{"abstract":"Causal stripe mask includes keys from every residue.","category":"Attention mask construction","checks":6,"contract":"Query i sees causal key j iff j<=i and i%stride==j%stride.","contract_signature":"length, stride","evaluation_group":"causal_striped_v1","failed_approach":"Grouping positions into fixed-width buckets rejects aligned keys that cross a bucket boundary.","family":"w3-attention-mask-construction-causal-stripe","id":"FA-98221","implementations":{"attempt":{"sha256":"5e648564c57eb5a6eab81c1dc1947877dd08021fba402294e3230490e9381abd","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(length, stride):\n    return [[j<=i and i//stride==j//stride for j in range(length)] for i in range(length)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('same residue',solve(N+3,2),[[j<=i and i%2==j%2 for j in range(N+3)] for i in range(N+3)])\ncheck('unit stride',solve(3,1),[[j<=i for j in range(3)] for i in range(3)])\ncheck('empty',solve(0,2),[])\ncheck('singleton',solve(1,7),[[True]])\ncheck('future forbidden',solve(3,2)[0],[True,False,False])\ncheck('nonadjacent aligned',solve(5,2)[4],[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":"d25e11491655924425466d5c5294259b9898afca377e767ff8449f867c93877f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(length, stride):\n    return [[j<=i for j in range(length)] for i in range(length)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('same residue',solve(N+3,2),[[j<=i and i%2==j%2 for j in range(N+3)] for i in range(N+3)])\ncheck('unit stride',solve(3,1),[[j<=i for j in range(3)] for i in range(3)])\ncheck('empty',solve(0,2),[])\ncheck('singleton',solve(1,7),[[True]])\ncheck('future forbidden',solve(3,2)[0],[True,False,False])\ncheck('nonadjacent aligned',solve(5,2)[4],[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-causal-stripe","generated_at":"2026-09-30T16:48:10.629758+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 mask preserves causal order but omits the required residue constraint.","sha256":"7827aaa1aaa23026505a6dc0fd7d4b7ea23f3f46c5fa17cf88a89b08ea4bcb57","title":"Causal stripe mask includes keys from every residue · 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":29.116,"exit_code":1,"observations":[{"actual":[[true,false,false,false],[true,true,false,false],[false,false,true,false],[false,false,true,true]],"check":"same residue","expected":[[true,false,false,false],[false,true,false,false],[true,false,true,false],[false,true,false,true]],"passed":false},{"actual":[[true,false,false],[false,true,false],[false,false,true]],"check":"unit stride","expected":[[true,false,false],[true,true,false],[true,true,true]],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[true]],"check":"singleton","expected":[[true]],"passed":true},{"actual":[true,false,false],"check":"future forbidden","expected":[true,false,false],"passed":true},{"actual":[false,false,false,false,true],"check":"nonadjacent aligned","expected":[true,false,true,false,true],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"same residue\", \"actual\": [[true, false, false, false], [true, true, false, false], [false, false, true, false], [false, false, true, true]], \"expected\": [[true, false, false, false], [false, true, false, false], [true, false, true, false], [false, true, false, true]], \"passed\": false}, {\"check\": \"unit stride\", \"actual\": [[true, false, false], [false, true, false], [false, false, true]], \"expected\": [[true, false, false], [true, true, false], [true, true, true]], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [[true]], \"expected\": [[true]], \"passed\": true}, {\"check\": \"future forbidden\", \"actual\": [true, false, false], \"expected\": [true, false, false], \"passed\": true}, {\"check\": \"nonadjacent aligned\", \"actual\": [false, false, false, false, true], \"expected\": [true, false, true, false, true], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":28.284,"exit_code":1,"observations":[{"actual":[[true,false,false,false],[true,true,false,false],[true,true,true,false],[true,true,true,true]],"check":"same residue","expected":[[true,false,false,false],[false,true,false,false],[true,false,true,false],[false,true,false,true]],"passed":false},{"actual":[[true,false,false],[true,true,false],[true,true,true]],"check":"unit stride","expected":[[true,false,false],[true,true,false],[true,true,true]],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[true]],"check":"singleton","expected":[[true]],"passed":true},{"actual":[true,false,false],"check":"future forbidden","expected":[true,false,false],"passed":true},{"actual":[true,true,true,true,true],"check":"nonadjacent aligned","expected":[true,false,true,false,true],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"same residue\", \"actual\": [[true, false, false, false], [true, true, false, false], [true, true, true, false], [true, true, true, true]], \"expected\": [[true, false, false, false], [false, true, false, false], [true, false, true, false], [false, true, false, true]], \"passed\": false}, {\"check\": \"unit stride\", \"actual\": [[true, false, false], [true, true, false], [true, true, true]], \"expected\": [[true, false, false], [true, true, false], [true, true, true]], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [[true]], \"expected\": [[true]], \"passed\": true}, {\"check\": \"future forbidden\", \"actual\": [true, false, false], \"expected\": [true, false, false], \"passed\": true}, {\"check\": \"nonadjacent aligned\", \"actual\": [true, true, true, true, true], \"expected\": [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."}}