The bug was in my beliefs, not my code

Short summary

A developer competing in ARC Prize 2026 discovered their AI agent's persistent underperformance wasn't caused by unreachable bugs in hidden test games, but by two false assumptions they had recorded as settled conclusions and then used as permission to stop investigating. Once they probed the real code and data instead of trusting their own notes, both beliefs collapsed within an hour and the problem became trivially reproducible. The core lesson: the most expensive mistake in any project is reasoning forward from an unverified belief — especially one that says "we can't, because" — since it ends investigation before it starts.

• •Author's AI agent was underperforming on hidden ARC Prize 2026 tests; two recorded assumptions about why were both wrong
• •Testing actual code and data instead of trusting notes revealed the problem was easily reproducible locally
• •Key takeaway: distrust any claim that ends investigation — re-derive beliefs from reality, not from your last summary of it

Generated with AI, which can make mistakes.