frank-primary: DFlash2 enabling patch — EAGLE3 aux-hidden-state interface for the GLM trunk

glm53-dflash-01-aux-hidden-states.patch: implements the interface whose absence makes
the engine refuse the drafter with 'Model does not support EAGLE3 interface'. Adds
EagleModelMixin to Glm5NextModel, captures the single-stream hidden state entering each
requested layer in the loop, returns (hidden_states, aux_hidden_states) as a tuple when
the list is non-empty, and exposes set_aux_hidden_state_layers /
get_eagle3_default_aux_hidden_state_layers on Glm5NextForCausalLM -- the contract read
out of interfaces.py:1694/1712, eagle3_utils.py:26-31, deepseek_v2.py:1551-1585 and
cudagraph_utils.py:621, with kimi_k25/pixtral as the delegation reference.

Independent of the compile changelist (01-05); it patches the same file as 01, so 01
goes first if both are applied. Scope is honest in the header: this makes the interface
present (the prerequisite for driving DFlash2), it does not promise draft quality and is
not a decode-speed fix.

scripts/patches/glm53-dflash-01-aux-hidden-states.patch

@@ -0,0 +1,117 @@
+# glm53-dflash-01-aux-hidden-states.patch — give the GLM trunk the EAGLE3 / DFlash2
+# auxiliary-hidden-state interface.
+#
+# STATUS: WIP, and INDEPENDENT of the compile changelist (01-05). It patches the same
+# file as glm53-compile-01-model-decorator.patch, so if both are ever applied, apply 01
+# first. Not part of the deployed shape.
+#
+# WHY.  `--speculative-config '{"method":"dflash","model":"/path/to/drafter", ...}'` with
+# incoai/GLM-5.3-Flash-DFlash2 is accepted -- the config parses, the drafter loads -- and
+# then the worker dies at init with:
+#
+#     RuntimeError: Model does not support EAGLE3 interface
+#
+# raised by v1/worker/gpu/spec_decode/eagle/eagle3_utils.py:20 through
+# `supports_eagle3(model)` == `isinstance(model, SupportsEagle3)` (a runtime-checkable
+# Protocol).  Nothing about the drafter, the method name or the payload is wrong:
+# `glm5next` implements neither half of the contract.
+#
+# THE CONTRACT (read out of this image, not assumed):
+#   * interfaces.py:1694 -- `holder = getattr(parent_ref, "model", parent_ref)` then
+#     `assert isinstance(holder, EagleModelMixin)` then
+#     `holder._set_aux_hidden_state_layers(layers)`.  The INNER trunk must inherit
+#     EagleModelMixin, which supplies `aux_hidden_state_layers` and the slot helpers.
+#   * interfaces.py:1712-1719 -- the default layer set is (2, L // 2, L - 3) and needs
+#     the holder to expose `layers`.
+#   * eagle3_utils.py:26-31 -- layers come from the spec config when it carries them
+#     (this drafter ships target_layer_ids [5, 14, 24, 33, 42], mapped to trunk
+#     indices), else from get_eagle3_default_aux_hidden_state_layers().
+#   * deepseek_v2.py:1551-1585 and v1/worker/gpu/cudagraph_utils.py:621 -- the trunk
+#     appends one tensor per aux layer while looping and returns the TUPLE
+#     (hidden_states, aux_hidden_states) only when that list is non-empty.
+#
+# WHAT IT ADDS for GLM: the mixin on Glm5NextModel; aux capture in the layer loop, where
+# the aux state is the single-stream `hidden_states` ENTERING that layer (GLM's loop
+# carries the already-summed single-stream state -- its non-mHC branch re-splits
+# `residual = hidden_states` inside the layer -- so this is the equivalent of
+# deepseek_v2's `hidden_states + residual`); the conditional tuple return; and
+# set_aux_hidden_state_layers / get_eagle3_default_aux_hidden_state_layers on
+# Glm5NextForCausalLM, delegating to the inner trunk (the same two-liner shape
+# kimi_k25.py:466 and pixtral.py:503 use).
+#
+# HONEST SCOPE: this makes the interface PRESENT, which is exactly what the engine
+# checks -- it does not make drafts GOOD, and per the measured profile it is not a
+# decode-speed fix (a verification pass pays pointwise cost proportional to its token
+# count, which is why MTP4 measured flat).  It is the prerequisite for driving DFlash2
+# on this endpoint at all.
+#
+# TARGET: vllm/models/glm5next/common/model.py   (inside the pinned image)
+#   base    sha256 008eeaa2a07e091465319f86900b5a321d921238723ccbe22e6b9e971e1d2b28
+#   patched sha256 4ff6ff8ddf8af3d74bef699f98fc95a99ee47586f6e785248e7dc4b683b72d7a
+#
+# APPLY: `patch -p1` from the vllm package root, or bind-mount the patched file over
+# site-packages (which is what a scratch-launcher DFLASH_PATCH=1 does).
+--- a/vllm/models/glm5next/common/model.py
++++ b/vllm/models/glm5next/common/model.py
+@@ -95,6 +95,9 @@
+ logger = init_logger(__name__)
+ 
+ 
++from vllm.model_executor.models.interfaces import EagleModelMixin
++
++
+ class Glm5NextMLP(nn.Module):
+     def __init__(
+         self,
+@@ -623,7 +626,7 @@
+         )
+ 
+ 
+-class Glm5NextModel(nn.Module):
++class Glm5NextModel(nn.Module, EagleModelMixin):
+     def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
+         super().__init__()
+ 
+@@ -730,7 +733,14 @@
+         if self.is_sequence_parallel:
+             hidden_states = sp_shard(hidden_states)
+ 
+-        for layer in self._active_layers:
++        aux_hidden_states: list[torch.Tensor] = []
++        for local_idx, layer in enumerate(self._active_layers):
++            if (getattr(self, "start_layer", 0) + local_idx) in self.aux_hidden_state_layers:
++                # Auxiliary hidden state for EAGLE-3 / DFlash2 drafts: the
++                # single-stream state ENTERING this layer, before its input norm --
++                # the same semantic deepseek_v2 implements by appending
++                # hidden_states + residual at this point in its loop.
++                aux_hidden_states.append(hidden_states)
+             hidden_states, residual, post, comb = layer(
+                 positions, hidden_states, residual, post, comb
+             )
+@@ -749,6 +759,8 @@
+             hidden_states = sp_all_gather(hidden_states)[:full_num_tokens]
+ 
+         hidden_states = self.norm(hidden_states)
++        if len(aux_hidden_states) > 0:
++            return hidden_states, aux_hidden_states
+         return hidden_states
+ 
+     def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]) -> set[str]:
+@@ -963,6 +975,17 @@
+     def embed_input_ids(self, input_ids: torch.Tensor) -> torch.Tensor:
+         return self.model.embed_input_ids(input_ids)
+ 
++    def set_aux_hidden_state_layers(self, layers: tuple[int, ...]) -> None:
++        # EAGLE-3 / DFlash2 interface (interfaces.py asserts the holder inherits
++        # EagleModelMixin, which supplies the slot plumbing behind this attribute).
++        self.model.aux_hidden_state_layers = layers
++
++    def get_eagle3_default_aux_hidden_state_layers(self) -> tuple[int, ...]:
++        # Only used when the spec config carries no explicit aux layers; the
++        # DFlash2 drafters this fleet runs ship target_layer_ids instead.
++        num_layers = len(self.model.layers)
++        return (2, num_layers // 2, num_layers - 3)
++
+     def forward(
+         self,
+         input_ids: torch.Tensor | None,