Zero Defect

This puts Claude into a strict operational mode for work where you absolutely cannot afford mistakes: production deployments, financial logic, security code. It enforces eight precision rules like "read before writing" and "verify before claiming," plus a pre-commit gate that requires you to actually run tests and confirm imports before saying anything is done. The anti-pattern table is especially useful, calling out things like editing without re-reading files or assuming APIs exist because they sound right. It's heavy-handed by design, trading speed for accuracy. If you're prototyping or exploring, you'll find it frustrating. But when the stakes are high and a hallucinated function name could break production, the discipline is worth it.