nextjs - ✅(Solved) Fix compound pageExtensions with node-runtime proxy can emit server/middleware.js but skip standalone copy [1 pull requests, 2 comments, 2 participants]

nextjs2026-03-18 17:51:49

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vercel/next.js#91600•Fetched 2026-04-08 00:57:50

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Author

relsunkaev

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omriattiya-il

relsunkaev

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Root Cause

proxy.api.js is accepted as the root proxy file because it matches the proxy detection regex built from pageExtensions.
With runtime = "nodejs", the build emits .next/server/middleware.js and .next/server/middleware.js.nft.json.
functions-config-manifest.json remains empty.
middleware-manifest.json remains empty.
.next/standalone/.../.next/server/middleware.js is missing.

Fix Action

Fixed

Fixed by PR: fix(build): use basename regexp to detect proxy/middleware with compound pageExtensions (https://github.com/vercel/next.js/pull/91736)

PR fix notes

PR #91736: fix(build): use basename regexp to detect proxy/middleware with compound pageExtensions

Repository: vercel/next.js
Author: sleitor
State: open | merged: False
Link: https://github.com/vercel/next.js/pull/91736

Description (problem / solution / changelog)

What?

Fix proxy/middleware detection in the production build and dev watcher when compound are used (e.g. ).

Why?

When a root proxy file is named proxy.api.js, path.parse().name returns 'proxy.api' (the full stem up to the final extension). The subsequent equality check fileBaseName === PROXY_FILENAME (where PROXY_FILENAME = 'proxy') never matches, so proxyFilePath is never set.

Consequence:

functions-config-manifest.json is not written with /_middleware
middleware.js is not copied into the standalone output
Downstream tooling that expects the node middleware artifact in standalone breaks

The same bug existed in both the production build path (packages/next/src/build/index.ts) and the dev watcher (server/lib/router-utils/setup-dev-bundler.ts).

How?

Both files already build detection regexps from pageExtensions (e.g. ^proxy\.(?:api\.js|page\.tsx)$). Replace the plain fileBaseName === PROXY_FILENAME equality checks with detectionRegExp.test(path.basename(filePath)). This correctly matches proxy.api.js regardless of how many extension segments are present.

Fixes #91600

Changed files

packages/next/src/build/index.ts (modified, +14/-4)
packages/next/src/server/lib/router-utils/setup-dev-bundler.ts (modified, +20/-3)

Code Example

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 25.3.0: Wed Jan 28 20:48:41 PST 2026; root:xnu-12377.81.4~5/RELEASE_ARM64_T6041
  Available memory (MB): 49152
  Available CPU cores: 14
Binaries:
  Node: 22.21.1
  npm: 10.9.4
  Yarn: N/A
  pnpm: 10.13.1
Relevant Packages:
  next: 16.2.0-canary.104
  eslint-config-next: N/A
  react: 19.2.4
  react-dom: 19.2.4
  typescript: N/A
Next.js Config:
  output: standalone

RAW_BUFFERClick to expand / collapse

Link to the code that reproduces this issue

https://github.com/relsunkaev/next-proxy-pageextensions-repro

To Reproduce

Clone the repro.
Run pnpm install.
Keep export const runtime = "nodejs" in proxy.api.js.
Run NODE_ENV=production CI=1 pnpm build.
Inspect these files:
- .next/server/middleware.js
- .next/server/middleware.js.nft.json
- .next/server/functions-config-manifest.json
- .next/standalone/**/.next/server/middleware.js
Observe that the build emits server/middleware.js, but does not write /_middleware into functions-config-manifest.json and does not copy middleware.js into standalone output.

Current vs. Expected behavior

Current behavior:

proxy.api.js is accepted as the root proxy file because it matches the proxy detection regex built from pageExtensions.
With runtime = "nodejs", the build emits .next/server/middleware.js and .next/server/middleware.js.nft.json.
functions-config-manifest.json remains empty.
middleware-manifest.json remains empty.
.next/standalone/.../.next/server/middleware.js is missing.

Expected behavior:

If proxy.api.js is accepted as a valid root proxy file, Next should classify it as middleware consistently.
In the node runtime case, functions-config-manifest.json should contain /_middleware.
middleware.js should be copied into standalone output.

Why this seems to happen:

Detection regex is built from pageExtensions, so proxy.api.js matches.
Later classification uses path.parse(rootPath).name === "proxy".
For proxy.api.js, path.parse(...).name is "proxy.api", so proxyFilePath is never set.
That leaves hasNodeMiddleware false, so standalone copy never runs.

Important scope note:

I could not reproduce the same failure without runtime = "nodejs".
Without that export, the same repro is classified as edge middleware instead, and the missing server/middleware.js standalone artifact is no longer the relevant failure mode.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 25.3.0: Wed Jan 28 20:48:41 PST 2026; root:xnu-12377.81.4~5/RELEASE_ARM64_T6041
  Available memory (MB): 49152
  Available CPU cores: 14
Binaries:
  Node: 22.21.1
  npm: 10.9.4
  Yarn: N/A
  pnpm: 10.13.1
Relevant Packages:
  next: 16.2.0-canary.104
  eslint-config-next: N/A
  react: 19.2.4
  react-dom: 19.2.4
  typescript: N/A
Next.js Config:
  output: standalone

Which area(s) are affected? (Select all that apply)

Middleware
Output
Pages Router
Turbopack

Which stage(s) are affected? (Select all that apply)

next build (local)
Other (Deployed)

Additional context

This came from a real app using compound page extensions:

pageExtensions: ["page.tsx", "api.ts"]
root proxy file named proxy.api.ts
export const runtime = "nodejs"

In that app, Next emits .next/server/middleware.js, but standalone output is missing middleware.js, which then breaks downstream tooling that expects standalone to contain the node middleware artifact.

I verified the repro on the latest canary (16.2.0-canary.104).

extent analysis

Fix Plan

To resolve the issue, we need to modify the next.config.js file to correctly handle the proxy.api.js file as a middleware file.

Here are the steps:

Update the next.config.js file to include a custom middleware function that checks for the proxy.api.js file.
Modify the pageExtensions to include the .api.js extension.

Code Changes

// next.config.js
module.exports = {
  // ... other configurations ...
  experimental: {
    // ... other experimental configurations ...
    middleware: [(req, res, next) => {
      if (req.url === '/_middleware') {
        // Handle the middleware request
      }
      next();
    }],
  },
  pageExtensions: ['page.tsx', 'api.ts', 'api.js'], // Add .api.js extension
};

Verification

To verify the fix, run the following commands:

pnpm build
Check the generated files in the .next directory to ensure that middleware.js is present in the standalone output.
Verify that the functions-config-manifest.json file contains the /_middleware entry.

Extra Tips

Make sure to update the next version to the latest canary version (16.2.0-canary.104 or later) to ensure that the fix is applied.
If you are using a custom middleware function, ensure that it is correctly handling the proxy.api.js file.

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nextjs - ✅(Solved) Fix compound pageExtensions with node-runtime proxy can emit server/middleware.js but skip standalone copy [1 pull requests, 2 comments, 2 participants]

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Root Cause

Fix Action

Fixed

PR fix notes

PR #91736: fix(build): use basename regexp to detect proxy/middleware with compound pageExtensions

Description (problem / solution / changelog)

What?

Why?

How?

Changed files

Code Example

Link to the code that reproduces this issue

To Reproduce

Current vs. Expected behavior

Provide environment information

Which area(s) are affected? (Select all that apply)

Which stage(s) are affected? (Select all that apply)

Additional context

extent analysis

Fix Plan

Code Changes

Verification

Extra Tips

Still need to ship something?

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nextjs - ✅(Solved) Fix compound pageExtensions with node-runtime proxy can emit server/middleware.js but skip standalone copy [1 pull requests, 2 comments, 2 participants]

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GitHub issue graph ai analysis

Root Cause

Fix Action

Fixed

PR fix notes

PR #91736: fix(build): use basename regexp to detect proxy/middleware with compound pageExtensions

Description (problem / solution / changelog)

What?

Why?

How?

Changed files

Code Example

Link to the code that reproduces this issue

To Reproduce

Current vs. Expected behavior

Provide environment information

Which area(s) are affected? (Select all that apply)

Which stage(s) are affected? (Select all that apply)

Additional context

extent analysis

Fix Plan

Code Changes

Verification

Extra Tips

Still need to ship something?

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TRENDING