Bun drafts ahead-of-time TypeScript compiler; Claude Code starts twice as fast

JavaScript runtime Bun opened a draft that compiles TypeScript to machine code before it runs, a change of more than a million lines.

On GitHub, Bun creator Jarred Sumner opened a draft pull request for 'bun build --compile --aot' on Oct 17. It adds 1,060,888 lines across 11,520 files; Sumner notes most of the million lines are tests, with over 613,000 in the test suite alone.

Benchmarks in the PR show Claude Code's CLI built this way reaching its first prompt in 163 ms instead of 346 ms, using a third of the CPU time and cutting anonymous memory from 184 MB to 50 MB. The TypeScript 6 compiler ran 3.7 times faster than on current Bun.

A post calling it 'a million lines of mythos 5.5 code' drew 1,000 likes on X, though the PR does not say which model, if any, wrote it. Anthropic acquired Bun last year. Sumner says it is still experimental, with 41 failing test files.