{"abstract":"A continuation response must start at the saved prefix boundary.","category":"HTTP ranges","checks":6,"contract":"Return [append,body] only when returned_start equals saved length; a mismatching start requests restart with empty output.","evaluation_group":"s3-http_ranges-resume-client","failed_approach":"The partial repair uses return [\"append\",body] if returned_start>=saved else [\"restart\",\"\"], which still violates the stated contract.","family":"s3-http_ranges-resume-content-range-start","id":"FA-26746","implementations":{"attempt":{"sha256":"9e5947fd890eec211758b073cd62b8c42d8c49ae1729522b8f5dd35b2a9694e6","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(saved, returned_start, body):\n    return [\"append\",body] if returned_start>=saved else [\"restart\",\"\"]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('resume-content-range-start fixture 0', solve(N,N+1,\"p\"*N), [\"restart\",\"\"])\ncheck('resume-content-range-start fixture 1', solve(N+1,N,\"p\"), [\"restart\",\"\"])\ncheck('resume-content-range-start fixture 2', solve(N,N,\"p\"*N), [\"append\",\"p\"*N])\ncheck('resume-content-range-start fixture 3', solve(0,0,\"\"), [\"append\",\"\"])\ncheck('resume-content-range-start fixture 4', solve(0,N,\"p\"), [\"restart\",\"\"])\ncheck('resume-content-range-start fixture 5', solve(N,0,\"p\"), [\"restart\",\"\"])\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":"a7c4e6bb2e6b40baaa617dc2643a0b2acd811ca479fff9656d42ab01483c4d37","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(saved, returned_start, body):\n    return [\"append\",body]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('resume-content-range-start fixture 0', solve(N,N+1,\"p\"*N), [\"restart\",\"\"])\ncheck('resume-content-range-start fixture 1', solve(N+1,N,\"p\"), [\"restart\",\"\"])\ncheck('resume-content-range-start fixture 2', solve(N,N,\"p\"*N), [\"append\",\"p\"*N])\ncheck('resume-content-range-start fixture 3', solve(0,0,\"\"), [\"append\",\"\"])\ncheck('resume-content-range-start fixture 4', solve(0,N,\"p\"), [\"restart\",\"\"])\ncheck('resume-content-range-start fixture 5', solve(N,0,\"p\"), [\"restart\",\"\"])\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":"253e4743268fcdca37c38accb71ff319325bbff12285ff4e4dbbd03bfb4193fa","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(saved, returned_start, body):\n    return [\"append\",body] if returned_start==saved else [\"restart\",\"\"]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('resume-content-range-start fixture 0', solve(N,N+1,\"p\"*N), [\"restart\",\"\"])\ncheck('resume-content-range-start fixture 1', solve(N+1,N,\"p\"), [\"restart\",\"\"])\ncheck('resume-content-range-start fixture 2', solve(N,N,\"p\"*N), [\"append\",\"p\"*N])\ncheck('resume-content-range-start fixture 3', solve(0,0,\"\"), [\"append\",\"\"])\ncheck('resume-content-range-start fixture 4', solve(0,N,\"p\"), [\"restart\",\"\"])\ncheck('resume-content-range-start fixture 5', solve(N,0,\"p\"), [\"restart\",\"\"])\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-content-range-start","generated_at":"2026-09-29T14:41:18.766152+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 [\"append\",body] if returned_start==saved else [\"restart\",\"\"]","root_cause":"The resume-content-range-start decision uses return [\"append\",body].","sha256":"c0cb08921290f689c9e38c1977889e366baf0362220ca59841e6e8b278af4b25","title":"A continuation response must start at the saved prefix boundary · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":41.484,"exit_code":1,"observations":[{"actual":["append","p"],"check":"resume-content-range-start fixture 0","expected":["restart",""],"passed":false},{"actual":["restart",""],"check":"resume-content-range-start fixture 1","expected":["restart",""],"passed":true},{"actual":["append","p"],"check":"resume-content-range-start fixture 2","expected":["append","p"],"passed":true},{"actual":["append",""],"check":"resume-content-range-start fixture 3","expected":["append",""],"passed":true},{"actual":["append","p"],"check":"resume-content-range-start fixture 4","expected":["restart",""],"passed":false},{"actual":["restart",""],"check":"resume-content-range-start fixture 5","expected":["restart",""],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"resume-content-range-start fixture 0\", \"actual\": [\"append\", \"p\"], \"expected\": [\"restart\", \"\"], \"passed\": false}, {\"check\": \"resume-content-range-start fixture 1\", \"actual\": [\"restart\", \"\"], \"expected\": [\"restart\", \"\"], \"passed\": true}, {\"check\": \"resume-content-range-start fixture 2\", \"actual\": [\"append\", \"p\"], \"expected\": [\"append\", \"p\"], \"passed\": true}, {\"check\": \"resume-content-range-start fixture 3\", \"actual\": [\"append\", \"\"], \"expected\": [\"append\", \"\"], \"passed\": true}, {\"check\": \"resume-content-range-start fixture 4\", \"actual\": [\"append\", \"p\"], \"expected\": [\"restart\", \"\"], \"passed\": false}, {\"check\": \"resume-content-range-start fixture 5\", \"actual\": [\"restart\", \"\"], \"expected\": [\"restart\", \"\"], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.254,"exit_code":1,"observations":[{"actual":["append","p"],"check":"resume-content-range-start fixture 0","expected":["restart",""],"passed":false},{"actual":["append","p"],"check":"resume-content-range-start fixture 1","expected":["restart",""],"passed":false},{"actual":["append","p"],"check":"resume-content-range-start fixture 2","expected":["append","p"],"passed":true},{"actual":["append",""],"check":"resume-content-range-start fixture 3","expected":["append",""],"passed":true},{"actual":["append","p"],"check":"resume-content-range-start fixture 4","expected":["restart",""],"passed":false},{"actual":["append","p"],"check":"resume-content-range-start fixture 5","expected":["restart",""],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"resume-content-range-start fixture 0\", \"actual\": [\"append\", \"p\"], \"expected\": [\"restart\", \"\"], \"passed\": false}, {\"check\": \"resume-content-range-start fixture 1\", \"actual\": [\"append\", \"p\"], \"expected\": [\"restart\", \"\"], \"passed\": false}, {\"check\": \"resume-content-range-start fixture 2\", \"actual\": [\"append\", \"p\"], \"expected\": [\"append\", \"p\"], \"passed\": true}, {\"check\": \"resume-content-range-start fixture 3\", \"actual\": [\"append\", \"\"], \"expected\": [\"append\", \"\"], \"passed\": true}, {\"check\": \"resume-content-range-start fixture 4\", \"actual\": [\"append\", \"p\"], \"expected\": [\"restart\", \"\"], \"passed\": false}, {\"check\": \"resume-content-range-start fixture 5\", \"actual\": [\"append\", \"p\"], \"expected\": [\"restart\", \"\"], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":40.363,"exit_code":0,"observations":[{"actual":["restart",""],"check":"resume-content-range-start fixture 0","expected":["restart",""],"passed":true},{"actual":["restart",""],"check":"resume-content-range-start fixture 1","expected":["restart",""],"passed":true},{"actual":["append","p"],"check":"resume-content-range-start fixture 2","expected":["append","p"],"passed":true},{"actual":["append",""],"check":"resume-content-range-start fixture 3","expected":["append",""],"passed":true},{"actual":["restart",""],"check":"resume-content-range-start fixture 4","expected":["restart",""],"passed":true},{"actual":["restart",""],"check":"resume-content-range-start fixture 5","expected":["restart",""],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"resume-content-range-start fixture 0\", \"actual\": [\"restart\", \"\"], \"expected\": [\"restart\", \"\"], \"passed\": true}, {\"check\": \"resume-content-range-start fixture 1\", \"actual\": [\"restart\", \"\"], \"expected\": [\"restart\", \"\"], \"passed\": true}, {\"check\": \"resume-content-range-start fixture 2\", \"actual\": [\"append\", \"p\"], \"expected\": [\"append\", \"p\"], \"passed\": true}, {\"check\": \"resume-content-range-start fixture 3\", \"actual\": [\"append\", \"\"], \"expected\": [\"append\", \"\"], \"passed\": true}, {\"check\": \"resume-content-range-start fixture 4\", \"actual\": [\"restart\", \"\"], \"expected\": [\"restart\", \"\"], \"passed\": true}, {\"check\": \"resume-content-range-start fixture 5\", \"actual\": [\"restart\", \"\"], \"expected\": [\"restart\", \"\"], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}