{"abstract":"A read policy distinguishes safety from idempotency.","category":"HTTP semantics","checks":4,"contract":"A read policy distinguishes safety from idempotency: return the result specified by the explicit input/output boundary fixtures.","contract_signature":"method","evaluation_group":"xh-safe-methods","failed_approach":"The attempted repair uses `method in ('GET', 'HEAD')` and still violates a separate fixture.","family":"xh-safe-methods","id":"FA-6596","implementations":{"attempt":{"sha256":"f600524f54ee0cfc248e6792854ab06ccf4b504afddc8362d8f8ca6bba998956","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(method):\n    return method in ('GET', 'HEAD')\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve('DELETE'), False)\", \"check('fixture 2', solve('OPTIONS'), True)\", \"check('fixture 3', solve('GET'), True)\", \"check('fixture 4', solve('PATCH'), 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":"c706f990383b135fafd5f664d48d951f7a34b1d3ff61931a141aeb779a48d9c9","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(method):\n    return method != 'POST'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve('DELETE'), False)\", \"check('fixture 2', solve('OPTIONS'), True)\", \"check('fixture 3', solve('GET'), True)\", \"check('fixture 4', solve('PATCH'), 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-safe-methods","generated_at":"2026-09-29T14:38:03.612984+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic http semantics model isolates the safe-methods policy at a network component boundary.","root_cause":"The faulty implementation uses `method != 'POST'` for the safe-methods decision.","sha256":"c5cf69975f2a650db116786fdb45e26fde5f37bb2dd1d51825264778dd820f50","title":"A read policy distinguishes safety from idempotency · 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":37.399,"exit_code":1,"observations":[{"actual":false,"check":"fixture 2","expected":true,"passed":false},{"actual":true,"check":"fixture 3","expected":true,"passed":true},{"actual":false,"check":"fixture 4","expected":false,"passed":true},{"actual":false,"check":"fixture 1","expected":false,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": false, \"expected\": true, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"fixture 1\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":37.154,"exit_code":1,"observations":[{"actual":true,"check":"fixture 2","expected":true,"passed":true},{"actual":true,"check":"fixture 3","expected":true,"passed":true},{"actual":true,"check":"fixture 4","expected":false,"passed":false},{"actual":true,"check":"fixture 1","expected":false,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"fixture 1\", \"actual\": true, \"expected\": false, \"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."}}