{"abstract":"EOS is classified without truncating output.","category":"Model output stopping rules","checks":6,"contract":"Truncate before the first end token and report reason eos; if absent preserve all and report null.","contract_signature":"tokens, eos_id","evaluation_group":"w3-output-eos","failed_approach":"Including EOS in the returned prefix exposes the marker as output.","family":"w3-model-output-stopping-rules-eos-token","id":"FA-100781","implementations":{"attempt":{"sha256":"4cb7c824d6b4a8bed61881e64dea51faf98ef0ef89bc2371fb1efc0a8e3bff81","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(tokens, eos_id):\n    if eos_id in tokens:return tokens[:tokens.index(eos_id)+1],'eos'\n    return tokens,None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('eos middle',solve([1,9,2],9),([1],'eos'))\ncheck('eos first',solve([9],9),([],'eos'))\ncheck('absent',solve([1,2],9),([1,2],None))\ncheck('empty',solve([],9),([],None))\ncheck('repeated eos',solve([1,9,9],9),([1],'eos'))\ncheck('zero eos valid',solve([2,0,3],0),([2],'eos'))\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":"a3151b4206105282d82fc8093ad48f41d80a310b7a58827ac51fb459fdfd4ab9","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(tokens, eos_id):\n    return (tokens,None) if eos_id not in tokens else (tokens,'eos')\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('eos middle',solve([1,9,2],9),([1],'eos'))\ncheck('eos first',solve([9],9),([],'eos'))\ncheck('absent',solve([1,2],9),([1,2],None))\ncheck('empty',solve([],9),([],None))\ncheck('repeated eos',solve([1,9,9],9),([1],'eos'))\ncheck('zero eos valid',solve([2,0,3],0),([2],'eos'))\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":"This toy contract covers the supplied token records only; it does not claim compatibility with a particular model runtime or tokenizer. 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-model-output-stopping-rules-eos-token","generated_at":"2026-09-30T16:48:39.593556+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic output-control model isolates one finish or streaming boundary from any particular runtime.","root_cause":"The end token is classified but output is not cut at its first occurrence.","sha256":"fae43f8ebe4dcd438245f50a2761f063ab246d3dc87bc9de30c876b1111a42a9","title":"Output stopping: EOS is classified without truncating output · case 01","variant":1,"variant_policy":"The same explicitly authored fixtures repeat across all five numbered records; runtime N is unused. These records share one mechanism and must remain together in evaluation splits.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":29.172,"exit_code":1,"observations":[{"actual":[[1,9],"eos"],"check":"eos middle","expected":[[1],"eos"],"passed":false},{"actual":[[9],"eos"],"check":"eos first","expected":[[],"eos"],"passed":false},{"actual":[[1,2],null],"check":"absent","expected":[[1,2],null],"passed":true},{"actual":[[],null],"check":"empty","expected":[[],null],"passed":true},{"actual":[[1,9],"eos"],"check":"repeated eos","expected":[[1],"eos"],"passed":false},{"actual":[[2,0],"eos"],"check":"zero eos valid","expected":[[2],"eos"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"eos middle\", \"actual\": [[1, 9], \"eos\"], \"expected\": [[1], \"eos\"], \"passed\": false}, {\"check\": \"eos first\", \"actual\": [[9], \"eos\"], \"expected\": [[], \"eos\"], \"passed\": false}, {\"check\": \"absent\", \"actual\": [[1, 2], null], \"expected\": [[1, 2], null], \"passed\": true}, {\"check\": \"empty\", \"actual\": [[], null], \"expected\": [[], null], \"passed\": true}, {\"check\": \"repeated eos\", \"actual\": [[1, 9], \"eos\"], \"expected\": [[1], \"eos\"], \"passed\": false}, {\"check\": \"zero eos valid\", \"actual\": [[2, 0], \"eos\"], \"expected\": [[2], \"eos\"], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":33.137,"exit_code":1,"observations":[{"actual":[[1,9,2],"eos"],"check":"eos middle","expected":[[1],"eos"],"passed":false},{"actual":[[9],"eos"],"check":"eos first","expected":[[],"eos"],"passed":false},{"actual":[[1,2],null],"check":"absent","expected":[[1,2],null],"passed":true},{"actual":[[],null],"check":"empty","expected":[[],null],"passed":true},{"actual":[[1,9,9],"eos"],"check":"repeated eos","expected":[[1],"eos"],"passed":false},{"actual":[[2,0,3],"eos"],"check":"zero eos valid","expected":[[2],"eos"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"eos middle\", \"actual\": [[1, 9, 2], \"eos\"], \"expected\": [[1], \"eos\"], \"passed\": false}, {\"check\": \"eos first\", \"actual\": [[9], \"eos\"], \"expected\": [[], \"eos\"], \"passed\": false}, {\"check\": \"absent\", \"actual\": [[1, 2], null], \"expected\": [[1, 2], null], \"passed\": true}, {\"check\": \"empty\", \"actual\": [[], null], \"expected\": [[], null], \"passed\": true}, {\"check\": \"repeated eos\", \"actual\": [[1, 9, 9], \"eos\"], \"expected\": [[1], \"eos\"], \"passed\": false}, {\"check\": \"zero eos valid\", \"actual\": [[2, 0, 3], \"eos\"], \"expected\": [[2], \"eos\"], \"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."}}