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, buried in junk, and the agent reports it as fact while paying tokens to read the noise. A guardrail that range-checks the value the moment a tool returns catches it, fixing accuracy and cost at once. Bad intent is red teaming. An attacker escalates over several turns until the agent leaks a stored card number or books above its limit. You generate these multi-turn attacks instead of scripting them, then score whether the agent held. Both are stochastic: run them once and you learn little, run them many times and you get the real picture, 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