{"abstract":"Draft positions without verifier results are counted as covered.","category":"Speculative decoding bookkeeping","checks":7,"contract":"Return the number of positions present in both the draft and verifier result lists; token values do not affect coverage.","contract_signature":"draft, verified","evaluation_group":"spec-verified-prefix","failed_approach":"Subtracting one from verifier length undercounts when the verifier returned every draft position.","family":"w3-speculative-decoding-bookkeeping-verified-prefix","id":"FA-100666","implementations":{"attempt":{"sha256":"682ecf82a367cd22cb55237148df922dbba380998d5e05823cb3239339f00c8f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(draft, verified):\n    return max(0,len(verified)-1)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('same coverage', solve([1,2],[1,9]),2)\ncheck('short verifier', solve([1,2,3],[1,2]),2)\ncheck('short draft', solve([1],[1,2]),1)\ncheck('empty verifier', solve([1,2],[]),0)\ncheck('both empty', solve([],[]),0)\ncheck('single coverage', solve([N],[N+1]),1)\ncheck('different tokens still covered', solve([1,2],[8,7]),2)\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":"38f4420ba3ee5b877e8fd2713c866b6abf4c9a3d748f2e3b86c9b58d7d027e2b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(draft, verified):\n    return len(draft)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('same coverage', solve([1,2],[1,9]),2)\ncheck('short verifier', solve([1,2,3],[1,2]),2)\ncheck('short draft', solve([1],[1,2]),1)\ncheck('empty verifier', solve([1,2],[]),0)\ncheck('both empty', solve([],[]),0)\ncheck('single coverage', solve([N],[N+1]),1)\ncheck('different tokens still covered', solve([1,2],[8,7]),2)\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-prefix","generated_at":"2026-09-30T16:48:38.099320+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 entire draft length is counted even when the verifier returned fewer positions.","sha256":"16c19c3c178c748dd076732cebb85c5cc6835fe94f18c1d519cf73409839b875","title":"Decoding: Draft positions without verifier results are counted as covered · 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":29.406,"exit_code":1,"observations":[{"actual":1,"check":"same coverage","expected":2,"passed":false},{"actual":1,"check":"short verifier","expected":2,"passed":false},{"actual":1,"check":"short draft","expected":1,"passed":true},{"actual":0,"check":"empty verifier","expected":0,"passed":true},{"actual":0,"check":"both empty","expected":0,"passed":true},{"actual":0,"check":"single coverage","expected":1,"passed":false},{"actual":1,"check":"different tokens still covered","expected":2,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"same coverage\", \"actual\": 1, \"expected\": 2, \"passed\": false}, {\"check\": \"short verifier\", \"actual\": 1, \"expected\": 2, \"passed\": false}, {\"check\": \"short draft\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"empty verifier\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"both empty\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"single coverage\", \"actual\": 0, \"expected\": 1, \"passed\": false}, {\"check\": \"different tokens still covered\", \"actual\": 1, \"expected\": 2, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":27.684,"exit_code":1,"observations":[{"actual":2,"check":"same coverage","expected":2,"passed":true},{"actual":3,"check":"short verifier","expected":2,"passed":false},{"actual":1,"check":"short draft","expected":1,"passed":true},{"actual":2,"check":"empty verifier","expected":0,"passed":false},{"actual":0,"check":"both empty","expected":0,"passed":true},{"actual":1,"check":"single coverage","expected":1,"passed":true},{"actual":2,"check":"different tokens still covered","expected":2,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"same coverage\", \"actual\": 2, \"expected\": 2, \"passed\": true}, {\"check\": \"short verifier\", \"actual\": 3, \"expected\": 2, \"passed\": false}, {\"check\": \"short draft\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"empty verifier\", \"actual\": 2, \"expected\": 0, \"passed\": false}, {\"check\": \"both empty\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"single coverage\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"different tokens still covered\", \"actual\": 2, \"expected\": 2, \"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."}}