diff --git a/experiments/dsv4_p800_256k_4k_probe/config.env b/experiments/dsv4_p800_256k_4k_probe/config.env
index de8af0a..d03041a 100644
--- a/experiments/dsv4_p800_256k_4k_probe/config.env
+++ b/experiments/dsv4_p800_256k_4k_probe/config.env
@@ -20,7 +20,9 @@ SERVER_MODE="${SERVER_MODE:-w8a8_int8_baseline}"
 
 # Extra SGLang launch arguments for the 256k-context probe.
 # 262144 input + 4096 output + padding -> use 270000.
-SGLANG_EXTRA_LAUNCH_ARGS="${SGLANG_EXTRA_LAUNCH_ARGS:---context-length 270000 --max-running-requests 4}"
+# max-running-requests=2 matches the probe concurrency; mem-fraction-static
+# limits the KV cache reservation to avoid OOM on P800.
+SGLANG_EXTRA_LAUNCH_ARGS="${SGLANG_EXTRA_LAUNCH_ARGS:---context-length 270000 --max-running-requests 2 --mem-fraction-static 0.85}"
 
 # Scenario list: "concurrency input_len output_len" (one per line).
 SCENARIOS=(
diff --git a/experiments/dsv4_p800_256k_4k_probe/run_bench.sh b/experiments/dsv4_p800_256k_4k_probe/run_bench.sh
index c37a0fa..fdf10e5 100755
--- a/experiments/dsv4_p800_256k_4k_probe/run_bench.sh
+++ b/experiments/dsv4_p800_256k_4k_probe/run_bench.sh
@@ -65,7 +65,7 @@ data["config"] = {
     "context_length": 270000,
     "server_mode": "w8a8_int8_baseline",
     "server_start_script": f"experiments/{data['metadata']['experiment']}/start_server.sh",
-    "extra_launch_args": "--context-length 270000 --max-running-requests 4",
+    "extra_launch_args": "--context-length 270000 --max-running-requests 2 --mem-fraction-static 0.85",
     "scenarios": ["2 262144 4096"],
     "num_prompts": 4
 }
diff --git a/experiments/dsv4_p800_long_context_matrix/README.md b/experiments/dsv4_p800_long_context_matrix/README.md
new file mode 100644
index 0000000..d5b7c20
--- /dev/null
+++ b/experiments/dsv4_p800_long_context_matrix/README.md
@@ -0,0 +1,52 @@
+# DSV4 P800 Long-Context Matrix
+
+Kunlun P800 XPU + SGLang + `DeepSeek-V4-Flash-INT8` long-context matrix benchmark.
+
+## What it does
+
+Runs a grid of input/output lengths to measure SGLang long-context serving
+performance on P800:
+
+- Input lengths: 64k, 128k, 256k
+- Output lengths: 256, 1k, 4k
+- Concurrency: 25 for 64k; 10, 5, 2 for 128k and 256k
+
+Each context group (64k / 128k / 256k) is started with its own server instance
+using the appropriate `--context-length` and `--max-running-requests`.
+
+## Quick Start
+
+```bash
+# Run the full matrix (starts server per group, runs all scenarios, stops server)
+PLATFORM=kunlun_p800 bash experiments/dsv4_p800_long_context_matrix/run_bench.sh
+```
+
+Results land in `experiments/dsv4_p800_long_context_matrix/results/<RUN_ID>/`.
+
+## Configuration
+
+Edit `config.env` or override via environment variables:
+
+```bash
+# Run with the tuned EAGLE speculative-decoding config instead of the baseline
+SERVER_MODE=w8a8_int8 PLATFORM=kunlun_p800 \
+bash experiments/dsv4_p800_long_context_matrix/run_bench.sh
+
+# Reduce concurrency for the 256k group if OOM occurs
+CONTEXT_GROUPS=("64k 80000 25" "128k 140000 10" "256k 270000 5") \
+PLATFORM=kunlun_p800 \
+bash experiments/dsv4_p800_long_context_matrix/run_bench.sh
+```
+
+## Files
+
+| File | Purpose |
+|---|---|
+| `config.env` | Experiment-level configuration (model, scenarios, context groups) |
+| `start_server.sh` | Start the P800 SGLang Docker container for a context group |
+| `run_bench.sh` | Orchestrator: server per group → warmup → scenarios → parse |
+
+## Platform
+
+This experiment targets `platforms/kunlun_p800.env` and uses
+`scripts/common/server_docker.sh` / `scripts/common/bench_client_docker.sh`.
diff --git a/experiments/dsv4_p800_long_context_matrix/config.env b/experiments/dsv4_p800_long_context_matrix/config.env
new file mode 100644
index 0000000..f836732
--- /dev/null
+++ b/experiments/dsv4_p800_long_context_matrix/config.env
@@ -0,0 +1,60 @@
+# Long-context matrix for SGLang on DeepSeek-V4-Flash-INT8 (Kunlun P800, TP=8).
+# Input lengths: 64k, 128k, 256k
+# Output lengths: 256, 1k, 4k
+# Concurrency: 25 for 64k; 10, 5, 2 for 128k and 256k
+
+EXPERIMENT="${EXPERIMENT:-dsv4_p800_long_context_matrix}"
+MODEL_NAME="${MODEL_NAME:-DeepSeek-V4-Flash-INT8}"
+MODEL_PATH="${MODEL_PATH:-/data1/models/DeepSeek-V4-Flash-INT8}"
+SERVED_MODEL_NAME="${SERVED_MODEL_NAME:-deepseek-v4-flash-int8}"
+PORT="${PORT:-30000}"
+BACKEND="${BACKEND:-sglang}"
+ENGINE="${ENGINE:-sglang-xpu}"
+DATASET="${DATASET:-random}"
+DATASET_PATH="${DATASET_PATH:-/workspace/dummy_sharegpt.json}"
+
+# Server launch mode for P800 SGLang.
+#   - "w8a8_int8"         : DeepSeek-V4-Flash-INT8 checkpoint with EAGLE speculative decoding
+#   - "w8a8_int8_baseline": DeepSeek-V4-Flash-INT8 checkpoint without speculative decoding
+SERVER_MODE="${SERVER_MODE:-w8a8_int8_baseline}"
+
+# Per-context server settings. Each group is run with its own server start.
+# Format: "input_label context_length max_running"
+declare -a CONTEXT_GROUPS=(
+  "64k  80000  25"
+  "128k 140000 10"
+  "256k 270000 10"
+)
+
+# Scenarios per group: "concurrency input_len output_len num_prompts"
+declare -a SCENARIOS_64K=(
+  "25 65536  256  50"
+  "25 65536  1024 50"
+  "25 65536  4096 50"
+)
+
+declare -a SCENARIOS_128K=(
+  "10 131072 256  20"
+  "5  131072 256  10"
+  "2  131072 256  4"
+  "10 131072 1024 20"
+  "5  131072 1024 10"
+  "2  131072 1024 4"
+  "10 131072 4096 20"
+  "5  131072 4096 10"
+  "2  131072 4096 4"
+)
+
+declare -a SCENARIOS_256K=(
+  "10 262144 256  20"
+  "5  262144 256  10"
+  "2  262144 256  4"
+  "10 262144 1024 20"
+  "5  262144 1024 10"
+  "2  262144 1024 4"
+  "10 262144 4096 20"
+  "5  262144 4096 10"
+  "2  262144 4096 4"
+)
+
+WARMUP="${WARMUP:-0}"
diff --git a/experiments/dsv4_p800_long_context_matrix/run_bench.sh b/experiments/dsv4_p800_long_context_matrix/run_bench.sh
new file mode 100755
index 0000000..95df3d3
--- /dev/null
+++ b/experiments/dsv4_p800_long_context_matrix/run_bench.sh
@@ -0,0 +1,255 @@
+#!/usr/bin/env bash
+# Long-context matrix for SGLang on DeepSeek-V4-Flash-INT8 (Kunlun P800).
+set -Eeuo pipefail
+
+SCRIPT_DIR="$(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 "${SCRIPT_DIR}/../../scripts/common/server_docker.sh"
+# shellcheck source=/dev/null
+source "${SCRIPT_DIR}/../../scripts/common/bench_client_docker.sh"
+# shellcheck source=/dev/null
+source "${SCRIPT_DIR}/config.env"
+
+RUN_ID="${RUN_ID:-$(date '+%Y%m%d-%H%M%S')}"
+RESULT_BASE="${SCRIPT_DIR}/results"
+
+log_dir_global="${RESULT_BASE}/${RUN_ID}/logs"
+mkdir -p "$log_dir_global"
+log_init "${log_dir_global}/orchestrator.log"
+
+log "experiment=${EXPERIMENT_NAME}"
+log "run_id=${RUN_ID}"
+log "platform=${PLATFORM}"
+log "hardware=${HARDWARE}"
+log "model=${MODEL_PATH}"
+log "server_mode=${SERVER_MODE}"
+log "groups=${#CONTEXT_GROUPS[@]}"
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+is_server_healthy() {
+  curl --fail --silent --show-error --max-time 5 "http://127.0.0.1:${PORT}/health" >/dev/null 2>&1
+}
+
+start_server() {
+  local context_length="$1"
+  local max_running="$2"
+  local extra_args="--context-length ${context_length} --max-running-requests ${max_running} --mem-fraction-static 0.85"
+  export SGLANG_EXTRA_LAUNCH_ARGS="${SGLANG_EXTRA_LAUNCH_ARGS:-${extra_args}}"
+
+  log "starting server (context_length=${context_length}, max_running=${max_running}, mode=${SERVER_MODE})"
+  docker_server_start "${MODEL_PATH}" "${PORT}" "${log_dir_global}/server_${context_length}.outer.log" "${SERVER_MODE}" "${SGLANG_EXTRA_LAUNCH_ARGS}"
+}
+
+stop_server() {
+  docker_server_stop
+}
+
+run_warmup() {
+  local raw_dir="$1"
+  local phase_log_dir="$2"
+  local input_len="$3"
+  local output_len="${4:-256}"
+
+  log "warming up (input=${input_len}, output=${output_len}, num=1)"
+
+  local tmp_warmup_file="/tmp/bench_outputs/${CHIP}_${ENGINE}_$(date '+%m%d')_warmup_1_${input_len}_${output_len}.jsonl"
+  local host_warmup_file="${raw_dir}/${BACKEND}_warmup_$(date '+%m%d')_1_${input_len}_${output_len}.jsonl"
+  local detail_log="${phase_log_dir}/warmup_${input_len}_${output_len}.log"
+
+  if WARMUP=0 run_random_case \
+      "$BACKEND" "$PORT" "$MODEL_PATH" "$tmp_warmup_file" \
+      1 "$input_len" "$output_len" 1 "${DATASET_PATH:-}" \
+      > "$detail_log" 2>&1; then
+    docker cp "${CONTAINER_NAME}:${tmp_warmup_file}" "$host_warmup_file" 2>/dev/null || true
+    log "warmup completed"
+  else
+    log "WARNING: warmup failed; continuing with group"
+  fi
+}
+
+scenario_already_completed() {
+  local output_file="$1"
+  local expected="$2"
+  [[ -s "$output_file" ]] || return 1
+  local completed
+  completed="$(python3 -c "
+import json, sys
+path = sys.argv[1]
+try:
+    with open(path, 'r', encoding='utf-8') as f:
+        for line in f:
+            line = line.strip()
+            if line:
+                data = json.loads(line)
+                print(data.get('completed', 0))
+                break
+except Exception:
+    print(0)
+" "$output_file")"
+  [[ "${completed:-0}" -ge "$expected" ]]
+}
+
+run_group() {
+  local group_label="$1"
+  local context_length="$2"
+  local max_running="$3"
+  local -n scenarios_ref="$4"
+
+  local result_root="${RESULT_BASE}/${RUN_ID}/${BACKEND}"
+  local raw_dir="${result_root}/raw_outputs"
+  local phase_log_dir="${result_root}/logs"
+
+  mkdir -p "$raw_dir" "$phase_log_dir"
+
+  log "===== ${BACKEND} ${group_label} START (context_length=${context_length}) ====="
+
+  stop_server
+  if ! start_server "$context_length" "$max_running"; then
+    log "ERROR: server failed to start for ${group_label}; skipping group"
+    stop_server
+    return 1
+  fi
+
+  # Warmup with the shortest output for this input length to save time.
+  local warmup_input="${scenarios_ref[0]}"
+  local warmup_input_len
+  warmup_input_len="$(echo "$warmup_input" | awk '{print $2}')"
+  run_warmup "$raw_dir" "$phase_log_dir" "$warmup_input_len" 256
+
+  for scenario in "${scenarios_ref[@]}"; do
+    # Allow SCENARIOS to be passed as a string like "(25 65536 256 50)" from env.
+    scenario="${scenario//[()]/}"
+    read -r concurrency input_len output_len num_prompts <<< "$scenario"
+
+    tmp_output_file="/tmp/bench_outputs/${CHIP}_${ENGINE}_$(date '+%m%d')_${concurrency}_${input_len}_${output_len}.jsonl"
+    output_file="${raw_dir}/${BACKEND}_${group_label}_$(date '+%m%d')_${concurrency}_${input_len}_${output_len}.jsonl"
+    detail_log="${phase_log_dir}/${BACKEND}_${group_label}_c${concurrency}_i${input_len}_o${output_len}.log"
+
+    if scenario_already_completed "$output_file" "$num_prompts"; then
+      log "skipping already-completed ${BACKEND} ${group_label} scenario: c=${concurrency} i=${input_len} o=${output_len}"
+      continue
+    fi
+
+    log "running ${BACKEND} ${group_label} scenario: c=${concurrency} i=${input_len} o=${output_len} n=${num_prompts}"
+
+    if run_random_case \
+        "$BACKEND" "$PORT" "$MODEL_PATH" "$tmp_output_file" \
+        "$concurrency" "$input_len" "$output_len" "$num_prompts" \
+        "${DATASET_PATH:-}" \
+        > "$detail_log" 2>&1; then
+      docker cp "${CONTAINER_NAME}:${tmp_output_file}" "$output_file" || {
+        log "ERROR: failed to copy ${tmp_output_file} from container"
+        continue
+      }
+      log "finished ${BACKEND} ${group_label} scenario: output=${output_file}"
+    else
+      log "ERROR: ${BACKEND} ${group_label} scenario c=${concurrency} i=${input_len} o=${output_len} failed; see ${detail_log}"
+      continue
+    fi
+  done
+
+  stop_server
+  log "===== ${BACKEND} ${group_label} DONE ====="
+}
+
+parse_backend() {
+  local result_root="${RESULT_BASE}/${RUN_ID}/${BACKEND}"
+  log "parsing ${BACKEND} results in ${result_root}"
+  python3 "${SCRIPT_DIR}/../../scripts/common/parse_backend.py" "$result_root" --backend "$BACKEND" \
+    >> "${result_root}/logs/parse.log" 2>&1 || {
+      log "WARNING: parser failed for ${BACKEND}; see ${result_root}/logs/parse.log"
+    }
+}
+
+write_backend_metadata() {
+  local result_root="${RESULT_BASE}/${RUN_ID}/${BACKEND}"
+  ensure_result_root "$result_root"
+  local meta_json="${result_root}/results.json"
+
+  write_metadata_json \
+    "$meta_json" \
+    "${EXPERIMENT_NAME}_${BACKEND}" \
+    "$RUN_ID" \
+    "$MODEL_PATH" \
+    "$BACKEND" \
+    "$ENGINE" \
+    "$HARDWARE" \
+    "$ACCELERATOR" \
+    "$CHIP" \
+    "experiments/${EXPERIMENT_NAME}/run_bench.sh" \
+    "" \
+    "Kunlun P800 long-context matrix ${BACKEND} TP=8 for DeepSeek-V4-Flash-INT8"
+
+  # Build groups JSON from CONTEXT_GROUPS.
+  local groups_json="["
+  local first=1
+  for group in "${CONTEXT_GROUPS[@]}"; do
+    read -r label context_length max_running <<< "$group"
+    if [[ "$first" -eq 1 ]]; then
+      first=0
+    else
+      groups_json+=","
+    fi
+    groups_json+="{\"label\":\"${label}\",\"context_length\":${context_length},\"max_running\":${max_running}}"
+  done
+  groups_json+="]"
+
+  # Embed config.
+  python3 - "$meta_json" "$groups_json" <<'PY' >/dev/null
+import json
+import sys
+
+path = sys.argv[1]
+groups = json.loads(sys.argv[2])
+
+with open(path, "r", encoding="utf-8") as f:
+    data = json.load(f)
+
+data["config"] = {
+    "tp": 8,
+    "xpu_visible_devices": "0,1,2,3,4,5,6,7",
+    "backend": data["metadata"]["backend"],
+    "engine": data["metadata"]["engine"],
+    "server_mode": "w8a8_int8_baseline",
+    "server_start_script": f"experiments/{data['metadata']['experiment']}/start_server.sh",
+    "groups": groups
+}
+with open(path, "w", encoding="utf-8") as f:
+    json.dump(data, f, indent=2, ensure_ascii=False)
+PY
+}
+
+# ---------------------------------------------------------------------------
+# Main
+# ---------------------------------------------------------------------------
+
+# Cleanup any leftovers.
+stop_server
+
+write_backend_metadata
+
+for group in "${CONTEXT_GROUPS[@]}"; do
+  read -r group_label context_length max_running <<< "$group"
+
+  # Resolve scenario array for this group.
+  scenario_array_name="SCENARIOS_${group_label^^}"
+  if [[ -z "${!scenario_array_name:-}" ]]; then
+    log "WARNING: no scenarios defined for group ${group_label}"
+    continue
+  fi
+
+  run_group "$group_label" "$context_length" "$max_running" "$scenario_array_name"
+done
+
+parse_backend
+
+log "all results saved to ${RESULT_BASE}/${RUN_ID}"
diff --git a/experiments/dsv4_p800_long_context_matrix/start_server.sh b/experiments/dsv4_p800_long_context_matrix/start_server.sh
new file mode 100755
index 0000000..5b5bcf6
--- /dev/null
+++ b/experiments/dsv4_p800_long_context_matrix/start_server.sh
@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# Start SGLang server for the P800 long-context matrix.
+# Usage: start_server.sh <context_length> <max_running>
+set -Eeuo pipefail
+
+CONTEXT_LENGTH="${1:-80000}"
+MAX_RUNNING="${2:-64}"
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+EXPERIMENT_NAME="$(basename "$SCRIPT_DIR")"
+
+# shellcheck source=/dev/null
+source "${SCRIPT_DIR}/../../scripts/common/server_docker.sh"
+# shellcheck source=/dev/null
+source "${SCRIPT_DIR}/config.env"
+
+log_init "${RESULT_ROOT:-/tmp/${EXPERIMENT_NAME}}/logs/start_server.log"
+log "starting server for ${EXPERIMENT_NAME}"
+log "model: ${MODEL_PATH}"
+log "port: ${PORT}"
+log "server mode: ${SERVER_MODE}"
+log "context length: ${CONTEXT_LENGTH}"
+log "max running requests: ${MAX_RUNNING}"
+
+extra_args="--context-length ${CONTEXT_LENGTH} --max-running-requests ${MAX_RUNNING} --mem-fraction-static 0.85"
+export SGLANG_EXTRA_LAUNCH_ARGS="${SGLANG_EXTRA_LAUNCH_ARGS:-${extra_args}}"
+
+docker_server_start "${MODEL_PATH}" "${PORT}" "${LOG_DIR}/server.outer.log" "${SERVER_MODE}" "${SGLANG_EXTRA_LAUNCH_ARGS}"
diff --git a/scripts/common/bench_client_docker.sh b/scripts/common/bench_client_docker.sh
index 504412d..6b3de60 100755
--- a/scripts/common/bench_client_docker.sh
+++ b/scripts/common/bench_client_docker.sh
@@ -63,7 +63,7 @@ run_random_case() {
     --random-input-len "$input_len"
     --random-output-len "$output_len"
     --num-prompts "$num_prompts"
-    --max-concurrency "$concurrency"
+    --concurrency "$concurrency"
     --warmup-requests "$warmup"
     --output-file "$output_file"
     --output-details
diff --git a/scripts/common/server_docker.sh b/scripts/common/server_docker.sh
index 521b85a..3d82312 100755
--- a/scripts/common/server_docker.sh
+++ b/scripts/common/server_docker.sh
@@ -206,11 +206,12 @@ EOF
     bash -c "echo '${server_cmd_b64}' | base64 -d | bash" \
     >> "${server_log}" 2>&1
 
-  log "container ${container} started, waiting for health"
-  if health_check 127.0.0.1 "$port" 600; then
+  local health_wait="${SGLANG_HEALTH_CHECK_TIMEOUT:-600}"
+  log "container ${container} started, waiting for health (timeout=${health_wait}s)"
+  if health_check 127.0.0.1 "$port" "$health_wait"; then
     log "container ${container} is healthy"
   else
-    log "ERROR: container ${container} failed health check"
+    log "ERROR: container ${container} failed health check after ${health_wait}s"
     return 1
   fi
 }