[Qwen3-next] support mamba radix cache for overlap scheduler (#14792)

docs/advanced_features/server_arguments.md

@@ -303,6 +303,8 @@ Please consult the documentation below and [server_args.py](https://github.com/s
 | `--max-mamba-cache-size` | The maximum size of the mamba cache. | `None` | Type: int |
 | `--mamba-ssm-dtype` | The data type of the SSM states in mamba cache. | `float32` | `float32`, `bfloat16` |
 | `--mamba-full-memory-ratio` | The ratio of mamba state memory to full kv cache memory. | `0.2` | Type: float |
+| `--mamba-scheduler-strategy` | The strategy to use for mamba scheduler. `auto` currently defaults to `no_buffer`. 1. `no_buffer` does not support overlap scheduler due to not allocating extra mamba state buffers. Branching point caching support is feasible but not implemented. 2. `extra_buffer` supports overlap schedule by allocating extra mamba state buffers to track mamba state for caching (mamba state usage per running req becomes `2x` for non-spec; `1+(1/(2+speculative_num_draft_tokens))x` for spec dec (e.g. 1.16x if speculative_num_draft_tokens==4)). 2a. `extra_buffer` is strictly better for non-KV-cache-bound cases; for KV-cache-bound cases, the tradeoff depends on whether enabling overlap outweighs reduced max running requests. 2b. mamba caching at radix cache branching point is strictly better than non-branch but requires kernel support (currently only FLA backend), currently only extra_buffer supports branching. | `auto` | `auto`, `no_buffer`, `extra_buffer` |
+| `--mamba-track-interval` | The interval (in tokens) to track the mamba state during decode. Only used when `--mamba-scheduler-strategy` is `extra_buffer`. Must be divisible by page_size if set, and must be >= speculative_num_draft_tokens when using speculative decoding. | `256` | Type: int |
 
 ## Args for multi-item scoring
 | Argument | Description | Defaults | Options |

python/sglang/srt/disaggregation/decode.py

@@ -155,8 +155,16 @@ class HybridMambaDecodeReqToTokenPool(HybridReqToTokenPool):
             pre_alloc_size=pre_alloc_size,
         )
         self.enable_memory_saver = enable_memory_saver
+        self.enable_mamba_extra_buffer = (
+            False  # TODO: add PD support for mamba cache extra_buffer
+        )
         self._init_mamba_pool(
-            size + pre_alloc_size, cache_params, device, speculative_num_draft_tokens
+            size=size + pre_alloc_size,
+            mamba_spec_state_size=size + pre_alloc_size,
+            cache_params=cache_params,
+            device=device,
+            enable_mamba_extra_buffer=self.enable_mamba_extra_buffer,
+            speculative_num_draft_tokens=speculative_num_draft_tokens,
         )
 
     def clear(self):

python/sglang/srt/layers/attention/fla/chunk.py

@@ -67,7 +67,7 @@ def chunk_gated_delta_rule_fwd(
         cu_seqlens=cu_seqlens,
     )
     if SUPPRESS_LEVEL < 3:
-        return g, o, A, final_state, None, None, None
+        return g, o, A, final_state, None, h, None
     elif SUPPRESS_LEVEL >= 3:
         return g, o, A, final_state, w, h, v_new
 
@@ -108,7 +108,7 @@ class ChunkGatedDeltaRuleFunction(torch.autograd.Function):
             output_final_state=output_final_state,
             cu_seqlens=cu_seqlens,
         )
-        return o.to(q.dtype), final_state
+        return o.to(q.dtype), final_state, h
 
 
 @torch.compiler.disable
@@ -224,7 +224,7 @@ def chunk_gated_delta_rule(
             )
     if scale is None:
         scale = k.shape[-1] ** -0.5
-    o, final_state = ChunkGatedDeltaRuleFunction.apply(
+    o, final_state, h = ChunkGatedDeltaRuleFunction.apply(
         q,
         k,
         v,
@@ -238,4 +238,4 @@ def chunk_gated_delta_rule(
     )
     if head_first:
         o = rearrange(o, "b t h ... -> b h t ...")
-    return o, final_state
+    return o, final_state, h

python/sglang/srt/layers/attention/fla/chunk_delta_h.py

@@ -16,6 +16,7 @@ from sglang.srt.layers.attention.fla.op import exp, safe_exp
 from sglang.srt.layers.attention.fla.utils import is_nvidia_hopper
 
 NUM_WARPS = [2, 4] if is_nvidia_hopper else [2, 4, 8, 16]
+CHUNK_SIZE = 64
 
 
 # @triton.autotune(
@@ -274,16 +275,15 @@ def chunk_gated_delta_rule_fwd_h(
     gk: Optional[torch.Tensor] = None,
     initial_state: Optional[torch.Tensor] = None,
     output_final_state: bool = False,
-    chunk_size: int = 64,  # SY: remove this argument and force chunk size 64?
     save_new_value: bool = True,
     cu_seqlens: Optional[torch.LongTensor] = None,
-) -> Tuple[torch.Tensor, torch.Tensor]:
+) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
     B, T, Hg, K, V = *k.shape, u.shape[-1]
     H = u.shape[-2]
-    BT = chunk_size
+    BT = CHUNK_SIZE
 
     chunk_indices = (
-        prepare_chunk_indices(cu_seqlens, chunk_size)
+        prepare_chunk_indices(cu_seqlens, CHUNK_SIZE)
         if cu_seqlens is not None
         else None
     )

python/sglang/srt/layers/attention/fla/fused_recurrent.py

@@ -353,6 +353,7 @@ def fused_recurrent_gated_delta_rule_update_fwd_kernel(
     cu_seqlens,
     scale,
     intermediate_states_buffer,
+    intermediate_state_indices,
     cache_steps,
     retrieve_parent_token_ptr,
     stride_retrieve_parent_token_seq: tl.constexpr,
@@ -431,7 +432,7 @@ def fused_recurrent_gated_delta_rule_update_fwd_kernel(
     # Prepare intermediate state cache variables if enabled
     cache_idx = -1
     if CACHE_INTERMEDIATE_STATES:
-        cache_idx = tl.load(h0_indices + i_n)
+        cache_idx = tl.load(intermediate_state_indices + i_n)
 
     step_idx = 0
     for _ in range(0, T):
@@ -532,6 +533,7 @@ def fused_recurrent_gated_delta_rule_update_fwd(
     disable_state_update: bool = False,
     disable_output_calculation: bool = False,
     intermediate_states_buffer: Optional[torch.Tensor] = None,
+    intermediate_state_indices: Optional[torch.Tensor] = None,
     cache_steps: Optional[int] = None,
     retrieve_parent_token: Optional[torch.Tensor] = None,
 ) -> torch.Tensor:
@@ -574,6 +576,7 @@ def fused_recurrent_gated_delta_rule_update_fwd(
         cu_seqlens=cu_seqlens,
         scale=scale,
         intermediate_states_buffer=intermediate_states_buffer,
+        intermediate_state_indices=intermediate_state_indices,
         cache_steps=0 if cache_steps is None else cache_steps,
         retrieve_parent_token_ptr=retrieve_parent_token,
         stride_retrieve_parent_token_seq=stride_retrieve_parent_token_seq,
@@ -588,13 +591,13 @@ def fused_recurrent_gated_delta_rule_update_fwd(
         BK=BK,
         BV=BV,
         USE_INITIAL_STATE=initial_state_source is not None,
-        IS_BETA_HEADWISE=beta.ndim == v.ndim,
-        USE_QK_L2NORM_IN_KERNEL=use_qk_l2norm_in_kernel,
         IS_VARLEN=cu_seqlens is not None,
-        DISABLE_STATE_UPDATE=disable_state_update,
-        DISABLE_OUTPUT_CALCULATION=disable_output_calculation,
         CACHE_INTERMEDIATE_STATES=intermediate_states_buffer is not None,
         HAS_EAGLE_TREE_CUSTOM_ATTN_MASK=retrieve_parent_token is not None,
+        IS_BETA_HEADWISE=beta.ndim == v.ndim,
+        USE_QK_L2NORM_IN_KERNEL=use_qk_l2norm_in_kernel,
+        DISABLE_STATE_UPDATE=disable_state_update,
+        DISABLE_OUTPUT_CALCULATION=disable_output_calculation,
         num_warps=num_warps,
         num_stages=num_stages,
     )
@@ -621,6 +624,7 @@ class FusedRecurrentUpdateFunction(torch.autograd.Function):
         disable_state_update: bool = False,
         disable_output_calculation: bool = False,
         intermediate_states_buffer: Optional[torch.Tensor] = None,
+        intermediate_state_indices: Optional[torch.Tensor] = None,
         cache_steps: Optional[int] = None,
         retrieve_parent_token: Optional[torch.Tensor] = None,
     ):
@@ -638,6 +642,7 @@ class FusedRecurrentUpdateFunction(torch.autograd.Function):
             disable_state_update=disable_state_update,
             disable_output_calculation=disable_output_calculation,
             intermediate_states_buffer=intermediate_states_buffer,
+            intermediate_state_indices=intermediate_state_indices,
             cache_steps=cache_steps,
             retrieve_parent_token=retrieve_parent_token,
         )
@@ -668,6 +673,7 @@ def fused_recurrent_gated_delta_rule_update(
     disable_state_update: bool = False,
     disable_output_calculation: bool = False,
     intermediate_states_buffer: Optional[torch.Tensor] = None,
+    intermediate_state_indices: Optional[torch.Tensor] = None,
     cache_steps: Optional[int] = None,
     retrieve_parent_token: Optional[torch.Tensor] = None,
 ) -> torch.Tensor:
@@ -677,14 +683,17 @@ def fused_recurrent_gated_delta_rule_update(
                 f"The batch size is expected to be 1 rather than {q.shape[0]} when using `cu_seqlens`."
                 f"Please flatten variable-length inputs before processing."
             )
-        if (
+        if initial_state_source is not None:
-            initial_state_source is not None
+            if initial_state_indices.shape[0] != len(cu_seqlens) - 1:
-            and initial_state_indices.shape[0] != len(cu_seqlens) - 1
+                raise ValueError(
-        ):
+                    f"The number of initial states is expected to be equal to the number of input sequences, "
-            raise ValueError(
+                    f"i.e., {len(cu_seqlens) - 1} rather than {initial_state_indices.shape[0]}."
-                f"The number of initial states is expected to be equal to the number of input sequences, "
+                )
-                f"i.e., {len(cu_seqlens) - 1} rather than {initial_state_indices.shape[0]}."
+            if initial_state_indices.shape[0] != intermediate_state_indices.shape[0]:
-            )
+                raise ValueError(
+                    f"The number of intermediate state indices is expected to be equal to the number of input sequences, "
+                    f"i.e., {initial_state_indices.shape[0]} != {intermediate_state_indices.shape[0]}."
+                )
     if scale is None:
         scale = k.shape[-1] ** -0.5
     else:
@@ -705,6 +714,7 @@ def fused_recurrent_gated_delta_rule_update(
         disable_state_update,
         disable_output_calculation,
         intermediate_states_buffer,
+        intermediate_state_indices,
         cache_steps,
         retrieve_parent_token,
     )

python/sglang/srt/layers/attention/hybrid_linear_attn_backend.py

@@ -1,10 +1,13 @@
 from typing import Optional, Union
 
 import torch
+import triton
+import triton.language as tl
 from einops import rearrange
 
 from sglang.srt.layers.attention.base_attn_backend import AttentionBackend
 from sglang.srt.layers.attention.fla.chunk import chunk_gated_delta_rule
+from sglang.srt.layers.attention.fla.chunk_delta_h import CHUNK_SIZE as FLA_CHUNK_SIZE
 from sglang.srt.layers.attention.fla.fused_gdn_gating import fused_gdn_gating
 from sglang.srt.layers.attention.fla.fused_recurrent import (
     fused_recurrent_gated_delta_rule_update,
@@ -57,6 +60,108 @@ elif is_npu():
     causal_conv1d_update = causal_conv1d_update_npu
 
 
+# Kernel to track mamba states if needed based on track mask
+@triton.jit
+def track_mamba_state_if_needed_kernel(
+    conv_states_ptr,
+    ssm_states_ptr,
+    cache_indices_ptr,
+    mamba_track_mask_ptr,
+    mamba_track_indices_ptr,
+    conv_state_stride_0,  # stride for first dimension (batch/pool index)
+    ssm_state_stride_0,  # stride for first dimension (batch/pool index)
+    conv_state_numel_per_row: tl.constexpr,  # total elements per row
+    ssm_state_numel_per_row: tl.constexpr,  # total elements per row
+    BLOCK_SIZE: tl.constexpr,
+):
+    """
+    Track conv_states and ssm_states rows based on track mask.
+
+    This kernel replaces a Python loop that copies state tensors for mamba attention.
+    For each batch element, if the track mask is True, it copies the entire row from
+    the source index (cache_indices[i]) to the destination index (mamba_track_indices[i]).
+
+    Grid: (batch_size,)
+    Each block handles one batch element, using multiple threads to copy data in parallel.
+    """
+    batch_idx = tl.program_id(0)
+
+    # Load the copy mask for this batch element
+    track_mask = tl.load(mamba_track_mask_ptr + batch_idx)
+
+    # Early exit if we don't need to track
+    if not track_mask:
+        return
+
+    # Load source and destination indices
+    src_idx = tl.load(cache_indices_ptr + batch_idx)
+    dst_idx = tl.load(mamba_track_indices_ptr + batch_idx)
+
+    # Copy conv_states
+    # Each thread handles BLOCK_SIZE elements
+    for offset in range(0, conv_state_numel_per_row, BLOCK_SIZE):
+        element_indices = offset + tl.arange(0, BLOCK_SIZE)
+        mask = element_indices < conv_state_numel_per_row
+
+        src_ptr = conv_states_ptr + src_idx * conv_state_stride_0 + element_indices
+        dst_ptr = conv_states_ptr + dst_idx * conv_state_stride_0 + element_indices
+
+        data = tl.load(src_ptr, mask=mask, other=0.0)
+        tl.store(dst_ptr, data, mask=mask)
+
+    # Copy ssm_states
+    for offset in range(0, ssm_state_numel_per_row, BLOCK_SIZE):
+        element_indices = offset + tl.arange(0, BLOCK_SIZE)
+        mask = element_indices < ssm_state_numel_per_row
+
+        src_ptr = ssm_states_ptr + src_idx * ssm_state_stride_0 + element_indices
+        dst_ptr = ssm_states_ptr + dst_idx * ssm_state_stride_0 + element_indices
+
+        data = tl.load(src_ptr, mask=mask, other=0.0)
+        tl.store(dst_ptr, data, mask=mask)
+
+
+def track_mamba_states_if_needed(
+    conv_states: torch.Tensor,
+    ssm_states: torch.Tensor,
+    cache_indices: torch.Tensor,
+    mamba_track_mask: torch.Tensor,
+    mamba_track_indices: torch.Tensor,
+    batch_size: int,
+):
+    """
+    Track mamba states using Triton kernel for better performance.
+
+    Args:
+        conv_states: Convolution states tensor [pool_size, ...]
+        ssm_states: SSM states tensor [pool_size, ...]
+        cache_indices: Source indices for each batch element [batch_size]
+        mamba_track_mask: Boolean mask indicating which elements to track [batch_size]
+        mamba_track_indices: Indices to track for each batch element [batch_size]
+        batch_size: Number of batch elements
+    """
+    conv_state_numel_per_row = conv_states[0].numel()
+    ssm_state_numel_per_row = ssm_states[0].numel()
+
+    # Choose BLOCK_SIZE based on the size of the data
+    BLOCK_SIZE = 1024
+
+    # Launch kernel with batch_size blocks
+    grid = (batch_size,)
+    track_mamba_state_if_needed_kernel[grid](
+        conv_states,
+        ssm_states,
+        cache_indices,
+        mamba_track_mask,
+        mamba_track_indices,
+        conv_states.stride(0),
+        ssm_states.stride(0),
+        conv_state_numel_per_row,
+        ssm_state_numel_per_row,
+        BLOCK_SIZE,
+    )
+
+
 class MambaAttnBackendBase(AttentionBackend):
     def __init__(self, model_runner: ModelRunner):
         super().__init__()
@@ -71,6 +176,7 @@ class MambaAttnBackendBase(AttentionBackend):
         self.retrieve_parent_token_list = []
         self.cached_cuda_graph_decode_query_start_loc: torch.Tensor = None
         self.cached_cuda_graph_verify_query_start_loc: torch.Tensor = None
+        self.conv_states_shape: tuple[int, int] = None
 
     def _forward_metadata(self, forward_batch: ForwardBatch):
         bs = forward_batch.batch_size
@@ -78,6 +184,15 @@ class MambaAttnBackendBase(AttentionBackend):
         retrieve_next_token = None
         retrieve_next_sibling = None
         retrieve_parent_token = None
+        track_conv_indices = None
+        track_ssm_h_src = None
+        track_ssm_h_dst = None
+        track_ssm_final_src = None
+        track_ssm_final_dst = None
+
+        mamba_cache_indices = self.req_to_token_pool.get_mamba_indices(
+            forward_batch.req_pool_indices
+        )
 
         if forward_batch.forward_mode.is_decode_or_idle():
             query_start_loc = torch.arange(
@@ -108,22 +223,160 @@ class MambaAttnBackendBase(AttentionBackend):
                     forward_batch.extend_start_loc[-1]
                     + forward_batch.extend_seq_lens[-1]
                 )
+                if (
+                    forward_batch.mamba_track_mask is not None
+                    and forward_batch.mamba_track_mask.any()
+                ):
+                    track_conv_indices = self._init_track_conv_indices(
+                        query_start_loc, forward_batch
+                    )
+
+                    (
+                        track_ssm_h_src,
+                        track_ssm_h_dst,
+                        track_ssm_final_src,
+                        track_ssm_final_dst,
+                    ) = self._init_track_ssm_indices(mamba_cache_indices, forward_batch)
         else:
             raise ValueError(f"Invalid forward mode: {forward_batch.forward_mode=}")
-        mamba_cache_indices = self.req_to_token_pool.get_mamba_indices(
+
-            forward_batch.req_pool_indices
-        )
         return ForwardMetadata(
             query_start_loc=query_start_loc,
             mamba_cache_indices=mamba_cache_indices,
             retrieve_next_token=retrieve_next_token,
             retrieve_next_sibling=retrieve_next_sibling,
             retrieve_parent_token=retrieve_parent_token,
+            track_conv_indices=track_conv_indices,
+            track_ssm_h_src=track_ssm_h_src,
+            track_ssm_h_dst=track_ssm_h_dst,
+            track_ssm_final_src=track_ssm_final_src,
+            track_ssm_final_dst=track_ssm_final_dst,
         )
 
     def init_forward_metadata(self, forward_batch: ForwardBatch):
         self.forward_metadata = self._forward_metadata(forward_batch)
 
+    def _init_track_conv_indices(
+        self, query_start_loc: torch.Tensor, forward_batch: ForwardBatch
+    ):
+        """
+        Compute indices for extracting conv states from the input sequence during extend.
+
+        In Mamba models, the conv layer maintains a sliding window of recent inputs.
+        After processing a prefill chunk, we need to save the last `conv_state_len` tokens
+        of the processed region for prefix caching.
+
+        The key insight is that FLA (Flash Linear Attention) processes sequences in chunks
+        of FLA_CHUNK_SIZE. We only track the conv state up to the last complete chunk boundary
+        (aligned_len).
+
+        start_indices is the starting token index of the conv state to track in this extend batch.
+        indices include all pos to track in this extend batch, conv_state_len for each req that
+        needs to be tracked (i.e. mamba_track_mask is True)
+
+        Returns:
+            indices: Tensor of shape [num_tracked_requests, conv_state_len] containing
+                     flattened positions into the packed input tensor.
+        """
+        conv_state_len = self.conv_states_shape[-1]
+
+        # Calculate the end position of the last aligned chunk
+        lens_to_track = (
+            forward_batch.mamba_track_seqlens - forward_batch.extend_prefix_lens
+        )
+        aligned_len = (lens_to_track // FLA_CHUNK_SIZE) * FLA_CHUNK_SIZE
+        start_indices = query_start_loc[:-1] + aligned_len - conv_state_len
+        start_indices = start_indices[forward_batch.mamba_track_mask]
+
+        # Create indices: [batch_size, conv_state_len]
+        indices = start_indices.unsqueeze(-1) + torch.arange(
+            conv_state_len,
+            device=self.device,
+            dtype=start_indices.dtype,
+        )
+
+        return indices.clamp(0, query_start_loc[-1] - 1)
+
+    def _init_track_ssm_indices(
+        self, mamba_cache_indices: torch.Tensor, forward_batch: ForwardBatch
+    ):
+        """
+        Compute source and destination indices for tracking SSM states for prefix caching.
+
+        After processing a prefill, we need to save the SSM recurrent state for prefix caching.
+        The FLA kernel outputs intermediate hidden states `h` at each chunk boundary,
+        plus a `last_recurrent_state` at the end of the chunked prefill size.
+
+        The challenge is that sequences may or may not end on a chunk boundary:
+          - Aligned case (len % FLA_CHUNK_SIZE == 0): In this case, FLA will store the to-cache
+            state in the last_recurrent_state.
+          - Unaligned case (len % FLA_CHUNK_SIZE != 0): The last_recurrent_state includes the
+            unaligned position, but we only want state up to the last chunk boundary.
+            We must extract from the intermediate `h` tensor at the appropriate chunk index.
+
+        We compute the src and dst indices for all requests that need to be cached
+        (i.e. mamba_track_mask is True) based on the rule above.
+
+        For example:
+        1. If chunked prefill length is < 64, then only final state has value. In this case we
+           cache `final` state.
+        2. if chunked prefill length == 64, then only final state has value. In this case we
+           cache pos 64, from `final` state
+        3. if chunked prefill length >64 and < 128, then both h and final state have value.
+           We cache pos 64 from `h` state
+        4. if chunked prefill length ==128, then both h and final state have value. We cache
+           pos 128 from `final` state. Note `h` doesn't include the pos 128.
+
+        Returns:
+            track_ssm_h_src: Source indices into the packed `h` tensor (for unaligned seqs)
+            track_ssm_h_dst: Destination cache slot indices (for unaligned seqs)
+            track_ssm_final_src: Source indices into last_recurrent_state buffer (for aligned seqs)
+            track_ssm_final_dst: Destination cache slot indices (for aligned seqs)
+        """
+        # Move to CPU to avoid kernel launches for masking operations
+        mamba_track_mask = forward_batch.mamba_track_mask.cpu()
+        extend_seq_lens = forward_batch.extend_seq_lens.cpu()
+        mamba_track_indices = forward_batch.mamba_track_indices.cpu()
+        mamba_cache_indices = mamba_cache_indices.cpu()
+        mamba_track_seqlens = forward_batch.mamba_track_seqlens.cpu()
+        prefix_lens = forward_batch.extend_prefix_lens.cpu()
+
+        # Calculate the number of hidden states per request
+        num_h_states = (extend_seq_lens - 1) // FLA_CHUNK_SIZE + 1
+
+        # Calculate the starting offset for each sequence in the packed batch
+        track_ssm_src_offset = torch.zeros_like(num_h_states)
+        track_ssm_src_offset[1:] = torch.cumsum(num_h_states[:-1], dim=0)
+
+        # Filter variables by track mask
+        lens_to_track = mamba_track_seqlens - prefix_lens
+        lens_masked = lens_to_track[mamba_track_mask]
+        offset_masked = track_ssm_src_offset[mamba_track_mask]
+        dst_masked = mamba_track_indices[mamba_track_mask]
+
+        # Determine if the sequence ends at a chunk boundary
+        is_aligned = (lens_masked % FLA_CHUNK_SIZE) == 0
+
+        # Case 1: Aligned. Use last_recurrent_state from ssm_states.
+        track_ssm_final_src = mamba_cache_indices[mamba_track_mask][is_aligned]
+        track_ssm_final_dst = dst_masked[is_aligned]
+
+        # Case 2: Unaligned. Use intermediate state from h.
+        # TODO: if support FLA_CHUNK_SIZE % page size != 0, then need to modify this
+        not_aligned = ~is_aligned
+        track_ssm_h_src = offset_masked[not_aligned] + (
+            lens_masked[not_aligned] // FLA_CHUNK_SIZE
+        )
+        track_ssm_h_dst = dst_masked[not_aligned]
+
+        # Move back to GPU
+        return (
+            track_ssm_h_src.to(self.device, non_blocking=True),
+            track_ssm_h_dst.to(self.device, non_blocking=True),
+            track_ssm_final_src.to(self.device, non_blocking=True),
+            track_ssm_final_dst.to(self.device, non_blocking=True),
+        )
+
     def init_forward_metadata_capture_cuda_graph(
         self,
         bs: int,
@@ -165,7 +418,7 @@ class MambaAttnBackendBase(AttentionBackend):
                 )
             )
             self.query_start_loc_list.append(
-                torch.empty((i + 2,), dtype=torch.int32, device=self.device)
+                torch.zeros((i + 2,), dtype=torch.int32, device=self.device)
             )
             self.retrieve_next_token_list.append(
                 torch.zeros(
@@ -277,7 +530,6 @@ class MambaAttnBackendBase(AttentionBackend):
         # If topk > 1, we need to use retrieve_next_token and retrieve_next_sibling to handle the eagle tree custom attention mask
         if forward_mode.is_target_verify() and spec_info.topk > 1:
             bs_without_pad = spec_info.retrive_next_token.shape[0]
-            # print(spec_info.retrive_next_token, spec_info.retrive_next_sibling)
             self.retrieve_next_token_list[bs - 1][:bs_without_pad].copy_(
                 spec_info.retrive_next_token
             )
@@ -300,6 +552,70 @@ class MambaAttnBackendBase(AttentionBackend):
     def get_cuda_graph_seq_len_fill_value(self):
         return 1  # Mamba attn does not use seq lens to index kv cache
 
+    def _track_mamba_state_decode(
+        self,
+        forward_batch: ForwardBatch,
+        conv_states: torch.Tensor,
+        ssm_states: torch.Tensor,
+        cache_indices: torch.Tensor,
+    ):
+        """
+        Track and copy Mamba conv/SSM states during decode for prefix caching.
+
+        During decode, each token update modifies conv_states and ssm_states in-place
+        at positions indexed by cache_indices (the working slots). For prefix caching,
+        we need to copy these updated states to persistent cache slots (mamba_track_indices)
+        so they can be prefix cached.
+
+        This delegates to `track_mamba_states_if_needed`, which performs:
+            conv_states[mamba_track_indices[i]] = conv_states[cache_indices[i]]
+            ssm_states[mamba_track_indices[i]] = ssm_states[cache_indices[i]]
+        for all requests where mamba_track_mask[i] is True.
+        """
+        if forward_batch.mamba_track_mask is not None:
+            track_mamba_states_if_needed(
+                conv_states,
+                ssm_states,
+                cache_indices,
+                forward_batch.mamba_track_mask,
+                forward_batch.mamba_track_indices,
+                forward_batch.batch_size,
+            )
+
+    def _track_mamba_state_extend(
+        self,
+        forward_batch: ForwardBatch,
+        h: torch.Tensor,
+        ssm_states: torch.Tensor,
+        forward_metadata: ForwardMetadata,
+    ):
+        """
+        Track and copy SSM states during extend for prefix caching.
+
+        After the FLA chunked prefill kernel runs, we need to save the SSM recurrent
+        state at the last chunk boundary so it can be reused for prefix caching.
+        The source of the state depends on whether the sequence length is aligned
+        to FLA_CHUNK_SIZE. See `_init_track_ssm_indices` for more details on how
+        the source and destination indices are computed.
+
+        Note: Conv state tracking for extend is handled separately via gather operations
+        using indices computed by `_init_track_conv_indices`.
+        """
+        if (
+            forward_batch.mamba_track_mask is not None
+            and forward_batch.mamba_track_mask.any()
+        ):
+            h = h.squeeze(0)
+
+            if forward_metadata.track_ssm_h_src.numel() > 0:
+                ssm_states[forward_metadata.track_ssm_h_dst] = h[
+                    forward_metadata.track_ssm_h_src
+                ].to(ssm_states.dtype, copy=False)
+            if forward_metadata.track_ssm_final_src.numel() > 0:
+                ssm_states[forward_metadata.track_ssm_final_dst] = ssm_states[
+                    forward_metadata.track_ssm_final_src
+                ]
+
 
 class KimiLinearAttnBackend(MambaAttnBackendBase):
     """Attention backend using Mamba kernel."""
@@ -521,6 +837,15 @@ class KimiLinearAttnBackend(MambaAttnBackendBase):
 class GDNAttnBackend(MambaAttnBackendBase):
     """Attention backend using Mamba kernel."""
 
+    def __init__(self, model_runner: ModelRunner):
+        super().__init__(model_runner)
+        self.conv_states_shape = (
+            model_runner.req_to_token_pool.mamba_pool.mamba_cache.conv[0].shape
+        )
+        assert (
+            self.conv_states_shape[-1] < FLA_CHUNK_SIZE
+        ), f"{self.conv_states_shape[-1]=} should be less than {FLA_CHUNK_SIZE}"
+
     def forward_decode(
         self,
         q: torch.Tensor,
@@ -593,6 +918,10 @@ class GDNAttnBackend(MambaAttnBackendBase):
             softplus_threshold=20.0,
         )
 
+        self._track_mamba_state_decode(
+            forward_batch, conv_states, ssm_states, cache_indices
+        )
+
         return core_attn_out
 
     def forward_extend(
@@ -622,12 +951,13 @@ class GDNAttnBackend(MambaAttnBackendBase):
         seq_len = kwargs["seq_len"]
 
         is_target_verify = forward_batch.forward_mode.is_target_verify()
+        forward_metadata = self.forward_metadata
 
-        query_start_loc = self.forward_metadata.query_start_loc
+        query_start_loc = forward_metadata.query_start_loc
-        cache_indices = self.forward_metadata.mamba_cache_indices
+        cache_indices = forward_metadata.mamba_cache_indices
-        retrieve_next_token = self.forward_metadata.retrieve_next_token
+        retrieve_next_token = forward_metadata.retrieve_next_token
-        retrieve_next_sibling = self.forward_metadata.retrieve_next_sibling
+        retrieve_next_sibling = forward_metadata.retrieve_next_sibling
-        retrieve_parent_token = self.forward_metadata.retrieve_parent_token
+        retrieve_parent_token = forward_metadata.retrieve_parent_token
 
         mamba_cache_params = self.req_to_token_pool.mamba2_layer_cache(layer_id)
         conv_states = mamba_cache_params.conv[0]
@@ -643,6 +973,9 @@ class GDNAttnBackend(MambaAttnBackendBase):
                 dtype=torch.bool,
                 device=forward_batch.input_ids.device,
             )
+            intermediate_state_indices = torch.arange(
+                cache_indices.shape[0], dtype=torch.int32, device=cache_indices.device
+            )
         else:
             has_initial_states = forward_batch.extend_prefix_lens > 0
 
@@ -660,14 +993,30 @@ class GDNAttnBackend(MambaAttnBackendBase):
                 activation,
                 conv_state_indices=cache_indices[:batch_size],
                 intermediate_conv_window=intermediate_conv_window_cache,
+                intermediate_state_indices=intermediate_state_indices[:batch_size],
                 retrieve_next_token=retrieve_next_token,
                 retrieve_next_sibling=retrieve_next_sibling,
                 retrieve_parent_token=retrieve_parent_token,
             )
             mixed_qkv = mixed_qkv_processed.transpose(1, 2).view(seq_len, -1)
         else:
+            mixed_qkv = mixed_qkv.transpose(0, 1)
+            if (
+                forward_batch.mamba_track_mask is not None
+                and forward_batch.mamba_track_mask.any()
+            ):
+                conv_dst = forward_batch.mamba_track_indices
+                # Gather all slices at once: [:, track_conv_indices] -> [d, num_masked, slice_len]
+                # track_conv_indices is already filtered and clamped in _init_track_conv_indices
+                mixed_qkv_to_track = mixed_qkv[
+                    :, forward_metadata.track_conv_indices
+                ].transpose(0, 1)
+                # Apply mask and assign to destinations
+                mask_indices = forward_batch.mamba_track_mask.nonzero(as_tuple=True)[0]
+                conv_states[conv_dst[mask_indices]] = mixed_qkv_to_track
+
             mixed_qkv = causal_conv1d_fn(
-                mixed_qkv.transpose(0, 1),
+                mixed_qkv,
                 conv_weights,
                 bias,
                 activation=activation,
@@ -710,12 +1059,13 @@ class GDNAttnBackend(MambaAttnBackendBase):
                 use_qk_l2norm_in_kernel=True,
                 disable_state_update=True,
                 intermediate_states_buffer=intermediate_state_cache,
+                intermediate_state_indices=intermediate_state_indices,
                 cache_steps=forward_batch.spec_info.draft_token_num,
                 retrieve_parent_token=retrieve_parent_token,
             )
         else:
             recurrent_state = ssm_states[cache_indices]
-            core_attn_out, last_recurrent_state = chunk_gated_delta_rule(
+            core_attn_out, last_recurrent_state, h = chunk_gated_delta_rule(
                 q=query,
                 k=key,
                 v=value,
@@ -730,6 +1080,10 @@ class GDNAttnBackend(MambaAttnBackendBase):
             last_recurrent_state = last_recurrent_state.to(ssm_states.dtype, copy=False)
             ssm_states[cache_indices] = last_recurrent_state
 
+            self._track_mamba_state_extend(
+                forward_batch, h, ssm_states, forward_metadata
+            )
+
         return core_attn_out
 
 
@@ -965,14 +1319,23 @@ class HybridLinearAttnBackend(AttentionBackend):
                 **kwargs,
             )
 
-    def update_mamba_state_after_mtp_verify(self, accepted_indices, model):
+    def update_mamba_state_after_mtp_verify(
-        request_number = accepted_indices.shape[0]
+        self,
+        accepted_steps: torch.Tensor,
+        mamba_track_indices: Optional[torch.Tensor],
+        mamba_steps_to_track: Optional[torch.Tensor],
+        model,
+    ):
+        request_number = accepted_steps.shape[0]
 
         state_indices_tensor = (
             self.linear_attn_backend.forward_metadata.mamba_cache_indices[
                 :request_number
             ]
         )
+        intermediate_state_indices = torch.arange(
+            request_number, dtype=torch.int32, device=state_indices_tensor.device
+        )
 
         mamba_caches = (
             self.linear_attn_backend.req_to_token_pool.get_speculative_mamba2_params_all_layers()
@@ -983,19 +1346,41 @@ class HybridLinearAttnBackend(AttentionBackend):
         intermediate_state_cache = mamba_caches.intermediate_ssm
         intermediate_conv_window_cache = mamba_caches.intermediate_conv_window[0]
 
-        # SSM state updates (chunked to reduce peak memory)
-        valid_mask = accepted_indices >= 0
-
         # Compute common indices once to avoid duplication
-        valid_state_indices = state_indices_tensor[valid_mask].to(torch.int64)  # [N]
+        valid_mask = accepted_steps >= 0
-        last_steps = accepted_indices[valid_mask].to(torch.int64)  # [N]
+        dst_state_indices = state_indices_tensor[valid_mask].to(torch.int64)  # [N]
+        src_state_indices = intermediate_state_indices[valid_mask].to(
+            torch.int64
+        )  # [N]
+        last_steps = accepted_steps[valid_mask].to(torch.int64)  # [N]
 
         # scatter into ssm_states at the chosen cache lines
-        ssm_states[:, valid_state_indices, :] = intermediate_state_cache[
+        ssm_states[:, dst_state_indices, :] = intermediate_state_cache[
-            :, valid_state_indices, last_steps
+            :, src_state_indices, last_steps
         ].to(ssm_states.dtype, copy=False)
 
         # Scatter into conv_states at the chosen cache lines
-        conv_states[:, valid_state_indices, :, :] = intermediate_conv_window_cache[
+        conv_states[:, dst_state_indices, :] = intermediate_conv_window_cache[
-            :, valid_state_indices, last_steps
+            :, src_state_indices, last_steps
         ].to(conv_states.dtype, copy=False)
+
+        # Track indices used for tracking mamba states for prefix cache
+        if mamba_track_indices is not None:
+            assert mamba_steps_to_track is not None
+            track_mask = mamba_steps_to_track >= 0
+            track_steps = mamba_steps_to_track[track_mask].to(torch.int64)  # [N]
+            if track_steps.numel() == 0:
+                # No track indices to update
+                return
+            dst_track_indices = mamba_track_indices[track_mask].to(torch.int64)
+            src_track_indices = intermediate_state_indices[track_mask].to(torch.int64)
+
+            # scatter into ssm_states at the chosen track states
+            ssm_states[:, dst_track_indices, :] = intermediate_state_cache[
+                :, src_track_indices, track_steps
+            ].to(ssm_states.dtype, copy=False)
+
+            # scatter into conv_states at the chosen track states
+            conv_states[:, dst_track_indices, :] = intermediate_conv_window_cache[
+                :, src_track_indices, track_steps
+            ].to(conv_states.dtype, copy=False)

python/sglang/srt/layers/attention/mamba/causal_conv1d_triton.py

@@ -578,6 +578,7 @@ def _causal_conv1d_update_kernel(
     conv_state_indices_ptr,
     num_accepted_tokens_ptr,
     intermediate_conv_window_ptr,
+    intermediate_state_indices_ptr,
     retrieve_next_token_ptr,
     retrieve_next_sibling_ptr,
     retrieve_parent_token_ptr,
@@ -602,6 +603,7 @@ def _causal_conv1d_update_kernel(
     stride_inter_step: tl.constexpr,
     stride_inter_dim: tl.constexpr,
     stride_inter_win: tl.constexpr,
+    stride_intermediate_state_indices: tl.constexpr,
     stride_retrieve_next_token_seq: tl.constexpr,
     stride_retrieve_next_token_token: tl.constexpr,
     stride_retrieve_next_sibling_seq: tl.constexpr,
@@ -639,6 +641,11 @@ def _causal_conv1d_update_kernel(
         conv_state_batch_coord = tl.load(
             conv_state_indices_ptr + idx_seq * stride_state_indices
         ).to(tl.int64)
+        if SAVE_INTERMEDIATE:
+            intermediate_state_batch_coord = tl.load(
+                intermediate_state_indices_ptr
+                + idx_seq * stride_intermediate_state_indices
+            ).to(tl.int64)
     else:
         conv_state_batch_coord = idx_seq
     if USE_PAD_SLOT:  # noqa
@@ -847,7 +854,7 @@ def _causal_conv1d_update_kernel(
                     # Layout: [seq(cache line), step, dim, win(K-1)]
                     base_ptr = (
                         intermediate_conv_window_ptr
-                        + conv_state_batch_coord * stride_inter_seq
+                        + intermediate_state_batch_coord * stride_inter_seq
                         + idx_token * stride_inter_step
                         + idx_feats * stride_inter_dim
                     )
@@ -934,7 +941,7 @@ def _causal_conv1d_update_kernel(
                 # Layout: [seq(cache line), step, dim, win(K-1)]
                 base_ptr = (
                     intermediate_conv_window_ptr
-                    + conv_state_batch_coord * stride_inter_seq
+                    + intermediate_state_batch_coord * stride_inter_seq
                     + idx_token * stride_inter_step
                     + idx_feats * stride_inter_dim
                 )
@@ -980,6 +987,7 @@ def causal_conv1d_update(
     conv_state_indices: Optional[torch.Tensor] = None,
     num_accepted_tokens: Optional[torch.Tensor] = None,
     intermediate_conv_window: Optional[torch.Tensor] = None,
+    intermediate_state_indices: Optional[torch.Tensor] = None,
     retrieve_next_token: Optional[torch.Tensor] = None,
     retrieve_next_sibling: Optional[torch.Tensor] = None,
     retrieve_parent_token: Optional[torch.Tensor] = None,
@@ -1040,6 +1048,8 @@ def causal_conv1d_update(
             assert conv_state.size(0) >= batch
         else:
             assert (batch,) == conv_state_indices.shape
+            assert intermediate_state_indices is not None
+            assert (batch,) == intermediate_state_indices.shape
 
         assert num_cache_lines >= batch
         assert weight.stride(1) == 1  # Need this
@@ -1056,6 +1066,11 @@ def causal_conv1d_update(
     stride_state_indices = (
         conv_state_indices.stride(0) if conv_state_indices is not None else 0
     )
+    stride_intermediate_state_indices = (
+        intermediate_state_indices.stride(0)
+        if intermediate_state_indices is not None
+        else 0
+    )
     if num_accepted_tokens is not None:
         state_len = width - 1 + (seqlen - 1)  # effective state_len needed
     else:
@@ -1117,6 +1132,7 @@ def causal_conv1d_update(
         conv_state_indices,
         num_accepted_tokens,
         intermediate_conv_window if intermediate_conv_window is not None else x,
+        intermediate_state_indices,
         retrieve_next_token,
         retrieve_next_sibling,
         retrieve_parent_token,
@@ -1141,6 +1157,7 @@ def causal_conv1d_update(
         stride_inter_step,
         stride_inter_dim,
         stride_inter_win,
+        stride_intermediate_state_indices,
         stride_retrieve_next_token_seq,
         stride_retrieve_next_token_token,
         stride_retrieve_next_sibling_seq,

python/sglang/srt/layers/attention/mamba/mamba2_metadata.py

@@ -27,9 +27,17 @@ from sglang.srt.model_executor.forward_batch_info import ForwardBatch
 class ForwardMetadata:
     query_start_loc: torch.Tensor
     mamba_cache_indices: torch.Tensor
+    # For topk > 1 eagle
     retrieve_next_token: Optional[torch.Tensor] = None
     retrieve_next_sibling: Optional[torch.Tensor] = None
     retrieve_parent_token: Optional[torch.Tensor] = None
+    # For prefill radix cache
+    track_conv_indices: Optional[torch.Tensor] = None
+    track_ssm_h_src: Optional[torch.Tensor] = None
+    track_ssm_h_dst: Optional[torch.Tensor] = None
+    track_ssm_final_src: Optional[torch.Tensor] = None
+    track_ssm_final_dst: Optional[torch.Tensor] = None
+
     is_target_verify: bool = False
     draft_token_num: int = 1
 

python/sglang/srt/managers/schedule_batch.py

@@ -57,6 +57,7 @@ from sglang.srt.disaggregation.decode_schedule_batch_mixin import (
 from sglang.srt.disaggregation.utils import DisaggregationMode
 from sglang.srt.distributed.parallel_state import get_tensor_model_parallel_rank
 from sglang.srt.environ import envs
+from sglang.srt.layers.attention.fla.chunk_delta_h import CHUNK_SIZE as FLA_CHUNK_SIZE
 from sglang.srt.mem_cache.allocator import (
     BaseTokenToKVPoolAllocator,
     SWATokenToKVPoolAllocator,
@@ -543,6 +544,14 @@ class Req:
         # Memory pool info
         self.req_pool_idx: Optional[int] = None
         self.mamba_pool_idx: Optional[torch.Tensor] = None  # shape (1)
+        self.mamba_ping_pong_track_buffer: Optional[torch.Tensor] = None  # shape (2)
+        self.mamba_next_track_idx: Optional[int] = None  # 0 or 1
+        self.mamba_last_track_seqlen: Optional[int] = (
+            None  # seq len of the last cached mamba state
+        )
+        # the branching point seqlen to track mamba state. If set, given by prefix match,
+        # it will be the tracked seqlen in the ping pong buffer for the right prefill pass.
+        self.mamba_branching_seqlen: Optional[int] = None
 
         # Check finish
         self.tokenizer = None
@@ -824,11 +833,13 @@ class Req:
                 self.last_node,
                 self.last_host_node,
                 self.host_hit_length,
+                self.mamba_branching_seqlen,
             ) = (
                 match_result.device_indices,
                 match_result.last_device_node,
                 match_result.last_host_node,
                 match_result.host_hit_length,
+                match_result.mamba_branching_seqlen,
             )
             self.cache_protected_len = len(self.prefix_indices)
 
@@ -1027,6 +1038,10 @@ class Req:
         self.extend_logprob_start_len = 0
         self.is_chunked = 0
         self.mamba_pool_idx = None
+        self.mamba_ping_pong_track_buffer = None
+        self.mamba_next_track_idx = None
+        self.mamba_last_track_seqlen = None
+        self.mamba_branching_seqlen = None
         self.already_computed = 0
         self.kv_allocated_len = 0
         self.kv_committed_len = 0
@@ -1115,6 +1130,11 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
     out_cache_loc: torch.Tensor = None  # shape: [b], int64
     output_ids: torch.Tensor = None  # shape: [b], int64
 
+    # For hybrid GDN prefix cache
+    mamba_track_indices: torch.Tensor = None  # shape: [b], int64
+    mamba_track_mask: torch.Tensor = None  # shape: [b], bool
+    mamba_track_seqlens: torch.Tensor = None  # shape: [b], int64
+
     # For multimodal inputs
     multimodal_inputs: Optional[List] = None
 
@@ -1380,6 +1400,9 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
         input_embeds = []
         extend_input_logprob_token_ids = []
         multimodal_inputs = []
+        mamba_track_mask_cpu = []
+        mamba_track_indices_cpu = []
+        mamba_track_seqlens_cpu = []
 
         for i, (req, seq_len, pre_len) in enumerate(zip(reqs, seq_lens, prefix_lens)):
             req.req_pool_idx = req_pool_indices[i]
@@ -1403,6 +1426,14 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
                 req.already_computed = seq_len
             req.is_retracted = False
 
+            if get_global_server_args().enable_mamba_extra_buffer():
+                self._mamba_radix_cache_v2_req_prepare_for_extend(
+                    req,
+                    mamba_track_mask_cpu,
+                    mamba_track_indices_cpu,
+                    mamba_track_seqlens_cpu,
+                )
+
             # Compute the relative logprob_start_len in an extend batch
             #
             # Key variables:
@@ -1512,6 +1543,23 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
         self.extend_logprob_start_lens = [r.extend_logprob_start_len for r in reqs]
         self.extend_input_logprob_token_ids = extend_input_logprob_token_ids
 
+        if get_global_server_args().enable_mamba_extra_buffer():
+            self.mamba_track_indices = torch.tensor(
+                mamba_track_indices_cpu,
+                dtype=torch.int64,
+                device=self.device,
+            )
+            self.mamba_track_mask = torch.tensor(
+                mamba_track_mask_cpu,
+                dtype=torch.bool,
+                device=self.device,
+            )
+            self.mamba_track_seqlens = torch.tensor(
+                mamba_track_seqlens_cpu,
+                dtype=torch.int64,
+                device=self.device,
+            )
+
         if self.model_config.is_encoder_decoder:
             self.prepare_encoder_info_extend(input_ids, seq_lens)
 
@@ -1521,6 +1569,60 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
             self.model_config.vocab_size,
         )
 
+    def _mamba_radix_cache_v2_req_prepare_for_extend(
+        self,
+        req: Req,
+        mamba_track_mask_cpu: List[bool],
+        mamba_track_indices_cpu: List[int],
+        mamba_track_seqlens_cpu: List[int],
+    ):
+        mask = (req.extend_input_len // FLA_CHUNK_SIZE) * FLA_CHUNK_SIZE > 0
+        mamba_track_mask_cpu.append(mask)
+        mamba_track_indices_cpu.append(
+            req.mamba_ping_pong_track_buffer[req.mamba_next_track_idx].item()
+        )
+        mamba_track_seqlen = -1
+        if mask:
+            # mamba_track_seqlen is used to calculate the indices to track in
+            # hybrid_linear_attn_backend's _init_track_ssm_indices. Due to the
+            # fact that the ssm state between aligned and non-aligned are retrieved differently,
+            # if 1) last pos and 2) is aligned, then retrieved from the last_recurrent_state,
+            # otherwise retrieved from h (i.e. unaligned).
+            # We need to pass the non-aligned seqlen to the calculation. Even though
+            # we pass in mamba_track_seqlen, the actual tracked seqlen is mamba_last_track_seqlen.
+            mamba_track_seqlen = len(req.prefix_indices) + req.extend_input_len
+            # mamba_last_track_seqlen is actual tracked seqlen. Used to pass to
+            # mamba radix cache to track which seqlen this mamba state should store at.
+            mamba_track_seqlen_aligned = (
+                len(req.prefix_indices)
+                + (req.extend_input_len // FLA_CHUNK_SIZE) * FLA_CHUNK_SIZE
+            )
+            req.mamba_next_track_idx = (
+                self.req_to_token_pool.get_mamba_ping_pong_other_idx(
+                    req.mamba_next_track_idx
+                )
+            )
+            if req.mamba_branching_seqlen is not None:
+                # track branching point in this forward if the branching point
+                # is within the current extend batch.
+                branching_seqlen_aligned_mask = (
+                    req.mamba_branching_seqlen - len(req.prefix_indices)
+                ) % FLA_CHUNK_SIZE == 0
+                if (
+                    req.mamba_branching_seqlen > len(req.prefix_indices)
+                    and req.mamba_branching_seqlen < mamba_track_seqlen
+                    and branching_seqlen_aligned_mask
+                ):
+                    # NOTE: See the comment above for mamba_track_seqlen, the +1 is necessary
+                    # because the branching point is not the last aligned position, so we need
+                    # to retrieve its state from h. Adding 1 will give us the correct index in h,
+                    # otherwise the calculation will retrieve the state from the last_recurrent_state,
+                    # which is not correct.
+                    mamba_track_seqlen = req.mamba_branching_seqlen + 1
+                    mamba_track_seqlen_aligned = req.mamba_branching_seqlen
+            req.mamba_last_track_seqlen = mamba_track_seqlen_aligned
+        mamba_track_seqlens_cpu.append(mamba_track_seqlen)
+
     def prepare_for_split_prefill(self):
         self.prepare_for_extend()
         # For split prefill, we need to set the forward mode to SPLIT_PREFILL
@@ -1786,6 +1888,24 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
             self.orig_seq_lens.add_(1)
         self.seq_lens_sum += bs
 
+        if get_global_server_args().enable_mamba_extra_buffer():
+            self.mamba_track_indices = torch.tensor(
+                [
+                    req.mamba_ping_pong_track_buffer[req.mamba_next_track_idx]
+                    for req in self.reqs
+                ],
+                dtype=torch.int64,
+                device=self.device,
+            )
+            self.mamba_track_mask = torch.tensor(
+                [
+                    sl % get_global_server_args().mamba_track_interval == 0
+                    for sl in self.seq_lens_cpu
+                ],
+                dtype=torch.bool,
+                device=self.device,
+            )
+
     def maybe_wait_verify_done(self):
         if self.is_v2_eagle:
             draft_input: EagleDraftInput = self.spec_info
@@ -1842,6 +1962,9 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
         self.out_cache_loc = None
         self.seq_lens_sum = self.seq_lens.sum().item()
         self.output_ids = self.output_ids[keep_indices_device]
+        self.mamba_track_indices = None
+        self.mamba_track_mask = None
+        self.mamba_track_seqlens = None
         self.return_logprob = any(req.return_logprob for req in self.reqs)
         if self.return_logprob:
             self.top_logprobs_nums = [self.top_logprobs_nums[i] for i in keep_indices]
@@ -1889,6 +2012,9 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
         self.seq_lens_sum += other.seq_lens_sum
         if self.output_ids is not None:
             self.output_ids = torch.cat([self.output_ids, other.output_ids])
+        self.mamba_track_indices = None
+        self.mamba_track_mask = None
+        self.mamba_track_seqlens = None
         if self.return_logprob and other.return_logprob:
             self.top_logprobs_nums.extend(other.top_logprobs_nums)
             self.token_ids_logprobs.extend(other.token_ids_logprobs)
@@ -1982,6 +2108,9 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
             dllm_config=self.dllm_config,
             reqs=self.reqs,
             has_grammar=self.has_grammar,
+            mamba_track_indices=self.mamba_track_indices,
+            mamba_track_mask=self.mamba_track_mask,
+            mamba_track_seqlens=self.mamba_track_seqlens,
         )
 
     def copy(self):
@@ -2003,6 +2132,9 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
             is_prefill_only=self.is_prefill_only,
             seq_lens_cpu=self.seq_lens_cpu,
             enable_overlap=self.enable_overlap,
+            mamba_track_indices=self.mamba_track_indices,
+            mamba_track_mask=self.mamba_track_mask,
+            mamba_track_seqlens=self.mamba_track_seqlens,
         )
 
     def _is_available_size_sufficient(self, num_tokens: int) -> bool:
@@ -2104,3 +2236,8 @@ class ModelWorkerBatch:
     # FIXME(lsyin): remove this after fully overlap grammar
     reqs: Optional[List[Req]] = None
     has_grammar: bool = False
+
+    # For mamba state tracking
+    mamba_track_indices: Optional[torch.Tensor] = None  # shape: [b], int64
+    mamba_track_mask: Optional[torch.Tensor] = None  # shape: [b], bool
+    mamba_track_seqlens: Optional[torch.Tensor] = None  # shape: [b], int64

python/sglang/srt/managers/schedule_policy.py

@@ -363,7 +363,7 @@ class PrefillAdder:
         self.is_hybrid_swa = isinstance(
             self.token_to_kv_pool_allocator, SWATokenToKVPoolAllocator
         )
-        self.is_ssm_radix_cache = isinstance(self.tree_cache, MambaRadixCache)
+        self.is_hybrid_ssm_cache = isinstance(self.tree_cache, MambaRadixCache)
 
         self.priority_scheduling_preemption_threshold = (
             priority_scheduling_preemption_threshold
@@ -389,7 +389,7 @@ class PrefillAdder:
                 self.token_to_kv_pool_allocator.swa_available_size()
                 + self.tree_cache.swa_evictable_size(),
             )
-        elif self.is_ssm_radix_cache:
+        elif self.is_hybrid_ssm_cache:
             available_and_evictable = (
                 self.token_to_kv_pool_allocator.available_size()
                 + self.tree_cache.full_evictable_size()
@@ -411,7 +411,7 @@ class PrefillAdder:
                 self.token_to_kv_pool_allocator.swa_available_size()
                 + self.tree_cache.swa_evictable_size(),
             )
-        elif self.is_ssm_radix_cache:
+        elif self.is_hybrid_ssm_cache:
             available_and_evictable = (
                 self.token_to_kv_pool_allocator.available_size()
                 + self.tree_cache.full_evictable_size()

python/sglang/srt/managers/scheduler.py

@@ -405,7 +405,7 @@ class Scheduler(
 
         # Hybrid memory pool
         self.is_hybrid_swa = self.tp_worker.is_hybrid_swa
-        self.is_ssm_model = (
+        self.is_hybrid_ssm = (
             self.tp_worker.model_runner.hybrid_gdn_config is not None
             or self.tp_worker.model_runner.mamba2_config is not None
         )
@@ -772,6 +772,7 @@ class Scheduler(
             eviction_policy=server_args.radix_eviction_policy,
             enable_metrics=self.enable_metrics,
             enable_kv_cache_events=self.enable_kv_cache_events,
+            enable_mamba_extra_buffer=server_args.enable_mamba_extra_buffer(),
         )
 
         if (
@@ -808,7 +809,7 @@ class Scheduler(
                 self.tree_cache = SWARadixCache(
                     params=params, sliding_window_size=self.sliding_window_size
                 )
-            elif self.is_ssm_model:
+            elif self.is_hybrid_ssm:
                 from sglang.srt.mem_cache.mamba_radix_cache import MambaRadixCache
 
                 self.tree_cache = MambaRadixCache(params)

python/sglang/srt/managers/scheduler_metrics_mixin.py

@@ -112,7 +112,7 @@ class SchedulerMetricsMixin:
                 f"full token usage: {full_token_usage:.2f}, "
                 f"swa token usage: {swa_token_usage:.2f}, "
             )
-        elif self.is_ssm_model:
+        elif self.is_hybrid_ssm:
             (
                 full_num_used,
                 _,
@@ -166,7 +166,7 @@ class SchedulerMetricsMixin:
             self.stats.token_usage = token_usage
             if self.is_hybrid_swa:
                 self.stats.swa_token_usage = swa_token_usage
-            if self.is_ssm_model:
+            if self.is_hybrid_ssm:
                 self.stats.mamba_usage = mamba_usage
             self.stats.num_queue_reqs = len(self.waiting_queue)
             self.stats.num_grammar_queue_reqs = len(self.grammar_queue)
@@ -238,7 +238,7 @@ class SchedulerMetricsMixin:
                 f"#swa token: {swa_num_used}, "
                 f"swa token usage: {swa_token_usage:.2f}, "
             )
-        elif self.is_ssm_model:
+        elif self.is_hybrid_ssm:
             (
                 full_num_used,
                 mamba_used,
@@ -315,7 +315,7 @@ class SchedulerMetricsMixin:
             self.stats.token_usage = token_usage
             if self.is_hybrid_swa:
                 self.stats.swa_token_usage = swa_token_usage
-            if self.is_ssm_model:
+            if self.is_hybrid_ssm:
                 self.stats.mamba_usage = mamba_usage
             self.stats.decode_sum_seq_lens = batch.seq_lens_cpu.sum().item()
             self.stats.gen_throughput = self.last_gen_throughput
@@ -402,7 +402,7 @@ class SchedulerMetricsMixin:
         if self.is_hybrid_swa:
             full_num_used, swa_num_used, *_ = self._get_swa_token_info()
             num_tokens = max(full_num_used, swa_num_used)
-        elif self.is_ssm_model:
+        elif self.is_hybrid_ssm:
             num_tokens = self._get_mamba_token_info()[0]
         else:
             num_tokens = self._get_token_info()[0]

python/sglang/srt/managers/scheduler_output_processor_mixin.py

@@ -21,6 +21,7 @@ from sglang.srt.managers.schedule_batch import (
     ScheduleBatch,
 )
 from sglang.srt.mem_cache.common import release_kv_cache
+from sglang.srt.server_args import get_global_server_args
 from sglang.srt.tracing.trace import trace_slice, trace_slice_batch, trace_slice_end
 
 if TYPE_CHECKING:
@@ -267,6 +268,7 @@ class SchedulerOutputProcessorMixin:
         next_token_ids = result.next_token_ids.tolist()
         accept_lens = result.accept_lens.tolist()
         result.num_accepted_tokens = sum(accept_lens) - len(batch.reqs)
+        result.accept_length_per_req_cpu = [x - 1 for x in accept_lens]
 
         predict_tokens = []
         stride = self.draft_worker.speculative_num_draft_tokens
@@ -359,6 +361,9 @@ class SchedulerOutputProcessorMixin:
                 req.output_ids.extend(next_token_id)
                 new_accepted_len = len(next_token_id)
 
+            # Update Mamba last track seqlen
+            self._mamba_prefix_cache_update(req, batch, result, i)
+
             req.check_finished(new_accepted_len)
 
             if req.finished():
@@ -424,6 +429,31 @@ class SchedulerOutputProcessorMixin:
         ):
             self.log_decode_stats(can_run_cuda_graph, running_batch=batch)
 
+    def _mamba_prefix_cache_update(
+        self, req: Req, batch: ScheduleBatch, result: GenerationBatchResult, i: int
+    ) -> None:
+        seq_len = len(req.origin_input_ids) + len(req.output_ids) - 1
+        if req.mamba_ping_pong_track_buffer is not None:
+            mamba_track_interval = get_global_server_args().mamba_track_interval
+            if batch.spec_algorithm.is_none() and seq_len % mamba_track_interval == 0:
+                # for non-spec decode, we update mamba_last_track_seqlen at the end of each track interval
+                req.mamba_next_track_idx = 1 - req.mamba_next_track_idx
+                req.mamba_last_track_seqlen = seq_len
+            elif (
+                not batch.spec_algorithm.is_none()
+                and result.accept_length_per_req_cpu is not None
+            ):
+                # for spec decode, update mamba_last_track_seqlen if this iteration crosses a track interval
+                actual_seq_len = req.seqlen - 1
+                if (
+                    actual_seq_len // mamba_track_interval
+                    != (actual_seq_len - result.accept_length_per_req_cpu[i])
+                    // mamba_track_interval
+                ):
+                    req.mamba_last_track_seqlen = (
+                        actual_seq_len // mamba_track_interval * mamba_track_interval
+                    )
+
     def _process_input_token_logprobs(
         self, req: Req, input_token_logprobs: List
     ) -> None:

python/sglang/srt/managers/scheduler_runtime_checker_mixin.py

@@ -121,9 +121,22 @@ class SchedulerRuntimeCheckerMixin:
             full_num_used != self.tree_cache.full_protected_size()
             or mamba_num_used != self.tree_cache.mamba_protected_size()
         )
+        free_full_pages = set(
+            self.token_to_kv_pool_allocator.free_pages.tolist()
+            + self.token_to_kv_pool_allocator.release_pages.tolist()
+        )
+        cached_full_pages = set(self.tree_cache.all_values_flatten().tolist())
+        expected_full_pages = set(range(1, self.token_to_kv_pool_allocator.size + 1))
+        leaked_full_pages = expected_full_pages - free_full_pages - cached_full_pages
+        free_mamba_pages = set(self.req_to_token_pool.mamba_pool.free_slots.tolist())
+        cached_mamba_pages = set(self.tree_cache.all_mamba_values_flatten().tolist())
+        expected_mamba_pages = set(range(self.req_to_token_pool.mamba_pool.size))
+        leaked_mamba_pages = (
+            expected_mamba_pages - free_mamba_pages - cached_mamba_pages
+        )
         token_msg = (
             f"{full_available_size=}, {full_evictable_size=}, {self.token_to_kv_pool_allocator.size=}, {self.tree_cache.full_protected_size()=}\n"
-            f"{mamba_available_size=}, {mamba_evictable_size=}, {self.req_to_token_pool.mamba_pool.size=}, {self.tree_cache.mamba_protected_size()=}\n"
+            f"{mamba_available_size=}, {mamba_evictable_size=}, {self.req_to_token_pool.mamba_pool.size=}, {self.tree_cache.mamba_protected_size()=}, leaked_full_pages={leaked_full_pages if len(leaked_full_pages) > 0 else None}, leaked_mamba_pages={leaked_mamba_pages if len(leaked_mamba_pages) > 0 else None}\n"
         )
         return memory_leak, token_msg
 
@@ -207,7 +220,7 @@ class SchedulerRuntimeCheckerMixin:
     def check_memory(self: Scheduler):
         if self.is_hybrid_swa:
             memory_leak, token_msg = self._check_hybrid_memory()
-        elif self.is_ssm_model and isinstance(self.tree_cache, MambaRadixCache):
+        elif self.is_hybrid_ssm and isinstance(self.tree_cache, MambaRadixCache):
             memory_leak, token_msg = self._check_mamba_memory()
         else:
             memory_leak, token_msg = self._check_radix_cache_memory()
@@ -242,7 +255,7 @@ class SchedulerRuntimeCheckerMixin:
                 ) = self._get_swa_token_info()
                 num_used = max(full_num_used, swa_num_used)
                 token_usage = max(full_token_usage, swa_token_usage)
-            elif self.is_ssm_model:
+            elif self.is_hybrid_ssm:
                 (
                     num_used,
                     _,
@@ -281,7 +294,7 @@ class SchedulerRuntimeCheckerMixin:
 
     def check_tree_cache(self: Scheduler):
         if (self.is_hybrid_swa and isinstance(self.tree_cache, SWARadixCache)) or (
-            self.is_ssm_model and isinstance(self.tree_cache, MambaRadixCache)
+            self.is_hybrid_ssm and isinstance(self.tree_cache, MambaRadixCache)
         ):
             self.tree_cache.sanity_check()
 
@@ -344,7 +357,7 @@ class SchedulerWatchdog:
             # Print batch size and memory pool info to check whether there are de-sync issues.
             if self.scheduler.is_hybrid_swa:
                 _, info_msg = self.scheduler._check_hybrid_memory()
-            elif self.scheduler.is_ssm_model and isinstance(
+            elif self.scheduler.is_hybrid_ssm and isinstance(
                 self.scheduler.tree_cache, MambaRadixCache
             ):
                 _, info_msg = self.scheduler._check_mamba_memory()

python/sglang/srt/managers/utils.py

@@ -24,7 +24,8 @@ class GenerationBatchResult:
     logits_output: Optional[LogitsProcessorOutput] = None
     pp_hidden_states_proxy_tensors: Optional[PPProxyTensors] = None
     next_token_ids: Optional[torch.Tensor] = None
-    num_accepted_tokens: Optional[int] = None
+    num_accepted_tokens: int = 0
+    accept_length_per_req_cpu: Optional[List[int]] = None
     can_run_cuda_graph: bool = False
 
     # For output processing

python/sglang/srt/mem_cache/cache_init_params.py

@@ -24,3 +24,5 @@ class CacheInitParams:
 
     enable_metrics: bool = False
     enable_kv_cache_events: bool = False
+
+    enable_mamba_extra_buffer: bool = False

python/sglang/srt/mem_cache/common.py

@@ -19,6 +19,10 @@ from sglang.srt.utils.common import ceil_align
 if TYPE_CHECKING:
     from sglang.srt.managers.schedule_batch import Req, ScheduleBatch
 
+# Needs 2 + 1 slots for mamba request with prefix cache. 2 for ping pong cache, 1 for running mamba state.
+MAMBA_STATE_PER_REQ_PREFIX_CACHE = 3
+MAMBA_STATE_PER_REQ_NO_CACHE = 1
+
 logger = logging.getLogger(__name__)
 
 
@@ -300,9 +304,15 @@ def alloc_req_slots(
     """Allocate request slots from the pool."""
     if isinstance(req_to_token_pool, HybridReqToTokenPool):
         mamba_available_size = req_to_token_pool.mamba_pool.available_size()
-        if mamba_available_size < num_reqs:
+        factor = (
+            MAMBA_STATE_PER_REQ_PREFIX_CACHE
+            if isinstance(tree_cache, MambaRadixCache)
+            else MAMBA_STATE_PER_REQ_NO_CACHE
+        )
+        mamba_state_needed = num_reqs * factor
+        if mamba_available_size < mamba_state_needed:
             if tree_cache is not None and isinstance(tree_cache, MambaRadixCache):
-                mamba_num = max(0, num_reqs - mamba_available_size)
+                mamba_num = max(0, mamba_state_needed - mamba_available_size)
                 tree_cache.evict_mamba(mamba_num)
         req_pool_indices = req_to_token_pool.alloc(num_reqs, reqs)
     else:

python/sglang/srt/mem_cache/mamba_radix_cache.py

@@ -21,16 +21,24 @@ The radix tree data structure for managing the hybrid (full and Mamba) KV cache.
 
 import heapq
 from collections import defaultdict
+from functools import partial
 from typing import TYPE_CHECKING, List, Optional, Tuple
 
 import torch
 from numpy import float64
 
-from sglang.srt.mem_cache.allocator import TokenToKVPoolAllocator
+from sglang.srt.distributed import get_tensor_model_parallel_rank
+from sglang.srt.layers.attention.fla.chunk_delta_h import CHUNK_SIZE as FLA_CHUNK_SIZE
+from sglang.srt.mem_cache.allocator import (
+    PagedTokenToKVPoolAllocator,
+    TokenToKVPoolAllocator,
+)
 from sglang.srt.mem_cache.base_prefix_cache import BasePrefixCache, MatchResult
+from sglang.srt.mem_cache.memory_pool import HybridReqToTokenPool
 from sglang.srt.mem_cache.radix_cache import (
     RadixKey,
     _key_match_page_size1,
+    _key_match_paged,
     get_child_key,
 )
 
@@ -252,6 +260,30 @@ class LRUList:
             return False
         return node.id in self.cache
 
+    def pretty_print(self, tree_cache: Optional["MambaRadixCache"] = None):
+        """
+        Pretty print the lru list
+        """
+        msg = f"{self.mamba=} LRU list: "
+        x_lru = self._get_lru()
+        while x_lru is not None and x_lru.id in self.cache:
+            msg += f"[{x_lru.id}] {x_lru.last_access_time:f} -> "
+            x_lru = getattr(x_lru, self.prv)
+        print(msg)
+
+        if not tree_cache:
+            return
+        msg = f"{self.mamba=} Nodes (sorted by last_access_time): "
+        if self.mamba:
+            nodes = tree_cache._collect_nontombstone_nodes()
+        else:
+            nodes = tree_cache._collect_all_nodes()
+        heapq.heapify(nodes)
+        while len(nodes):
+            x = heapq.heappop(nodes)
+            msg += f"[{x.id}] {x.last_access_time:f} -> "
+        print(msg)
+
     # Note: this is expensive, only use for debug
     def sanity_check_evictable_size(self):
         """
@@ -292,9 +324,13 @@ class LRUList:
                 if x == tree_cache.root_node:
                     # root node is not in the lru list
                     continue
+                assert (
+                    x_lru is not None and x_lru.id in self.cache
+                ), f"Incorrect LRU list, x_lru is None or not in cache: {x_lru=}, {x.id=}"
+
                 assert (
                     x == x_lru
-                ), f"Incorrect LRU list, {self.mamba=}, x: {x.id=} != x_lru: {x_lru.id=}"
+                ), f"Incorrect LRU list, {self.mamba=}, x: {x.id=} != x_lru: {x_lru.id=}, {x.last_access_time=}, {x_lru.last_access_time=}"
                 assert (
                     x_lru.full_lock_ref == 0
                 ), f"x_lru should not be locked when idle, {x_lru.full_lock_ref=}, {x_lru.id=}"
@@ -314,22 +350,33 @@ class LRUList:
                 evictable_size == lru_list_evictable_size
             ), f"{self.mamba=}, total nodes: {total_nodes}, total lru: {total_lru}, evictable size: {evictable_size} != lru list evictable size: {lru_list_evictable_size}"
         except Exception as e:
-            msg = f"Mamba Radix tree sanity check failed, ping @yizhang2077: {e}"
+            if get_tensor_model_parallel_rank() == 0:
-            logger.error(msg)
+                msg = f"Mamba Radix tree sanity check failed, ping @yizhang2077: {e}"
-            raise Exception(msg)
+                logger.error(msg)
+                tree_cache.pretty_print()
+                tree_cache.full_lru_list.pretty_print(tree_cache)
+                tree_cache.mamba_lru_list.pretty_print(tree_cache)
+                raise Exception(msg)
 
 
 class MambaRadixCache(BasePrefixCache):
     def __init__(self, params: CacheInitParams):
-        assert isinstance(params.token_to_kv_pool_allocator, TokenToKVPoolAllocator)
+        assert isinstance(
-        self.req_to_token_pool = params.req_to_token_pool
+            params.token_to_kv_pool_allocator, TokenToKVPoolAllocator
+        ) or isinstance(params.token_to_kv_pool_allocator, PagedTokenToKVPoolAllocator)
+        self.req_to_token_pool: HybridReqToTokenPool = params.req_to_token_pool
         self.token_to_kv_pool_allocator = params.token_to_kv_pool_allocator
 
-        assert (
-            params.page_size == 1
-        ), "Only support page_size=1 in mamba radix cache now."
         self.page_size = params.page_size
         self.disable = params.disable
+        self.enable_mamba_extra_buffer = params.enable_mamba_extra_buffer
+
+        if not self.enable_mamba_extra_buffer:
+            assert (
+                self.page_size == 1
+            ), f"Page size must be 1 for MambaRadixCache v1, got {self.page_size}"
+        else:
+            logger.info(f"Mamba extra_buffer is enabled.")
 
         if self.token_to_kv_pool_allocator:
             self.device = self.token_to_kv_pool_allocator.device
@@ -339,15 +386,19 @@ class MambaRadixCache(BasePrefixCache):
         if params.enable_metrics:
             self.init_metrics_collector()
 
-        self.key_match_fn = _key_match_page_size1
+        if self.page_size == 1:
-        self.get_child_key_fn = get_child_key
+            self.key_match_fn = _key_match_page_size1
+            self.get_child_key_fn = get_child_key
+        else:
+            self.key_match_fn = partial(_key_match_paged, page_size=self.page_size)
+            self.get_child_key_fn = partial(get_child_key, page_size=self.page_size)
         self.reset()
 
     ##### Public API #####
 
     def reset(self) -> None:
         self.root_node = TreeNode()
-        self.root_node.key = []
+        self.root_node.key = RadixKey([], None)
         self.root_node.value = []
         self.root_node.full_lock_ref = 1
         self.root_node.mamba_lock_ref = 1
@@ -384,7 +435,7 @@ class MambaRadixCache(BasePrefixCache):
                 last_host_node=self.root_node,
             )
 
-        value, last_node = self._match_prefix_helper(key)
+        value, last_node, mamba_branching_seqlen = self._match_prefix_helper(key)
 
         # copy mamba state to req local space if cow is true
         if cow_mamba and last_node.mamba_value is not None:
@@ -415,18 +466,26 @@ class MambaRadixCache(BasePrefixCache):
             device_indices=value,
             last_device_node=last_node,
             last_host_node=last_node,
+            mamba_branching_seqlen=mamba_branching_seqlen,
         )
 
     def insert(self, key: RadixKey, value=None, mamba_value=None) -> Tuple[int, bool]:
         if self.disable:
-            return 0
+            return 0, False
 
         if value is None:
             value = torch.tensor([x for x in key.token_ids], dtype=torch.int64)
         return self._insert_helper(self.root_node, key, value, mamba_value)
 
-    def cache_finished_req(self, req: Req, is_insert: bool = True):
+    def cache_finished_req(self, req: Req, is_insert: bool = True) -> None:
         """Cache request when it finishes."""
+        # for abort with prefix cache hit and before alloc is called
+        if req.req_pool_idx is None:
+            if req.mamba_pool_idx is not None:
+                self.req_to_token_pool.mamba_pool.free(req.mamba_pool_idx.unsqueeze(-1))
+                req.mamba_pool_idx = None
+            return
+
         kv_committed_len = req.pop_committed_kv_cache()
 
         if self.disable:
@@ -442,56 +501,135 @@ class MambaRadixCache(BasePrefixCache):
             req.req_pool_idx, :kv_committed_len
         ]
 
-        page_aligned_len = len(kv_indices)
-        page_aligned_kv_indices = kv_indices.to(dtype=torch.int64, copy=True)
-
-        # Radix Cache takes one ref in memory pool
-        # insert the token_ids and kv_indices into the radix tree
-        # Note: the insert function already frees the overlapped kv_indices
-        mamba_value = req.mamba_pool_idx.unsqueeze(-1).clone()
-
         if is_insert:
+            cache_len = (
+                req.mamba_last_track_seqlen
+                if self.enable_mamba_extra_buffer
+                else len(token_ids)
+            )
+            if cache_len is None:
+                cache_len = 0
+            if cache_len != len(token_ids):
+                cache_end_idx = max(cache_len, req.cache_protected_len)
+                self.token_to_kv_pool_allocator.free(kv_indices[cache_end_idx:])
+                token_ids = token_ids[:cache_len]
+                kv_indices = kv_indices[:cache_len]
+
+            if self.page_size != 1:
+                page_aligned_len = len(kv_indices) // self.page_size * self.page_size
+                page_aligned_kv_indices = kv_indices[:page_aligned_len].to(
+                    dtype=torch.int64, copy=True
+                )
+            else:
+                page_aligned_len = len(kv_indices)
+                page_aligned_kv_indices = kv_indices.to(dtype=torch.int64, copy=True)
+
+            assert (
+                cache_len == page_aligned_len
+            ), f"It is required {cache_len=}, {page_aligned_len=}, {kv_committed_len=}, {len(req.origin_input_ids)=}, {len(req.output_ids)=} ping @yizhang2077 if you see this"
+
+            # Radix Cache takes one ref in memory pool
+            # insert the token_ids and kv_indices into the radix tree
+            if self.enable_mamba_extra_buffer:
+                mamba_ping_pong_track_buffer_to_keep = (
+                    self.req_to_token_pool.get_mamba_ping_pong_other_idx(
+                        req.mamba_next_track_idx
+                    )
+                )
+                mamba_value = (
+                    req.mamba_ping_pong_track_buffer[
+                        mamba_ping_pong_track_buffer_to_keep
+                    ]
+                    .unsqueeze(-1)
+                    .clone()
+                )
+            else:
+                mamba_value = req.mamba_pool_idx.unsqueeze(-1).clone()
+                mamba_ping_pong_track_buffer_to_keep = None
+
             new_prefix_len, mamba_exist = self.insert(
                 RadixKey(token_ids[:page_aligned_len], req.extra_key),
                 page_aligned_kv_indices,
                 mamba_value,
             )
+
             self.token_to_kv_pool_allocator.free(
-                kv_indices[len(req.prefix_indices) : new_prefix_len]
+                kv_indices[req.cache_protected_len : new_prefix_len]
             )
         else:
-            self.token_to_kv_pool_allocator.free(
+            self.token_to_kv_pool_allocator.free(kv_indices[req.cache_protected_len :])
-                kv_indices[len(req.prefix_indices) : page_aligned_len]
-            )
             mamba_exist = True
 
-        if req.req_pool_idx is not None:
+        if mamba_exist:
-            self.req_to_token_pool.free(req.req_pool_idx, free_mamba_cache=mamba_exist)
+            mamba_ping_pong_track_buffer_to_keep = None
-            self.dec_lock_ref(req.last_node)
+
-        else:  # for abort case
+        free_mamba_cache = True if self.enable_mamba_extra_buffer else mamba_exist
-            self.req_to_token_pool.mamba_pool.free(mamba_value)
+
+        self.req_to_token_pool.free(
+            req.req_pool_idx,
+            free_mamba_cache=free_mamba_cache,
+            mamba_ping_pong_track_buffer_to_keep=mamba_ping_pong_track_buffer_to_keep,
+        )
+
+        self.dec_lock_ref(req.last_node)
 
     def cache_unfinished_req(self, req: Req, chunked=False) -> None:
         """Cache request when it is unfinished."""
-        if self.disable:
+
+        def _skip_cache_unfinished_req(req: Req) -> None:
             kv_indices = self.req_to_token_pool.req_to_token[
                 req.req_pool_idx, : len(req.fill_ids)
             ]
+
             # `req.prefix_indices` will be used in `PrefillAdder::add_chunked_req` later
-            req.prefix_indices = kv_indices
+            req.prefix_indices = kv_indices.to(dtype=torch.int64, copy=True)
             return
 
         token_ids = req.fill_ids
-        kv_indices = self.req_to_token_pool.req_to_token[
+        cache_len = (
+            req.mamba_last_track_seqlen
+            if self.enable_mamba_extra_buffer
+            else len(token_ids)
+        )
+        if self.disable or cache_len is None:
+            return _skip_cache_unfinished_req(req)
+
+        kv_indices_orig = self.req_to_token_pool.req_to_token[
             req.req_pool_idx, : len(token_ids)
         ]
-        page_aligned_len = len(kv_indices)
+        # kv_indices is the kv indices to be cached
-        page_aligned_kv_indices = kv_indices.to(dtype=torch.int64, copy=True)
+        kv_indices = kv_indices_orig[:cache_len]
+        if self.page_size != 1:
+            page_aligned_len = len(kv_indices) // self.page_size * self.page_size
+            page_aligned_kv_indices = kv_indices[:page_aligned_len].to(
+                dtype=torch.int64, copy=True
+            )
+        else:
+            page_aligned_len = len(kv_indices)
+            page_aligned_kv_indices = kv_indices.to(dtype=torch.int64, copy=True)
+
+        assert page_aligned_len == len(
+            kv_indices
+        ), f"page_aligned_len != len(kv_indices), {page_aligned_len=}, {len(kv_indices)=}, {cache_len=}, {self.page_size=}, {FLA_CHUNK_SIZE=}"
+
         page_aligned_token_ids = token_ids[:page_aligned_len]
 
-        mamba_value = self.req_to_token_pool.get_mamba_indices(
+        if self.enable_mamba_extra_buffer:
-            req.req_pool_idx
+            # copy from the ping pong track buffer
-        ).unsqueeze(-1)
+            mamba_ping_pong_track_buffer_to_keep = (
+                self.req_to_token_pool.get_mamba_ping_pong_other_idx(
+                    req.mamba_next_track_idx
+                )
+            )
+            mamba_value = (
+                req.mamba_ping_pong_track_buffer[mamba_ping_pong_track_buffer_to_keep]
+                .unsqueeze(-1)
+                .clone()
+            )
+        else:
+            mamba_value = self.req_to_token_pool.get_mamba_indices(
+                req.req_pool_idx
+            ).unsqueeze(-1)
         # radix tree mamba value is forked from req space
         mamba_value_forked = self.req_to_token_pool.mamba_pool.fork_from(mamba_value)
 
@@ -508,7 +646,7 @@ class MambaRadixCache(BasePrefixCache):
             mamba_value_forked,
         )
         self.token_to_kv_pool_allocator.free(
-            kv_indices[len(req.prefix_indices) : new_prefix_len]
+            kv_indices[req.cache_protected_len : new_prefix_len]
         )
         # there is a mamba cache in radix cache, release it
         if mamba_exist:
@@ -526,21 +664,28 @@ class MambaRadixCache(BasePrefixCache):
         if not mamba_exist:
             assert torch.equal(new_last_node.mamba_value, mamba_value_forked)
 
-        assert len(req.prefix_indices) <= len(
+        assert (
+            req.cache_protected_len <= len(new_indices) + self.page_size - 1
+        ), f"{req.cache_protected_len=}, {len(new_indices)=}, {len(page_aligned_token_ids)=}, {mamba_exist=}"
+        assert new_prefix_len <= len(
             new_indices
-        ), f"{req.prefix_indices=}, {new_indices=}"
+        ), f"{new_prefix_len=}, {len(new_indices)=}"
-        assert new_prefix_len <= len(new_indices), f"{new_prefix_len=}, {new_indices=}"
 
         self.req_to_token_pool.write(
-            (req.req_pool_idx, slice(len(req.prefix_indices), len(new_indices))),
+            (req.req_pool_idx, slice(req.cache_protected_len, len(new_indices))),
-            new_indices[len(req.prefix_indices) :],
+            new_indices[req.cache_protected_len :],
         )
 
         self.dec_lock_ref(req.last_node)
         self.inc_lock_ref(new_last_node)
 
         # `req.prefix_indices` will be used in `PrefillAdder::add_chunked_req` later
-        req.prefix_indices = new_indices
+        # NOTE: this is needed for both page_size == 1 and page_size > 1
+        req.prefix_indices = torch.cat(
+            [new_indices, kv_indices_orig[len(new_indices) :]]
+        )
+        req.cache_protected_len = len(new_indices)
+        req.mamba_last_track_seqlen = None
         req.last_node = new_last_node
 
     def pretty_print(self) -> None:
@@ -670,7 +815,7 @@ class MambaRadixCache(BasePrefixCache):
         It unlocks the mamba_lock_ref for current node if its mamba_value exists.
         """
         if self.disable:
-            return
+            return None
 
         if node.mamba_value is not None:
             assert (
@@ -692,6 +837,8 @@ class MambaRadixCache(BasePrefixCache):
             node = node.parent
 
     def sanity_check(self):
+        if self.disable:
+            return
         self.full_lru_list.sanity_check(self)
         self.mamba_lru_list.sanity_check(self)
 
@@ -734,13 +881,25 @@ class MambaRadixCache(BasePrefixCache):
                 _dfs_helper(child)
 
         _dfs_helper(self.root_node)
-        return torch.cat(values)
+        return torch.cat(values) if len(values) > 0 else torch.tensor([])
+
+    def all_mamba_values_flatten(self) -> torch.Tensor:
+        values = []
+
+        def _dfs_helper(node: TreeNode):
+            if node.mamba_value is not None:
+                values.append(node.mamba_value)
+            for _, child in node.children.items():
+                _dfs_helper(child)
+
+        _dfs_helper(self.root_node)
+        return torch.cat(values) if len(values) > 0 else torch.tensor([])
 
     ##### Internal Helper Functions #####
 
     def _match_prefix_helper(
         self, key: RadixKey
-    ) -> Tuple[List[torch.Tensor], TreeNode]:
+    ) -> Tuple[List[torch.Tensor], TreeNode, Optional[int]]:
         """
         Mamba prefix matching helper. It factors in the sliding window size such that
         the matched node is guaranteed to either 1. connected to root without mamba tombstone,
@@ -750,7 +909,7 @@ class MambaRadixCache(BasePrefixCache):
         node = self.root_node
         child_key = self.get_child_key_fn(key)
 
-        value = []
+        value: List[torch.Tensor] = []
         best_value_len = 0
         best_last_node = node
         while len(key) > 0 and child_key in node.children.keys():
@@ -793,7 +952,19 @@ class MambaRadixCache(BasePrefixCache):
             )
             node_update = node_update.parent
 
-        return value[:best_value_len], best_last_node
+        # Calculate the branching point. It is defined as the last aligned position that
+        # does not have a mamba value.
+        if len(value) > best_value_len:
+            fla_chunk_aligned_seqlen = (
+                sum(len(v) for v in value) // FLA_CHUNK_SIZE
+            ) * FLA_CHUNK_SIZE
+            mamba_branching_seqlen = (
+                fla_chunk_aligned_seqlen if fla_chunk_aligned_seqlen > 0 else None
+            )
+        else:
+            mamba_branching_seqlen = None
+
+        return value[:best_value_len], best_last_node, mamba_branching_seqlen
 
     def _split_node(self, key: RadixKey, child: TreeNode, split_len: int) -> TreeNode:
         # new_node -> child

python/sglang/srt/mem_cache/memory_pool.py

@@ -152,6 +152,7 @@ class MambaPool:
         self,
         *,
         size: int,
+        spec_state_size: int,
         cache_params: BaseLinearStateParams,
         device: str,
         enable_memory_saver: bool = False,
@@ -198,7 +199,7 @@ class MambaPool:
                 intermediate_ssm_state_cache = torch.zeros(
                     size=(
                         num_mamba_layers,
-                        size + 1,
+                        spec_state_size + 1,
                         speculative_num_draft_tokens,
                         temporal_state_shape[0],
                         temporal_state_shape[1],
@@ -213,7 +214,7 @@ class MambaPool:
                     torch.zeros(
                         size=(
                             num_mamba_layers,
-                            size + 1,
+                            spec_state_size + 1,
                             speculative_num_draft_tokens,
                             conv_shape[0],
                             conv_shape[1],
@@ -267,6 +268,10 @@ class MambaPool:
 
         select_index = self.free_slots[:need_size]
         self.free_slots = self.free_slots[need_size:]
+        # clear at alloc time
+        for i in range(len(self.mamba_cache.conv)):
+            self.mamba_cache.conv[i][:, select_index] = 0
+        self.mamba_cache.temporal[:, select_index] = 0
 
         return select_index
 
@@ -274,9 +279,6 @@ class MambaPool:
         if free_index.numel() == 0:
             return
         self.free_slots = torch.cat((self.free_slots, free_index))
-        for i in range(len(self.mamba_cache.conv)):
-            self.mamba_cache.conv[i][:, free_index] = 0
-        self.mamba_cache.temporal[:, free_index] = 0
 
     def clear(self):
         # Zero the entire mamba cache before resetting free_slots
@@ -333,10 +335,12 @@ class HybridReqToTokenPool(ReqToTokenPool):
         *,
         size: int,
         mamba_size: int,
+        mamba_spec_state_size: int,
         max_context_len: int,
         device: str,
         enable_memory_saver: bool,
         cache_params: BaseLinearStateParams,
+        enable_mamba_extra_buffer: bool,
         speculative_num_draft_tokens: int = None,
     ):
         super().__init__(
@@ -345,23 +349,32 @@ class HybridReqToTokenPool(ReqToTokenPool):
             device=device,
             enable_memory_saver=enable_memory_saver,
         )
+        self.mamba_ping_pong_track_buffer_size = (
+            2 if speculative_num_draft_tokens is None else 1
+        )
+        self.enable_mamba_extra_buffer = enable_mamba_extra_buffer
         self.enable_memory_saver = enable_memory_saver
         self._init_mamba_pool(
             size=mamba_size,
+            mamba_spec_state_size=mamba_spec_state_size,
             cache_params=cache_params,
             device=device,
+            enable_mamba_extra_buffer=enable_mamba_extra_buffer,
             speculative_num_draft_tokens=speculative_num_draft_tokens,
         )
 
     def _init_mamba_pool(
         self,
         size: int,
+        mamba_spec_state_size: int,
         cache_params: BaseLinearStateParams,
         device: str,
+        enable_mamba_extra_buffer: bool,
         speculative_num_draft_tokens: int = None,
     ):
         self.mamba_pool = MambaPool(
             size=size,
+            spec_state_size=mamba_spec_state_size,
             cache_params=cache_params,
             device=device,
             enable_memory_saver=self.enable_memory_saver,
@@ -373,32 +386,67 @@ class HybridReqToTokenPool(ReqToTokenPool):
         self.req_index_to_mamba_index_mapping: torch.Tensor = torch.zeros(
             size, dtype=torch.int32, device=self.device
         )
+        if enable_mamba_extra_buffer:
+            self.req_index_to_mamba_ping_pong_track_buffer_mapping: torch.Tensor = (
+                torch.zeros(
+                    (size, self.mamba_ping_pong_track_buffer_size),
+                    dtype=torch.int32,
+                    device=self.device,
+                )
+            )
 
     # For chunk prefill req, we do not need to allocate mamba cache,
     # We could use allocated mamba cache instead.
-    def alloc(
+    def alloc(self, need_size: int, reqs: Optional[List["Req"]]) -> Optional[List[int]]:
-        self, need_size: int, reqs: Optional[List[Req]] = None
+        assert reqs is not None
-    ) -> Optional[List[int]]:
         select_index = super().alloc(need_size)
         if select_index == None:
             return None
 
         mamba_index = []
+        mamba_ping_pong_track_buffer_list = []
         for req in reqs:
             mid = None
             if req.mamba_pool_idx is not None:  # for radix cache
                 mid = req.mamba_pool_idx
             else:
-                mid = self.mamba_pool.alloc(1)[0]
+                mid = self.mamba_pool.alloc(1)
+                assert (
+                    mid is not None
+                ), f"Not enough space for mamba cache, try to increase --mamba-full-memory-ratio or --max-mamba-cache-size. {mid=}, {self.mamba_pool.size=}, {self.mamba_pool.available_size()=}, {len(reqs)=}"
+                mid = mid[0]
                 req.mamba_pool_idx = mid
-            if mid is not None:
+            mamba_index.append(mid)
-                mamba_index.append(mid)
+            if self.enable_mamba_extra_buffer:
+                if req.mamba_ping_pong_track_buffer is None:
+                    req.mamba_ping_pong_track_buffer = self.mamba_pool.alloc(
+                        self.mamba_ping_pong_track_buffer_size
+                    )
+                    assert (
+                        req.mamba_ping_pong_track_buffer is not None
+                    ), "Not enough space for mamba ping pong idx, try to increase --mamba-full-memory-ratio."
+                    req.mamba_next_track_idx = 0
+                mamba_ping_pong_track_buffer_list.append(
+                    req.mamba_ping_pong_track_buffer.tolist()
+                )
         assert len(select_index) == len(
             mamba_index
-        ), f"Not enough space for mamba cache, try to increase --max-mamba-cache-size."
+        ), f"Not enough space for mamba cache, try to increase --mamba-full-memory-ratio or --max-mamba-cache-size."
+        if self.enable_mamba_extra_buffer:
+            assert len(select_index) == len(
+                mamba_ping_pong_track_buffer_list
+            ), f"Not enough space for mamba ping pong idx, try to increase --mamba-full-memory-ratio."
         self.req_index_to_mamba_index_mapping[select_index] = torch.tensor(
             mamba_index, dtype=torch.int32, device=self.device
         )
+        if self.enable_mamba_extra_buffer:
+            self.req_index_to_mamba_ping_pong_track_buffer_mapping[select_index] = (
+                torch.tensor(
+                    mamba_ping_pong_track_buffer_list,
+                    dtype=torch.int32,
+                    device=self.device,
+                )
+            )
         return select_index
 
     def get_mamba_indices(self, req_indices: torch.Tensor) -> torch.Tensor:
@@ -411,8 +459,19 @@ class HybridReqToTokenPool(ReqToTokenPool):
     def get_speculative_mamba2_params_all_layers(self) -> MambaPool.SpeculativeState:
         return self.mamba_pool.get_speculative_mamba2_params_all_layers()
 
+    def get_mamba_ping_pong_other_idx(self, mamba_next_track_idx: int) -> int:
+        if self.mamba_ping_pong_track_buffer_size == 2:
+            return 1 - mamba_next_track_idx
+        else:
+            return mamba_next_track_idx
+
     # For chunk prefill, we can not free mamba cache, we need use it in the future
-    def free(self, free_index: Union[int, List[int]], free_mamba_cache: bool = True):
+    def free(
+        self,
+        free_index: Union[int, List[int]],
+        free_mamba_cache: bool = True,
+        mamba_ping_pong_track_buffer_to_keep: Optional[int] = None,
+    ):
         if isinstance(free_index, (int,)):
             free_index = [free_index]
         super().free(free_index)
@@ -420,9 +479,31 @@ class HybridReqToTokenPool(ReqToTokenPool):
             mamba_index = self.req_index_to_mamba_index_mapping[free_index]
             self.mamba_pool.free(mamba_index)
 
+            if self.enable_mamba_extra_buffer:
+                mamba_ping_pong_track_buffer_to_free = (
+                    self.req_index_to_mamba_ping_pong_track_buffer_mapping[
+                        free_index
+                    ].squeeze(0)
+                )
+                if mamba_ping_pong_track_buffer_to_keep is not None:
+                    assert mamba_ping_pong_track_buffer_to_keep in [
+                        0,
+                        1,
+                    ], f"mamba_ping_pong_track_buffer_to_keep must be 0 or 1, {mamba_ping_pong_track_buffer_to_keep=}"
+                    idx_to_free = list(range(self.mamba_ping_pong_track_buffer_size))
+                    idx_to_free.remove(mamba_ping_pong_track_buffer_to_keep)
+                    mamba_ping_pong_track_buffer_to_free = (
+                        mamba_ping_pong_track_buffer_to_free[idx_to_free]
+                    )
+                self.mamba_pool.free(mamba_ping_pong_track_buffer_to_free)
+
     def clear(self):
+        logger.info("Reset HybridReqToTokenPool")
         super().clear()
         self.mamba_pool.clear()
+        self.req_index_to_mamba_index_mapping.zero_()
+        if self.enable_mamba_extra_buffer:
+            self.req_index_to_mamba_ping_pong_track_buffer_mapping.zero_()
 
 
 class KVCache(abc.ABC):
@@ -1133,6 +1214,9 @@ class HybridLinearKVPool(KVCache):
                     cache_v,
                 )
 
+    def move_kv_cache(self, tgt_loc: torch.Tensor, src_loc: torch.Tensor):
+        self.full_kv_pool.move_kv_cache(tgt_loc, src_loc)
+
     def get_v_head_dim(self):
         return self.full_kv_pool.get_value_buffer(0).shape[-1]
 

python/sglang/srt/model_executor/cuda_graph_runner.py

@@ -321,6 +321,11 @@ class CudaGraphRunner:
                 num_tokens_per_bs=self.num_tokens_per_bs,
             )
 
+        enable_mamba_track = (
+            self.model_runner.server_args.enable_mamba_extra_buffer()
+            and self.model_runner.spec_algorithm.is_none()
+        )
+
         if self.require_gathered_buffer:
             assert self.require_mlp_tp_gather or self.require_attn_tp_gather
         self.buffers: GraphInputBuffers = GraphInputBuffers.create(
@@ -338,6 +343,7 @@ class CudaGraphRunner:
             encoder_len_fill_value=self.encoder_len_fill_value,
             num_tokens_per_bs=self.num_tokens_per_bs,
             cache_loc_dtype=self._cache_loc_dtype(),
+            enable_mamba_track=enable_mamba_track,
         )
 
         self.tbo_plugin = TboCudaGraphRunnerPlugin()
@@ -537,7 +543,7 @@ class CudaGraphRunner:
     def capture_one_batch_size(
         self, bs: int, forward: Callable, stream_idx: Optional[int] = None
     ):
-        buffers = self.buffers
+        buffers: GraphInputBuffers = self.buffers
         graph = self._create_device_graph()
         stream = self.stream
         num_tokens = bs * self.num_tokens_per_bs
@@ -611,6 +617,18 @@ class CudaGraphRunner:
         else:
             lora_ids = None
 
+        # mamba state tracking
+        mamba_track_indices = (
+            buffers.mamba_track_indices[:bs]
+            if buffers.mamba_track_indices is not None
+            else None
+        )
+        mamba_track_mask = (
+            buffers.mamba_track_mask[:bs]
+            if buffers.mamba_track_mask is not None
+            else None
+        )
+
         if stream_idx is None:
             attn_backend = self.model_runner.attn_backend
         else:
@@ -631,6 +649,9 @@ class CudaGraphRunner:
             attn_backend=attn_backend,
             out_cache_loc=out_cache_loc,
             seq_lens_sum=seq_lens.sum().item(),
+            mamba_track_indices=mamba_track_indices,
+            mamba_track_mask=mamba_track_mask,
+            mamba_track_seqlens=None,  # Prefill only
             encoder_lens=encoder_lens,
             return_logprob=False,
             positions=positions,

python/sglang/srt/model_executor/forward_batch_info.py

@@ -249,6 +249,12 @@ class ForwardBatch:
     # The indices of output tokens in the token_to_kv_pool_swa
     # TODO(shiyang, biao): integrate out_cache_loc_swa into multiple attention backends
     out_cache_loc_swa: Optional[torch.Tensor] = None
+    # The indices to track mamba state with
+    mamba_track_indices: Optional[torch.Tensor] = None  # shape: [b], int64
+    # The mask to track mamba state if needed
+    mamba_track_mask: Optional[torch.Tensor] = None  # shape: [b], bool
+    # The seqlens to track mamba state if masked, prefill only.
+    mamba_track_seqlens: Optional[torch.Tensor] = None  # shape: [b], int64
 
     # Optional seq_lens on cpu
     seq_lens_cpu: Optional[torch.Tensor] = None
@@ -398,6 +404,9 @@ class ForwardBatch:
             req_pool_indices=batch.req_pool_indices,
             seq_lens=batch.seq_lens,
             out_cache_loc=batch.out_cache_loc,
+            mamba_track_indices=batch.mamba_track_indices,
+            mamba_track_mask=batch.mamba_track_mask,
+            mamba_track_seqlens=batch.mamba_track_seqlens,
             mm_inputs=batch.multimodal_inputs,
             encoder_cached=batch.encoder_cached,
             encoder_lens=batch.encoder_lens,
@@ -881,6 +890,16 @@ class ForwardBatch:
         if self.encoder_lens is not None:
             self.encoder_lens = self._pad_tensor_to_size(self.encoder_lens, bs)
         self.positions = self._pad_tensor_to_size(self.positions, num_tokens)
+        if self.mamba_track_indices is not None:
+            self.mamba_track_indices = self._pad_tensor_to_size(
+                self.mamba_track_indices, bs
+            )
+        if self.mamba_track_mask is not None:
+            self.mamba_track_mask = self._pad_tensor_to_size(self.mamba_track_mask, bs)
+        if self.mamba_track_seqlens is not None:
+            self.mamba_track_seqlens = self._pad_tensor_to_size(
+                self.mamba_track_seqlens, bs
+            )
 
         if self.mrope_positions is not None:
             self.mrope_positions = self._pad_tensor_to_size(self.mrope_positions, bs)

python/sglang/srt/model_executor/input_buffers.py

@@ -25,6 +25,8 @@ class GraphInputBuffers:
     num_token_non_padded: torch.Tensor
     custom_mask: torch.Tensor
     next_token_logits_buffer: torch.Tensor
+    mamba_track_indices: Optional[torch.Tensor]
+    mamba_track_mask: Optional[torch.Tensor]
     global_num_tokens_gpu: torch.Tensor
     global_num_tokens_for_logprob_gpu: torch.Tensor
     encoder_lens: Optional[torch.Tensor]
@@ -48,6 +50,7 @@ class GraphInputBuffers:
         encoder_len_fill_value: int,
         num_tokens_per_bs: int,
         cache_loc_dtype: torch.dtype,
+        enable_mamba_track: bool,
     ) -> "GraphInputBuffers":
         with torch.device(device):
             input_ids = torch.zeros((max_num_token,), dtype=torch.int64)
@@ -66,6 +69,14 @@ class GraphInputBuffers:
                 (max_num_token, vocab_size),
                 dtype=torch.float,
             )
+            mamba_track_indices = (
+                torch.zeros((max_bs,), dtype=torch.int64)
+                if enable_mamba_track
+                else None
+            )
+            mamba_track_mask = (
+                torch.zeros((max_bs,), dtype=torch.bool) if enable_mamba_track else None
+            )
 
             if pp_size > 1:
                 pp_proxy_tensors = {
@@ -111,6 +122,8 @@ class GraphInputBuffers:
             num_token_non_padded=num_token_non_padded,
             custom_mask=custom_mask,
             next_token_logits_buffer=next_token_logits_buffer,
+            mamba_track_indices=mamba_track_indices,
+            mamba_track_mask=mamba_track_mask,
             encoder_lens=encoder_lens,
             global_num_tokens_gpu=global_num_tokens_gpu,
             global_num_tokens_for_logprob_gpu=global_num_tokens_for_logprob_gpu,
@@ -134,6 +147,10 @@ class GraphInputBuffers:
         if bs != raw_bs:
             self.seq_lens.fill_(seq_len_fill_value)
             self.out_cache_loc.zero_()
+            if self.mamba_track_indices is not None:
+                self.mamba_track_indices.zero_()
+            if self.mamba_track_mask is not None:
+                self.mamba_track_mask.fill_(False)
 
         # Common inputs
         self.input_ids[:raw_num_token].copy_(forward_batch.input_ids)
@@ -142,6 +159,17 @@ class GraphInputBuffers:
         self.out_cache_loc[:raw_num_token].copy_(forward_batch.out_cache_loc)
         self.positions[:raw_num_token].copy_(forward_batch.positions)
 
+        if (
+            self.mamba_track_indices is not None
+            and forward_batch.mamba_track_indices is not None
+        ):
+            self.mamba_track_indices[:raw_bs].copy_(forward_batch.mamba_track_indices)
+        if (
+            self.mamba_track_mask is not None
+            and forward_batch.mamba_track_mask is not None
+        ):
+            self.mamba_track_mask[:raw_bs].copy_(forward_batch.mamba_track_mask)
+
         seq_lens_cpu: Optional[torch.Tensor] = None
         if forward_batch.seq_lens_cpu is not None:
             if bs != raw_bs:

python/sglang/srt/model_executor/model_runner.py

@@ -238,8 +238,10 @@ def add_chunked_prefix_cache_attention_backend(backend_name):
 # Detect stragger ranks in model loading
 UNBALANCED_MODEL_LOADING_TIMEOUT_S = 480  # leave more time for post data processing
 
-# the ratio of mamba cache pool size to max_running_requests, it will be safe when it is larger than 2 (yizhang2077)
+# the ratio of mamba cache pool size to max_running_requests
 MAMBA_CACHE_SIZE_MAX_RUNNING_REQUESTS_RATIO = 3
+MAMBA_CACHE_V2_ADDITIONAL_RATIO_OVERLAP = 2
+MAMBA_CACHE_V2_ADDITIONAL_RATIO_NO_OVERLAP = 1
 
 logger = logging.getLogger(__name__)
 
@@ -1446,14 +1448,9 @@ class ModelRunner:
         server_args = self.server_args
         assert config is not None
 
-        speculativa_ratio = (
-            0
-            if server_args.speculative_num_draft_tokens is None
-            else server_args.speculative_num_draft_tokens
-        )
         if (
             server_args.disable_radix_cache
-            or config.mamba2_cache_params.mamba_cache_per_req == 0
+            or server_args.max_mamba_cache_size is not None
         ):
             # with disable radix cache, sets the max_mamba_cache_size based on the max_running_requests
             if server_args.max_mamba_cache_size is None:
@@ -1461,7 +1458,25 @@ class ModelRunner:
                     server_args.max_mamba_cache_size = server_args.max_running_requests
                 else:
                     server_args.max_mamba_cache_size = 512
+            server_args.max_mamba_cache_size = server_args.max_mamba_cache_size // (
+                server_args.dp_size if server_args.enable_dp_attention else 1
+            )
         else:
+            assert config.mamba2_cache_params.mamba_cache_per_req > 0
+            # reserve the memory for the intermediate mamba states used for spec dec
+            if not self.spec_algorithm.is_none():
+                assert server_args.speculative_num_draft_tokens is not None
+                assert server_args.max_running_requests is not None
+
+                mamba_state_intermediate_size = (
+                    config.mamba2_cache_params.mamba_cache_per_req
+                    * server_args.max_running_requests
+                    * server_args.speculative_num_draft_tokens
+                )
+                total_rest_memory = total_rest_memory - (
+                    mamba_state_intermediate_size / (1 << 30)
+                )
+
             # allocate the memory based on the ratio between mamba state memory vs. full kv cache memory
             # solve the equations:
             # 1. mamba_state_memory + full_kv_cache_memory == total_rest_memory
@@ -1475,21 +1490,22 @@ class ModelRunner:
             server_args.max_mamba_cache_size = int(
                 (mamba_state_memory_raw * (1 << 30))
                 // config.mamba2_cache_params.mamba_cache_per_req
-                // (1 + speculativa_ratio)
             )
 
-        if self.hybrid_gdn_config is not None:
-            server_args.max_mamba_cache_size = server_args.max_mamba_cache_size // (
-                server_args.dp_size if server_args.enable_dp_attention else 1
-            )
         mamba_state_memory = (
             server_args.max_mamba_cache_size
             * config.mamba2_cache_params.mamba_cache_per_req
-            * (1 + speculativa_ratio)
             / (1 << 30)
         )
         return total_rest_memory - mamba_state_memory
 
+    @property
+    def qwen3_next_config(self):
+        config = self.model_config.hf_config
+        if isinstance(config, Qwen3NextConfig):
+            return config
+        return None
+
     @property
     def hybrid_gdn_config(self):
         config = self.model_config.hf_config
@@ -1683,11 +1699,18 @@ class ModelRunner:
             )
 
         if self.mambaish_config is not None:
-            ratio = (
+            additional_ratio = 0
-                MAMBA_CACHE_SIZE_MAX_RUNNING_REQUESTS_RATIO
+            if (
-                if not self.server_args.disable_radix_cache
+                self.server_args.enable_mamba_extra_buffer()
-                else 1
+                and not self.spec_algorithm.is_none()
-            )
+            ):
+                additional_ratio = MAMBA_CACHE_V2_ADDITIONAL_RATIO_NO_OVERLAP
+            else:
+                additional_ratio = MAMBA_CACHE_V2_ADDITIONAL_RATIO_OVERLAP
+            if self.server_args.disable_radix_cache:
+                ratio = 1
+            else:
+                ratio = MAMBA_CACHE_SIZE_MAX_RUNNING_REQUESTS_RATIO + additional_ratio
             max_num_reqs = min(
                 max_num_reqs, self.server_args.max_mamba_cache_size // ratio
             )
@@ -1789,11 +1812,13 @@ class ModelRunner:
                 self.req_to_token_pool = HybridReqToTokenPool(
                     size=max_num_reqs,
                     mamba_size=self.server_args.max_mamba_cache_size,
+                    mamba_spec_state_size=max_num_reqs,
                     max_context_len=self.model_config.context_len
                     + extra_max_context_len,
                     device=self.device,
                     enable_memory_saver=self.server_args.enable_memory_saver,
                     cache_params=config.mamba2_cache_params,
+                    enable_mamba_extra_buffer=self.server_args.enable_mamba_extra_buffer(),
                     speculative_num_draft_tokens=self.server_args.speculative_num_draft_tokens,
                 )
             else:

python/sglang/srt/server_args.py

@@ -30,6 +30,7 @@ import orjson
 from sglang.srt.connector import ConnectorType
 from sglang.srt.environ import ToolStrictLevel, envs
 from sglang.srt.function_call.function_call_parser import FunctionCallParser
+from sglang.srt.layers.attention.fla.chunk_delta_h import CHUNK_SIZE as FLA_CHUNK_SIZE
 from sglang.srt.lora.lora_registry import LoRARef
 from sglang.srt.parser.reasoning_parser import ReasoningParser
 from sglang.srt.utils.common import (
@@ -185,6 +186,8 @@ FP8_GEMM_RUNNER_BACKEND_CHOICES = [
 
 MAMBA_SSM_DTYPE_CHOICES = ["float32", "bfloat16"]
 
+mamba_scheduler_strategy_CHOICES = ["auto", "no_buffer", "extra_buffer"]
+
 
 # Allow external code to add more choices
 def add_load_format_choices(choices):
@@ -466,6 +469,8 @@ class ServerArgs:
     max_mamba_cache_size: Optional[int] = None
     mamba_ssm_dtype: str = "float32"
     mamba_full_memory_ratio: float = 0.9
+    mamba_scheduler_strategy: str = "auto"
+    mamba_track_interval: int = 256
 
     # Hierarchical cache
     enable_hierarchical_cache: bool = False
@@ -737,6 +742,10 @@ class ServerArgs:
             self.random_seed = random.randint(0, 1 << 30)
         if self.mm_process_config is None:
             self.mm_process_config = {}
+        if self.mamba_scheduler_strategy == "auto":
+            # TODO: when extra_buffer is more verified, we can set the default path based on
+            #       [overlap, non-overlap]
+            self.mamba_scheduler_strategy = "no_buffer"
 
         # Handle ModelScope model downloads
         if get_bool_env_var("SGLANG_USE_MODELSCOPE"):
@@ -1333,12 +1342,6 @@ class ServerArgs:
                         f"{model_arch}"
                     )
         elif model_arch in ["Qwen3NextForCausalLM"]:
-            if 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"
-                )
-                self.disable_overlap_schedule = True
             if is_sm100_supported():
                 quantization_config = getattr(hf_config, "quantization_config", None)
                 quant_method = (
@@ -1372,15 +1375,52 @@ class ServerArgs:
                     )
                     self.disable_radix_cache = True
                     self.disable_overlap_schedule = False
+
+            # Mamba radix cache v2
+            if self.enable_mamba_extra_buffer():
+                assert (
+                    is_cuda()
+                ), "Mamba extra_buffer is only supported on CUDA devices with FLA backend"
+                assert (
+                    self.disaggregation_mode == "null"
+                ), "Mamba extra_buffer is not compatible with disaggregation mode yet."
+                if self.speculative_num_draft_tokens is not None:
+                    assert (
+                        self.mamba_track_interval >= self.speculative_num_draft_tokens
+                    ), f"mamba_track_interval {self.mamba_track_interval} must be greater than or equal to speculative_num_draft_tokens {self.speculative_num_draft_tokens}"
+
+                if self.page_size is not None:
+                    assert (
+                        self.mamba_track_interval % self.page_size == 0
+                    ), f"mamba_track_interval {self.mamba_track_interval} must be divisible by page_size {self.page_size}"
+                    assert (
+                        FLA_CHUNK_SIZE % self.page_size == 0
+                    ), f"Page size for hybrid GDN model must be divisible by {FLA_CHUNK_SIZE}, got {self.page_size}"
+
+                if self.speculative_algorithm is not None:
+                    logger.info(
+                        f"Disable overlap schedule for {model_arch} model speculative decoding."
+                    )
+                    self.disable_overlap_schedule = True
+            elif not self.disable_radix_cache:
+                logger.warning(
+                    "Disabling overlap schedule since MambaRadixCache no_buffer is not compatible with "
+                    "overlap schedule currently, try to use --mamba-scheduler-strategy extra_buffer to enable overlap schedule"
+                )
+                self.disable_overlap_schedule = True
+
         elif model_arch in [
             "FalconH1ForCausalLM",
             "JetNemotronForCausalLM",
             "JetVLMForConditionalGeneration",
         ]:
+            assert (
+                not self.enable_mamba_extra_buffer()
+            ), f"mamba extra_buffer is not supported for {model_arch} model"
             if not self.disable_radix_cache:
                 logger.warning(
-                    "Disabling overlap schedule since MambaRadixCache is not compatible with "
+                    "Disabling overlap schedule since mamba no_buffer is not compatible with "
-                    "overlap schedule currently, try to use --disable-radix-cache if overlap schedule is necessary"
+                    "overlap schedule, try to use --disable-radix-cache if overlap schedule is necessary"
                 )
                 self.disable_overlap_schedule = True
                 if is_sm100_supported():
@@ -3535,6 +3575,19 @@ class ServerArgs:
             default=ServerArgs.mamba_full_memory_ratio,
             help="The ratio of mamba state memory to full kv cache memory.",
         )
+        parser.add_argument(
+            "--mamba-scheduler-strategy",
+            type=str,
+            choices=mamba_scheduler_strategy_CHOICES,
+            default=ServerArgs.mamba_scheduler_strategy,
+            help="The strategy to use for mamba radix cache.",
+        )
+        parser.add_argument(
+            "--mamba-track-interval",
+            type=int,
+            default=ServerArgs.mamba_track_interval,
+            help="The interval to track the mamba state during decode.",
+        )
 
         # Hierarchical cache
         parser.add_argument(
@@ -4326,6 +4379,9 @@ class ServerArgs:
         model_config = self.get_model_config()
         return model_config.attention_arch == AttentionArch.MLA
 
+    def enable_mamba_extra_buffer(self) -> bool:
+        return self.mamba_scheduler_strategy == "extra_buffer"
+
     def check_server_args(self):
         # Check parallel size constraints
         assert (

python/sglang/srt/speculative/eagle_info.py

@@ -147,6 +147,16 @@ class EagleVerifyInput(SpecInput, EagleVerifyInputV2Mixin):
             bs,
         )
 
+        if get_global_server_args().enable_mamba_extra_buffer():
+            batch.mamba_track_indices = torch.tensor(
+                [
+                    req.mamba_ping_pong_track_buffer[req.mamba_next_track_idx]
+                    for req in batch.reqs
+                ],
+                dtype=torch.int64,
+                device=batch.device,
+            )
+
     def generate_attn_arg_prefill(
         self,
         req_pool_indices: torch.Tensor,

python/sglang/srt/speculative/eagle_worker.py

@@ -316,6 +316,7 @@ class EAGLEWorker(TpModelWorker):
                 logits_output=logits_output,
                 next_token_ids=verify_output.verified_id,
                 num_accepted_tokens=sum(verify_output.accept_length_per_req_cpu),
+                accept_length_per_req_cpu=verify_output.accept_length_per_req_cpu,
                 can_run_cuda_graph=can_run_cuda_graph,
             )
 
@@ -669,6 +670,7 @@ class EAGLEWorker(TpModelWorker):
         pass
 
     def verify(self, batch: ScheduleBatch, spec_info: EagleVerifyInput):
+        seq_lens_pre_verify = batch.seq_lens.clone()
         spec_info.prepare_for_verify(batch, self.page_size)
         spec_info.num_tokens_per_batch = self.speculative_num_steps + 1
         batch.return_hidden_states = False
@@ -743,44 +745,8 @@ class EAGLEWorker(TpModelWorker):
             self.target_worker.model_runner.hybrid_gdn_config is not None
             or self.target_worker.model_runner.mamba2_config is not None
         ):
-            accepted_length = (
+            self._mamba_verify_update(
-                torch.tensor(
+                batch, res, logits_output, spec_info, seq_lens_pre_verify
-                    res.accept_length_per_req_cpu,
-                    device=logits_output.hidden_states.device,
-                    dtype=torch.int64,
-                )
-                + 1
-            )
-
-            # If topk > 1, we need to use retrieve_next_token and retrieve_next_sibling to handle the eagle tree custom attention mask
-            # res.accepted_indices.shape[0] > 0 skips DP attn idle batch
-            if spec_info.topk > 1 and res.accepted_indices.shape[0] > 0:
-                # accepted_indices=[0,2,3,4,5,7,9,10,11], accepted_length=[4, 3, 2], cumulative_accepted_lengths=[4, 7, 9]
-                # first_token_indices_per_req=prepend(0, accepted_indices[cumulative_accepted_lengths[:-1]]) = [0, 5, 10]
-                # last_token_indices_per_req=accepted_indices[cumulative_accepted_lengths - 1] = [4, 9, 11] (last token ID of each req)
-                # max_relative_indices_per_req = [4,4,1]; those are the per-req spec-decoding step offsets that contain the correct mamba caches
-                cumulative_accepted_lengths = torch.cumsum(accepted_length, dim=0)
-                req_start_positions = torch.cat(
-                    [
-                        torch.zeros(
-                            1,
-                            dtype=cumulative_accepted_lengths.dtype,
-                            device=cumulative_accepted_lengths.device,
-                        ),
-                        cumulative_accepted_lengths[:-1],
-                    ]
-                )
-                first_token_indices_per_req = res.accepted_indices[req_start_positions]
-                last_token_indices_per_req = res.accepted_indices[
-                    cumulative_accepted_lengths - 1
-                ]
-                max_relative_indices_per_req = (
-                    last_token_indices_per_req - first_token_indices_per_req
-                )
-            else:
-                max_relative_indices_per_req = accepted_length - 1
-            self.target_worker.model_runner.attn_backend.update_mamba_state_after_mtp_verify(
-                max_relative_indices_per_req, self.target_worker.model_runner.model
             )
 
         if batch.return_logprob:
@@ -794,6 +760,85 @@ class EAGLEWorker(TpModelWorker):
 
         return logits_output, res, model_worker_batch, can_run_cuda_graph
 
+    def _mamba_verify_update(
+        self,
+        batch: ScheduleBatch,
+        res: EagleVerifyOutput,
+        logits_output: LogitsProcessorOutput,
+        spec_info: EagleVerifyInput,
+        seq_lens_pre_verify: torch.Tensor,
+    ):
+        accepted_length = (
+            torch.tensor(
+                res.accept_length_per_req_cpu,
+                device=logits_output.hidden_states.device,
+                dtype=torch.int64,
+            )
+            + 1
+        )
+        cumulative_accepted_lengths = torch.cumsum(accepted_length, dim=0)
+        # prepend 0 to the cumulative_accepted_lengths
+        accepted_indices_start = torch.cat(
+            [
+                torch.zeros(
+                    1,
+                    dtype=cumulative_accepted_lengths.dtype,
+                    device=cumulative_accepted_lengths.device,
+                ),
+                cumulative_accepted_lengths[:-1],
+            ]
+        )
+        accepted_indices_offset = torch.arange(
+            0,
+            len(batch.seq_lens) * batch.spec_info.draft_token_num,
+            step=batch.spec_info.draft_token_num,
+            dtype=accepted_indices_start.dtype,
+            device=accepted_indices_start.device,
+        )
+
+        # If topk > 1, we need to use retrieve_next_token and retrieve_next_sibling to handle the eagle tree custom attention mask
+        # res.accepted_indices.shape[0] > 0 skips DP attn idle batch
+        if spec_info.topk > 1 and res.accepted_indices.shape[0] > 0:
+            # accepted_indices=[0,2,3,4,5,7,9,10,11], accepted_length=[4, 3, 2], cumulative_accepted_lengths=[4, 7, 9]
+            # first_token_indices_per_req=prepend(0, accepted_indices[cumulative_accepted_lengths[:-1]]) = [0, 5, 10]
+            # last_token_indices_per_req=accepted_indices[cumulative_accepted_lengths - 1] = [4, 9, 11] (last token ID of each req)
+            # max_relative_indices_per_req = [4,4,1]; those are the per-req spec-decoding step offsets that contain the correct mamba caches
+            # first_token_indices_per_req = res.accepted_indices[accepted_indices_start]
+            accepted_steps = (
+                res.accepted_indices[cumulative_accepted_lengths - 1]
+                - accepted_indices_offset
+            )
+        else:
+            accepted_steps = accepted_length - 1
+
+        if batch.mamba_track_indices is not None:
+            # If after verify, the request's seq_lens has crossed a mamba track interval,
+            # we need to update the mamba state for the request at the crossing point.
+            mamba_track_interval = self.server_args.mamba_track_interval
+            to_track_mask = (
+                seq_lens_pre_verify // mamba_track_interval
+                != batch.seq_lens // mamba_track_interval
+            )
+            tracking_point = (
+                batch.seq_lens // mamba_track_interval * mamba_track_interval
+            )
+            to_track_ith = torch.clamp(tracking_point - seq_lens_pre_verify - 1, min=0)
+            mamba_steps_to_track = torch.where(
+                to_track_mask,
+                res.accepted_indices[to_track_ith + accepted_indices_start]
+                - accepted_indices_offset,
+                -1,
+            )
+        else:
+            mamba_steps_to_track = None
+
+        self.target_worker.model_runner.attn_backend.update_mamba_state_after_mtp_verify(
+            accepted_steps=accepted_steps,
+            mamba_track_indices=batch.mamba_track_indices,
+            mamba_steps_to_track=mamba_steps_to_track,
+            model=self.target_worker.model_runner.model,
+        )
+
     def add_logprob_values(
         self,
         batch: ScheduleBatch,

python/sglang/test/kl_test_utils.py

@@ -1,6 +1,7 @@
 import inspect
 import json
 import os
+import random
 
 import numpy as np
 import requests
@@ -79,8 +80,9 @@ def get_input_ids(
             break
         text = format_longbench_v2_example(example)
         tokens = tokenizer.encode(text)
-        # Truncate to max_tokens
+        # Truncate to a random length between 0.5x and 1.5x of max_prompt_tokens
-        input_ids.append(tokens[:max_prompt_tokens])
+        truncate_len = int(max_prompt_tokens * random.uniform(0.5, 1.5))
+        input_ids.append(tokens[:truncate_len])
 
     # Save to local cache
     with open(cache_file, "w") as f:

test/srt/models/test_qwen3_next_models.py

@@ -1,6 +1,8 @@
 import unittest
 from types import SimpleNamespace
 
+import requests
+
 from sglang.srt.utils import kill_process_tree
 from sglang.test.few_shot_gsm8k import run_eval
 from sglang.test.kl_test_utils import (
@@ -16,7 +18,22 @@ from sglang.test.test_utils import (
 
 QWEN3_NEXT_MODEL = "Qwen/Qwen3-Next-80B-A3B-Instruct"
 
-ACC_THRESHOLDS = {QWEN3_NEXT_MODEL: {"kl_div": 0.01, "gsm8k": 0.93}}
+ACC_THRESHOLDS = {
+    QWEN3_NEXT_MODEL: {"kl_div": 0.008, "gsm8k": 0.93},
+}
+
+
+def send_request_helper(base_url: str, text: str):
+    response = requests.post(
+        base_url + "/generate",
+        json={
+            "text": text,
+            "sampling_params": {
+                "max_new_tokens": 1,
+            },
+        },
+    )
+    return response.json()
 
 
 class TestQwen3Next(CustomTestCase):
@@ -33,6 +50,10 @@ class TestQwen3Next(CustomTestCase):
                 "4",
                 "--chunked-prefill-size",
                 "2048",
+                "--mamba-scheduler-strategy",
+                "extra_buffer",
+                "--mamba-track-interval",
+                "128",
             ],
         )
 
@@ -61,8 +82,8 @@ class TestQwen3Next(CustomTestCase):
             self.base_url,
             ACC_THRESHOLDS,
             self.model,
-            max_samples=16,
+            max_samples=32,
-            max_new_tokens=256,
+            max_new_tokens=512,
         )
 
     def test_input_output_logprobs_match_decode_cache_hit(self):
@@ -70,10 +91,37 @@ class TestQwen3Next(CustomTestCase):
             self.base_url,
             ACC_THRESHOLDS,
             self.model,
-            max_samples=16,
+            max_samples=32,
-            max_new_tokens=256,
+            max_new_tokens=512,
         )
 
+    def test_prefix_cache_branching(self):
+        print("running test_prefix_cache_branching")
+        requests.get(self.base_url + "/flush_cache")
+        branching_pos = 257
+        text_prefix = "hi" * branching_pos
+        suffix_list = ["this" * 256, "here" * 256, "that" * 256]
+        cache_hit_list = [False, False, True]
+
+        # First request only prefill the entire sequence
+        # Second request won't have cache hit, but will cache the branching point
+        # Third request will have cache hit on the branching point
+        for i, (suffix, cache_hit) in enumerate(
+            zip(suffix_list, cache_hit_list, strict=True)
+        ):
+            result = send_request_helper(self.base_url, text_prefix + suffix)
+            cached_tokens = result["meta_info"]["cached_tokens"]
+            if cache_hit:
+                expected_cached_tokens = branching_pos // 64 * 64
+                assert (
+                    cached_tokens == expected_cached_tokens
+                ), f"{i=}, {cache_hit=}, {cached_tokens=} is not equal to {expected_cached_tokens=}, {branching_pos=}"
+            else:
+                assert (
+                    cached_tokens == 0
+                ), f"{i=}, {cache_hit=}, {cached_tokens=} is not 0"
+        print("test_prefix_cache_branching passed")
+
 
 class TestQwen3NextMTP(CustomTestCase):
     @classmethod
@@ -98,6 +146,10 @@ class TestQwen3NextMTP(CustomTestCase):
                 "0.8",
                 "--tp",
                 "4",
+                "--chunked-prefill-size",
+                "2048",
+                "--mamba-scheduler-strategy",
+                "no_buffer",
             ],
         )
 
@@ -121,6 +173,24 @@ class TestQwen3NextMTP(CustomTestCase):
             metrics["accuracy"], ACC_THRESHOLDS[self.model]["gsm8k"]
         )
 
+    def test_input_output_logprobs_match_prefill_cache_hit(self):
+        test_input_output_logprobs_match_prefill_cache_hit_helper(
+            self.base_url,
+            ACC_THRESHOLDS,
+            self.model,
+            max_samples=32,
+            max_new_tokens=512,
+        )
+
+    def test_input_output_logprobs_match_decode_cache_hit(self):
+        test_input_output_logprobs_match_decode_cache_hit_helper(
+            self.base_url,
+            ACC_THRESHOLDS,
+            self.model,
+            max_samples=32,
+            max_new_tokens=512,
+        )
+
 
 class TestQwen3NextMTPTopk(CustomTestCase):
     @classmethod
@@ -145,6 +215,12 @@ class TestQwen3NextMTPTopk(CustomTestCase):
                 "0.8",
                 "--tp",
                 "4",
+                "--chunked-prefill-size",
+                "2048",
+                "--mamba-scheduler-strategy",
+                "extra_buffer",
+                "--mamba-track-interval",
+                "128",
             ],
         )
 
@@ -168,6 +244,51 @@ class TestQwen3NextMTPTopk(CustomTestCase):
             metrics["accuracy"], ACC_THRESHOLDS[self.model]["gsm8k"]
         )
 
+    def test_input_output_logprobs_match_prefill_cache_hit(self):
+        test_input_output_logprobs_match_prefill_cache_hit_helper(
+            self.base_url,
+            ACC_THRESHOLDS,
+            self.model,
+            max_samples=32,
+            max_new_tokens=512,
+        )
+
+    def test_input_output_logprobs_match_decode_cache_hit(self):
+        test_input_output_logprobs_match_decode_cache_hit_helper(
+            self.base_url,
+            ACC_THRESHOLDS,
+            self.model,
+            max_samples=32,
+            max_new_tokens=512,
+        )
+
+    def test_prefix_cache_branching(self):
+        print("running test_prefix_cache_branching")
+        requests.get(self.base_url + "/flush_cache")
+        branching_pos = 257
+        text_prefix = "hi" * branching_pos
+        suffix_list = ["this" * 256, "here" * 256, "that" * 256]
+        cache_hit_list = [False, False, True]
+
+        # First request only prefill the entire sequence
+        # Second request won't have cache hit, but will cache the branching point
+        # Third request will have cache hit on the branching point
+        for i, (suffix, cache_hit) in enumerate(
+            zip(suffix_list, cache_hit_list, strict=True)
+        ):
+            result = send_request_helper(self.base_url, text_prefix + suffix)
+            cached_tokens = result["meta_info"]["cached_tokens"]
+            if cache_hit:
+                expected_cached_tokens = branching_pos // 64 * 64
+                assert (
+                    cached_tokens == expected_cached_tokens
+                ), f"{i=}, {cache_hit=}, {cached_tokens=} is not equal to {expected_cached_tokens=}, {branching_pos=}"
+            else:
+                assert (
+                    cached_tokens == 0
+                ), f"{i=}, {cache_hit=}, {cached_tokens=} is not 0"
+        print("test_prefix_cache_branching passed")
+
 
 class TestQwen3NextPiecewiseCudaGraph(CustomTestCase):
 

test/srt/run_suite.py

@@ -146,7 +146,7 @@ suites = {
         TestFile("test_eagle_dp_attention.py", 200),
     ],
     "per-commit-4-gpu": [
-        TestFile("models/test_qwen3_next_models.py", 472),
+        TestFile("models/test_qwen3_next_models.py", 590),
         TestFile("test_gpt_oss_4gpu.py", 300),
         TestFile("test_local_attn.py", 411),
         TestFile("test_multi_instance_release_memory_occupation.py", 64),

test/srt/test_mamba_unittest.py

@@ -81,10 +81,12 @@ class TestMamba(unittest.TestCase):
         req_to_token_pool = HybridReqToTokenPool(
             size=max_num_reqs,
             mamba_size=mamba_cache_size,
+            mamba_spec_state_size=max_num_reqs,
             max_context_len=max_context_len,
             device=device,
             enable_memory_saver=False,
             cache_params=mamba2_cache_params,
+            enable_mamba_extra_buffer=False,
             speculative_num_draft_tokens=3,
         )
 
@@ -159,10 +161,12 @@ class TestMamba(unittest.TestCase):
         req_to_token_pool = HybridReqToTokenPool(
             size=max_num_reqs,
             mamba_size=mamba_cache_size,
+            mamba_spec_state_size=max_num_reqs,
             max_context_len=max_context_len,
             device=device,
             enable_memory_saver=False,
             cache_params=mamba2_cache_params,
+            enable_mamba_extra_buffer=False,
             speculative_num_draft_tokens=3,
         )
         # setup kv pool