[Qwen3.5] Raise Exception when radix_cache and extra_buffer are enabled at the same time (#19169)

python/sglang/srt/server_args.py

@@ -1720,6 +1720,13 @@ class ServerArgs:
             ), f"mamba extra_buffer is not supported for {model_arch} model"
 
         if self.enable_mamba_extra_buffer():  # extra_buffer
+            if self.disable_radix_cache:
+                raise ValueError(
+                    "mamba extra_buffer is not compatible with --disable-radix-cache "
+                    "Overlap scheduling is already supported with no_buffer + disable_radix_cache. "
+                    "Please use --mamba-scheduler-strategy no_buffer instead."
+                )
+
             assert (
                 is_cuda()
             ), "Mamba extra_buffer is only supported on CUDA devices with FLA backend"