diff --git a/benchmarks/multi_node/amd_utils/models.yaml b/benchmarks/multi_node/amd_utils/models.yaml
index bc2b39aa07..bc80c7d21d 100644
--- a/benchmarks/multi_node/amd_utils/models.yaml
+++ b/benchmarks/multi_node/amd_utils/models.yaml
@@ -395,6 +395,15 @@ DeepSeek-V4-Pro:
     dp:
       max_running_requests: 1024
       cuda_graph_bs_range: "1-128"
+      # Must match prefill.context_length. In PD-disagg the decode admits requests
+      # against its own context length; if left unset it defaults to the model's
+      # (huge) config value, so a request whose input exceeds prefill's 9217 budget
+      # is accepted by decode (pre-allocated, waiting for KV) but rejected by prefill
+      # (never sends KV) -> the request hangs to the client timeout (the 8k1k
+      # conc-500 straggler tail). Keeping decode symmetric with prefill makes such
+      # over-length requests fail fast at admission instead.
+      context_length: 9217
     no_dp:
       max_running_requests: 128
       cuda_graph_bs_range: "1-128"
+      context_length: 9217
diff --git a/benchmarks/multi_node/amd_utils/server_sglang.sh b/benchmarks/multi_node/amd_utils/server_sglang.sh
index ec5805eb0e..4e6b20caef 100755
--- a/benchmarks/multi_node/amd_utils/server_sglang.sh
+++ b/benchmarks/multi_node/amd_utils/server_sglang.sh
@@ -154,6 +154,7 @@ no_dp = decode.get('no_dp', {})
 # Decode DP config
 print(f'DECODE_MAX_RUNNING_REQUESTS_DP=\"{dp.get(\"max_running_requests\", 4096)}\"')
 print(f'DECODE_CHUNKED_PREFILL_SIZE_DP=\"{eval_formula(dp.get(\"chunked_prefill_size\", 262144))}\"')
+print(f'DECODE_CONTEXT_LENGTH_DP=\"{dp.get(\"context_length\", \"\")}\"')
 s, e = parse_range(dp.get('cuda_graph_bs_range', '1-160'), 1, 160)
 print(f'DECODE_CUDA_GRAPH_BS_DP_START=\"{s}\"')
 print(f'DECODE_CUDA_GRAPH_BS_DP_END=\"{e}\"')
@@ -161,6 +162,7 @@ print(f'DECODE_CUDA_GRAPH_BS_DP_END=\"{e}\"')
 # Decode EP-only config (EP enabled but DP disabled)
 print(f'DECODE_MAX_RUNNING_REQUESTS_EP_ONLY=\"{ep_only.get(\"max_running_requests\", 256)}\"')
 print(f'DECODE_CHUNKED_PREFILL_SIZE_EP_ONLY=\"{eval_formula(ep_only.get(\"chunked_prefill_size\", 262144))}\"')
+print(f'DECODE_CONTEXT_LENGTH_EP_ONLY=\"{ep_only.get(\"context_length\", \"\")}\"')
 s, e = parse_range(ep_only.get('cuda_graph_bs_range', '1-256'), 1, 256)
 print(f'DECODE_CUDA_GRAPH_BS_EP_ONLY_START=\"{s}\"')
 print(f'DECODE_CUDA_GRAPH_BS_EP_ONLY_END=\"{e}\"')
@@ -168,6 +170,7 @@ print(f'DECODE_CUDA_GRAPH_BS_EP_ONLY_END=\"{e}\"')
 # Decode no-DP config
 print(f'DECODE_MAX_RUNNING_REQUESTS_NO_DP=\"{no_dp.get(\"max_running_requests\", 128)}\"')
 print(f'DECODE_CHUNKED_PREFILL_SIZE_NO_DP=\"{eval_formula(no_dp.get(\"chunked_prefill_size\", 262144))}\"')
+print(f'DECODE_CONTEXT_LENGTH_NO_DP=\"{no_dp.get(\"context_length\", \"\")}\"')
 s, e = parse_range(no_dp.get('cuda_graph_bs_range', '1-128'), 1, 128)
 print(f'DECODE_CUDA_GRAPH_BS_NO_DP_START=\"{s}\"')
 print(f'DECODE_CUDA_GRAPH_BS_NO_DP_END=\"{e}\"')
@@ -205,12 +208,23 @@ fi
 if [[ "$DECODE_ENABLE_DP" == "true" ]]; then
     decode_cuda_graph_bs=($(seq $DECODE_CUDA_GRAPH_BS_DP_START $DECODE_CUDA_GRAPH_BS_DP_END))
     decode_max_running_requests=$((DECODE_CUDA_GRAPH_BS_DP_END * DECODE_TP_SIZE))
+    decode_context_length=$DECODE_CONTEXT_LENGTH_DP
 elif [[ "$DECODE_ENABLE_EP" == "true" ]]; then
     decode_cuda_graph_bs=($(seq $DECODE_CUDA_GRAPH_BS_EP_ONLY_START $DECODE_CUDA_GRAPH_BS_EP_ONLY_END))
     decode_max_running_requests=$DECODE_MAX_RUNNING_REQUESTS_EP_ONLY
+    decode_context_length=$DECODE_CONTEXT_LENGTH_EP_ONLY
 else
     decode_cuda_graph_bs=($(seq $DECODE_CUDA_GRAPH_BS_NO_DP_START $DECODE_CUDA_GRAPH_BS_NO_DP_END))
     decode_max_running_requests=$DECODE_MAX_RUNNING_REQUESTS_NO_DP
+    decode_context_length=$DECODE_CONTEXT_LENGTH_NO_DP
+fi
+# In PD-disaggregation the decode must admit requests against the SAME context
+# length as prefill; otherwise decode accepts over-length requests that prefill
+# rejects, and those requests hang forever waiting for a KV transfer that never
+# comes (the 8k1k conc-500 straggler). Fall back to the prefill value if the
+# decode context_length is not set in the model config, so the two always agree.
+if [[ -z "$decode_context_length" ]]; then
+    decode_context_length=$prefill_context_length
 fi
 
 # When both DP and EP are enabled, override max-running-requests and dispatch tokens
@@ -251,6 +265,9 @@ DECODE_MODE_FLAGS="--mem-fraction-static ${DECODE_MEM_FRACTION_STATIC} --max-run
 if [[ "$DECODE_PREFILL_ROUND_ROBIN_BALANCE" == "True" ]] || [[ "$DECODE_PREFILL_ROUND_ROBIN_BALANCE" == "true" ]]; then
     DECODE_MODE_FLAGS="$DECODE_MODE_FLAGS --prefill-round-robin-balance"
 fi
+if [[ -n "$decode_context_length" ]]; then
+    DECODE_MODE_FLAGS="$DECODE_MODE_FLAGS --context-length ${decode_context_length}"
+fi
 
 if [[ "$DECODE_MTP_SIZE" -gt 0 ]]; then
     MORI_MAX_DISPATCH_TOKENS_DECODE=$((MORI_MAX_DISPATCH_TOKENS_DECODE * (DECODE_MTP_SIZE + 1)))