Claude Opus 5.5 ported the TypeScript compiler to Rust for $24k
Theo Browne published tsc-rs, a Rust port of Microsoft's TypeScript 7 compiler written in full by Claude Opus 5.5 over two weeks for about $24,047 in API-priced tokens, after GPT models had spent more than $400,000 on an earlier attempt that never finished the job.
Image: GitHub
Why it mattersOne developer paid Opus 5.5 $24,047 to port a Microsoft codebase in two weeks, which is a usable measurement of what a parity-port job costs today.
A developer paid a language model about $24,047 to port Microsoft's TypeScript compiler to Rust, and the result passes all 181,711 of upstream's tests. Theo Browne of Ping (pingdotgg) published the project, tsc-rs, under the MIT licence this week. The Hacker News discussion reached 106 points overnight and the repository had 664 stars at the time of writing.
The port is of microsoft/TypeScript at revision 673a5f17d713, a late-September build of TypeScript 7.1.0-dev. That codebase is the native TypeScript compiler Microsoft is writing in Go, not the older Ruby or JavaScript ones. The Rust version keeps the Go algorithms and command line and ships as an npm package called tsc-rs that works as a drop-in replacement in the projects the author tested.
What the numbers look like
The author ran a timed benchmark against VS Code's 3.75 million lines of TypeScript. Checking took 54.56 seconds under tsc 6 (the JavaScript compiler), 6.84 seconds under tsc 7 (the Go compiler), and 4.20 seconds under tsc-rs. Across six open-source apps the geometric mean put tsc-rs at 20.9 times tsc 6 and 1.61 times tsc 7. The runs were taken on an Apple M4 Pro, median of five with hyperfine, with --noEmit --incremental false.
The author also reports the type-check time on 60 open-source projects at about half of Go's, geometric mean, and says the tsc-rs preview packages ship without profile-guided optimisation or BOLT, so they are slower than that measured build.
What it cost, in the author's own words
Theo first tried OpenAI's models. "They wrote over 1.3m lines of Rust over multiple months of /goal loops and never got past like 84% compat," he writes, and he puts the API-priced total above $400,000. He then gave the same job to Claude Opus 5.5 on his Claude Max plan. By his account Opus started from scratch, had a working first version in 10 hours, and finished a complete port in two weeks for API-priced spend of about $24,047. The run used "somewhere between 925% and 983% of my $200 plan weekly limits" on his Claude accounts.
He also says, in bold at the top of the README, "I've never read a line of this code." Everything below a line labelled "The Slop Line" was written by the model, which includes the install guide, the status section, the compatibility notes and the four benchmark tables.
What the author admits it still gets wrong
The port is pinned to one upstream revision and compared against Go at the same revision, so a reader cannot generalise the compatibility claim to a different TypeScript version. In some monorepos tsc-rs writes output for more workspace files than tsc and reports TS6059. In tsc -b, when one project imports another without a project reference, tsc-rs can read the stale or missing output in a few shapes of config where tsc reads the fresh one. The project ships binaries for Linux x64 and macOS arm64 only. Windows and Linux arm64 are not available yet.
A reader who wants to try it today has a parity benchmark that fails below set multipliers and a repository with every input and script a reviewer would need to repeat the measurements on their own machine.
Source
- Project: pingdotgg/ts-rust on GitHub
- Discussion: Hacker News
This item was written by an AI system from the linked source. Reveneau is responsible for what it publishes.
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