{"abstract":"Bidirectional local attention omits future neighbors.","category":"Attention mask construction","checks":6,"contract":"For length L and radius R, query i sees keys j when |i-j|<=R, including both directions.","contract_signature":"length, radius","evaluation_group":"bidirectional_local_window_v1","failed_approach":"Using strict distance < radius omits keys exactly at the configured radius.","family":"w3-attention-mask-construction-bidirectional-window","id":"FA-98216","implementations":{"attempt":{"sha256":"32c69b8e76e3502d11fd4ba84266381836b9a9518ae7f741cb2b3e34d16b842a","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(length, radius):\n    return [[abs(i-j)<radius 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('symmetric neighborhood',solve(N+2,1),[[abs(i-j)<=1 for j in range(N+2)] for i in range(N+2)])\ncheck('radius zero',solve(3,0),[[i==j for j in range(3)] for i in range(3)])\ncheck('negative radius',solve(2,-1),[[False,False],[False,False]])\ncheck('empty',solve(0,1),[])\ncheck('singleton',solve(1,8),[[True]])\ncheck('future neighbor',solve(4,2)[0],[True,True,True,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":"957aa37b93743189e18033a13d22ab8b0a73e218d6a1ffc1e3b74a2ce9a60156","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(length, radius):\n    return [[j<=i and i-j<=radius 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('symmetric neighborhood',solve(N+2,1),[[abs(i-j)<=1 for j in range(N+2)] for i in range(N+2)])\ncheck('radius zero',solve(3,0),[[i==j for j in range(3)] for i in range(3)])\ncheck('negative radius',solve(2,-1),[[False,False],[False,False]])\ncheck('empty',solve(0,1),[])\ncheck('singleton',solve(1,8),[[True]])\ncheck('future neighbor',solve(4,2)[0],[True,True,True,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-bidirectional-window","generated_at":"2026-09-30T16:48:10.629859+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":"A causal predicate is retained in a symmetric neighborhood contract.","sha256":"feb74acd9267952654b662897711cc1a9e5709a69236f3ea7d95d2c1915ff865","title":"Bidirectional local attention omits future neighbors · 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":27.95,"exit_code":1,"observations":[{"actual":[[true,false,false],[false,true,false],[false,false,true]],"check":"symmetric neighborhood","expected":[[true,true,false],[true,true,true],[false,true,true]],"passed":false},{"actual":[[false,false,false],[false,false,false],[false,false,false]],"check":"radius zero","expected":[[true,false,false],[false,true,false],[false,false,true]],"passed":false},{"actual":[[false,false],[false,false]],"check":"negative radius","expected":[[false,false],[false,false]],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[true]],"check":"singleton","expected":[[true]],"passed":true},{"actual":[true,true,false,false],"check":"future neighbor","expected":[true,true,true,false],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"symmetric neighborhood\", \"actual\": [[true, false, false], [false, true, false], [false, false, true]], \"expected\": [[true, true, false], [true, true, true], [false, true, true]], \"passed\": false}, {\"check\": \"radius zero\", \"actual\": [[false, false, false], [false, false, false], [false, false, false]], \"expected\": [[true, false, false], [false, true, false], [false, false, true]], \"passed\": false}, {\"check\": \"negative radius\", \"actual\": [[false, false], [false, false]], \"expected\": [[false, false], [false, false]], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [[true]], \"expected\": [[true]], \"passed\": true}, {\"check\": \"future neighbor\", \"actual\": [true, true, false, false], \"expected\": [true, true, true, false], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":29.336,"exit_code":1,"observations":[{"actual":[[true,false,false],[true,true,false],[false,true,true]],"check":"symmetric neighborhood","expected":[[true,true,false],[true,true,true],[false,true,true]],"passed":false},{"actual":[[true,false,false],[false,true,false],[false,false,true]],"check":"radius zero","expected":[[true,false,false],[false,true,false],[false,false,true]],"passed":true},{"actual":[[false,false],[false,false]],"check":"negative radius","expected":[[false,false],[false,false]],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[true]],"check":"singleton","expected":[[true]],"passed":true},{"actual":[true,false,false,false],"check":"future neighbor","expected":[true,true,true,false],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"symmetric neighborhood\", \"actual\": [[true, false, false], [true, true, false], [false, true, true]], \"expected\": [[true, true, false], [true, true, true], [false, true, true]], \"passed\": false}, {\"check\": \"radius zero\", \"actual\": [[true, false, false], [false, true, false], [false, false, true]], \"expected\": [[true, false, false], [false, true, false], [false, false, true]], \"passed\": true}, {\"check\": \"negative radius\", \"actual\": [[false, false], [false, false]], \"expected\": [[false, false], [false, false]], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [[true]], \"expected\": [[true]], \"passed\": true}, {\"check\": \"future neighbor\", \"actual\": [true, false, false, false], \"expected\": [true, true, 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."}}