Pi from Scratch rebuilds an agent in 765 lines

Pi from Scratch rebuilds a working TypeScript coding agent in 765 source lines across five files, with another 401 lines of tests covering the loop, tools, CLI, LLM client, and terminal UI. The MIT-licensed repository and interactive trace tutorial were published inside the last 24 hours and expose read, edit, and shell tools behind an OpenAI-compatible API. For builders deciding what belongs in the harness rather than the model, this compact implementation is a useful foil to the five-task performance swing measured across coding-agent harnesses: study the loop before adding orchestration layers.