{"abstract":"A logical position at a page boundary is assigned to the preceding block.","category":"KV cache position mapping","checks":6,"contract":"For nonnegative position and positive page_size, return (block_number, offset_within_block).","contract_signature":"position, page_size","evaluation_group":"w3-kv-map-paged-position-block","failed_approach":"Correctly selecting the block while returning the logical position as its offset breaks boundary writes.","family":"w3-kv-cache-position-mapping-paged-position-block","id":"FA-98556","implementations":{"attempt":{"sha256":"166c4c556f332ad221d3eac95c2b550d55ffa99c1a03e12fb779b6a098e62846","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(position, page_size):\n    return (position//page_size, position)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('first page',solve(N,4),(N//4,N%4))\ncheck('boundary',solve(8,4),(2,0))\ncheck('last offset',solve(7,4),(1,3))\ncheck('zero position',solve(0,5),(0,0))\ncheck('one page size',solve(4,4),(1,0))\ncheck('single element page',solve(N,1),(N,0))\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":"09e6078fc4c8af166722a375367f9f5f2498eee269c802e8b6039e34ad141ef7","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(position, page_size):\n    return ((position+page_size-1)//page_size, position%page_size)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('first page',solve(N,4),(N//4,N%4))\ncheck('boundary',solve(8,4),(2,0))\ncheck('last offset',solve(7,4),(1,3))\ncheck('zero position',solve(0,5),(0,0))\ncheck('one page size',solve(4,4),(1,0))\ncheck('single element page',solve(N,1),(N,0))\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 toy integer maps omit tensor layout, concurrency, device memory, and model-specific cache formats. 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-kv-cache-position-mapping-paged-position-block","generated_at":"2026-09-30T16:48:14.105598+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A small in-memory model makes the cache address contract explicit for a serving component.","root_cause":"Block selection uses a ceiling-like boundary rule.","sha256":"096cdb5801d73016d4741d3443de66ea4d2df412fc196f72ad67e736ef0bf8b8","title":"Paged cache position selects the correct block · 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":27.197,"exit_code":1,"observations":[{"actual":[0,1],"check":"first page","expected":[0,1],"passed":true},{"actual":[2,8],"check":"boundary","expected":[2,0],"passed":false},{"actual":[1,7],"check":"last offset","expected":[1,3],"passed":false},{"actual":[0,0],"check":"zero position","expected":[0,0],"passed":true},{"actual":[1,4],"check":"one page size","expected":[1,0],"passed":false},{"actual":[1,1],"check":"single element page","expected":[1,0],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"first page\", \"actual\": [0, 1], \"expected\": [0, 1], \"passed\": true}, {\"check\": \"boundary\", \"actual\": [2, 8], \"expected\": [2, 0], \"passed\": false}, {\"check\": \"last offset\", \"actual\": [1, 7], \"expected\": [1, 3], \"passed\": false}, {\"check\": \"zero position\", \"actual\": [0, 0], \"expected\": [0, 0], \"passed\": true}, {\"check\": \"one page size\", \"actual\": [1, 4], \"expected\": [1, 0], \"passed\": false}, {\"check\": \"single element page\", \"actual\": [1, 1], \"expected\": [1, 0], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":26.635,"exit_code":1,"observations":[{"actual":[1,1],"check":"first page","expected":[0,1],"passed":false},{"actual":[2,0],"check":"boundary","expected":[2,0],"passed":true},{"actual":[2,3],"check":"last offset","expected":[1,3],"passed":false},{"actual":[0,0],"check":"zero position","expected":[0,0],"passed":true},{"actual":[1,0],"check":"one page size","expected":[1,0],"passed":true},{"actual":[1,0],"check":"single element page","expected":[1,0],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"first page\", \"actual\": [1, 1], \"expected\": [0, 1], \"passed\": false}, {\"check\": \"boundary\", \"actual\": [2, 0], \"expected\": [2, 0], \"passed\": true}, {\"check\": \"last offset\", \"actual\": [2, 3], \"expected\": [1, 3], \"passed\": false}, {\"check\": \"zero position\", \"actual\": [0, 0], \"expected\": [0, 0], \"passed\": true}, {\"check\": \"one page size\", \"actual\": [1, 0], \"expected\": [1, 0], \"passed\": true}, {\"check\": \"single element page\", \"actual\": [1, 0], \"expected\": [1, 0], \"passed\": true}], \"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."}}