{"abstract":"Hex nybbles are swapped within each byte.","category":"Binary formats","checks":4,"contract":"Expand bytes to high then low nybbles.","contract_signature":"x","evaluation_group":"model-3c70c5b5f42644df","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-binary-nibble-order","id":"FA-3691","implementations":{"attempt":{"sha256":"f97312776e1a55a1bc784e6a294219a596f0e2b6cc1cdb9155a0dcf2be7d7f36","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 [v>>4 for v in x]+[v&15 for v in 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([18, 52]), [1, 2, 3, 4])\ncheck('boundary 2', solve([255]), [15, 15])\ncheck('boundary 3', solve([0]), [0, 0])\ncheck('boundary 4', solve([]), [])\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":"bf96f271dfd66545f32c357b348113dda3e9af732cfba96488a41fca91b42df5","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 [n for v in x for n in (v&15,v>>4)]\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([18, 52]), [1, 2, 3, 4])\ncheck('boundary 2', solve([255]), [15, 15])\ncheck('boundary 3', solve([0]), [0, 0])\ncheck('boundary 4', solve([]), [])\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-nibble-order","generated_at":"2026-09-29T14:37:29.507980+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: Expand bytes to high then low nybbles.","sha256":"7230ce59d609ea793ab48c0f3fb421ba8523b04b0cdc28418d17ce9f598e470c","title":"Hex nybbles are swapped within each byte · 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":148.077,"exit_code":1,"observations":[{"actual":[1,3,2,4],"check":"boundary 1","expected":[1,2,3,4],"passed":false},{"actual":[15,15],"check":"boundary 2","expected":[15,15],"passed":true},{"actual":[0,0],"check":"boundary 3","expected":[0,0],"passed":true},{"actual":[],"check":"boundary 4","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [1, 3, 2, 4], \"expected\": [1, 2, 3, 4], \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": [15, 15], \"expected\": [15, 15], \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": [0, 0], \"expected\": [0, 0], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":58.513,"exit_code":1,"observations":[{"actual":[2,1,4,3],"check":"boundary 1","expected":[1,2,3,4],"passed":false},{"actual":[15,15],"check":"boundary 2","expected":[15,15],"passed":true},{"actual":[0,0],"check":"boundary 3","expected":[0,0],"passed":true},{"actual":[],"check":"boundary 4","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [2, 1, 4, 3], \"expected\": [1, 2, 3, 4], \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": [15, 15], \"expected\": [15, 15], \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": [0, 0], \"expected\": [0, 0], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [], \"expected\": [], \"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."}}