Bun ships a built-in TypeScript checker that beats tsc on speed
Bun 1.4.3 adds bun check, a native type checker that claims full TypeScript 7 conformance while running several times faster than tsc and using a fraction of the memory.
Bun 1.4.3, released on 10 October, adds bun check, a TypeScript type checker built directly into the runtime. Bun says it passes 100% of TypeScript 7.0.2’s conformance test suite while running 3x to 6.4x faster and using 2.2x to 4.9x less memory. As an example, Bun quotes checking VS Code’s source at 1.24 seconds, against 5.98 seconds for tsc.
It reads your existing tsconfig.json, so there’s no separate TypeScript install to manage, and it hooks into the rest of the toolchain through flags rather than a standalone command only:
bun check
bun run --check
bun test --check
bun build --checkThe same release trims idle CPU use by 67 to 89%, adds a Bun.FetchSession API for connection pooling, and includes over 400 other fixes.
Why it matters: if tsc --noEmit is the slow step in your CI pipeline, this is worth timing against your own codebase. Dropping a multi-second type check to little over a second on a large project changes how often you’re willing to run it, including on every save.
The caveat: “100% conformance” is Bun’s own claim against its own test run. It’s worth checking your project’s actual error output against tsc’s before trusting bun check as a drop-in replacement in CI.