[Spec][LoRA] Support multi-adapter LoRA with EAGLE/NEXTN/DFLASH/DSPARK speculative decoding (#34337)

python/sglang/srt/lora/backend/base_backend.py

@@ -5,7 +5,11 @@ import triton
 import triton.language as tl
 
 from sglang.srt.lora.backend.lmhead_mixing import LoRABackendLmHeadMixing
-from sglang.srt.lora.utils import LoRABatchInfo, MoELoRABatchInfo
+from sglang.srt.lora.utils import (
+    LoRABatchInfo,
+    MoELoRABatchInfo,
+    get_batch_token_counts,
+)
 from sglang.srt.model_executor.forward_batch_info import ForwardBatch
 
 
@@ -296,16 +300,7 @@ class BaseLoRABackend(LoRABackendLmHeadMixing):
             adapter_enabled = None
             token_lora_mapping = None
 
-        num_tokens = (
+        num_tokens, max_len = get_batch_token_counts(forward_batch)
-            sum(forward_batch.extend_seq_lens_cpu)
-            if forward_batch.forward_mode.is_extend()
-            else forward_batch.batch_size
-        )
-        max_len = (
-            max(forward_batch.extend_seq_lens_cpu)
-            if forward_batch.forward_mode.is_extend()
-            else 1
-        )
 
         if (
             batch_info.req_seg_indptr is not None

python/sglang/srt/lora/backend/chunked_backend.py

@@ -12,6 +12,7 @@ from sglang.srt.lora.backend.base_backend import BaseLoRABackend
 from sglang.srt.lora.utils import (
     LoRABatchInfo,
     generate_sequence_lengths,
+    get_batch_token_counts,
     get_lm_head_pruned_lens,
     merge_and_chunk_segments,
 )
@@ -184,11 +185,7 @@ class ChunkedSgmvLoRABackend(BaseLoRABackend):
         Returns:
             The determined chunk size
         """
-        num_tokens = (
+        num_tokens, _ = get_batch_token_counts(forward_batch)
-            forward_batch.extend_num_tokens
-            if forward_batch.forward_mode.is_extend()
-            else forward_batch.batch_size
-        )
         return self._determine_chunk_size_for_tokens(num_tokens)
 
     def _determine_chunk_size_for_tokens(self, num_tokens: int) -> int:

python/sglang/srt/lora/backend/triton_backend.py

@@ -11,6 +11,8 @@ from sglang.kernels.ops.gemm.sgemm_lora_b import sgemm_lora_b_fwd
 from sglang.srt.lora.backend.base_backend import BaseLoRABackend
 from sglang.srt.lora.utils import (
     LoRABatchInfo,
+    generate_sequence_lengths,
+    get_batch_token_counts,
     get_lm_head_pruned_lens,
     merge_and_chunk_segments,
 )
@@ -289,6 +291,15 @@ class TritonLoRABackend(BaseLoRABackend):
                 self.cuda_graph_batch_info is not None
             ), "CUDA Graph batch info is not initialized."
             batch_info = self.cuda_graph_batch_info
+            if forward_batch.forward_mode.is_target_verify():
+                # seg_lens were pre-filled at the captured per-request width
+                # (stored as max_len); another width would silently
+                # mis-segment adapters onto the wrong token rows.
+                assert forward_batch.spec_info.draft_token_num == batch_info.max_len, (
+                    "target-verify width "
+                    f"{forward_batch.spec_info.draft_token_num} does not match "
+                    f"the captured LoRA cuda-graph width {batch_info.max_len}"
+                )
             batch_info.bs = forward_batch.batch_size
             batch_info.num_segments = forward_batch.batch_size
         elif use_prefill_cuda_graph:
@@ -303,17 +314,9 @@ class TritonLoRABackend(BaseLoRABackend):
             batch_info.seg_lens[bs:].zero_()
             torch.cumsum(batch_info.seg_lens, dim=0, out=batch_info.seg_indptr[1:])
         else:
-            max_len = (
+            # max_len comes from the CPU-side counts to avoid a D2H transfer.
-                # Calculate max_len from the CPU copy to avoid D2H transfer.
+            _, max_len = get_batch_token_counts(forward_batch)
-                max(forward_batch.extend_seq_lens_cpu)
+            seg_lens = generate_sequence_lengths(forward_batch, device=self.device)
-                if forward_batch.forward_mode.is_extend()
-                else 1
-            )
-            seg_lens = (
-                forward_batch.extend_seq_lens
-                if forward_batch.forward_mode.is_extend()
-                else torch.ones(bs, dtype=torch.int32, device=self.device)
-            )
             seg_indptr = torch.zeros((bs + 1,), dtype=torch.int32, device=self.device)
             seg_indptr[1:] = torch.cumsum(seg_lens, dim=0)
 

python/sglang/srt/lora/layers.py

@@ -31,6 +31,11 @@ from sglang.srt.runtime_context import get_parallel
 _SGLANG_EXPERIMENTAL_LORA_OPTI = envs.SGLANG_EXPERIMENTAL_LORA_OPTI.get()
 
 
+def unwrap_lora_layer(module: nn.Module) -> nn.Module:
+    """Return the plain module behind a LoRA wrapper, or the module itself."""
+    return module.base_layer if isinstance(module, BaseLayerWithLoRA) else module
+
+
 class BaseLayerWithLoRA(nn.Module):
     def __init__(
         self,

python/sglang/srt/lora/lora_manager.py

@@ -43,6 +43,7 @@ from sglang.srt.lora.utils import (
     auto_detect_lora_target_modules,
     get_normalized_target_modules,
     get_target_module_name,
+    warn_if_adapter_targets_embeddings,
 )
 from sglang.srt.managers.io_struct import LoRAUpdateOutput
 from sglang.srt.model_executor.forward_batch_info import ForwardBatch
@@ -50,6 +51,7 @@ from sglang.srt.runtime_context import (
     get_exec,
     get_lora,
     get_parallel,
+    get_spec,
 )
 from sglang.srt.server_args import ServerArgs
 from sglang.srt.utils import get_available_gpu_memory, replace_submodule
@@ -105,6 +107,7 @@ class LoRAManager:
         self.lora_strict_loading: bool = getattr(
             server_args, "lora_strict_loading", False
         )
+        self.speculative_algorithm: Optional[str] = get_spec().speculative_algorithm
 
         # LoRA backend for running sgemm kernels
         logger.info(f"Using {lora_backend} as backend of LoRA kernels.")
@@ -782,6 +785,12 @@ class LoRAManager:
         )
         lora_adapter.initialize_weights()
 
+        warn_if_adapter_targets_embeddings(
+            lora_name=lora_ref.lora_name,
+            embedding_layer_names=lora_adapter.embedding_layers.keys(),
+            speculative_algorithm=self.speculative_algorithm,
+        )
+
         self.loras[lora_ref.lora_id] = lora_adapter
 
     def load_lora_weights_from_tensors(
@@ -799,6 +808,12 @@ class LoRAManager:
             base_model=self.base_model,
         )
         lora_adapter.initialize_weights_from_tensors(tensors)
+
+        warn_if_adapter_targets_embeddings(
+            lora_name=lora_ref.lora_name,
+            embedding_layer_names=lora_adapter.embedding_layers.keys(),
+            speculative_algorithm=self.speculative_algorithm,
+        )
         self.loras[lora_ref.lora_id] = lora_adapter
 
     def load_lora_adapter_from_tensors(
@@ -1035,12 +1050,18 @@ def init_lora_cuda_graph_moe_buffers(
     from sglang.srt.lora.layers import FusedMoEWithLoRA
 
     max_bs = get_exec().graph.cuda_graph_config.decode.max_bs
+    # With spec on, the decode graph captures TARGET_VERIFY batches of
+    # num_draft_tokens per request, and the buffers below are per-token, so
+    # they must be sized in tokens rather than requests.
+    max_tokens = max_bs * (get_spec().speculative_num_draft_tokens or 1)
     max_loras = get_lora().max_loras_per_batch
     for module in model.modules():
         if isinstance(module, FusedMoEWithLoRA):
-            lora_manager.init_cuda_graph_moe_buffers(max_bs, max_loras, dtype, module)
+            lora_manager.init_cuda_graph_moe_buffers(
+                max_tokens, max_loras, dtype, module
+            )
             logger.info(
                 f"Pre-allocated shared MoE LoRA CUDA graph buffers "
-                f"(max_bs={max_bs}, max_loras={max_loras})"
+                f"(max_tokens={max_tokens}, max_loras={max_loras})"
             )
             break

python/sglang/srt/lora/utils.py

@@ -1,3 +1,4 @@
+import logging
 from dataclasses import dataclass
 from enum import Enum
 from typing import Iterable, List, Optional, Set, Tuple, Union
@@ -7,6 +8,29 @@ import torch
 from sglang.srt.model_executor.forward_batch_info import ForwardBatch
 from sglang.srt.utils.hf_transformers_utils import AutoConfig
 
+logger = logging.getLogger(__name__)
+
+
+def warn_if_adapter_targets_embeddings(
+    lora_name: str,
+    embedding_layer_names: Iterable[str],
+    speculative_algorithm: Optional[str],
+) -> None:
+    """Warn once when an adapter carries embedding weights under EAGLE spec."""
+    if speculative_algorithm not in ("EAGLE", "EAGLE3"):
+        return
+    modules = sorted(embedding_layer_names)
+    if not modules:
+        return
+    logger.warning(
+        "LoRA adapter '%s' targets embedding modules (%s) while EAGLE-family "
+        "speculative decoding is enabled. The shared draft consumes their "
+        "base weights, so those deltas do not influence drafting and may "
+        "reduce the accept rate. Outputs are unaffected.",
+        lora_name,
+        ", ".join(modules),
+    )
+
 
 @dataclass
 class MoELoRABatchInfo:
@@ -465,6 +489,19 @@ def get_lm_head_lora_b_shard_size(output_dim: int, shard_indices=None) -> int:
     return output_dim
 
 
+def get_batch_token_counts(forward_batch: ForwardBatch) -> Tuple[int, int]:
+    """(total tokens, max tokens per request) for LoRA segment math."""
+    mode = forward_batch.forward_mode
+    if mode.is_decode():
+        return forward_batch.batch_size, 1
+    if mode.is_target_verify():
+        num_tokens_per_req = forward_batch.spec_info.draft_token_num
+        return forward_batch.batch_size * num_tokens_per_req, num_tokens_per_req
+    if mode.is_extend():
+        return forward_batch.extend_num_tokens, max(forward_batch.extend_seq_lens_cpu)
+    raise ValueError(f"Unsupported forward mode: {mode}")
+
+
 def generate_sequence_lengths(
     forward_batch: ForwardBatch, device: Optional[torch.device] = None
 ) -> torch.Tensor:

python/sglang/srt/model_executor/forward_batch_info.py

@@ -845,7 +845,7 @@ class ForwardBatch(ForwardBatchDeepSeekMHAMixin):
 
         if ret.forward_mode.is_idle():
             ret.positions = torch.empty((0,), dtype=torch.int64, device=device)
-            if model_runner.server_args.enable_lora:
+            if model_runner.lora_manager is not None:
                 model_runner.lora_manager.reset_lora_batch()
             return ret
 
@@ -919,8 +919,8 @@ class ForwardBatch(ForwardBatchDeepSeekMHAMixin):
             else:
                 ret._compute_mrope_positions(model_runner, batch)
 
-        # Init lora information
+        # Init lora information (None on a draft runner: it is unadapted)
-        if model_runner.server_args.enable_lora:
+        if model_runner.lora_manager is not None:
             # In the non-LoRA overlap loading case, we fetch LoRA adapters into the memory pool
             # as a batch, right before running the batch
             if not model_runner.server_args.enable_lora_overlap_loading:

python/sglang/srt/model_executor/model_runner.py

@@ -319,6 +319,9 @@ class ModelRunner:
         # earlier publish.
         if not is_draft_worker:
             set_global_server_args_for_scheduler(server_args)
+        # Set by maybe_init_lora_manager; stays None when LoRA is off and on
+        # draft runners, which serve adapters' target model unadapted.
+        self.lora_manager: Optional[LoRAManager] = None
         self.draft_attention_backend = resolve_draft_attention_backend(
             draft_attention_backend=draft_attention_backend,
             server_args=server_args,
@@ -751,7 +754,8 @@ class ModelRunner:
             self.apply_torch_tp()
 
     def maybe_init_lora_manager(self):
-        if get_lora().enable_lora:
+        # Adapters apply to the target model only; the draft runs unadapted.
+        if get_lora().enable_lora and not self.is_draft_worker:
             self.init_lora_manager()
 
     def maybe_enable_batch_invariant_mode(self):

python/sglang/srt/model_executor/model_runner_components/cuda_graph_setup.py

@@ -271,7 +271,7 @@ def capture_prefill_graph(
         return result(eager_runner)
 
     if (
-        model_runner.server_args.enable_lora
+        model_runner.lora_manager is not None
         and not model_runner.lora_manager.supports_prefill_cuda_graph
     ):
         logger.warning(

python/sglang/srt/model_executor/runner/base_runner.py

@@ -574,7 +574,7 @@ class BaseRunner(ABC):
             )
 
         # Optional LoRA metadata.
-        if mr.server_args.enable_lora:
+        if mr.lora_manager is not None:
             lora_ids = [None] * batch_size
         else:
             lora_ids = None

python/sglang/srt/model_executor/runner/decode_cuda_graph_runner.py

@@ -348,7 +348,7 @@ class DecodeCudaGraphRunner(BaseCudaGraphRunner):
         self._captured_ragged_layouts: dict[int, object] = {}
         if self.ragged_verify_mode and (
             self.enable_two_batch_overlap
-            or model_runner.server_args.enable_lora
+            or model_runner.lora_manager is not None
             or self.disable_padding
         ):
             raise ValueError(
@@ -381,7 +381,7 @@ class DecodeCudaGraphRunner(BaseCudaGraphRunner):
         if self.enable_torch_compile:
             set_torch_compile_config()
 
-        if self.model_runner.server_args.enable_lora:
+        if self.model_runner.lora_manager is not None:
             # Phase 2 of LoRA CUDA graph init: dense LoRA batch metadata.
             # Phase 1 (MoE buffers) was handled earlier in ModelRunner via
             # lora_manager.init_cuda_graph_moe_buffers().
@@ -927,7 +927,7 @@ class DecodeCudaGraphRunner(BaseCudaGraphRunner):
             spec_info,
         )
 
-        if self.model_runner.server_args.enable_lora:
+        if self.model_runner.lora_manager is not None:
             # It is safe to capture CUDA graph using empty LoRA id, as the LoRA kernels will always be launched whenever
             # `--enable-lora` is set to True (and return immediately if the LoRA id is empty for perf optimization).
             lora_ids = [None] * bs

python/sglang/srt/model_executor/runner/prefill_cuda_graph_runner.py

@@ -256,7 +256,7 @@ class PrefillCudaGraphRunner(BaseCudaGraphRunner):
         # --- model flags ----------------------------------------------
         self.quant_config = getattr(model_runner.model, "quant_config", None)
         self.is_multimodal = model_runner.model_config.is_multimodal
-        self.enable_lora = model_runner.server_args.enable_lora
+        self.enable_lora = model_runner.lora_manager is not None
         # Classification/reward forwards branch on return_pooled_hidden_states;
         # capture must use the same flag value as replay for those models.
         self.capture_return_pooled_hidden_states = not model_runner.is_generation

python/sglang/srt/server_args.py

@@ -319,6 +319,10 @@ RETRACTION_POLICY_CHOICES = ["length", "priority"]
 
 RL_ON_POLICY_TARGET_CHOICES = ["fsdp"]
 
+# Speculative algorithms whose verify forward presents a uniform per-request
+# token width, which is what the LoRA segment layout assumes.
+_LORA_SPEC_ALGORITHMS = ("EAGLE", "EAGLE3", "DFLASH", "DSPARK")
+
 LORA_BACKEND_CHOICES = ["triton", "csgmv", "ascend", "torch_native"]
 
 ENCODER_TRANSFER_BACKEND_CHOICES = [
@@ -9451,10 +9455,7 @@ class ServerArgs:
                 )
 
             # Validate compatibility with speculative decoding
-            if self.speculative_algorithm not in ["NGRAM", None]:
+            self._check_lora_speculative_compatibility()
-                raise ValueError(
-                    "Currently LoRA is only compatible with NGRAM speculative decoding."
-                )
 
             # Parse lora_paths
             if isinstance(self.lora_paths, list):
@@ -9559,6 +9560,65 @@ class ServerArgs:
                 self.lora_drain_wait_threshold >= 0.0
             ), "--lora-drain-wait-threshold must be non-negative."
 
+    def _check_lora_speculative_compatibility(self):
+        """Validate LoRA + speculative decoding combinations.
+
+        Adapters apply to the target only; a shared draft runs unadapted.
+        Matches resolved algorithm names (NEXTN has collapsed to EAGLE).
+        """
+        if self.speculative_algorithm in ["NGRAM", None]:
+            return
+
+        if self.speculative_algorithm not in _LORA_SPEC_ALGORITHMS:
+            promoted = (
+                " (NEXTN/EAGLE with a Gemma4 assistant draft is automatically "
+                "promoted to FROZEN_KV_MTP, which does not support LoRA)"
+                if self.speculative_algorithm == "FROZEN_KV_MTP"
+                else ""
+            )
+            raise ValueError(
+                "LoRA is only compatible with NGRAM, EAGLE, NEXTN, EAGLE3, "
+                "DFLASH, or DSPARK speculative decoding, not "
+                f"{self.speculative_algorithm}{promoted}."
+            )
+
+        ragged_mode = envs.SGLANG_RAGGED_VERIFY_MODE.get()
+
+        # Each entry: (is unsupported, why). Reasons are appended to a shared
+        # prefix so the message names the combination, not just the flag.
+        unsupported = [
+            (
+                self.speculative_algorithm == "DSPARK" and ragged_mode != "static",
+                f"does not support SGLANG_RAGGED_VERIFY_MODE={ragged_mode!r}: "
+                "the per-request verify lengths it schedules break the "
+                "uniform-width LoRA segment layout",
+            ),
+            (
+                self.speculative_adaptive,
+                "does not support --speculative-adaptive: the draft is built "
+                "from a static ServerArgs snapshot, and the runtime-state "
+                "swap does not rebuild LoRA cuda-graph metadata",
+            ),
+            (
+                "experimental_sgl_trtllm"
+                in (self.moe_runner_backend, self.speculative_moe_runner_backend),
+                "does not support the experimental_sgl_trtllm MoE runner: its "
+                "TopK reads the LoRA config per forward, which the draft "
+                "resolves against the target's after its own publish ended",
+            ),
+            (
+                envs.SGLANG_ENABLE_OVERLAP_PLAN_STREAM.get(),
+                "does not support SGLANG_ENABLE_OVERLAP_PLAN_STREAM=1: LoRA "
+                "batch preparation would run on the plan stream, unordered "
+                "against in-flight forwards",
+            ),
+        ]
+        for is_unsupported, reason in unsupported:
+            if is_unsupported:
+                raise ValueError(
+                    f"LoRA with EAGLE/NEXTN/EAGLE3 speculative decoding {reason}."
+                )
+
     def validate_buckets_rule(self, arg_name: str, buckets_rule: List[str]):
         if not buckets_rule:
             return

python/sglang/srt/speculative/dflash_worker_v2.py

@@ -22,6 +22,7 @@ from sglang.srt.distributed.parallel_state_wrapper import ParallelState
 from sglang.srt.environ import envs
 from sglang.srt.layers.logits_processor import should_apply_lm_head_quant_method
 from sglang.srt.layers.logprob_processor import compute_spec_logprobs
+from sglang.srt.lora.layers import unwrap_lora_layer
 from sglang.srt.managers.schedule_batch import ScheduleBatch
 from sglang.srt.managers.scheduler import GenerationBatchResult
 from sglang.srt.managers.tp_worker import TpModelWorker
@@ -480,7 +481,7 @@ class DFlashWorkerV2(BaseSpecWorker):
         if self.block_size <= 1:
             return _eager("block_size<=1")
         target_model = self._target_worker.model_runner.model
-        lm_head = getattr(target_model, "lm_head", None)
+        lm_head = unwrap_lora_layer(getattr(target_model, "lm_head", None))
         if lm_head is None:
             return _eager("no target lm_head")
 
@@ -1749,8 +1750,8 @@ class DFlashWorkerV2(BaseSpecWorker):
 
         # --- 1) Draft a fixed block with the draft model.
         target_model = self.target_worker.model_runner.model
-        embed_module = target_model.get_input_embeddings()
+        embed_module = unwrap_lora_layer(target_model.get_input_embeddings())
-        lm_head = getattr(target_model, "lm_head", None)
+        lm_head = unwrap_lora_layer(getattr(target_model, "lm_head", None))
         if lm_head is None or not (
             hasattr(lm_head, "weight")
             or callable(getattr(getattr(lm_head, "quant_method", None), "apply", None))

python/sglang/srt/speculative/dspark_components/dspark_draft.py

@@ -11,6 +11,7 @@ from sglang.kernels.ops.speculative.dspark.dspark_draft_model import (
     SampleStepTokens,
 )
 from sglang.srt.environ import envs
+from sglang.srt.lora.layers import unwrap_lora_layer
 from sglang.srt.managers.schedule_batch import ScheduleBatch
 from sglang.srt.model_executor.forward_batch_info import (
     CaptureHiddenMode,
@@ -201,7 +202,7 @@ class DraftBlockProposer:
         target_model,
         sampling_info,
     ) -> DraftProposal:
-        embed_module = target_model.get_input_embeddings()
+        embed_module = unwrap_lora_layer(target_model.get_input_embeddings())
         draft_sampler = self._draft_sampler
         all_greedy = sampling_info is None or sampling_info.is_all_greedy
         fwd = self._run_forward(

python/sglang/srt/speculative/dspark_components/dspark_worker_v2.py

@@ -12,6 +12,7 @@ from sglang.srt.configs.hybrid_arch import mambaish_config
 from sglang.srt.distributed.parallel_state_wrapper import ParallelState
 from sglang.srt.environ import envs
 from sglang.srt.layers.logprob_processor import compute_spec_logprobs
+from sglang.srt.lora.layers import unwrap_lora_layer
 from sglang.srt.managers.schedule_batch import ScheduleBatch
 from sglang.srt.managers.scheduler import GenerationBatchResult
 from sglang.srt.managers.tp_worker import TpModelWorker
@@ -190,13 +191,15 @@ class DSparkWorkerV2(BaseSpecWorker):
                 )
         else:
             target_model = self.target_worker.model_runner.model
-            lm_head = getattr(target_model, "lm_head", None)
+            lm_head = unwrap_lora_layer(getattr(target_model, "lm_head", None))
             if lm_head is None or not hasattr(lm_head, "weight"):
                 raise RuntimeError(
                     "DSpark requires the target model to expose `lm_head` with `weight`."
                 )
             self.draft_model.attach_shared_modules(
-                embed_tokens=self._resolve_target_embed_tokens(target_model),
+                embed_tokens=unwrap_lora_layer(
+                    self._resolve_target_embed_tokens(target_model)
+                ),
                 lm_head=lm_head,
             )
 

python/sglang/srt/speculative/eagle_worker_v2.py

@@ -278,8 +278,12 @@ class EagleDraftWorker(EagleDraftWorkerBase):
             self.hot_token_id = None
 
     def init_lm_head(self):
+        from sglang.srt.lora.layers import unwrap_lora_layer
+
         embed, head = self.target_worker.model_runner.model.get_embed_and_head()
-        target_lm_head = getattr(self.target_worker.model_runner.model, "lm_head", None)
+        target_lm_head = unwrap_lora_layer(
+            getattr(self.target_worker.model_runner.model, "lm_head", None)
+        )
 
         def maybe_share_target_lm_head():
             if (

test/manual/lora/check_spec_baseline_divergence.py

@@ -0,0 +1,125 @@
+"""Does a spec-on vs spec-off divergence need LoRA at all?
+
+Run this when the spec+LoRA harness
+(``test/manual/lora/run_spec_lora_matrix.py``) reports a mismatch that
+survives its filters. It runs the *same* speculative config with **no
+adapters loaded**, comparing spec-off against spec-on greedy outputs and
+sampling each side twice so run-to-run instability is visible.
+
+If the base model diverges on the same prompt, the cause is the model and
+the speculative path (EAGLE3 topk>1 tree verify in particular), not the LoRA
+integration -- which is exactly what it showed for
+Qwen3-30B-A3B-Instruct-2507 on prompt #2: DIFFERS, and UNSTABLE-self, with
+zero adapters involved.
+
+The harness's own filters cannot answer this: they can tell whether a pair
+reproduces within one server config, but not whether the divergence depends
+on LoRA being present. That needs this second config.
+
+Usage (from a checkout, with a GPU):
+    python test/manual/lora/check_spec_baseline_divergence.py
+"""
+
+import os
+import subprocess
+import sys
+import time
+
+import requests
+
+PROMPTS = [
+    "What is the capital of France? Answer in one sentence.",
+    "List three primary colors.",
+    "Write a one-sentence story about a brave detective on Mars.",
+    "Explain what a hash table is in two sentences.",
+]
+BASE = "http://127.0.0.1:31000"
+COMMON = [
+    "--tp",
+    "4",
+    "--moe-runner-backend",
+    "triton",
+    "--attention-backend",
+    "flashinfer",
+    "--prefill-attention-backend",
+    "fa4",
+    "--decode-attention-backend",
+    "fa4",
+    "--mem-fraction-static",
+    "0.8",
+]
+SPEC = [
+    "--speculative-algorithm",
+    "EAGLE3",
+    "--speculative-draft-model-path",
+    "lmsys/SGLang-EAGLE3-Qwen3-30B-A3B-Instruct-2507-SpecForge-Nex",
+    "--speculative-num-steps",
+    "3",
+    "--speculative-eagle-topk",
+    "4",
+    "--speculative-num-draft-tokens",
+    "8",
+]
+
+
+def launch(extra):
+    env = dict(os.environ, SGLANG_ALLOW_OVERWRITE_LONGER_CONTEXT_LEN="1")
+    p = subprocess.Popen(
+        [
+            sys.executable,
+            "-m",
+            "sglang.launch_server",
+            "--model-path",
+            "Qwen/Qwen3-30B-A3B-Instruct-2507",
+            "--port",
+            "31000",
+        ]
+        + COMMON
+        + extra,
+        stdout=open("/scratch/loraspec/logs/attrib_server.log", "a"),
+        stderr=subprocess.STDOUT,
+        env=env,
+    )
+    for _ in range(120):
+        time.sleep(10)
+        try:
+            if requests.get(BASE + "/health", timeout=3).ok:
+                return p
+        except Exception:
+            pass
+    raise SystemExit("server did not come up")
+
+
+def gen():
+    r = requests.post(
+        BASE + "/generate",
+        json={
+            "text": PROMPTS,
+            "sampling_params": {"temperature": 0, "max_new_tokens": 32},
+        },
+        timeout=900,
+    )
+    r.raise_for_status()
+    return [x["text"] for x in r.json()]
+
+
+results = {}
+for label, extra in [("nospec", []), ("spec", SPEC)]:
+    p = launch(extra)
+    try:
+        results[label] = [gen(), gen()]
+    finally:
+        p.terminate()
+        p.wait(timeout=120)
+    time.sleep(10)
+
+print("=" * 70)
+for i, prompt in enumerate(PROMPTS):
+    a1, a2 = results["nospec"][0][i], results["nospec"][1][i]
+    b1, b2 = results["spec"][0][i], results["spec"][1][i]
+    stable = "stable" if (a1 == a2 and b1 == b2) else "UNSTABLE-self"
+    verdict = "same" if a1 == b1 else "DIFFERS"
+    print(f"prompt#{i}: nospec-vs-spec={verdict} ({stable})")
+    if a1 != b1:
+        print(f"   nospec: {a1!r}")
+        print(f"   spec  : {b1!r}")

test/manual/lora/run_spec_lora_matrix.py

@@ -0,0 +1,876 @@
+"""Manual validation harness: multi-adapter LoRA + EAGLE-family speculative decoding.
+
+The oracle is spec-on vs spec-off *per adapter*, not adapter vs base.
+Speculative decoding is lossless with respect to the target it verifies
+against, so for greedy sampling:
+
+    output(adapter=X, spec=ON) == output(adapter=X, spec=OFF)
+
+Comparing an adapter's output to the base model's only proves LoRA was
+applied at all. This harness launches the same weights twice (reference
+without spec, then with spec) and runs four checks:
+
+  1. parity   — per adapter, spec-on output == spec-off output (the oracle)
+  2. distinct — each adapter's output differs from base (LoRA really applied)
+  3. mixed    — a batch interleaving every adapter matches the solo outputs
+                (crossed verify segments serve a request the wrong adapter)
+  4. eager    — a batch wider than --cuda-graph-max-bs still matches
+                (exercises the non-cuda-graph target-verify path)
+
+It also reports per-adapter accept length from each response's
+meta_info["spec_accept_length"], which is how much speculation the shared
+unadapted draft actually buys for that adapter.
+
+Usage:
+    python test/manual/lora/run_spec_lora_matrix.py --config eagle3-llama31
+    python test/manual/lora/run_spec_lora_matrix.py --config nextn-qwen35-35b-a3b
+    python test/manual/lora/run_spec_lora_matrix.py --list
+
+Add --keep-derived to reuse a previously written derived adapter, and
+--max-new-tokens / --port to adjust the run.
+"""
+
+import argparse
+import hashlib
+import json
+import os
+import random
+import shutil
+import sys
+import time
+from concurrent import futures
+
+import requests
+
+from sglang.srt.utils import kill_process_tree
+from sglang.test.test_utils import (
+    DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
+    popen_launch_server,
+)
+
+PROMPTS = [
+    "What is the capital of France? Answer in one sentence.",
+    "List three primary colors.",
+    "Write a one-sentence story about a brave detective on Mars.",
+    "Explain what a hash table is in two sentences.",
+]
+
+DERIVED_SUFFIX = "-derived"
+
+
+# Each config is a runnable server shape. `adapters` are (name, hf_path)
+# pairs; `derive_from` names an adapter to synthesize a second, distinct
+# adapter from when the base has only one public adapter (needed to make
+# mixed-adapter batches meaningful).
+CONFIGS = {
+    # Cheapest: 5 genuinely distinct public adapters, ranks 8-64, no synthesis.
+    "eagle3-llama31": dict(
+        model="meta-llama/Llama-3.1-8B-Instruct",
+        spec_args=[
+            "--speculative-algorithm=EAGLE3",
+            "--speculative-draft-model-path=lmsys/sglang-EAGLE3-LLaMA3.1-Instruct-8B",
+            "--speculative-num-steps=5",
+            "--speculative-eagle-topk=8",
+            "--speculative-num-draft-tokens=32",
+        ],
+        adapters=[
+            ("fact", "algoprog/fact-generation-llama-3.1-8b-instruct-lora"),
+            ("guard", "nvidia/llama-3.1-nemoguard-8b-topic-control"),
+            ("sql", "philschmid/code-llama-3-1-8b-text-to-sql-lora"),
+            ("ocr", "pbevan11/llama-3.1-8b-ocr-correction"),
+            ("zh", "faridlazuarda/valadapt-llama-3.1-8B-it-chinese"),
+        ],
+        common_args=["--mem-fraction-static=0.7", "--max-lora-rank=64"],
+        tp=1,
+    ),
+    # EAGLE topk=1 is the same chain-shaped drafting NEXTN/MTP uses, on 1 GPU
+    # without needing an MTP checkpoint. cuda-graph-max-bs forces the eager path.
+    "eagle-topk1-llama2": dict(
+        model="meta-llama/Llama-2-7b-chat-hf",
+        spec_args=[
+            "--speculative-algorithm=EAGLE",
+            "--speculative-draft-model-path=lmsys/sglang-EAGLE-llama2-chat-7B",
+            "--speculative-num-steps=3",
+            "--speculative-eagle-topk=1",
+            "--speculative-num-draft-tokens=4",
+        ],
+        adapters=[("norwegian", "RuterNorway/Llama-2-7b-chat-norwegian-LoRa")],
+        derive_from="norwegian",
+        common_args=[
+            "--mem-fraction-static=0.7",
+            "--max-lora-rank=128",
+            "--cuda-graph-max-bs=2",
+        ],
+        tp=1,
+    ),
+    # Real NEXTN (self-bundled MTP head, no draft path) on a MoE base: the
+    # densest coverage per GPU-hour — MoE-LoRA cuda-graph buffers, virtual
+    # experts, and an arch whose MTP head shares the target lm_head module.
+    "nextn-qwen35-35b-a3b": dict(
+        model="Qwen/Qwen3.5-35B-A3B",
+        spec_args=[
+            "--speculative-algorithm=NEXTN",
+            "--speculative-num-steps=3",
+            "--speculative-eagle-topk=1",
+            "--speculative-num-draft-tokens=4",
+        ],
+        adapters=[("case", "opherlie/lora-test-case-Qwen3.5-35B-A3B", "dataset")],
+        derive_from="case",
+        common_args=[
+            "--max-lora-rank=64",
+            "--moe-runner-backend=triton",
+            "--experts-shared-outer-loras",
+            "--lora-use-virtual-experts",
+            "--disable-shared-experts-fusion",
+            "--mem-fraction-static=0.8",
+        ],
+        tp=4,
+    ),
+    # MoE + EAGLE3 with a draft checkpoint matched to the same base variant.
+    "eagle3-qwen3-30b-a3b": dict(
+        model="Qwen/Qwen3-30B-A3B-Instruct-2507",
+        spec_args=[
+            "--speculative-algorithm=EAGLE3",
+            "--speculative-draft-model-path=lmsys/SGLang-EAGLE3-Qwen3-30B-A3B-Instruct-2507-SpecForge-Nex",
+            "--speculative-num-steps=3",
+            "--speculative-eagle-topk=4",
+            "--speculative-num-draft-tokens=8",
+        ],
+        adapters=[
+            ("case", "yushengsu/lora-diff-Qwen3-30B-A3B-Instruct-2507", "dataset")
+        ],
+        derive_from="case",
+        common_args=[
+            "--max-lora-rank=32",
+            "--moe-runner-backend=triton",
+            "--experts-shared-outer-loras",
+            "--attention-backend=flashinfer",
+            "--prefill-attention-backend=fa4",
+            "--decode-attention-backend=fa4",
+            "--mem-fraction-static=0.8",
+        ],
+        # The draft checkpoint's config derives a 2048 context; the draft
+        # follows the target's context_length (it reads target KV), so the
+        # longer-context guard has to be waived for this pairing.
+        env={"SGLANG_ALLOW_OVERWRITE_LONGER_CONTEXT_LEN": "1"},
+        tp=4,
+    ),
+    # DFLASH: fixed-size block drafting, verified in one TARGET_VERIFY pass.
+    # Its target is the one base with several genuinely distinct public
+    # adapters, so no synthesis is needed.
+    "dflash-llama31": dict(
+        model="meta-llama/Llama-3.1-8B-Instruct",
+        spec_args=[
+            "--speculative-algorithm=DFLASH",
+            "--speculative-draft-model-path=z-lab/LLaMA3.1-8B-Instruct-DFlash-UltraChat",
+            "--speculative-num-draft-tokens=4",
+        ],
+        adapters=[
+            ("fact", "algoprog/fact-generation-llama-3.1-8b-instruct-lora"),
+            ("guard", "nvidia/llama-3.1-nemoguard-8b-topic-control"),
+        ],
+        common_args=["--mem-fraction-static=0.7", "--max-lora-rank=64"],
+        # The draft checkpoint derives a 40960 context against the target's
+        # 131072; the draft follows the target, so waive the guard.
+        env={"SGLANG_ALLOW_OVERWRITE_LONGER_CONTEXT_LEN": "1"},
+        tp=1,
+    ),
+    # DSPARK with a separate DSpark draft head, on the one base that has two
+    # distinct public adapters. Only the default static ragged-verify mode is
+    # supported: the others schedule per-request verify lengths, which the
+    # uniform-width LoRA segment layout cannot express.
+    "dspark-inkling": dict(
+        model="thinkingmachines/Inkling-Small",
+        spec_args=[
+            "--speculative-algorithm=DSPARK",
+            "--speculative-draft-model-path=RadixArk/Inkling-Small-DSpark",
+            "--speculative-dspark-block-size=5",
+        ],
+        adapters=[
+            ("gutenberg", "nbeerbower/Inkling-Small-Gutenberg-DPO-LoRA"),
+            ("hemlock", "hemlang/Inkling-Small-Hemlock-SFT-LoRA"),
+        ],
+        common_args=[
+            "--max-lora-rank=32",
+            "--moe-runner-backend=triton",
+            "--experts-shared-outer-loras",
+            "--mem-fraction-static=0.8",
+        ],
+        env={"SGLANG_ALLOW_OVERWRITE_LONGER_CONTEXT_LEN": "1"},
+        # A ~500GB checkpoint over network storage does not load inside the
+        # default launch budget.
+        launch_timeout=3600,
+        tp=8,
+    ),
+    # Flagship MLA + MoE NextN. 8 GPUs.
+    "nextn-deepseek-v31": dict(
+        model="deepseek-ai/DeepSeek-V3.1-Base",
+        spec_args=[
+            "--speculative-algorithm=NEXTN",
+            "--speculative-num-steps=3",
+            "--speculative-eagle-topk=1",
+            "--speculative-num-draft-tokens=4",
+        ],
+        adapters=[("case", "yushengsu/lora-diff-DeepSeek-V3.1-Base", "dataset")],
+        derive_from="case",
+        common_args=[
+            "--max-lora-rank=32",
+            "--moe-runner-backend=triton",
+            "--experts-shared-outer-loras",
+            "--attention-backend=flashinfer",
+            "--prefill-attention-backend=fa4",
+            "--decode-attention-backend=flashinfer",
+            "--disable-shared-experts-fusion",
+            "--mem-fraction-static=0.8",
+        ],
+        tp=8,
+    ),
+}
+
+
+def log(msg: str) -> None:
+    print(f"[harness] {msg}", flush=True)
+
+
+def materialize_adapter(hf_path: str, repo_type: str) -> str:
+    """Download an adapter and return its local directory.
+
+    Several adapters used here live in *dataset* repos (that is how the
+    repo's own LoRA logprob-diff tests host them), which the server cannot
+    resolve as a model id — so every adapter is materialized locally and
+    passed to --lora-paths by path.
+    """
+    from huggingface_hub import snapshot_download
+
+    return snapshot_download(repo_id=hf_path, repo_type=repo_type)
+
+
+def check_adapter_supported(name: str, local_path: str) -> None:
+    """Report what each adapter exercises. Nothing here is a rejection: a
+    draft sharing the target's lm_head gets the unwrapped base layer, so
+    lm_head and embedding adapters cost accept rate, not correctness."""
+    config_path = os.path.join(local_path, "adapter_config.json")
+    try:
+        with open(config_path) as f:
+            config = json.load(f)
+    except Exception as e:  # noqa: BLE001 - not every layout ships one
+        log(f"  {name}: could not read adapter_config.json ({e}); skipping precheck")
+        return
+    modules = config.get("target_modules")
+    log(f"  {name}: r={config.get('r')} target_modules={modules}")
+    if isinstance(modules, list):
+        shared = {"lm_head", "output", "unembed_tokens"} & set(modules)
+        if shared:
+            log(f"  {name}: targets {sorted(shared)} — shared-lm_head path")
+        if {"embed_tokens", "vocab_emb", "word_embeddings"} & set(modules):
+            log(f"  {name}: targets embeddings — expect a reduced accept rate")
+    if config.get("modules_to_save"):
+        log(f"  {name}: WARNING modules_to_save={config['modules_to_save']}")
+
+
+LM_HEAD_MARKERS = ("lm_head", "unembed_tokens")
+
+
+def adapter_lm_head_keys(local_path: str):
+    """Tensor keys that would land on lm_head (PEFT unembed_tokens keys are
+    rewritten to lm_head during load)."""
+    from safetensors import safe_open
+
+    weights = os.path.join(local_path, "adapter_model.safetensors")
+    if not os.path.isfile(weights):
+        return []
+    with safe_open(weights, "pt") as f:
+        return [k for k in f.keys() if any(m in k for m in LM_HEAD_MARKERS)]
+
+
+def write_adapter_variant(
+    source_dir: str, out_dir: str, keep: bool, *, negate_b: bool, drop_lm_head: bool
+) -> str:
+    """Write a modified copy of an adapter.
+
+    ``drop_lm_head`` removes output-layer tensors, isolating an adapter's
+    other modules from the shared-lm_head path. The server accepts lm_head
+    adapters, so this is for narrowing a failure, not a requirement.
+
+    ``negate_b`` flips the sign of every lora_B tensor, producing a second
+    adapter of identical shape whose outputs genuinely diverge from the
+    original — without which a "mixed-adapter" batch would compare an adapter
+    against itself and could not detect crossed verify segments.
+    """
+    if keep and os.path.isdir(out_dir):
+        log(f"reusing adapter variant at {out_dir}")
+        return out_dir
+
+    from safetensors.torch import load_file, save_file
+
+    weights_name = "adapter_model.safetensors"
+    src_weights = os.path.join(source_dir, weights_name)
+    if not os.path.isfile(src_weights):
+        raise SystemExit(f"{source_dir} has no {weights_name}")
+
+    if os.path.isdir(out_dir):
+        shutil.rmtree(out_dir)
+    os.makedirs(out_dir)
+
+    tensors = load_file(src_weights)
+    dropped = flipped = 0
+    out = {}
+    for key, value in tensors.items():
+        if drop_lm_head and any(m in key for m in LM_HEAD_MARKERS):
+            dropped += 1
+            continue
+        if negate_b and "lora_B" in key:
+            value = -value
+            flipped += 1
+        out[key] = value
+    save_file(out, os.path.join(out_dir, weights_name))
+    shutil.copy(
+        os.path.join(source_dir, "adapter_config.json"),
+        os.path.join(out_dir, "adapter_config.json"),
+    )
+    log(
+        f"wrote {out_dir} (dropped {dropped} lm_head tensors, "
+        f"negated {flipped} lora_B tensors)"
+    )
+    return out_dir
+
+
+def launch(config: dict, adapters, base_url: str, with_spec: bool):
+    other_args = list(config["common_args"])
+    env = config.get("env")
+    if config["tp"] > 1:
+        other_args += [f"--tp={config['tp']}"]
+    if adapters:
+        other_args += [
+            "--enable-lora",
+            f"--lora-backend={config.get('lora_backend', 'triton')}",
+            # +1: the base model occupies a pool slot too, and every mixed
+            # batch below co-batches base requests.
+            f"--max-loras-per-batch={len(adapters) + 1}",
+            "--lora-paths",
+        ] + [f"{name}={path}" for name, path in adapters]
+    else:
+        # Base arms: --max-lora-rank is a LoRA-only flag and is rejected
+        # without --enable-lora, so drop it from the common set.
+        other_args = [a for a in other_args if not a.startswith("--max-lora-rank")]
+    if with_spec:
+        other_args += config["spec_args"]
+    other_args += config.get("extra_args", [])
+    log(f"launching {'spec' if with_spec else 'reference'} server: {other_args}")
+    return popen_launch_server(
+        config["model"],
+        base_url,
+        timeout=config.get("launch_timeout", DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH),
+        other_args=other_args,
+        env=env,
+    )
+
+
+def generate(base_url: str, texts, routes, max_new_tokens: int):
+    """One /generate call; returns (texts, per-request accept lengths)."""
+    response = requests.post(
+        base_url + "/generate",
+        json={
+            "text": texts,
+            "lora_path": routes,
+            "sampling_params": {"temperature": 0, "max_new_tokens": max_new_tokens},
+        },
+        timeout=1800,
+    )
+    response.raise_for_status()
+    results = response.json()
+    outputs = [item["text"] for item in results]
+    accepts = [item["meta_info"].get("spec_accept_length") for item in results]
+    return outputs, accepts
+
+
+def min_logprob_gap(base_url: str, route, prompt: str, max_new_tokens: int):
+    """Smallest top-2 logprob gap along the greedy path for one request.
+
+    A gap of ~0 means the argmax at that position is decided by kernel scan
+    order, so any change in reduction order (a verify forward computes logits
+    at a different batch shape than a plain decode) flips the token with no
+    correctness implication. Used to classify surviving mismatches.
+    """
+    response = requests.post(
+        base_url + "/generate",
+        json={
+            "text": prompt,
+            "lora_path": route,
+            "sampling_params": {"temperature": 0, "max_new_tokens": max_new_tokens},
+            "return_logprob": True,
+            "top_logprobs_num": 2,
+        },
+        timeout=600,
+    )
+    response.raise_for_status()
+    tops = response.json()["meta_info"].get("output_top_logprobs") or []
+    gaps = [c[0][0] - c[1][0] for c in tops if c and len(c) >= 2]
+    return min(gaps) if gaps else None
+
+
+def collect_solo(base_url: str, routes, max_new_tokens: int):
+    """Per route: outputs and mean accept length over PROMPTS."""
+    solo, accept = {}, {}
+    for route in routes:
+        outputs, accepts = generate(
+            base_url, list(PROMPTS), [route] * len(PROMPTS), max_new_tokens
+        )
+        solo[route] = outputs
+        seen = [a for a in accepts if a]
+        accept[route] = sum(seen) / len(seen) if seen else None
+    return solo, accept
+
+
+def report_parity(label: str, reference: dict, actual: dict) -> int:
+    """Compare per-route output lists; returns the mismatch count."""
+    mismatches = 0
+    for route, expected in reference.items():
+        for i, (want, got) in enumerate(zip(expected, actual[route])):
+            if want != got:
+                mismatches += 1
+                log(f"  MISMATCH [{label}] route={route} prompt#{i}")
+                log(f"    spec-off: {want!r}")
+                log(f"    spec-on : {got!r}")
+    return mismatches
+
+
+def build_load(num_prompts: int, input_len: int, seed: int):
+    """Fixed synthetic prompts as raw token ids, so every arm sends identical
+    work and the input length is exact rather than tokenizer-dependent."""
+    rng = random.Random(seed)
+    return [
+        [rng.randint(1000, 10000) for _ in range(input_len)] for _ in range(num_prompts)
+    ]
+
+
+def one_request(base_url: str, input_ids, route, output_len: int):
+    started = time.perf_counter()
+    response = requests.post(
+        base_url + "/generate",
+        json={
+            "input_ids": input_ids,
+            "lora_path": route,
+            "sampling_params": {
+                "temperature": 0,
+                "max_new_tokens": output_len,
+                # Fixed-length output: every arm emits exactly output_len
+                # tokens, so throughput is comparable without length drift.
+                "ignore_eos": True,
+            },
+        },
+        timeout=3600,
+    )
+    response.raise_for_status()
+    meta = response.json()["meta_info"]
+    return dict(
+        latency=time.perf_counter() - started,
+        output_tokens=meta.get("completion_tokens", output_len),
+        accept_length=meta.get("spec_accept_length"),
+    )
+
+
+def measure(base_url: str, loads, routes, output_len: int, concurrency: int):
+    """Drive `concurrency` in-flight requests over the load; return throughput,
+    accept length, and per-request latency."""
+    pairs = [(loads[i], routes[i % len(routes)]) for i in range(len(loads))]
+    started = time.perf_counter()
+    with futures.ThreadPoolExecutor(max_workers=concurrency) as pool:
+        results = list(
+            pool.map(
+                lambda pair: one_request(base_url, pair[0], pair[1], output_len), pairs
+            )
+        )
+    elapsed = time.perf_counter() - started
+    accepts = [r["accept_length"] for r in results if r["accept_length"]]
+    total_out = sum(r["output_tokens"] for r in results)
+    latencies = sorted(r["latency"] for r in results)
+    return dict(
+        output_tps=total_out / elapsed,
+        accept_length=(sum(accepts) / len(accepts)) if accepts else None,
+        median_latency=latencies[len(latencies) // 2],
+        elapsed=elapsed,
+        requests=len(results),
+    )
+
+
+def run_perf(config: dict, args) -> int:
+    """Four arms answering two questions: does speculation still pay once LoRA
+    is on (lora_spec vs lora_nospec), and how much does serving adapters cost
+    relative to speculating on the plain base model (lora_spec vs base_spec)?
+    """
+    base_url = f"http://127.0.0.1:{args.port}"
+    adapters = resolve_adapters(config, args)
+    concurrencies = [int(c) for c in args.concurrency.split(",")]
+    loads = build_load(args.num_prompts, args.input_len, args.seed)
+    warmup = build_load(max(concurrencies), args.input_len, args.seed + 1)
+
+    # (label, serve LoRA?, speculate?)
+    arms = [
+        ("base_nospec", False, False),
+        ("base_spec", False, True),
+        ("lora_nospec", True, False),
+        ("lora_spec", True, True),
+    ]
+    table = {}
+
+    for label, with_lora, with_spec in arms:
+        log("=" * 68)
+        log(f"arm {label}: lora={with_lora} spec={with_spec}")
+        process = None
+        try:
+            process = launch(
+                config,
+                adapters if with_lora else [],
+                base_url,
+                with_spec=with_spec,
+            )
+            # Multi-adapter arms spread requests round-robin across every
+            # adapter (the multi-tenant shape); base arms send no adapter.
+            routes = [name for name, _ in adapters] if with_lora else [None]
+            measure(base_url, warmup, routes, args.output_len, len(warmup))
+            for concurrency in concurrencies:
+                stats = measure(base_url, loads, routes, args.output_len, concurrency)
+                table[(label, concurrency)] = stats
+                log(
+                    f"  c={concurrency:<4} {stats['output_tps']:8.1f} tok/s  "
+                    f"accept={stats['accept_length']}  "
+                    f"p50={stats['median_latency']:.2f}s"
+                )
+        finally:
+            if process is not None:
+                kill_process_tree(process.pid)
+
+    report_perf(table, concurrencies, args)
+    return 0
+
+
+def report_perf(table, concurrencies, args) -> None:
+    log("=" * 78)
+    log(
+        f"PERF  model-shape: {args.num_prompts} reqs x {args.input_len} in / "
+        f"{args.output_len} out"
+    )
+    log("=" * 78)
+    labels = ["base_nospec", "base_spec", "lora_nospec", "lora_spec"]
+    log(f"{'concurrency':<12}" + "".join(f"{label:>16}" for label in labels))
+    for concurrency in concurrencies:
+        cells = []
+        for label in labels:
+            stats = table.get((label, concurrency))
+            cells.append(f"{stats['output_tps']:.1f}" if stats else "-")
+        log(
+            f"{concurrency:<12}" + "".join(f"{cell:>16}" for cell in cells) + "   tok/s"
+        )
+    log("")
+    log(f"{'concurrency':<12}{'base accept':>16}{'lora accept':>16}")
+    for concurrency in concurrencies:
+        base = table.get(("base_spec", concurrency), {}).get("accept_length")
+        lora = table.get(("lora_spec", concurrency), {}).get("accept_length")
+        fmt = lambda v: f"{v:.3f}" if v else "-"  # noqa: E731
+        log(f"{concurrency:<12}{fmt(base):>16}{fmt(lora):>16}")
+    log("")
+    log("ratios (>1 is better)")
+    log(
+        f"{'concurrency':<12}{'spec on base':>16}{'spec on lora':>16}"
+        f"{'lora vs base':>16}"
+    )
+    for concurrency in concurrencies:
+
+        def tps(label):
+            stats = table.get((label, concurrency))
+            return stats["output_tps"] if stats else None
+
+        base_nospec, base_spec = tps("base_nospec"), tps("base_spec")
+        lora_nospec, lora_spec = tps("lora_nospec"), tps("lora_spec")
+        ratio = lambda a, b: f"{a / b:.2f}x" if a and b else "-"  # noqa: E731
+        log(
+            f"{concurrency:<12}"
+            f"{ratio(base_spec, base_nospec):>16}"
+            f"{ratio(lora_spec, lora_nospec):>16}"
+            f"{ratio(lora_spec, base_spec):>16}"
+        )
+    log("")
+    log("  spec on base  = speculation speedup without adapters (the ceiling)")
+    log("  spec on lora  = speculation speedup with adapters served (the ask)")
+    log("  lora vs base  = cost of serving adapters, both speculating")
+
+
+def resolve_adapters(config: dict, args):
+    """Materialize every adapter locally and return (name, local_path) pairs,
+    deriving a second distinct adapter when the base has only one public one.
+
+    Config entries are (name, hf_path) or (name, hf_path, repo_type).
+    """
+    adapters = []
+    for entry in config["adapters"]:
+        name, hf_path = entry[0], entry[1]
+        repo_type = entry[2] if len(entry) > 2 else "model"
+        local_path = materialize_adapter(hf_path, repo_type)
+
+        # A draft sharing the target's lm_head gets the unwrapped base layer,
+        # so these adapters cost accept rate, not correctness. Keep the
+        # weights as published so the run exercises that path.
+        lm_head_keys = adapter_lm_head_keys(local_path)
+        if lm_head_keys:
+            log(
+                f"  {name}: carries {len(lm_head_keys)} lm_head tensor(s) "
+                f"({lm_head_keys[0]}) — exercising the shared-lm_head path"
+            )
+        adapters.append((name, local_path))
+
+    log(f"prechecking {len(adapters)} adapter(s) against the lm_head rule")
+    for name, local_path in adapters:
+        check_adapter_supported(name, local_path)
+
+    derive_name = config.get("derive_from")
+    if derive_name:
+        source = dict(adapters)[derive_name]
+        # Key the cache on the source path: several configs name their
+        # adapter "case", so a name-only key served one model's variant to
+        # another (mismatched layer counts).
+        source_key = hashlib.sha1(source.encode()).hexdigest()[:8]
+        adapters.append(
+            (
+                derive_name + DERIVED_SUFFIX,
+                write_adapter_variant(
+                    source,
+                    os.path.join(
+                        args.derived_dir, f"{derive_name}{DERIVED_SUFFIX}-{source_key}"
+                    ),
+                    args.keep_derived,
+                    negate_b=True,
+                    drop_lm_head=False,
+                ),
+            )
+        )
+    return adapters
+
+
+def collect_shapes(base_url: str, routes, args):
+    """Outputs for every (shape, route, prompt) the checks compare.
+
+    Three shapes: solo (one route per batch), mixed (every route interleaved
+    in one batch), wide (a batch larger than the cuda-graph capture, so the
+    eager verify path runs).
+    """
+    out = {}
+    solo, accept = collect_solo(base_url, routes, args.max_new_tokens)
+    for route, texts in solo.items():
+        for i, text in enumerate(texts):
+            out[("solo", route, i)] = text
+
+    mixed_texts = [p for p in PROMPTS for _ in routes]
+    mixed_routes = [r for _ in PROMPTS for r in routes]
+    mixed, _ = generate(base_url, mixed_texts, mixed_routes, args.max_new_tokens)
+    for text, route, got in zip(mixed_texts, mixed_routes, mixed):
+        out[("mixed", route, PROMPTS.index(text))] = got
+
+    wide = max(args.wide_batch, len(routes) * 2)
+    wide_routes = [routes[i % len(routes)] for i in range(wide)]
+    wide_texts = [PROMPTS[i % len(PROMPTS)] for i in range(wide)]
+    wide_out, _ = generate(base_url, wide_texts, wide_routes, args.max_new_tokens)
+    for text, route, got in zip(wide_texts, wide_routes, wide_out):
+        out[("wide", route, PROMPTS.index(text))] = got
+
+    return out, accept, solo
+
+
+def unstable_keys(ref_a: dict, ref_b: dict) -> set:
+    """(route, prompt) pairs the reference itself cannot reproduce.
+
+    Greedy decoding is not bitwise reproducible here: batch composition
+    changes reduction order (MoE routing especially), and two runs of the
+    same server can diverge. Anything unstable *without* speculation is a
+    property of the model and backend, not of spec+LoRA, so the spec
+    comparison must exclude it or it reports noise as failure.
+    """
+    unstable = set()
+    for (shape, route, index), text in ref_a.items():
+        # run-to-run, identical shape
+        if ref_b.get((shape, route, index)) != text:
+            unstable.add((route, index))
+        # shape-to-shape, same run
+        if ref_a.get(("solo", route, index)) != text:
+            unstable.add((route, index))
+    return unstable
+
+
+def is_reproducible(base_url: str, route, prompt: str, args, repeats: int = 3) -> bool:
+    """Whether one prompt yields the same greedy output across repeats."""
+    outputs = {
+        generate(base_url, [prompt], [route], args.max_new_tokens)[0][0]
+        for _ in range(repeats)
+    }
+    return len(outputs) == 1
+
+
+def compare(ref_a, spec_a, spec_b, noisy, base_url: str, args) -> int:
+    """Count genuine spec-on vs spec-off differences.
+
+    Skips pairs the reference could not reproduce, pairs where the spec side
+    disagrees with itself, and differences that land on an argmax tie (where
+    the token choice is arbitrary in the first place).
+    """
+    log("comparing spec-on against spec-off on reproducible pairs only")
+    excluded = ties = failures = 0
+    for key, want in ref_a.items():
+        shape, route, index = key
+        # Both sides must be self-consistent before a difference between them
+        # means anything: the instability set is stochastic, so a single
+        # sample per side would report noise as a failure.
+        if (route, index) in noisy or spec_a.get(key) != spec_b.get(key):
+            excluded += 1
+            continue
+        got = spec_a.get(key)
+        if got == want:
+            continue
+
+        # A pair can look stable in two samples and still be stochastic, so
+        # re-sample this specific pair before calling it a defect. Verified
+        # necessary: a prompt that survived the blanket filter turned out to
+        # diverge spec-on vs spec-off with no adapters loaded at all, and to
+        # disagree with itself across repeats.
+        if not is_reproducible(base_url, route, PROMPTS[index], args):
+            ties += 1
+            gap = min_logprob_gap(base_url, route, PROMPTS[index], args.max_new_tokens)
+            log(
+                f"  UNSTABLE [{shape}] route={route} prompt#{index}: the spec "
+                f"server does not reproduce this prompt across repeats "
+                f"(min top-2 logprob gap {gap}); not attributable to spec"
+            )
+            continue
+
+        failures += 1
+        log(f"  MISMATCH [{shape}] route={route} prompt#{index}")
+        log(f"    spec-off: {want!r}")
+        log(f"    spec-on : {got!r}")
+    log(
+        f"  ({excluded} skipped as baseline-nondeterministic, "
+        f"{ties} skipped as not reproducible on re-sampling)"
+    )
+    return failures
+
+
+def run(config: dict, args) -> int:
+    base_url = f"http://127.0.0.1:{args.port}"
+    adapters = resolve_adapters(config, args)
+    routes = [None] + [name for name, _ in adapters]
+    failures = 0
+    process = None
+
+    try:
+        # Phase 1 — reference: same weights and adapters, speculation off.
+        # Collected twice to measure how much this model/backend varies on
+        # its own, which sets the noise floor for the spec comparison.
+        process = launch(config, adapters, base_url, with_spec=False)
+        ref_a, _, solo_a = collect_shapes(base_url, routes, args)
+        ref_b, _, _ = collect_shapes(base_url, routes, args)
+        noisy = unstable_keys(ref_a, ref_b)
+        log(
+            f"baseline noise floor: {len(noisy)} of "
+            f"{len(routes) * len(PROMPTS)} (route, prompt) pairs are not "
+            "reproducible without speculation"
+        )
+
+        for route in routes[1:]:
+            if solo_a[route] == solo_a[None]:
+                failures += 1
+                log(
+                    f"  FAIL adapter {route} output is identical to base on every prompt"
+                )
+        kill_process_tree(process.pid)
+        process = None
+
+        # Phase 2 — speculation on, same three shapes.
+        process = launch(config, adapters, base_url, with_spec=True)
+        spec_a, accept, _ = collect_shapes(base_url, routes, args)
+        spec_b, _, _ = collect_shapes(base_url, routes, args)
+
+        failures += compare(ref_a, spec_a, spec_b, noisy, base_url, args)
+    finally:
+        if process is not None:
+            kill_process_tree(process.pid)
+
+    log("=" * 68)
+    log("per-adapter accept length (tokens per verify step; 1.0 = no speedup)")
+    for route in routes:
+        value = accept.get(route)
+        label = "base" if route is None else route
+        log(f"  {label:<24} {value if value is None else round(value, 3)}")
+    log("=" * 68)
+    log(f"RESULT: {'PASS' if failures == 0 else f'FAIL ({failures} mismatches)'}")
+    return 1 if failures else 0
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--config", help=f"one of: {', '.join(CONFIGS)}")
+    parser.add_argument("--list", action="store_true", help="list configs and exit")
+    parser.add_argument("--port", type=int, default=30000)
+    parser.add_argument("--max-new-tokens", type=int, default=32)
+    parser.add_argument(
+        "--wide-batch",
+        type=int,
+        default=16,
+        help="batch size for the eager-path check; keep it above --cuda-graph-max-bs",
+    )
+    parser.add_argument(
+        "--lora-backend", help="override the config's LoRA kernel backend"
+    )
+    parser.add_argument(
+        "--extra-arg",
+        action="append",
+        default=[],
+        dest="extra_args",
+        help="extra server flag, repeatable (e.g. --extra-arg=--enable-lora-overlap-loading)",
+    )
+    parser.add_argument("--derived-dir", default="/tmp/sglang-derived-loras")
+    parser.add_argument("--keep-derived", action="store_true")
+    parser.add_argument(
+        "--mode",
+        choices=["correctness", "perf", "both"],
+        default="correctness",
+        help="correctness = the 4 output checks; perf = the 4-arm throughput "
+        "and accept-length comparison",
+    )
+    parser.add_argument(
+        "--concurrency",
+        default="1,8,32",
+        help="comma-separated in-flight request counts to sweep (perf mode)",
+    )
+    parser.add_argument("--num-prompts", type=int, default=64)
+    parser.add_argument("--input-len", type=int, default=512)
+    parser.add_argument("--output-len", type=int, default=256)
+    parser.add_argument("--seed", type=int, default=42)
+    args = parser.parse_args()
+
+    if args.list or not args.config:
+        for name, config in CONFIGS.items():
+            algo = next(
+                a.split("=")[1] for a in config["spec_args"] if "algorithm" in a
+            )
+            n = len(config["adapters"]) + (1 if config.get("derive_from") else 0)
+            print(
+                f"{name:<24} tp={config['tp']}  {algo:<7} adapters={n}  {config['model']}"
+            )
+        return 0
+
+    if args.config not in CONFIGS:
+        raise SystemExit(f"unknown config {args.config!r}; use --list")
+    started = time.time()
+    config = dict(CONFIGS[args.config])
+    if args.lora_backend:
+        config["lora_backend"] = args.lora_backend
+    config["extra_args"] = args.extra_args
+    code = 0
+    if args.mode in ("correctness", "both"):
+        code |= run(config, args)
+    if args.mode in ("perf", "both"):
+        code |= run_perf(config, args)
+    log(f"total wall time {time.time() - started:.0f}s")
+    return code
+
+
+if __name__ == "__main__":
+    sys.exit(main())

test/registered/lora/test_lora_spec_decoding.py

@@ -0,0 +1,142 @@
+"""E2E test for multi-adapter LoRA + EAGLE-family speculative decoding.
+
+Adapters apply to the target model only; one shared draft runs unadapted.
+
+Deliberately asserts serving properties rather than exact output text.
+Greedy decoding is not bitwise reproducible across batch shapes or server
+restarts here -- reduction order changes flip a token and greedy amplifies
+it -- so text equality between configurations is a flaky assertion, not a
+correctness oracle. Losslessness is verified out of band by
+test/manual/lora/run_spec_lora_matrix.py, which measures that noise floor
+first. What this guards is what CI can hold stable:
+
+- the server starts at all with multiple adapters + speculation (it used to
+  crash loading the target's adapters into the draft model);
+- adapters are actually applied during target-verify (adapter output differs
+  from base output);
+- a mixed-adapter batch, and a batch wider than the cuda-graph capture, are
+  served without error (the eager verify path used to crash on
+  extend_seq_lens_cpu=None);
+- speculation is really running (accept length above 1).
+"""
+
+import unittest
+
+import requests
+
+from sglang.srt.utils import kill_process_tree
+from sglang.test.ci.ci_register import register_cuda_ci
+from sglang.test.test_utils import (
+    DEFAULT_DRAFT_MODEL_EAGLE3,
+    DEFAULT_TARGET_MODEL_EAGLE3,
+    DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
+    DEFAULT_URL_FOR_TEST,
+    CustomTestCase,
+    popen_launch_server,
+)
+
+register_cuda_ci(est_time=600, stage="base-b", runner_config="1-gpu-large")
+
+PROMPTS = [
+    "What is the capital of France? Answer in one sentence.",
+    "List three primary colors.",
+    "Write a one-sentence story about a brave detective on Mars.",
+]
+# Ranks 8 and 64: a mixed-rank batch is what the per-request lora_ranks
+# indexing has to get right, and uniform ranks would hide a mixup.
+ADAPTERS = [
+    ("fact", "algoprog/fact-generation-llama-3.1-8b-instruct-lora"),
+    ("guard", "nvidia/llama-3.1-nemoguard-8b-topic-control"),
+]
+SAMPLING = {"temperature": 0, "max_new_tokens": 32}
+
+
+class TestEagle3MultiLoRA(CustomTestCase):
+    process = None
+
+    @classmethod
+    def setUpClass(cls):
+        cls.base_url = DEFAULT_URL_FOR_TEST
+        cls.process = popen_launch_server(
+            DEFAULT_TARGET_MODEL_EAGLE3,
+            cls.base_url,
+            timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
+            other_args=[
+                # Canonical EAGLE3 sglang config, as in
+                # test/registered/core/test_basic_sanity_eagle3.py: the draft
+                # checkpoint is fp16, and bf16 + flashinfer cutlass RMSNorm
+                # hits a dtype mismatch on the draft's input_layernorm.
+                "--dtype=float16",
+                "--attention-backend=triton",
+                "--speculative-algorithm=EAGLE3",
+                f"--speculative-draft-model-path={DEFAULT_DRAFT_MODEL_EAGLE3}",
+                "--speculative-num-steps=5",
+                "--speculative-eagle-topk=8",
+                "--speculative-num-draft-tokens=32",
+                "--enable-lora",
+                "--lora-backend=triton",
+                "--max-lora-rank=64",
+                # +1: the base model occupies a memory-pool slot too, and the
+                # batches below co-batch base requests with adapter requests.
+                f"--max-loras-per-batch={len(ADAPTERS) + 1}",
+                "--mem-fraction-static=0.7",
+                "--lora-paths",
+            ]
+            + [f"{name}={path}" for name, path in ADAPTERS],
+        )
+
+    @classmethod
+    def tearDownClass(cls):
+        if cls.process is not None:
+            kill_process_tree(cls.process.pid)
+
+    def _generate(self, texts, lora_paths):
+        response = requests.post(
+            self.base_url + "/generate",
+            json={"text": texts, "lora_path": lora_paths, "sampling_params": SAMPLING},
+        )
+        self.assertEqual(response.status_code, 200, response.text)
+        results = response.json()
+        self.assertEqual(len(results), len(texts))
+        for item in results:
+            self.assertTrue(item["text"].strip(), f"empty output in {results}")
+        return [item["text"] for item in results]
+
+    def test_adapters_are_applied_under_speculation(self):
+        base = self._generate(PROMPTS, [None] * len(PROMPTS))
+        for name, _ in ADAPTERS:
+            adapted = self._generate(PROMPTS, [name] * len(PROMPTS))
+            self.assertNotEqual(
+                adapted,
+                base,
+                f"adapter {name} matched the base model on every prompt; LoRA "
+                "was likely not applied during target-verify",
+            )
+
+    def test_mixed_adapter_and_wide_batches_are_served(self):
+        routes = [None] + [name for name, _ in ADAPTERS]
+        self._generate(
+            [p for p in PROMPTS for _ in routes],
+            [r for _ in PROMPTS for r in routes],
+        )
+        # Wider than the default cuda-graph capture, so target-verify falls
+        # back to the eager path.
+        wide = 24
+        self._generate(
+            [PROMPTS[i % len(PROMPTS)] for i in range(wide)],
+            [routes[i % len(routes)] for i in range(wide)],
+        )
+
+    def test_speculation_is_active(self):
+        self._generate(PROMPTS, [ADAPTERS[0][0]] * len(PROMPTS))
+        info = requests.get(self.base_url + "/get_server_info").json()
+        accept_length = info["internal_states"][0]["avg_spec_accept_length"]
+        self.assertGreater(
+            accept_length,
+            1.0,
+            f"no drafts accepted with LoRA enabled: {accept_length}",
+        )
+
+
+if __name__ == "__main__":
+    unittest.main(verbosity=3)

test/registered/unit/lora/test_lora_spec_verify_batch_info.py

@@ -0,0 +1,109 @@
+"""Unit tests for LoRA batch-info preparation under TARGET_VERIFY.
+
+TARGET_VERIFY reports is_extend() True but ForwardBatch.init_new leaves
+extend_seq_lens / extend_seq_lens_cpu as None (verify is routed through the
+decode-style positions branch), while every request carries a uniform
+spec_info.draft_token_num-token segment. Regression guards for the paths that
+assumed extend fields exist on every is_extend() mode:
+
+- triton eager path: ``max(None)`` TypeError, and 1-token/req segments for a
+  draft_token_num-token layout (silent adapter mis-segmentation).
+- MoE _add_moe_lora_info: ``sum(None)`` TypeError.
+- static cuda-graph path: seg_lens are pre-filled at the captured width; a
+  verify batch of another width must fail loudly, not mis-segment.
+"""
+
+import unittest
+from types import SimpleNamespace
+from unittest.mock import patch
+
+import torch
+
+from sglang.srt.lora.backend.triton_backend import TritonLoRABackend
+from sglang.srt.model_executor.forward_batch_info import ForwardMode
+from sglang.test.ci.ci_register import register_cuda_ci
+from sglang.test.test_utils import CustomTestCase
+
+register_cuda_ci(est_time=30, stage="base-b", runner_config="1-gpu-small")
+
+
+def _verify_batch(bs: int, draft_token_num: int) -> SimpleNamespace:
+    return SimpleNamespace(
+        forward_mode=ForwardMode.TARGET_VERIFY,
+        batch_size=bs,
+        spec_info=SimpleNamespace(draft_token_num=draft_token_num),
+        extend_seq_lens=None,
+        extend_seq_lens_cpu=None,
+    )
+
+
+class TestLoRASpecVerifyBatchInfo(CustomTestCase):
+    def _backend(self, max_loras_per_batch: int = 2) -> TritonLoRABackend:
+        return TritonLoRABackend(
+            max_loras_per_batch=max_loras_per_batch, device=torch.device("cuda")
+        )
+
+    def _prepare(self, backend, forward_batch, use_cuda_graph: bool):
+        backend.prepare_lora_batch(
+            forward_batch,
+            weight_indices=[0, 1],
+            lora_ranks=[8, 8],
+            scalings=[1.0, 1.0],
+            use_cuda_graph=use_cuda_graph,
+        )
+        return backend.batch_info
+
+    def test_eager_target_verify_builds_uniform_draft_width_segments(self):
+        backend = self._backend()
+        batch_info = self._prepare(
+            backend, _verify_batch(bs=2, draft_token_num=4), use_cuda_graph=False
+        )
+        self.assertEqual(batch_info.max_len, 4)
+        self.assertEqual(batch_info.seg_lens[:2].tolist(), [4, 4])
+        self.assertEqual(batch_info.seg_indptr[:3].tolist(), [0, 4, 8])
+        self.assertEqual(batch_info.num_segments, 2)
+
+    def test_graph_path_serves_the_captured_width_and_rejects_others(self):
+        """prepare_lora_batch predicts graph use before can_run_graph decides,
+        so a mismatched width used to silently apply the captured segment
+        layout to a differently-shaped batch (wrong adapter on wrong rows).
+        The matching case also pins that bs is rebound per batch, which is
+        what makes a mixed-adapter batch index the right slots."""
+        backend = self._backend()
+        backend.init_cuda_graph_batch_info(max_bs_in_cuda_graph=4, num_tokens_per_req=4)
+
+        batch_info = self._prepare(
+            backend, _verify_batch(bs=2, draft_token_num=4), use_cuda_graph=True
+        )
+        self.assertIs(batch_info, backend.cuda_graph_batch_info)
+        self.assertEqual(batch_info.seg_lens.tolist(), [4, 4, 4, 4])
+        self.assertEqual(batch_info.bs, 2)
+
+        with self.assertRaisesRegex(AssertionError, "width"):
+            self._prepare(
+                backend, _verify_batch(bs=2, draft_token_num=8), use_cuda_graph=True
+            )
+
+    def test_moe_lora_info_uses_draft_width_token_counts_for_verify(self):
+        backend = self._backend()
+        backend.is_moe_lora = True
+        captured = {}
+
+        def _capture(num_tokens, seg_indptr, lora_ranks, req_to_lora, *args, **kwargs):
+            captured["num_tokens"] = num_tokens
+            captured["max_len"] = kwargs["max_len"]
+            return None, None
+
+        with patch(
+            "sglang.srt.lora.backend.base_backend._compute_moe_lora_info",
+            side_effect=_capture,
+        ):
+            self._prepare(
+                backend, _verify_batch(bs=2, draft_token_num=4), use_cuda_graph=False
+            )
+        self.assertEqual(captured["num_tokens"], 8)
+        self.assertEqual(captured["max_len"], 4)
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/unit/model_executor/test_draft_runner_skips_lora.py

@@ -0,0 +1,51 @@
+"""The draft runner must not build a LoRA manager.
+
+Adapters apply to the target model only. Every worker is handed the same
+published ServerArgs, so `enable_lora` is True for the draft too -- the
+decision is the runner's own, keyed on is_draft_worker. Without it the draft
+tries to load the target's adapters into the draft model, whose layer count
+differs, and startup fails inside LoRAAdapter weight loading.
+
+The LoRA paths downstream then key on `lora_manager is not None` rather than
+the config, so a draft runner skips them by construction.
+"""
+
+import unittest
+from unittest.mock import patch
+
+from sglang.srt.model_executor.model_runner import ModelRunner
+from sglang.test.ci.ci_register import register_cpu_ci
+from sglang.test.test_utils import CustomTestCase
+
+register_cpu_ci(est_time=5, suite="base-a-test-cpu")
+
+
+class TestDraftRunnerSkipsLoRA(CustomTestCase):
+    def _init_lora_called(self, *, is_draft_worker: bool, enable_lora: bool) -> bool:
+        runner = ModelRunner.__new__(ModelRunner)
+        runner.is_draft_worker = is_draft_worker
+        runner.lora_manager = None
+        with patch.object(ModelRunner, "init_lora_manager") as init_lora:
+            with patch("sglang.srt.model_executor.model_runner.get_lora") as get_lora:
+                get_lora.return_value.enable_lora = enable_lora
+                runner.maybe_init_lora_manager()
+        return init_lora.called
+
+    def test_only_the_target_runner_builds_a_lora_manager(self):
+        cases = [
+            (False, True, True),  # target + LoRA -> builds one
+            (True, True, False),  # draft + LoRA -> must not
+            (False, False, False),  # LoRA off -> nobody builds one
+        ]
+        for is_draft_worker, enable_lora, expected in cases:
+            with self.subTest(draft=is_draft_worker, enable_lora=enable_lora):
+                self.assertEqual(
+                    self._init_lora_called(
+                        is_draft_worker=is_draft_worker, enable_lora=enable_lora
+                    ),
+                    expected,
+                )
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/unit/model_executor/test_prefill_cuda_graph_runner.py

@@ -69,9 +69,11 @@ class TestPrefillCudaGraphRunnerChunkedPrefix(CustomTestCase):
             device="cuda",
             gpu_id=0,
             is_draft_worker=False,
+            # A real ModelRunner always has this attribute; the prefill gate
+            # reads it rather than the process-wide LoRA config.
+            lora_manager=None,
             spec_algorithm=SimpleNamespace(is_eagle=lambda: False),
             server_args=SimpleNamespace(
-                enable_lora=False,
                 cuda_graph_config=SimpleNamespace(
                     prefill=SimpleNamespace(bs=[1], backend=Backend.BREAKABLE)
                 ),