{"abstract":"Unknown deque checkpoint request clears saved history.","category":"Bounded deques","checks":6,"contract":"Deque savepoints capture ordered snapshots by unique tag. Rolling back restores a named snapshot and discards it plus nested checkpoints. Release discards the same checkpoint suffix without restoring data. Unknown tags preserve state.","contract_signature":"x","evaluation_group":"s3-bounded-deques-nested-checkpoints","failed_approach":"The partial repair still applies the incorrect transition to an admitted boundary or multi-element case.","family":"s3-bounded-deques-nested-checkpoints-unknown-preservation","id":"FA-46916","implementations":{"attempt":{"sha256":"507fc51c0cbf335bc8849b36239a5b608866254f08af347afae6c32e6dda24ef","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    a,stack,op,tag=x\n    if op=='save':return [a,stack+[[tag,a[:]]],tag,True]\n    where=next((i for i,z in enumerate(stack) if z[0]==tag),None)\n    if where is None:return [a,stack if not a else [],None,False]\n    retained=stack[:where]\n    state=stack[where][1][:] if op=='rollback' else a[:]\n    return [state,retained,tag,True]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('0', solve([[N+2],[[1,[N]],[2,[N+1]]],\"rollback\",1]), {1: [[1], [], 1, True], 2: [[2], [], 1, True], 3: [[3], [], 1, True], 4: [[4], [], 1, True], 5: [[5], [], 1, True]}[N])\ncheck('1', solve([[N+2],[[1,[N]],[2,[N+1]]],\"rollback\",2]), {1: [[2], [[1, [1]]], 2, True], 2: [[3], [[1, [2]]], 2, True], 3: [[4], [[1, [3]]], 2, True], 4: [[5], [[1, [4]]], 2, True], 5: [[6], [[1, [5]]], 2, True]}[N])\ncheck('2', solve([[N+2],[[1,[N]],[2,[N+1]]],\"release\",1]), {1: [[3], [], 1, True], 2: [[4], [], 1, True], 3: [[5], [], 1, True], 4: [[6], [], 1, True], 5: [[7], [], 1, True]}[N])\ncheck('3', solve([[N],[],\"save\",3]), {1: [[1], [[3, [1]]], 3, True], 2: [[2], [[3, [2]]], 3, True], 3: [[3], [[3, [3]]], 3, True], 4: [[4], [[3, [4]]], 3, True], 5: [[5], [[3, [5]]], 3, True]}[N])\ncheck('4', solve([[N],[[1,[N-1]]],\"save\",4]), {1: [[1], [[1, [0]], [4, [1]]], 4, True], 2: [[2], [[1, [1]], [4, [2]]], 4, True], 3: [[3], [[1, [2]], [4, [3]]], 4, True], 4: [[4], [[1, [3]], [4, [4]]], 4, True], 5: [[5], [[1, [4]], [4, [5]]], 4, True]}[N])\ncheck('5', solve([[N],[[1,[N-1]]],\"rollback\",9]), {1: [[1], [[1, [0]]], None, False], 2: [[2], [[1, [1]]], None, False], 3: [[3], [[1, [2]]], None, False], 4: [[4], [[1, [3]]], None, False], 5: [[5], [[1, [4]]], None, False]}[N])\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":"2c8c436d23f58561b691c90600f45c3780f45cfb5a85c53b28e2c41653db9bc7","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    a,stack,op,tag=x\n    if op=='save':return [a,stack+[[tag,a[:]]],tag,True]\n    where=next((i for i,z in enumerate(stack) if z[0]==tag),None)\n    if where is None:return [a,[],None,False]\n    retained=stack[:where]\n    state=stack[where][1][:] if op=='rollback' else a[:]\n    return [state,retained,tag,True]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('0', solve([[N+2],[[1,[N]],[2,[N+1]]],\"rollback\",1]), {1: [[1], [], 1, True], 2: [[2], [], 1, True], 3: [[3], [], 1, True], 4: [[4], [], 1, True], 5: [[5], [], 1, True]}[N])\ncheck('1', solve([[N+2],[[1,[N]],[2,[N+1]]],\"rollback\",2]), {1: [[2], [[1, [1]]], 2, True], 2: [[3], [[1, [2]]], 2, True], 3: [[4], [[1, [3]]], 2, True], 4: [[5], [[1, [4]]], 2, True], 5: [[6], [[1, [5]]], 2, True]}[N])\ncheck('2', solve([[N+2],[[1,[N]],[2,[N+1]]],\"release\",1]), {1: [[3], [], 1, True], 2: [[4], [], 1, True], 3: [[5], [], 1, True], 4: [[6], [], 1, True], 5: [[7], [], 1, True]}[N])\ncheck('3', solve([[N],[],\"save\",3]), {1: [[1], [[3, [1]]], 3, True], 2: [[2], [[3, [2]]], 3, True], 3: [[3], [[3, [3]]], 3, True], 4: [[4], [[3, [4]]], 3, True], 5: [[5], [[3, [5]]], 3, True]}[N])\ncheck('4', solve([[N],[[1,[N-1]]],\"save\",4]), {1: [[1], [[1, [0]], [4, [1]]], 4, True], 2: [[2], [[1, [1]], [4, [2]]], 4, True], 3: [[3], [[1, [2]], [4, [3]]], 4, True], 4: [[4], [[1, [3]], [4, [4]]], 4, True], 5: [[5], [[1, [4]], [4, [5]]], 4, True]}[N])\ncheck('5', solve([[N],[[1,[N-1]]],\"rollback\",9]), {1: [[1], [[1, [0]]], None, False], 2: [[2], [[1, [1]]], None, False], 3: [[3], [[1, [2]]], None, False], 4: [[4], [[1, [3]]], None, False], 5: [[5], [[1, [4]]], None, False]}[N])\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":"Offline finite deterministic model; no claim of production implementation or concurrent memory-model conformance. 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":"s3-bounded-deques-nested-checkpoints-unknown-preservation","generated_at":"2026-09-29T14:44:36.506101+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Controlled bounded deque implementation model with explicit storage and lifecycle observations.","root_cause":"Unknown deque checkpoint request clears saved history.","sha256":"152063db5bba161a050dcfe35f8646f97c62818bdc6639c5fde07b71ffe20348","title":"Unknown deque checkpoint request clears saved history · 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":39.471,"exit_code":1,"observations":[{"actual":[[1],[],1,true],"check":"0","expected":[[1],[],1,true],"passed":true},{"actual":[[2],[[1,[1]]],2,true],"check":"1","expected":[[2],[[1,[1]]],2,true],"passed":true},{"actual":[[3],[],1,true],"check":"2","expected":[[3],[],1,true],"passed":true},{"actual":[[1],[[3,[1]]],3,true],"check":"3","expected":[[1],[[3,[1]]],3,true],"passed":true},{"actual":[[1],[[1,[0]],[4,[1]]],4,true],"check":"4","expected":[[1],[[1,[0]],[4,[1]]],4,true],"passed":true},{"actual":[[1],[],null,false],"check":"5","expected":[[1],[[1,[0]]],null,false],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"0\", \"actual\": [[1], [], 1, true], \"expected\": [[1], [], 1, true], \"passed\": true}, {\"check\": \"1\", \"actual\": [[2], [[1, [1]]], 2, true], \"expected\": [[2], [[1, [1]]], 2, true], \"passed\": true}, {\"check\": \"2\", \"actual\": [[3], [], 1, true], \"expected\": [[3], [], 1, true], \"passed\": true}, {\"check\": \"3\", \"actual\": [[1], [[3, [1]]], 3, true], \"expected\": [[1], [[3, [1]]], 3, true], \"passed\": true}, {\"check\": \"4\", \"actual\": [[1], [[1, [0]], [4, [1]]], 4, true], \"expected\": [[1], [[1, [0]], [4, [1]]], 4, true], \"passed\": true}, {\"check\": \"5\", \"actual\": [[1], [], null, false], \"expected\": [[1], [[1, [0]]], null, false], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":38.746,"exit_code":1,"observations":[{"actual":[[1],[],1,true],"check":"0","expected":[[1],[],1,true],"passed":true},{"actual":[[2],[[1,[1]]],2,true],"check":"1","expected":[[2],[[1,[1]]],2,true],"passed":true},{"actual":[[3],[],1,true],"check":"2","expected":[[3],[],1,true],"passed":true},{"actual":[[1],[[3,[1]]],3,true],"check":"3","expected":[[1],[[3,[1]]],3,true],"passed":true},{"actual":[[1],[[1,[0]],[4,[1]]],4,true],"check":"4","expected":[[1],[[1,[0]],[4,[1]]],4,true],"passed":true},{"actual":[[1],[],null,false],"check":"5","expected":[[1],[[1,[0]]],null,false],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"0\", \"actual\": [[1], [], 1, true], \"expected\": [[1], [], 1, true], \"passed\": true}, {\"check\": \"1\", \"actual\": [[2], [[1, [1]]], 2, true], \"expected\": [[2], [[1, [1]]], 2, true], \"passed\": true}, {\"check\": \"2\", \"actual\": [[3], [], 1, true], \"expected\": [[3], [], 1, true], \"passed\": true}, {\"check\": \"3\", \"actual\": [[1], [[3, [1]]], 3, true], \"expected\": [[1], [[3, [1]]], 3, true], \"passed\": true}, {\"check\": \"4\", \"actual\": [[1], [[1, [0]], [4, [1]]], 4, true], \"expected\": [[1], [[1, [0]], [4, [1]]], 4, true], \"passed\": true}, {\"check\": \"5\", \"actual\": [[1], [], null, false], \"expected\": [[1], [[1, [0]]], null, false], \"passed\": false}], \"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."}}