Evaluating Claude’s C Compiler Against GCC Anthropic recently announced that 16 instances of Claude Opus 4.6, running in parallel as autonomous agents, built a C compiler from scratch. Over nearly 2,000 Claude Code sessions across two weeks, at $20,000 in API costs, the agents produced a 100,000-line Rust codebase. A clean-room implementation with no internet access, depending only on the Rust…