fcoreutils: Claude Code autonomously rewrites GNU coreutils in Rust - up to 54x faster, 100% compatible. We gave Claude Code a small Linux machine with full sudo access, defined one goal (rewrite GNU coreutils with 100% compatibility and 10x-30x performance), and walked away. Zero human-written code. Claude Code consumed the full $500 API credit in 3 days + another 3 days Claude Max 20 - autonomously designing architecture, implementing 10 SIMD-accelerated tools, publishing 62+ releases to crates.io, and passing 826/826 compatibility tests. Results (independently verified via GitHub Actions): - wc: 54.3x faster than GNU, 28.6x faster than uutils/coreutils - sort: 18.1x faster than GNU, 15.1x faster than uutils - uniq: 13.4x faster than GNU - base64: 8.8x faster than GNU - cut/tr/tac: 5-7x faster than GNU Key: Claude Code didn't just match uutils/coreutils - it surpassed it across every tool. A single autonomous AI agent outperforming a major community-maintained Rust project.
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