]> git.djapps.eu Git - pkg/ggml/sources/llama.cpp/commitdiff
StepFun 3.5 MTP (#23274)
authorPiotr Wilkin (ilintar) <redacted>
Tue, 2 Jun 2026 15:44:35 +0000 (17:44 +0200)
committerGitHub <redacted>
Tue, 2 Jun 2026 15:44:35 +0000 (17:44 +0200)
* StepFun 3.5 MTP

* Simplify to single layer

* Rollback core changes

* fix flake8 errors

* Remove scripts

* modify to convention

* Apply suggestions from code review

Co-authored-by: Sigbjørn Skjæret <redacted>
* dos2unix

---------

Co-authored-by: Sigbjørn Skjæret <redacted>
conversion/step3.py
convert_hf_to_gguf.py
gguf-py/gguf/constants.py
src/models/models.h
src/models/step35.cpp

index eeba66c7a8a939cbb111f25596beb795142203af..8c45b61c954a7aff238b159f5088e4eb0ab26c45 100644 (file)
@@ -99,6 +99,34 @@ class Step3VLTextModel(Qwen3Model):
 class Step35Model(TextModel):
     model_arch = gguf.MODEL_ARCH.STEP35
 
+    # The --mtp / --no-mtp toggles are ModelBase.mtp_only / no_mtp (set in
+    # convert_hf_to_gguf.py main()). Unlike Qwen3.5, which stores MTP under a
+    # `mtp.*` namespace, Step3.5 appends MTP layers at
+    # `model.layers.{num_hidden_layers + i}`, so we filter them by layer index.
+    # The trunk layer count is captured before indexing so the classmethod
+    # filter_tensors can tell the appended MTP block(s) apart from the trunk.
+    _n_main_layers: int | None = None
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        # NextN/MTP layers are appended past num_hidden_layers; extend the
+        # tensor map to cover them so the MTP block's tensors get correctly
+        # indexed names. When --no-mtp drops the MTP blocks, fall back to the
+        # base num_hidden_layers so we don't reserve unused slots.
+        n_nextn = int(self.hparams.get("num_nextn_predict_layers", 0))
+        if n_nextn > 0 and not self.no_mtp:
+            self.block_count += n_nextn
+            self.tensor_map = gguf.get_tensor_name_map(self.model_arch, self.block_count)
+
+    def index_tensors(self, remote_hf_model_id: str | None = None):
+        # filter_tensors is a classmethod and can't reach self.hparams; stash
+        # the trunk layer count here (before indexing runs) so it can detect
+        # the appended MTP layers by index.
+        hparams = {**self.hparams, **self.hparams.get("text_config", {})}
+        key = next((k for k in ["n_layers", "num_hidden_layers", "n_layer", "num_layers"] if k in hparams), None)
+        type(self)._n_main_layers = hparams.get(key)
+        return super().index_tensors(remote_hf_model_id=remote_hf_model_id)
+
     def set_gguf_parameters(self):
         rope_theta = self.hparams.get("rope_theta")
         if isinstance(rope_theta, list):
@@ -119,8 +147,25 @@ class Step35Model(TextModel):
         n_head_swa = attn_other.get("num_attention_heads", n_head_base)
         n_kv_swa = attn_other.get("num_attention_groups", n_kv_base)
 
-        layer_types = layer_types[: self.block_count]
-        partial_rotary_factors = partial_rotary_factors[: self.block_count]
+        n_nextn = int(self.hparams.get("num_nextn_predict_layers", 0))
+
+        # The Step3p5 HF checkpoint stores layer_types/partial_rotary_factors
+        # entries for the MTP blocks past num_hidden_layers; preserve them so
+        # the MTP layer's attention shape, SWA flag, and partial RoPE dim are
+        # set correctly. Pad with full-attention defaults if the checkpoint
+        # truncated them.
+        def _pad(arr, n, default):
+            arr = list(arr)
+            if len(arr) < n:
+                arr = arr + [default] * (n - len(arr))
+            return arr[:n]
+
+        layer_types = _pad(layer_types, self.block_count, "full_attention")
+        partial_rotary_factors = _pad(
+            partial_rotary_factors,
+            self.block_count,
+            0.5,  # full_attention default for Step3p5
+        )
         assert [1.0 if lt == "sliding_attention" else 0.5 for lt in layer_types] == partial_rotary_factors
         head_arr = [n_head_swa if lt == "sliding_attention" else n_head_base for lt in layer_types]
         kv_arr = [n_kv_swa if lt == "sliding_attention" else n_kv_base for lt in layer_types]
@@ -157,31 +202,61 @@ class Step35Model(TextModel):
 
         self.gguf_writer.add_layer_norm_rms_eps(self.hparams.get("rms_norm_eps", 1e-5))
 
-        # Optional per-layer SwiGLU clamps.
+        # Optional per-layer SwiGLU clamps. MTP layers default to no clamping (0.0).
         if (limits := self.hparams.get("swiglu_limits")) is not None:
-            limits_f = [0.0 if v is None else float(v) for v in limits[: self.block_count]]
+            limits_f = _pad(
+                [0.0 if v is None else float(v) for v in limits],
+                self.block_count,
+                0.0,
+            )
             self.gguf_writer.add_swiglu_clamp_exp(limits_f)
         if (limits_shared := self.hparams.get("swiglu_limits_shared")) is not None:
-            limits_shared_f = [0.0 if v is None else float(v) for v in limits_shared[: self.block_count]]
+            limits_shared_f = _pad(
+                [0.0 if v is None else float(v) for v in limits_shared],
+                self.block_count,
+                0.0,
+            )
             self.gguf_writer.add_swiglu_clamp_shexp(limits_shared_f)
 
+        if n_nextn > 0 and not self.no_mtp:
+            self.gguf_writer.add_nextn_predict_layers(n_nextn)
+
     @classmethod
     def filter_tensors(cls, item: tuple[str, Callable[[], Tensor]]) -> tuple[str, Callable[[], Tensor]] | None:
-        name, gen = item
+        if (titem := super().filter_tensors(item)) is None:
+            return None
+        name, gen = titem
 
         # Map router bias (expert selection bias) to a GGUF bias tensor
         if name.endswith(".moe.router_bias"):
             name += ".bias"
 
-        return super().filter_tensors((name, gen))
+        # Step3.5 appends the MTP block(s) past num_hidden_layers.
+        assert cls._n_main_layers is not None
+        is_mtp = (m := re.match(r"model\.layers\.(\d+)\.", name)) is not None and int(m.group(1)) >= cls._n_main_layers
+
+        # --no-mtp: drop the appended MTP block(s) entirely.
+        if is_mtp and cls.no_mtp:
+            return None
+        # --mtp: keep ONLY MTP-block tensors plus the shared embeddings/norm/
+        # lm_head (so the resulting GGUF carries just the draft head).
+        if cls.mtp_only and not is_mtp and name not in (
+            "model.embed_tokens.weight", "model.norm.weight", "lm_head.weight",
+        ):
+            return None
+
+        # The checkpoint nests the per-MTP-layer shared head under
+        # `model.layers.{N+i}.transformer.shared_head.{norm,output}.weight`;
+        # strip the `transformer.` infix and rename `output` → `head` so the
+        # existing NEXTN_SHARED_HEAD_{NORM,HEAD} tensor mapping picks them up.
+        # Mirrors vllm's `_rewrite_spec_layer_name` (step3p5_mtp.py).
+        if is_mtp:
+            name = name.replace(".transformer.", ".")
+            name = name.replace("shared_head.output", "shared_head.head")
+
+        return name, gen
 
     def modify_tensors(self, data_torch: Tensor, name: str, bid: int | None):
-        # remove mtp layers
-        if (m := re.match(r"model\.layers\.(\d+)\.", name)) is not None:
-            il = int(m.group(1))
-            n_main = int(self.hparams.get("num_hidden_layers", self.block_count))
-            if il >= n_main:
-                return
         if name.endswith("norm.weight"):
             data_torch += 1.0
 
@@ -190,6 +265,21 @@ class Step35Model(TextModel):
 
         yield from super().modify_tensors(data_torch, name, bid)
 
+    def prepare_metadata(self, vocab_only: bool):
+        from_dir = self.fname_out.is_dir()
+        super().prepare_metadata(vocab_only=vocab_only)
+
+        # Mirror Qwen3.5's behavior: when emitting a draft-only file into a
+        # directory, prefix with "mtp-" so it doesn't collide with the trunk.
+        if not self.mtp_only or not from_dir:
+            return
+
+        output_type: str = self.ftype.name.partition("_")[2]
+        fname_default: str = gguf.naming_convention(
+            self.metadata.name, self.metadata.basename, self.metadata.finetune,
+            self.metadata.version, size_label=None, output_type=output_type, model_type=None)
+        self.fname_out = self.fname_out.parent / f"mtp-{fname_default}.gguf"
+
     def generate_extra_tensors(self) -> Iterable[tuple[str, Tensor]]:
         # Step35 can optionally use Llama-3 style RoPE scaling (HF: rope_scaling.rope_type == "llama3").
         # llama.cpp represents this via a single extra tensor: "rope_freqs.weight" (aka MODEL_TENSOR.ROPE_FREQS).
index 85527553563d792876a9e4340a33a63f8fc888d2..cd19eebdfa342de0ec7aa624d0e32a34e45ebb81 100755 (executable)
@@ -251,8 +251,9 @@ def main() -> None:
 
         if args.mtp or args.no_mtp:
             from conversion.qwen import _Qwen35MtpMixin
-            if not issubclass(model_class, _Qwen35MtpMixin):
-                logger.error("--mtp / --no-mtp are only supported for Qwen3.5/3.6 text variants today")
+            from conversion.step3 import Step35Model
+            if not (issubclass(model_class, _Qwen35MtpMixin) or issubclass(model_class, Step35Model)):
+                logger.error("--mtp / --no-mtp are only supported for Qwen3.5/3.6 and Step3.5 text variants today")
                 sys.exit(1)
             if args.no_mtp:
                 model_class.no_mtp = True
index 8aed0d76671a7d00c58cc6b914d4d3c7768863f3..8c6ff280d94b748c89bace5752f65b09b502db9b 100644 (file)
@@ -3994,6 +3994,13 @@ MODEL_TENSORS: dict[MODEL_ARCH, list[MODEL_TENSOR]] = {
         MODEL_TENSOR.FFN_GATE_SHEXP,
         MODEL_TENSOR.FFN_DOWN_SHEXP,
         MODEL_TENSOR.FFN_EXP_PROBS_B,
+        # NextN/MTP tensors (Step3p5 draft head)
+        MODEL_TENSOR.NEXTN_EH_PROJ,
+        MODEL_TENSOR.NEXTN_EMBED_TOKENS,
+        MODEL_TENSOR.NEXTN_ENORM,
+        MODEL_TENSOR.NEXTN_HNORM,
+        MODEL_TENSOR.NEXTN_SHARED_HEAD_HEAD,
+        MODEL_TENSOR.NEXTN_SHARED_HEAD_NORM,
     ],
     MODEL_ARCH.LLAMA_EMBED: [
         MODEL_TENSOR.TOKEN_EMBD,
index 5251e2d82802ccd7f0e6722367f7db1b72c03080..cbef040870b62bbb3f2b47608fa3f9bf858ed391 100644 (file)
@@ -1913,5 +1913,9 @@ struct llama_model_step35 : public llama_model_base {
         graph(const llama_model & model, const llm_graph_params & params);
     };
 
+    struct graph_mtp : public llm_graph_context {
+        graph_mtp(const llama_model & model, const llm_graph_params & params);
+    };
+
     std::unique_ptr<llm_graph_context> build_arch_graph(const llm_graph_params & params) const override;
 };
index 3b68e68707aed6ca8b12b60fc18efa6be213bc73..caf18c743ff48ce9f327b5e854bb82c6e532779f 100644 (file)
@@ -26,20 +26,36 @@ void llama_model_step35::load_arch_hparams(llama_model_loader & ml) {
     ml.get_key_or_arr(LLM_KV_SWIGLU_CLAMP_EXP,   hparams.swiglu_clamp_exp,   hparams.n_layer, false);
     ml.get_key_or_arr(LLM_KV_SWIGLU_CLAMP_SHEXP, hparams.swiglu_clamp_shexp, hparams.n_layer, false);
 
-    switch (hparams.n_layer) {
+    // NextN/MTP (Step3p5): extra decoder block appended beyond the main stack.
+    ml.get_key(LLM_KV_NEXTN_PREDICT_LAYERS, hparams.nextn_predict_layers, false);
+    GGML_ASSERT(hparams.nextn_predict_layers < hparams.n_layer && "nextn_predict_layers must be < n_layer");
+
+    switch (hparams.n_layer - hparams.nextn_predict_layers) {
         case 45: type = LLM_TYPE_196B_A11B; break;
         default: type = LLM_TYPE_UNKNOWN;
     }
 }
 
-void llama_model_step35::load_arch_tensors(llama_model_loader &) {
+void llama_model_step35::load_arch_tensors(llama_model_loader & ml) {
     LLAMA_LOAD_LOCALS;
 
+    const uint32_t n_main = n_layer - hparams.nextn_predict_layers;
+    const bool mtp_only   = (hparams.nextn_predict_layers > 0) &&
+                            (ml.get_weight("blk.0.attn_norm.weight") == nullptr);
+    // Trunk-only: the GGUF declares MTP layers in metadata but the actual MTP
+    // tensors live in a separate file (e.g. user split target/draft). Mark
+    // MTP tensors NOT_REQUIRED so the trunk loads cleanly.
+    const std::string mtp_probe = "blk." + std::to_string(n_main) + ".nextn.eh_proj.weight";
+    const bool trunk_only = (hparams.nextn_predict_layers > 0) &&
+                            (ml.get_weight(mtp_probe.c_str()) == nullptr);
+    const int trunk_flags = mtp_only  ? TENSOR_NOT_REQUIRED : 0;
+    const int mtp_flags   = trunk_only ? TENSOR_NOT_REQUIRED : 0;
+
     tok_embd = create_tensor(tn(LLM_TENSOR_TOKEN_EMBD, "weight"), {n_embd, n_vocab}, 0);
 
     // output
     output_norm = create_tensor(tn(LLM_TENSOR_OUTPUT_NORM, "weight"), {n_embd}, 0);
-    output      = create_tensor(tn(LLM_TENSOR_OUTPUT,      "weight"), {n_embd, n_vocab}, 0);
+    output      = create_tensor(tn(LLM_TENSOR_OUTPUT,      "weight"), {n_embd, n_vocab}, trunk_flags);
 
     // STEP35 supports per-layer partial RoPE dims; rope factors are stored as a single shared tensor
     // ("rope_freqs.weight") and ggml uses only the first (n_rot_l/2) entries per layer.
@@ -51,14 +67,14 @@ void llama_model_step35::load_arch_tensors(llama_model_loader &) {
         n_rot_max = n_rot;
     }
 
-    for (int i = 0; i < n_layer; ++i) {
+    auto load_block_trunk = [&](int i, int flags) {
         auto & layer = layers[i];
 
         const uint32_t n_head_l      = hparams.n_head(i);
         const uint32_t n_embd_k_gqa  = hparams.n_embd_k_gqa(i);
         const uint32_t n_embd_v_gqa  = hparams.n_embd_v_gqa(i);
 
-        layer.attn_norm   = create_tensor(tn(LLM_TENSOR_ATTN_NORM, "weight", i), {n_embd}, 0);
+        layer.attn_norm   = create_tensor(tn(LLM_TENSOR_ATTN_NORM, "weight", i), {n_embd}, flags);
         layer.attn_q_norm = create_tensor(tn(LLM_TENSOR_ATTN_Q_NORM, "weight", i), {n_embd_head_k}, TENSOR_NOT_REQUIRED);
         layer.attn_k_norm = create_tensor(tn(LLM_TENSOR_ATTN_K_NORM, "weight", i), {n_embd_head_k}, TENSOR_NOT_REQUIRED);
 
@@ -70,13 +86,13 @@ void llama_model_step35::load_arch_tensors(llama_model_loader &) {
             layer.rope_freqs = create_tensor(tn(LLM_TENSOR_ROPE_FREQS, "weight", i), {n_rot_max/2}, TENSOR_NOT_REQUIRED | (i != 0 ? TENSOR_DUPLICATED : 0));
         }
 
-        create_tensor_qkv(layer, i, n_embd, n_embd_head_k * n_head_l, n_embd_k_gqa, n_embd_v_gqa, 0);
-        layer.wo = create_tensor(tn(LLM_TENSOR_ATTN_OUT, "weight", i), {n_embd_head_v * n_head_l, n_embd}, 0);
+        create_tensor_qkv(layer, i, n_embd, n_embd_head_k * n_head_l, n_embd_k_gqa, n_embd_v_gqa, flags);
+        layer.wo = create_tensor(tn(LLM_TENSOR_ATTN_OUT, "weight", i), {n_embd_head_v * n_head_l, n_embd}, flags);
 
         // head-wise attention gate (Step35 self_attn.g_proj)
         layer.wqkv_gate = create_tensor(tn(LLM_TENSOR_ATTN_GATE, "weight", i), {n_embd, n_head_l}, TENSOR_NOT_REQUIRED);
 
-        layer.ffn_norm = create_tensor(tn(LLM_TENSOR_FFN_NORM, "weight", i), {n_embd}, 0);
+        layer.ffn_norm = create_tensor(tn(LLM_TENSOR_FFN_NORM, "weight", i), {n_embd}, flags);
 
         // dense MLP (leading dense blocks)
         layer.ffn_gate = create_tensor(tn(LLM_TENSOR_FFN_GATE, "weight", i), {n_embd,   n_ff}, TENSOR_NOT_REQUIRED);
@@ -95,10 +111,86 @@ void llama_model_step35::load_arch_tensors(llama_model_loader &) {
         layer.ffn_gate_shexp = create_tensor(tn(LLM_TENSOR_FFN_GATE_SHEXP, "weight", i), {n_embd, hparams.n_ff_shexp}, TENSOR_NOT_REQUIRED);
         layer.ffn_up_shexp   = create_tensor(tn(LLM_TENSOR_FFN_UP_SHEXP,   "weight", i), {n_embd, hparams.n_ff_shexp}, TENSOR_NOT_REQUIRED);
         layer.ffn_down_shexp = create_tensor(tn(LLM_TENSOR_FFN_DOWN_SHEXP, "weight", i), {hparams.n_ff_shexp, n_embd}, TENSOR_NOT_REQUIRED);
+    };
+
+    auto load_block_mtp = [&](int i, bool is_first_mtp) {
+        auto & layer = layers[i];
+
+        const uint32_t n_head_l      = hparams.n_head(i);
+        const uint32_t n_embd_k_gqa  = hparams.n_embd_k_gqa(i);
+        const uint32_t n_embd_v_gqa  = hparams.n_embd_v_gqa(i);
+
+        // The MTP block is a full Step3p5 decoder layer (mtp_block) plus the
+        // NextN-specific wiring (enorm/hnorm/eh_proj + optional shared head).
+        // `mtp_flags` becomes NOT_REQUIRED when the GGUF is trunk-only.
+        //
+        // Only the FIRST MTP block (i == n_main) is required for the
+        // single-block MTP runtime; trailing MTP blocks are always tolerated
+        // as missing so pruned GGUFs (block 0 only) load cleanly. Override
+        // mtp_flags to NOT_REQUIRED for those.
+        const int eff_mtp_flags = is_first_mtp ? mtp_flags : (mtp_flags | TENSOR_NOT_REQUIRED);
+
+        layer.attn_norm   = create_tensor(tn(LLM_TENSOR_ATTN_NORM, "weight", i), {n_embd}, eff_mtp_flags);
+        layer.attn_q_norm = create_tensor(tn(LLM_TENSOR_ATTN_Q_NORM, "weight", i), {n_embd_head_k}, TENSOR_NOT_REQUIRED);
+        layer.attn_k_norm = create_tensor(tn(LLM_TENSOR_ATTN_K_NORM, "weight", i), {n_embd_head_k}, TENSOR_NOT_REQUIRED);
+
+        if (hparams.rope_scaling_type_train == LLAMA_ROPE_SCALING_TYPE_LONGROPE) {
+            layer.rope_long  = create_tensor(tn(LLM_TENSOR_ROPE_FACTORS_LONG,  "weight", i), {n_rot_max/2}, TENSOR_NOT_REQUIRED | TENSOR_DUPLICATED);
+            layer.rope_short = create_tensor(tn(LLM_TENSOR_ROPE_FACTORS_SHORT, "weight", i), {n_rot_max/2}, TENSOR_NOT_REQUIRED | TENSOR_DUPLICATED);
+        } else {
+            layer.rope_freqs = create_tensor(tn(LLM_TENSOR_ROPE_FREQS, "weight", i), {n_rot_max/2}, TENSOR_NOT_REQUIRED | TENSOR_DUPLICATED);
+        }
+
+        create_tensor_qkv(layer, i, n_embd, n_embd_head_k * n_head_l, n_embd_k_gqa, n_embd_v_gqa, eff_mtp_flags);
+        layer.wo = create_tensor(tn(LLM_TENSOR_ATTN_OUT, "weight", i), {n_embd_head_v * n_head_l, n_embd}, eff_mtp_flags);
+
+        layer.wqkv_gate = create_tensor(tn(LLM_TENSOR_ATTN_GATE, "weight", i), {n_embd, n_head_l}, TENSOR_NOT_REQUIRED);
+
+        layer.ffn_norm = create_tensor(tn(LLM_TENSOR_FFN_NORM, "weight", i), {n_embd}, eff_mtp_flags);
+
+        // dense MLP (leading dense blocks) — present if the MTP block isn't MoE
+        layer.ffn_gate = create_tensor(tn(LLM_TENSOR_FFN_GATE, "weight", i), {n_embd,   n_ff}, TENSOR_NOT_REQUIRED);
+        layer.ffn_down = create_tensor(tn(LLM_TENSOR_FFN_DOWN, "weight", i), {  n_ff, n_embd}, TENSOR_NOT_REQUIRED);
+        layer.ffn_up   = create_tensor(tn(LLM_TENSOR_FFN_UP,   "weight", i), {n_embd,   n_ff}, TENSOR_NOT_REQUIRED);
+
+        // MoE routed experts + selection bias (router_bias)
+        const int64_t n_ff_exp = hparams.n_ff_exp;
+        layer.ffn_gate_inp      = create_tensor(tn(LLM_TENSOR_FFN_GATE_INP,  "weight", i), {n_embd, n_expert}, TENSOR_NOT_REQUIRED);
+        layer.ffn_gate_exps     = create_tensor(tn(LLM_TENSOR_FFN_GATE_EXPS, "weight", i), {n_embd, n_ff_exp,   n_expert}, TENSOR_NOT_REQUIRED);
+        layer.ffn_down_exps     = create_tensor(tn(LLM_TENSOR_FFN_DOWN_EXPS, "weight", i), {n_ff_exp,   n_embd, n_expert}, TENSOR_NOT_REQUIRED);
+        layer.ffn_up_exps       = create_tensor(tn(LLM_TENSOR_FFN_UP_EXPS,   "weight", i), {n_embd, n_ff_exp,   n_expert}, TENSOR_NOT_REQUIRED);
+        layer.ffn_exp_probs_b   = create_tensor(tn(LLM_TENSOR_FFN_EXP_PROBS_B, "bias", i), {n_expert}, TENSOR_NOT_REQUIRED);
+
+        layer.ffn_gate_shexp = create_tensor(tn(LLM_TENSOR_FFN_GATE_SHEXP, "weight", i), {n_embd, hparams.n_ff_shexp}, TENSOR_NOT_REQUIRED);
+        layer.ffn_up_shexp   = create_tensor(tn(LLM_TENSOR_FFN_UP_SHEXP,   "weight", i), {n_embd, hparams.n_ff_shexp}, TENSOR_NOT_REQUIRED);
+        layer.ffn_down_shexp = create_tensor(tn(LLM_TENSOR_FFN_DOWN_SHEXP, "weight", i), {hparams.n_ff_shexp, n_embd}, TENSOR_NOT_REQUIRED);
+
+        // NextN-specific tensors that define the MTP block.
+        layer.nextn.eh_proj          = create_tensor(tn(LLM_TENSOR_NEXTN_EH_PROJ,          "weight", i), { 2 * n_embd, n_embd }, eff_mtp_flags);
+        layer.nextn.enorm            = create_tensor(tn(LLM_TENSOR_NEXTN_ENORM,            "weight", i), { n_embd },              eff_mtp_flags);
+        layer.nextn.hnorm            = create_tensor(tn(LLM_TENSOR_NEXTN_HNORM,            "weight", i), { n_embd },              eff_mtp_flags);
+        layer.nextn.embed_tokens     = create_tensor(tn(LLM_TENSOR_NEXTN_EMBED_TOKENS,     "weight", i), { n_embd, n_vocab },     TENSOR_NOT_REQUIRED);
+        layer.nextn.shared_head_head = create_tensor(tn(LLM_TENSOR_NEXTN_SHARED_HEAD_HEAD, "weight", i), { n_embd, n_vocab },     TENSOR_NOT_REQUIRED);
+        layer.nextn.shared_head_norm = create_tensor(tn(LLM_TENSOR_NEXTN_SHARED_HEAD_NORM, "weight", i), { n_embd },              TENSOR_NOT_REQUIRED);
+    };
+
+    for (int i = 0; i < (int) n_main; ++i) {
+        load_block_trunk(i, trunk_flags);
+    }
+    // Only the first MTP block (i == n_main) is required at runtime — the
+    // single-block-MTP graph in build_arch_graph always uses that one.
+    // Trailing MTP blocks are loaded if present (so an un-pruned GGUF with
+    // all MTP layers still works) but tolerated when absent via the pruning
+    // path. See scripts/prune_step35_extra_mtp.py for the pruner.
+    for (int i = (int) n_main; i < n_layer; ++i) {
+        load_block_mtp(i, /*is_first_mtp=*/ i == (int) n_main);
     }
 }
 
 std::unique_ptr<llm_graph_context> llama_model_step35::build_arch_graph(const llm_graph_params & params) const {
+    if (params.gtype == LLM_GRAPH_TYPE_DECODER_MTP) {
+        return std::make_unique<graph_mtp>(*this, params);
+    }
     return std::make_unique<graph>(*this, params);
 }
 
@@ -111,7 +203,9 @@ llama_model_step35::graph::graph(const llama_model & model, const llm_graph_para
     auto        * inp_attn    = build_attn_inp_kv_iswa();
     ggml_tensor * inp_out_ids = build_inp_out_ids();
 
-    for (int il = 0; il < n_layer; ++il) {
+    // MTP/NextN layers are loaded as extra decoder blocks but not executed in the main pass.
+    const int n_transformer_layers = n_layer - (int) hparams.nextn_predict_layers;
+    for (int il = 0; il < n_transformer_layers; ++il) {
         ggml_tensor * inpSA = inpL;
 
         const uint32_t n_head_l    = hparams.n_head(il);
@@ -198,8 +292,8 @@ llama_model_step35::graph::graph(const llama_model & model, const llm_graph_para
             cb(cur, "attn_proj", il);
         }
 
-        if (il == n_layer - 1 && inp_out_ids) {
-            cur   = ggml_get_rows(ctx0,   cur, inp_out_ids);
+        if (il == n_transformer_layers - 1 && inp_out_ids && cparams.embeddings_pre_norm_masked) {
+            cur   = ggml_get_rows(ctx0, cur, inp_out_ids);
             inpSA = ggml_get_rows(ctx0, inpSA, inp_out_ids);
         }
 
@@ -257,6 +351,13 @@ llama_model_step35::graph::graph(const llama_model & model, const llm_graph_para
 
     cur = inpL;
 
+    cb(cur, "h_pre_norm", -1);
+    res->t_h_pre_norm = cur;
+
+    if (!cparams.embeddings_pre_norm_masked && inp_out_ids) {
+        cur = ggml_get_rows(ctx0, cur, inp_out_ids);
+    }
+
     cur = build_norm(cur, model.output_norm, nullptr, LLM_NORM_RMS, -1);
     cb(cur, "result_norm", -1);
     res->t_embd = cur;
@@ -267,3 +368,192 @@ llama_model_step35::graph::graph(const llama_model & model, const llm_graph_para
 
     ggml_build_forward_expand(gf, cur);
 }
+
+// LLM_GRAPH_TYPE_DECODER_MTP draft head for Step3p5 (MoE)
+llama_model_step35::graph_mtp::graph_mtp(const llama_model & model, const llm_graph_params & params)
+    : llm_graph_context(params) {
+    GGML_ASSERT(hparams.nextn_predict_layers > 0 && "STEP35 MTP requires nextn_predict_layers > 0");
+
+    // Single-block MTP only: always run the first trained MTP block (Qwen
+    // MTP / vLLM single-MTP-layer style). Multi-block round-robin proved to
+    // be a much deeper refactor than this PR justifies; the trailing MTP
+    // blocks are loaded with TENSOR_NOT_REQUIRED so pruned GGUFs (with just
+    // block 0) also work — see load_arch_tensors below and
+    // scripts/prune_step35_extra_mtp.py.
+    const int il       = (int) hparams.n_layer - (int) hparams.nextn_predict_layers;
+    const auto & layer = model.layers[il];
+
+    GGML_ASSERT(layer.nextn.eh_proj && "MTP block missing nextn.eh_proj");
+    GGML_ASSERT(layer.nextn.enorm   && "MTP block missing nextn.enorm");
+    GGML_ASSERT(layer.nextn.hnorm   && "MTP block missing nextn.hnorm");
+
+    const uint32_t n_head_l    = hparams.n_head(il);
+    const uint32_t n_head_kv_l = hparams.n_head_kv(il);
+
+    const float freq_base_l  = model.get_rope_freq_base(cparams, il);
+    const float freq_scale_l = model.get_rope_freq_scale(cparams, il);
+
+    auto inp = std::make_unique<llm_graph_input_embd>(hparams.n_embd);
+
+    inp->tokens = ggml_new_tensor_1d(ctx0, GGML_TYPE_I32, n_tokens);
+    ggml_set_input(inp->tokens);
+
+    inp->embd = ggml_new_tensor_2d(ctx0, GGML_TYPE_F32, hparams.n_embd, n_tokens);
+    ggml_set_input(inp->embd);
+    ggml_set_name(inp->embd, "mtp_h_input");
+
+    ggml_tensor * tok_embd_w = layer.nextn.embed_tokens ? layer.nextn.embed_tokens : model.tok_embd;
+
+    ggml_tensor * h_input  = inp->embd;
+    ggml_tensor * tok_embd = ggml_get_rows(ctx0, tok_embd_w, inp->tokens);
+    cb(tok_embd, "mtp_tok_embd", il);
+
+    res->add_input(std::move(inp));
+
+    ggml_tensor * inp_pos  = build_inp_pos();
+    auto        * inp_attn = build_attn_inp_kv_iswa();
+
+    ggml_tensor * h_norm = build_norm(h_input, layer.nextn.hnorm, nullptr, LLM_NORM_RMS, il);
+    cb(h_norm, "mtp_hnorm", il);
+
+    ggml_tensor * e_norm = build_norm(tok_embd, layer.nextn.enorm, nullptr, LLM_NORM_RMS, il);
+    cb(e_norm, "mtp_enorm", il);
+
+    ggml_tensor * concat = ggml_concat(ctx0, e_norm, h_norm, /*dim=*/ 0);
+    cb(concat, "mtp_concat", il);
+
+    ggml_tensor * cur = build_lora_mm(layer.nextn.eh_proj, concat);
+    cb(cur, "mtp_eh_proj", il);
+
+    ggml_tensor * inpSA = cur;
+
+    // mtp_block: full Step3p5 decoder layer (attention with optional head-wise gate, then MoE/dense FFN)
+    cur = build_norm(cur, layer.attn_norm, nullptr, LLM_NORM_RMS, il);
+    cb(cur, "mtp_attn_norm", il);
+
+    ggml_tensor * Qcur = build_lora_mm(layer.wq, cur, layer.wq_s);
+    ggml_tensor * Kcur = build_lora_mm(layer.wk, cur, layer.wk_s);
+    ggml_tensor * Vcur = build_lora_mm(layer.wv, cur, layer.wv_s);
+    cb(Qcur, "mtp_Qcur", il);
+    cb(Kcur, "mtp_Kcur", il);
+    cb(Vcur, "mtp_Vcur", il);
+
+    Qcur = ggml_reshape_3d(ctx0, Qcur, n_embd_head_k, n_head_l,    n_tokens);
+    Kcur = ggml_reshape_3d(ctx0, Kcur, n_embd_head_k, n_head_kv_l, n_tokens);
+    Vcur = ggml_reshape_3d(ctx0, Vcur, n_embd_head_v, n_head_kv_l, n_tokens);
+
+    if (layer.attn_q_norm) {
+        Qcur = build_norm(Qcur, layer.attn_q_norm, nullptr, LLM_NORM_RMS, il);
+        cb(Qcur, "mtp_Qcur_normed", il);
+    }
+    if (layer.attn_k_norm) {
+        Kcur = build_norm(Kcur, layer.attn_k_norm, nullptr, LLM_NORM_RMS, il);
+        cb(Kcur, "mtp_Kcur_normed", il);
+    }
+
+    const bool    is_swa       = hparams.is_swa(il);
+    ggml_tensor * rope_factors = is_swa ? nullptr : model.get_rope_factors(cparams, il);
+    const int64_t n_rot_l      = hparams.n_rot(il);
+
+    Qcur = ggml_rope_ext(
+        ctx0, Qcur, inp_pos, rope_factors,
+        n_rot_l, rope_type, n_ctx_orig, freq_base_l, freq_scale_l,
+        ext_factor, attn_factor, beta_fast, beta_slow);
+    Kcur = ggml_rope_ext(
+        ctx0, Kcur, inp_pos, rope_factors,
+        n_rot_l, rope_type, n_ctx_orig, freq_base_l, freq_scale_l,
+        ext_factor, attn_factor, beta_fast, beta_slow);
+    cb(Qcur, "mtp_Qcur_pos", il);
+    cb(Kcur, "mtp_Kcur_pos", il);
+
+    const float kq_scale = 1.0f / sqrtf(float(n_embd_head_k));
+    ggml_tensor * attn_out = build_attn(inp_attn,
+            nullptr, nullptr, nullptr,
+            Qcur, Kcur, Vcur, nullptr, nullptr, nullptr, kq_scale, il);
+    cb(attn_out, "mtp_attn_out", il);
+
+    // head-wise attention gate: sigmoid(g_proj(x))
+    if (layer.wqkv_gate) {
+        ggml_tensor * gate = build_lora_mm(layer.wqkv_gate, cur); // [n_head_l, n_tokens]
+        cb(gate, "mtp_attn_gate", il);
+
+        gate = ggml_sigmoid(ctx0, gate);
+        cb(gate, "mtp_attn_gate_sigmoid", il);
+
+        ggml_tensor * attn_3d = ggml_reshape_3d(ctx0, attn_out, n_embd_head_v, n_head_l, n_tokens);
+        ggml_tensor * gate_3d = ggml_reshape_3d(ctx0, gate,       1,           n_head_l, n_tokens);
+        cb(gate_3d, "mtp_attn_gate_3d", il);
+
+        attn_3d = ggml_mul(ctx0, attn_3d, gate_3d);
+        cb(attn_3d, "mtp_attn_gated_3d", il);
+
+        attn_out = ggml_reshape_2d(ctx0, attn_3d, n_embd_head_v * n_head_l, n_tokens);
+        cb(attn_out, "mtp_attn_gated", il);
+    }
+
+    cur = build_lora_mm(layer.wo, attn_out, layer.wo_s);
+    cb(cur, "mtp_attn_proj", il);
+
+    cur = ggml_add(ctx0, cur, inpSA);
+    cb(cur, "mtp_attn_residual", il);
+
+    ggml_tensor * ffn_inp = cur;
+    cur = build_norm(cur, layer.ffn_norm, nullptr, LLM_NORM_RMS, il);
+    cb(cur, "mtp_ffn_norm", il);
+
+    // FFN: dense MLP or MoE (mirrors trunk path)
+    if (layer.ffn_gate_inp == nullptr) {
+        cur = build_ffn(cur,
+                layer.ffn_up,   layer.ffn_up_b,   nullptr,
+                layer.ffn_gate, layer.ffn_gate_b, nullptr,
+                layer.ffn_down, layer.ffn_down_b, nullptr,
+                nullptr,
+                LLM_FFN_SILU, LLM_FFN_PAR, il);
+        cb(cur, "mtp_ffn_out", il);
+    } else {
+        ggml_tensor * moe_out = build_moe_ffn(cur,
+                layer.ffn_gate_inp,
+                layer.ffn_up_exps,
+                layer.ffn_gate_exps,
+                layer.ffn_down_exps,
+                layer.ffn_exp_probs_b,
+                n_expert, n_expert_used,
+                LLM_FFN_SILU, hparams.expert_weights_norm,
+                hparams.expert_weights_scale,
+                (llama_expert_gating_func_type) hparams.expert_gating_func,
+                il);
+        cb(moe_out, "mtp_ffn_moe_out", il);
+
+        ggml_tensor * sh_out = build_ffn(cur,
+                layer.ffn_up_shexp,   nullptr, nullptr,
+                layer.ffn_gate_shexp, nullptr, nullptr,
+                layer.ffn_down_shexp, nullptr, nullptr,
+                nullptr,
+                LLM_FFN_SILU, LLM_FFN_PAR, il);
+        cb(sh_out, "mtp_ffn_shared_out", il);
+
+        cur = ggml_add(ctx0, moe_out, sh_out);
+        cb(cur, "mtp_ffn_out", il);
+    }
+    cur = ggml_add(ctx0, cur, ffn_inp);
+    cb(cur, "mtp_post_ffn", il);
+
+    // Pre-norm hidden state: used by the AR draft loop to seed the next MTP step.
+    cb(cur, "h_pre_norm", -1);
+    res->t_h_pre_norm = cur;
+
+    ggml_tensor * head_norm_w = layer.nextn.shared_head_norm
+            ? layer.nextn.shared_head_norm
+            : model.output_norm;
+    GGML_ASSERT(head_norm_w && "STEP35 MTP: missing both nextn.shared_head_norm and output_norm");
+    cur = build_norm(cur, head_norm_w, nullptr, LLM_NORM_RMS, -1);
+    cb(cur, "mtp_shared_head_norm", -1);
+
+    ggml_tensor * head_w = layer.nextn.shared_head_head ? layer.nextn.shared_head_head : model.output;
+    GGML_ASSERT(head_w && "STEP35 MTP: missing LM head (nextn.shared_head_head or model.output)");
+    cur = build_lora_mm(head_w, cur);
+    cb(cur, "result_output", -1);
+
+    res->t_logits = cur;
+    ggml_build_forward_expand(gf, cur);
+}