Five teams in the Rust project have adopted a policy governing the use of Large Language Models (LLMs) for contributions to the rust-lang/rust monorepo. The policy is intended for a specific purpose and does not represent an official stance on LLMs across the entire Rust project.

Bun is undergoing a rewrite in Rust, which aims to leverage AI capabilities for the work typically done by open-source maintainers. Anthropic's AI tools, including a C compiler, are contributing to this rewrite process.

ast-grep rewrote Tree-sitter's C core in Rust, resulting in a 30% increase in parser speed and a 22% improvement in overall performance for ast-grep. The new core enhances parsing efficiency and accelerates tree reading.

Claude Code v2.1.181 and later utilize the Rust port of Bun, resulting in a 10% faster startup on Linux. The command `strings ~/.local/bin/claude | grep -m1 'Bun v1'` confirms the use of Bun v1.4.0 on macOS.

Roc's compiler team has rewritten 300,000 lines of Rust code into Zig over the past year and a half. The project has achieved feature parity with the original Rust compiler.

Bun is being rewritten in Rust to improve performance and maintainability. Jarred's early involvement in the Zig community showcased his experimental approach to problem-solving, contributing to his growth as an engineer.

pgrust is a rewrite of Postgres in Rust that achieves 100% compatibility with Postgres 18.3, passing over 46,000 regression tests. It maintains disk compatibility with Postgres and can boot from an existing Postgres 18.3 data directory, aiming to facilitate internal changes while preserving the original behavior and using AI-assisted programming.

Prylint is a Rust reimplementation of pylint that delivers byte-for-byte identical output while being 15 to 2300 times faster, with a median speed increase of approximately 85 times. It maintains the same error messages, line and column references, text order, exit codes, and footer as the original pylint.

React Compiler is being ported to Rust as an experimental project. The port is in progress, with all fixtures passing but potential unknown bugs, and no builds are currently available for testing.

Grit is a project aimed at rewriting Git in Rust, focusing on creating a library-based architecture. The initiative draws inspiration from Anthropic's experiment with agents generating a functioning C compiler.