{"abstract":"Response trailers exclude forbidden routing fields.","category":"Proxy forwarding","checks":4,"contract":"Bounded offline decision model: response trailers exclude forbidden routing fields. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","contract_signature":"trailers","evaluation_group":"xh-response-trailers-exclude-forbidden-routing-fields","failed_approach":"The attempted repair uses `{k:v for k,v in trailers.items() if k not in {\"host\",\"content-length\",\"transfer-encoding\"}}` and still violates a separate fixture.","family":"xh-response-trailers-exclude-forbidden-routing-fields","id":"FA-7036","implementations":{"attempt":{"sha256":"87784d99c61f77ebc8cde0695bcaa0f17d2fbff30ff2e636267390799ca586bc","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(trailers):\n    return {k:v for k,v in trailers.items() if k not in {\"host\",\"content-length\",\"transfer-encoding\"}}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve({'Host': 'x', 'Digest': 'd'}), {'Digest': 'd'})\", \"check('fixture 2', solve({'content-length': '2'}), {})\", \"check('fixture 3', solve({}), {})\", \"check('fixture 4', solve({'checksum': 'a'}), {'checksum': 'a'})\"]\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":"ef47043380dbbbc6eeaf0069af181b7fcb98e69eabec8d12e2eed78abf65828b","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(trailers):\n    return trailers\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve({'Host': 'x', 'Digest': 'd'}), {'Digest': 'd'})\", \"check('fixture 2', solve({'content-length': '2'}), {})\", \"check('fixture 3', solve({}), {})\", \"check('fixture 4', solve({'checksum': 'a'}), {'checksum': 'a'})\"]\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-response-trailers-exclude-forbidden-routing-fields","generated_at":"2026-09-29T14:38:07.805101+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic proxy forwarding model isolates the response-trailers-exclude-forbidden-routing-fields policy at a network component boundary.","root_cause":"The faulty implementation uses `trailers` for the response-trailers-exclude-forbidden-routing-fields decision.","sha256":"4449ae584bbf3cd844686659ac0fe3a22a2a569fd6d7fa12438beb4c72072426","title":"Response trailers exclude forbidden routing fields · 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":38.023,"exit_code":1,"observations":[{"actual":{},"check":"fixture 2","expected":{},"passed":true},{"actual":{},"check":"fixture 3","expected":{},"passed":true},{"actual":{"checksum":"a"},"check":"fixture 4","expected":{"checksum":"a"},"passed":true},{"actual":{"Digest":"d","Host":"x"},"check":"fixture 1","expected":{"Digest":"d"},"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": {}, \"expected\": {}, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": {}, \"expected\": {}, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": {\"checksum\": \"a\"}, \"expected\": {\"checksum\": \"a\"}, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": {\"Host\": \"x\", \"Digest\": \"d\"}, \"expected\": {\"Digest\": \"d\"}, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":33.6,"exit_code":1,"observations":[{"actual":{"content-length":"2"},"check":"fixture 2","expected":{},"passed":false},{"actual":{},"check":"fixture 3","expected":{},"passed":true},{"actual":{"checksum":"a"},"check":"fixture 4","expected":{"checksum":"a"},"passed":true},{"actual":{"Digest":"d","Host":"x"},"check":"fixture 1","expected":{"Digest":"d"},"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": {\"content-length\": \"2\"}, \"expected\": {}, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": {}, \"expected\": {}, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": {\"checksum\": \"a\"}, \"expected\": {\"checksum\": \"a\"}, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": {\"Host\": \"x\", \"Digest\": \"d\"}, \"expected\": {\"Digest\": \"d\"}, \"passed\": false}], \"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."}}