behavior-characterizationlisted

# Behavior Characterization Detect what the system does today without judging whether it is ideal. ## Observable signals - Return values. - Exceptions and error codes. - Side effects and state changes. - Persistence writes/reads. - Published events. - Relevant logs. - External calls. - Edge conditions and branch behavior. - Implicit business rules. Every behavior claim needs code evidence or must be marked as a hypothesis. ## Characterization method - Write an assertion expected to fail, run it, and read the actual value from the failure message; anchor that value as the expected result. The test documents what the code does, not what it should do. - Characterize only the zone the plan will touch (targeted characterization), not the whole unit by default. ## Bugs found while characterizing Characterize the bug as-is: the test anchors today's wrong output. Never fix it in the same step — record it, finish the safety net, and schedule the fix as a follow-up behavior change to run with the net in place.