{"abstract":"UTF-16 code units are interpreted as Unicode scalars.","category":"Encodings","checks":4,"contract":"Decode little-endian UTF-16 code units to text with replacement for unpaired surrogates.","evaluation_group":"model-3bec5d94a4a5a275","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-utf16-surrogate-pair","id":"FA-3926","implementations":{"attempt":{"sha256":"72392a0734b08099d9cb584846ad6c761ece129ef0014078b19a6e40ed9cfa57","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(v.to_bytes(2,'little').decode('utf-16-le','replace') 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([55357, 56832]), '😀')\ncheck('boundary 2', solve([55296]), '�')\ncheck('boundary 3', solve([65]), 'A')\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":"df47615848fb3b84c07a8be5a003f721bfa1975f9bb86adf676055584413d7bd","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(chr(v) for v in x).encode('utf-8','replace').decode()\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([55357, 56832]), '😀')\ncheck('boundary 2', solve([55296]), '�')\ncheck('boundary 3', solve([65]), 'A')\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"},"fixed":{"sha256":"4599cedf5bf1bfff10286cf1ff73610b099c59f44f51db3757b95a3434044a2c","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 b''.join(v.to_bytes(2,'little') for v in x).decode('utf-16-le','replace')\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([55357, 56832]), '😀')\ncheck('boundary 2', solve([55296]), '�')\ncheck('boundary 3', solve([65]), 'A')\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-utf16-surrogate-pair","generated_at":"2026-09-29T14:37:33.084172+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 little-endian UTF-16 code units to text with replacement for unpaired surrogates.","root_cause":"The implementation applies an operation whose text or grammar semantics violate this contract: Decode little-endian UTF-16 code units to text with replacement for unpaired surrogates.","sha256":"0b8d91e0edee7c1a5bdacbbc238fca1b0c113d54100151652730bbe309c76381","title":"UTF-16 code units are interpreted as Unicode scalars · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":54.874,"exit_code":1,"observations":[{"actual":"��","check":"boundary 1","expected":"😀","passed":false},{"actual":"�","check":"boundary 2","expected":"�","passed":true},{"actual":"A","check":"boundary 3","expected":"A","passed":true},{"actual":"","check":"boundary 4","expected":"","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": \"��\", \"expected\": \"😀\", \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": \"�\", \"expected\": \"�\", \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": \"A\", \"expected\": \"A\", \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":64.267,"exit_code":1,"observations":[{"actual":"??","check":"boundary 1","expected":"😀","passed":false},{"actual":"?","check":"boundary 2","expected":"�","passed":false},{"actual":"A","check":"boundary 3","expected":"A","passed":true},{"actual":"","check":"boundary 4","expected":"","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": \"??\", \"expected\": \"😀\", \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": \"?\", \"expected\": \"�\", \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": \"A\", \"expected\": \"A\", \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":144.73,"exit_code":0,"observations":[{"actual":"😀","check":"boundary 1","expected":"😀","passed":true},{"actual":"�","check":"boundary 2","expected":"�","passed":true},{"actual":"A","check":"boundary 3","expected":"A","passed":true},{"actual":"","check":"boundary 4","expected":"","passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": \"😀\", \"expected\": \"😀\", \"passed\": true}, {\"check\": \"boundary 2\", \"actual\": \"�\", \"expected\": \"�\", \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": \"A\", \"expected\": \"A\", \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}