Pin TypeScript to 6.x: the 7.0 native port breaks Next.js build & typescript-eslint (blocks #499)

[NiveditJain]

Summary

Dependabot PR #499 bumps typescript 6.0.3 → 7.0.2 and turns every CI job red. TypeScript 7.0 is the native (Go) port ("Corsa"/tsgo), and its npm package is not a drop-in replacement for the JS-based 6.x line. This issue records the root cause, the reproduction, and the recommended handling so the bump isn't retried blindly.

Recommendation: stay on typescript@6.x for now, and tell Dependabot to ignore typescript major-version updates. Revisit when Next.js and typescript-eslint support the native port.

Why it breaks

The typescript@7.0.2 package ships the native compiler, not the classic JS API:

• Its package.json exports map points the main entry "." at ./lib/version.cjs — a version stub. The classic compiler API (createProgram, transpileModule, parseJsonConfigFileContent, …) is no longer at the main entry; only an experimental subset is exposed under typescript/unstable/*.
• lib/ contains only a thin launcher (tsc.js, getExePath.js) plus per-platform native binaries (@typescript/typescript-linux-x64@7.0.2, etc.). There is no lib/typescript.js.

Every type-aware tool in this repo consumes the classic programmatic API, so the bump breaks them.

Because package.json's prepare script runs bun run build (→ next build) on every bun install, the failure hits the very first step of all CI jobs (build, test×3, quality, docs, test-e2e), not just build.

Reproduction (on a throwaway branch, TS pinned to 7.0.2)

1. next build fails — even with type-checking disabled. Next.js 16.2.x runs a "TypeScript config validation" step that needs the classic API. With typescript.ignoreBuildErrors: true it does skip type-checking (✓ Compiled successfully → Skipping validation of types), but config validation still runs and still needs the API. Under CI=true (how CI runs) Next can't self-repair and the build exits 1. Locally it only "passed" by having Next shell out to npm install mid-build to fetch a working TypeScript — impossible under --frozen-lockfile / no-network CI.

   CI error:

   It looks like you're trying to use TypeScript but do not have the required package(s) installed.
   

2. typescript-eslint refuses TS 7. eslint-config-next@16.2.10 bundles typescript-eslint@8.64.0, whose peer dependency is:

   peer typescript@">=4.8.4 <6.1.0"   ← doesn't allow 6.1+, let alone 7.0
   

   So bun run lint (the quality job) breaks independently of Next.

3. The native tsc binary itself works. bunx tsc --noEmit runs on the native compiler — that's the one piece that is forward-compatible.

Blocked on upstream

A port would require released versions of Next.js and typescript-eslint that speak the native-port API. Those don't exist yet — typescript@7.0.2 only just became latest; the ecosystem is mid-migration. Nothing in this repo can bridge that gap.

Recommended handling

Now:

• Keep typescript pinned to 6.x.
• Add a Dependabot ignore rule so the major bump stops being re-proposed weekly:

  # .github/dependabot.yml — under the `bun` ecosystem
  ignore:
    - dependency-name: "typescript"
      update-types: ["version-update:semver-major"]

• Close build(deps-dev): Bump typescript from 6.0.3 to 7.0.2 #499.

Later (revisit criteria): once Next.js and typescript-eslint ship native-port support. The incremental adoption path is to add @typescript/native-preview (tsgo) as a separate fast type-check tool while keeping typescript@6.x as the API the ecosystem consumes — not a straight swap of the typescript package.

References

• PR build(deps-dev): Bump typescript from 6.0.3 to 7.0.2 #499 — the Dependabot bump this issue tracks
• TypeScript native port (typescript@7.x / @typescript/native-preview)