fix: generate conversation titles with session model (cherry-pick #3898 to develop)

[JasonW404]

Summary

Cherry-pick of #3898 (merged into hotfix/v2.5.1) onto develop. The fix was never propagated to develop, so title generation on develop still ignores the session-selected model.

• pass the send-time session model_id from the chat UI to conversation title generation
• resolve and validate the selected tenant-scoped LLM for both regular and Northbound title APIs
• preserve the existing tenant-default LLM fallback when model_id is omitted
• log successful title generation as title_generation: <model> -> <title>

Behavior

Explicit model selections must exist in the current tenant, be active, and have type llm. Invalid, deleted, cross-tenant, or non-LLM selections return HTTP 422 without generating or persisting a title. The frontend snapshots the model ID used for the Agent run (modelIdForRun), so a later selector change cannot alter the title model.

Provenance

• Source PR: fix: generate conversation titles with session model #3898 — fix: generate conversation titles with session model (merged to hotfix/v2.5.1)
• Cherry-picked commit: 68b99763e76ada0164aa6436e65d6bd47e34dfa7 (squash merge, single parent)
• Base: origin/develop @ 96599711f24a0cc7f83c8d143e4ac5ce747cda61
• Applied with git cherry-pick -x; no conflicts, 8 files auto-merged cleanly
• Resulting commit: 899a40f2a — 14 files changed, +249 / -20 (identical to fix: generate conversation titles with session model #3898)

Verification

Port fidelity — the change set is byte-identical to #3898:

• git range-diff reports the commit as equivalent; the only delta is the added (cherry picked from commit ...) trailer
• Extracted added/removed payload lines from both patches: 269 vs 269, diff empty

Backend focused suites, baseline origin/develop vs this branch (all green, no regressions):

test file	baseline	branch	Δ
test/backend/test_model_consts.py	79	81	+2
test/backend/app/test_conversation_management_app.py	29	30	+1
test/backend/app/test_northbound_app.py	105	106	+1
test/backend/services/test_conversation_management_service.py	93	98	+5
test/backend/services/test_northbound_service.py	114	114	0
total	420	429	+9

The +9 matches exactly the test cases added by #3898, and the new except ValidationError handlers are covered by test_generate_title_validation_error in both app test files.

Frontend:

• node --test tests/conversationTitle.test.ts: 2 passed
• tsc --noEmit: error set identical to baseline (234 pre-existing errors, all from unrelated components/ui/* and e2e/* files); zero errors in chatInterface.tsx, conversationTitle.ts, or conversationService.ts

Symbol resolution after auto-merge (guards against silent drift on develop):

• ValidationError resolves to consts.exceptions.ValidationError in both apps/northbound_app.py and apps/conversation_management_app.py
• Field resolves in consts/model.py; logger, Optional, and get_model_by_model_id all resolve in services/conversation_management_service.py

Runtime/E2E validation (ARM64 Docker build, Multipass Docker E2E, tenant-admin E2E, observed title_generation log) was performed in #3898 and is not repeated here; this is a faithful port of that already-reviewed change.

Notes

Pre-existing, unrelated to this PR: running the five backend test files together in a single pytest invocation fails collection with AttributeError: module 'consts.model' has no attribute 'ManageTenantModelCreateRequest'. This reproduces identically on clean origin/develop and is caused by test/conftest.py exposing both backend.consts.model and consts.model as distinct module objects. Running each file individually passes. Not addressed here.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!