Tracking: vinext dev is unusable for this app — every route 404s (workerd/no-fs) or 500s (dev module-runner can't CJS-interop the per-request MDX compile chain)

[hyf0]

Tracking issue for vinext dev being unusable on this app (reactjs/react.dev, Pages Router). vinext build && vinext start works perfectly; only the dev server is broken. There are two stacked failure modes depending on whether @cloudflare/vite-plugin is active. Related: #6 (a narrow slice of the CJS issue below), #14 (the cloudflare-in-dev half), #15 (why the compile chain runs per-request at all).

Symptom A — with cloudflare() in vite.config (the config vinext deploy requires): every route 404s

vinext deploy requires cloudflare() in a custom vite.config, and it runs unconditionally, so it's active in dev too. @cloudflare/vite-plugin runs the app in workerd, which has no fs. This app's catch-all getStaticProps reads content from disk (see #15), so every page throws and the dev server returns:

GET /                    -> 404   (content-length: 0, no error in the log)
GET /learn               -> 404
GET /learn/installation  -> 404
GET /api/md              -> 404
GET /robots.txt          -> 200   (static assets still serve)
GET /favicon.ico         -> 200

A bare 404 with an empty body and no log line makes this very hard to trace — it looks like routing is half-broken rather than "the page handler threw in workerd".

Symptom B — with cloudflare() gated off (dev runs in Node): cascading CJS-interop crashes

Because vinext doesn't prerender in dev (#15), every request runs the full build-time MDX compile chain (remark/retext/babel + metro-cache). vinext's dev SSR module-runner inlines those (old, CJS) packages without CJS interop, so each one throws require/exports/module is not defined. They surface one at a time; each can be silenced by adding it to optimizeDeps.include (+ ssr.optimizeDeps.include), which just reveals the next:

node_modules/parse-numeric-range/index.js   ReferenceError: exports is not defined   (fatal — dev server exits)
node_modules/tailwindcss/defaultTheme.js    ReferenceError: require is not defined    (fatal)
node_modules/debounce/index.js              ReferenceError: module is not defined     (now per-request 500)
node_modules/metro-cache/src/index.js       ReferenceError: require is not defined
node_modules/remark/index.js                ReferenceError: require is not defined
… still ahead: remark-external-links, remark-images, remark-unwrap-images,
   remark-html, retext, retext-smartypants, mdast-util-to-string, unist-util-visit, …

Getting dev to boot this way needs an ~18-entry optimizeDeps.include list that is fragile (breaks whenever any of those transitive packages changes), and dev would still recompile all MDX on every request (slow). Note the first two crashes are fatal (the dev server process exits), not per-request errors.

Root cause

1. cloudflare() can't be scoped to the deploy build, so dev inherits workerd (no fs) → vinext deploy with a custom vite.config fails on missing cloudflare() (and the local-vs-deploy wrangler.jsonc story) #14.
2. vinext dev executes getStaticProps per request instead of prerendering (Pages Router: getStaticProps runs per-request instead of prerendering → fs-backed SSG apps 500 on Cloudflare Workers (needs --prerender-all) #15), dragging the entire build-time compile chain onto the request path, where the dev module-runner can't CJS-interop it (vinext dev SSR module-runner doesn't CJS-interop UMD/CJS deps (classnames window, parse-numeric-range exports) #6 is the first two entries of the list above).

What works today

vinext build --prerender-all && vinext start — all routes 200, real content, no per-request compilation. So the recommended local workflow is vinext start, and this issue tracks making vinext dev actually usable.

Suggestions

• Don't run cloudflare() in dev (or give configs a reliable deploy-only signal — see vinext deploy with a custom vite.config fails on missing cloudflare() (and the local-vs-deploy wrangler.jsonc story) #14) so dev runs in Node where fs works.
• Make the dev SSR module-runner apply the same CJS interop the production build already does (the build bundles all of these packages fine), so an app doesn't need to hand-enumerate every transitive CJS dep in optimizeDeps.include.
• Optionally prerender/cache getStaticProps in dev too (Pages Router: getStaticProps runs per-request instead of prerendering → fs-backed SSG apps 500 on Cloudflare Workers (needs --prerender-all) #15) so the heavy compile chain isn't on the request path.

Related upstream (cloudflare/vinext)

• SSR dev server fails with "module is not defined" for CJS dependencies (void-elements, highlight.js, etc.) cloudflare/vinext#585 — SSR dev server fails with "module is not defined" for CJS deps (Symptom B root cause; OPEN)
• fix: support CommonJS node_modules in Pages Router dev cloudflare/vinext#665 — fix: support CommonJS node_modules in Pages Router dev (a written-but-stalled fix; OPEN, changes requested)
• Pages Router: _next/data JSON endpoint not implemented cloudflare/vinext#1330 — Pages Router _next/data JSON endpoint not implemented (OPEN/reopened)
• Static pre-rendering at build time cloudflare/vinext#9 / Populating remote cache during deployment cloudflare/vinext#562 — getStaticProps not prerendered / remote cache (why the compile chain runs per-request)

Environment

vinext 0.1.8, Vite 8.1, Node 24, Pages Router, macOS.