X_CONTRACT_DEFECT
Means
a generated legal input made a handler fail
Typical cause
the contract step's exercise assertion called the handler with input its own schema accepts, and it threw an uncoded error, failed its output schema, or answered a coded 5xx; meta.run and meta.input name the run
Fix
fix the handler or tighten input:, then replay the exact run: bun test <file> -t '<name>: handler survives generated input' (the seed is the action name)