{"abstract":"Causal ordering hides valid encoder states in cross-attention.","category":"Attention mask construction","checks":6,"contract":"Cross-attention visibility is source-key validity replicated for each decoder query.","contract_signature":"source_valid, query_count","evaluation_group":"encoder_decoder_cross_mask_v1","failed_approach":"Selecting one source validity bit by query row and broadcasting it across keys loses each key’s own padding state.","family":"w3-attention-mask-construction-encoder-decoder-causal","id":"FA-98186","implementations":{"attempt":{"sha256":"636749adc2dd945415c14bd3558a915d2d74eefbd9a5ae5e35078d00d2c0dd3a","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]\ncheck('later source visible',solve(s,2),[[True]*N+[False] for _ in range(2)])\ncheck('single decoder query',solve([True,True],1),[[True,True]])\ncheck('zero source',solve([],2),[[],[]])\ncheck('zero target',solve([True],0),[])\ncheck('all invalid source',solve([False,False],2),[[False,False],[False,False]])\ncheck('source order retained',solve([False,True,True],1),[[False,True,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":"c9722cabb63d7d8521f806f7290a1d787ab6f3fc9340515aa7824dd5b7b2c771","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[j]) and j<=i for j in range(len(source_valid))] for i 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]\ncheck('later source visible',solve(s,2),[[True]*N+[False] for _ in range(2)])\ncheck('single decoder query',solve([True,True],1),[[True,True]])\ncheck('zero source',solve([],2),[[],[]])\ncheck('zero target',solve([True],0),[])\ncheck('all invalid source',solve([False,False],2),[[False,False],[False,False]])\ncheck('source order retained',solve([False,True,True],1),[[False,True,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-encoder-decoder-causal","generated_at":"2026-09-30T16:48:10.196425+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":"The key index is limited by decoder query position even though encoder keys are all available.","sha256":"ad71ea21c557e6fba498b14d30f913ad5d30bac222550e553c24e9d3a5c38e50","title":"Causal ordering hides valid encoder states in cross-attention · 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":27.072,"exit_code":1,"observations":[{"actual":[[true,true],[false,false]],"check":"later source visible","expected":[[true,false],[true,false]],"passed":false},{"actual":[[true,true]],"check":"single decoder query","expected":[[true,true]],"passed":true},{"actual":[[],[]],"check":"zero source","expected":[[],[]],"passed":true},{"actual":[],"check":"zero target","expected":[],"passed":true},{"actual":[[false,false],[false,false]],"check":"all invalid source","expected":[[false,false],[false,false]],"passed":true},{"actual":[[false,false,false]],"check":"source order retained","expected":[[false,true,true]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"later source visible\", \"actual\": [[true, true], [false, false]], \"expected\": [[true, false], [true, false]], \"passed\": false}, {\"check\": \"single decoder query\", \"actual\": [[true, true]], \"expected\": [[true, true]], \"passed\": true}, {\"check\": \"zero source\", \"actual\": [[], []], \"expected\": [[], []], \"passed\": true}, {\"check\": \"zero target\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"all invalid source\", \"actual\": [[false, false], [false, false]], \"expected\": [[false, false], [false, false]], \"passed\": true}, {\"check\": \"source order retained\", \"actual\": [[false, false, false]], \"expected\": [[false, true, true]], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":27.241,"exit_code":1,"observations":[{"actual":[[true,false],[true,false]],"check":"later source visible","expected":[[true,false],[true,false]],"passed":true},{"actual":[[true,false]],"check":"single decoder query","expected":[[true,true]],"passed":false},{"actual":[[],[]],"check":"zero source","expected":[[],[]],"passed":true},{"actual":[],"check":"zero target","expected":[],"passed":true},{"actual":[[false,false],[false,false]],"check":"all invalid source","expected":[[false,false],[false,false]],"passed":true},{"actual":[[false,false,false]],"check":"source order retained","expected":[[false,true,true]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"later source visible\", \"actual\": [[true, false], [true, false]], \"expected\": [[true, false], [true, false]], \"passed\": true}, {\"check\": \"single decoder query\", \"actual\": [[true, false]], \"expected\": [[true, true]], \"passed\": false}, {\"check\": \"zero source\", \"actual\": [[], []], \"expected\": [[], []], \"passed\": true}, {\"check\": \"zero target\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"all invalid source\", \"actual\": [[false, false], [false, false]], \"expected\": [[false, false], [false, false]], \"passed\": true}, {\"check\": \"source order retained\", \"actual\": [[false, false, false]], \"expected\": [[false, true, 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."}}