{"abstract":"The operation returns a result or retained state that violates this contract: Return whether right is a positional suffix of left, with empty right always matching.","category":"Collection algebra","checks":5,"contract":"Return whether right is a positional suffix of left, with empty right always matching. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","contract_signature":"x, y=None","evaluation_group":"model-900802f5cbbc02d4","failed_approach":"Prefix comparison checks the opposite boundary.","family":"xr-suffix-empty-identity","id":"FA-4301","implementations":{"attempt":{"sha256":"2416145d3bd186775e7405b80d397607709b8209988dc24d6c9155e0c356322b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return x[:len(y)]==y\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('both empty', solve([], []), True)\ncheck('empty right operand', solve(['a'], []), True)\ncheck('empty left operand', solve([], ['b']), False)\ncheck('overlap and multiplicity', solve(['b', 'a', 'b'], ['b', 'c', 'c']), False)\ncheck('nonprefix suffix matches', solve(['b','a'], ['a']), True)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"5d497f987680f5c06970d7872cd70326266e8d3b43ae2b202c6621657552a7ef","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return x[-len(y):]==y\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('both empty', solve([], []), True)\ncheck('empty right operand', solve(['a'], []), True)\ncheck('empty left operand', solve([], ['b']), False)\ncheck('overlap and multiplicity', solve(['b', 'a', 'b'], ['b', 'c', 'c']), False)\ncheck('nonprefix suffix matches', solve(['b','a'], ['a']), True)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":" This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"xr-suffix-empty-identity","generated_at":"2026-09-29T14:37:37.702484+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A controlled local-runtime regression for collection APIs, language semantics, or ownership wrappers. Fixtures include boundary and interaction cases.","root_cause":"Negative-zero slicing selects the full sequence instead of the empty suffix.","sha256":"aa415cdb0e57d7ca6b52ef3009ed8e260b770e0ef81e16f994dccd241dc068fd","title":"Suffix empty identity · case 01","variant":1,"variant_policy":"Five execution reruns of a fixed adversarial fixture suite; variant number does not alter semantic inputs.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":36.467,"exit_code":1,"observations":[{"actual":true,"check":"both empty","expected":true,"passed":true},{"actual":true,"check":"empty right operand","expected":true,"passed":true},{"actual":false,"check":"empty left operand","expected":false,"passed":true},{"actual":false,"check":"overlap and multiplicity","expected":false,"passed":true},{"actual":false,"check":"nonprefix suffix matches","expected":true,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"both empty\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"empty right operand\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"empty left operand\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"overlap and multiplicity\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"nonprefix suffix matches\", \"actual\": false, \"expected\": true, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.777,"exit_code":1,"observations":[{"actual":true,"check":"both empty","expected":true,"passed":true},{"actual":false,"check":"empty right operand","expected":true,"passed":false},{"actual":false,"check":"empty left operand","expected":false,"passed":true},{"actual":false,"check":"overlap and multiplicity","expected":false,"passed":true},{"actual":true,"check":"nonprefix suffix matches","expected":true,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"both empty\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"empty right operand\", \"actual\": false, \"expected\": true, \"passed\": false}, {\"check\": \"empty left operand\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"overlap and multiplicity\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"nonprefix suffix matches\", \"actual\": true, \"expected\": true, \"passed\": true}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}