{
  "observation": "Long-context chat traffic is dominated by large prefills, so TTFT under the stepped SLO is the binding constraint. A launch-safe baseline should spread compute across all 4 GPUs while limiting concurrent long-prefill contention.",
  "diagnosis": "The FLASHINFER attempt failed at startup, but the safer FLASH_ATTN family launched successfully. A conservative seq cap plus a moderate batched-token cap is a better baseline for diagnosing whether the SLO itself is too aggressive under this trace.",
  "config_patch": {
    "env_patch": {
      "VLLM_ATTENTION_BACKEND": "FLASH_ATTN"
    },
    "flag_patch": {
      "tensor-parallel-size": 4,
      "max-num-seqs": 16,
      "max-num-batched-tokens": 24576,
      "gpu-memory-utilization": 0.94,
      "block-size": 32
    }
  },
  "expected_effects": [
    "Stable 4-GPU launch without FLASHINFER warmup failure",
    "Lower head-of-line blocking than larger sequence caps",
    "More interpretable lower-bound throughput/SLO measurement"
  ],
  "why_not_previous_failures": "This proposal keeps the launch-safe FLASH_ATTN backend and the conservative batching limits that already avoided the earlier FLASHINFER startup failure."
}