TypeScript version migration guide (5.x to 6 to 7, tsgo native port). Use for TS 6 tsconfig breaking changes, TS 7 Go rewrite rollout, or TS5xxx deprecation codes.
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TypeScript version migration guide (5.x to 6 to 7, tsgo native port). Use for TS 6 tsconfig breaking changes, TS 7 Go rewrite rollout, or TS5xxx deprecation codes.
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LanguageTypeScript
LicenseMIT
📦 Ships with claude-skills
</> SKILL.md
typescript-migration.SKILL.md
---name: typescript-migration
description: "TypeScript version migration guide (5.x to 6 to 7, tsgo native port). Use for TS 6 tsconfig breaking changes, TS 7 Go rewrite rollout, or TS5xxx deprecation codes."
license: MIT
---# TypeScript Migration
Authoritative migration guide for TypeScript 5.x → 6 → 7 (native Go port). Sourced from Microsoft's official announcements.
## Status
- **Skill Status**: Production Ready
- **Last Updated**: 2026-07-09
- **TS 6.0 Released**: 2026-03-17 (Final) — last JavaScript-based release
- **TS 7.0 Released**: 2026-07-08 — native Go port ("Corsa"), stable
- **Authoritative Sources**:
- TS 7.0 release: https://devblogs.microsoft.com/typescript/announcing-typescript-7-0/
- TS 6.0 beta: https://devblogs.microsoft.com/typescript/announcing-typescript-6-0-beta/
- TS 6 → 7 diff tracker: https://github.com/microsoft/typescript-go/blob/main/CHANGES.md
- ts5to6 tool: https://github.com/andrewbranch/ts5to6
## The Golden Rule
> NEVER skip TypeScript 6. The only supported paths are **5.x → 6 → 7**.
>
> Skipping TS 6 produces a wall of hard errors because TS 7 removes everything TS 6 deprecated. Use `"ignoreDeprecations": "6.0"` only as a temporary pause inside TS 6; it does NOT work in TS 7.
## Quick Triage (1 Minute)
- `npx tsc` runs TS 7 (via the `@typescript/native` alias).
- Tools importing `typescript` (typescript-eslint, ts-morph) transparently get TS 6's API via `@typescript/typescript6`.
- A `tsc6` executable is also available if a TS 6 invocation is needed directly.
- Remove this workaround once TS 7.1 ships the new API.
## The 4-Step Standard Workflow
1. **Detect** — `scripts/detect-ts-version.sh` reports the installed version.
2. **Audit** — `scripts/audit-ts7-breakers.sh` detects breakers BEFORE any upgrade. `scripts/ts6-deprecation-scan.sh` extracts TS5xxx codes from `tsc` output.
3. **Migrate** — follow `references/migration-playbooks.md` for the appropriate path. Run `ts5to6 --fixBaseUrl` and `ts5to6 --fixRootDir` if the user explicitly approves (these are official Microsoft-endorsed codemods). All other changes are manual.
4. **Verify** — `scripts/compare-tsc7-tsc6.sh` diffs diagnostic codes between TS 7 `tsc` and TS 6 `tsc6`. Match on TSxxxx codes, NOT message text (wording differs between compilers). Delete stale `.tsbuildinfo` files before the first TS 7 run (incompatible between the JS and Go compilers).
## Critical Rules
### Always
- ✅ Migrate through TS 6 — never skip it.
- ✅ Match on diagnostic codes (TSxxxx), not message wording.
- ✅ Delete stale `.tsbuildinfo` before the first TS 7 run.
- ✅ Cite Microsoft's official blog posts as authoritative; treat third-party tutorials as secondary.
- ✅ Run `audit-ts7-breakers.sh` BEFORE any upgrade.
### Never
- ❌ Never install `@typescript/native-preview` for stable use — it's the legacy nightly package; stable is the standard `typescript` package.
- ❌ Never assert the unverified third-party claims listed in `references/unverified-claims.md` (e.g. "moduleResolution default is node16", "`--ts6-migration` flag exists", "ES5 target is removed in 6", "`--keyofStringsOnly` was removed").
- ❌ Never recommend `ts-migrating` (the tool) for TS version migration — it only helps tighten compilerOptions within a version.
- ❌ Never assume VS Code needs a setting key to enable TS 7 — install the official extension; it auto-enables.
- ❌ Never auto-edit user source via custom scripts — only detection/audit scripts and officially-blessed codemods (`ts5to6`).
## The `ts-migrating` Tool — Conditional Offer
Offer this tool ONLY when the user wants to enable a stricter `compilerOption` (e.g. `noUncheckedIndexedAccess`, `strict`, `erasableSyntaxOnly`) on an existing large codebase — NOT for version migration.
Gate conditions (all must hold):
- Existing, non-greenfield TypeScript project.
- The goal is enabling a `compilerOption` incrementally.
- This is not a tsgo / TS-7 migration.
Warnings:
- The `annotate` subcommand rewrites source — run on a clean git tree and review the diff.
- The IDE plugin has ZERO effect on `tsc`; wire `ts-migrating check` into CI for it to matter.
- `// @ts-migrating` markers are tech debt needing a cleanup sweep.
- This is NOT Airbnb's `ts-migrate` (different tool — JS → TS conversion).
Full install, commands, and gate logic in `references/ts-migrating-tool-guide.md`.
## Common Error Codes
| Code | Meaning | Action |
|---|---|---|
| TS5011 | rootDir mismatch | Set `"rootDir": "./src"` |
| TS5101 | Option deprecated, stops in TS {ver} | Add `"ignoreDeprecations": "6.0"` (TS 6 only) or fix |
| TS5102 | Option removed | Remove from tsconfig |
| TS5107 | Option=value deprecated | Same as TS5101 |
| TS5108 | Option=value removed | Remove |
| TS5111 | Migration info (baseUrl, node10) | See `references/ts6-breaking-changes.md` |
Load these reference files when the user needs detail beyond the quick-reference above:
| Load This File | When |
|---|---|
| `references/ts6-breaking-changes.md` | Migrating to TS 6; need full PR-cited detail on each default change, deprecation, or syntax change |
| `references/ts7-go-rewrite.md` | Adopting TS 7; need install detail, compat matrix, performance tables, known gaps |
| `references/ecosystem-compatibility.md` | Checking whether a specific tool (typescript-eslint, ts-morph, ts-node, vite, webpack, vitest, etc.) works under TS 7 |
| `references/migration-playbooks.md` | Need ordered checklists for 5→6, 6→7, or 5→7-via-6 |
| `references/ts-migrating-tool-guide.md` | User wants to enable a stricter compilerOption incrementally on an existing large codebase |
| `references/unverified-claims.md` | Encountering a claim that contradicts official sources; verify before asserting |
## Dependencies
- **Required for migration**: `typescript` (target version), `tsconfig.json` in the project root.
- **Optional helpers**:
- `@andrewbranch/ts5to6` — official codemod for `baseUrl` / `rootDir`.
- `@typescript/typescript6` — side-by-side API compat for TS 7.
- `ts-migrating` — incremental strict-flag rollout (see guide).
## Package Versions (Verified 2026-07-09)
```json
{
"devDependencies": {
"typescript": "^7.0.2",
"@typescript/typescript6": "^6.0.2"
},
"optionalHelpers": {
"@andrewbranch/ts5to6": "latest",
"ts-migrating": "latest"
}
}
```
All facts in this skill are cited to Microsoft's official TypeScript blog (devblogs.microsoft.com/typescript). Third-party tutorial claims that conflict with official sources are catalogued in `references/unverified-claims.md` and treated as suspect.
