{"abstract":"The operation returns a result or retained state that violates this contract: Return indices whose element differs from its predecessor; position zero is not a change.","category":"Sequence semantics","checks":4,"contract":"Return indices whose element differs from its predecessor; position zero is not a change. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","evaluation_group":"model-079a696e39f03dec","failed_approach":"Global novelty is substituted for inequality with the immediate predecessor.","family":"xr-adjacent-change-positions","id":"FA-4206","implementations":{"attempt":{"sha256":"c8560607970381c79f76d5f1acdb772ef2ff8b900b7625b9811b0ea470791356","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return [i for i in range(1,len(x)) if x[i] not in x[:i]]\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']), [1])\ncheck('nonadjacent duplicate and unsorted order', solve(['b', 'a', 'b', 'c']), [1, 2, 3])\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":"c5f30fd5e4ab1f55aee92270c15ac5018cdc79770a9336d32fdcac09113f2a43","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return [i for i in range(len(x)) if i==0 or x[i]!=x[i-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']), [1])\ncheck('nonadjacent duplicate and unsorted order', solve(['b', 'a', 'b', 'c']), [1, 2, 3])\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":"4309ca506fc0eac21a2ffe32b21037680d6e3cdb9551b870a66b2e961d4a462b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return [i for i in range(1,len(x)) if x[i]!=x[i-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']), [1])\ncheck('nonadjacent duplicate and unsorted order', solve(['b', 'a', 'b', 'c']), [1, 2, 3])\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-adjacent-change-positions","generated_at":"2026-09-29T14:37:36.943332+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":"Return indices whose element differs from its predecessor; position zero is not a change.","root_cause":"The first element is incorrectly counted as a change without a predecessor.","sha256":"b7bbb891a2936866ee84503009e00fe428ae3387abf01a85df124f85aef86cb3","title":"Adjacent change positions · 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":39.407,"exit_code":1,"observations":[{"actual":[],"check":"empty collection","expected":[],"passed":true},{"actual":[],"check":"singleton collection","expected":[],"passed":true},{"actual":[1],"check":"two distinct elements","expected":[1],"passed":true},{"actual":[1,3],"check":"nonadjacent duplicate and unsorted order","expected":[1,2,3],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"empty collection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton collection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"two distinct elements\", \"actual\": [1], \"expected\": [1], \"passed\": true}, {\"check\": \"nonadjacent duplicate and unsorted order\", \"actual\": [1, 3], \"expected\": [1, 2, 3], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":38.696,"exit_code":1,"observations":[{"actual":[],"check":"empty collection","expected":[],"passed":true},{"actual":[0],"check":"singleton collection","expected":[],"passed":false},{"actual":[0,1],"check":"two distinct elements","expected":[1],"passed":false},{"actual":[0,1,2,3],"check":"nonadjacent duplicate and unsorted order","expected":[1,2,3],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"empty collection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton collection\", \"actual\": [0], \"expected\": [], \"passed\": false}, {\"check\": \"two distinct elements\", \"actual\": [0, 1], \"expected\": [1], \"passed\": false}, {\"check\": \"nonadjacent duplicate and unsorted order\", \"actual\": [0, 1, 2, 3], \"expected\": [1, 2, 3], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":36.229,"exit_code":0,"observations":[{"actual":[],"check":"empty collection","expected":[],"passed":true},{"actual":[],"check":"singleton collection","expected":[],"passed":true},{"actual":[1],"check":"two distinct elements","expected":[1],"passed":true},{"actual":[1,2,3],"check":"nonadjacent duplicate and unsorted order","expected":[1,2,3],"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\": [1], \"expected\": [1], \"passed\": true}, {\"check\": \"nonadjacent duplicate and unsorted order\", \"actual\": [1, 2, 3], \"expected\": [1, 2, 3], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}