{"abstract":"Zigzag decoding loses odd-value signs.","category":"Binary formats","checks":4,"contract":"Decode a nonnegative ZigZag integer to its signed integer.","evaluation_group":"model-5fd5d9f6519c0ab4","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-binary-zigzag","id":"FA-3621","implementations":{"attempt":{"sha256":"bea41d4507264cb471d358a8ad818b2da3256536642cc2710c6b7a660b01ed2d","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//2) if x&1 else x//2\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(1), -1)\ncheck('boundary 2', solve(3), -2)\ncheck('boundary 3', solve(2), 1)\ncheck('boundary 4', solve(0), 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":"d1c57cfd2d9c64cb4566f2876fa2b1b435db848507a84fc4c6880fe762d934a1","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//2\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(1), -1)\ncheck('boundary 2', solve(3), -2)\ncheck('boundary 3', solve(2), 1)\ncheck('boundary 4', solve(0), 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":"cffd15d08c92277ba67ecfdddb265cba36715680ad0315435945529477304c8c","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)^-(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(1), -1)\ncheck('boundary 2', solve(3), -2)\ncheck('boundary 3', solve(2), 1)\ncheck('boundary 4', solve(0), 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-zigzag","generated_at":"2026-09-29T14:37:28.427757+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 a nonnegative ZigZag integer to its signed integer.","root_cause":"The implementation applies an operation whose text or grammar semantics violate this contract: Decode a nonnegative ZigZag integer to its signed integer.","sha256":"1109eedae8c9639bf0ae8b26c2352f9ce4c1e2b021c1b777346d41d2c5c0084a","title":"Zigzag decoding loses odd-value signs · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":55.986,"exit_code":1,"observations":[{"actual":0,"check":"boundary 1","expected":-1,"passed":false},{"actual":-1,"check":"boundary 2","expected":-2,"passed":false},{"actual":1,"check":"boundary 3","expected":1,"passed":true},{"actual":0,"check":"boundary 4","expected":0,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": 0, \"expected\": -1, \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": -1, \"expected\": -2, \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": 0, \"expected\": 0, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":59.534,"exit_code":1,"observations":[{"actual":0,"check":"boundary 1","expected":-1,"passed":false},{"actual":1,"check":"boundary 2","expected":-2,"passed":false},{"actual":1,"check":"boundary 3","expected":1,"passed":true},{"actual":0,"check":"boundary 4","expected":0,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": 0, \"expected\": -1, \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": 1, \"expected\": -2, \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": 0, \"expected\": 0, \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":52.193,"exit_code":0,"observations":[{"actual":-1,"check":"boundary 1","expected":-1,"passed":true},{"actual":-2,"check":"boundary 2","expected":-2,"passed":true},{"actual":1,"check":"boundary 3","expected":1,"passed":true},{"actual":0,"check":"boundary 4","expected":0,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": -1, \"expected\": -1, \"passed\": true}, {\"check\": \"boundary 2\", \"actual\": -2, \"expected\": -2, \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": 0, \"expected\": 0, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}