{"abstract":"Block sparse mask attends to non-neighbor blocks.","category":"Attention mask construction","checks":6,"contract":"Positions have block IDs; causal pair visible iff absolute block ID difference<=block_radius.","contract_signature":"blocks, block_radius","evaluation_group":"causal_block_neighbor_v1","failed_approach":"Checking only signed block difference lets a lower-numbered query block accept an earlier higher-numbered block.","family":"w3-attention-mask-construction-block-sparse-neighbors","id":"FA-98231","implementations":{"attempt":{"sha256":"f982a77641fa3cca5d84ce62bfc5dc781e8b0fc2ecec01812f4787476925f27f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(blocks, block_radius):\n    return [[j<=i and blocks[i]-blocks[j]<=block_radius 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=[i//2 for i in range(N+4)]\ncheck('block radius',solve(b,1),[[j<=i and abs(b[i]-b[j])<=1 for j in range(len(b))] for i in range(len(b))])\ncheck('same block',solve([0,0],0),[[True,False],[True,True]])\ncheck('adjacent blocks',solve([0,1],1),[[True,False],[True,True]])\ncheck('excluded block',solve([1,0,2],0),[[True,False,False],[False,True,False],[False,False,True]])\ncheck('empty',solve([],2),[])\ncheck('negative radius',solve([0,0],-1),[[False,False],[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":"5b6b6556fdc4e5dad68b6751c6c17ad525208a0849016e4c1461378762eb4644","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(blocks, block_radius):\n    return [[blocks[j]<=blocks[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=[i//2 for i in range(N+4)]\ncheck('block radius',solve(b,1),[[j<=i and abs(b[i]-b[j])<=1 for j in range(len(b))] for i in range(len(b))])\ncheck('same block',solve([0,0],0),[[True,False],[True,True]])\ncheck('adjacent blocks',solve([0,1],1),[[True,False],[True,True]])\ncheck('excluded block',solve([1,0,2],0),[[True,False,False],[False,True,False],[False,False,True]])\ncheck('empty',solve([],2),[])\ncheck('negative radius',solve([0,0],-1),[[False,False],[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-block-sparse-neighbors","generated_at":"2026-09-30T16:48:10.630175+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 predicate orders block IDs but never bounds their distance or checks causal token order.","sha256":"797b1fdd0d74e83e089c8c9924ffc4b3416ab6c587aa9c4a6cc973fe9af46560","title":"Block sparse mask attends to non-neighbor blocks · 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":29.312,"exit_code":1,"observations":[{"actual":[[true,false,false,false,false],[true,true,false,false,false],[true,true,true,false,false],[true,true,true,true,false],[false,false,true,true,true]],"check":"block radius","expected":[[true,false,false,false,false],[true,true,false,false,false],[true,true,true,false,false],[true,true,true,true,false],[false,false,true,true,true]],"passed":true},{"actual":[[true,false],[true,true]],"check":"same block","expected":[[true,false],[true,true]],"passed":true},{"actual":[[true,false],[true,true]],"check":"adjacent blocks","expected":[[true,false],[true,true]],"passed":true},{"actual":[[true,false,false],[true,true,false],[false,false,true]],"check":"excluded block","expected":[[true,false,false],[false,true,false],[false,false,true]],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[false,false],[false,false]],"check":"negative radius","expected":[[false,false],[false,false]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"block radius\", \"actual\": [[true, false, false, false, false], [true, true, false, false, false], [true, true, true, false, false], [true, true, true, true, false], [false, false, true, true, true]], \"expected\": [[true, false, false, false, false], [true, true, false, false, false], [true, true, true, false, false], [true, true, true, true, false], [false, false, true, true, true]], \"passed\": true}, {\"check\": \"same block\", \"actual\": [[true, false], [true, true]], \"expected\": [[true, false], [true, true]], \"passed\": true}, {\"check\": \"adjacent blocks\", \"actual\": [[true, false], [true, true]], \"expected\": [[true, false], [true, true]], \"passed\": true}, {\"check\": \"excluded block\", \"actual\": [[true, false, false], [true, true, false], [false, false, true]], \"expected\": [[true, false, false], [false, true, false], [false, false, true]], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"negative radius\", \"actual\": [[false, false], [false, false]], \"expected\": [[false, false], [false, false]], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":27.817,"exit_code":1,"observations":[{"actual":[[true,true,false,false,false],[true,true,false,false,false],[true,true,true,true,false],[true,true,true,true,false],[true,true,true,true,true]],"check":"block radius","expected":[[true,false,false,false,false],[true,true,false,false,false],[true,true,true,false,false],[true,true,true,true,false],[false,false,true,true,true]],"passed":false},{"actual":[[true,true],[true,true]],"check":"same block","expected":[[true,false],[true,true]],"passed":false},{"actual":[[true,false],[true,true]],"check":"adjacent blocks","expected":[[true,false],[true,true]],"passed":true},{"actual":[[true,true,false],[false,true,false],[true,true,true]],"check":"excluded block","expected":[[true,false,false],[false,true,false],[false,false,true]],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[true,true],[true,true]],"check":"negative radius","expected":[[false,false],[false,false]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"block radius\", \"actual\": [[true, true, false, false, false], [true, true, false, false, false], [true, true, true, true, false], [true, true, true, true, false], [true, true, true, true, true]], \"expected\": [[true, false, false, false, false], [true, true, false, false, false], [true, true, true, false, false], [true, true, true, true, false], [false, false, true, true, true]], \"passed\": false}, {\"check\": \"same block\", \"actual\": [[true, true], [true, true]], \"expected\": [[true, false], [true, true]], \"passed\": false}, {\"check\": \"adjacent blocks\", \"actual\": [[true, false], [true, true]], \"expected\": [[true, false], [true, true]], \"passed\": true}, {\"check\": \"excluded block\", \"actual\": [[true, true, false], [false, true, false], [true, true, true]], \"expected\": [[true, false, false], [false, true, false], [false, false, true]], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"negative radius\", \"actual\": [[true, true], [true, true]], \"expected\": [[false, false], [false, 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."}}