[15.5] Reject TypeScript >= 7.0 with an actionable error#96110
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lukesandberg merged 3 commits intoJul 24, 2026
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TypeScript 7's native compiler no longer ships the JavaScript compiler API
(`typescript/lib/typescript.js`) that Next.js loads via `require('typescript')`,
producing surprising failures with no actionable message. This was reported
against the 16.2 line in #95801.
Because the missing API file makes an installed TS7 look like a missing
dependency, expose the resolved `typescript/package.json` path from
`hasNecessaryDependencies` and check the installed version up front, throwing a
CompileError with guidance to install TypeScript 6 or upgrade Next.js before the
`require()` runs. Prereleases (7.0.0-beta/-rc, nightly 7.0.0-dev.*) are rejected
too via the `7.0.0-0` prerelease sentinel.
Minimal mitigation for the 15.5.x line; mirrors the next-16-2 mitigation (#95837).
Auto-install version is already pinned on this line via getTypeScriptPackageSpec,
so no install-specifier change is needed here.
Contributor
Failing CI jobsCommit: 131bdac | About building and testing Next.js |
lukesandberg
marked this pull request as ready for review
July 23, 2026 21:58
bgw
approved these changes
Jul 23, 2026
lukesandberg
enabled auto-merge (squash)
July 23, 2026 22:14
The `next lint` first-time-setup tests install `eslint-config-next`, whose transitive deps (e.g. `@typescript-eslint/*` pulling `eslint-visitor-keys@5`) have dropped Node 18 support. npm/pnpm honor the `overrides` pin that works around this, but yarn 1.x does not apply it to the tarball dependency, so the install fails and `.eslintrc.json` is never written. Drop the yarn install variant and skip the three default-package-manager config-creation tests (which also resolve to yarn in the CI environment). The npm and pnpm install variants still cover the first-time-setup path. This is a 15.5-only maintenance-branch workaround; the failure is unrelated to product code.
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Summary
A minimal mitigation for the TypeScript 7 problem on the
15.5.xline, ported from thenext-16-2mitigation (#95837).TypeScript 7's native compiler no longer ships the JavaScript compiler API (
typescript/lib/typescript.js) that Next.js loads viarequire('typescript'), so an installed TS7 produces surprising failures with no actionable message. This was reported against 16.2 in #95801.What it does
hasNecessaryDependenciesnow also exposes the resolvedtypescript/package.jsonpath.verifyTypeScriptSetupreads that version up front and, if it's>= 7.0.0(including prereleases —7.0.0-beta/-rc, nightly7.0.0-dev.*, via the7.0.0-0sentinel withincludePrerelease), throws aCompileErrorwith guidance to install TypeScript 6 or upgrade Next.js, before therequire()runs.Unlike the 16.2 mitigation, no install-specifier change is needed here: the
15.5line already pins TypeScript auto-installs viagetTypeScriptPackageSpec(typescript@5.8.2) rather than pullinglatest.Applies to both
next devandnext build.Notes
15.5; the fullexperimental.useTypeScriptClibackend (real TS7 support) is a separate, larger effort and was considered overkill for this stable line.next-16-2mitigation [16.2] Reject TypeScript >= 7.0 with an actionable error (mitigation for #95801) #95837, and full backport [Backport] Fixes to support TypeScript 7 #95831.Verification
pnpm --filter=next build5.8.2/6.x(incl.6.0.0-beta) are not rejected;7.0.0-dev.*/7.0.0-beta/7.0.0-rc/7.0.0/7.0.2are rejected.typescript@7+next@15.5:next buildandCI=1 next buildexit non-zero with the actionable error instead of the opaque failure.