{"abstract":"Cross-attention mask omits the source interval limit.","category":"Attention mask construction","checks":6,"contract":"Query q sees source indices in [q+offset-left, q+offset+right], clipped to source bounds; left and right are nonnegative.","contract_signature":"source_count, query_count, offset, left, right","evaluation_group":"aligned_banded_cross_v1","failed_approach":"Using one source interval for every query misses the query-dependent alignment shift.","family":"w3-attention-mask-construction-banded-cross-attention","id":"FA-98236","implementations":{"attempt":{"sha256":"b6fbc03bcf39dd231a41429b1cfe133127e3d998fcebd0ba68ea7ce99580d481","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(source_count, query_count, offset, left, right):\n    return [[max(0,offset-left)<=s<min(source_count,offset+right+1) for s in range(source_count)] for q in range(query_count)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('moving source window',solve(N+3,3,1,1,0),[[max(0,q+1-1)<=s<min(N+3,q+2) for s in range(N+3)] for q in range(3)])\ncheck('one-to-one',solve(3,3,0,0,0),[[s==q for s in range(3)] for q in range(3)])\ncheck('empty source',solve(0,2,0,1,1),[[],[]])\ncheck('empty queries',solve(3,0,0,1,1),[])\ncheck('window clipped left',solve(3,1,0,2,0),[[True,False,False]])\ncheck('window clipped right',solve(3,3,0,0,1)[2],[False,False,True])\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":"3eb4104b50656a4d8fafb789fb3009c99c066e3cdffe5f61126c949c5bf1d31a","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(source_count, query_count, offset, left, right):\n    return [[True for _ in range(source_count)] for _ in range(query_count)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('moving source window',solve(N+3,3,1,1,0),[[max(0,q+1-1)<=s<min(N+3,q+2) for s in range(N+3)] for q in range(3)])\ncheck('one-to-one',solve(3,3,0,0,0),[[s==q for s in range(3)] for q in range(3)])\ncheck('empty source',solve(0,2,0,1,1),[[],[]])\ncheck('empty queries',solve(3,0,0,1,1),[])\ncheck('window clipped left',solve(3,1,0,2,0),[[True,False,False]])\ncheck('window clipped right',solve(3,3,0,0,1)[2],[False,False,True])\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-banded-cross-attention","generated_at":"2026-09-30T16:48:10.630067+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":"Every source key is enabled, regardless of its distance from the aligned source interval.","sha256":"2b45e2fa66a3a0ca91a64da5008634230423be576ef159922d74c89560bbc44d","title":"Cross-attention mask omits the source interval limit · 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":28.582,"exit_code":1,"observations":[{"actual":[[true,true,false,false],[true,true,false,false],[true,true,false,false]],"check":"moving source window","expected":[[true,true,false,false],[false,true,true,false],[false,false,true,true]],"passed":false},{"actual":[[true,false,false],[true,false,false],[true,false,false]],"check":"one-to-one","expected":[[true,false,false],[false,true,false],[false,false,true]],"passed":false},{"actual":[[],[]],"check":"empty source","expected":[[],[]],"passed":true},{"actual":[],"check":"empty queries","expected":[],"passed":true},{"actual":[[true,false,false]],"check":"window clipped left","expected":[[true,false,false]],"passed":true},{"actual":[true,true,false],"check":"window clipped right","expected":[false,false,true],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"moving source window\", \"actual\": [[true, true, false, false], [true, true, false, false], [true, true, false, false]], \"expected\": [[true, true, false, false], [false, true, true, false], [false, false, true, true]], \"passed\": false}, {\"check\": \"one-to-one\", \"actual\": [[true, false, false], [true, false, false], [true, false, false]], \"expected\": [[true, false, false], [false, true, false], [false, false, true]], \"passed\": false}, {\"check\": \"empty source\", \"actual\": [[], []], \"expected\": [[], []], \"passed\": true}, {\"check\": \"empty queries\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"window clipped left\", \"actual\": [[true, false, false]], \"expected\": [[true, false, false]], \"passed\": true}, {\"check\": \"window clipped right\", \"actual\": [true, true, false], \"expected\": [false, false, true], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":27.464,"exit_code":1,"observations":[{"actual":[[true,true,true,true],[true,true,true,true],[true,true,true,true]],"check":"moving source window","expected":[[true,true,false,false],[false,true,true,false],[false,false,true,true]],"passed":false},{"actual":[[true,true,true],[true,true,true],[true,true,true]],"check":"one-to-one","expected":[[true,false,false],[false,true,false],[false,false,true]],"passed":false},{"actual":[[],[]],"check":"empty source","expected":[[],[]],"passed":true},{"actual":[],"check":"empty queries","expected":[],"passed":true},{"actual":[[true,true,true]],"check":"window clipped left","expected":[[true,false,false]],"passed":false},{"actual":[true,true,true],"check":"window clipped right","expected":[false,false,true],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"moving source window\", \"actual\": [[true, true, true, true], [true, true, true, true], [true, true, true, true]], \"expected\": [[true, true, false, false], [false, true, true, false], [false, false, true, true]], \"passed\": false}, {\"check\": \"one-to-one\", \"actual\": [[true, true, true], [true, true, true], [true, true, true]], \"expected\": [[true, false, false], [false, true, false], [false, false, true]], \"passed\": false}, {\"check\": \"empty source\", \"actual\": [[], []], \"expected\": [[], []], \"passed\": true}, {\"check\": \"empty queries\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"window clipped left\", \"actual\": [[true, true, true]], \"expected\": [[true, false, false]], \"passed\": false}, {\"check\": \"window clipped right\", \"actual\": [true, true, true], \"expected\": [false, false, true], \"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."}}