{"abstract":"A replacement repeats until newly created matches disappear.","category":"Text processing","checks":4,"contract":"Perform one left-to-right nonoverlapping replacement pass of aa to a.","evaluation_group":"model-9ab33eda792360c0","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-overlapping-rewrite-once","id":"FA-3961","implementations":{"attempt":{"sha256":"e839d97eb8a67ed30a3979055fc55e95a670dc9fd9ee407e2800732a399fb43d","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 re.sub('a+','a',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('aaaa'), 'aa')\ncheck('boundary 2', solve('aaa'), 'aa')\ncheck('boundary 3', solve('aba'), 'aba')\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":"a9f207eb59a211deee671445d520563dad4d9367243c51d8f4e568c60d40653d","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.replace('aa','a').replace('aa','a')\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('aaaa'), 'aa')\ncheck('boundary 2', solve('aaa'), 'aa')\ncheck('boundary 3', solve('aba'), 'aba')\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":"9b4c316fa6973c8a367fe492627546e8cf26b024181ad1bcf9cb0f26443ead27","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.replace('aa','a')\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('aaaa'), 'aa')\ncheck('boundary 2', solve('aaa'), 'aa')\ncheck('boundary 3', solve('aba'), 'aba')\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-overlapping-rewrite-once","generated_at":"2026-09-29T14:37:33.569483+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: Perform one left-to-right nonoverlapping replacement pass of aa to a.","root_cause":"The implementation applies an operation whose text or grammar semantics violate this contract: Perform one left-to-right nonoverlapping replacement pass of aa to a.","sha256":"30ecb2ee0cafb1acd3d84abd8aa365cdff4e97cbdc16f86bff80310603226507","title":"A replacement repeats until newly created matches disappear · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":166.029,"exit_code":1,"observations":[{"actual":"a","check":"boundary 1","expected":"aa","passed":false},{"actual":"a","check":"boundary 2","expected":"aa","passed":false},{"actual":"aba","check":"boundary 3","expected":"aba","passed":true},{"actual":"","check":"boundary 4","expected":"","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": \"a\", \"expected\": \"aa\", \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": \"a\", \"expected\": \"aa\", \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": \"aba\", \"expected\": \"aba\", \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":54.73,"exit_code":1,"observations":[{"actual":"a","check":"boundary 1","expected":"aa","passed":false},{"actual":"a","check":"boundary 2","expected":"aa","passed":false},{"actual":"aba","check":"boundary 3","expected":"aba","passed":true},{"actual":"","check":"boundary 4","expected":"","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": \"a\", \"expected\": \"aa\", \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": \"a\", \"expected\": \"aa\", \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": \"aba\", \"expected\": \"aba\", \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":61.718,"exit_code":0,"observations":[{"actual":"aa","check":"boundary 1","expected":"aa","passed":true},{"actual":"aa","check":"boundary 2","expected":"aa","passed":true},{"actual":"aba","check":"boundary 3","expected":"aba","passed":true},{"actual":"","check":"boundary 4","expected":"","passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": \"aa\", \"expected\": \"aa\", \"passed\": true}, {\"check\": \"boundary 2\", \"actual\": \"aa\", \"expected\": \"aa\", \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": \"aba\", \"expected\": \"aba\", \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}