Cloudflare and VoidZero Take On tsrs, a Rust Port of the TypeScript Compiler

Cloudflare and VoidZero are taking on tsrs, an experimental port of the TypeScript compiler to Rust, and will develop it as part of the Oxc JavaScript compiler toolchain, Cloudflare said in a blog post on October 20, 2026. The companies are working with Max Schwenk of Owner.com, who started the port, and said the work is happening “in close collaboration with the TypeScript team.”

Cloudflare’s post, written by Boshen Chen, Dimitri Mitropoulos and Christoph Nakazawa, said early benchmarks show tsrs running up to 8x faster than TypeScript 7.0 and using about 70% less memory when both run the same number of type-check workers. The authors said the TypeScript 7.1 beta is itself up to 2.5x faster than 7.0, and that some of those optimizations were upstreamed from tsrs.

“To be clear, we are not forking TypeScript,” the authors wrote, adding that the TypeScript team should remain in full control of the language’s design and direction. A port has to follow upstream decisions closely, they said, “or it will eventually fall apart and become incompatible.”

Why a Second Native Compiler

Microsoft’s TypeScript team already moved the compiler from JavaScript to Go, a port Cloudflare said made TypeScript 10x faster and far more memory efficient. Cloudflare’s case for Rust centers on WebAssembly. Compiling a Go program to Wasm means shipping Go’s garbage collector along with it, the post said, while Rust’s memory model allows simpler interactions between a WebAssembly guest and host.

Cloudflare tied that to its own platform, saying a small memory footprint lets full development toolchains run in sandboxed environments on Cloudflare Workers, and with Wasm, in a browser, on an embedded device or in an IoT application. It said more than 10 million developers build on its platform and that it plans to try deeper tsrs integrations, such as type-aware lint rules in Oxlint.

The project’s GitHub repository, now under the oxc-project organization, describes tsrs as a drop-in replacement for the TypeScript 7 compiler and language server. The maintainers say they aim to release a stable version against TypeScript 7.1 with 100% conformance. The –init and –showConfig commands are not supported yet, and pull requests are closed for now because the team says it lacks the bandwidth to review them. The license notice says tsrs is a derivative of TypeScript under Apache-2.0 and is “Not affiliated with or endorsed by Microsoft.”

An Agent-Written Port

Schwenk, Owner’s head of AI developer experience, described the project’s origin in an October 19, 2026 post on Owner’s engineering blog. Owner’s backend monolith, about 37,000 TypeScript files checked as one program, needed 19 GiB of memory and 80 seconds for a single-threaded check on TypeScript 7.0. He said he asked Anthropic’s Claude Opus 5.5 for a faithful port of the Go compiler to Rust and “wrote zero code.”

The port was tested against the 15,197 conformance cases left behind by TypeScript’s JavaScript-to-Go migration. After a type printer was added, 99.97% of error baselines matched, which Schwenk put at all but four of 13,462. Owner now runs tsrs across its monorepo, with type checks taking seven seconds in CI and about twelve on a MacBook. Across a suite of 17 public projects, he wrote, tsrs uses about 3x less memory and runs 2.5 to 5x faster than the TypeScript nightly build, numbers he said “move as everyone keeps shipping.”

Cloudflare said it is also working with Theo Browne to merge his separate Rust port, tsc-rs, with tsrs into one package that supports all of TypeScript’s features, including Language Server Protocol support. Developers can install the experimental release now from npm, and the authors said they aim to reduce remaining differences from upstream TypeScript, such as the order in which diagnostics print, before a stable release.