model: add DSpark support for Nemotron3.5 (#27804)

* model: add DSpark support for Nemotron3.5

* Update src/models/dflash.cpp

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@huggingface.co>

---------

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@huggingface.co>
Co-authored-by: Xuan Son Nguyen <son@huggingface.co>

common/speculative.cpp

@@ -935,6 +935,9 @@ struct common_speculative_impl_draft_dflash : public common_speculative_impl {
     // dspark speculators
     bool sample_from_anchor = true;
 
+    // block-internal attention
+    bool causal_attn = false;
+
     const int32_t * target_layer_ids   = nullptr; // model_dft's extract layer indices
     uint32_t        target_layer_ids_n = 0;
 
@@ -972,12 +975,25 @@ struct common_speculative_impl_draft_dflash : public common_speculative_impl {
             if (llama_model_meta_val_str(model_dft, "dflash.sample_from_anchor", buf, sizeof(buf)) >= 0) {
                 sample_from_anchor = std::strcmp(buf, "true") == 0;
             }
+            if (llama_model_meta_val_str(model_dft, "dflash.attention.causal", buf, sizeof(buf)) >= 0) {
+                causal_attn = std::strcmp(buf, "true") == 0;
+            }
         }
 
         selector_top_k = llama_model_dflash_selector_top_k(model_dft);
         is_dflash2     = selector_top_k > 0;
         mask_token_id = llama_vocab_mask(llama_model_get_vocab(model_dft));
 
+        if (is_dspark && this->params.p_min > 0.0f) {
+            char buf[16] = {};
+            const bool has_conf =
+                llama_model_meta_val_str(model_dft, "dflash.has_confidence_head", buf, sizeof(buf)) < 0 ||
+                std::strcmp(buf, "true") == 0;
+            if (!has_conf) {
+                throw std::runtime_error("DSpark draft has no confidence head: please set --spec-draft-p-min 0");
+            }
+        }
+
         LOG_INF("%s: adding speculative implementation '%s'\n", __func__, common_speculative_type_to_str(type).c_str());
         LOG_INF("%s: - n_max=%d, n_min=%d, p_min=%.2f\n", __func__, this->params.n_max, this->params.n_min, this->params.p_min);
         LOG_INF("%s: - block_size=%d, mask_token_id=%d, n_extract=%u, sample_from_anchor=%s\n", __func__,
@@ -1036,7 +1052,7 @@ struct common_speculative_impl_draft_dflash : public common_speculative_impl {
 
         // DFlash2 reads its selector lattice from h_nextn and never consumes raw logits.
         llama_set_embeddings_nextn(ctx_dft, true, /*masked*/ !is_dflash2);
-        llama_set_causal_attn(ctx_dft, false); // DFlash needs non-causal attention
+        llama_set_causal_attn(ctx_dft, causal_attn); // DFlash needs non-causal attention unless the model says otherwise
     }
 
     ~common_speculative_impl_draft_dflash() override {

conversion/qwen.py

@@ -709,14 +709,20 @@ class DFlashModel(Qwen3Model):
             extract_layer_ids = [i + 1 for i in target_layer_ids]
             self.gguf_writer.add_target_layers(extract_layer_ids)
 
-        use_sliding_window = self.hparams.get("use_sliding_window", False)
-        sliding_window = self.hparams.get("sliding_window")
+        use_sliding_window = self.hparams.get("use_sliding_window", False) or dflash_config.get("use_swa", False)
+        sliding_window = dflash_config.get("swa_window_size") or self.hparams.get("sliding_window")
         layer_types = self.hparams.get("layer_types")
         if use_sliding_window and sliding_window and layer_types:
             is_swa = [lt == "sliding_attention" for lt in layer_types]
             self.gguf_writer.add_sliding_window(sliding_window)
             self.gguf_writer.add_sliding_window_pattern(is_swa)
 
+        causal = self.hparams.get("is_causal")
+        if causal is None:
+            causal = dflash_config.get("causal")
+        if causal is not None:
+            self.gguf_writer.add_causal_attention(bool(causal))
+
         # M-RoPE target: the draft ropes on the temporal dim only, so write
         # degenerate sections [n_rot/2, 0, 0, 0]
         if self._target_uses_mrope():
@@ -737,6 +743,8 @@ class DFlashModel(Qwen3Model):
         name, gen = item
         if not name.startswith("model."):
             name = "model." + name
+        if "sink" in name and not name.endswith(".weight"):
+            name += ".weight"
         return super().filter_tensors((name, gen))
 
     _ROPE_PERMUTE_SUFFIXES = (
@@ -815,6 +823,10 @@ class DSparkModel(DFlashModel):
         super().set_gguf_parameters()
         self.gguf_writer.add_sample_from_anchor(self._sample_from_anchor)
 
+        # confidence head is optional: vanilla-markov exports ship without it
+        has_conf = any("confidence_head.proj" in name for name in self.model_tensors)
+        self.gguf_writer.add_has_confidence_head(has_conf)
+
     @classmethod
     def filter_tensors(cls, item: tuple[str, Callable[[], Tensor]]) -> tuple[str, Callable[[], Tensor]] | None:
         if item[0] == "t2d":  # not used at runtime
@@ -833,7 +845,7 @@ class DSparkModel(DFlashModel):
             self._d2t = data_torch
             return
 
-        if self._n_vocab_draft == self.hparams["vocab_size"] and name.endswith(("embed_tokens.weight", "lm_head.weight")):
+        if self._n_vocab_draft == self.hparams["vocab_size"] and name.endswith("lm_head.weight"):
             return
 
         # interleaved-rope checkpoints (rope_is_neox_style = false) -> NeoX layout: per head, even dims first then odd

gguf-py/gguf/constants.py

@@ -167,6 +167,7 @@ class Keys:
         SELECTOR_RANK                     = "{arch}.selector_rank"
         SELECTOR_TOP_K                    = "{arch}.selector_top_k"
         SAMPLE_FROM_ANCHOR                = "{arch}.sample_from_anchor"
+        HAS_CONFIDENCE_HEAD               = "{arch}.has_confidence_head"
         NORM_BEFORE_RESIDUAL              = "{arch}.norm_before_residual"
         NORM_BEFORE_FC                    = "{arch}.norm_before_fc"
 

gguf-py/gguf/gguf_writer.py

@@ -1008,6 +1008,9 @@ class GGUFWriter:
     def add_sample_from_anchor(self, value: bool) -> None:
         self.add_bool(Keys.LLM.SAMPLE_FROM_ANCHOR.format(arch=self.arch), value)
 
+    def add_has_confidence_head(self, value: bool) -> None:
+        self.add_bool(Keys.LLM.HAS_CONFIDENCE_HEAD.format(arch=self.arch), value)
+
     def add_target_layers(self, value: Sequence[int]) -> None:
         self.add_array(Keys.LLM.TARGET_LAYERS.format(arch=self.arch), value)
 

src/llama-model.h

@@ -672,6 +672,7 @@ struct llama_model {
     // dspark
     struct ggml_tensor * dspark_markov_w1   = nullptr;
     struct ggml_tensor * dspark_markov_w2   = nullptr;
+    struct ggml_tensor * dspark_markov_w2_s = nullptr;
     struct ggml_tensor * dspark_conf_proj   = nullptr;
     struct ggml_tensor * dspark_conf_proj_b = nullptr;
 

src/models/dflash.cpp

@@ -115,10 +115,11 @@ void llama_model_dflash::load_arch_tensors(llama_model_loader &) {
     if (markov_meta) {
         const int64_t dspark_markov_rank = markov_meta->ne[0];
 
-        dspark_markov_w1 = create_tensor(tn(LLM_TENSOR_DSPARK_MARKOV_W1, "weight"), { dspark_markov_rank, n_vocab }, 0);
-        dspark_markov_w2 = create_tensor(tn(LLM_TENSOR_DSPARK_MARKOV_W2, "weight"), { dspark_markov_rank, n_vocab_draft }, 0);
+        dspark_markov_w1   = create_tensor(tn(LLM_TENSOR_DSPARK_MARKOV_W1, "weight"), { dspark_markov_rank, n_vocab }, 0);
+        dspark_markov_w2   = create_tensor(tn(LLM_TENSOR_DSPARK_MARKOV_W2, "weight"), { dspark_markov_rank, n_vocab_draft }, 0);
+        dspark_markov_w2_s = create_tensor(tn(LLM_TENSOR_DSPARK_MARKOV_W2, "scale"),  { 1 }, TENSOR_NOT_REQUIRED);
 
-        dspark_conf_proj   = create_tensor(tn(LLM_TENSOR_DSPARK_CONF_PROJ, "weight"), { n_embd + dspark_markov_rank, 1 }, 0);
+        dspark_conf_proj   = create_tensor(tn(LLM_TENSOR_DSPARK_CONF_PROJ, "weight"), { n_embd + dspark_markov_rank, 1 }, TENSOR_NOT_REQUIRED);
         dspark_conf_proj_b = create_tensor(tn(LLM_TENSOR_DSPARK_CONF_PROJ, "bias"),   { 1 },             TENSOR_NOT_REQUIRED);
 
         LLAMA_LOG_INFO("%s: DFlash with DSpark markov head (rank = %lld)\n", __func__, (long long) dspark_markov_rank);
@@ -219,6 +220,9 @@ void llama_model_dflash::load_arch_tensors(llama_model_loader &) {
         layer.attn_q_norm = create_tensor(tn(LLM_TENSOR_ATTN_Q_NORM, "weight", i), { n_embd_head_k }, 0);
         layer.attn_k_norm = create_tensor(tn(LLM_TENSOR_ATTN_K_NORM, "weight", i), { n_embd_head_k }, 0);
 
+        // optional per-head attention sinks (e.g. Nemotron DSpark)
+        layer.attn_sinks = create_tensor(tn(LLM_TENSOR_ATTN_SINKS, "weight", i), { n_head }, TENSOR_NOT_REQUIRED);
+
         layer.ffn_norm = create_tensor(tn(LLM_TENSOR_FFN_NORM, "weight", i), { n_embd }, 0);
         layer.ffn_gate = create_tensor(tn(LLM_TENSOR_FFN_GATE, "weight", i), { n_embd, n_ff }, 0);
         layer.ffn_down = create_tensor(tn(LLM_TENSOR_FFN_DOWN, "weight", i), { n_ff, n_embd }, 0);
@@ -290,7 +294,10 @@ static void build_dspark_markov_head(llm_graph_context & g, const llama_model &
 
     ggml_tensor * w1 = model.dspark_markov_w1;
     ggml_tensor * w2 = model.dspark_markov_w2;
-    GGML_ASSERT(w1 && w2 && model.dspark_conf_proj && "DSpark markov/confidence weights not loaded");
+    GGML_ASSERT(w1 && w2 && "DSpark markov weights not loaded");
+
+    // confidence head is optional
+    const bool has_conf = model.dspark_conf_proj != nullptr;
 
     ggml_tensor * base = res->t_logits; // [n_vocab, n_tokens]
     const int64_t n_vocab = base->ne[0];
@@ -321,23 +328,22 @@ static void build_dspark_markov_head(llm_graph_context & g, const llama_model &
     ggml_tensor * prev = ggml_view_2d(ctx0, tokens, 1, n_blocks, token_stride, 0);
     prev = ggml_cont_1d(ctx0, prev, n_blocks);
 
-    // confidence head input: predicts per-position acceptance
-    ggml_tensor * conf_inp = res->t_embd; // [n_embd, n_tok]
-
     ggml_tensor * cat      = nullptr;
     ggml_tensor * cat_conf = nullptr;
 
     if (!sample_from_anchor) {
         // bonus anchor slot: pass the logits through unbiased, pad the (unread) confidence column
-        cat      = ggml_cont(ctx0, ggml_view_2d(ctx0, base, n_vocab, n_blocks, base_stride, 0));
-        cat_conf = ggml_sigmoid(ctx0, ggml_cont(ctx0, ggml_view_2d(ctx0, base, 1, n_blocks, base_stride, 0)));
+        cat = ggml_cont(ctx0, ggml_view_2d(ctx0, base, n_vocab, n_blocks, base_stride, 0));
+        if (has_conf) {
+            cat_conf = ggml_sigmoid(ctx0, ggml_cont(ctx0, ggml_view_2d(ctx0, base, 1, n_blocks, base_stride, 0)));
+        }
     }
 
     // TODO: the in-graph chain is greedy (argmax); sampling params affect only the final
     //       token pick, not the Markov conditioning path
     for (int64_t i = i_draft_beg; i < block_drafts; ++i) {
-        ggml_tensor * w1_prev = ggml_get_rows(ctx0, w1, prev);   // [R, n_blocks]
-        ggml_tensor * bias    = ggml_mul_mat(ctx0, w2, w1_prev); // [n_vocab_draft, n_blocks]
+        ggml_tensor * w1_prev = ggml_get_rows(ctx0, w1, prev);                          // [R, n_blocks]
+        ggml_tensor * bias    = g.build_lora_mm(w2, w1_prev, model.dspark_markov_w2_s); // [n_vocab_draft, n_blocks]
         if (model.d2t) {
             // reduced draft vocab: scatter the bias to the target rows (base is -inf on the others)
             const int64_t n_draft_vocab = bias->ne[0];
@@ -354,17 +360,21 @@ static void build_dspark_markov_head(llm_graph_context & g, const llama_model &
 
         cat = cat ? ggml_concat(ctx0, cat, col, 1) : col;
 
-        // conf(i) = sigmoid(conf_proj . [conf_inp(i); markov_w1[prev(i)]] + b)  -- [1, n_blocks]
-        ggml_tensor * conf_inp_i = ggml_view_2d(ctx0, conf_inp, conf_inp->ne[0], n_blocks,
-                                                (size_t) block_drafts * conf_inp->nb[1], i*conf_inp->nb[1]);
-        ggml_tensor * feat = ggml_concat(ctx0, ggml_cont(ctx0, conf_inp_i), w1_prev, 0);
-        ggml_tensor * conf = ggml_mul_mat(ctx0, model.dspark_conf_proj, feat);
-        if (model.dspark_conf_proj_b) {
-            conf = ggml_add(ctx0, conf, model.dspark_conf_proj_b);
-        }
-        conf = ggml_sigmoid(ctx0, conf);
+        if (has_conf) {
+            // confidence head input: predicts per-position acceptance
+            ggml_tensor * conf_inp   = res->t_embd; // [n_embd, n_tok]
+            // conf(i) = sigmoid(conf_proj . [conf_inp(i); markov_w1[prev(i)]] + b)  -- [1, n_blocks]
+            ggml_tensor * conf_inp_i = ggml_view_2d(ctx0, conf_inp, conf_inp->ne[0], n_blocks,
+                                                    (size_t) block_drafts * conf_inp->nb[1], i*conf_inp->nb[1]);
+            ggml_tensor * feat = ggml_concat(ctx0, ggml_cont(ctx0, conf_inp_i), w1_prev, 0);
+            ggml_tensor * conf = ggml_mul_mat(ctx0, model.dspark_conf_proj, feat);
+            if (model.dspark_conf_proj_b) {
+                conf = ggml_add(ctx0, conf, model.dspark_conf_proj_b);
+            }
+            conf = ggml_sigmoid(ctx0, conf);
 
-        cat_conf = cat_conf ? ggml_concat(ctx0, cat_conf, conf, 1) : conf;
+            cat_conf = cat_conf ? ggml_concat(ctx0, cat_conf, conf, 1) : conf;
+        }
 
         if (i + 1 < block_drafts) {
             prev = ggml_argmax(ctx0, col);
@@ -376,7 +386,7 @@ static void build_dspark_markov_head(llm_graph_context & g, const llama_model &
     out = ggml_cont(ctx0, ggml_permute(ctx0, out, 0, 2, 1, 3)); // [n_vocab, block_drafts, n_blocks]
     out = ggml_reshape_2d(ctx0, out, n_vocab, n_tok);
 
-    {
+    if (has_conf) {
         ggml_tensor * conf = ggml_reshape_3d(ctx0, cat_conf, 1, n_blocks, block_drafts);
         conf = ggml_cont(ctx0, ggml_permute(ctx0, conf, 0, 2, 1, 3));
         conf = ggml_reshape_2d(ctx0, conf, 1, n_tok);
@@ -707,8 +717,8 @@ llama_model_dflash::graph<false>::graph(const llama_model & model, const llm_gra
 
         // cache-aware, non-causal attention
         ggml_tensor * cur = use_iswa
-            ? build_attn(inp_attn_iswa, layer.wo, NULL, NULL, Qcur, Kcur, Vcur, nullptr, nullptr, nullptr, kq_scale, il)
-            : build_attn(inp_attn,      layer.wo, NULL, NULL, Qcur, Kcur, Vcur, nullptr, nullptr, nullptr, kq_scale, il);
+            ? build_attn(inp_attn_iswa, layer.wo, NULL, NULL, Qcur, Kcur, Vcur, nullptr, layer.attn_sinks, nullptr, kq_scale, il)
+            : build_attn(inp_attn,      layer.wo, NULL, NULL, Qcur, Kcur, Vcur, nullptr, layer.attn_sinks, nullptr, kq_scale, il);
 
         if (attn_dynamic) {
             cur = build_dflash2_conv(*this, cur, attn_dynamic, layer.dflash_attn_conv_base, 1);