{"abstract":"A sign-magnitude octet is decoded as two-complement.","category":"Binary formats","checks":4,"contract":"Decode high-bit sign and seven-bit magnitude, with either zero representation mapping to zero.","contract_signature":"x","evaluation_group":"model-661c01d144df5a43","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-binary-sign-magnitude","id":"FA-3616","implementations":{"attempt":{"sha256":"11fa1c16a791ed4cb7c407407a691e4112df4d0e4c68fc3ae5c27660ef79f817","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 if x>=128 else x\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(129), -1)\ncheck('boundary 2', solve(255), -127)\ncheck('boundary 3', solve(128), 0)\ncheck('boundary 4', solve(7), 7)\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":"287ecb6231b58f4d0412e4cccc77b76c26d567230e15a3b26be58409c1696f0d","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-256 if x>=128 else x\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(129), -1)\ncheck('boundary 2', solve(255), -127)\ncheck('boundary 3', solve(128), 0)\ncheck('boundary 4', solve(7), 7)\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-sign-magnitude","generated_at":"2026-09-29T14:37:28.426622+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 high-bit sign and seven-bit magnitude, with either zero representation mapping to zero.","sha256":"31e8f6196abcd58f4f3d9f687ba36a35ef19283b6e322cd0962c40da00560ddf","title":"A sign-magnitude octet is decoded as two-complement · 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":60.412,"exit_code":1,"observations":[{"actual":-129,"check":"boundary 1","expected":-1,"passed":false},{"actual":-255,"check":"boundary 2","expected":-127,"passed":false},{"actual":-128,"check":"boundary 3","expected":0,"passed":false},{"actual":7,"check":"boundary 4","expected":7,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": -129, \"expected\": -1, \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": -255, \"expected\": -127, \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": -128, \"expected\": 0, \"passed\": false}, {\"check\": \"boundary 4\", \"actual\": 7, \"expected\": 7, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":57.627,"exit_code":1,"observations":[{"actual":-127,"check":"boundary 1","expected":-1,"passed":false},{"actual":-1,"check":"boundary 2","expected":-127,"passed":false},{"actual":-128,"check":"boundary 3","expected":0,"passed":false},{"actual":7,"check":"boundary 4","expected":7,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": -127, \"expected\": -1, \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": -1, \"expected\": -127, \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": -128, \"expected\": 0, \"passed\": false}, {\"check\": \"boundary 4\", \"actual\": 7, \"expected\": 7, \"passed\": true}], \"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."}}