Support per function regions from vercel.json by ctgowrie · Pull Request #15149 · vercel/vercel

ctgowrie · 2026-02-19T18:38:46Z

Update next builder to allow per function regions from vercel.json

Enables vercel.json below to be mapped into build output API lambdas

  "regions": ["fra1"],
  "functions": {
    "src/app/api/v3/**/cle1/route.ts": {
      "regions": ["cle1"],
      "functionFailoverRegions": ["pdx1"]
    },
    "src/app/api/v3/**/iad1/route.ts": {
      "regions": ["iad1"],
      "functionFailoverRegions": ["pdx1"]
    }
  },

Note

Low Risk Change

This PR adds support for passing through regions and functionFailoverRegions configuration from vercel.json to lambda build output, a straightforward feature addition with no security implications.

Adds regions and functionFailoverRegions properties to LambdaGroup type
Passes region config through to lambda build output in server-build.ts
Adds helper function regionsArrayEqual for comparing region arrays in grouping logic

^{Risk assessment for commit 2c3a826.}

changeset-bot · 2026-02-19T18:38:56Z

🦋 Changeset detected

Latest commit: 2c3a826

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

This PR includes changesets to release 2 packages

Name	Type
@vercel/next	Patch
vercel	Patch

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

github-actions · 2026-02-19T18:39:00Z

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{
  "build": {
    "env": {
      "VERCEL_CLI_VERSION": "vercel@https://vercel-6qihyw349.vercel.sh/tarballs/vercel.tgz"
    }
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github-actions · 2026-02-19T18:40:20Z

🧪 Unit Test Strategy

Comparing: 95d8614 → 2c3a826 (view diff)

Strategy: Affected packages only

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

Affected packages - 2 (5%)

@vercel/next
vercel

Unaffected packages - 38 (95%)

@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/fs-detectors
@vercel/functions
@vercel/gatsby-plugin-vercel-builder
@vercel/go
@vercel/h3
@vercel/hono
@vercel/hydrogen
@vercel/koa
@vercel/nestjs
@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-build
@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

packages/next/src/utils.ts

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 publish to npm yourself or [setup this action to publish automatically](https://github.com/changesets/action#with-publishing). 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@50.21.0 ### Minor Changes - Add `--all` flag to `vercel ls` command and improve behavior when not linked to a project ([#15143](#15143)) - `vercel ls` no longer requires a linked project. When not linked, it now lists all deployments across all projects in the current scope - Added `--all` flag to explicitly list deployments across all projects, even when linked to a specific project - Added "Project" column to the deployment table output to show which project each deployment belongs to - JSON output (`--format json`) is unchanged and continues to include the `name` field for project name ### Patch Changes - fix(cli): Handle SIGINT during upgrade prompt without showing a stacktrace ([#15105](#15105)) - Use formatted tables for `metrics schema` output, matching the convention used by other list commands ([#15138](#15138)) - Updated dependencies \[[`5d1f55af04d0fdba7e7ac86f9eeda44316f54f5b`](5d1f55a)]: - @vercel/next@4.15.31 ## @vercel/config@0.0.33 ### Patch Changes - Fix rewrite regexp conversion when header transforms are present ([#15134](#15134)) ## @vercel/next@4.15.31 ### Patch Changes - Added support for `regions` and `functionFailoverRegions` in per-function configuration from `vercel.json` for Next.js projects. ([#15149](#15149)) ## @vercel/python-runtime@0.4.3 ### Patch Changes - fix formatting and lint ([#15142](#15142))  > [!NOTE] > Low Risk Change > > This PR is an automated Changesets release that only bumps version numbers in package.json files, updates CHANGELOG.md files, and deletes changeset markdown files - no code logic changes. > > - Version bumps in package.json files (vercel, @vercel/config, @vercel/next, @vercel/python-runtime) > - CHANGELOG.md updates documenting previous changes > - Deleted .changeset/*.md files consumed by release process > > <sup>Risk assessment for [commit 3b54c69](https://github.com/vercel/vercel/commit/3b54c6956719db3f1dfd50629330f42ab8143af6).</sup>  Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

RobbyUitbeijerse · 2026-02-23T09:16:47Z

Hey Vercel team, our existing project (without any vercel.json) started running into the following since last Friday. Not quite sure if it's related but it might be good to know. This is the only region related PR I could find that was recently closed, so it might be related.

15:16:38.486 
Build Completed in /vercel/output [4m]
15:16:38.850 
Deploying outputs...
15:16:43.883 
Error: Invalid region: auto, allowed values are: cdg1, arn1, dub1, lhr1, iad1, sfo1, pdx1, cle1, gru1, hkg1, hnd1, icn1, kix1, sin1, bom1, syd1, fra1, cpt1, dxb1, yul1

To clarify, deployments were fine before Friday afternoon, we haven't made any changes in the Vercel dashboard and we do have regions selected in the Settings > Functions (cdg1, dub1, fra1), I also attempted to just change regions, redeploy, change them back etc to make sure invalid config wasn't cached somewhere in the build cache.

[edit] I found the cause, but it did curiously start being an issue since last Friday. We had it in our project for months already, even though it was probably invalid the moment we introduced it. The culprit was a route with the following defined:

export const preferredRegion = 'auto';

ctgowrie · 2026-02-23T14:39:04Z

Hey Vercel team, our existing project (without any vercel.json) started running into the following since last Friday. Not quite sure if it's related but it might be good to know. This is the only region related PR I could find that was recently closed, so it might be related.
15:16:38.486 
Build Completed in /vercel/output [4m]
15:16:38.850 
Deploying outputs...
15:16:43.883 
Error: Invalid region: auto, allowed values are: cdg1, arn1, dub1, lhr1, iad1, sfo1, pdx1, cle1, gru1, hkg1, hnd1, icn1, kix1, sin1, bom1, syd1, fra1, cpt1, dxb1, yul1
To clarify, deployments were fine before Friday afternoon, we haven't made any changes in the Vercel dashboard and we do have regions selected in the Settings > Functions (cdg1, dub1, fra1), I also attempted to just change regions, redeploy, change them back etc to make sure invalid config wasn't cached somewhere in the build cache.

[edit] I found the cause, but it did curiously start being an issue since last Friday. We had it in our project for months already, even though it was probably invalid the moment we introduced it. The culprit was a route with the following defined:

export const preferredRegion = 'auto';

@RobbyUitbeijerse thanks for the report. Can you please file a Vercel support ticket with your project information so we can take a deeper look?

RobbyUitbeijerse · 2026-02-23T15:07:46Z

@ctgowrie thanks for getting back so quickly! done and done. I didn't actually add the information I added in later in my previous comment and it doesn't seem to be possible to add some context after creating the case for support, but let me know if I can help out by providing more info somehow

ctgowrie · 2026-02-23T18:29:35Z

@ctgowrie thanks for getting back so quickly! done and done. I didn't actually add the information I added in later in my previous comment and it doesn't seem to be possible to add some context after creating the case for support, but let me know if I can help out by providing more info somehow

@RobbyUitbeijerse Can you share a link to the support case? Feel free to send to my email at casey.gowrie@vercel.com

This reverts commit 5d1f55a.

This reverts commit 5d1f55a. Vercel build system does not properly support per function regions yet, so revert this PR temporarily while we land more robust support there.

Support per function regions from vercel.json

d0c28fa

ctgowrie requested review from a team, huozhi, ijjk, timneutkens and ztanner as code owners February 19, 2026 18:38

ijjk approved these changes Feb 19, 2026

View reviewed changes

packages/next/src/utils.ts Outdated Show resolved Hide resolved

better region equality check

2c3a826

vercel bot deployed to Preview February 19, 2026 18:53 View deployment

Timer approved these changes Feb 19, 2026

View reviewed changes

ctgowrie merged commit 5d1f55a into main Feb 19, 2026
225 of 227 checks passed

ctgowrie deleted the cgowrie/per-func-regions branch February 19, 2026 19:22

vercel-release-bot mentioned this pull request Feb 19, 2026

Version Packages #15150

Merged

ctgowrie added a commit that referenced this pull request Feb 23, 2026

Revert "Support per function regions from vercel.json (#15149)"

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This reverts commit 5d1f55a.

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Support per function regions from vercel.json#15149

Support per function regions from vercel.json#15149
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