{"abstract":"Multipart boundary detection retains an incomplete delimiter suffix across reads.","category":"HTTP ranges","checks":6,"contract":"Return [complete-prefix,remainder] split at first complete marker in tail+chunk; if absent preserve the entire data as remainder for this bounded buffering model.","contract_signature":"tail, chunk, marker","evaluation_group":"s3-http_ranges-multipart-client","failed_approach":"The partial repair uses s=tail+chunk\np=s.find(marker)\nreturn [s[:p],s[p+len(marker):]] if p>=0 else [s,\"\"], which still violates the stated contract.","family":"s3-http_ranges-multipart-client-delimiter-split","id":"FA-26791","implementations":{"attempt":{"sha256":"c2ee401f4213745f709deba793438c72dba71d6cfcd1943d1ac0cefcf50a62ed","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(tail, chunk, marker):\n    s=tail+chunk\n    p=s.find(marker)\n    return [s[:p],s[p+len(marker):]] if p>=0 else [s,\"\"]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('multipart-client-delimiter-split fixture 0', solve(\"a\"*N+\"--\",\"bX\",\"--b\"), [\"a\"*N,\"X\"])\ncheck('multipart-client-delimiter-split fixture 1', solve(\"a\",\"b\",\"--b\"), [\"\",\"ab\"])\ncheck('multipart-client-delimiter-split fixture 2', solve(\"\",\"abc--bZ\",\"--b\"), [\"abc\",\"Z\"])\ncheck('multipart-client-delimiter-split fixture 3', solve(\"\",\"\",\"--b\"), [\"\",\"\"])\ncheck('multipart-client-delimiter-split fixture 4', solve(\"--b\",\"X\",\"--b\"), [\"\",\"X\"])\ncheck('multipart-client-delimiter-split fixture 5', solve(\"x\",\"--b--b\",\"--b\"), [\"x\",\"--b\"])\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":"3c9a9ae611088fa54c2b55a01a5baec3d4fab365e811333338a7eaa5e135a15e","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(tail, chunk, marker):\n    p=chunk.find(marker)\n    return [chunk[:p],chunk[p+len(marker):]] if p>=0 else [\"\",chunk]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('multipart-client-delimiter-split fixture 0', solve(\"a\"*N+\"--\",\"bX\",\"--b\"), [\"a\"*N,\"X\"])\ncheck('multipart-client-delimiter-split fixture 1', solve(\"a\",\"b\",\"--b\"), [\"\",\"ab\"])\ncheck('multipart-client-delimiter-split fixture 2', solve(\"\",\"abc--bZ\",\"--b\"), [\"abc\",\"Z\"])\ncheck('multipart-client-delimiter-split fixture 3', solve(\"\",\"\",\"--b\"), [\"\",\"\"])\ncheck('multipart-client-delimiter-split fixture 4', solve(\"--b\",\"X\",\"--b\"), [\"\",\"X\"])\ncheck('multipart-client-delimiter-split fixture 5', solve(\"x\",\"--b--b\",\"--b\"), [\"x\",\"--b\"])\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-multipart-client-delimiter-split","generated_at":"2026-09-29T14:41:19.180360+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.","root_cause":"The multipart-client-delimiter-split decision uses p=chunk.find(marker)\nreturn [chunk[:p],chunk[p+len(marker):]] if p>=0 else [\"\",chunk].","sha256":"b09dc65195aef544477452798c9aeb24469f9a0d81084333fa265af91e0d9471","title":"Multipart boundary detection retains an incomplete delimiter suffix across reads · 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":38.953,"exit_code":1,"observations":[{"actual":["a","X"],"check":"multipart-client-delimiter-split fixture 0","expected":["a","X"],"passed":true},{"actual":["ab",""],"check":"multipart-client-delimiter-split fixture 1","expected":["","ab"],"passed":false},{"actual":["abc","Z"],"check":"multipart-client-delimiter-split fixture 2","expected":["abc","Z"],"passed":true},{"actual":["",""],"check":"multipart-client-delimiter-split fixture 3","expected":["",""],"passed":true},{"actual":["","X"],"check":"multipart-client-delimiter-split fixture 4","expected":["","X"],"passed":true},{"actual":["x","--b"],"check":"multipart-client-delimiter-split fixture 5","expected":["x","--b"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"multipart-client-delimiter-split fixture 0\", \"actual\": [\"a\", \"X\"], \"expected\": [\"a\", \"X\"], \"passed\": true}, {\"check\": \"multipart-client-delimiter-split fixture 1\", \"actual\": [\"ab\", \"\"], \"expected\": [\"\", \"ab\"], \"passed\": false}, {\"check\": \"multipart-client-delimiter-split fixture 2\", \"actual\": [\"abc\", \"Z\"], \"expected\": [\"abc\", \"Z\"], \"passed\": true}, {\"check\": \"multipart-client-delimiter-split fixture 3\", \"actual\": [\"\", \"\"], \"expected\": [\"\", \"\"], \"passed\": true}, {\"check\": \"multipart-client-delimiter-split fixture 4\", \"actual\": [\"\", \"X\"], \"expected\": [\"\", \"X\"], \"passed\": true}, {\"check\": \"multipart-client-delimiter-split fixture 5\", \"actual\": [\"x\", \"--b\"], \"expected\": [\"x\", \"--b\"], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":38.028,"exit_code":1,"observations":[{"actual":["","bX"],"check":"multipart-client-delimiter-split fixture 0","expected":["a","X"],"passed":false},{"actual":["","b"],"check":"multipart-client-delimiter-split fixture 1","expected":["","ab"],"passed":false},{"actual":["abc","Z"],"check":"multipart-client-delimiter-split fixture 2","expected":["abc","Z"],"passed":true},{"actual":["",""],"check":"multipart-client-delimiter-split fixture 3","expected":["",""],"passed":true},{"actual":["","X"],"check":"multipart-client-delimiter-split fixture 4","expected":["","X"],"passed":true},{"actual":["","--b"],"check":"multipart-client-delimiter-split fixture 5","expected":["x","--b"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"multipart-client-delimiter-split fixture 0\", \"actual\": [\"\", \"bX\"], \"expected\": [\"a\", \"X\"], \"passed\": false}, {\"check\": \"multipart-client-delimiter-split fixture 1\", \"actual\": [\"\", \"b\"], \"expected\": [\"\", \"ab\"], \"passed\": false}, {\"check\": \"multipart-client-delimiter-split fixture 2\", \"actual\": [\"abc\", \"Z\"], \"expected\": [\"abc\", \"Z\"], \"passed\": true}, {\"check\": \"multipart-client-delimiter-split fixture 3\", \"actual\": [\"\", \"\"], \"expected\": [\"\", \"\"], \"passed\": true}, {\"check\": \"multipart-client-delimiter-split fixture 4\", \"actual\": [\"\", \"X\"], \"expected\": [\"\", \"X\"], \"passed\": true}, {\"check\": \"multipart-client-delimiter-split fixture 5\", \"actual\": [\"\", \"--b\"], \"expected\": [\"x\", \"--b\"], \"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."}}