Developer Rewrites Pi Coding Assistant in Rust for Major Performance Boosts

On November 2, 2026 at 23:53, a developer posted on V2EX about pi-rust, a personal project that rewrites the Pi coding assistant in Rust. The rewritten command-line tool is called rpi. According to the author, rpi improves both performance and content footprint compared with the original, though no quantified figures are given in the post.

The developer explains the motivation as twofold: a desire to learn Rust and the wish to find a project worth maintaining long term. An agent, the author notes, has to handle async requests, streaming output, file operations, and state management, with terminal UI and plugins still to come. These demands force practical decisions about how to share state, propagate errors upward, cancel async tasks, and split interfaces. Pi was chosen as the rewrite target precisely because a TypeScript implementation already exists to serve as reference: when implementing a feature, the author can first see how the original does it, then work out the Rust version, and compare the two afterward instead of judging correctness by imagination alone.

The post also outlines the mechanics the author had to work through while building a full agent, such as who executes a tool call once the model returns it, what result should be fed back to the model when a tool errors, what happens if a user cancels mid-stream while a message is still being delivered, and what state the history should resume with after an interruption. These issues rarely surface when simply calling a chat API but are unavoidable in a complete agent. At the time of the post, the project is at the stage of a freshly published announcement describing motivation and implementation approach.