diff --git a/python/sglang/srt/server_args.py b/python/sglang/srt/server_args.py
index af7a05f95..ac6cb90e2 100644
--- a/python/sglang/srt/server_args.py
+++ b/python/sglang/srt/server_args.py
@@ -549,7 +549,7 @@ class ServerArgs:
     enable_piecewise_cuda_graph: bool = False
     enable_torch_compile_debug_mode: bool = False
     torch_compile_max_bs: int = 32
-    piecewise_cuda_graph_max_tokens: int = 4096
+    piecewise_cuda_graph_max_tokens: Optional[int] = None
     piecewise_cuda_graph_tokens: Optional[List[int]] = None
     piecewise_cuda_graph_compiler: str = "eager"
     torchao_config: str = ""
@@ -895,6 +895,12 @@ class ServerArgs:
         else:
             self.cuda_graph_max_bs = max(self.cuda_graph_bs)
 
+        if self.piecewise_cuda_graph_max_tokens is None:
+            # Capture piecewise cuda graph tokens up to the chunked prefill size. Two benefits:
+            # 1. cuda graph acceleration for all prefill lengths.
+            # 2. do not need more temporary memory for activations. Less fragmentation.
+            self.piecewise_cuda_graph_max_tokens = self.chunked_prefill_size
+
         if self.piecewise_cuda_graph_tokens is None:
             self.piecewise_cuda_graph_tokens = (
                 self._generate_piecewise_cuda_graph_tokens()
@@ -936,7 +942,7 @@ class ServerArgs:
 
             # For piecewise cuda graphs
             if self.enable_piecewise_cuda_graph:
-                reserved_mem += self.piecewise_cuda_graph_max_tokens // 4
+                reserved_mem += self.piecewise_cuda_graph_max_tokens // 8
 
             self.mem_fraction_static = (
                 round((gpu_mem - reserved_mem) / gpu_mem, 3)