diff --git a/README.md b/README.md
index 2ce958d..b135e7a 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,7 @@
 | DSV4 H200 SGLang baseline | `experiments/dsv4_h200_sglang/run_bench.sh` | NVIDIA H200 + native SGLang + DeepSeek-V4-Flash |
 | DSV4 H200 SGLang vs vLLM | `experiments/dsv4_h200_sglang_vs_vllm/run_bench.sh` | NVIDIA H200 上 SGLang 与 vLLM 控制变量对比（TP=8，最长 200k 上下文） |
 | DSV4 H200 vLLM DSpark vs default | `experiments/dsv4_h200_vllm_dspark_vs_default/run_bench.sh` | vLLM 开启 DSpark 投机解码 vs 默认配置，验证 TTFT 差异 |
+| DSV4 H200 max context length | `experiments/dsv4_h200_max_context_length/run_bench.sh` | 探索 SGLang / vLLM 在 H200 上能支持的最大输入长度 |
 
 ### 旧结构（scripts/ + bench_results/）
 
@@ -76,6 +77,12 @@ bash experiments/dsv4_h200_sglang_vs_vllm/run_bench.sh
 bash experiments/dsv4_h200_vllm_dspark_vs_default/run_bench.sh
 ```
 
+### H200 max context length
+
+```bash
+bash experiments/dsv4_h200_max_context_length/run_bench.sh
+```
+
 ### DSpark grid（旧结构）
 
 ```bash
diff --git a/experiments/dsv4_h200_max_context_length/README.md b/experiments/dsv4_h200_max_context_length/README.md
new file mode 100644
index 0000000..583d098
--- /dev/null
+++ b/experiments/dsv4_h200_max_context_length/README.md
@@ -0,0 +1,59 @@
+# DSV4 H200 最大上下文长度探索实验
+
+在 8x NVIDIA H200 上，逐步增大输入长度，测试 **SGLang** 与 **vLLM** serving DeepSeek-V4-Flash 时各自能稳定处理的最长上下文。
+
+## 目的
+
+- 找到 SGLang / vLLM 在 H200 TP=8 配置下，单请求最多能支持多长的输入 token。
+- 每个长度只跑 1 个请求、输出 1 个 token，尽量减少 decode 阶段显存干扰。
+- 每次测试单独启动 server，并把 `max-model-len` / `context-length` 刚好设为 `target_len + 1024`，避免预分配过大。
+
+## 默认候选长度
+
+```text
+65536, 131072, 262144, 393216, 524288, 655360, 786432, 917504, 1048576
+```
+
+可以通过环境变量覆盖：
+
+```bash
+CANDIDATE_LENS=(65536 131072 262144 524288) bash run_bench.sh
+```
+
+## 控制变量
+
+| 维度 | SGLang | vLLM |
+|---|---|---|
+| 硬件 | 8x H200，TP=8 | 同上 |
+| 输入长度 | `--random-input-len $target_len --random-range-ratio 1.0` | 同上 |
+| 输出长度 | 1 | 1 |
+| 并发 / 请求数 | 1 / 1 | 1 / 1 |
+| 压测客户端 | `sglang.bench_serving --backend vllm` | 同上 |
+
+> `--random-range-ratio 1.0` 确保输入长度固定为 `target_len`，而不是默认的 `[1, target_len]` 均匀分布。
+
+## 快速运行
+
+```bash
+bash experiments/dsv4_h200_max_context_length/run_bench.sh
+```
+
+结果保存在 `experiments/dsv4_h200_max_context_length/results/<RUN_ID>/`：
+
+```
+results/<RUN_ID>/
+├── results.json
+├── report.md
+└── raw_outputs/      # gitignored
+```
+
+## 产物说明
+
+- `results.json`：每个候选长度的尝试记录，包括 `success`、TTFT/TPOT/E2E 指标、`server_args`。
+- `report.md`：汇总表格，以及每个 backend 最终支持的最大输入长度。
+
+## 环境
+
+- SGLM server: `/data/user1/yy/envs/sglang`
+- vLLM server: `/data/user1/yy/envs/vllm`
+- Benchmark client: `/data/user1/yy/envs/sglang`
diff --git a/experiments/dsv4_h200_max_context_length/config.env b/experiments/dsv4_h200_max_context_length/config.env
new file mode 100644
index 0000000..180129d
--- /dev/null
+++ b/experiments/dsv4_h200_max_context_length/config.env
@@ -0,0 +1,48 @@
+# Common configuration for the max context length exploration on H200.
+# All values can be overridden via environment variables.
+
+EXPERIMENT="dsv4_h200_max_context_length"
+MODEL_NAME="DeepSeek-V4-Flash"
+MODEL_PATH="/data/models/DeepSeek-V4-Flash"
+SERVED_MODEL_NAME="deepseek-v4-flash"
+
+# Ports must differ from other running experiments.
+SGLANG_PORT="${SGLANG_PORT:-30011}"
+VLLM_PORT="${VLLM_PORT:-30012}"
+
+# Virtual environments.
+VENV_SGLANG="${VENV_SGLANG:-/data/user1/yy/envs/sglang}"
+VENV_VLLM="${VENV_VLLM:-/data/user1/yy/envs/vllm}"
+VENV_CLIENT="${VENV_CLIENT:-$VENV_SGLANG}"
+
+# Hardware: use all 8 H200 cards for both backends.
+export CUDA_VISIBLE_DEVICES="0,1,2,3,4,5,6,7"
+TP=8
+
+# We want exact input lengths, so fix the random range ratio to 1.0.
+OUTPUT_LEN="${OUTPUT_LEN:-1}"
+NUM_PROMPTS="${NUM_PROMPTS:-1}"
+MAX_CONCURRENCY="${MAX_CONCURRENCY:-1}"
+REQUEST_RATE="${REQUEST_RATE:-10000}"
+
+# Padding added to target length when setting server max context/model length.
+CONTEXT_PAD="${CONTEXT_PAD:-1024}"
+
+# Candidate input lengths (tokens). Override via CANDIDATE_LENS env var.
+if [[ -z "${CANDIDATE_LENS:-}" ]]; then
+  declare -a CANDIDATE_LENS=(
+    65536
+    131072
+    262144
+    393216
+    524288
+    655360
+    786432
+    917504
+    1048576
+  )
+fi
+
+# Server start scripts bundled with this experiment.
+SGLANG_START_SCRIPT="${SCRIPT_DIR:-.}/start_sglang.sh"
+VLLM_START_SCRIPT="${SCRIPT_DIR:-.}/start_vllm.sh"
diff --git a/experiments/dsv4_h200_max_context_length/extract_metrics.py b/experiments/dsv4_h200_max_context_length/extract_metrics.py
new file mode 100755
index 0000000..c2579ce
--- /dev/null
+++ b/experiments/dsv4_h200_max_context_length/extract_metrics.py
@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+"""Extract a compact metrics dict from a sglang.bench_serving JSONL output.
+
+Usage:
+    python3 extract_metrics.py <raw_jsonl_path>
+"""
+import json
+import sys
+from pathlib import Path
+
+
+def parse_jsonl(path: Path) -> dict | None:
+    with open(path, "r", encoding="utf-8") as f:
+        for line in f:
+            line = line.strip()
+            if not line:
+                continue
+            try:
+                return json.loads(line)
+            except json.JSONDecodeError:
+                continue
+    return None
+
+
+def compute(data: dict) -> dict:
+    return {
+        "success_count": data.get("completed", 0),
+        "total_count": len(data.get("input_lens", [])),
+        "duration_s": data.get("duration", 0.0),
+        "request_throughput": data.get("request_throughput", 0.0),
+        "input_token_throughput": data.get("input_throughput", 0.0),
+        "output_token_throughput": data.get("output_throughput", 0.0),
+        "total_input_tokens": data.get("total_input_tokens", 0),
+        "total_output_tokens": data.get("total_output_tokens", 0),
+        "e2e_ms": {
+            "mean": data.get("mean_e2e_latency_ms", 0.0),
+            "p50": data.get("median_e2e_latency_ms", 0.0),
+            "p90": data.get("p90_e2e_latency_ms", 0.0),
+            "p95": data.get("p95_e2e_latency_ms", 0.0),
+            "p99": data.get("p99_e2e_latency_ms", 0.0),
+        },
+        "ttft_ms": {
+            "mean": data.get("mean_ttft_ms", 0.0),
+            "p50": data.get("median_ttft_ms", 0.0),
+            "p90": data.get("p90_ttft_ms", 0.0),
+            "p95": data.get("p95_ttft_ms", 0.0),
+            "p99": data.get("p99_ttft_ms", 0.0),
+        },
+        "tpot_ms": {
+            "mean": data.get("mean_tpot_ms", 0.0),
+            "p50": data.get("median_tpot_ms", 0.0),
+            "p90": data.get("p90_tpot_ms", 0.0),
+            "p95": data.get("p95_tpot_ms", 0.0),
+            "p99": data.get("p99_tpot_ms", 0.0),
+        },
+        "itl_ms": {
+            "mean": data.get("mean_itl_ms", 0.0),
+            "p50": data.get("median_itl_ms", 0.0),
+            "p90": data.get("p90_itl_ms", 0.0),
+            "p95": data.get("p95_itl_ms", 0.0),
+            "p99": data.get("p99_itl_ms", 0.0),
+        },
+    }
+
+
+def main():
+    path = Path(sys.argv[1])
+    data = parse_jsonl(path)
+    if data is None:
+        raise SystemExit("No valid JSON found")
+    print(json.dumps(compute(data), indent=2, ensure_ascii=False))
+
+
+if __name__ == "__main__":
+    main()
diff --git a/experiments/dsv4_h200_max_context_length/parse_results.py b/experiments/dsv4_h200_max_context_length/parse_results.py
new file mode 100755
index 0000000..0c497d3
--- /dev/null
+++ b/experiments/dsv4_h200_max_context_length/parse_results.py
@@ -0,0 +1,62 @@
+#!/usr/bin/env python3
+"""Generate report.md from results.json for the max context length experiment.
+
+Usage:
+    python3 parse_results.py <result_root>
+"""
+import json
+import sys
+from pathlib import Path
+
+
+def main():
+    result_root = Path(sys.argv[1]) if len(sys.argv) > 1 else Path("results")
+    results_json = result_root / "results.json"
+    report_path = result_root / "report.md"
+
+    with open(results_json, "r", encoding="utf-8") as f:
+        data = json.load(f)
+
+    meta = data["metadata"]
+    cfg = data["config"]
+
+    with open(report_path, "w", encoding="utf-8") as f:
+        f.write("# H200 Max Context Length Exploration Report\n\n")
+        f.write(f"- Result root: `{result_root}`\n")
+        f.write(f"- Model: `{meta['model']}`\n")
+        f.write(f"- Hardware: {meta['hardware']}\n")
+        f.write(f"- TP: {cfg['tp']}\n")
+        f.write(f"- Output len: {cfg['output_len']}, num prompts: {cfg['num_prompts']}, concurrency: {cfg['max_concurrency']}\n\n")
+
+        f.write("## Per-attempt results\n\n")
+        f.write("| Backend | Target len | Max model/context len | Status | TTFT mean(ms) | TTFT P95(ms) | E2E mean(ms) | E2E P99(ms) | Error |\n")
+        f.write("|---|---:|---:|---:|---:|---:|---:|---:|---:|\n")
+
+        max_by_backend = {}
+        for s in data.get("scenarios", []):
+            backend = s["backend"]
+            target = s["target_len"]
+            status = "✅ pass" if s["success"] else "❌ fail"
+            metrics = s.get("metrics") or {}
+            ttft = metrics.get("ttft_ms", {})
+            e2e = metrics.get("e2e_ms", {})
+            f.write(
+                f"| {backend} | {target} | {s['max_model_len']} | {status} | "
+                f"{ttft.get('mean', 0):.2f} | {ttft.get('p95', 0):.2f} | "
+                f"{e2e.get('mean', 0):.2f} | {e2e.get('p99', 0):.2f} | "
+                f"{s.get('error', '') or ''} |\n"
+            )
+            if s["success"] and (backend not in max_by_backend or target > max_by_backend[backend]):
+                max_by_backend[backend] = target
+
+        f.write("\n## Maximum supported input length\n\n")
+        for backend in ("sglang", "vllm"):
+            max_len = max_by_backend.get(backend, 0)
+            f.write(f"- **{backend}**: {max_len} tokens\n")
+        f.write("\n")
+
+    print(f"Wrote report to {report_path}")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/experiments/dsv4_h200_max_context_length/run_bench.sh b/experiments/dsv4_h200_max_context_length/run_bench.sh
new file mode 100755
index 0000000..bc1515d
--- /dev/null
+++ b/experiments/dsv4_h200_max_context_length/run_bench.sh
@@ -0,0 +1,269 @@
+#!/usr/bin/env bash
+# Max context length exploration for SGLang and vLLM on H200.
+set -Eeuo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+EXPERIMENT_NAME="$(basename "$SCRIPT_DIR")"
+
+# shellcheck source=/dev/null
+source "${SCRIPT_DIR}/../../scripts/common/lib.sh"
+# shellcheck source=/dev/null
+source "${SCRIPT_DIR}/../../scripts/common/platform.sh"
+# shellcheck source=/dev/null
+source "${SCRIPT_DIR}/config.env"
+
+RUN_ID="${RUN_ID:-$(date '+%Y%m%d-%H%M%S')}"
+RESULT_ROOT="${RESULT_ROOT:-${SCRIPT_DIR}/results/${RUN_ID}}"
+LOG_DIR="${RESULT_ROOT}/logs"
+RAW_DIR="${RESULT_ROOT}/raw_outputs"
+
+ensure_result_root "$RESULT_ROOT"
+log_init "${LOG_DIR}/orchestrator.log"
+
+log "experiment=${EXPERIMENT_NAME}"
+log "run_id=${RUN_ID}"
+log "platform=${PLATFORM}"
+log "hardware=${HARDWARE}"
+log "model=${MODEL_PATH}"
+log "candidate_lengths=${CANDIDATE_LENS[*]}"
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+is_server_healthy() {
+  local port="$1"
+  curl --fail --silent --show-error --max-time 5 "http://127.0.0.1:${port}/health" >/dev/null 2>&1
+}
+
+stop_server() {
+  local backend="$1"
+  local pid_file="/data/user1/yy/${EXPERIMENT_NAME}_${backend}.pid"
+  if [[ -f "$pid_file" ]]; then
+    local pid
+    pid="$(cat "$pid_file")"
+    if kill -0 "$pid" 2>/dev/null; then
+      log "stopping ${backend} server pid=${pid}"
+      kill "$pid" 2>/dev/null || true
+      sleep 5
+      kill -9 "$pid" 2>/dev/null || true
+    fi
+    rm -f "$pid_file"
+  fi
+  sleep 2
+}
+
+start_server() {
+  local backend="$1"
+  local target_len="$2"
+  local start_script port
+  if [[ "$backend" == "sglang" ]]; then
+    start_script="${SGLANG_START_SCRIPT}"
+    port="$SGLANG_PORT"
+  else
+    start_script="${VLLM_START_SCRIPT}"
+    port="$VLLM_PORT"
+  fi
+
+  log "starting ${backend} server (target_len=${target_len}) with ${start_script}"
+  bash "${start_script}" "$target_len" >> "${LOG_DIR}/${backend}_${target_len}.server.outer.log" 2>&1
+
+  if ! is_server_healthy "$port"; then
+    log "error: ${backend} server (target_len=${target_len}) failed to become healthy"
+    return 1
+  fi
+  log "${backend} server is healthy on port ${port}"
+}
+
+build_server_args() {
+  local backend="$1"
+  local target_len="$2"
+  local max_len=$(( target_len + CONTEXT_PAD ))
+  if [[ "$backend" == "sglang" ]]; then
+    echo "sglang serve --trust-remote-code --model-path $MODEL_PATH --tp $TP --moe-runner-backend marlin --context-length $max_len --max-running-requests 1 --mem-fraction-static 0.88 --host 0.0.0.0 --port $SGLANG_PORT"
+  else
+    echo "vllm serve $MODEL_PATH --trust-remote-code --tensor-parallel-size $TP --kv-cache-dtype fp8 --max-model-len $max_len --max-num-seqs 1 --block-size 256 --gpu-memory-utilization 0.90 --tokenizer-mode deepseek_v4 --reasoning-parser deepseek_v4 --no-disable-hybrid-kv-cache-manager --disable-uvicorn-access-log --port $VLLM_PORT"
+  fi
+}
+
+append_scenario() {
+  local scenario_json="$1"
+  "${VENV_CLIENT}/bin/python" - "$RESULT_JSON" "$scenario_json" <<'PY'
+import json
+import sys
+
+results_path, scenario_json = sys.argv[1], sys.argv[2]
+with open(results_path, "r", encoding="utf-8") as f:
+    data = json.load(f)
+
+data["scenarios"].append(json.loads(scenario_json))
+with open(results_path, "w", encoding="utf-8") as f:
+    json.dump(data, f, indent=2, ensure_ascii=False)
+PY
+}
+
+run_backend() {
+  local backend="$1"
+  local port
+  if [[ "$backend" == "sglang" ]]; then
+    port="$SGLANG_PORT"
+  else
+    port="$VLLM_PORT"
+  fi
+
+  log "===== ${backend} max context exploration START ====="
+
+  for target_len in "${CANDIDATE_LENS[@]}"; do
+    local max_len=$(( target_len + CONTEXT_PAD ))
+    local output_file="${RAW_DIR}/${backend}_ctx_${target_len}.jsonl"
+    local detail_log="${LOG_DIR}/${backend}_ctx_${target_len}.log"
+
+    log "trying ${backend} target_len=${target_len} (max_model/context_len=${max_len})"
+
+    stop_server "$backend"
+    if ! start_server "$backend" "$target_len"; then
+      local err="server failed to start"
+      log "ERROR: ${err}"
+      append_scenario "$(jq -n \
+        --arg backend "$backend" \
+        --argjson target_len "$target_len" \
+        --argjson max_model_len "$max_len" \
+        --arg server_args "$(build_server_args "$backend" "$target_len")" \
+        --arg error "$err" \
+        '{backend:$backend, target_len:$target_len, max_model_len:$max_model_len, success:false, server_args:$server_args, metrics:null, error:$error}')"
+      break
+    fi
+
+    local bench_rc=0
+    "${VENV_CLIENT}/bin/python" -m sglang.bench_serving \
+      --backend vllm \
+      --host 127.0.0.1 \
+      --port "$port" \
+      --dataset-name random \
+      --random-input-len "$target_len" \
+      --random-output-len "$OUTPUT_LEN" \
+      --random-range-ratio 1.0 \
+      --num-prompts "$NUM_PROMPTS" \
+      --max-concurrency "$MAX_CONCURRENCY" \
+      --request-rate "$REQUEST_RATE" \
+      --output-file "$output_file" \
+      --output-details \
+      > "$detail_log" 2>&1 || bench_rc=$?
+
+    if [[ "$bench_rc" -ne 0 ]]; then
+      local err="bench_serving exited with code ${bench_rc}; see ${detail_log}"
+      log "ERROR: ${backend} target_len=${target_len} failed; ${err}"
+      append_scenario "$(jq -n \
+        --arg backend "$backend" \
+        --argjson target_len "$target_len" \
+        --argjson max_model_len "$max_len" \
+        --arg server_args "$(build_server_args "$backend" "$target_len")" \
+        --arg error "$err" \
+        '{backend:$backend, target_len:$target_len, max_model_len:$max_model_len, success:false, server_args:$server_args, metrics:null, error:$error}')"
+      stop_server "$backend"
+      break
+    fi
+
+    # Verify the request actually completed.
+    local completed
+    completed="$(${VENV_CLIENT}/bin/python -c "
+import json
+with open('${output_file}') as f:
+    for line in f:
+        data = json.loads(line)
+        print(data.get('completed', 0))
+        break
+")"
+    if [[ "${completed:-0}" -lt "$NUM_PROMPTS" ]]; then
+      local err="only ${completed}/${NUM_PROMPTS} requests completed"
+      log "ERROR: ${backend} target_len=${target_len} ${err}"
+      append_scenario "$(jq -n \
+        --arg backend "$backend" \
+        --argjson target_len "$target_len" \
+        --argjson max_model_len "$max_len" \
+        --arg server_args "$(build_server_args "$backend" "$target_len")" \
+        --arg error "$err" \
+        '{backend:$backend, target_len:$target_len, max_model_len:$max_model_len, success:false, server_args:$server_args, metrics:null, error:$error}')"
+      stop_server "$backend"
+      break
+    fi
+
+    local metrics_json
+    metrics_json="$(${VENV_CLIENT}/bin/python "${SCRIPT_DIR}/extract_metrics.py" "$output_file")"
+
+    append_scenario "$(jq -n \
+      --arg backend "$backend" \
+      --argjson target_len "$target_len" \
+      --argjson max_model_len "$max_len" \
+      --arg server_args "$(build_server_args "$backend" "$target_len")" \
+      --argjson metrics "$metrics_json" \
+      '{backend:$backend, target_len:$target_len, max_model_len:$max_model_len, success:true, server_args:$server_args, metrics:$metrics, error:null}')"
+
+    log "${backend} target_len=${target_len} succeeded"
+    stop_server "$backend"
+  done
+
+  log "===== ${backend} max context exploration DONE ====="
+}
+
+# ---------------------------------------------------------------------------
+# Main
+# ---------------------------------------------------------------------------
+
+mkdir -p "$RAW_DIR" "$LOG_DIR"
+
+RESULT_JSON="${RESULT_ROOT}/results.json"
+write_metadata_json \
+  "$RESULT_JSON" \
+  "$EXPERIMENT_NAME" \
+  "$RUN_ID" \
+  "$MODEL_PATH" \
+  "sglang+vllm" \
+  "sglang+vllm" \
+  "$HARDWARE" \
+  "$ACCELERATOR" \
+  "$CHIP" \
+  "experiments/${EXPERIMENT_NAME}/run_bench.sh" \
+  "$VENV_CLIENT" \
+  "H200 max context length exploration for DeepSeek-V4-Flash"
+
+# Embed config.
+"${VENV_CLIENT}/bin/python" - "$RESULT_JSON" <<'PY'
+import json
+import sys
+
+path = sys.argv[1]
+with open(path, "r", encoding="utf-8") as f:
+    data = json.load(f)
+
+data["config"] = {
+    "tp": 8,
+    "cuda_visible_devices": "0,1,2,3,4,5,6,7",
+    "output_len": 1,
+    "num_prompts": 1,
+    "max_concurrency": 1,
+    "request_rate": 10000,
+    "context_pad": 1024,
+}
+with open(path, "w", encoding="utf-8") as f:
+    json.dump(data, f, indent=2, ensure_ascii=False)
+PY
+
+# Ensure jq is available.
+if ! command -v jq >/dev/null 2>&1; then
+  log "ERROR: jq is required for JSON manipulation in this script"
+  exit 1
+fi
+
+stop_server sglang
+stop_server vllm
+
+run_backend sglang
+run_backend vllm
+
+log "parsing results"
+"${VENV_CLIENT}/bin/python" "${SCRIPT_DIR}/parse_results.py" "$RESULT_ROOT" >> "${LOG_DIR}/parse.log" 2>&1 || {
+  log "WARNING: parse_results.py failed; see ${LOG_DIR}/parse.log"
+}
+
+log "all results saved to ${RESULT_ROOT}"
diff --git a/experiments/dsv4_h200_max_context_length/start_sglang.sh b/experiments/dsv4_h200_max_context_length/start_sglang.sh
new file mode 100755
index 0000000..a82d5db
--- /dev/null
+++ b/experiments/dsv4_h200_max_context_length/start_sglang.sh
@@ -0,0 +1,70 @@
+#!/bin/bash
+# Start SGLang server for a specific target context length.
+set -e
+
+TARGET_LEN="${1:-}"
+if [[ -z "$TARGET_LEN" ]]; then
+  echo "Usage: $0 <target_input_length_in_tokens>"
+  exit 1
+fi
+
+cd /data/user1/yy
+mkdir -p logs
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+# shellcheck source=/dev/null
+source "${SCRIPT_DIR}/config.env"
+
+export PATH="${VENV_SGLANG}/bin:$PATH"
+export PYTHONUNBUFFERED=1
+export SGLANG_LOG_LEVEL=info
+export TMPDIR=/data/user1/yy/tmp
+export CUDA_VISIBLE_DEVICES="${CUDA_VISIBLE_DEVICES}"
+
+MAX_CONTEXT_LEN=$(( TARGET_LEN + CONTEXT_PAD ))
+
+LOG="/data/user1/yy/logs/dsv4_h200_max_context_length_sglang_${TARGET_LEN}_$(date +%Y%m%d_%H%M%S).log"
+PID_FILE="/data/user1/yy/dsv4_h200_max_context_length_sglang.pid"
+
+rm -f "$PID_FILE"
+
+echo "=== Starting SGLang server (TP=$TP, target_input_len=$TARGET_LEN, max_context_len=$MAX_CONTEXT_LEN) ==="
+echo "Model: $MODEL_PATH"
+echo "Port: $SGLANG_PORT"
+echo "Log: $LOG"
+
+nohup sglang serve \
+    --trust-remote-code \
+    --model-path "$MODEL_PATH" \
+    --tp "$TP" \
+    --moe-runner-backend marlin \
+    --context-length "$MAX_CONTEXT_LEN" \
+    --max-running-requests 1 \
+    --mem-fraction-static 0.88 \
+    --host 0.0.0.0 \
+    --port "$SGLANG_PORT" \
+    > "$LOG" 2>&1 &
+
+PID=$!
+echo $PID > "$PID_FILE"
+echo "PID: $PID"
+echo "Waiting for health..."
+
+for i in $(seq 1 240); do
+    if curl --fail --silent --show-error --max-time 5 "http://127.0.0.1:${SGLANG_PORT}/health" >/dev/null 2>&1; then
+        echo "SGLang server is ready at http://127.0.0.1:${SGLANG_PORT}"
+        echo "Log: $LOG"
+        exit 0
+    fi
+    if ! kill -0 $PID 2>/dev/null; then
+        echo "ERROR: SGLang server exited early"
+        tail -200 "$LOG"
+        exit 1
+    fi
+    echo "Waiting... ($i/240)"
+    sleep 5
+done
+
+echo "ERROR: SGLang server not healthy after 240 retries"
+tail -200 "$LOG"
+exit 1
diff --git a/experiments/dsv4_h200_max_context_length/start_vllm.sh b/experiments/dsv4_h200_max_context_length/start_vllm.sh
new file mode 100755
index 0000000..dce6692
--- /dev/null
+++ b/experiments/dsv4_h200_max_context_length/start_vllm.sh
@@ -0,0 +1,73 @@
+#!/bin/bash
+# Start vLLM server for a specific target context length.
+set -e
+
+TARGET_LEN="${1:-}"
+if [[ -z "$TARGET_LEN" ]]; then
+  echo "Usage: $0 <target_input_length_in_tokens>"
+  exit 1
+fi
+
+cd /data/user1/yy
+mkdir -p logs
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+# shellcheck source=/dev/null
+source "${SCRIPT_DIR}/config.env"
+
+VENV="${VENV_VLLM}"
+export PATH="$VENV/bin:$PATH"
+export PYTHONUNBUFFERED=1
+export TMPDIR=/data/user1/yy/tmp
+export CUDA_VISIBLE_DEVICES="${CUDA_VISIBLE_DEVICES}"
+
+MAX_MODEL_LEN=$(( TARGET_LEN + CONTEXT_PAD ))
+
+LOG="/data/user1/yy/logs/dsv4_h200_max_context_length_vllm_${TARGET_LEN}_$(date +%Y%m%d_%H%M%S).log"
+PID_FILE="/data/user1/yy/dsv4_h200_max_context_length_vllm.pid"
+
+rm -f "$PID_FILE"
+
+echo "=== Starting vLLM server (TP=$TP, target_input_len=$TARGET_LEN, max_model_len=$MAX_MODEL_LEN) ==="
+echo "Model: $MODEL_PATH"
+echo "Port: $VLLM_PORT"
+echo "Log: $LOG"
+
+nohup vllm serve "$MODEL_PATH" \
+    --trust-remote-code \
+    --tensor-parallel-size "$TP" \
+    --kv-cache-dtype fp8 \
+    --max-model-len "$MAX_MODEL_LEN" \
+    --max-num-seqs 1 \
+    --block-size 256 \
+    --gpu-memory-utilization 0.90 \
+    --tokenizer-mode deepseek_v4 \
+    --reasoning-parser deepseek_v4 \
+    --no-disable-hybrid-kv-cache-manager \
+    --disable-uvicorn-access-log \
+    --port "$VLLM_PORT" \
+    > "$LOG" 2>&1 &
+
+PID=$!
+echo $PID > "$PID_FILE"
+echo "PID: $PID"
+echo "Waiting for health..."
+
+for i in $(seq 1 240); do
+    if curl --fail --silent --show-error --max-time 5 "http://127.0.0.1:${VLLM_PORT}/health" >/dev/null 2>&1; then
+        echo "vLLM server is ready at http://127.0.0.1:${VLLM_PORT}"
+        echo "Log: $LOG"
+        exit 0
+    fi
+    if ! kill -0 $PID 2>/dev/null; then
+        echo "ERROR: vLLM server exited early"
+        tail -200 "$LOG"
+        exit 1
+    fi
+    echo "Waiting... ($i/240)"
+    sleep 5
+done
+
+echo "ERROR: vLLM server not healthy after 240 retries"
+tail -200 "$LOG"
+exit 1
diff --git a/experiments/dsv4_h200_sglang_vs_vllm/results/20260708-083346/sglang/results.json b/experiments/dsv4_h200_sglang_vs_vllm/results/20260708-083346/sglang/results.json
new file mode 100644
index 0000000..92be18f
--- /dev/null
+++ b/experiments/dsv4_h200_sglang_vs_vllm/results/20260708-083346/sglang/results.json
@@ -0,0 +1,29 @@
+{
+  "metadata": {
+    "experiment": "dsv4_h200_sglang_vs_vllm_sglang",
+    "run_id": "20260708-083346",
+    "timestamp": "2026-07-08T08:33:51+00:00",
+    "model": "/data/models/DeepSeek-V4-Flash",
+    "backend": "sglang",
+    "engine": "sglang",
+    "hardware": "8x NVIDIA H200 143GB",
+    "accelerator": "NVIDIA H200",
+    "chip": "nvidia_h200",
+    "script": "experiments/dsv4_h200_sglang_vs_vllm/run_bench.sh",
+    "env": "/data/user1/yy/envs/sglang",
+    "git_commit": "e9ed45c",
+    "git_dirty": "dirty",
+    "description": "H200 sglang TP=8 comparison benchmark for DeepSeek-V4-Flash"
+  },
+  "config": {
+    "tp": 8,
+    "cuda_visible_devices": "0,1,2,3,4,5,6,7",
+    "phase1_max_model_len": 32768,
+    "phase2_max_model_len": 210000,
+    "backend": "sglang",
+    "server_start_script": "experiments/dsv4_h200_sglang_vs_vllm/start_sglang.sh",
+    "phase1_server_args": "sglang serve --trust-remote-code --model-path /data/models/DeepSeek-V4-Flash --tp 8 --moe-runner-backend marlin --context-length 32768 --max-running-requests 256 --mem-fraction-static 0.88 --host 0.0.0.0 --port 30006",
+    "phase2_server_args": "sglang serve --trust-remote-code --model-path /data/models/DeepSeek-V4-Flash --tp 8 --moe-runner-backend marlin --context-length 210000 --max-running-requests 2 --mem-fraction-static 0.88 --host 0.0.0.0 --port 30006"
+  },
+  "scenarios": []
+}
\ No newline at end of file
diff --git a/experiments/dsv4_h200_sglang_vs_vllm/results/20260708-083346/vllm/results.json b/experiments/dsv4_h200_sglang_vs_vllm/results/20260708-083346/vllm/results.json
new file mode 100644
index 0000000..d1bc61d
--- /dev/null
+++ b/experiments/dsv4_h200_sglang_vs_vllm/results/20260708-083346/vllm/results.json
@@ -0,0 +1,29 @@
+{
+  "metadata": {
+    "experiment": "dsv4_h200_sglang_vs_vllm_vllm",
+    "run_id": "20260708-083346",
+    "timestamp": "2026-07-08T08:33:51+00:00",
+    "model": "/data/models/DeepSeek-V4-Flash",
+    "backend": "vllm",
+    "engine": "vllm",
+    "hardware": "8x NVIDIA H200 143GB",
+    "accelerator": "NVIDIA H200",
+    "chip": "nvidia_h200",
+    "script": "experiments/dsv4_h200_sglang_vs_vllm/run_bench.sh",
+    "env": "/data/user1/yy/envs/vllm",
+    "git_commit": "e9ed45c",
+    "git_dirty": "dirty",
+    "description": "H200 vllm TP=8 comparison benchmark for DeepSeek-V4-Flash"
+  },
+  "config": {
+    "tp": 8,
+    "cuda_visible_devices": "0,1,2,3,4,5,6,7",
+    "phase1_max_model_len": 32768,
+    "phase2_max_model_len": 210000,
+    "backend": "vllm",
+    "server_start_script": "experiments/dsv4_h200_sglang_vs_vllm/start_vllm.sh",
+    "phase1_server_args": "vllm serve /data/models/DeepSeek-V4-Flash --trust-remote-code --tensor-parallel-size 8 --kv-cache-dtype fp8 --max-model-len 32768 --max-num-seqs 256 --block-size 256 --gpu-memory-utilization 0.90 --tokenizer-mode deepseek_v4 --reasoning-parser deepseek_v4 --no-disable-hybrid-kv-cache-manager --disable-uvicorn-access-log --port 30005",
+    "phase2_server_args": "vllm serve /data/models/DeepSeek-V4-Flash --trust-remote-code --tensor-parallel-size 8 --kv-cache-dtype fp8 --max-model-len 210000 --max-num-seqs 2 --block-size 256 --gpu-memory-utilization 0.90 --tokenizer-mode deepseek_v4 --reasoning-parser deepseek_v4 --no-disable-hybrid-kv-cache-manager --disable-uvicorn-access-log --port 30005"
+  },
+  "scenarios": []
+}
\ No newline at end of file