{"abstract":"The operation returns a result or retained state that violates this contract: Emit overlapping adjacent pairs, omitting an incomplete singleton.","category":"Sequence semantics","checks":4,"contract":"Emit overlapping adjacent pairs, omitting an incomplete singleton. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","evaluation_group":"model-2247df1e8d59a3a6","failed_approach":"Wrapping the final element back to the first creates a nonexistent neighbor pair.","family":"xr-pairwise-neighbors-overlap","id":"FA-4171","implementations":{"attempt":{"sha256":"a2d727123219cd81dfc3b4b0b0b66174a7af176bca8332828e9d1d1dfef86292","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return [[x[i],x[(i+1)%len(x)]] for i in range(len(x))]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('empty collection', solve([]), [])\ncheck('singleton collection', solve(['a']), [])\ncheck('two distinct elements', solve(['a', 'b']), [['a', 'b']])\ncheck('nonadjacent duplicate and unsorted order', solve(['b', 'a', 'b', 'c']), [['b', 'a'], ['a', 'b'], ['b', 'c']])\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":"373d1c2d9319b1e0dd492d5e41cbdcc0bb5f12502e767794a4b005933114f6c3","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return [x[i:i+2] for i in range(0,len(x),2)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('empty collection', solve([]), [])\ncheck('singleton collection', solve(['a']), [])\ncheck('two distinct elements', solve(['a', 'b']), [['a', 'b']])\ncheck('nonadjacent duplicate and unsorted order', solve(['b', 'a', 'b', 'c']), [['b', 'a'], ['a', 'b'], ['b', 'c']])\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"},"fixed":{"sha256":"d077153d9b10aee06d7c018909871a456fad90d4f71241445878b8414d7b1931","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return [[x[i],x[i+1]] for i in range(len(x)-1)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('empty collection', solve([]), [])\ncheck('singleton collection', solve(['a']), [])\ncheck('two distinct elements', solve(['a', 'b']), [['a', 'b']])\ncheck('nonadjacent duplicate and unsorted order', solve(['b', 'a', 'b', 'c']), [['b', 'a'], ['a', 'b'], ['b', 'c']])\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-pairwise-neighbors-overlap","generated_at":"2026-09-29T14:37:36.471372+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.","repair":"Emit overlapping adjacent pairs, omitting an incomplete singleton.","root_cause":"Nonoverlapping chunks skip adjacent pairs that cross chunk boundaries.","sha256":"a1ed16b49323344baa1a9900b609d2d982b8765af957cd4b5e42d5dc1ed4776d","title":"Pairwise neighbors overlap · case 01","variant":1,"variant_policy":"Five execution reruns of a fixed adversarial fixture suite; variant number does not alter semantic inputs.","verification":{"attempt":{"elapsed_ms":126.458,"exit_code":1,"observations":[{"actual":[],"check":"empty collection","expected":[],"passed":true},{"actual":[["a","a"]],"check":"singleton collection","expected":[],"passed":false},{"actual":[["a","b"],["b","a"]],"check":"two distinct elements","expected":[["a","b"]],"passed":false},{"actual":[["b","a"],["a","b"],["b","c"],["c","b"]],"check":"nonadjacent duplicate and unsorted order","expected":[["b","a"],["a","b"],["b","c"]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"empty collection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton collection\", \"actual\": [[\"a\", \"a\"]], \"expected\": [], \"passed\": false}, {\"check\": \"two distinct elements\", \"actual\": [[\"a\", \"b\"], [\"b\", \"a\"]], \"expected\": [[\"a\", \"b\"]], \"passed\": false}, {\"check\": \"nonadjacent duplicate and unsorted order\", \"actual\": [[\"b\", \"a\"], [\"a\", \"b\"], [\"b\", \"c\"], [\"c\", \"b\"]], \"expected\": [[\"b\", \"a\"], [\"a\", \"b\"], [\"b\", \"c\"]], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.931,"exit_code":1,"observations":[{"actual":[],"check":"empty collection","expected":[],"passed":true},{"actual":[["a"]],"check":"singleton collection","expected":[],"passed":false},{"actual":[["a","b"]],"check":"two distinct elements","expected":[["a","b"]],"passed":true},{"actual":[["b","a"],["b","c"]],"check":"nonadjacent duplicate and unsorted order","expected":[["b","a"],["a","b"],["b","c"]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"empty collection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton collection\", \"actual\": [[\"a\"]], \"expected\": [], \"passed\": false}, {\"check\": \"two distinct elements\", \"actual\": [[\"a\", \"b\"]], \"expected\": [[\"a\", \"b\"]], \"passed\": true}, {\"check\": \"nonadjacent duplicate and unsorted order\", \"actual\": [[\"b\", \"a\"], [\"b\", \"c\"]], \"expected\": [[\"b\", \"a\"], [\"a\", \"b\"], [\"b\", \"c\"]], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":42.297,"exit_code":0,"observations":[{"actual":[],"check":"empty collection","expected":[],"passed":true},{"actual":[],"check":"singleton collection","expected":[],"passed":true},{"actual":[["a","b"]],"check":"two distinct elements","expected":[["a","b"]],"passed":true},{"actual":[["b","a"],["a","b"],["b","c"]],"check":"nonadjacent duplicate and unsorted order","expected":[["b","a"],["a","b"],["b","c"]],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"empty collection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton collection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"two distinct elements\", \"actual\": [[\"a\", \"b\"]], \"expected\": [[\"a\", \"b\"]], \"passed\": true}, {\"check\": \"nonadjacent duplicate and unsorted order\", \"actual\": [[\"b\", \"a\"], [\"a\", \"b\"], [\"b\", \"c\"]], \"expected\": [[\"b\", \"a\"], [\"a\", \"b\"], [\"b\", \"c\"]], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}