Your agent passes every test you wrote, because every test assumes the world behaves. Production does not: tools return wrong data, and some users push the agent on purpose. Two kinds of trouble, and you need both. Bad luck is chaos: a weather tool returns 12 degrees for Miami in June and the agent reports it as fact. A guardrail that range-checks the value the moment a tool returns catches it. Bad intent is red teaming: an attacker escalates over several turns until the agent leaks a stored card number. You generate these multi-turn attacks instead of scripting them, then score whether the agent held. Both are stochastic: run them many times and you get a correctness rate and a breach rate, not a single pass.

Outline: • The happy-path trap • Bad luck: chaos testing • Bad intent: red teaming • One run is not a measurement • Test both before you ship