{"abstract":"Dns nxdomain is distinct from empty noerror answer.","category":"DNS resolution","checks":4,"contract":"Bounded offline decision model: dns nxdomain is distinct from empty noerror answer. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","evaluation_group":"xh-dns-nxdomain-is-distinct-from-empty-noerror-answer","failed_approach":"The attempted repair uses `'nodata' if not answers else 'answer'` and still violates a separate fixture.","family":"xh-dns-nxdomain-is-distinct-from-empty-noerror-answer","id":"FA-7346","implementations":{"attempt":{"sha256":"e88ef6548d67cf2afbe709c324f9596fa35bc90f837483ec3e24ddadd121197b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport ipaddress\nimport re\nfrom urllib.parse import urlsplit, urljoin\nN = 1\nobservations = []\ndef solve(rcode, answers):\n    return 'nodata' if not answers else 'answer'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(3, []), 'name-error')\", \"check('fixture 2', solve(0, []), 'nodata')\", \"check('fixture 3', solve(0, ['a']), 'answer')\", \"check('fixture 4', solve(3, ['a']), 'name-error')\"]\nfor _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:\n    exec(_line)\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":"5934c78c0a8b5ae1a5311149f7b90a4d9ea55850988ebb17d9569e5e1c63c1c4","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport ipaddress\nimport re\nfrom urllib.parse import urlsplit, urljoin\nN = 1\nobservations = []\ndef solve(rcode, answers):\n    return 'name-error' if not answers else 'answer'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(3, []), 'name-error')\", \"check('fixture 2', solve(0, []), 'nodata')\", \"check('fixture 3', solve(0, ['a']), 'answer')\", \"check('fixture 4', solve(3, ['a']), 'name-error')\"]\nfor _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:\n    exec(_line)\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":"3d8184793b4c2d2e7e40cfe3f3bd45024f5b154f24f226dda6678f6826afa4a8","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport ipaddress\nimport re\nfrom urllib.parse import urlsplit, urljoin\nN = 1\nobservations = []\ndef solve(rcode, answers):\n    return 'name-error' if rcode == 3 else ('answer' if answers else 'nodata')\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(3, []), 'name-error')\", \"check('fixture 2', solve(0, []), 'nodata')\", \"check('fixture 3', solve(0, ['a']), 'answer')\", \"check('fixture 4', solve(3, ['a']), 'name-error')\"]\nfor _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:\n    exec(_line)\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":"Bounded deterministic policy model over validated inputs; not a complete protocol stack or an interoperability claim. The five variants rotate the same explicit fixture set. 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":"xh-dns-nxdomain-is-distinct-from-empty-noerror-answer","generated_at":"2026-09-29T14:38:10.903374+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic dns resolution model isolates the dns-nxdomain-is-distinct-from-empty-noerror-answer policy at a network component boundary.","repair":"Apply the explicit dns-nxdomain-is-distinct-from-empty-noerror-answer contract, including the tested boundary and negative cases.","root_cause":"The faulty implementation uses `'name-error' if not answers else 'answer'` for the dns-nxdomain-is-distinct-from-empty-noerror-answer decision.","sha256":"377116ec9992f68635b1a47ddf4de6f0c94e8ca9e27b431888440bb997bd8e9b","title":"Dns nxdomain is distinct from empty noerror answer · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":45.884,"exit_code":1,"observations":[{"actual":"nodata","check":"fixture 2","expected":"nodata","passed":true},{"actual":"answer","check":"fixture 3","expected":"answer","passed":true},{"actual":"answer","check":"fixture 4","expected":"name-error","passed":false},{"actual":"nodata","check":"fixture 1","expected":"name-error","passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": \"nodata\", \"expected\": \"nodata\", \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": \"answer\", \"expected\": \"answer\", \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": \"answer\", \"expected\": \"name-error\", \"passed\": false}, {\"check\": \"fixture 1\", \"actual\": \"nodata\", \"expected\": \"name-error\", \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":44.72,"exit_code":1,"observations":[{"actual":"name-error","check":"fixture 2","expected":"nodata","passed":false},{"actual":"answer","check":"fixture 3","expected":"answer","passed":true},{"actual":"answer","check":"fixture 4","expected":"name-error","passed":false},{"actual":"name-error","check":"fixture 1","expected":"name-error","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": \"name-error\", \"expected\": \"nodata\", \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": \"answer\", \"expected\": \"answer\", \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": \"answer\", \"expected\": \"name-error\", \"passed\": false}, {\"check\": \"fixture 1\", \"actual\": \"name-error\", \"expected\": \"name-error\", \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":46.072,"exit_code":0,"observations":[{"actual":"nodata","check":"fixture 2","expected":"nodata","passed":true},{"actual":"answer","check":"fixture 3","expected":"answer","passed":true},{"actual":"name-error","check":"fixture 4","expected":"name-error","passed":true},{"actual":"name-error","check":"fixture 1","expected":"name-error","passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": \"nodata\", \"expected\": \"nodata\", \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": \"answer\", \"expected\": \"answer\", \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": \"name-error\", \"expected\": \"name-error\", \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": \"name-error\", \"expected\": \"name-error\", \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}