fix(website): index prerendered HTML from Next's adapter route cache

[stipsan]

Description

The Vercel – react-rx deployment of the docs site fails on current since #694: next build succeeds, then pagefind --site .next/server/app reports Found 0 files matching **/*.{html} and exits 1 with "Pagefind was not able to build an index".

Root cause. #694 resolved next ^16.3.6 → 16.4.0 (the lockfile-only hold from #684 could not survive the next lockfile refresh). next@16.4.0 is the first stable release with vercel/next.js#99482 "Scope response cache keys to their source route": when a deployment adapter is configured, the export worker writes each prerendered page to .next/server/route-cache/APP_PAGE/<sha256(source route)>/$/<pathname>.html (useScopedBuildArtifacts in next/dist/export/worker.js) instead of .next/server/app/<pathname>.html. Vercel's @vercel/next builder sets NEXT_ADAPTER_PATH (adapter builds for next >= 16.2.0-canary.28), so on Vercel .next/server/app contains only the compiled route modules and no HTML. Local and CI builds have no adapter and still prerender to .next/server/app, which is why next build kept passing everywhere except the Vercel deployment. The layout is unchanged on Next canary, so this is the new permanent output for adapter builds, not a regression that will be reverted.

Fix. postbuild now runs website/scripts/pagefind.mts, which uses Pagefind's Node API to index .next/server/app plus every .next/server/route-cache/APP_PAGE/*/$ root that exists, then writes public/_pagefind as before. Pagefind derives URLs relative to each root, so the index content is identical to what the CLI produced before 16.4 (/, /guide.html, /examples/activity.html, … — Nextra strips .html). The script still fails the build when no HTML is found anywhere, and prints which roots it indexed so a future layout change is visible in the build log.

Why not pin next. Reverting to 16.3.6 only defers this to the next bump (the #684 hold lasted hours), holds back security patches, and the route-cache layout is where the Vercel adapter now reads prerendered output from. Pointing Pagefind at where the HTML actually lives is the durable fix; a single --site directory cannot express it because the root is hashed and differs between adapter and non-adapter builds, hence the small script.

The tsconfig.json change only adds **/*.mts to include so Oxlint's type-aware lint sees @types/node for the script. .mts is used so Node loads it as ESM without MODULE_TYPELESS_PACKAGE_JSON warnings, since website/package.json has no "type": "module".

What to review

• website/scripts/pagefind.mts — the root discovery (.next/server/app and route-cache/APP_PAGE/<hash>/$), error handling (createIndex/addDirectory/writeFiles errors, and the explicit "no prerendered HTML" failure), and the summary line. 41 lines, one no-console disable for the summary.
• website/package.json — postbuild runs the script with node (Node ≥ 22.18 strips types natively; the prebuild tsdown step already requires that on every build host).
• website/tsconfig.json — **/*.mts added to include.

Suggested merge: rebase (single commit).

Testing

No automated test for a build script; verified by running pnpm run build in website/ with next@16.4.0 from the current lockfile, in both layouts:

• Default (local/CI, no adapter): Pagefind indexed 24 from .next/server/app into public/_pagefind, exit 0, pagefind-entry.json reports page_count: 22.
• Adapter mode, reproducing Vercel with NEXT_ADAPTER_PATH=<no-op adapter>: before this change, pagefind --site .next/server/app → Found 0 files matching **/*.{html} → Pagefind was not able to build an index → exit 1 (the exact Vercel failure). After: Pagefind indexed 1 from …/APP_PAGE/1ac71f…/$, 1 from …/APP_PAGE/41da0e…/$, 22 from …/APP_PAGE/fbc75e…/$ into public/_pagefind, exit 0.
• Both layouts produce a byte-identical index (en_155874b525, 22 pages); the decoded fragments list /, /guide.html, /reference.html, /examples/*.html, /migrate/*.html with no route-cache prefix.
• Negative path: running the script against an empty .next/server/app exits 1 with Pagefind found no prerendered HTML in .next/server/app and writes nothing.
• pnpm lint, pnpm knip and oxfmt --check pass.
• On Vercel itself: this PR's Vercel – react-rx check passes ("Deployment has completed"), the preview serves /_pagefind/pagefind-entry.json with page_count: 22, and a Pagefind query for useObservable against the preview's index returns 20 results whose URLs (/reference, /guide, /examples/simple, /migrate/v4-to-v7, …) all respond HTTP 200.

  

[vercel]

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Project	Deployment	Actions	Updated
react-rx	Building	Preview	Oct 12, 2026 8:10pm UTC

1 Skipped Deployment

Project	Deployment	Actions	Updated
async-react	Skipped		Oct 12, 2026 8:10pm UTC

[Copilot]

🟢 Approval recommended

The implementation correctly handles both Next.js output layouts with appropriate failure reporting.

0 open findings

What changed in this PR

Updates website search indexing to support Next.js 16.4 adapter route-cache output while preserving local builds.

Changes:

• Adds Pagefind discovery and indexing across standard and adapter output roots.
• Runs the new script after website builds.
• Includes .mts scripts in TypeScript analysis.

File	Description
website/​scripts/​pagefind.mts	Discovers prerendered HTML roots and builds the Pagefind index.
website/​package.json	Uses the new postbuild script.
website/​tsconfig.json	Includes .mts files in type checking.

🧠 Review effort: Balanced

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