Developers talk about bugs in systems, but rarely about the bugs in ourselves -- the mental shortcuts, biases, and perception gaps that silently shape how we write and review code. In this talk, we’ll explore the cognitive failures I’ve seen across engineering teams: premature certainty, invisible assumptions, pattern-matching gone wrong, and the “I swear I read that line” illusion. We’ll map how these human bugs create security holes, bad architecture, and debugging rabbit holes. Then we’ll look at practical ways to compensate for them using lightweight rituals, tooling, and intentional checks that catch errors your brain won’t. It’s a mix of psychology, engineering, and a little humour -- with examples that every developer will recognise.