{"abstract":"Absolute position omits the replacement token after rejection.","category":"Speculative decoding bookkeeping","checks":7,"contract":"Advance absolute position by accepted draft tokens plus one replacement token after rejection.","contract_signature":"position, accepted","evaluation_group":"spec-position-accounting","failed_approach":"Adding a constant two advances correctly only when exactly one draft token was accepted.","family":"w3-speculative-decoding-bookkeeping-position-accounting","id":"FA-100696","implementations":{"attempt":{"sha256":"f44cd12e6ccca251a3ce41052935c3d3cc1b588927c093cdebed10dc415a5be7","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(position, accepted):\n    return position+2\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('partial advance', solve(10,2),13)\ncheck('zero accepted', solve(4,0),5)\ncheck('single accepted', solve(0,1),2)\ncheck('negative base position', solve(-2,2),1)\ncheck('vary position', solve(N,1),N+2)\ncheck('large accepted', solve(3,4),8)\ncheck('no prefix', solve(9,0),10)\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":"3aecfb9648b780d6ecda39d09ce988d59f2bf104a89d6a3ee2f58e34665301f4","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(position, accepted):\n    return position+accepted\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('partial advance', solve(10,2),13)\ncheck('zero accepted', solve(4,0),5)\ncheck('single accepted', solve(0,1),2)\ncheck('negative base position', solve(-2,2),1)\ncheck('vary position', solve(N,1),N+2)\ncheck('large accepted', solve(3,4),8)\ncheck('no prefix', solve(9,0),10)\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-position-accounting","generated_at":"2026-09-30T16:48:38.598986+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 replacement token is omitted from absolute-position advancement.","sha256":"08314f6855dc9b58196603345fa36b620fe88f4e0b5402dfba498e95392fa465","title":"Decoding: Absolute position omits the replacement token after rejection · 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":31.093,"exit_code":1,"observations":[{"actual":12,"check":"partial advance","expected":13,"passed":false},{"actual":6,"check":"zero accepted","expected":5,"passed":false},{"actual":2,"check":"single accepted","expected":2,"passed":true},{"actual":0,"check":"negative base position","expected":1,"passed":false},{"actual":3,"check":"vary position","expected":3,"passed":true},{"actual":5,"check":"large accepted","expected":8,"passed":false},{"actual":11,"check":"no prefix","expected":10,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"partial advance\", \"actual\": 12, \"expected\": 13, \"passed\": false}, {\"check\": \"zero accepted\", \"actual\": 6, \"expected\": 5, \"passed\": false}, {\"check\": \"single accepted\", \"actual\": 2, \"expected\": 2, \"passed\": true}, {\"check\": \"negative base position\", \"actual\": 0, \"expected\": 1, \"passed\": false}, {\"check\": \"vary position\", \"actual\": 3, \"expected\": 3, \"passed\": true}, {\"check\": \"large accepted\", \"actual\": 5, \"expected\": 8, \"passed\": false}, {\"check\": \"no prefix\", \"actual\": 11, \"expected\": 10, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":32.305,"exit_code":1,"observations":[{"actual":12,"check":"partial advance","expected":13,"passed":false},{"actual":4,"check":"zero accepted","expected":5,"passed":false},{"actual":1,"check":"single accepted","expected":2,"passed":false},{"actual":0,"check":"negative base position","expected":1,"passed":false},{"actual":2,"check":"vary position","expected":3,"passed":false},{"actual":7,"check":"large accepted","expected":8,"passed":false},{"actual":9,"check":"no prefix","expected":10,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"partial advance\", \"actual\": 12, \"expected\": 13, \"passed\": false}, {\"check\": \"zero accepted\", \"actual\": 4, \"expected\": 5, \"passed\": false}, {\"check\": \"single accepted\", \"actual\": 1, \"expected\": 2, \"passed\": false}, {\"check\": \"negative base position\", \"actual\": 0, \"expected\": 1, \"passed\": false}, {\"check\": \"vary position\", \"actual\": 2, \"expected\": 3, \"passed\": false}, {\"check\": \"large accepted\", \"actual\": 7, \"expected\": 8, \"passed\": false}, {\"check\": \"no prefix\", \"actual\": 9, \"expected\": 10, \"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."}}