{"abstract":"Identity encoding is implicit unless specifically excluded.","category":"Content negotiation","checks":4,"contract":"Bounded offline decision model: identity encoding is implicit unless specifically excluded. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","evaluation_group":"xh-identity-encoding-is-implicit-unless-specifically-excluded","failed_approach":"The attempted repair uses `qualities.get(\"identity\",1)` and still violates a separate fixture.","family":"xh-identity-encoding-is-implicit-unless-specifically-excluded","id":"FA-6861","implementations":{"attempt":{"sha256":"0374575020aad1dd178e3d70a7084c449f6c03e1218408b1d9de750337955bcf","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(qualities):\n    return qualities.get(\"identity\",1)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve({}), 1)\", \"check('fixture 2', solve({'*': 0}), 0)\", \"check('fixture 3', solve({'identity': 0.2, '*': 0}), 0.2)\", \"check('fixture 4', solve({'gzip': 1}), 1)\"]\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":"01c8f64cc047d7f3bc535163966c616e5bfd71c5bcde08bc4854317f5831b5c9","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(qualities):\n    return qualities.get(\"identity\",0)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve({}), 1)\", \"check('fixture 2', solve({'*': 0}), 0)\", \"check('fixture 3', solve({'identity': 0.2, '*': 0}), 0.2)\", \"check('fixture 4', solve({'gzip': 1}), 1)\"]\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":"8a61336bdc307e030878b47786c923d4178a1b5b6a4d5a5e61af2ebb94be7194","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(qualities):\n    return qualities.get(\"identity\", 0 if qualities.get(\"*\") == 0 else 1)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve({}), 1)\", \"check('fixture 2', solve({'*': 0}), 0)\", \"check('fixture 3', solve({'identity': 0.2, '*': 0}), 0.2)\", \"check('fixture 4', solve({'gzip': 1}), 1)\"]\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-identity-encoding-is-implicit-unless-specifically-excluded","generated_at":"2026-09-29T14:38:05.953266+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic content negotiation model isolates the identity-encoding-is-implicit-unless-specifically-excluded policy at a network component boundary.","repair":"Apply the explicit identity-encoding-is-implicit-unless-specifically-excluded contract, including the tested boundary and negative cases.","root_cause":"The faulty implementation uses `qualities.get(\"identity\",0)` for the identity-encoding-is-implicit-unless-specifically-excluded decision.","sha256":"5427feac1bed0fdbac18e40a1303dd66b4c4949b78cd5e5c0fe202925d05f80e","title":"Identity encoding is implicit unless specifically excluded · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":144.521,"exit_code":1,"observations":[{"actual":1,"check":"fixture 2","expected":0,"passed":false},{"actual":0.2,"check":"fixture 3","expected":0.2,"passed":true},{"actual":1,"check":"fixture 4","expected":1,"passed":true},{"actual":1,"check":"fixture 1","expected":1,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": 1, \"expected\": 0, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": 0.2, \"expected\": 0.2, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": 1, \"expected\": 1, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.988,"exit_code":1,"observations":[{"actual":0,"check":"fixture 2","expected":0,"passed":true},{"actual":0.2,"check":"fixture 3","expected":0.2,"passed":true},{"actual":0,"check":"fixture 4","expected":1,"passed":false},{"actual":0,"check":"fixture 1","expected":1,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 0.2, \"expected\": 0.2, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 0, \"expected\": 1, \"passed\": false}, {\"check\": \"fixture 1\", \"actual\": 0, \"expected\": 1, \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":36.232,"exit_code":0,"observations":[{"actual":0,"check":"fixture 2","expected":0,"passed":true},{"actual":0.2,"check":"fixture 3","expected":0.2,"passed":true},{"actual":1,"check":"fixture 4","expected":1,"passed":true},{"actual":1,"check":"fixture 1","expected":1,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 0.2, \"expected\": 0.2, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": 1, \"expected\": 1, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}