{"abstract":"Mismatch report returns the draft token instead of the verified token.","category":"Speculative decoding bookkeeping","checks":7,"contract":"For a nonnegative zero-based rejection index k, return verified[k] when present, otherwise None.","contract_signature":"draft, verified, k","evaluation_group":"spec-verified-mismatch-token","failed_approach":"Returning the first verified token fixes only rejection at position zero.","family":"w3-speculative-decoding-bookkeeping-verified-mismatch-token","id":"FA-100726","implementations":{"attempt":{"sha256":"69d617011432d660b18541974d54df696317f5bece1b68aab3bf8fae5810d685","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(draft, verified, k):\n    return verified[0] if verified else None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('middle mismatch', solve([1,2,3],[1,9,3],1),9)\ncheck('first mismatch', solve([5],[8],0),8)\ncheck('beyond verified', solve([1,2],[1],1),None)\ncheck('empty verified', solve([1],[],0),None)\ncheck('later position', solve([1,2,3],[1,2,7],2),7)\ncheck('singleton token', solve([N],[N+1],0),N+1)\ncheck('short draft but verified slot', solve([1],[1,4],1),4)\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":"48d57797d59a024da873f6f81118eb63d629e90029a8a78fcb20fb62691cc76b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(draft, verified, k):\n    return draft[k] if k < len(draft) else None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('middle mismatch', solve([1,2,3],[1,9,3],1),9)\ncheck('first mismatch', solve([5],[8],0),8)\ncheck('beyond verified', solve([1,2],[1],1),None)\ncheck('empty verified', solve([1],[],0),None)\ncheck('later position', solve([1,2,3],[1,2,7],2),7)\ncheck('singleton token', solve([N],[N+1],0),N+1)\ncheck('short draft but verified slot', solve([1],[1,4],1),4)\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 finite toy sequences with explicit contracts; they make no claim about production decoder behavior or model quality. 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-speculative-decoding-bookkeeping-verified-mismatch-token","generated_at":"2026-09-30T16:48:39.096632+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A self-contained bookkeeping model makes prefix and token-count semantics observable without a model runtime.","root_cause":"The draft token at the mismatch position is reported as if it were verified.","sha256":"3558247370b7b9aba6b6dfc37fb9f268ce4278036796da584cde0dfce9ba30a0","title":"Decoding: Mismatch report returns the draft token instead of the verified token · 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":34.691,"exit_code":1,"observations":[{"actual":1,"check":"middle mismatch","expected":9,"passed":false},{"actual":8,"check":"first mismatch","expected":8,"passed":true},{"actual":1,"check":"beyond verified","expected":null,"passed":false},{"actual":null,"check":"empty verified","expected":null,"passed":true},{"actual":1,"check":"later position","expected":7,"passed":false},{"actual":2,"check":"singleton token","expected":2,"passed":true},{"actual":1,"check":"short draft but verified slot","expected":4,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"middle mismatch\", \"actual\": 1, \"expected\": 9, \"passed\": false}, {\"check\": \"first mismatch\", \"actual\": 8, \"expected\": 8, \"passed\": true}, {\"check\": \"beyond verified\", \"actual\": 1, \"expected\": null, \"passed\": false}, {\"check\": \"empty verified\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"later position\", \"actual\": 1, \"expected\": 7, \"passed\": false}, {\"check\": \"singleton token\", \"actual\": 2, \"expected\": 2, \"passed\": true}, {\"check\": \"short draft but verified slot\", \"actual\": 1, \"expected\": 4, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":34.373,"exit_code":1,"observations":[{"actual":2,"check":"middle mismatch","expected":9,"passed":false},{"actual":5,"check":"first mismatch","expected":8,"passed":false},{"actual":2,"check":"beyond verified","expected":null,"passed":false},{"actual":1,"check":"empty verified","expected":null,"passed":false},{"actual":3,"check":"later position","expected":7,"passed":false},{"actual":1,"check":"singleton token","expected":2,"passed":false},{"actual":null,"check":"short draft but verified slot","expected":4,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"middle mismatch\", \"actual\": 2, \"expected\": 9, \"passed\": false}, {\"check\": \"first mismatch\", \"actual\": 5, \"expected\": 8, \"passed\": false}, {\"check\": \"beyond verified\", \"actual\": 2, \"expected\": null, \"passed\": false}, {\"check\": \"empty verified\", \"actual\": 1, \"expected\": null, \"passed\": false}, {\"check\": \"later position\", \"actual\": 3, \"expected\": 7, \"passed\": false}, {\"check\": \"singleton token\", \"actual\": 1, \"expected\": 2, \"passed\": false}, {\"check\": \"short draft but verified slot\", \"actual\": null, \"expected\": 4, \"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."}}