Build a C compiler with a team of parallel agents with Claude
Anthropic's engineering write-up on tasking Opus 4.6 agent teams with building a C compiler.
Done with Claude Code
What they did
Nicholas Carlini ran 16 Claude agents in an endless loop, each in its own Docker container, pushing to a shared git repo. Agents claimed tasks by writing lock files, merged each other's work, and had no orchestrator. Carlini's main work was building tests, CI, and a GCC-based oracle so agents could fix different kernel bugs in parallel.
How it went
About 2,000 sessions produced a 100,000-line Rust compiler that builds Linux 6.9 on x86, ARM and RISC-V and passes 99% of most test suites. It still calls GCC for 16-bit x86, its assembler and linker are buggy, and its output is inefficient.
Worth knowing
It cost just under $20,000 in API fees over two weeks, and the quality of the test harness decided whether agents stayed on track. Run it in a container.
Try it yourself with Claude Code
I want to build a small [tool, e.g. a Markdown-to-HTML converter in Python] from scratch with a spec-first approach. First write a short spec and a test suite in this folder, then split the work into independent pieces and use sub-agents to implement them in parallel. Stop when all tests pass, and give me a summary of what each sub-agent built and any tests you had to skip.
Source
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