empty           empty/null/zero-length input or collection
stale           cached / outdated state read after the source changed
loading         partially-loaded UI or partial response
retry           idempotency, dedup, exponential backoff
permission      role/scope mismatch, IDOR, mass assignment
concurrency     two writers, lost update, race
rollback        compensating action on partial failure
integration     dependency timeout / 5xx / contract drift
overflow        bounds, big payloads, pagination
state-skip      transition from unexpected state
