[AMD ]Feat/dsv4 ep tbo prefill (#29362)

Co-authored-by: wunhuang <wunhuang@amd.com>
Co-authored-by: At1a8 <fangyuan@amd.com>

python/sglang/srt/batch_overlap/operations_strategy.py

@@ -63,6 +63,15 @@ class OperationsStrategy:
                     for layer in layers
                 ]
             )
+        elif layer_name == "DeepseekV4DecoderLayer":
+            return OperationsStrategy.concat(
+                [
+                    _compute_moe_deepseek_v4_layer_operations_strategy_tbo(
+                        layer, forward_mode
+                    )
+                    for layer in layers
+                ]
+            )
         else:
             raise NotImplementedError
 
@@ -150,6 +159,73 @@ def _compute_moe_deepseek_blog_decode(layer):
     )
 
 
+# -------------------------------- Strategy for DeepSeek V4 ---------------------------------------
+
+
+# DSV4 prefill TBO (EP / mori path). Cross-layer mHC fusion is disabled under
+# TBO, so each layer is self-contained: attn-side mHC pre+norm -> attn ->
+# ffn-side mHC pre+norm -> MoE (a2a dispatch/combine overlapped) -> mHC post.
+# The MoE ops are reused from self.mlp (DeepseekV2MoE) and decompose
+# forward_deepep; the layer-level op_mhc_* wrap DSV4's hc_pre / hc_post.
+def _compute_moe_deepseek_v4_layer_operations_strategy_tbo(
+    layer: torch.nn.Module,
+    forward_mode: ForwardMode,
+) -> OperationsStrategy:
+    if forward_mode == ForwardMode.EXTEND:
+        return _compute_moe_deepseek_v4_prefill(layer)
+    else:
+        # Decode TBO for DSV4 is not implemented yet (ATOM data: decode TBO
+        # regresses; needs cuda-graph capture work). Prefill-only for now.
+        raise NotImplementedError(
+            f"DeepseekV4 TBO only supports prefill (EXTEND), got {forward_mode=}"
+        )
+
+
+def _compute_moe_deepseek_v4_prefill(layer):
+    from sglang.srt.layers.moe import get_moe_a2a_backend
+
+    if get_moe_a2a_backend().is_none():
+        # Non-EP DP TP-MoE: overlap the DP all_gatherv (gather) + reduce_scatterv
+        # (combine) with the other ubatch's attn+MoE compute (ATOM's DSV4 path).
+        ops = [
+            layer.op_mhc_prepare_attn,
+            layer.self_attn.op_attn,
+            layer.op_mhc_post_attn_pre_mlp,
+            layer.op_gather_a,
+            operations.YieldOperation(),
+            layer.op_gather_b,
+            layer.op_moe,
+            layer.op_combine_a,
+            operations.YieldOperation(),
+            layer.op_combine_b,
+            layer.op_mhc_postprocess,
+        ]
+    else:
+        # EP / mori a2a: reuse DeepseekV2MoE's deepep dispatch/combine ops.
+        ops = [
+            layer.op_mhc_prepare_attn,
+            layer.self_attn.op_attn,
+            layer.op_mhc_post_attn_pre_mlp,
+            layer.mlp.op_gate,
+            layer.mlp.op_select_experts,
+            layer.mlp.op_dispatch_a,
+            operations.YieldOperation(),
+            layer.mlp.op_dispatch_b,
+            layer.mlp.op_experts,
+            layer.mlp.op_combine_a,
+            operations.YieldOperation(),
+            layer.mlp.op_shared_experts,
+            layer.mlp.op_combine_b,
+            layer.mlp.op_output,
+            layer.op_mhc_postprocess,
+        ]
+    return OperationsStrategy(
+        deep_gemm_num_sms=None,
+        tbo_delta_stages=0,
+        operations=ops,
+    )
+
+
 # -------------------------------- Strategy for Qwen3 ---------------------------------------
 
 

python/sglang/srt/batch_overlap/two_batch_overlap.py

@@ -103,9 +103,28 @@ def _is_two_chunk_split_enabled(extend_lens: Sequence[int]) -> bool:
     overall_sum = sum(extend_lens)
     threshold = get_tbo_token_distribution_threshold()
     assert threshold <= 0.5, f"{threshold=}"
-    return left_sum < overall_sum * threshold or left_sum > overall_sum * (
+    want_two_chunk = left_sum < overall_sum * threshold or left_sum > overall_sum * (
         1 - threshold
     )
+    if not want_two_chunk:
+        return False
+
+    # Two-chunk splits a single seq across both micro-batches by cutting at
+    # overall_sum // 2. child_a then spans seqs [0 : split_seq_index + 1]
+    # (batch_size = split_seq_index + 1) but only receives overall_sum // 2
+    # query tokens. For a degenerate batch (a single seq, or a near-empty
+    # DP-sync batch) this cut is 0 or tiny, leaving child_a with more seqs
+    # than query tokens (e.g. (bs=1, tok=0)). That violates the DSV4 compress
+    # planner invariant `batch_size <= num_q_tokens` and crashes the kernel.
+    # Fall back to a seq-boundary split, whose child_a is seq-aligned (each
+    # seq contributes >= 1 token) and cannot become empty-with-count.
+    split_seq_index = _split_array_by_cum_less_than_half(extend_lens)
+    child_a_batch_size = split_seq_index + 1
+    child_a_num_q_tokens = overall_sum // 2
+    if child_a_batch_size > child_a_num_q_tokens:
+        return False
+
+    return True
 
 
 def _split_extend_seqs(arr: Sequence[int]) -> int:
@@ -652,9 +671,10 @@ class TboForwardBatchPreparer:
             output_dict[key] = old_value[start_token_index:end_token_index]
 
         attention_tp_size = get_parallel().attn_tp_size
-        output_dict["tbo_padded_len"] = (
+        _tbo_padded_len = (
             (end_token_index - start_token_index - 1) // attention_tp_size + 1
         ) * attention_tp_size
+        output_dict["tbo_padded_len"] = _tbo_padded_len
 
         for key in [
             "req_pool_indices",

python/sglang/srt/layers/attention/deepseek_v4_backend_hip_radix.py

@@ -406,6 +406,14 @@ class _GraphBucket(enum.Enum):
 class DeepseekV4HipRadixBackend(
     AttentionBackend, C4IndexerBackendMixin, CompressorBackendMixin
 ):
+    # DSV4 TBO runs ONLY in eager prefill (prefill cuda-graph is disabled);
+    # decode/target-verify graphs are non-TBO (primary backend only). So the TBO
+    # child backends must not be driven through cuda-graph capture/replay — doing
+    # so rebuilds this backend's compressor/indexer metadata per replay step on
+    # both children and leaks ROCm HSA resources (HSA_STATUS_ERROR_OUT_OF_RESOURCES).
+    # TboAttnBackend reads this to skip children in the *_graph paths only.
+    tbo_supports_cuda_graph = False
+
     def __init__(
         self,
         model_runner: ModelRunner,

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

@@ -25,6 +25,20 @@ class TboAttnBackend(AttentionBackend):
             children=[creator() for _ in range(2)],
         )
 
+    def _children_use_cuda_graph(self) -> bool:
+        """Whether the TBO child backends participate in CUDA-graph capture/replay.
+
+        Some models only run TBO in eager prefill and keep their graph-captured
+        modes (decode / target-verify) NON-TBO on the primary backend. For those,
+        the children must NOT be driven through the cuda-graph paths: doing so
+        rebuilds their per-step metadata on every replay even though the captured
+        graph never uses them. For DeepSeek-V4 that metadata build (compressor /
+        indexer) leaks ROCm HSA resources across the 2 children -> eventual
+        HSA_STATUS_ERROR_OUT_OF_RESOURCES. Eager prefill TBO (init_forward_metadata)
+        is unaffected; only the *_graph paths are gated.
+        """
+        return getattr(self.primary, "tbo_supports_cuda_graph", True)
+
     def init_forward_metadata_out_graph(
         self,
         forward_batch: "ForwardBatch",
@@ -33,6 +47,8 @@ class TboAttnBackend(AttentionBackend):
         self.primary.init_forward_metadata_out_graph(
             forward_batch=forward_batch, in_capture=in_capture
         )
+        if not self._children_use_cuda_graph():
+            return
         tbo_children = getattr(forward_batch, "tbo_children", None)
         if tbo_children is not None:
             for child, forward_batch_child in zip(
@@ -97,6 +113,8 @@ class TboAttnBackend(AttentionBackend):
 
     def init_forward_metadata_in_graph(self, forward_batch: "ForwardBatch"):
         self.primary.init_forward_metadata_in_graph(forward_batch=forward_batch)
+        if not self._children_use_cuda_graph():
+            return
         tbo_children = getattr(forward_batch, "tbo_children", None)
         if tbo_children is not None:
             for child, forward_batch_child in zip(
@@ -118,17 +136,23 @@ class TboAttnBackend(AttentionBackend):
 
     def init_cuda_graph_state(self, max_bs: int, max_num_tokens: int):
         self.primary.init_cuda_graph_state(max_bs=max_bs, max_num_tokens=max_num_tokens)
+        if not self._children_use_cuda_graph():
+            return
         for item in self.children:
             # TODO for children, maybe can provide *smaller* max_bs to optimize
             item.init_cuda_graph_state(max_bs=max_bs, max_num_tokens=max_num_tokens)
 
     def on_after_cuda_graph_warmup(self):
         self.primary.on_after_cuda_graph_warmup()
+        if not self._children_use_cuda_graph():
+            return
         for child in self.children:
             child.on_after_cuda_graph_warmup()
 
     def get_cuda_graph_seq_len_fill_value(self):
         ans = self.primary.get_cuda_graph_seq_len_fill_value()
+        if not self._children_use_cuda_graph():
+            return ans
         for child in self.children:
             assert ans == child.get_cuda_graph_seq_len_fill_value()
         return ans
@@ -145,6 +169,19 @@ class TboAttnBackend(AttentionBackend):
     def get_indexer_metadata(self, layer_id: int, forward_batch: "ForwardBatch"):
         return self.primary.get_indexer_metadata(layer_id, forward_batch)
 
+    def __getattr__(self, name):
+        # Delegate backend-specific attributes/methods not explicitly wrapped
+        # above (e.g. DSV4's get_unified_swa_loc / get_swa_out_cache_loc, which
+        # the model calls directly via get_attn_backend()) to the primary
+        # full-batch backend. Inside TBO the per-child backend is resolved
+        # directly from the forward context, so this path only serves the
+        # non-overlapped forward (warmup / decode / TBO-ineligible batches).
+        # NOTE: __getattr__ runs only when normal lookup fails; guard `primary`
+        # to avoid infinite recursion before __init__ sets it.
+        if name == "primary":
+            raise AttributeError(name)
+        return getattr(self.primary, name)
+
 
 def _build_tbo_child_replay_fb_view(
     fb_view,

python/sglang/srt/layers/dp_attention.py

@@ -691,6 +691,112 @@ def dp_reduce_scatter_tensor(output: torch.Tensor, input: torch.Tensor):
         get_attention_tp_group().all_gather_into_tensor(output, scattered_local_tokens)
 
 
+# ---------------------------------------------------------------------------
+# Two-batch-overlap (non-EP / DP TP-MoE) async gather + combine.
+#
+# The DP TP-MoE path (deepseek_v4) gathers local hidden -> a global buffer
+# before the experts and reduce-scatters back after. For TBO we run those two
+# collectives on a single shared comm stream (mirroring the mori dispatcher's
+# _comm_stream) and return a CUDA event, so the op engine can yield and let the
+# OTHER ubatch's attn+MoE compute run on the compute stream while this ubatch's
+# gather/combine proceeds on the comm stream. Both ubatches share ONE comm
+# stream -> their collectives serialize in-order (no concurrent-collective
+# deadlock on the RCCL communicator), each overlapping the other's compute.
+# ---------------------------------------------------------------------------
+_DP_TBO_COMM_STREAM: Optional[torch.cuda.Stream] = None
+
+
+def get_dp_tbo_comm_stream() -> torch.cuda.Stream:
+    global _DP_TBO_COMM_STREAM
+    if _DP_TBO_COMM_STREAM is None:
+        _DP_TBO_COMM_STREAM = torch.cuda.Stream()
+    return _DP_TBO_COMM_STREAM
+
+
+# Persistent reusable CUDA events for non-EP DP TBO, keyed by (kind, subbatch).
+# CRITICAL: do NOT create a fresh event per gather/combine -- that is ~244 new
+# torch.cuda.Event per forward (61 layers x 2 ubatches x 2), and the HSA signal
+# pool is exhausted after a few hundred forwards -> HSA_STATUS_ERROR_OUT_OF_RESOURCES
+# ("...create internal OS-specific events"). Reuse one event per (kind, subbatch)
+# and just re-record it (mirrors the mori CommStreamPool event reuse).
+_TBO_EVENT_POOL: dict = {}
+
+
+def _tbo_event(key) -> torch.cuda.Event:
+    ev = _TBO_EVENT_POOL.get(key)
+    if ev is None:
+        ev = torch.cuda.Event()
+        _TBO_EVENT_POOL[key] = ev
+    return ev
+
+
+def dp_gather_partial_async(
+    global_tokens: torch.Tensor,
+    local_tokens: torch.Tensor,
+    forward_batch: ForwardBatch,
+    event_key=("gather", 0),
+) -> torch.cuda.Event:
+    """Launch `dp_gather_partial` (all_gatherv) on the shared DP TBO comm stream;
+    re-record + return a PERSISTENT event (keyed by `event_key`) that fires when
+    the gather completes. Caller yields, then `compute_stream.wait_event(ev)`
+    before reading `global_tokens`."""
+    comm = get_dp_tbo_comm_stream()
+    compute = torch.cuda.current_stream()
+    # Keep buffers alive across streams (caching allocator).
+    local_tokens.record_stream(comm)
+    global_tokens.record_stream(comm)
+    ev = _tbo_event(event_key)
+    with torch.cuda.stream(comm):
+        comm.wait_stream(compute)  # inputs were produced on the compute stream
+        dp_gather_partial(global_tokens, local_tokens, forward_batch)
+        ev.record(comm)
+    return ev
+
+
+# Persistent grow-only buffers for non-EP DP TBO, keyed by (kind, tbo_subbatch).
+# Reused across ALL layers (and forwards) so the caching allocator does not churn
+# a fresh per-layer `torch.empty` for the 8x DP-gather / combine buffers. That
+# churn (different sizes per forward x 2 ubatches x 61 layers, kept alive by the
+# comm-stream record_stream) ballooned `reserved` to ~270GB and tripped
+# HSA_STATUS_ERROR_OUT_OF_RESOURCES at large prefill chunks, even though the live
+# (allocated) working set was only ~10GB.
+_TBO_PERSIST_BUF: dict = {}
+
+
+def get_tbo_persistent_buffer(
+    key, rows: int, hidden: int, dtype: torch.dtype, device
+) -> torch.Tensor:
+    """Return a [rows, hidden] view of a grow-only persistent buffer for `key`.
+    Reallocates only when the request exceeds the cached capacity / changes
+    dtype|hidden. Caller must treat the returned view as scratch (overwritten)."""
+    buf = _TBO_PERSIST_BUF.get(key)
+    cap = 0 if buf is None else buf.shape[0]
+    if buf is None or rows > cap or buf.shape[1] != hidden or buf.dtype != dtype:
+        new_rows = max(rows, cap)
+        buf = torch.empty((new_rows, hidden), dtype=dtype, device=device)
+        _TBO_PERSIST_BUF[key] = buf
+    return buf[:rows]
+
+
+def dp_reduce_scatterv_async(
+    output_local: torch.Tensor,
+    global_tokens: torch.Tensor,
+    sizes: List[int],
+    event_key=("combine", 0),
+) -> torch.cuda.Event:
+    """Launch the variable-length reduce_scatterv (combine) on the shared DP TBO
+    comm stream; re-record + return a PERSISTENT event (keyed by `event_key`).
+    Matches the gatherv (SUM_LEN) path."""
+    comm = get_dp_tbo_comm_stream()
+    compute = torch.cuda.current_stream()
+    ev = _tbo_event(event_key)
+    with torch.cuda.stream(comm):
+        comm.wait_stream(compute)
+        get_tp_group().reduce_scatterv(global_tokens, output=output_local, sizes=sizes)
+        ev.record(comm)
+    return ev
+
+
 def attn_tp_reduce_scatter_tensor(output: torch.Tensor, input: torch.Tensor):
     return get_attention_tp_group().reduce_scatter_tensor(output, input)
 

python/sglang/srt/models/deepseek_v2.py

@@ -1452,6 +1452,14 @@ class DeepseekV2MoE(nn.Module):
         router_logits = state.pop("router_logits")
         hidden_states = state.hidden_states_mlp_input
 
+        # Hash MoE layers (e.g. DeepSeek-V4) route on input_ids; forward_deepep
+        # passes them as a topk kwarg. The per-ubatch forward_batch.input_ids is
+        # already sliced+padded to match hidden_states rows (and equals the
+        # global ids under EP dp-attention). No-op for non-hash models.
+        topk_kwargs = {}
+        if getattr(self, "is_hash", False):
+            topk_kwargs["input_ids"] = state.forward_batch.input_ids
+
         if router_logits is not None:
             with get_global_expert_distribution_recorder().with_current_layer(
                 self.layer_id
@@ -1463,6 +1471,7 @@ class DeepseekV2MoE(nn.Module):
                     expert_location_dispatch_info=ExpertLocationDispatchInfo.init_new(
                         layer_id=self.layer_id,
                     ),
+                    **topk_kwargs,
                 )
         else:
             state.topk_output = self.topk.empty_topk_output(

python/sglang/srt/models/deepseek_v4.py

@@ -53,15 +53,21 @@ from sglang.srt.layers.deepseek_v4_rope import (
 )
 from sglang.srt.layers.dp_attention import (
     _DpGatheredBufferWrapper,
+    _tbo_event,
     attn_tp_all_gather,
     attn_tp_all_reduce,
     dp_gather_partial,
     dp_gather_replicate,
     dp_reduce_scatter_tensor,
+    dp_reduce_scatterv_async,
     dp_scatter,
     get_dp_global_num_tokens,
+    get_dp_tbo_comm_stream,
     get_global_dp_buffer,
+    get_global_dp_buffer_len,
     get_local_dp_buffer,
+    get_local_dp_buffer_len,
+    get_tbo_persistent_buffer,
     is_dp_attention_enabled,
     is_dp_gatherv_active,
 )
@@ -1108,6 +1114,21 @@ class MQALayer(nn.Module):
 
         return o
 
+    # ---- TBO op decomposition (prefill two-batch-overlap) ----
+    def op_attn(self, state):
+        """Run the attention forward as a single TBO op.
+
+        Consumes the post-input-norm hidden states produced by
+        ``DeepseekV4DecoderLayer.op_mhc_prepare_attn`` and stores the attention
+        output for ``op_mhc_post_attn_pre_mlp``.
+        """
+        state.hidden_states_after_attn = self.forward(
+            x=state.pop("hidden_states_after_input_norm"),
+            positions=state.positions,
+            forward_batch=state.forward_batch,
+            x_quant=state.pop("attn_x_quant"),
+        )
+
 
 class DeepseekV4DecoderLayer(nn.Module):
     def __init__(
@@ -1600,6 +1621,217 @@ class DeepseekV4DecoderLayer(nn.Module):
         # cross-layer fusion, and the final layer is completed in DeepseekV4Model.
         return hidden_states, residual, post, comb
 
+    # ------------------------------------------------------------------
+    # TBO op decomposition (prefill two-batch-overlap, EP / mori path)
+    #
+    # These mirror the NON-fused branch of ``forward`` (cross-layer mHC
+    # fusion is disabled under TBO, so every layer is self-contained), split
+    # into ops so the operations engine can overlap one ubatch's MoE a2a
+    # dispatch/combine with the other ubatch's attention + expert GEMM.
+    # The MoE ops themselves (op_gate / op_select_experts / op_dispatch_a/b /
+    # op_experts / op_combine_a/b / op_shared_experts / op_output) are reused
+    # as-is from ``self.mlp`` (DeepseekV2MoE) — they decompose ``forward_deepep``.
+    # ------------------------------------------------------------------
+    def op_mhc_prepare_attn(
+        self,
+        state,
+        positions: torch.Tensor,
+        hidden_states: torch.Tensor,
+        forward_batch: ForwardBatch,
+        residual: Optional[torch.Tensor] = None,
+        tbo_subbatch_index: Optional[int] = None,
+        **kwargs,
+    ):
+        # Non-fused attention-side mHC pre + input layernorm.
+        attn_residual = hidden_states
+        hidden_states, post, comb, norm_fused = self.hc_pre(
+            hidden_states,
+            self.hc_attn_fn,
+            self.hc_attn_scale,
+            self.hc_attn_base,
+            norm=self.input_layernorm,
+            forward_batch=forward_batch,
+        )
+        if not norm_fused:
+            if _use_aiter and _is_gfx95_supported:
+                x_quant, hidden_states = _fused_rmsnorm_fp8_quant(
+                    hidden_states,
+                    self.input_layernorm.weight,
+                    self.rms_norm_eps,
+                )
+            else:
+                hidden_states = self.input_layernorm(hidden_states)
+                x_quant = None
+        else:
+            x_quant = None
+
+        state.attn_residual = attn_residual
+        state.attn_post = post
+        state.attn_comb = comb
+        state.hidden_states_after_input_norm = hidden_states
+        state.attn_x_quant = x_quant
+        # mori's op_output slices final_hidden_states[:num_tokens].
+        if get_moe_a2a_backend().is_mori():
+            state.num_tokens = attn_residual.shape[0]
+        state.update(
+            dict(
+                forward_batch=forward_batch,
+                positions=positions,
+                tbo_subbatch_index=tbo_subbatch_index,
+            )
+        )
+
+    def op_mhc_post_attn_pre_mlp(self, state):
+        # Close the attention mHC (hc_post), then open the FFN-side mHC pre +
+        # post-attention layernorm. Produces the 2D MoE input.
+        hidden_states = self.hc_post(
+            state.pop("hidden_states_after_attn"),
+            state.pop("attn_residual"),
+            state.pop("attn_post"),
+            state.pop("attn_comb"),
+        )
+        ffn_residual = hidden_states
+        hidden_states, post, comb, norm_fused = self.hc_pre(
+            hidden_states,
+            self.hc_ffn_fn,
+            self.hc_ffn_scale,
+            self.hc_ffn_base,
+            norm=self.post_attention_layernorm,
+            forward_batch=state.forward_batch,
+        )
+        if not norm_fused:
+            hidden_states = self.post_attention_layernorm(hidden_states)
+        state.ffn_residual = ffn_residual
+        state.ffn_post = post
+        state.ffn_comb = comb
+        state.hidden_states_mlp_input = hidden_states
+
+    def op_mhc_postprocess(self, state):
+        # Close the FFN mHC (hc_post) and emit the next layer's input dict.
+        hidden_states = self.hc_post(
+            state.pop("hidden_states_mlp_output"),
+            state.pop("ffn_residual"),
+            state.pop("ffn_post"),
+            state.pop("ffn_comb"),
+        )
+        output = dict(
+            positions=state.positions,
+            hidden_states=hidden_states,
+            # DSV4 non-fused layers carry no residual across layers; the key is
+            # required by the next layer's op_mhc_prepare_attn (ignored) and by
+            # _model_forward_tbo_merge_outputs (None -> None).
+            residual=None,
+            forward_batch=state.forward_batch,
+            tbo_subbatch_index=state.tbo_subbatch_index,
+        )
+        state.clear(
+            expect_keys={
+                "positions",
+                "forward_batch",
+                "tbo_subbatch_index",
+            }
+        )
+        return output
+
+    # ------------------------------------------------------------------
+    # Non-EP (DP TP-MoE) TBO ops. Overlap the DP all_gatherv (pre-MoE gather)
+    # + reduce_scatterv (post-MoE combine) with the OTHER ubatch's attn+MoE
+    # compute. Used when moe_a2a_backend is "none" (DP-attention, TP-MoE) —
+    # the path ATOM uses for DSV4 (+~7.7% prefill). Replaces the EP mori
+    # op_dispatch/op_combine. op_mhc_* and op_attn are reused (local hidden).
+    # ------------------------------------------------------------------
+    def op_gather_a(self, state):
+        # Launch the all_gatherv (local hidden -> global buffer) + the input_ids
+        # replicate-gather on the shared comm stream; record an event.
+        fb = state.forward_batch
+        local = state.pop("hidden_states_mlp_input")  # LOCAL [M_local, hidden]
+        # Shared-expert-local: compute on LOCAL hidden before the gather; added
+        # back after the combine (same as the non-fused forward). Skipped in the
+        # global MoE via skip_shared_experts.
+        do_shared_local = (
+            _SHARED_EXPERT_LOCAL
+            and getattr(self.mlp, "shared_experts", None) is not None
+            and getattr(self.mlp, "_shared_expert_tp1", False)
+        )
+        state.do_shared_local = do_shared_local
+        state.shared_local = (
+            self.mlp._forward_shared_experts(local)
+            if (do_shared_local and local.shape[0] > 0)
+            else None
+        )
+        # Persistent grow-only scratch (keyed per ubatch) instead of a fresh
+        # torch.empty each layer -> stops the allocator's `reserved` from
+        # ballooning at large prefill chunks. input_ids_global is gathered ONCE
+        # per ubatch in _forward_layers_tbo (cached on fb), not here.
+        sub = state.tbo_subbatch_index
+        global_rows = get_global_dp_buffer_len()
+        global_hidden = get_tbo_persistent_buffer(
+            ("gh", sub), global_rows, local.shape[1], local.dtype, local.device
+        )
+        comm = get_dp_tbo_comm_stream()
+        compute = torch.cuda.current_stream()
+        with torch.cuda.stream(comm):
+            comm.wait_stream(compute)
+            dp_gather_partial(global_hidden, local, fb)
+            state.gather_event = _tbo_event(("gather", sub))
+            state.gather_event.record(comm)
+        state.gather_keepalive = local
+        state.global_hidden = global_hidden
+
+    def op_gather_b(self, state):
+        torch.cuda.current_stream().wait_event(state.pop("gather_event"))
+        # Compute now ordered after the gather -> the gather input is safe to
+        # release (freed on the compute stream, no record_stream deferral).
+        state.pop("gather_keepalive")
+
+    def op_moe(self, state):
+        # MoE (gate/topk/experts) on the GLOBAL gathered buffer. use_reduce_scatter
+        # skips the MoE-internal all_reduce (we reduce_scatterv in op_combine).
+        fb = state.forward_batch
+        global_hidden = state.pop("global_hidden")
+        global_ids = fb._tbo_global_input_ids
+        state.global_expert_out = self.mlp(
+            global_hidden,
+            fb,
+            use_reduce_scatter=True,
+            input_ids=global_ids,
+            input_ids_global=global_ids,
+            skip_shared_experts=state.do_shared_local,
+        )
+
+    def op_combine_a(self, state):
+        # Launch reduce_scatterv (global partial expert sums -> per-rank local) on
+        # the comm stream; record an event. Symmetric inverse of the all_gatherv.
+        global_out = state.pop("global_expert_out")
+        local_out = get_tbo_persistent_buffer(
+            ("lo", state.tbo_subbatch_index),
+            get_local_dp_buffer_len(),
+            global_out.shape[1],
+            global_out.dtype,
+            global_out.device,
+        )
+        state.combine_event = dp_reduce_scatterv_async(
+            local_out,
+            global_out,
+            get_dp_global_num_tokens(),
+            event_key=("combine", state.tbo_subbatch_index),
+        )
+        state.local_out = local_out
+        # Keep the (variable-size) MoE output alive until op_combine_b waits on
+        # the combine event (replaces record_stream; avoids reserved churn).
+        state.combine_keepalive = global_out
+
+    def op_combine_b(self, state):
+        torch.cuda.current_stream().wait_event(state.pop("combine_event"))
+        state.pop("combine_keepalive")
+        hidden = state.pop("local_out")
+        shared_local = state.pop("shared_local")
+        state.pop("do_shared_local")
+        if shared_local is not None:
+            n = hidden.shape[0]
+            hidden = hidden + shared_local[:n]
+        state.hidden_states_mlp_output = hidden
+
 
 class DeepseekV4Model(nn.Module):
     fall_back_to_pt_during_load = False
@@ -1695,6 +1927,116 @@ class DeepseekV4Model(nn.Module):
         y = torch.sum(pre.unsqueeze(-1) * x.view(shape), dim=1)
         return y.to(dtype)
 
+    def _can_run_tbo(self, forward_batch: ForwardBatch) -> bool:
+        """DSV4 prefill-only two-batch-overlap gate.
+
+        TBO batch prep (tbo_split_seq_index / tbo_children) is populated
+        model-agnostically when --enable-two-batch-overlap is set and the
+        DP-attention preparer allows it (mori `normal` mode permits prefill
+        TBO). We additionally restrict to: prefill (EXTEND), single PP, and the
+        non-CP path, which is the only case the DSV4 op strategy implements.
+        """
+        from sglang.srt.layers.moe import is_tbo_enabled
+
+        return (
+            is_tbo_enabled()
+            and forward_batch.can_run_tbo
+            and forward_batch.tbo_children is not None
+            and forward_batch.global_forward_mode is not None
+            and forward_batch.global_forward_mode.is_extend()
+            and not dsa_use_prefill_cp(forward_batch)
+            and self.pp_group.world_size == 1
+        )
+
+    def _forward_layers_tbo(
+        self,
+        positions: torch.Tensor,
+        hidden_states: torch.Tensor,
+        forward_batch: ForwardBatch,
+    ) -> torch.Tensor:
+        from sglang.srt.batch_overlap.operations import execute_overlapped_operations
+        from sglang.srt.batch_overlap.operations_strategy import OperationsStrategy
+        from sglang.srt.batch_overlap.two_batch_overlap import (
+            _model_forward_filter_inputs,
+            _model_forward_tbo_merge_outputs,
+        )
+
+        layers = [self.layers[i] for i in range(self.start_layer, self.end_layer)]
+        operations_strategy = OperationsStrategy.init_new_tbo(
+            layers, forward_batch.global_forward_mode
+        )
+
+        # Split the per-rank batch into the 2 ubatches (token-range slice + pad
+        # to tbo_padded_len). residual is unused by the DSV4 non-fused layer ops.
+        inputs_arr = [
+            _model_forward_filter_inputs(
+                hidden_states=hidden_states,
+                residual=None,
+                positions=positions,
+                output_forward_batch=child,
+                tbo_subbatch_index=idx,
+            )
+            for idx, child in enumerate(forward_batch.tbo_children)
+        ]
+
+        # Non-EP DP TP-MoE: the per-ubatch DP gather/combine (op_gather/op_combine)
+        # needs each ubatch's per-rank token counts, but tbo_padded_len is computed
+        # per-rank locally (not synced). All-gather both ubatches' padded lengths
+        # once across DP ranks, then populate each child's global_num_tokens +
+        # global_dp_buffer_len so the gatherv/reduce_scatterv buffers size correctly.
+        if get_moe_a2a_backend().is_none() and get_parallel().attn_dp_size > 1:
+            tp_group = get_tp_group()
+            world = tp_group.world_size
+            children = forward_batch.tbo_children
+            local_lens = torch.tensor(
+                [int(c.tbo_padded_len) for c in children],
+                dtype=torch.int64,
+                device=hidden_states.device,
+            )
+            gathered = torch.empty(
+                (world, local_lens.shape[0]),
+                dtype=torch.int64,
+                device=hidden_states.device,
+            )
+            tp_group.all_gather_into_tensor(gathered, local_lens)
+            gathered_cpu = gathered.tolist()
+            rank = tp_group.rank_in_group
+            for idx, child in enumerate(children):
+                sizes = [gathered_cpu[r][idx] for r in range(world)]
+                child.global_num_tokens_cpu = sizes
+                child.global_num_tokens_gpu = gathered[:, idx].contiguous()
+                child.global_dp_buffer_len = sum(sizes)
+                # Gather the ubatch's input_ids -> global ONCE here (cached on the
+                # child) instead of per-layer in op_gather_a. The hash MoE reads
+                # the SAME global ids every layer, so 61x2 per-layer all_gatherv of
+                # VARYING size (-> RCCL registers a new internal buffer per size ->
+                # HSA_STATUS_ERROR_OUT_OF_RESOURCES) collapses to 1 per ubatch.
+                local_ids = child.input_ids
+                rows = sizes[rank]
+                if local_ids.shape[0] < rows:
+                    padded_ids = local_ids.new_zeros((rows,))
+                    padded_ids[: local_ids.shape[0]] = local_ids
+                elif local_ids.shape[0] > rows:
+                    padded_ids = local_ids[:rows]
+                else:
+                    padded_ids = local_ids
+                gids = torch.empty(
+                    (sum(sizes),), dtype=local_ids.dtype, device=local_ids.device
+                )
+                tp_group.all_gatherv(padded_ids, sizes=sizes, output=gids)
+                child._tbo_global_input_ids = gids
+
+        outputs_arr = execute_overlapped_operations(
+            inputs_arr=inputs_arr,
+            operations_arr=[operations_strategy.operations] * 2,
+            delta_stages=[0, operations_strategy.tbo_delta_stages],
+        )
+
+        hidden_states, _ = _model_forward_tbo_merge_outputs(
+            outputs_arr[0], outputs_arr[1], hidden_states.shape[0]
+        )
+        return hidden_states
+
     def forward(
         self,
         input_ids: torch.Tensor,
@@ -1740,32 +2082,41 @@ class DeepseekV4Model(nn.Module):
             if hasattr(forward_batch, _attr):
                 delattr(forward_batch, _attr)
 
-        use_fused = self.use_fused_mhc_post_pre
+        if self._can_run_tbo(forward_batch):
-        prev_residual, prev_post, prev_comb = None, None, None
+            # Two-batch-overlap prefill (EP / mori). Cross-layer mHC fusion is
-        last_layer = None
+            # disabled here (each layer self-contained), so no trailing hc_post.
-        for i in range(self.start_layer, self.end_layer):
+            hidden_states = self._forward_layers_tbo(
-            layer = self.layers[i]
+                positions=positions,
-            last_layer = layer
+                hidden_states=hidden_states,
-            ctx = (
+                forward_batch=forward_batch,
-                nullcontext()
-                if check_cuda_graph_backend(Phase.PREFILL, Backend.TC_PIECEWISE)
-                else get_global_expert_distribution_recorder().with_current_layer(i)
             )
-            with ctx:
+        else:
-                hidden_states, prev_residual, prev_post, prev_comb = layer(
+            use_fused = self.use_fused_mhc_post_pre
-                    positions=positions,
+            prev_residual, prev_post, prev_comb = None, None, None
-                    hidden_states=hidden_states,
+            last_layer = None
-                    forward_batch=forward_batch,
+            for i in range(self.start_layer, self.end_layer):
-                    input_ids=input_ids,
+                layer = self.layers[i]
-                    input_ids_global=input_ids_global,
+                last_layer = layer
-                    prev_residual=prev_residual,
+                ctx = (
-                    prev_post=prev_post,
+                    nullcontext()
-                    prev_comb=prev_comb,
+                    if check_cuda_graph_backend(Phase.PREFILL, Backend.TC_PIECEWISE)
+                    else get_global_expert_distribution_recorder().with_current_layer(i)
+                )
+                with ctx:
+                    hidden_states, prev_residual, prev_post, prev_comb = layer(
+                        positions=positions,
+                        hidden_states=hidden_states,
+                        forward_batch=forward_batch,
+                        input_ids=input_ids,
+                        input_ids_global=input_ids_global,
+                        prev_residual=prev_residual,
+                        prev_post=prev_post,
+                        prev_comb=prev_comb,
+                    )
+            if use_fused and last_layer is not None:
+                hidden_states = last_layer.hc_post(
+                    hidden_states, prev_residual, prev_post, prev_comb
                 )
-        if use_fused and last_layer is not None:
-            hidden_states = last_layer.hc_post(
-                hidden_states, prev_residual, prev_post, prev_comb
-            )
 
         # CP all-gather only on the last PP rank; PP IPC carries CP-split tensors.
         if self.pp_group.is_last_rank and dsa_use_prefill_cp(forward_batch):

python/sglang/srt/server_args.py

@@ -6434,6 +6434,22 @@ class ServerArgs:
             self._mamba_cache_chunk_size = max(chunk_size, self.page_size)
         return self._mamba_cache_chunk_size
 
+    def _check_two_batch_overlap(self):
+        # With no EP a2a backend, two-batch-overlap is only valid on the non-EP
+        # DP TP-MoE path (overlapping the DP all_gatherv / reduce_scatterv with
+        # the other ubatch's compute), which requires DP attention. Enabling it
+        # there needs no extra opt-in env flag.
+        if (
+            self.enable_two_batch_overlap
+            and self.moe_a2a_backend == "none"
+            and not self.enable_dp_attention
+        ):
+            raise ValueError(
+                "When enabling two batch overlap without an EP a2a backend "
+                "(moe_a2a_backend='none'), --enable-dp-attention is required "
+                "(DeepSeek-V4 non-EP DP TBO path)."
+            )
+
     def check_server_args(self):
         # Check parallel size constraints
         assert (
@@ -6581,11 +6597,8 @@ class ServerArgs:
                 "--export-metrics-to-file-dir is required when --export-metrics-to-file is enabled"
             )
 
-        # Check two batch overlap
+        # Check two batch overlap backend requirement.
-        if self.enable_two_batch_overlap and self.moe_a2a_backend == "none":
+        self._check_two_batch_overlap()
-            raise ValueError(
-                "When enabling two batch overlap, moe_a2a_backend cannot be 'none'."
-            )
 
         # Check communications compression
         if self.enable_quant_communications and self.tp_size == 1:

test/registered/amd/test_deepseek_v4_flash_fp8_tbo.py

@@ -0,0 +1,163 @@
+"""MI35x DeepSeek-V4-Flash FP8 + non-EP DP two-batch-overlap (TBO) test (8-GPU)
+
+End-to-end accuracy test for DeepSeek-V4-Flash (285B) FP8 with the non-EP DP
+two-batch-overlap path on MI35x ROCm 7.2.
+
+TBO here is the DP-attention TP-MoE variant (moe_a2a_backend='none'): it overlaps
+one micro-batch's DP all_gatherv (pre-MoE gather) + reduce_scatterv (post-MoE
+combine) with the other micro-batch's attention + expert compute (prefill only).
+Enabled purely via `--enable-dp-attention` + `--enable-two-batch-overlap` (no opt-in
+env). This test guards that TBO does not regress GSM8K accuracy and that the DP TBO
+server launches + runs to completion (exercises op_gather/op_moe/op_combine and the
+event+ref combine-buffer lifetime that fixed the reserved-memory OOM at mem0.9).
+
+Unlike the CPU-only server-args guard unit test (TestTwoBatchOverlapBackend), this
+actually runs the TBO forward on the real model — which only DeepSeek-V4 implements,
+so it needs the real 8-GPU model (a dummy model path would not exercise TBO).
+
+Registry: nightly-amd-8-gpu-mi35x-deepseek-v4-flash suite
+"""
+
+import os
+import unittest
+from types import SimpleNamespace
+
+from sglang.srt.utils import kill_process_tree
+from sglang.test.ci.ci_register import register_amd_ci
+from sglang.test.few_shot_gsm8k import run_eval as run_eval_few_shot_gsm8k
+from sglang.test.test_utils import (
+    DEFAULT_URL_FOR_TEST,
+    CustomTestCase,
+    is_in_ci,
+    popen_launch_server,
+    write_github_step_summary,
+)
+
+register_amd_ci(
+    est_time=7200, suite="nightly-amd-8-gpu-mi35x-deepseek-v4-flash", nightly=True
+)
+
+DEEPSEEK_V4_FLASH_FP8_MODEL_PATH = os.environ.get(
+    "DEEPSEEK_V4_FP8_MODEL_PATH", "sgl-project/DeepSeek-V4-Flash-FP8"
+)
+SERVER_LAUNCH_TIMEOUT = 3600
+FLASHMLA_BACKEND = os.environ.get("SGLANG_HACK_FLASHMLA_BACKEND", "unified_kv_triton")
+
+# DSV4 fused-kernel optimal set (mirrors the validated dp-tbo launch config).
+# The DP + TBO forward path is sensitive to these; the non-TBO tp8 test can use a
+# leaner set, but DP TBO needs the full DSV4 opt env or the MoE/attn kernels hit
+# shape mismatches at warmup.
+COMMON_ENV_VARS = {
+    "SGLANG_DEFAULT_THINKING": "1",
+    "SGLANG_DSV4_REASONING_EFFORT": "max",
+    "SGLANG_OPT_DEEPGEMM_HC_PRENORM": "false",
+    "SGLANG_USE_AITER": "1",
+    "SGLANG_USE_ROCM700A": "0",
+    "SGLANG_OPT_USE_FUSED_COMPRESS": "true",
+    "SGLANG_HACK_FLASHMLA_BACKEND": FLASHMLA_BACKEND,
+    "SGLANG_OPT_FP8_WO_A_GEMM": "false",
+    "SGLANG_OPT_USE_JIT_INDEXER_METADATA": "false",
+    "SGLANG_OPT_USE_TOPK_V2": "false",
+    "SGLANG_OPT_USE_AITER_INDEXER": "true",
+    "SGLANG_OPT_USE_TILELANG_INDEXER": "false",
+    "SGLANG_OPT_USE_TILELANG_MHC_PRE": "false",
+    "SGLANG_OPT_USE_TILELANG_MHC_POST": "false",
+    "SGLANG_FP8_PAGED_MQA_LOGITS_TORCH": "1",
+    "SGLANG_OPT_USE_FUSED_COMPRESS_TRITON": "true",
+    "SGLANG_OPT_USE_MULTI_STREAM_OVERLAP": "false",
+    "SGLANG_ROCM_USE_MULTI_STREAM": "false",
+    "AITER_BF16_FP8_MOE_BOUND": "0",
+    "SGLANG_EAGER_INPUT_NO_COPY": "true",
+    # DP TP-MoE collective path that non-EP DP TBO overlaps.
+    "SGLANG_DP_USE_GATHERV": "1",
+    "SGLANG_DP_USE_REDUCE_SCATTER": "1",
+    "SGLANG_SHARED_EXPERT_TP1": "1",
+    "SGLANG_DP_SHARED_EXPERT_LOCAL": "1",
+    # ROCm HSA-resource stability for TBO at high concurrency.
+    "GPU_MAX_HW_QUEUES": "5",
+    # FP8 variant
+    "SGLANG_DSV4_FP4_EXPERTS": "false",
+}
+
+
+class TestDeepseekV4FlashFp8Tbo(CustomTestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.model = DEEPSEEK_V4_FLASH_FP8_MODEL_PATH
+        cls.base_url = DEFAULT_URL_FOR_TEST
+
+        env = os.environ.copy()
+        env.update(COMMON_ENV_VARS)
+
+        other_args = [
+            "--trust-remote-code",
+            "--tp",
+            "8",
+            # DP attention + TBO: non-EP DP TP-MoE two-batch-overlap. DP TBO is
+            # selected because moe_a2a_backend stays 'none'; no opt-in env needed.
+            "--dp",
+            "8",
+            "--enable-dp-attention",
+            "--enable-prefill-delayer",
+            "--enable-two-batch-overlap",
+            "--disable-radix-cache",
+            "--attention-backend",
+            "dsv4",
+            "--kv-cache-dtype",
+            "fp8_e4m3",
+            "--max-running-requests",
+            "512",
+            "--cuda-graph-max-bs",
+            "512",
+            "--page-size",
+            "256",
+            "--mem-fraction-static",
+            "0.90",
+            "--swa-full-tokens-ratio",
+            "0.15",
+            # global chunk; DP-attention divides by dp_size=8 -> 8192/rank.
+            "--chunked-prefill-size",
+            "65536",
+            "--disable-shared-experts-fusion",
+            "--tool-call-parser",
+            "deepseekv4",
+            "--reasoning-parser",
+            "deepseek-v4",
+        ]
+
+        cls.process = popen_launch_server(
+            cls.model,
+            cls.base_url,
+            timeout=SERVER_LAUNCH_TIMEOUT,
+            other_args=other_args,
+            env=env,
+        )
+
+    @classmethod
+    def tearDownClass(cls):
+        kill_process_tree(cls.process.pid)
+
+    def test_gsm8k_tbo(self):
+        args = SimpleNamespace(
+            num_shots=8,
+            data_path=None,
+            num_questions=1319,
+            parallel=1319,
+            max_new_tokens=512,
+            host="http://127.0.0.1",
+            port=int(self.base_url.split(":")[-1]),
+        )
+        metrics = run_eval_few_shot_gsm8k(args)
+        print(f"{metrics=}")
+
+        if is_in_ci():
+            write_github_step_summary(
+                f"### test_gsm8k_tbo (deepseek-v4-flash-fp8 DP+TBO, {FLASHMLA_BACKEND})\n"
+                f'{metrics["accuracy"]=:.3f}\n'
+            )
+        # TBO must not regress accuracy vs the non-TBO baseline (>0.91).
+        self.assertGreater(metrics["accuracy"], 0.91)
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/amd/test_deepseek_v4_pro_fp4_tbo.py

@@ -0,0 +1,151 @@
+"""MI35x DeepSeek-V4-Pro FP4 + non-EP DP two-batch-overlap (TBO) test (8-GPU)
+
+End-to-end accuracy test for DeepSeek-V4-Pro (1.6T) FP4 with the non-EP DP
+two-batch-overlap path on MI35x ROCm 7.2.
+
+TBO here is the DP-attention TP-MoE variant (moe_a2a_backend='none'): it overlaps
+one micro-batch's DP all_gatherv (pre-MoE gather) + reduce_scatterv (post-MoE
+combine) with the other micro-batch's attention + expert compute (prefill only).
+Enabled purely via `--enable-dp-attention` + `--enable-two-batch-overlap` (no opt-in
+env). This test guards that TBO does not regress GSM8K accuracy and that the DP TBO
+server launches + runs (exercises op_gather/op_moe/op_combine and the event+ref
+combine-buffer lifetime that fixed the reserved-memory OOM at mem0.9).
+
+Unlike the CPU-only server-args guard unit test (TestTwoBatchOverlapBackend), this
+runs the TBO forward on the real model — which only DeepSeek-V4 implements — so it
+needs the real 8-GPU model (a dummy model path would not exercise TBO). Uses the FP4
+Pro model (fp4 routed experts); do NOT force SGLANG_DSV4_FP4_EXPERTS=false here or
+the expert weights are read at the wrong (fp8) shape.
+
+Registry: nightly-amd-8-gpu-mi35x-deepseek-v4-pro suite
+"""
+
+import os
+import unittest
+from types import SimpleNamespace
+
+from sglang.srt.utils import kill_process_tree
+from sglang.test.ci.ci_register import register_amd_ci
+from sglang.test.few_shot_gsm8k import run_eval as run_eval_few_shot_gsm8k
+from sglang.test.test_utils import (
+    DEFAULT_URL_FOR_TEST,
+    CustomTestCase,
+    is_in_ci,
+    popen_launch_server,
+    write_github_step_summary,
+)
+
+register_amd_ci(
+    est_time=14400, suite="nightly-amd-8-gpu-mi35x-deepseek-v4-pro", nightly=True
+)
+
+DEEPSEEK_V4_PRO_FP4_MODEL_PATH = os.environ.get(
+    "DEEPSEEK_V4_PRO_MODEL_PATH_FP4", "deepseek-ai/DeepSeek-V4-Pro"
+)
+# Pro is 1.6T; weight load + warmup is much longer than Flash 285B.
+SERVER_LAUNCH_TIMEOUT = 5400
+FLASHMLA_BACKEND = os.environ.get("SGLANG_HACK_FLASHMLA_BACKEND", "unified_kv_triton")
+
+COMMON_ENV_VARS = {
+    "SGLANG_DEFAULT_THINKING": "1",
+    "SGLANG_DSV4_REASONING_EFFORT": "max",
+    "SGLANG_USE_ROCM700A": "0",
+    "SGLANG_HACK_FLASHMLA_BACKEND": FLASHMLA_BACKEND,
+    "AITER_BF16_FP8_MOE_BOUND": "0",
+    # DP TP-MoE collective path that non-EP DP TBO overlaps.
+    "SGLANG_DP_USE_GATHERV": "1",
+    "SGLANG_DP_USE_REDUCE_SCATTER": "1",
+    "SGLANG_SHARED_EXPERT_TP1": "1",
+    "SGLANG_DP_SHARED_EXPERT_LOCAL": "1",
+    # ROCm HSA-resource stability for TBO at high concurrency.
+    "GPU_MAX_HW_QUEUES": "5",
+}
+
+# FP4 variant
+FP4_ENV_VARS = {
+    "SGLANG_DSV4_FP4_EXPERTS": "true",
+}
+
+
+class TestDeepseekV4ProFp4Tbo(CustomTestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.model = DEEPSEEK_V4_PRO_FP4_MODEL_PATH
+        cls.base_url = DEFAULT_URL_FOR_TEST
+
+        env = os.environ.copy()
+        env.update(COMMON_ENV_VARS)
+        env.update(FP4_ENV_VARS)
+
+        other_args = [
+            "--trust-remote-code",
+            "--tp",
+            "8",
+            # DP attention + TBO: non-EP DP TP-MoE two-batch-overlap. DP TBO is
+            # selected because moe_a2a_backend stays 'none'; no opt-in env needed.
+            "--dp",
+            "8",
+            "--enable-dp-attention",
+            "--enable-prefill-delayer",
+            "--enable-two-batch-overlap",
+            "--disable-radix-cache",
+            "--attention-backend",
+            "dsv4",
+            "--kv-cache-dtype",
+            "fp8_e4m3",
+            "--max-running-requests",
+            "512",
+            "--cuda-graph-max-bs",
+            "512",
+            "--page-size",
+            "256",
+            "--mem-fraction-static",
+            "0.90",
+            "--swa-full-tokens-ratio",
+            "0.15",
+            # global chunk; DP-attention divides by dp_size=8 -> 8192/rank.
+            "--chunked-prefill-size",
+            "65536",
+            "--disable-shared-experts-fusion",
+            "--tool-call-parser",
+            "deepseekv4",
+            "--reasoning-parser",
+            "deepseek-v4",
+        ]
+
+        cls.process = popen_launch_server(
+            cls.model,
+            cls.base_url,
+            timeout=SERVER_LAUNCH_TIMEOUT,
+            other_args=other_args,
+            env=env,
+        )
+
+    @classmethod
+    def tearDownClass(cls):
+        kill_process_tree(cls.process.pid)
+
+    def test_gsm8k_tbo(self):
+        args = SimpleNamespace(
+            num_shots=8,
+            data_path=None,
+            num_questions=1319,
+            parallel=1319,
+            max_new_tokens=512,
+            host="http://127.0.0.1",
+            port=int(self.base_url.split(":")[-1]),
+        )
+        metrics = run_eval_few_shot_gsm8k(args)
+        print(f"{metrics=}")
+
+        if is_in_ci():
+            write_github_step_summary(
+                f"### test_gsm8k_tbo (deepseek-v4-pro-fp4 DP+TBO, {FLASHMLA_BACKEND})\n"
+                f'{metrics["accuracy"]=:.3f}\n'
+            )
+        # TBO must not regress accuracy vs the non-TBO baseline (>0.91).
+        self.assertGreater(metrics["accuracy"], 0.91)
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/unit/server_args/test_server_args.py

@@ -1364,5 +1364,48 @@ class TestSamplingBackendTokenOracleEnvGate(CustomTestCase):
         self.assertEqual(parsed.sampling_backend, "token_oracle")
 
 
+class TestTwoBatchOverlapBackend(CustomTestCase):
+    """Non-EP DP two-batch-overlap backend requirement.
+
+    With no EP a2a backend (moe_a2a_backend='none'), --enable-two-batch-overlap
+    is only valid on the DeepSeek-V4 non-EP DP TP-MoE path (overlapping the DP
+    all_gatherv / reduce_scatterv with the other ubatch's compute), which
+    requires --enable-dp-attention. This replaced the removed opt-in
+    SGLANG_ENABLE_DP_TBO env: enabling DP TBO now needs no extra flag.
+
+    dummy-model short-circuits __post_init__, so the guard handler is invoked
+    directly (same pattern as TestDeepEPWaterfillArgs)."""
+
+    def _args(self, **overrides):
+        args = ServerArgs(model_path="dummy")
+        args.enable_two_batch_overlap = True
+        args.moe_a2a_backend = "none"
+        args.enable_dp_attention = False
+        for key, value in overrides.items():
+            setattr(args, key, value)
+        return args
+
+    def test_no_a2a_without_dp_attention_raises(self):
+        args = self._args(enable_dp_attention=False)
+        with self.assertRaisesRegex(ValueError, "enable-dp-attention"):
+            args._check_two_batch_overlap()
+
+    def test_no_a2a_with_dp_attention_ok(self):
+        # DP TBO path is valid: --enable-dp-attention + --enable-two-batch-overlap
+        # with a2a backend 'none' must NOT raise (no SGLANG_ENABLE_DP_TBO needed).
+        args = self._args(enable_dp_attention=True)
+        args._check_two_batch_overlap()
+
+    def test_ep_a2a_backend_ok_without_dp_attention(self):
+        # EP a2a path (e.g. deepep) overlaps dispatch/combine; the guard does not
+        # require dp-attention there.
+        args = self._args(moe_a2a_backend="deepep", enable_dp_attention=False)
+        args._check_two_batch_overlap()
+
+    def test_tbo_disabled_is_noop(self):
+        args = self._args(enable_two_batch_overlap=False, enable_dp_attention=False)
+        args._check_two_batch_overlap()
+
+
 if __name__ == "__main__":
     unittest.main()