/ lab · OPBR canonical · interactive

Same correct refund. Two different paths.

An AI agent processes a €1,200 refund. In both runs the final JSON is identical: correct amount, correct customer, all provenance fields populated, fraud_check_passed: true. The output evaluator passes both runs. The behavior contract passes one and fails the other. The difference lives in the order in which things happened. This is the canonical shape of output-passing behavioral regression.

P2Violation detected. Side effect refund_commit precedes precondition check fraud_check. The agent committed the refund before confirming the policy allowed it.
output PASS
behavior FAIL
clause P2
violating fraud_check
Try it. Grab refund_commit in Run B and drag it down past fraud_check. The bracket retracts as you cross each precondition. The verdict flips from FAIL to PASS. The prose above rewrites itself. The URL updates so the state is shareable. Drag back up — the violation returns. Keyboard: focus the row, use / to reorder one step at a time.