nextjs - ✅(Solved) Fix `next build` shows generic "Invalid segment configuration export detected" when `config.matcher` uses `String.raw` in `proxy.ts` [2 pull requests, 3 comments, 3 participants]

nextjs2026-02-13 03:42:17

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vercel/next.js#89937•Fetched 2026-04-08 00:21:01

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Error Message

Observe this error at the end of build:

Build fails with a generic segment config error.
Error should clearly identify src/proxy.ts and explain that config.matcher must be statically analyzable (or literal), with a specific diagnostic for String.raw.
The issue is specifically about error reporting quality: the build failure reason is not pinpointed even though the root cause is String.raw in config.matcher inside proxy.ts.

Root Cause

Reproducible locally.
The issue is specifically about error reporting quality: the build failure reason is not pinpointed even though the root cause is String.raw in config.matcher inside proxy.ts.

Fix Action

Fixed

Fixed by PR: fix: support String.raw tagged templates in segment config extraction (https://github.com/vercel/next.js/pull/90162)
Fixed by PR: fix: include file path in segment config validation error (https://github.com/vercel/next.js/pull/91131)

PR fix notes

PR #90162: fix: support `String.raw` tagged templates in segment config extraction

Repository: vercel/next.js
Author: sleitor
State: open | merged: False
Link: https://github.com/vercel/next.js/pull/90162

Description (problem / solution / changelog)

Summary

Fixes #89937

When using String.raw in middleware config.matcher:

export const config = {
  matcher: String.raw`/api/:path*`,
}

The build fails with a generic error:

Invalid segment configuration export detected. This can cause unexpected behavior...

Root Cause

extractExportedConstValue in extract-const-value.ts handles TemplateLiteral nodes but not TaggedTemplateExpression nodes. String.raw\...`produces aTaggedTemplateExpression` in the SWC AST.

Fix

Add support for TaggedTemplateExpression where the tag is String.raw
Return the raw quasis value (preserving backslashes, as String.raw does)
Expressions in String.raw templates throw UnsupportedValueError (same as regular templates)
Non-String.raw tagged templates throw UnsupportedValueError
Added unit tests for all cases

Test Plan

Added unit tests for extractExportedConstValue covering:
- String.raw with simple path patterns
- String.raw with backslash sequences (preserved as-is)
- Array with mixed String.raw and string literal elements
- String.raw with expressions (throws)
- Non-String.raw tagged templates (throws)

Changed files

packages/next/src/build/analysis/extract-const-value.ts (modified, +33/-0)
test/unit/extract-const-value.test.ts (added, +58/-0)

PR #91131: fix: include file path in segment config validation error

Repository: vercel/next.js
Author: mvanhorn
State: open | merged: False
Link: https://github.com/vercel/next.js/pull/91131

Description (problem / solution / changelog)

Summary

The generic "Invalid segment configuration export detected" error now includes the specific file path that has the issue
Added a hint about static analyzability requirements (e.g., String.raw, template literals with variables, function calls are not supported)
Added a link to the invalid-page-config docs page for more context

Before:

⨯ Invalid segment configuration export detected. This can cause unexpected behavior from the configs not being applied. You should see the relevant failures in the logs above. Please fix them to continue.

After:

⨯ Invalid segment configuration export detected in "src/proxy.ts". The exported `config` must use statically analyzable values. Dynamic expressions like `String.raw`, template literals with variables, or function calls are not supported.
Read More - https://nextjs.org/docs/messages/invalid-page-config

Fixes #89937

Test plan

Updated existing test in test/production/exported-runtimes-value-validation/ to verify the improved error message includes:
- The "Invalid segment configuration export detected" text
- The middleware file reference
- The "statically analyzable" hint

This contribution was developed with AI assistance (Claude Code).

Changed files

packages/next/src/build/index.ts (modified, +7/-4)
test/production/exported-runtimes-value-validation/index.test.ts (modified, +9/-0)

Code Example

npm install

---

npm run build

---

⨯ Invalid segment configuration export detected. This can cause unexpected behavior from the configs not being applied. You should see the relevant failures in the logs above. Please fix them to continue.

---

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 25.2.0
Binaries:
  Node: 24.11.1
  npm: 11.6.2
  Yarn: N/A
  pnpm: 10.28.1
Relevant Packages:
  next: 16.1.3
  react: 19.2.3
  react-dom: 19.2.3
  typescript: 5.9.3
Next.js Config:
  output: N/A

RAW_BUFFERClick to expand / collapse

Link to the code that reproduces this issue

https://github.com/ahxar/next-proxy-string-raw-repro

To Reproduce

Clone the reproduction repo.
Install dependencies:
```
npm install
```
Run:
```
npm run build
```

Observe this error at the end of build:

⨯ Invalid segment configuration export detected. This can cause unexpected behavior from the configs not being applied. You should see the relevant failures in the logs above. Please fix them to continue.

In src/proxy.ts, remove String.raw and use a plain string literal in config.matcher.
Run npm run build again and it succeeds.

Current vs. Expected behavior

Current behavior:

Build fails with a generic segment config error.
Message says "You should see the relevant failures in the logs above", but there is no actionable failure pointing to src/proxy.ts / config.matcher.

Expected behavior:

Error should clearly identify src/proxy.ts and explain that config.matcher must be statically analyzable (or literal), with a specific diagnostic for String.raw.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 25.2.0
Binaries:
  Node: 24.11.1
  npm: 11.6.2
  Yarn: N/A
  pnpm: 10.28.1
Relevant Packages:
  next: 16.1.3
  react: 19.2.3
  react-dom: 19.2.3
  typescript: 5.9.3
Next.js Config:
  output: N/A

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

Middleware

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

next build (local)

Additional context

Reproducible locally.
The issue is specifically about error reporting quality: the build failure reason is not pinpointed even though the root cause is String.raw in config.matcher inside proxy.ts.

extent analysis

Fix: Make `config.matcher` a statically‑analyzable literal

Next.js middleware matcher must be a literal string (or an array of literals) that the compiler can evaluate at build time.
String.raw creates a computed value, so the segment‑config validator throws the generic “Invalid segment configuration export detected” error.

Step‑by‑step

Open src/proxy.ts.

Replace the String.raw call with a plain string (or a template literal that resolves to a literal).

// BEFORE
export const config = {
  matcher: String.raw`/api/:path*`,
};

// AFTER – simple literal
export const config = {

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nextjs - ✅(Solved) Fix `next build` shows generic "Invalid segment configuration export detected" when `config.matcher` uses `String.raw` in `proxy.ts` [2 pull requests, 3 comments, 3 participants]

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Error Message

Root Cause

Fix Action

Fixed

PR fix notes

PR #90162: fix: support String.raw tagged templates in segment config extraction

Description (problem / solution / changelog)

Summary

Root Cause

Fix

Test Plan

Changed files

PR #91131: fix: include file path in segment config validation error

Description (problem / solution / changelog)

Summary

Test plan

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: Make config.matcher a statically‑analyzable literal

Step‑by‑step

Still need to ship something?

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TRENDING

PR #90162: fix: support `String.raw` tagged templates in segment config extraction

Fix: Make `config.matcher` a statically‑analyzable literal