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feat(docs): serve Markdown to clients that ask for it - #12596

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feat(docs): serve Markdown to clients that ask for it#12596
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@jd jd commented Aug 28, 2026

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Every page already ships its Markdown source at <path>.md, which is what the
"View as Markdown" button and llms.txt link to. But the convention agents
reach for first is to request the page's own URL with Accept: text/markdown
(https://acceptmarkdown.com), and that returned HTML.

The site is a static build, so a Cloudflare Pages middleware is the only layer
that sees request headers. It rewrites to the .md twin when Markdown is asked
for, answers 404s in the format that was requested, and merges Accept into
Vary on both variants — without it a CDN would hand whichever variant it
cached first to everyone, which is the failure this is most likely to produce
in production and the least likely to be noticed. The Vary goes on 304
responses too, since those are exactly the ones a cache is about to act on.

Markdown is served only when text/markdown is named explicitly and not
outranked by text/html. Browsers send text/html,...,*/*;q=0.8, so honouring
wildcards would serve raw Markdown to every human visitor; the tests pin the
real Chrome and Firefox Accept headers against that.

HTML is served as the fallback only on a 404 from the .md route, not on
anything that is merely not ok: 304 Not Modified is the normal answer to a
client revalidating Markdown it already holds, and treating it as a missing
page answered it with HTML.

Three things about adding a root _middleware needed care, all three verified
against the real Pages runtime with wrangler pages dev dist:

Cloudflare documents that _redirects are not applied to requests served by
Functions, and this repository has 99 of them. next() does still route
through the asset server, so every redirect, the _headers rules, the .md
routes and the static 404 behave exactly as before.

next() is called with an explicit request everywhere. A bare next() is
documented as forwarding the original request, but once the middleware has
asked for the Markdown twin the runtime forwards that request again — so
/api and /cli, which are built from src/pages/ and have no .md, were
answered with the Markdown 404 instead of their own HTML. The test double
refuses a call with no request so this cannot come back.

A root middleware otherwise turns every request into a Worker invocation,
assets included — roughly thirty per page view, none of which can be
negotiated. _routes.json excludes the bundle, the search index, the
OpenGraph images and the static files by name, so only page requests reach the
Function.

Also ignore .wrangler/ — running the Pages runtime locally drops generated
bundles there, and eslint linted them.

Depends-On: #12595

@jd

jd commented Aug 28, 2026

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This pull request is part of a Mergify stack:

# Pull Request Link
1 fix(seo): restore the homepage OpenGraph image #12593
2 fix(a11y): stop docset grids skipping a heading level #12594
3 feat(docs): publish the API description where machines look for it #12595
4 feat(docs): serve Markdown to clients that ask for it #12596 👈
5 feat(docs): tell agents what Mergify is for in llms.txt #12597
6 feat(seo): describe the site with schema.org JSON-LD #12598
7 feat(docs): point a lost agent somewhere useful from the 404 #12599

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Merge Protections

🟢 All 7 merge protections satisfied — ready to merge.

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mergify Bot requested a review from a team August 28, 2026 13:31
Copilot AI lite review requested due to automatic review settings August 28, 2026 13:33
@jd
jd force-pushed the devs/jd/agentic-readiness/serve-markdown-clients-ask--52f9d2a1 branch from 1171c35 to 73f5d6b Compare August 28, 2026 13:33
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jd commented Aug 28, 2026

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Revision history

# Type Changes Reason Date
1 initial 1171c35 2026-08-28 13:33 UTC
2 content 1171c35 → 73f5d6b Scope the middleware with _routes.json: a root _middleware makes every request a Worker invocation, assets included (~30 per page view), none of which can be negotiated. Excludes the bundle, search i… 2026-08-28 13:33 UTC
3 content 73f5d6b → 80ec774 Fix the 304 fallback copilot found on #12596, plus a next(request) bug it surfaced; add middleware tests 2026-08-28 14:37 UTC
4 rebase 80ec774 → ecb955f (rebase only) 2026-08-28 15:09 UTC

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Pull request overview

Adds Cloudflare Pages middleware-based content negotiation so clients explicitly requesting text/markdown receive the existing per-page *.md “twin”, while keeping CDN caching correct via Vary: Accept and avoiding Worker invocations for most static assets.

Changes:

  • Introduces prefersMarkdown() + isNegotiablePage() utilities (with Vitest coverage) to drive safe Accept-header negotiation.
  • Adds Pages middleware to rewrite negotiable page requests to their *.md twin, return Markdown-formatted 404s when appropriate, and merge Accept into Vary for negotiated media types.
  • Adds <link rel="alternate" type="text/markdown"> in page head, and introduces _routes.json plus lint/format ignores for local Wrangler artifacts.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file
File Description
src/util/acceptMarkdown.ts Implements Accept parsing + policy for when to serve Markdown.
src/util/acceptMarkdown.test.ts Unit tests covering key negotiation scenarios and asset/page detection.
src/components/HeadSEO.astro Publishes the Markdown twin via an alternate link tag.
public/_routes.json Limits Pages Function routing to page requests by excluding major static asset paths.
functions/_middleware.ts Rewrites requests to *.md when appropriate and sets Vary: Accept on negotiated responses.
eslint.config.js Ignores local .wrangler/ artifacts for linting.
biome.json Excludes .wrangler/ from Biome formatting/linting.
.gitignore Ignores local Wrangler build artifacts.

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Comment thread functions/_middleware.ts
@jd
jd marked this pull request as ready for review August 28, 2026 14:08
@jd
jd force-pushed the devs/jd/agentic-readiness/serve-markdown-clients-ask--52f9d2a1 branch from 73f5d6b to 80ec774 Compare August 28, 2026 14:37
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mergify Bot had a problem deploying to Mergify Merge Protections August 28, 2026 14:37 Failure
jd added 4 commits August 28, 2026 17:08
`getOgImageUrl` strips the leading and trailing slashes off the pathname to
build the image filename. For the homepage that pathname is `/`, so stripping
left an empty string and the lookup missed — every docs page had an OpenGraph
image and the homepage shipped `<meta property="og:image">` with no content.

The homepage's collection id is `index`, which is what `getStaticPaths` names
its image, so fall back to that when the slug comes out empty.

Covered by a regression test that fails against the old expression. The
generated-image set comes from the content collection and needs the Astro build
pipeline, so the test stubs it and exercises the derivation, which is the half
that was wrong.

Change-Id: Ifb9a23ea2caa20d28489a4f21363d85ed5e3342c
Docset cards rendered their title as `h4`. Almost every grid sits directly
under an `##`, so the outline jumped h2 to h4 — including on the homepage,
whose whole body is the "Products" grid. Screen readers and anything parsing
the document outline read that as a missing level.

Default the card heading to `h3` and make it a prop, because one grid does
belong at h4: the "Components" grid in `ci-insights.mdx` is nested under an
`### Components`, where h3 would make the cards siblings of their own section
heading instead of children.

Change-Id: Ie01f4c2b03f1f2b7f798ae89b056135a5b00800e
The Mergify OpenAPI 3.1 document is already deployed — it is what the API
Reference pages are generated from — but only at `/api-schemas.json`, a
filename that exists nowhere outside this repository. Every OpenAPI client,
SDK generator and crawler probes `/openapi.json`, so nothing finds it and the
docs read as a site with no API at all.

Serve the same bytes at `/openapi.json`. The route does not transform the
document: the spec is synced from the engine repository, and two spellings of
it that could disagree would be worse than one obscure path.

Alongside it, three other entry points that were undiscoverable:

- `<link rel="service-desc">` in every page head, the IANA relation for "the
  description of this site's API" (RFC 8631), plus one for `llms.txt`.
- `robots.txt` had no `Sitemap:` line, so crawlers had to guess
  `sitemap-index.xml` rather than be told.
- `/developers` is the path people and tools guess for a developer portal and
  was a 404; it now redirects to the API reference.

Change-Id: I1b625f960363c8427d5282c052fee74111bf07fa
Every page already ships its Markdown source at `<path>.md`, which is what the
"View as Markdown" button and `llms.txt` link to. But the convention agents
reach for first is to request the page's own URL with `Accept: text/markdown`
(https://acceptmarkdown.com), and that returned HTML.

The site is a static build, so a Cloudflare Pages middleware is the only layer
that sees request headers. It rewrites to the `.md` twin when Markdown is asked
for, answers 404s in the format that was requested, and merges `Accept` into
`Vary` on both variants — without it a CDN would hand whichever variant it
cached first to everyone, which is the failure this is most likely to produce
in production and the least likely to be noticed. The `Vary` goes on `304`
responses too, since those are exactly the ones a cache is about to act on.

Markdown is served only when `text/markdown` is named explicitly and not
outranked by `text/html`. Browsers send `text/html,...,*/*;q=0.8`, so honouring
wildcards would serve raw Markdown to every human visitor; the tests pin the
real Chrome and Firefox Accept headers against that.

HTML is served as the fallback only on a `404` from the `.md` route, not on
anything that is merely not `ok`: `304 Not Modified` is the normal answer to a
client revalidating Markdown it already holds, and treating it as a missing
page answered it with HTML.

Three things about adding a root `_middleware` needed care, all three verified
against the real Pages runtime with `wrangler pages dev dist`:

Cloudflare documents that `_redirects` are not applied to requests served by
Functions, and this repository has 99 of them. `next()` does still route
through the asset server, so every redirect, the `_headers` rules, the `.md`
routes and the static 404 behave exactly as before.

`next()` is called with an explicit request everywhere. A bare `next()` is
documented as forwarding the original request, but once the middleware has
asked for the Markdown twin the runtime forwards *that* request again — so
`/api` and `/cli`, which are built from `src/pages/` and have no `.md`, were
answered with the Markdown 404 instead of their own HTML. The test double
refuses a call with no request so this cannot come back.

A root middleware otherwise turns every request into a Worker invocation,
assets included — roughly thirty per page view, none of which can be
negotiated. `_routes.json` excludes the bundle, the search index, the
OpenGraph images and the static files by name, so only page requests reach the
Function.

Also ignore `.wrangler/` — running the Pages runtime locally drops generated
bundles there, and eslint linted them.

Change-Id: I52f9d2a1c70248b1406412129a633cc3bee219de
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Base automatically changed from devs/jd/agentic-readiness/publish-api-desc-machines-look--1b625f96 to main September 4, 2026 13:10
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mergify Bot requested a review from a team September 5, 2026 21:40
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mergify Bot commented Sep 7, 2026

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mergify Bot merged commit 80a2587 into main Sep 7, 2026
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mergify Bot deleted the devs/jd/agentic-readiness/serve-markdown-clients-ask--52f9d2a1 branch September 7, 2026 13:51
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4 participants