A researcher used 16 instances of the language model Opus 4.6 to build a C compiler from scratch, with the goal of testing the limits of autonomous software development. The compiler, written in Rust, can build Linux 6.9 on x86, ARM, and RISC-V, but has limitations such as inefficient generated code and lack of a 16-bit x86 compiler. The project required nearly 2,000 Claude Code sessions and $20,000 in API costs. The resulting compiler is a significant achievement, but its quality and maintainability are debated.