{"abstract":"Base64 decoding silently ignores foreign characters.","category":"Encodings","checks":4,"contract":"Decode canonical standard alphabet base64 with validation; invalid input returns None.","evaluation_group":"model-fab8613370701069","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-base64-strict-junk","id":"FA-3306","implementations":{"attempt":{"sha256":"2ef2f37c8002f3f267b6a15fc63828789322163efdac61cbd5252bd513319d0c","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 list(base64.b64decode(x.replace(' ','').replace('\\n','')))\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('Y Q=='), None)\ncheck('boundary 2', solve('YQ==\\n'), None)\ncheck('boundary 3', solve('YQ=='), [97])\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":"35dfa0ad7c9e1bea36dfd49daf2310bdbca045f753b67b44290ed8cbb9102f5f","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 list(base64.b64decode(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('Y Q=='), None)\ncheck('boundary 2', solve('YQ==\\n'), None)\ncheck('boundary 3', solve('YQ=='), [97])\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":"014622123e1bf1d581356729ba552196eb6b6036b37b47ed96e0d0affa4ae1b9","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        try:\n            return list(base64.b64decode(x,validate=True))\n        except (ValueError,binascii.Error):\n            return None\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('Y Q=='), None)\ncheck('boundary 2', solve('YQ==\\n'), None)\ncheck('boundary 3', solve('YQ=='), [97])\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-base64-strict-junk","generated_at":"2026-09-29T14:37:24.057387+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 canonical standard alphabet base64 with validation; invalid input returns None.","root_cause":"The implementation applies an operation whose text or grammar semantics violate this contract: Decode canonical standard alphabet base64 with validation; invalid input returns None.","sha256":"79295bdcbc98a5c2027a8a7b545bf337cc21317cfb49e06af3f0e19005f6b84b","title":"Base64 decoding silently ignores foreign characters · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":61.981,"exit_code":1,"observations":[{"actual":[97],"check":"boundary 1","expected":null,"passed":false},{"actual":[97],"check":"boundary 2","expected":null,"passed":false},{"actual":[97],"check":"boundary 3","expected":[97],"passed":true},{"actual":[],"check":"boundary 4","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [97], \"expected\": null, \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": [97], \"expected\": null, \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": [97], \"expected\": [97], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":53.071,"exit_code":1,"observations":[{"actual":[97],"check":"boundary 1","expected":null,"passed":false},{"actual":[97],"check":"boundary 2","expected":null,"passed":false},{"actual":[97],"check":"boundary 3","expected":[97],"passed":true},{"actual":[],"check":"boundary 4","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [97], \"expected\": null, \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": [97], \"expected\": null, \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": [97], \"expected\": [97], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":60.653,"exit_code":0,"observations":[{"actual":null,"check":"boundary 1","expected":null,"passed":true},{"actual":null,"check":"boundary 2","expected":null,"passed":true},{"actual":[97],"check":"boundary 3","expected":[97],"passed":true},{"actual":[],"check":"boundary 4","expected":[],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"boundary 2\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": [97], \"expected\": [97], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}