{"abstract":"Padded keys remain visible to active queries.","category":"Attention mask construction","checks":6,"contract":"Return rows for every query; a key is visible iff valid and key_index<=query_index.","contract_signature":"valid","evaluation_group":"key_padding_v1","failed_approach":"Masking invalid queries alone leaves padded key columns visible.","family":"w3-attention-mask-construction-key-padding","id":"FA-98146","implementations":{"attempt":{"sha256":"415e28534c079b7c112463d593bd1d18715372438cafe25571fd20cd79608f12","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(valid):\n    return [[bool(valid[i]) and j<=i for j in range(len(valid))] for i in range(len(valid))]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nv=[True]*N+[False]\ncheck('padded final key',solve(v),[[j<=i and j<N for j in range(N+1)] for i in range(N+1)])\ncheck('all valid',solve([True,True]),[[True,False],[True,True]])\ncheck('all padded',solve([False,False]),[[False,False],[False,False]])\ncheck('empty',solve([]),[])\ncheck('singleton active',solve([True]),[[True]])\ncheck('singleton pad',solve([False]),[[False]])\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":"a0dfb9ae6ff09e3d7d24055dd4082e44e770dbb377e12b7b4d8b7f215f874847","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(valid):\n    return [[j<=i for j in range(len(valid))] for i in range(len(valid))]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nv=[True]*N+[False]\ncheck('padded final key',solve(v),[[j<=i and j<N for j in range(N+1)] for i in range(N+1)])\ncheck('all valid',solve([True,True]),[[True,False],[True,True]])\ncheck('all padded',solve([False,False]),[[False,False],[False,False]])\ncheck('empty',solve([]),[])\ncheck('singleton active',solve([True]),[[True]])\ncheck('singleton pad',solve([False]),[[False]])\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":"These are toy Boolean matrix contracts; they do not define a production model architecture or tensor library behavior. 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":"w3-attention-mask-construction-key-padding","generated_at":"2026-09-30T16:48:09.758011+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A small explicit visibility matrix makes sequence-attention boundary behavior reviewable.","root_cause":"Key validity is not included in the attention predicate.","sha256":"6d48bcc429414018762769eca9b4d412e989b31797fa72fb1a9f0a1ad05b1e37","title":"Padded keys remain visible to active queries · case 01","variant":1,"variant_policy":"The fixture code references N, supplied as 1 through 5. Fixed boundary checks may repeat. These records share one mechanism and must remain together in evaluation splits.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":26.368,"exit_code":1,"observations":[{"actual":[[true,false],[false,false]],"check":"padded final key","expected":[[true,false],[true,false]],"passed":false},{"actual":[[true,false],[true,true]],"check":"all valid","expected":[[true,false],[true,true]],"passed":true},{"actual":[[false,false],[false,false]],"check":"all padded","expected":[[false,false],[false,false]],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[true]],"check":"singleton active","expected":[[true]],"passed":true},{"actual":[[false]],"check":"singleton pad","expected":[[false]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"padded final key\", \"actual\": [[true, false], [false, false]], \"expected\": [[true, false], [true, false]], \"passed\": false}, {\"check\": \"all valid\", \"actual\": [[true, false], [true, true]], \"expected\": [[true, false], [true, true]], \"passed\": true}, {\"check\": \"all padded\", \"actual\": [[false, false], [false, false]], \"expected\": [[false, false], [false, false]], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton active\", \"actual\": [[true]], \"expected\": [[true]], \"passed\": true}, {\"check\": \"singleton pad\", \"actual\": [[false]], \"expected\": [[false]], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":27.08,"exit_code":1,"observations":[{"actual":[[true,false],[true,true]],"check":"padded final key","expected":[[true,false],[true,false]],"passed":false},{"actual":[[true,false],[true,true]],"check":"all valid","expected":[[true,false],[true,true]],"passed":true},{"actual":[[true,false],[true,true]],"check":"all padded","expected":[[false,false],[false,false]],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[true]],"check":"singleton active","expected":[[true]],"passed":true},{"actual":[[true]],"check":"singleton pad","expected":[[false]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"padded final key\", \"actual\": [[true, false], [true, true]], \"expected\": [[true, false], [true, false]], \"passed\": false}, {\"check\": \"all valid\", \"actual\": [[true, false], [true, true]], \"expected\": [[true, false], [true, true]], \"passed\": true}, {\"check\": \"all padded\", \"actual\": [[true, false], [true, true]], \"expected\": [[false, false], [false, false]], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton active\", \"actual\": [[true]], \"expected\": [[true]], \"passed\": true}, {\"check\": \"singleton pad\", \"actual\": [[true]], \"expected\": [[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."}}