{"abstract":"Cached rectangular attention uses local instead of absolute positions.","category":"Attention mask construction","checks":6,"contract":"Queries occupy absolute positions [query_start, query_start+Q); keys are absolute [0,K).","contract_signature":"key_count, query_count, query_start","evaluation_group":"rectangular_causal_v1","failed_approach":"Shifting by the whole key length works only when the cache is full.","family":"w3-attention-mask-construction-rectangular-offset-causal","id":"FA-98176","implementations":{"attempt":{"sha256":"8cb640083acb71fe27dadd6fac3a36cb1cd1073c175fc6f0af2a135f58b802e1","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(key_count, query_count, query_start):\n    return [[j<=key_count-query_count+i for j in range(key_count)] for i in range(query_count)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('partial cache offset',solve(N+3,2,N),[[j<=N+i for j in range(N+3)] for i in range(2)])\ncheck('zero offset',solve(3,2,0),[[j<=i for j in range(3)] for i in range(2)])\ncheck('empty queries',solve(3,0,2),[])\ncheck('empty keys',solve(0,2,0),[[],[]])\ncheck('one query',solve(4,1,2),[[True,True,True,False]])\ncheck('last cached query',solve(5,2,3)[1],[True,True,True,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":"1424425697c7c5b15cf7e04c0820f2f7800fb4ba3e81fb62c0d44fb9191976f3","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(key_count, query_count, query_start):\n    return [[j<=i for j in range(key_count)] for i in range(query_count)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('partial cache offset',solve(N+3,2,N),[[j<=N+i for j in range(N+3)] for i in range(2)])\ncheck('zero offset',solve(3,2,0),[[j<=i for j in range(3)] for i in range(2)])\ncheck('empty queries',solve(3,0,2),[])\ncheck('empty keys',solve(0,2,0),[[],[]])\ncheck('one query',solve(4,1,2),[[True,True,True,False]])\ncheck('last cached query',solve(5,2,3)[1],[True,True,True,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-rectangular-offset-causal","generated_at":"2026-09-30T16:48:10.193787+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 query row index is compared directly to key positions.","sha256":"e7a3a0b086b340eff50da25cbea6e8521abf73f5cc230652df3851c58c26d942","title":"Cached rectangular attention uses local instead of absolute positions · 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":27.098,"exit_code":1,"observations":[{"actual":[[true,true,true,false],[true,true,true,true]],"check":"partial cache offset","expected":[[true,true,false,false],[true,true,true,false]],"passed":false},{"actual":[[true,true,false],[true,true,true]],"check":"zero offset","expected":[[true,false,false],[true,true,false]],"passed":false},{"actual":[],"check":"empty queries","expected":[],"passed":true},{"actual":[[],[]],"check":"empty keys","expected":[[],[]],"passed":true},{"actual":[[true,true,true,true]],"check":"one query","expected":[[true,true,true,false]],"passed":false},{"actual":[true,true,true,true,true],"check":"last cached query","expected":[true,true,true,true,true],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"partial cache offset\", \"actual\": [[true, true, true, false], [true, true, true, true]], \"expected\": [[true, true, false, false], [true, true, true, false]], \"passed\": false}, {\"check\": \"zero offset\", \"actual\": [[true, true, false], [true, true, true]], \"expected\": [[true, false, false], [true, true, false]], \"passed\": false}, {\"check\": \"empty queries\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty keys\", \"actual\": [[], []], \"expected\": [[], []], \"passed\": true}, {\"check\": \"one query\", \"actual\": [[true, true, true, true]], \"expected\": [[true, true, true, false]], \"passed\": false}, {\"check\": \"last cached query\", \"actual\": [true, true, true, true, true], \"expected\": [true, true, true, true, true], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":28.254,"exit_code":1,"observations":[{"actual":[[true,false,false,false],[true,true,false,false]],"check":"partial cache offset","expected":[[true,true,false,false],[true,true,true,false]],"passed":false},{"actual":[[true,false,false],[true,true,false]],"check":"zero offset","expected":[[true,false,false],[true,true,false]],"passed":true},{"actual":[],"check":"empty queries","expected":[],"passed":true},{"actual":[[],[]],"check":"empty keys","expected":[[],[]],"passed":true},{"actual":[[true,false,false,false]],"check":"one query","expected":[[true,true,true,false]],"passed":false},{"actual":[true,true,false,false,false],"check":"last cached query","expected":[true,true,true,true,true],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"partial cache offset\", \"actual\": [[true, false, false, false], [true, true, false, false]], \"expected\": [[true, true, false, false], [true, true, true, false]], \"passed\": false}, {\"check\": \"zero offset\", \"actual\": [[true, false, false], [true, true, false]], \"expected\": [[true, false, false], [true, true, false]], \"passed\": true}, {\"check\": \"empty queries\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty keys\", \"actual\": [[], []], \"expected\": [[], []], \"passed\": true}, {\"check\": \"one query\", \"actual\": [[true, false, false, false]], \"expected\": [[true, true, true, false]], \"passed\": false}, {\"check\": \"last cached query\", \"actual\": [true, true, false, false, false], \"expected\": [true, true, true, 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."}}