{"abstract":"Saved byte positions cannot transfer across content encodings.","category":"HTTP ranges","checks":6,"contract":"Equal representation codings permit concatenation; differing codings return None, including identity versus gzip.","evaluation_group":"s3-http_ranges-resume-client","failed_approach":"The partial repair uses return prefix+body if response_coding==\"identity\" or response_coding==saved_coding else None, which still violates the stated contract.","family":"s3-http_ranges-resume-coding-change-restart","id":"FA-26776","implementations":{"attempt":{"sha256":"71ecd5da14e531f19c8bdea260ebb06e5a700c6c1d0c022f372747d5b416b0f8","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(saved_coding, response_coding, prefix, body):\n    return prefix+body if response_coding==\"identity\" or response_coding==saved_coding else None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('resume-coding-change-restart fixture 0', solve(\"gzip\",\"identity\",\"a\"*N,\"b\"), None)\ncheck('resume-coding-change-restart fixture 1', solve(\"identity\",\"gzip\",\"a\",\"b\"), None)\ncheck('resume-coding-change-restart fixture 2', solve(\"gzip\",\"gzip\",\"a\"*N,\"b\"), \"a\"*N+\"b\")\ncheck('resume-coding-change-restart fixture 3', solve(\"identity\",\"identity\",\"a\",\"b\"), \"ab\")\ncheck('resume-coding-change-restart fixture 4', solve(\"br\",\"gzip\",\"a\",\"b\"), None)\ncheck('resume-coding-change-restart fixture 5', solve(\"br\",\"br\",\"\",\"\"), \"\")\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":"67fa10534b1407e1aa0787fefa701973dd648f1566836b22cb42434738857e71","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(saved_coding, response_coding, prefix, body):\n    return prefix+body\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('resume-coding-change-restart fixture 0', solve(\"gzip\",\"identity\",\"a\"*N,\"b\"), None)\ncheck('resume-coding-change-restart fixture 1', solve(\"identity\",\"gzip\",\"a\",\"b\"), None)\ncheck('resume-coding-change-restart fixture 2', solve(\"gzip\",\"gzip\",\"a\"*N,\"b\"), \"a\"*N+\"b\")\ncheck('resume-coding-change-restart fixture 3', solve(\"identity\",\"identity\",\"a\",\"b\"), \"ab\")\ncheck('resume-coding-change-restart fixture 4', solve(\"br\",\"gzip\",\"a\",\"b\"), None)\ncheck('resume-coding-change-restart fixture 5', solve(\"br\",\"br\",\"\",\"\"), \"\")\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":"fbaae2f4e4c872cdcd0939de620f1b0790c79cded0ec5cea8f23b28056edb000","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(saved_coding, response_coding, prefix, body):\n    return prefix+body if saved_coding==response_coding else None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('resume-coding-change-restart fixture 0', solve(\"gzip\",\"identity\",\"a\"*N,\"b\"), None)\ncheck('resume-coding-change-restart fixture 1', solve(\"identity\",\"gzip\",\"a\",\"b\"), None)\ncheck('resume-coding-change-restart fixture 2', solve(\"gzip\",\"gzip\",\"a\"*N,\"b\"), \"a\"*N+\"b\")\ncheck('resume-coding-change-restart fixture 3', solve(\"identity\",\"identity\",\"a\",\"b\"), \"ab\")\ncheck('resume-coding-change-restart fixture 4', solve(\"br\",\"gzip\",\"a\",\"b\"), None)\ncheck('resume-coding-change-restart fixture 5', solve(\"br\",\"br\",\"\",\"\"), \"\")\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":"Deterministic simplified range service, with stipulated local policies and already parsed trusted inputs; not a complete HTTP implementation. 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":"s3-http_ranges-resume-coding-change-restart","generated_at":"2026-09-29T14:41:18.937306+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Range responses combine representation identity, conditional requests, framing, and partial-object state.","repair":"Apply the bounded decision exactly: return prefix+body if saved_coding==response_coding else None","root_cause":"The resume-coding-change-restart decision uses return prefix+body.","sha256":"d175f3a39f9e1abfe2218bcb8adb111afbb93b8d71ceddd109d38a6d676d077e","title":"Saved byte positions cannot transfer across content encodings · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":40.07,"exit_code":1,"observations":[{"actual":"ab","check":"resume-coding-change-restart fixture 0","expected":null,"passed":false},{"actual":null,"check":"resume-coding-change-restart fixture 1","expected":null,"passed":true},{"actual":"ab","check":"resume-coding-change-restart fixture 2","expected":"ab","passed":true},{"actual":"ab","check":"resume-coding-change-restart fixture 3","expected":"ab","passed":true},{"actual":null,"check":"resume-coding-change-restart fixture 4","expected":null,"passed":true},{"actual":"","check":"resume-coding-change-restart fixture 5","expected":"","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"resume-coding-change-restart fixture 0\", \"actual\": \"ab\", \"expected\": null, \"passed\": false}, {\"check\": \"resume-coding-change-restart fixture 1\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 2\", \"actual\": \"ab\", \"expected\": \"ab\", \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 3\", \"actual\": \"ab\", \"expected\": \"ab\", \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 5\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.091,"exit_code":1,"observations":[{"actual":"ab","check":"resume-coding-change-restart fixture 0","expected":null,"passed":false},{"actual":"ab","check":"resume-coding-change-restart fixture 1","expected":null,"passed":false},{"actual":"ab","check":"resume-coding-change-restart fixture 2","expected":"ab","passed":true},{"actual":"ab","check":"resume-coding-change-restart fixture 3","expected":"ab","passed":true},{"actual":"ab","check":"resume-coding-change-restart fixture 4","expected":null,"passed":false},{"actual":"","check":"resume-coding-change-restart fixture 5","expected":"","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"resume-coding-change-restart fixture 0\", \"actual\": \"ab\", \"expected\": null, \"passed\": false}, {\"check\": \"resume-coding-change-restart fixture 1\", \"actual\": \"ab\", \"expected\": null, \"passed\": false}, {\"check\": \"resume-coding-change-restart fixture 2\", \"actual\": \"ab\", \"expected\": \"ab\", \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 3\", \"actual\": \"ab\", \"expected\": \"ab\", \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 4\", \"actual\": \"ab\", \"expected\": null, \"passed\": false}, {\"check\": \"resume-coding-change-restart fixture 5\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":38.612,"exit_code":0,"observations":[{"actual":null,"check":"resume-coding-change-restart fixture 0","expected":null,"passed":true},{"actual":null,"check":"resume-coding-change-restart fixture 1","expected":null,"passed":true},{"actual":"ab","check":"resume-coding-change-restart fixture 2","expected":"ab","passed":true},{"actual":"ab","check":"resume-coding-change-restart fixture 3","expected":"ab","passed":true},{"actual":null,"check":"resume-coding-change-restart fixture 4","expected":null,"passed":true},{"actual":"","check":"resume-coding-change-restart fixture 5","expected":"","passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"resume-coding-change-restart fixture 0\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 1\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 2\", \"actual\": \"ab\", \"expected\": \"ab\", \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 3\", \"actual\": \"ab\", \"expected\": \"ab\", \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"resume-coding-change-restart fixture 5\", \"actual\": \"\", \"expected\": \"\", \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}