{"abstract":"Cross-attention mask swaps source and query dimensions.","category":"Attention mask construction","checks":6,"contract":"Return QxS visibility from target queries to every valid source key; query values do not affect visibility.","contract_signature":"source_valid, query_count","evaluation_group":"cross_attention_source_padding_v1","failed_approach":"Broadcasting a query-indexed source validity bit across the row loses the individual source-key validity pattern.","family":"w3-attention-mask-construction-cross-attention-padding","id":"FA-98181","implementations":{"attempt":{"sha256":"8e792556b0623826d1adfbba12f220b670f092c6a7ed69f19e2fe6ae5eb2b2a7","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(source_valid, query_count):\n    return [[bool(source_valid[q%len(source_valid)]) for _ in source_valid] for q in range(query_count)] if source_valid else [[] for _ in range(query_count)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ns=[True]*N+[False,True]\ncheck('rectangular source',solve(s,2),[[True]*N+[False,True] for _ in range(2)])\ncheck('no sources',solve([],3),[[],[],[]])\ncheck('no queries',solve([True],0),[])\ncheck('all padded sources',solve([False,False],1),[[False,False]])\ncheck('single valid source',solve([False,True],2),[[False,True],[False,True]])\ncheck('queries independent',solve([True,False],3),[[True,False]]*3)\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":"dca0c4ee52f87787b2a2c6a43f8fdceedfc41a8cade0bd7e5e85779fb15ee584","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(source_valid, query_count):\n    return [[True for _ in range(query_count)] for _ in source_valid]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ns=[True]*N+[False,True]\ncheck('rectangular source',solve(s,2),[[True]*N+[False,True] for _ in range(2)])\ncheck('no sources',solve([],3),[[],[],[]])\ncheck('no queries',solve([True],0),[])\ncheck('all padded sources',solve([False,False],1),[[False,False]])\ncheck('single valid source',solve([False,True],2),[[False,True],[False,True]])\ncheck('queries independent',solve([True,False],3),[[True,False]]*3)\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-cross-attention-padding","generated_at":"2026-09-30T16:48:10.193045+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":"Rows use the source count and columns use the query count, while source-key padding is ignored.","sha256":"8a51eb82147a1d4a0b0b3b0062c36e1c3c9bb77aaf72225cc82e8962e822817a","title":"Cross-attention mask swaps source and query dimensions · 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":27.541,"exit_code":1,"observations":[{"actual":[[true,true,true],[false,false,false]],"check":"rectangular source","expected":[[true,false,true],[true,false,true]],"passed":false},{"actual":[[],[],[]],"check":"no sources","expected":[[],[],[]],"passed":true},{"actual":[],"check":"no queries","expected":[],"passed":true},{"actual":[[false,false]],"check":"all padded sources","expected":[[false,false]],"passed":true},{"actual":[[false,false],[true,true]],"check":"single valid source","expected":[[false,true],[false,true]],"passed":false},{"actual":[[true,true],[false,false],[true,true]],"check":"queries independent","expected":[[true,false],[true,false],[true,false]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"rectangular source\", \"actual\": [[true, true, true], [false, false, false]], \"expected\": [[true, false, true], [true, false, true]], \"passed\": false}, {\"check\": \"no sources\", \"actual\": [[], [], []], \"expected\": [[], [], []], \"passed\": true}, {\"check\": \"no queries\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"all padded sources\", \"actual\": [[false, false]], \"expected\": [[false, false]], \"passed\": true}, {\"check\": \"single valid source\", \"actual\": [[false, false], [true, true]], \"expected\": [[false, true], [false, true]], \"passed\": false}, {\"check\": \"queries independent\", \"actual\": [[true, true], [false, false], [true, true]], \"expected\": [[true, false], [true, false], [true, false]], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":27.285,"exit_code":1,"observations":[{"actual":[[true,true],[true,true],[true,true]],"check":"rectangular source","expected":[[true,false,true],[true,false,true]],"passed":false},{"actual":[],"check":"no sources","expected":[[],[],[]],"passed":false},{"actual":[[]],"check":"no queries","expected":[],"passed":false},{"actual":[[true],[true]],"check":"all padded sources","expected":[[false,false]],"passed":false},{"actual":[[true,true],[true,true]],"check":"single valid source","expected":[[false,true],[false,true]],"passed":false},{"actual":[[true,true,true],[true,true,true]],"check":"queries independent","expected":[[true,false],[true,false],[true,false]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"rectangular source\", \"actual\": [[true, true], [true, true], [true, true]], \"expected\": [[true, false, true], [true, false, true]], \"passed\": false}, {\"check\": \"no sources\", \"actual\": [], \"expected\": [[], [], []], \"passed\": false}, {\"check\": \"no queries\", \"actual\": [[]], \"expected\": [], \"passed\": false}, {\"check\": \"all padded sources\", \"actual\": [[true], [true]], \"expected\": [[false, false]], \"passed\": false}, {\"check\": \"single valid source\", \"actual\": [[true, true], [true, true]], \"expected\": [[false, true], [false, true]], \"passed\": false}, {\"check\": \"queries independent\", \"actual\": [[true, true, true], [true, true, true]], \"expected\": [[true, false], [true, false], [true, 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."}}