Every developer has spent hours debugging a problem only to discover the issue was obvious in hindsight. The root cause often isn’t technical—it’s cognitive. This talk explores the mental shortcuts and perception gaps that silently shape how we write and interpret code: pattern-matching errors, false certainty, invisible assumptions, and the “I swear I read that line” illusion. We’ll map these human bugs to the production defects they create—misread logs, bad merges, faulty architecture decisions, and subtle regressions. Then we’ll explore ways to compensate using engineering habits: structured review patterns, slow-thinking triggers, sanity-check prompts, and workflow design that protects you from your own mind. A mix of psychology, debugging, and uncomfortable relatability.