{"abstract":"A cache hit leaves the entry at the eviction end.","category":"Caching","checks":4,"contract":"Given unique keys ordered least to most recent, move an existing hit to the end; misses do not alter order.","contract_signature":"order, key","evaluation_group":"xc-lru-hit-promotes","failed_approach":"Moving a hit to the front makes it the next eviction victim.","family":"xc-lru-hit-promotes","id":"FA-10381","implementations":{"attempt":{"sha256":"e9c5dd504aa1bcbedefcc95fedbae8137b8261e8c69e0b7e5ef72e3070b8f60c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(order, key):\n    return [key]+[x for x in order if x != key] if key in order else list(order)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(['a', 'b', 'c'], 'a')), ['b', 'c', 'a'])\ncheck('fixture 2', solve(*(['a', 'b', 'c'], 'c')), ['a', 'b', 'c'])\ncheck('fixture 3', solve(*(['a'], 'absent')), ['a'])\ncheck('fixture 4', solve(*([], 'a')), [])\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":"b39d4fecedc3b351f4c4bb4455ad0f00c13468da19c80f5649db1260ae386f38","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(order, key):\n    return list(order)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(['a', 'b', 'c'], 'a')), ['b', 'c', 'a'])\ncheck('fixture 2', solve(*(['a', 'b', 'c'], 'c')), ['a', 'b', 'c'])\ncheck('fixture 3', solve(*(['a'], 'absent')), ['a'])\ncheck('fixture 4', solve(*([], 'a')), [])\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":"xc-lru-hit-promotes","generated_at":"2026-09-29T14:38:38.510988+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic cache state transformation. Inputs are copied or treated as immutable; no remote storage, real clock, or concurrent interleaving is simulated.","root_cause":"Successful reads do not update least-to-most-recent order.","sha256":"81bd9c49e8a2290e731fbd9d18277dc8375201323f464e31b286611c82508328","title":"A cache hit leaves the entry at the eviction end · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":40.316,"exit_code":1,"observations":[{"actual":["a","b","c"],"check":"fixture 1","expected":["b","c","a"],"passed":false},{"actual":["c","a","b"],"check":"fixture 2","expected":["a","b","c"],"passed":false},{"actual":["a"],"check":"fixture 3","expected":["a"],"passed":true},{"actual":[],"check":"fixture 4","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [\"a\", \"b\", \"c\"], \"expected\": [\"b\", \"c\", \"a\"], \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": [\"c\", \"a\", \"b\"], \"expected\": [\"a\", \"b\", \"c\"], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [\"a\"], \"expected\": [\"a\"], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.259,"exit_code":1,"observations":[{"actual":["a","b","c"],"check":"fixture 1","expected":["b","c","a"],"passed":false},{"actual":["a","b","c"],"check":"fixture 2","expected":["a","b","c"],"passed":true},{"actual":["a"],"check":"fixture 3","expected":["a"],"passed":true},{"actual":[],"check":"fixture 4","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [\"a\", \"b\", \"c\"], \"expected\": [\"b\", \"c\", \"a\"], \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": [\"a\", \"b\", \"c\"], \"expected\": [\"a\", \"b\", \"c\"], \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": [\"a\"], \"expected\": [\"a\"], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [], \"expected\": [], \"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."}}