Fix duplicate `/api` route handling by jeffsee55 · Pull Request #15297 · vercel/vercel

jeffsee55 · 2026-02-27T01:08:59Z

Fix dynamic routes with [id] segments returning 404 on Vercel . When Next.js is the frontend, do not add the catch-all ^/api(/.*)?$ → 404 rewrite, so App Router API routes like /api/blog/posts/[id] are handled by Next.js instead of being 404'd by zero-config routes.

Can be reproduced by deploying this repo and visiting /api/flow/hello/next, which incorrectly 404s.

Warning

High Risk Change

Changes routing logic in detect-builders.ts to skip adding catch-all 404 rewrite for /api routes when Next.js is the frontend, which alters request handling behavior in production deployments.

Routing: conditionally skips catch-all /api 404 rewrite when Next.js detected
Infrastructure: affects how Vercel routes API requests in production
Tests added to verify behavior for both Next.js and non-Next.js frontends

^{Risk assessment for commit a18f5c3.}

…2). When Next.js is the frontend, do not add the catch-all `^/api(/.*)?$` → 404 rewrite, so App Router API routes like `/api/blog/posts/[id]` are handled by Next.js instead of being 404'd by zero-config routes.

changeset-bot · 2026-02-27T01:09:10Z

🦋 Changeset detected

Latest commit: a18f5c3

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@vercel/fs-detectors	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

github-actions · 2026-02-27T01:09:16Z

📦 CLI Tarball Ready

The Vercel CLI tarball for this PR is now available!

Quick Test

You can test this PR's CLI directly by running:

npx https://vercel-2qo53qp1p.vercel.sh/tarballs/vercel.tgz --help

Use in vercel.json

To use this CLI version in your project builds, add to your vercel.json:

{
  "build": {
    "env": {
      "VERCEL_CLI_VERSION": "vercel@https://vercel-2qo53qp1p.vercel.sh/tarballs/vercel.tgz"
    }
  }
}

Python Runtime Wheel

A vercel-runtime wheel was also built for this PR.
To use in your Python project builds, also set this environment variable:

VERCEL_RUNTIME_PYTHON="vercel-runtime @ https://vercel-2qo53qp1p.vercel.sh/tarballs/vercel_runtime-0.6.0.dev1772252471+a18f5c3-py3-none-any.whl"

Python Workers Wheel

A vercel-workers wheel was also built for this PR.
To use in your Python project builds, also set this environment variable:

VERCEL_WORKERS_PYTHON="vercel-workers @ https://vercel-2qo53qp1p.vercel.sh/tarballs/vercel_workers-0.1.0.dev1772252471+a18f5c3-py3-none-any.whl"

github-actions · 2026-02-27T01:10:32Z

🧪 Unit Test Strategy

Comparing: 0c4ebf1 → a18f5c3 (view diff)

Strategy: Affected packages only

✅ Only testing packages that have been modified or depend on modified packages.

Affected packages - 3 (8%)

@vercel/fs-detectors
@vercel/static-build
vercel

Unaffected packages - 37 (93%)

@vercel-internals/get-package-json
@vercel/backends
@vercel/build-utils
@vercel/cervel
@vercel/cli-auth
@vercel/client
@vercel/config
@vercel/detect-agent
@vercel/edge
@vercel/elysia
@vercel/error-utils
@vercel/express
@vercel/fastify
@vercel/firewall
@vercel/frameworks
@vercel/functions
@vercel/gatsby-plugin-vercel-builder
@vercel/go
@vercel/h3
@vercel/hono
@vercel/hydrogen
@vercel/koa
@vercel/nestjs
@vercel/next
@vercel/node
@vercel/oidc
@vercel/oidc-aws-credentials-provider
@vercel/python
@vercel/python-analysis
@vercel/redwood
@vercel/related-projects
@vercel/remix-builder
@vercel/routing-utils
@vercel/ruby
@vercel/rust
@vercel/static-config
examples

Results

Unit tests: Only affected packages will run unit tests
E2E tests: Running in parallel via E2E Tests workflow
Type checks: Only affected packages will run type checks

This comment is automatically generated based on the affected testing strategy

Removed filter for experimental fixture '06-services-multi-frontend-multi-runtime'.

…nts-return-404-on-vercel-despite

This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## @vercel/backends@0.0.40 ### Patch Changes - Updated dependencies \[[`9721f4948a72d273f792c54f5393aa50ac279209`](9721f49)]: - @vercel/build-utils@13.6.2 ## @vercel/build-utils@13.6.2 ### Patch Changes - add partialFallback flag to prerender output ([#14703](#14703)) ## @vercel/cervel@0.0.27 ### Patch Changes - Updated dependencies \[]: - @vercel/backends@0.0.40 ## vercel@50.25.6 ### Patch Changes - Updated dependencies \[[`9721f4948a72d273f792c54f5393aa50ac279209`](9721f49)]: - @vercel/build-utils@13.6.2 - @vercel/next@4.15.37 - @vercel/backends@0.0.40 - @vercel/elysia@0.1.43 - @vercel/express@0.1.52 - @vercel/fastify@0.1.46 - @vercel/go@3.4.3 - @vercel/h3@0.1.52 - @vercel/hono@0.2.46 - @vercel/hydrogen@1.3.5 - @vercel/koa@0.1.26 - @vercel/nestjs@0.2.47 - @vercel/node@5.6.10 - @vercel/python@6.19.0 - @vercel/redwood@2.4.9 - @vercel/remix-builder@5.6.0 - @vercel/ruby@2.3.2 - @vercel/rust@1.0.5 - @vercel/static-build@2.8.44 ## @vercel/client@17.2.51 ### Patch Changes - Updated dependencies \[[`9721f4948a72d273f792c54f5393aa50ac279209`](9721f49)]: - @vercel/build-utils@13.6.2 ## @vercel/elysia@0.1.43 ### Patch Changes - Updated dependencies \[]: - @vercel/node@5.6.10 ## @vercel/express@0.1.52 ### Patch Changes - Updated dependencies \[]: - @vercel/node@5.6.10 - @vercel/cervel@0.0.27 ## @vercel/fastify@0.1.46 ### Patch Changes - Updated dependencies \[]: - @vercel/node@5.6.10 ## @vercel/fs-detectors@5.8.15 ### Patch Changes - Fix App Router dynamic API routes returning 404 in production. When a project has both Next.js (App Router) and a root `api/` folder, zero-config added a catch-all `^/api(/.*)?# @vercel/fs-detectors → 404 in the filesystem phase, which runs before the rewrite phase where Next.js routes live. So requests like `/api/flow/hello/next`or`/api/blog/posts/5`matched the catch-all and never reached the Next.js route. When Next.js is the frontend we no longer add that rewrite so those routes are handled by Next.js. (Locally, only`next dev`worked;`vc dev\` had the same 404.) ([#15297](#15297)) ## @vercel/gatsby-plugin-vercel-builder@2.0.142 ### Patch Changes - Updated dependencies \[[`9721f4948a72d273f792c54f5393aa50ac279209`](9721f49)]: - @vercel/build-utils@13.6.2 ## @vercel/h3@0.1.52 ### Patch Changes - Updated dependencies \[]: - @vercel/node@5.6.10 ## @vercel/hono@0.2.46 ### Patch Changes - Updated dependencies \[]: - @vercel/node@5.6.10 ## @vercel/koa@0.1.26 ### Patch Changes - Updated dependencies \[]: - @vercel/node@5.6.10 ## @vercel/nestjs@0.2.47 ### Patch Changes - Updated dependencies \[]: - @vercel/node@5.6.10 ## @vercel/next@4.15.37 ### Patch Changes - add partialFallback flag to prerender output ([#14703](#14703)) ## @vercel/node@5.6.10 ### Patch Changes - Updated dependencies \[[`9721f4948a72d273f792c54f5393aa50ac279209`](9721f49)]: - @vercel/build-utils@13.6.2 ## @vercel/static-build@2.8.44 ### Patch Changes - Updated dependencies \[]: - @vercel/gatsby-plugin-vercel-builder@2.0.142  > [!NOTE] > Low Risk Change > > This PR is an automated Changesets release that only bumps version numbers in package.json files and updates CHANGELOG.md files across multiple packages, with no code logic changes. > > - Version bumps in package.json files (patch versions) > - CHANGELOG.md updates documenting dependency updates > - Deleted changeset markdown files consumed by release process > > <sup>Risk assessment for [commit 00d9965](https://github.com/vercel/vercel/commit/00d9965d12c097c2375af4e717f17594ca2ed06c).</sup>  Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Check against accumulated stderr on test

aa3f1f4

vercel bot deployed to Preview February 27, 2026 20:29 View deployment

Remove useless test

3b5d8f1

vercel bot deployed to Preview February 27, 2026 23:21 View deployment

jeffsee55 marked this pull request as ready for review February 27, 2026 23:23

jeffsee55 requested review from a team and agadzik as code owners February 27, 2026 23:23

jeffsee55 requested a review from ijjk February 27, 2026 23:25

ijjk approved these changes Feb 27, 2026

View reviewed changes

Move test

2f15137

vercel bot deployed to Preview February 28, 2026 00:07 View deployment

Disable test

84e2e37

vercel bot deployed to Preview February 28, 2026 00:18 View deployment

jeffsee55 added 2 commits February 27, 2026 20:21

Remove filter for experimental fixture in tests

995df39

Removed filter for experimental fixture '06-services-multi-frontend-multi-runtime'.

Merge branch 'main' into jeffsee/cli-152-dynamic-routes-with-id-segme…

a18f5c3

…nts-return-404-on-vercel-despite

vercel bot deployed to Preview February 28, 2026 04:22 View deployment

mehulkar approved these changes Mar 2, 2026

View reviewed changes

ricardo-agz approved these changes Mar 2, 2026

View reviewed changes

jeffsee55 merged commit f1e8c97 into main Mar 2, 2026
270 of 274 checks passed

jeffsee55 deleted the jeffsee/cli-152-dynamic-routes-with-id-segments-return-404-on-vercel-despite branch March 2, 2026 18:35

vercel-release-bot mentioned this pull request Mar 2, 2026

Version Packages #15343

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Fix duplicate `/api` route handling#15297

Fix duplicate `/api` route handling#15297
jeffsee55 merged 7 commits intomainfrom
jeffsee/cli-152-dynamic-routes-with-id-segments-return-404-on-vercel-despite

jeffsee55 commented Feb 27, 2026 •

edited by vercel bot

Loading

Uh oh!

changeset-bot bot commented Feb 27, 2026 •

edited

Loading

Uh oh!

github-actions bot commented Feb 27, 2026 •

edited

Loading

Uh oh!

github-actions bot commented Feb 27, 2026 •

edited

Loading

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Conversation

jeffsee55 commented Feb 27, 2026 • edited by vercel bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

changeset-bot bot commented Feb 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

🦋 Changeset detected

Uh oh!

github-actions bot commented Feb 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

📦 CLI Tarball Ready

Quick Test

Use in vercel.json

Python Runtime Wheel

Python Workers Wheel

Uh oh!

github-actions bot commented Feb 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

🧪 Unit Test Strategy

Results

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

jeffsee55 commented Feb 27, 2026 •

edited by vercel bot

Loading

changeset-bot bot commented Feb 27, 2026 •

edited

Loading

github-actions bot commented Feb 27, 2026 •

edited

Loading

github-actions bot commented Feb 27, 2026 •

edited

Loading