Each recorded case starts with Alice at ten thousand cents, Bob at two thousand five hundred, and no transfer rows. The contract specifies five rejections and two successes. This is a fictional teaching fixture calling real SQLite functions. Its rejection rule requires the exact response, unchanged account and transfer rows, and no open transaction.

The baseline returns unknown destination for a two thousand cent request to ghost. It has already committed Alice's debit. After the connection closes and reopens, Alice has eight thousand cents, Bob still has two thousand five hundred, and no transfer row exists. The response matches; the durable state fails.

The second failure uses an internal test-only seam, not a caller-controlled field. After a real debit, a zero-amount transfer insert triggers a real CHECK constraint error. The failing statement aborts, but the baseline's earlier debit remains committed. The same forbidden balances survive reconnecting. This does not demonstrate attacker reachability.

The implemented correction begins an explicit transaction and checks the destination before debiting. For the injected constraint error, the trace shows a temporary debit inside the transaction, followed by explicit rollback. A fresh connection sees the original balances and no transfer row. The corrected gate checking response and effects passes all seven selected cases.

The independent observer compares literal expected account and transfer rows, not just the balance sum. The two successful controls also reject a handler that refuses every request. Four gates perform twenty-three calls across seven scenarios. Wrapper success means the expected passing and failing children reproduced, not that the baseline became acceptable.

For your own operation, copy the worksheet and agree the rejection owner, allowed effects and forbidden effects before running it. Keep the request, revision, raw observations and next decision together. That work is proposed. Authorization, retries, concurrency, crash recovery and notification delivery were not exercised by this teaching fixture.