{"abstract":"Attention crosses independent block boundaries.","category":"Attention mask construction","checks":6,"contract":"Square causal matrix; positions attend only within identical supplied block IDs.","contract_signature":"blocks","evaluation_group":"block_causal_v1","failed_approach":"Restricting matches to neighboring positions removes valid long-range visibility inside a block.","family":"w3-attention-mask-construction-block-diagonal","id":"FA-98161","implementations":{"attempt":{"sha256":"c80540fa838fb9f7fe53fbc19f0b9e92e3f720f3f6412ccdd20c0a0f6b921aed","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(blocks):\n    return [[blocks[i]==blocks[j] and j<=i and i-j<=1 for j in range(len(blocks))] for i in range(len(blocks))]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nb=[0]*N+[1,1]\ncheck('boundary isolation',solve(b),[[b[i]==b[j] and j<=i for j in range(len(b))] for i in range(len(b))])\ncheck('same block',solve([4,4]),[[True,False],[True,True]])\ncheck('alternating labels',solve([1,2,1]),[[True,False,False],[False,True,False],[True,False,True]])\ncheck('empty',solve([]),[])\ncheck('singleton',solve([7]),[[True]])\ncheck('equal-sized block IDs differ',solve([2,3,2]),[[True,False,False],[False,True,False],[True,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":"04b18d72c2265c2ae62f0f40a5f6f887287f6e19448c05272499c0651621e641","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(blocks):\n    return [[j<=i for j in range(len(blocks))] for i in range(len(blocks))]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nb=[0]*N+[1,1]\ncheck('boundary isolation',solve(b),[[b[i]==b[j] and j<=i for j in range(len(b))] for i in range(len(b))])\ncheck('same block',solve([4,4]),[[True,False],[True,True]])\ncheck('alternating labels',solve([1,2,1]),[[True,False,False],[False,True,False],[True,False,True]])\ncheck('empty',solve([]),[])\ncheck('singleton',solve([7]),[[True]])\ncheck('equal-sized block IDs differ',solve([2,3,2]),[[True,False,False],[False,True,False],[True,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-block-diagonal","generated_at":"2026-09-30T16:48:10.192954+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":"Visibility uses global causal order without checking block ownership.","sha256":"c83355fa874e5556ebaf9bfd75f89f51a422ebebcf375e36a465d99313e6d605","title":"Attention crosses independent block boundaries · 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":26.885,"exit_code":1,"observations":[{"actual":[[true,false,false],[false,true,false],[false,true,true]],"check":"boundary isolation","expected":[[true,false,false],[false,true,false],[false,true,true]],"passed":true},{"actual":[[true,false],[true,true]],"check":"same block","expected":[[true,false],[true,true]],"passed":true},{"actual":[[true,false,false],[false,true,false],[false,false,true]],"check":"alternating labels","expected":[[true,false,false],[false,true,false],[true,false,true]],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[true]],"check":"singleton","expected":[[true]],"passed":true},{"actual":[[true,false,false],[false,true,false],[false,false,true]],"check":"equal-sized block IDs differ","expected":[[true,false,false],[false,true,false],[true,false,true]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary isolation\", \"actual\": [[true, false, false], [false, true, false], [false, true, true]], \"expected\": [[true, false, false], [false, true, false], [false, true, true]], \"passed\": true}, {\"check\": \"same block\", \"actual\": [[true, false], [true, true]], \"expected\": [[true, false], [true, true]], \"passed\": true}, {\"check\": \"alternating labels\", \"actual\": [[true, false, false], [false, true, false], [false, false, true]], \"expected\": [[true, false, false], [false, true, false], [true, false, true]], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [[true]], \"expected\": [[true]], \"passed\": true}, {\"check\": \"equal-sized block IDs differ\", \"actual\": [[true, false, false], [false, true, false], [false, false, true]], \"expected\": [[true, false, false], [false, true, false], [true, false, true]], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":28.297,"exit_code":1,"observations":[{"actual":[[true,false,false],[true,true,false],[true,true,true]],"check":"boundary isolation","expected":[[true,false,false],[false,true,false],[false,true,true]],"passed":false},{"actual":[[true,false],[true,true]],"check":"same block","expected":[[true,false],[true,true]],"passed":true},{"actual":[[true,false,false],[true,true,false],[true,true,true]],"check":"alternating labels","expected":[[true,false,false],[false,true,false],[true,false,true]],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[true]],"check":"singleton","expected":[[true]],"passed":true},{"actual":[[true,false,false],[true,true,false],[true,true,true]],"check":"equal-sized block IDs differ","expected":[[true,false,false],[false,true,false],[true,false,true]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary isolation\", \"actual\": [[true, false, false], [true, true, false], [true, true, true]], \"expected\": [[true, false, false], [false, true, false], [false, true, true]], \"passed\": false}, {\"check\": \"same block\", \"actual\": [[true, false], [true, true]], \"expected\": [[true, false], [true, true]], \"passed\": true}, {\"check\": \"alternating labels\", \"actual\": [[true, false, false], [true, true, false], [true, true, true]], \"expected\": [[true, false, false], [false, true, false], [true, false, true]], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [[true]], \"expected\": [[true]], \"passed\": true}, {\"check\": \"equal-sized block IDs differ\", \"actual\": [[true, false, false], [true, true, false], [true, true, true]], \"expected\": [[true, false, false], [false, true, false], [true, 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."}}