Theo ships tsc-rs, a Rust TypeScript compiler he never read
Five months of agent work, two token bills that differ by a factor of twenty, and zero lines of human review.
Theo released tsc-rs, a complete rewrite of the TypeScript compiler, type checker and LSP in Rust, built entirely by agents over five months. It is open source, shipped as a drop-in replacement for tsc, and he says he has not read a single line of the code.
I have not read a single line of the code.
I burned ~$400k of Codex tokens and got nowhere. Burned ~$20k of Opus and got there in 2 weeks.
The numbers are the story. By his account he burned roughly $400k of Codex tokens and got nowhere, then burned roughly $20k of Opus and got there in two weeks. In a follow-up he put that Opus spend at about ten weeks of usage on the $200 Claude subscription, which is a different way of saying the same thing and a reminder that the sticker price and the subscription price are not the same economy. This is the same port he was earlier talking about finishing.
What he claims it does
Theo lists the reasons he likes the implementation over alternatives. It is a drop-in replacement for tsc, he claims 100% compatibility, it is fully wasm-ready, and the effect-ts modifications are built in. He also says Bun's `bun check` dropped the same night, that Jarred shared numbers with him early, that it is incredibly impressive, and that it is probably the right choice for most apps using Bun. tsc-rs is only faster, he says, if you are using the Effect ts checks. He later noticed `bun check` is missing incremental checks and amended that tsc-rs might actually be the best drop-in option right now.
His own sign-off was "Try this out and lmk how broken it is." Nobody outside has run it at scale yet.
For working engineers, the useful datum here is not the total spend, it is the ratio between two models on one long-running task, reported by one person on one project. It is an anecdote, not a benchmark. Theo also posted that Opus took the porting brief seriously enough to port most of the Go standard library into Rust along the way.