Cloudflare and VoidZero have published tsrs, an experimental Rust reimplementation of the TypeScript compiler built almost entirely through AI-directed coding rather than manual programming. Early benchmarks show sharp gains in speed and memory use against TypeScript 7.0, though the project still lacks core developer tooling and full compatibility with existing workflows.
An AI-driven translation, not a human rewrite
The project took shape inside the Oxc toolchain through work by Max Schwenk of Owner.com, alongside the TypeScript team. Schwenk says he wrote no code himself; instead he directed AI agents, led by Claude Opus 5.5, to translate the existing compiler into Rust. The agents used TypeScript's own suite of 15,197 conformance tests as their specification, and the resulting project tracks the upcoming TypeScript 7 release. Cloudflare has been careful to describe tsrs as a port built in cooperation with Microsoft's TypeScript team, not an independent fork - the team retains control over the language's design.
Performance claims and their limits
Measured against TypeScript 7.0 at matching checker worker counts, tsrs reports up to eight times faster type checking and about 70% lower memory use. On Owner.com's 37,000-file codebase, a check that took 80 seconds and 19 GiB of memory under TypeScript 7.0 finished in seven seconds with tsrs. A separate developer benchmark found a 5.3-times speedup with 72% less memory and identical diagnostic output. However, comparing tsrs against the newer TypeScript 7.1 beta - rather than 7.0 - narrowed the gap to roughly 2.7 times, since Microsoft has already folded some of the same optimizations into its own compiler. Daniel Rosenwasser of the TypeScript team noted that part of the speedup comes from algorithmic improvements rather than the switch to Rust alone, some of which are now feeding back into TypeScript itself.
Compatibility gaps and a crowded field
The build is explicitly experimental. It has no watch mode, no language server, and does not support flags such as --init or --showConfig. Diagnostic ordering can differ from the standard compiler, and testers found tsrs exits with code 2 on type errors instead of tsc's code 1 - a mismatch that can break continuous-integration scripts. Rust compilation also enables a WebAssembly build, @tsrs/wasm, letting checks run in browsers or on Cloudflare Workers without bundling a garbage collector, unlike Microsoft's Go-based tsgo compiler. Cloudflare says it plans to merge tsrs with Theo Browne's separate Rust port, tsc-rs, rather than compete, and to add language-server support later. Because tsrs currently tracks TypeScript 7, teams still on TypeScript 5 or 6 are advised to adopt Microsoft's Go-based compiler first before trying tsrs with the same configuration file. The project is released under the Apache-2.0 license and available through GitHub and npm.