Adopt TypeScript 7 through the supported dual-compiler toolchain

[artiphishle]

Goal

Adopt TypeScript 7 as the canonical native compiler for Devtools and managed Ankhorage repositories without breaking the TypeScript compiler API consumers that still require TypeScript 6.

This must supersede Renovate PR #94. That PR only changes typescript from ~6.0.3 to ~7.0.2; it is not a valid TypeScript 7 migration.

Investigation result

PR #94 builds with TypeScript 7, then CI fails while loading the shared ESLint config:

typescript-eslint does not support TS 7.0.
Error [ERR_INTERNAL_ASSERTION]

This is expected current ecosystem behavior, not a transient Devtools lint defect:

• TypeScript 7 is the native Go compiler and language server.
• TypeScript 7.0 deliberately has no JavaScript compiler API. A new API is expected in 7.1.
• typescript-eslint@8.69.0 requires the TypeScript API and declares typescript >=4.8.4 <6.1.0.
• Microsoft therefore documents a side-by-side installation for TypeScript 7.0:

{
  "devDependencies": {
    "@typescript/native": "npm:typescript@~7.0.2",
    "typescript": "npm:@typescript/typescript6@~6.0.2"
  }
}

With the repository-pinned Bun 1.4.0, this was validated locally:

node_modules/.bin/tsc --version   -> Version 7.0.2
node_modules/.bin/tsc6 --version  -> Version 6.0.3
require('typescript').version     -> 6.0.3

The prototype passed Devtools build, lint loading, format check, Knip, 66 tests, TypeScript 7 typecheck, TypeScript 6 comparison typecheck, and docs validation.

A packaged-consumer smoke test found an additional owner requirement:

• a consumer with only typescript@7.0.2 still makes the published ankhorage-eslint wrapper load TypeScript 7 and crash;
• adding TypeScript 6 only as a dependency of @ankhorage/devtools does not reliably isolate typed linting because package-manager hoisting can place typescript-eslint beside the consumer's TypeScript 7;
• the consumer itself must receive the documented dual aliases. With those aliases, the same packaged wrapper executes typed lint rules normally while tsc remains TypeScript 7.

Sources:

• TypeScript 7.0 announcement and side-by-side setup
• typescript-eslint TypeScript 7 API tracking issue
• TypeScript 7 VS Code extension
• Related Devtools update propagation: Automate Devtools toolchain updates and downstream sync #64

MUST

• Supersede/close chore: defer TypeScript 7 until ESLint support #94; do not merge a direct replacement of the canonical typescript package with TypeScript 7.
• Define one canonical Devtools-owned TypeScript transition policy with two explicit lanes:
  • @typescript/native aliases stable typescript@7 and owns the tsc binary used by build/typecheck;
  • typescript aliases stable @typescript/typescript6 and owns the current JavaScript API used by typescript-eslint and other programmatic consumers.
• Apply the dual aliases to Devtools itself and regenerate bun.lock with the repository-pinned Bun 1.4.0. A frozen install must reproduce tsc -> 7.x, tsc6 -> 6.x, and require('typescript') -> 6.x.
• Make the package synchronization contract write the same two canonical dev dependencies into ordinary managed consumers. It must replace direct typescript@7, remove obsolete @typescript/native-preview declarations, preserve unrelated manifest fields, and remain byte-stable on a second sync.
• Keep normal build and typecheck entrypoints on tsc so they use the native compiler. Do not rename the production compiler command to a repository-specific alias or keep two competing build paths.
• Make the TypeScript 6 compatibility lane explicit in tests and documentation as a current TypeScript 7.0 ecosystem requirement, not as a legacy fallback. Record the removal gate: TypeScript must publish the new stable API and typescript-eslint must support it before the TS6 lane is removed.
• Update the managed VS Code contract so repositories actually use the TypeScript 7 language server: recommend TypeScriptTeam.native-preview, enable js/ts.experimental.useTsgo, and point js/ts.tsdk.path at the native package alias. Keep the documented ability to disable the TS7 language server when a current tool requires TypeScript 6.
• Add regression coverage for:
  • package metadata and both alias ranges;
  • binary/API version selection (tsc, tsc6, and require('typescript'));
  • migration of a direct TypeScript dependency through package sync;
  • idempotent package and lockfile synchronization;
  • a packed consumer fixture proving ankhorage-eslint performs typed linting while the consumer's tsc is TypeScript 7;
  • managed VS Code assets.
• Verify Renovate tracks the two aliased packages independently and cannot recreate chore: defer TypeScript 7 until ESLint support #94's invalid direct-major update. Add configuration tests for the alias behavior rather than relying on a manual ignore.
• Validate Devtools under both compilers during the migration: TypeScript 7 is the primary build/typecheck; TypeScript 6 must also compile with stableTypeOrdering enabled and without ignoreDeprecations, matching Microsoft's transition precondition.
• Run the complete Devtools validation contract, add the required package changeset, release the owner package, and propagate the released policy through the existing Automate Devtools toolchain updates and downstream sync #64 automation rather than patching consumers manually.

SHOULD

• Record before/after build and typecheck timings so the native compiler adoption has measurable acceptance evidence.
• Audit managed repositories for TypeScript 7 CLI differences, especially scripts that pass source files to tsc while a tsconfig.json exists, and for tools/frameworks that embed the compiler API. Fix the owning package or keep those API calls on the canonical TS6 lane; do not add repository-local shims.
• Add or update Doctor enforcement so a managed repository reports drift when tsc resolves to TypeScript 6, the typescript API resolves to TypeScript 7, or only one half of the current dual policy is installed.
• Prove released end-to-end propagation in at least one normal package consumer and Studio, including frozen install, build, typed lint, tests, and typecheck.
• Track typescript-eslint#10940 and TypeScript 7.1. Once the new API is stable and supported, open a focused cleanup issue to remove the TS6 lane, its editor fallback, and transition-only assertions in one canonical change.

Acceptance

• Devtools CI is green with TypeScript 7 executing tsc and TypeScript 6 satisfying typed ESLint/API consumers.
• A released, synchronized consumer has the same binary/API split and its published Devtools lint wrapper runs without the chore: defer TypeScript 7 until ESLint support #94 crash.
• Managed editor settings select the TypeScript 7 language server.
• Renovate updates the native and API lanes without collapsing them into an unsupported single TypeScript 7 dependency.
• The release and downstream synchronization follow existing Devtools ownership; no consumer-specific compatibility implementation or manual repository-by-repository migration is introduced.