The v4 window boot named the real presence-check rule: isinstance against a
runtime_checkable Protocol walks __protocol_attrs__ (which includes members
inherited from BASE protocols) and getattr_static()s each one off the instance,
breaking on the first missing attribute. SupportsEagleBase declares
has_own_lm_head/has_own_embed_tokens as plain instance-var annotations, so
v3's bare supports_eagle3 flag still failed. Replicated in-image with stock
typing: flag-only class -> False; flag + the two base members -> True.
v4 declares all three on Glm5NextForCausalLM:
supports_eagle3: ClassVar[Literal[True]] = True
has_own_lm_head: bool = False
has_own_embed_tokens: bool = False
(False is correct for the two: the wrapper delegates embed/lm_head to its
trunk. The MRO-safe attribute path is kept from v3.)
base 008eeaa2... -> patched 60f27aad..., apply-verified against the pinned
image (patch -p1 reproduces the sha256 and matches the mounted file).