{"abstract":"Hex formatting places a separator between nybbles.","category":"Binary formats","checks":4,"contract":"Format bytes as lowercase two-digit hex groups separated by one colon; empty input empty.","contract_signature":"x","evaluation_group":"model-03e843efe18d69ef","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-hex-separator-grouping","id":"FA-4036","implementations":{"attempt":{"sha256":"25b8896dc8bb2ca5a2d21c73344ec0356a05d8b1f120dff771484e0deae82395","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 ':'.join(format(v,'x') 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([0, 10, 255]), '00:0a:ff')\ncheck('boundary 2', solve([16]), '10')\ncheck('boundary 3', solve([]), '')\ncheck('boundary 4', solve([1, 2]), '01:02')\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":"09318218cf917aa9e18023d69ca5ece4675a81ee74e2a70de9394a9d543d6953","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 ':'.join(bytes(x).hex())\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([0, 10, 255]), '00:0a:ff')\ncheck('boundary 2', solve([16]), '10')\ncheck('boundary 3', solve([]), '')\ncheck('boundary 4', solve([1, 2]), '01:02')\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-hex-separator-grouping","generated_at":"2026-09-29T14:37:34.633744+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: Format bytes as lowercase two-digit hex groups separated by one colon; empty input empty.","sha256":"338237c96eb2e4c8dbd921e505c7eae9280081c7248def4f0540b0de571c5928","title":"Hex formatting places a separator between nybbles · 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":65.715,"exit_code":1,"observations":[{"actual":"0:a:ff","check":"boundary 1","expected":"00:0a:ff","passed":false},{"actual":"10","check":"boundary 2","expected":"10","passed":true},{"actual":"","check":"boundary 3","expected":"","passed":true},{"actual":"1:2","check":"boundary 4","expected":"01:02","passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": \"0:a:ff\", \"expected\": \"00:0a:ff\", \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": \"10\", \"expected\": \"10\", \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": \"1:2\", \"expected\": \"01:02\", \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":58.861,"exit_code":1,"observations":[{"actual":"0:0:0:a:f:f","check":"boundary 1","expected":"00:0a:ff","passed":false},{"actual":"1:0","check":"boundary 2","expected":"10","passed":false},{"actual":"","check":"boundary 3","expected":"","passed":true},{"actual":"0:1:0:2","check":"boundary 4","expected":"01:02","passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": \"0:0:0:a:f:f\", \"expected\": \"00:0a:ff\", \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": \"1:0\", \"expected\": \"10\", \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": \"0:1:0:2\", \"expected\": \"01:02\", \"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."}}