mtp: support for gemma-4 E2B and E4B assistants (#24282)

* models: update converter to support smaller assistants

* models: add masked_embd tensors to gemma4-assist arch

* gemma-4: remove temp debug for conversion

* gemma-4-mtp: filter out masked_embedding tensors during conversion

Author: max-krasnyansky

conversion/gemma.py

@@ -789,6 +789,16 @@ def set_gguf_parameters(self):
 class Gemma4AssistantModel(Gemma4Model):
     model_arch = gguf.MODEL_ARCH.GEMMA4_ASSISTANT
 
+    @classmethod
+    def filter_tensors(cls, item: tuple[str, Callable[[], Tensor]]) -> tuple[str, Callable[[], Tensor]] | None:
+        name, gen = item
+
+        if "masked_embedding" in name:
+            logger.debug(f"Skipping get tensor {name!r} in safetensors so that convert can end normally.")
+            return None
+
+        return super().filter_tensors(item)
+
     def set_gguf_parameters(self):
         super().set_gguf_parameters()
         self.gguf_writer.add_embedding_length_out(self.hparams["backbone_hidden_size"])

gguf-py/gguf/constants.py

@@ -538,6 +538,8 @@ class VISION_PROJECTOR_TYPE(IntEnum):
 class MODEL_TENSOR(IntEnum):
     TOKEN_EMBD           = auto()
     TOKEN_EMBD_NORM      = auto()
+    MASKED_EMBD_CENTROIDS= auto()
+    MASKED_EMBD_ORDERING = auto()
     TOKEN_TYPES          = auto()
     POS_EMBD             = auto()
     OUTPUT               = auto()
@@ -1087,6 +1089,8 @@ class MODEL_TENSOR(IntEnum):
     MODEL_TENSOR.TOKEN_EMBD:                "token_embd",
     MODEL_TENSOR.TOKEN_EMBD_NORM:           "token_embd_norm",
     MODEL_TENSOR.TOKEN_TYPES:               "token_types",
+    MODEL_TENSOR.MASKED_EMBD_CENTROIDS:     "masked_embd_centroids",
+    MODEL_TENSOR.MASKED_EMBD_ORDERING:      "masked_embd_ordering",
     MODEL_TENSOR.POS_EMBD:                  "position_embd",
     MODEL_TENSOR.OUTPUT_NORM:               "output_norm",
     MODEL_TENSOR.OUTPUT:                    "output",
@@ -2586,6 +2590,8 @@ class MODEL_TENSOR(IntEnum):
     MODEL_ARCH.GEMMA4_ASSISTANT: [
         MODEL_TENSOR.ROPE_FREQS,
         MODEL_TENSOR.TOKEN_EMBD,
+        MODEL_TENSOR.MASKED_EMBD_CENTROIDS,
+        MODEL_TENSOR.MASKED_EMBD_ORDERING,
         MODEL_TENSOR.OUTPUT_NORM,
         MODEL_TENSOR.NEXTN_PROJ_PRE,
         MODEL_TENSOR.NEXTN_PROJ_POST,

gguf-py/gguf/tensor_mapping.py

@@ -37,6 +37,14 @@ class TensorNameMap:
             "model.embed",                               # talkie
         ),
 
+        # Masked embeddings
+        MODEL_TENSOR.MASKED_EMBD_CENTROIDS: (
+            "masked_embedding.centroids",                # gemma-4 E2B/E4B assistants
+        ),
+        MODEL_TENSOR.MASKED_EMBD_ORDERING: (
+            "masked_embedding.token_ordering",           # gemma-4 E2B/E4B assistants
+        ),
+
         # Token type embeddings
         MODEL_TENSOR.TOKEN_TYPES: (
             "embeddings.token_type_embeddings",  # bert nomic-bert

src/llama-arch.cpp

@@ -559,6 +559,8 @@ static const std::map<llm_tensor, const char *> LLM_TENSOR_NAMES = {
     { LLM_TENSOR_INDEXER_PROJ,                           "blk.%d.indexer.proj" },
     { LLM_TENSOR_INDEXER_ATTN_K,                         "blk.%d.indexer.attn_k" },
     { LLM_TENSOR_INDEXER_ATTN_Q_B,                       "blk.%d.indexer.attn_q_b" },
+    { LLM_TENSOR_MASKED_EMBD_CENTROIDS,                  "masked_embd_centroids" },
+    { LLM_TENSOR_MASKED_EMBD_ORDERING,                   "masked_embd_ordering" },
 };
 
 // declare information about the model weight tensors:
@@ -783,6 +785,8 @@ static const std::map<llm_tensor, llm_tensor_info> LLM_TENSOR_INFOS = {
     // latent projections feed ggml_mul_mat, the buft probe must use MUL_MAT to keep them on GPU
     {LLM_TENSOR_FFN_LATENT_DOWN,            {LLM_TENSOR_LAYER_REPEATING, GGML_OP_MUL_MAT}},
     {LLM_TENSOR_FFN_LATENT_UP,              {LLM_TENSOR_LAYER_REPEATING, GGML_OP_MUL_MAT}},
+    {LLM_TENSOR_MASKED_EMBD_CENTROIDS,      {LLM_TENSOR_LAYER_INPUT,     GGML_OP_NONE}},
+    {LLM_TENSOR_MASKED_EMBD_ORDERING,       {LLM_TENSOR_LAYER_INPUT,     GGML_OP_NONE}},
 };
 
 LLM_KV::LLM_KV(llm_arch arch, const char * suffix) : arch(arch), suffix(suffix) {}

src/llama-arch.h

@@ -566,8 +566,11 @@ enum llm_tensor {
     LLM_TENSOR_NEXTN_HNORM,
     LLM_TENSOR_NEXTN_SHARED_HEAD_HEAD,
     LLM_TENSOR_NEXTN_SHARED_HEAD_NORM,
+    LLM_TENSOR_MASKED_EMBD_CENTROIDS,
+    LLM_TENSOR_MASKED_EMBD_ORDERING,
 };
 
+
 enum llm_tensor_layer {
     LLM_TENSOR_LAYER_INPUT,
     LLM_TENSOR_LAYER_REPEATING,

src/models/gemma4-assistant.cpp

@@ -39,6 +39,9 @@ void llama_model_gemma4_assistant::load_arch_tensors(llama_model_loader &) {
 
     output_norm = create_tensor(tn(LLM_TENSOR_OUTPUT_NORM, "weight"), { n_embd }, 0);
 
+    create_tensor(tn(LLM_TENSOR_MASKED_EMBD_CENTROIDS, "weight"), {}, TENSOR_NOT_REQUIRED);
+    create_tensor(tn(LLM_TENSOR_MASKED_EMBD_ORDERING),  {}, TENSOR_NOT_REQUIRED);
+
     const int64_t n_embd_backbone = hparams.n_embd_inp();
     nextn_proj_post = create_tensor(tn(LLM_TENSOR_NEXTN_PROJ_POST, "weight"), { n_embd, n_embd_backbone }, 0);