I benchmarked 4 coding agents on an NP-hard problem I solved 8 years ago

I gave an unpublished fiber network optimization problem to Claude Code, Codex, Gemini CLI, and Mistral. The score is total fiber length (lower is better). A good human solution in 30 minutes: ~40,000. My best after days of C++: 34,123. Given one hour, Claude Code hit 34,061 — beating me by 62 points. A 7-word prompt hint improved every agent by 18-30%. About 15% of all trials produced completely invalid outputs.