{"abstract":"The operation returns a result or retained state that violates this contract: Collapse adjacent equal values only; separated repetitions remain.","category":"Sequence semantics","checks":5,"contract":"Collapse adjacent equal values only; separated repetitions remain. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","evaluation_group":"model-7a785f64638790d4","failed_approach":"Sorting and deduplicating both destroys run order and merges separate runs.","family":"xr-adjacent-run-collapse","id":"FA-4096","implementations":{"attempt":{"sha256":"10f4b7b38e3475044b0b5e2a1243b452d5ba246f26b11b6871ec26dba45f7326","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return sorted(set(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']), ['a'])\ncheck('two distinct elements', solve(['a', 'b']), ['a', 'b'])\ncheck('nonadjacent duplicate and unsorted order', solve(['b', 'a', 'b', 'c']), ['b', 'a', 'b', 'c'])\ncheck('adjacent duplicates collapse', solve(['b','b','a','b']), ['b','a','b'])\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":"837ad5dc985c94e85ec832b6d01c5c6f90f939983da4c42e85e2cf2e53cdc2c4","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return list(dict.fromkeys(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']), ['a'])\ncheck('two distinct elements', solve(['a', 'b']), ['a', 'b'])\ncheck('nonadjacent duplicate and unsorted order', solve(['b', 'a', 'b', 'c']), ['b', 'a', 'b', 'c'])\ncheck('adjacent duplicates collapse', solve(['b','b','a','b']), ['b','a','b'])\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":"f28422db4de4fb02d1e1a015296226bf9b276e2c28af615f599ea64be9caa3da","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return [v for i,v in enumerate(x) if i == 0 or v != 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']), ['a'])\ncheck('two distinct elements', solve(['a', 'b']), ['a', 'b'])\ncheck('nonadjacent duplicate and unsorted order', solve(['b', 'a', 'b', 'c']), ['b', 'a', 'b', 'c'])\ncheck('adjacent duplicates collapse', solve(['b','b','a','b']), ['b','a','b'])\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-run-collapse","generated_at":"2026-09-29T14:37:35.588788+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":"Collapse adjacent equal values only; separated repetitions remain.","root_cause":"Global deduplication collapses equal values from separate runs.","sha256":"b03b4160b35e631cfebeec153a38ae86f1e51368a02c4a16a4730215d73fff6d","title":"Adjacent run collapse · 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":37.083,"exit_code":1,"observations":[{"actual":[],"check":"empty collection","expected":[],"passed":true},{"actual":["a"],"check":"singleton collection","expected":["a"],"passed":true},{"actual":["a","b"],"check":"two distinct elements","expected":["a","b"],"passed":true},{"actual":["a","b","c"],"check":"nonadjacent duplicate and unsorted order","expected":["b","a","b","c"],"passed":false},{"actual":["a","b"],"check":"adjacent duplicates collapse","expected":["b","a","b"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"empty collection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton collection\", \"actual\": [\"a\"], \"expected\": [\"a\"], \"passed\": true}, {\"check\": \"two distinct elements\", \"actual\": [\"a\", \"b\"], \"expected\": [\"a\", \"b\"], \"passed\": true}, {\"check\": \"nonadjacent duplicate and unsorted order\", \"actual\": [\"a\", \"b\", \"c\"], \"expected\": [\"b\", \"a\", \"b\", \"c\"], \"passed\": false}, {\"check\": \"adjacent duplicates collapse\", \"actual\": [\"a\", \"b\"], \"expected\": [\"b\", \"a\", \"b\"], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":37.803,"exit_code":1,"observations":[{"actual":[],"check":"empty collection","expected":[],"passed":true},{"actual":["a"],"check":"singleton collection","expected":["a"],"passed":true},{"actual":["a","b"],"check":"two distinct elements","expected":["a","b"],"passed":true},{"actual":["b","a","c"],"check":"nonadjacent duplicate and unsorted order","expected":["b","a","b","c"],"passed":false},{"actual":["b","a"],"check":"adjacent duplicates collapse","expected":["b","a","b"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"empty collection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton collection\", \"actual\": [\"a\"], \"expected\": [\"a\"], \"passed\": true}, {\"check\": \"two distinct elements\", \"actual\": [\"a\", \"b\"], \"expected\": [\"a\", \"b\"], \"passed\": true}, {\"check\": \"nonadjacent duplicate and unsorted order\", \"actual\": [\"b\", \"a\", \"c\"], \"expected\": [\"b\", \"a\", \"b\", \"c\"], \"passed\": false}, {\"check\": \"adjacent duplicates collapse\", \"actual\": [\"b\", \"a\"], \"expected\": [\"b\", \"a\", \"b\"], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":42.491,"exit_code":0,"observations":[{"actual":[],"check":"empty collection","expected":[],"passed":true},{"actual":["a"],"check":"singleton collection","expected":["a"],"passed":true},{"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","b","c"],"passed":true},{"actual":["b","a","b"],"check":"adjacent duplicates collapse","expected":["b","a","b"],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"empty collection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton collection\", \"actual\": [\"a\"], \"expected\": [\"a\"], \"passed\": true}, {\"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\", \"b\", \"c\"], \"passed\": true}, {\"check\": \"adjacent duplicates collapse\", \"actual\": [\"b\", \"a\", \"b\"], \"expected\": [\"b\", \"a\", \"b\"], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}