common: support the DSpark sidecar resolution (#26458)

The dspark- files resolve like the other speculative sidecars: the
-hfd tag applies to them, a requested sidecar resolves without a full
model at the tag, and an explicit -md selection disables the discovery.
When no type is requested, dspark outranks dflash in the auto-selection
since its sidecar carries the extra Markov head.

common/arg.cpp

@@ -374,6 +374,10 @@ common_models_handler common_models_handler_init(const common_params & params, l
                                            params.speculative.types.end(),
                                            COMMON_SPECULATIVE_TYPE_DRAFT_EAGLE3) != params.speculative.types.end();
 
+    const bool spec_type_draft_dspark = std::find(params.speculative.types.begin(),
+                                           params.speculative.types.end(),
+                                           COMMON_SPECULATIVE_TYPE_DRAFT_DSPARK) != params.speculative.types.end();
+
     // only download mmproj if the current example is using it
     bool use_mmproj = false;
     for (const auto & ex : mmproj_examples) {
@@ -388,6 +392,7 @@ common_models_handler common_models_handler_init(const common_params & params, l
     opts.download_mtp    = spec_type_draft_mtp;
     opts.download_eagle3 = spec_type_draft_eagle3;
     opts.download_dflash = spec_type_draft_dflash;
+    opts.download_dspark = spec_type_draft_dspark;
     opts.download_mmproj = use_mmproj && !params.no_mmproj
                         && params.mmproj.path.empty() && params.mmproj.url.empty();
 
@@ -402,6 +407,7 @@ common_models_handler common_models_handler_init(const common_params & params, l
             opts_spec.download_mtp    = true;
             opts_spec.download_dflash = true;
             opts_spec.download_eagle3 = true;
+            opts_spec.download_dspark = true;
         }
         plan_spec = common_download_get_hf_plan(params.speculative.draft.mparams, opts_spec);
     }
@@ -544,12 +550,19 @@ void common_models_handler_apply(common_models_handler & handler, common_params
         plan_spec.mtp    = {};
         plan_spec.dflash = {};
         plan_spec.eagle3 = {};
+        plan_spec.dspark = {};
     }
 
     // infer the speculative type from the sidecar shipped by the draft repo when none is requested
     if (spec_types_is_default(params)) {
         if (!plan_spec.mtp.local_path.empty()) {
             params.speculative.types = { COMMON_SPECULATIVE_TYPE_DRAFT_MTP };
+            plan_spec.dspark = {};
+            plan_spec.dflash = {};
+            plan_spec.eagle3 = {};
+        } else if (!plan_spec.dspark.local_path.empty()) {
+            // dspark outranks dflash, its sidecar carries the extra Markov head
+            params.speculative.types = { COMMON_SPECULATIVE_TYPE_DRAFT_DSPARK };
             plan_spec.dflash = {};
             plan_spec.eagle3 = {};
         } else if (!plan_spec.dflash.local_path.empty()) {
@@ -563,7 +576,8 @@ void common_models_handler_apply(common_models_handler & handler, common_params
     // when a sidecar type is requested, the draft repo resolves to its sidecar instead of a full model
     const bool spec_sidecar_found = !plan_spec.mtp.local_path.empty() ||
                                     !plan_spec.dflash.local_path.empty() ||
-                                    !plan_spec.eagle3.local_path.empty();
+                                    !plan_spec.eagle3.local_path.empty() ||
+                                    !plan_spec.dspark.local_path.empty();
     if (!plan_spec.mtp.local_path.empty() && !had_spec_url) {
         tasks.emplace_back(plan_spec.mtp, opts, [&]() {
             // only use the discovered MTP head when no draft path is set yet
@@ -594,6 +608,16 @@ void common_models_handler_apply(common_models_handler & handler, common_params
             }
         });
     }
+    if (!plan_spec.dspark.local_path.empty() && !had_spec_url) {
+        tasks.emplace_back(plan_spec.dspark, opts, [&]() {
+            // only use the discovered DSpark sidecar when no draft path is set yet
+            if (params.speculative.draft.mparams.path.empty()) {
+                params.speculative.draft.mparams.path = hf_cache::finalize_file(plan_spec.dspark);
+            } else {
+                hf_cache::finalize_file(plan_spec.dspark);
+            }
+        });
+    }
 
     // a wired draft sidecar counts as an explicit draft for the main plan fallback below
     if (spec_sidecar_found) {
@@ -649,6 +673,16 @@ void common_models_handler_apply(common_models_handler & handler, common_params
             }
         });
     }
+    if (!plan.dspark.local_path.empty() && !had_spec_url) {
+        tasks.emplace_back(plan.dspark, opts, [&]() {
+            // only fall back to the discovered DSpark sidecar when no draft was explicitly provided
+            if (params.speculative.draft.mparams.empty()) {
+                params.speculative.draft.mparams.path = hf_cache::finalize_file(plan.dspark);
+            } else {
+                hf_cache::finalize_file(plan.dspark);
+            }
+        });
+    }
     if (!plan.preset.local_path.empty()) {
         tasks.emplace_back(plan.preset, opts, [&]() {
             // if HF repo is a preset repo, we simply run server in router mode with the preset.ini file

common/download.cpp

@@ -656,6 +656,12 @@ static hf_cache::hf_file find_best_dflash(const hf_cache::hf_files & files,
     return find_best_sibling(files, model, "dflash-", tag);
 }
 
+static hf_cache::hf_file find_best_dspark(const hf_cache::hf_files & files,
+                                          const std::string        & model,
+                                          const std::string        & tag = "") {
+    return find_best_sibling(files, model, "dspark-", tag);
+}
+
 static bool gguf_filename_is_model(const std::string & filepath) {
     if (!string_ends_with(filepath, ".gguf")) {
         return false;
@@ -670,7 +676,8 @@ static bool gguf_filename_is_model(const std::string & filepath) {
            filename.find("imatrix") == std::string::npos &&
            filename.find("mtp-")    == std::string::npos &&
            filename.find("eagle3-") == std::string::npos &&
-           filename.find("dflash-") == std::string::npos;
+           filename.find("dflash-") == std::string::npos &&
+           filename.find("dspark-") == std::string::npos;
 }
 
 static hf_cache::hf_file find_best_model(const hf_cache::hf_files & files,
@@ -763,7 +770,7 @@ common_download_hf_plan common_download_get_hf_plan(const common_params_model &
     } else {
         primary = find_best_model(all, tag);
         // a requested sidecar can resolve on its own, without a full model of the same tag
-        if (primary.path.empty() && !opts.download_mtp && !opts.download_dflash && !opts.download_eagle3) {
+        if (primary.path.empty() && !opts.download_mtp && !opts.download_dflash && !opts.download_eagle3 && !opts.download_dspark) {
             LOG_ERR("%s: no GGUF files found in repository %s\n", __func__, repo.c_str());
             list_available_gguf_files(all);
             return plan;
@@ -787,9 +794,12 @@ common_download_hf_plan common_download_get_hf_plan(const common_params_model &
     if (opts.download_eagle3) {
         plan.eagle3 = find_best_eagle3(all, primary.path, tag);
     }
+    if (opts.download_dspark) {
+        plan.dspark = find_best_dspark(all, primary.path, tag);
+    }
 
     if (primary.path.empty() &&
-        plan.mtp.local_path.empty() && plan.dflash.local_path.empty() && plan.eagle3.local_path.empty()) {
+        plan.mtp.local_path.empty() && plan.dflash.local_path.empty() && plan.eagle3.local_path.empty() && plan.dspark.local_path.empty()) {
         LOG_ERR("%s: no GGUF files found in repository %s\n", __func__, repo.c_str());
         list_available_gguf_files(all);
     }
@@ -967,7 +977,8 @@ std::vector<common_cached_model_info> common_list_cached_models() {
             split.prefix.find("mmproj")  != std::string::npos ||
             split.prefix.find("mtp-")    != std::string::npos ||
             split.prefix.find("eagle3-") != std::string::npos ||
-            split.prefix.find("dflash-") != std::string::npos) {
+            split.prefix.find("dflash-") != std::string::npos ||
+            split.prefix.find("dspark-") != std::string::npos) {
             continue;
         }
         if (seen.insert(f.repo_id + ":" + split.tag).second) {

common/download.h

@@ -59,6 +59,7 @@ struct common_download_opts {
     bool download_mtp     = false;
     bool download_eagle3  = false;
     bool download_dflash  = false;
+    bool download_dspark  = false;
     common_download_callback * callback = nullptr;
 };
 
@@ -110,6 +111,7 @@ struct common_download_hf_plan {
     hf_cache::hf_file mtp;
     hf_cache::hf_file eagle3;
     hf_cache::hf_file dflash;
+    hf_cache::hf_file dspark;
     hf_cache::hf_file preset; // if set, only this file is downloaded
 };
 common_download_hf_plan common_download_get_hf_plan(const common_params_model & model, const common_download_opts & opts);