{"abstract":"A byte-count prefix is trusted without checking body size.","category":"Binary formats","checks":4,"contract":"Decode one-byte length and exact payload; return payload bytes or None.","evaluation_group":"model-6ab73a6a81290ebc","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-binary-length-prefix","id":"FA-3661","implementations":{"attempt":{"sha256":"f663d2fad6143fa95f13963491247b61cdd9a7afdf28cf6739102193e3705c2a","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct\nfrom urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit\nfrom email.header import decode_header, make_header\nfrom email.utils import getaddresses\nfrom xml.etree import ElementTree as ET\nimport shlex, string, textwrap\n\nN = 1\nobservations = []\ndef solve(x):\n    try:\n        return x[1:1+x[0]] if x else None\n    except Exception as exc:\n        return {\"error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('boundary 1', solve([2, 65]), None)\ncheck('boundary 2', solve([1, 65, 66]), None)\ncheck('boundary 3', solve([2, 65, 66]), [65, 66])\ncheck('boundary 4', solve([0]), [])\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":"60d658fdacc94d2ff078bb6b14d1012e0017717f777c437e14f0cf729d025e86","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct\nfrom urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit\nfrom email.header import decode_header, make_header\nfrom email.utils import getaddresses\nfrom xml.etree import ElementTree as ET\nimport shlex, string, textwrap\n\nN = 1\nobservations = []\ndef solve(x):\n    try:\n        return x[1:]\n    except Exception as exc:\n        return {\"error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('boundary 1', solve([2, 65]), None)\ncheck('boundary 2', solve([1, 65, 66]), None)\ncheck('boundary 3', solve([2, 65, 66]), [65, 66])\ncheck('boundary 4', solve([0]), [])\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"},"fixed":{"sha256":"7f8bd3999a8ac538ffb72b6d539abc16077a5cf4db4fb3b872f5b45c920bbdd3","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct\nfrom urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit\nfrom email.header import decode_header, make_header\nfrom email.utils import getaddresses\nfrom xml.etree import ElementTree as ET\nimport shlex, string, textwrap\n\nN = 1\nobservations = []\ndef solve(x):\n    try:\n        return x[1:] if x and len(x)==x[0]+1 else None\n    except Exception as exc:\n        return {\"error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('boundary 1', solve([2, 65]), None)\ncheck('boundary 2', solve([1, 65, 66]), None)\ncheck('boundary 3', solve([2, 65, 66]), [65, 66])\ncheck('boundary 4', solve([0]), [])\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 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":"xp-binary-length-prefix","generated_at":"2026-09-29T14:37:29.171659+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A local executable model for consumers of structured text; oracle values are authored literals, not outputs copied from the repaired implementation.","repair":"Implement the complete stated contract, including the boundary fixtures: Decode one-byte length and exact payload; return payload bytes or None.","root_cause":"The implementation applies an operation whose text or grammar semantics violate this contract: Decode one-byte length and exact payload; return payload bytes or None.","sha256":"d2218664eeb15912d6f9e0e467e3f316e124bf61c07c34004097e94757e5a207","title":"A byte-count prefix is trusted without checking body size · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":51.047,"exit_code":1,"observations":[{"actual":[65],"check":"boundary 1","expected":null,"passed":false},{"actual":[65],"check":"boundary 2","expected":null,"passed":false},{"actual":[65,66],"check":"boundary 3","expected":[65,66],"passed":true},{"actual":[],"check":"boundary 4","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [65], \"expected\": null, \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": [65], \"expected\": null, \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": [65, 66], \"expected\": [65, 66], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":53.405,"exit_code":1,"observations":[{"actual":[65],"check":"boundary 1","expected":null,"passed":false},{"actual":[65,66],"check":"boundary 2","expected":null,"passed":false},{"actual":[65,66],"check":"boundary 3","expected":[65,66],"passed":true},{"actual":[],"check":"boundary 4","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [65], \"expected\": null, \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": [65, 66], \"expected\": null, \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": [65, 66], \"expected\": [65, 66], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":51.712,"exit_code":0,"observations":[{"actual":null,"check":"boundary 1","expected":null,"passed":true},{"actual":null,"check":"boundary 2","expected":null,"passed":true},{"actual":[65,66],"check":"boundary 3","expected":[65,66],"passed":true},{"actual":[],"check":"boundary 4","expected":[],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"boundary 2\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": [65, 66], \"expected\": [65, 66], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}