diff --git a/python/sglang/srt/layers/attention/mamba/mamba.py b/python/sglang/srt/layers/attention/mamba/mamba.py
index b8d49db97..286c51de9 100644
--- a/python/sglang/srt/layers/attention/mamba/mamba.py
+++ b/python/sglang/srt/layers/attention/mamba/mamba.py
@@ -534,6 +534,9 @@ class MambaMixer2(torch.nn.Module):
                     layer_cache, MambaPool.SpeculativeState
                 ), "layer_cache must be SpeculativeState for speculative decoding"
                 draft_token_num = metadata.draft_token_num
+                self.intermediate_state_indices = torch.arange(
+                    num_decodes, dtype=torch.int32, device=state_indices_tensor_d.device
+                )
 
                 # Reshape for batch processing
                 hidden_states_B_C_d_reshaped = hidden_states_B_C_d.view(
@@ -548,6 +551,7 @@ class MambaMixer2(torch.nn.Module):
                     self.activation,
                     conv_state_indices=state_indices_tensor_d[:num_decodes],
                     intermediate_conv_window=layer_cache.intermediate_conv_window[0],
+                    intermediate_state_indices=self.intermediate_state_indices,
                     retrieve_next_token=metadata.retrieve_next_token,
                     retrieve_next_sibling=metadata.retrieve_next_sibling,
                     retrieve_parent_token=metadata.retrieve_parent_token,
@@ -621,6 +625,7 @@ class MambaMixer2(torch.nn.Module):
                     intermediate_states_buffer=layer_cache.intermediate_ssm,
                     cache_steps=draft_token_num,
                     retrieve_parent_token=metadata.retrieve_parent_token,
+                    intermediate_state_indices=self.intermediate_state_indices,
                 )
             else:
                 selective_state_update(
diff --git a/python/sglang/srt/layers/attention/mamba/ops/mamba_ssm.py b/python/sglang/srt/layers/attention/mamba/ops/mamba_ssm.py
index 97039d675..f238d51b4 100644
--- a/python/sglang/srt/layers/attention/mamba/ops/mamba_ssm.py
+++ b/python/sglang/srt/layers/attention/mamba/ops/mamba_ssm.py
@@ -56,6 +56,14 @@ else:
         is not None
     }
 )
+@triton.heuristics(
+    {
+        "HAS_INTERMEDIATE_STATE_INDICES": lambda args: args[
+            "intermediate_state_indices_ptr"
+        ]
+        is not None
+    }
+)
 @triton.jit(do_not_specialize=["T"])
 def _selective_scan_update_kernel(
     # Pointers to matrices
@@ -74,6 +82,7 @@ def _selective_scan_update_kernel(
     intermediate_states_buffer,
     cache_steps,
     retrieve_parent_token_ptr,
+    intermediate_state_indices_ptr,
     # Matrix dimensions
     batch,
     T,
@@ -130,6 +139,7 @@ def _selective_scan_update_kernel(
     DISABLE_STATE_UPDATE: tl.constexpr,
     CACHE_INTERMEDIATE_STATES: tl.constexpr,
     HAS_EAGLE_TREE_CUSTOM_ATTN_MASK: tl.constexpr,
+    HAS_INTERMEDIATE_STATE_INDICES: tl.constexpr,
     BLOCK_SIZE_DSTATE: tl.constexpr,
 ):
     pid_m = tl.program_id(axis=0)
@@ -177,7 +187,12 @@ def _selective_scan_update_kernel(
 
     cache_idx = -1
     if CACHE_INTERMEDIATE_STATES:
-        if HAS_STATE_BATCH_INDICES:
+        if HAS_INTERMEDIATE_STATE_INDICES:
+            intermediate_state_idx = tl.load(intermediate_state_indices_ptr + pid_b).to(
+                tl.int64
+            )
+            cache_idx = intermediate_state_idx
+        elif HAS_STATE_BATCH_INDICES:
             cache_idx = state_batch_idx
         else:
             cache_idx = pid_b
@@ -250,7 +265,7 @@ def _selective_scan_update_kernel(
                 if state_batch_idx != pad_slot_id:
                     cache_ptr_base = (
                         intermediate_states_buffer
-                        + state_batch_idx * cache_steps * nheads * dim * dstate
+                        + cache_idx * cache_steps * nheads * dim * dstate
                         + current_step_idx * nheads * dim * dstate
                         + pid_h * dim * dstate
                     )
@@ -300,6 +315,7 @@ def selective_state_update(
     intermediate_states_buffer=None,
     cache_steps=None,
     retrieve_parent_token=None,
+    intermediate_state_indices=None,
 ):
     """
     Argument:
@@ -324,6 +340,8 @@ def selective_state_update(
         intermediate_states_buffer: Buffer to cache intermediate states
         cache_steps: Total number of steps in the buffer
         retrieve_parent_token: (batch, T) tensor of parent token indices for EAGLE tree attention
+        intermediate_state_indices: (batch,) tensor of indices for intermediate_states_buffer operations.
+            If provided, uses these indices instead of state_batch_indices for the buffer.
     """
     if state.dim() == 3:
         state = state.unsqueeze(1)
@@ -426,6 +444,7 @@ def selective_state_update(
             intermediate_states_buffer,
             cache_steps if cache_steps is not None else 0,
             retrieve_parent_token,
+            intermediate_state_indices,
             batch,
             T,
             nheads,
diff --git a/python/sglang/srt/server_args.py b/python/sglang/srt/server_args.py
index 261895b01..a870358d1 100644
--- a/python/sglang/srt/server_args.py
+++ b/python/sglang/srt/server_args.py
@@ -1376,7 +1376,13 @@ class ServerArgs:
                 else:
                     self.quantization = model_config.quantization
                 self.moe_runner_backend = "flashinfer_cutlass"
-            if not self.disable_radix_cache:
+
+            if not self.disable_radix_cache and self.speculative_algorithm is not None:
+                logger.warning(
+                    "Disabling radix cache since speculative decoding for NemotronHForCausalLM is not supported with radix cache yet."
+                )
+                self.disable_radix_cache = True
+            elif not self.disable_radix_cache:
                 logger.warning(
                     "Disabling overlap schedule since MambaRadixCache is not compatible with "
                     "overlap schedule currently, try to use --disable-radix-cache if overlap schedule is necessary"