{"abstract":"COBS decoding inserts a zero after the final block.","category":"Binary formats","checks":6,"contract":"Decode COBS code blocks to bytes; insert an implied zero only between blocks with code below 255. Reject zero code or truncation.","contract_signature":"x","evaluation_group":"model-c80d81bf074896b3","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-cobs-interblock-zero","id":"FA-4076","implementations":{"attempt":{"sha256":"41e4eb6a6087648e41db4653e4210b8e6581847492d33337bc5c68f778e14970","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        out=[]\n        i=0\n        while i<len(x):\n            c=x[i]\n            if not c or i+c>len(x): return None\n            out.extend(x[i+1:i+c])\n            if c<255: out.append(0)\n            i+=c\n        return out\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, 2, 66]), [65, 0, 66])\ncheck('boundary 2', solve([1]), [])\ncheck('boundary 3', solve([2, 65]), [65])\ncheck('boundary 4', solve([0]), None)\ncheck('boundary 5', solve([3, 65]), None)\ncheck('boundary 6', solve([2, 0]), None)\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":"c638045dd92795dda29989256ca95daf797d71bb6dbb89a14aa23ef22a8de7dd","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, 2, 66]), [65, 0, 66])\ncheck('boundary 2', solve([1]), [])\ncheck('boundary 3', solve([2, 65]), [65])\ncheck('boundary 4', solve([0]), None)\ncheck('boundary 5', solve([3, 65]), None)\ncheck('boundary 6', solve([2, 0]), None)\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-cobs-interblock-zero","generated_at":"2026-09-29T14:37:35.462826+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.","root_cause":"The implementation applies an operation whose text or grammar semantics violate this contract: Decode COBS code blocks to bytes; insert an implied zero only between blocks with code below 255. Reject zero code or truncation.","sha256":"aa5fb513fdae34f9573b5b6bb3231c9551913520634adbcc3f1bd49a9e23185c","title":"COBS decoding inserts a zero after the final block · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":56.611,"exit_code":1,"observations":[{"actual":[65,0,66,0],"check":"boundary 1","expected":[65,0,66],"passed":false},{"actual":[0],"check":"boundary 2","expected":[],"passed":false},{"actual":[65,0],"check":"boundary 3","expected":[65],"passed":false},{"actual":null,"check":"boundary 4","expected":null,"passed":true},{"actual":null,"check":"boundary 5","expected":null,"passed":true},{"actual":[0,0],"check":"boundary 6","expected":null,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [65, 0, 66, 0], \"expected\": [65, 0, 66], \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": [0], \"expected\": [], \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": [65, 0], \"expected\": [65], \"passed\": false}, {\"check\": \"boundary 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"boundary 5\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"boundary 6\", \"actual\": [0, 0], \"expected\": null, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":150.242,"exit_code":1,"observations":[{"actual":[65,2,66],"check":"boundary 1","expected":[65,0,66],"passed":false},{"actual":[],"check":"boundary 2","expected":[],"passed":true},{"actual":[65],"check":"boundary 3","expected":[65],"passed":true},{"actual":[],"check":"boundary 4","expected":null,"passed":false},{"actual":[65],"check":"boundary 5","expected":null,"passed":false},{"actual":[0],"check":"boundary 6","expected":null,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [65, 2, 66], \"expected\": [65, 0, 66], \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": [65], \"expected\": [65], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [], \"expected\": null, \"passed\": false}, {\"check\": \"boundary 5\", \"actual\": [65], \"expected\": null, \"passed\": false}, {\"check\": \"boundary 6\", \"actual\": [0], \"expected\": null, \"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."}}