{"abstract":"Empty accept encoding requires identity.","category":"Content negotiation","checks":4,"contract":"Bounded offline decision model: empty accept encoding requires identity. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","contract_signature":"present, encodings","evaluation_group":"xh-empty-accept-encoding-requires-identity","failed_approach":"The attempted repair uses `['identity'] if not encodings else encodings` and still violates a separate fixture.","family":"xh-empty-accept-encoding-requires-identity","id":"FA-6866","implementations":{"attempt":{"sha256":"0839bbc9e61d8a77c0b8e436480709e28e1fa5b80594b3b16e8b10f7c6c72054","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(present, encodings):\n    return ['identity'] if not encodings else encodings\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(True, []), ['identity'])\", \"check('fixture 2', solve(False, []), [])\", \"check('fixture 3', solve(True, ['gzip']), ['gzip'])\", \"check('fixture 4', solve(False, ['br']), ['br'])\"]\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":"c256310e598274894a251a0f26e9b52fd9488f85c354930831ea1e85cb3e4980","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(present, encodings):\n    return encodings\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(True, []), ['identity'])\", \"check('fixture 2', solve(False, []), [])\", \"check('fixture 3', solve(True, ['gzip']), ['gzip'])\", \"check('fixture 4', solve(False, ['br']), ['br'])\"]\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-empty-accept-encoding-requires-identity","generated_at":"2026-09-29T14:38:05.968736+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic content negotiation model isolates the empty-accept-encoding-requires-identity policy at a network component boundary.","root_cause":"The faulty implementation uses `encodings` for the empty-accept-encoding-requires-identity decision.","sha256":"b82bc0a5ea2f908a1b4e7b8bbebd46d5a59db893910a8db862d9745530917819","title":"Empty accept encoding requires identity · 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":134.61,"exit_code":1,"observations":[{"actual":["identity"],"check":"fixture 2","expected":[],"passed":false},{"actual":["gzip"],"check":"fixture 3","expected":["gzip"],"passed":true},{"actual":["br"],"check":"fixture 4","expected":["br"],"passed":true},{"actual":["identity"],"check":"fixture 1","expected":["identity"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": [\"identity\"], \"expected\": [], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [\"gzip\"], \"expected\": [\"gzip\"], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [\"br\"], \"expected\": [\"br\"], \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": [\"identity\"], \"expected\": [\"identity\"], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":44.827,"exit_code":1,"observations":[{"actual":[],"check":"fixture 2","expected":[],"passed":true},{"actual":["gzip"],"check":"fixture 3","expected":["gzip"],"passed":true},{"actual":["br"],"check":"fixture 4","expected":["br"],"passed":true},{"actual":[],"check":"fixture 1","expected":["identity"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": [\"gzip\"], \"expected\": [\"gzip\"], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [\"br\"], \"expected\": [\"br\"], \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": [], \"expected\": [\"identity\"], \"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."}}