jmtrs

An Anthropic engineer just rewrote a million line codebase into another language in eleven days by himself, then published the entire method. Rewrites are the least of what it is good for Jarred Sumner works at Anthropic and created Bun. He ported it from Zig to Rust with 64 Claudes running at once. 535,496 lines, 1,448 files, merged with 100% of the existing test suite green on all six platforms and zero tests skipped. He calls them dynamic workflows. It is a graph: named nodes, state on disk, agents running inside boundaries he drew. Every time output came back wrong, he edited the workflow instead of patching files. Then he wrote all of it down. The false starts, the prompts, the rules he added mid run. Full playbook in the comments. What that looks like when you build the graph: 1. Give every node one job and a file to read. His agents each did one thing: port, fix errors, review, apply. The rulebook file is the shared state they all start from, not the chat history. 2. Keep state on disk, not in context. The work queue was the filesystem. Kill the run at 60 percent, restart, and it resumes at 60 percent because the disk remembers. 3. Make review its own node. One agent works, two review with nothing but the result, told to assume it is wrong. A reviewer sharing the writer's context always agrees with the writer. 4. Push slow operations out of the loop. He banned cargo and git from inside it, ran the compiler once across everything, then fanned agents out on the error list. Check frequency should match check cost. 5. Isolate parallel branches. His agents collided until he split them across four worktrees, 16 each. Parallelism needs separate ground to stand on. Your instinct will be to fix the file in front of you. Fix the sentence in the rules that let it through, and the next hundred files come back right. Bookmark this