{"abstract":"Child beams inherit cache rows in their previous row order.","category":"KV cache position mapping","checks":6,"contract":"Return cache rows for each child in the supplied parent_indices order; parent indices may repeat.","contract_signature":"cache_rows, parent_indices","evaluation_group":"w3-kv-map-beam-parent-reorder","failed_approach":"Sorting selected parent IDs loses the decoder’s requested child ordering.","family":"w3-kv-cache-position-mapping-beam-parent-reorder","id":"FA-98581","implementations":{"attempt":{"sha256":"4721abff7c40365eb97b58a13d447b883d485918dccb3a464511c2fe745d0bbd","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(cache_rows, parent_indices):\n    return [cache_rows[i] for i in sorted(parent_indices)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nrows=[['a'],['b'],['c']]\ncheck('swap parents',solve(rows,[2,0]),[['c'],['a']])\ncheck('duplicate parent',solve(rows,[1,1]),[['b'],['b']])\ncheck('identity',solve(rows,[0,1,2]),rows)\ncheck('reverse',solve(rows,[2,1,0]),[['c'],['b'],['a']])\ncheck('empty children',solve(rows,[]),[])\ncheck('single child',solve(rows,[N%3]),[rows[N%3]])\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":"64ab9bbf18c6f9c860edc39b4ee90547ca635443ee8d178d6e583b24cfc2bafd","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(cache_rows, parent_indices):\n    return list(cache_rows[:len(parent_indices)])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nrows=[['a'],['b'],['c']]\ncheck('swap parents',solve(rows,[2,0]),[['c'],['a']])\ncheck('duplicate parent',solve(rows,[1,1]),[['b'],['b']])\ncheck('identity',solve(rows,[0,1,2]),rows)\ncheck('reverse',solve(rows,[2,1,0]),[['c'],['b'],['a']])\ncheck('empty children',solve(rows,[]),[])\ncheck('single child',solve(rows,[N%3]),[rows[N%3]])\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-beam-parent-reorder","generated_at":"2026-09-30T16:48:14.544565+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":"The beam selection scores are updated but their parent row indices are ignored.","sha256":"535dbf0bf133ef2f630cd10b55d99754c7c72842cee87a4726b01e93b6374e92","title":"Beam cache rows follow selected parent beams · 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":27.198,"exit_code":1,"observations":[{"actual":[["a"],["c"]],"check":"swap parents","expected":[["c"],["a"]],"passed":false},{"actual":[["b"],["b"]],"check":"duplicate parent","expected":[["b"],["b"]],"passed":true},{"actual":[["a"],["b"],["c"]],"check":"identity","expected":[["a"],["b"],["c"]],"passed":true},{"actual":[["a"],["b"],["c"]],"check":"reverse","expected":[["c"],["b"],["a"]],"passed":false},{"actual":[],"check":"empty children","expected":[],"passed":true},{"actual":[["b"]],"check":"single child","expected":[["b"]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"swap parents\", \"actual\": [[\"a\"], [\"c\"]], \"expected\": [[\"c\"], [\"a\"]], \"passed\": false}, {\"check\": \"duplicate parent\", \"actual\": [[\"b\"], [\"b\"]], \"expected\": [[\"b\"], [\"b\"]], \"passed\": true}, {\"check\": \"identity\", \"actual\": [[\"a\"], [\"b\"], [\"c\"]], \"expected\": [[\"a\"], [\"b\"], [\"c\"]], \"passed\": true}, {\"check\": \"reverse\", \"actual\": [[\"a\"], [\"b\"], [\"c\"]], \"expected\": [[\"c\"], [\"b\"], [\"a\"]], \"passed\": false}, {\"check\": \"empty children\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"single child\", \"actual\": [[\"b\"]], \"expected\": [[\"b\"]], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":25.798,"exit_code":1,"observations":[{"actual":[["a"],["b"]],"check":"swap parents","expected":[["c"],["a"]],"passed":false},{"actual":[["a"],["b"]],"check":"duplicate parent","expected":[["b"],["b"]],"passed":false},{"actual":[["a"],["b"],["c"]],"check":"identity","expected":[["a"],["b"],["c"]],"passed":true},{"actual":[["a"],["b"],["c"]],"check":"reverse","expected":[["c"],["b"],["a"]],"passed":false},{"actual":[],"check":"empty children","expected":[],"passed":true},{"actual":[["a"]],"check":"single child","expected":[["b"]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"swap parents\", \"actual\": [[\"a\"], [\"b\"]], \"expected\": [[\"c\"], [\"a\"]], \"passed\": false}, {\"check\": \"duplicate parent\", \"actual\": [[\"a\"], [\"b\"]], \"expected\": [[\"b\"], [\"b\"]], \"passed\": false}, {\"check\": \"identity\", \"actual\": [[\"a\"], [\"b\"], [\"c\"]], \"expected\": [[\"a\"], [\"b\"], [\"c\"]], \"passed\": true}, {\"check\": \"reverse\", \"actual\": [[\"a\"], [\"b\"], [\"c\"]], \"expected\": [[\"c\"], [\"b\"], [\"a\"]], \"passed\": false}, {\"check\": \"empty children\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"single child\", \"actual\": [[\"a\"]], \"expected\": [[\"b\"]], \"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."}}