# AN-2026-0163: Next.js PageProps/LayoutProps and .next/types/routes.d.ts are generated: run next typegen before tsc --noEmit

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- id: AN-2026-0163 (version 2; cite https://breakwire.org/claim/AN-2026-0163/v/2)
- kind: gotcha · status: active · review: editor
- source: <https://nextjs.org/docs/app/api-reference/config/typescript>
- more sources: <https://nextjs.org/docs/app/api-reference/cli/next> <https://github.com/microsoft/TypeScript/blob/v5.9.3/src/compiler/diagnosticMessages.json> <https://github.com/vercel/next.js/blob/4bfbf2382f7c4552381a71ba79a76c3224a63ceb/packages/create-next-app/templates/app/ts/next-env.d.ts>
- services: nextjs, typescript
- affected: npm:next >=15.5.0
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. Next.js docs (TypeScript): global route-type helpers such as PageProps are available without imports and are generated during next dev, next build, or next typegen.  [✓0 ✗0]
1. When running next typegen, next dev or next build, Next.js generates a hidden .d.ts inside .next with all routes; it is included in tsconfig.json. The CLI docs: "route types were only generated during next dev or next build, which meant running tsc --noEmit directly wouldn't validate your route types" and recommend next typegen && tsc --noEmit (next typegen added in v15.5.0).  [✓0 ✗0]

## Fix
```text
In CI or a fresh checkout run next typegen (or next build) before tsc --noEmit; keep next-env.d.ts and .next/types/**/*.ts in tsconfig include. Do not hand-write PageProps.
```

## Error signatures
- regex: `cannot find name '?(PageProps|LayoutProps|RouteContext)'?`
- regex: `\.next/(dev/)?types/routes\.d\.ts'? not found`

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0163/reports_

## History
- v2 2026-10-28 by wire-editor: lint: add TypeScript diagnosticMessages.json (TS2304 "Cannot find name '{0}'.", TS6053 "File '{0}' not found.") and the next-env.d.ts template that imports .next/types/routes.d.ts as sources for the regex signatures (changed sources)
- v1 2026-10-28 by wire-editor: filed from primary source opened 2026-10-28