What is the native (Go) port of the TypeScript compiler?

TypeScript 7 is a native port: the compiler and language service written in TypeScript (internal codename Strada, versions up to 6.x) were ported to Go (Corsa). The team's stated aim was to keep it faithful: same logic and structure, so results stay consistent between the two. Go was chosen because idiomatic Go resembles the existing code, giving a structurally similar codebase that makes porting changes feasible, with memory-layout control and a garbage collector that costs little for a batch compiler (from the team's "Why Go?" discussion).

Gains come from native code plus parallelism: 7.0 parses, type-checks and emits in parallel. The announcement reports 8x to 12x faster full builds on large open-source projects (vscode 125.7s to 10.6s) and an editor that loads far faster.

What it means in practice:

• Install and CLI. npm i -D typescript now gives a native tsc (my 7.0.2 install used a per-platform binary package). The previews used @typescript/native-preview and tsgo; nightlies move to typescript@next. New flags: --checkers, --builders, --singleThreaded.
• Same language, 6.0 defaults. 7.0 adopts 6.0's defaults (strict: true, types: [], …) and turns 6.0's deprecations into hard errors, such as target: es5 and moduleResolution: node10.
• Editor. The language server speaks the Language Server Protocol instead of the old tsserver protocol.
• No JavaScript API in 7.0. Tools that import typescript (typescript-eslint, Volar-based Vue/Astro/Svelte tooling) stay on 6.0, side by side via @typescript/typescript6 (which provides tsc6). A new API is expected in 7.1.

For migration I would first move to 6.0, fix its deprecations (--stableTypeOrdering helps compare outputs), then switch the CLI to 7.

# 38-file Vite/React app in this repo, tsc --noEmit, 3 runs each, Apple M1 Pro, wall time
5.9.3   1.09s  1.07s  1.15s
6.0.3   1.10s  1.02s  1.05s
7.0.2   0.21s  0.16s  0.16s      (--singleThreaded: 0.25s 0.24s 0.24s)

# deprecations: tsc --noEmit --target es5 --moduleResolution node a.ts
5.9.3  (no output)
6.0.3  error TS5107: Option 'moduleResolution=node10' is deprecated and will stop functioning in TypeScript 7.0. …
7.0.2  error TS5108: Option 'moduleResolution=node10' has been removed. Please remove it from your configuration.
       error TS5108: Option 'target=ES5' has been removed. …
# 6.0.3 with --ignoreDeprecations 6.0 → exit 0; 7.0.2 with it still → TS5108

# package.json: "@typescript/native": "npm:typescript@7.0.2", "typescript": "npm:@typescript/typescript6@6.0.2"
tsc -v → 7.0.2     tsc6 -v → 6.0.3     require("typescript").createProgram → function (6.0.3)

• Expecting identical speedups. On the repo's small app the gap was about 6x (about 1.1s to 0.16s), not 10x; the announced numbers are for large codebases and several cores. One machine, three runs each, no warm-up control.
• Importing the compiler API from 7.0. require("typescript") on 7.0.2 returned only { version, versionMajorMinor }; the 7.0 announcement says it ships no API. Pin typescript to the 6.0 compat package for tools that need it.
• Assuming 7.0 reads old configs. target: es5, moduleResolution: node10 and similar now fail with TS5108 and --ignoreDeprecations 6.0 no longer helps. Also tsc a.ts with a tsconfig.json present errors with TS5112 on 6.0.3 and 7.0.2 unless you pass --ignoreConfig.
• Treating --checkers/--singleThreaded as correctness knobs. The announcement says the number of checkers can, in rare cases, surface order-dependent results, so pin one number in CI. (Not reproduced here.)