typedRoutes invalid Link href is not enforced by tsc in a workspace app unless .next/types/link.d.ts is manually referenced

Link to the code that reproduces this issue

https://github.com/jakeleventhal/next-typed-routes-workspace-tsc-repro

To Reproduce

1. Clone the repo
2. Install dependencies:

bun install

3. Generate route types:

bun run -F @repro/web typegen

4. Confirm the generated files:

• apps/web/.next/types/routes.d.ts contains only /
• apps/web/.next/types/link.d.ts contains the next/link and next/navigation route augmentations
• apps/web/next-env.d.ts imports ./.next/types/routes.d.ts

5. Run TypeScript from the app package:

bun run -F @repro/web tsc
bun run -F @repro/web tsc:noemit

6. Notice that both commands succeed, even though apps/web/src/app/page.tsx contains an invalid route:

<Link href="/definitely-not-a-real-route">Broken typed route</Link>

7. Now run the comparison script that explicitly loads the generated link.d.ts file:

bun run -F @repro/web tsc:with-link-augmentation

8. Notice that this fails immediately with:

src/app/page.tsx(6,10): error TS2322: Type '"/definitely-not-a-real-route"' is not assignable to type 'UrlObject | RouteImpl<"/definitely-not-a-real-route">'.

Current vs. Expected behavior

Current:

• typedRoutes: true is enabled
• next typegen generates both routes.d.ts and link.d.ts
• In this workspace-style setup, both tsc --build and tsc --noEmit still accept an invalid Link href
• If I manually reference .next/types/link.d.ts, the same invalid route is rejected

Expected:

After next typegen, plain TypeScript checking should reject the invalid Link href without requiring a manual reference to .next/types/link.d.ts.

This expectation seems consistent with the docs for next typegen, which say:

next typegen && tsc --noEmit

should validate route usage externally.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
Binaries:
  Node: 24.12.0
  Bun: 1.3.12
Relevant Packages:
  next: 16.2.4
  react: 19.2.0
  react-dom: 19.2.0
  typescript: 5.9.3

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

TypeScript

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

next typegen, tsc --build, tsc --noEmit

Additional context

The repro is intentionally a tiny monorepo/workspace because I could not reproduce this in a standalone single-package Next app. The mismatch seems to depend on a shared tsconfig package + app package setup.

The generated next-env.d.ts in the repro currently looks like this:

/// <reference types="next" />
/// <reference types="next/image-types/global" />
import "./.next/types/routes.d.ts";

That appears to be enough for route metadata, but not enough for next/link route enforcement in this setup.

Start with the linked workspace reproduction and run bun install, bun run -F @repro/web typegen, and the three TypeScript commands. Compare apps/web/next-env.d.ts, .next/types/routes.d.ts, .next/types/link.d.ts, and apps/web/src/app/page.tsx to trace which generated declarations are loaded. Done means plain tsc commands reject the invalid Link href without a manual link.d.ts reference.