{"abstract":"Dns edns fallback removes extension after format error only.","category":"DNS resolution","checks":4,"contract":"Bounded offline decision model: dns edns fallback removes extension after format error only. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","contract_signature":"edns, rcode","evaluation_group":"xh-dns-edns-fallback-removes-extension-after-format-error-only","failed_approach":"The attempted repair uses `rcode == 1` and still violates a separate fixture.","family":"xh-dns-edns-fallback-removes-extension-after-format-error-only","id":"FA-7431","implementations":{"attempt":{"sha256":"308e2f6e3847f0d2265237cd9ceba807f9d03822ccb41facb6a1de1c982a0852","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(edns, rcode):\n    return rcode == 1\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(True, 1), True)\", \"check('fixture 2', solve(True, 3), False)\", \"check('fixture 3', solve(False, 1), False)\", \"check('fixture 4', solve(False, 0), False)\"]\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":"0b23aebb15cb884b98c6a31d3cedd8a3729c0fe678e35e44cc61a07567955e7d","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(edns, rcode):\n    return edns\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(True, 1), True)\", \"check('fixture 2', solve(True, 3), False)\", \"check('fixture 3', solve(False, 1), False)\", \"check('fixture 4', solve(False, 0), False)\"]\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-edns-fallback-removes-extension-after-format-error-only","generated_at":"2026-09-29T14:38:11.914640+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic dns resolution model isolates the dns-edns-fallback-removes-extension-after-format-error-only policy at a network component boundary.","root_cause":"The faulty implementation uses `edns` for the dns-edns-fallback-removes-extension-after-format-error-only decision.","sha256":"bcf112bcffbe6e8a997b27424ac28e5c53e35605b4314e07e520b9e0d2992736","title":"Dns edns fallback removes extension after format error only · 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":49.071,"exit_code":1,"observations":[{"actual":false,"check":"fixture 2","expected":false,"passed":true},{"actual":true,"check":"fixture 3","expected":false,"passed":false},{"actual":false,"check":"fixture 4","expected":false,"passed":true},{"actual":true,"check":"fixture 1","expected":true,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"fixture 4\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": true, \"expected\": true, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":46.176,"exit_code":1,"observations":[{"actual":true,"check":"fixture 2","expected":false,"passed":false},{"actual":false,"check":"fixture 3","expected":false,"passed":true},{"actual":false,"check":"fixture 4","expected":false,"passed":true},{"actual":true,"check":"fixture 1","expected":true,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": true, \"expected\": true, \"passed\": true}], \"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."}}