Add Tool Calling and Reasoning Token Metadata to genai_config.json with Fallback Map

src/config.cpp

@@ -1545,6 +1545,34 @@ void ClearDecoderProviderOptionsHardwareVendorId(Config& config, std::string_vie
   }
 }
 
+struct ToolCalling_Element : JSON::Element {
+  explicit ToolCalling_Element(Config::ToolCalling& v) : v_{v} {}
+
+  void OnValue(std::string_view name, JSON::Value value) override {
+    if (name == "tool_call_start_token") {
+      v_.tool_call_start_token = JSON::Get<std::string_view>(value);
+    } else if (name == "tool_call_end_token") {
+      v_.tool_call_end_token = JSON::Get<std::string_view>(value);
+    }
+  }
+
+  Config::ToolCalling& v_;
+};
+
+struct Reasoning_Element : JSON::Element {
+  explicit Reasoning_Element(Config::Reasoning& v) : v_{v} {}
+
+  void OnValue(std::string_view name, JSON::Value value) override {
+    if (name == "reasoning_start_token") {
+      v_.reasoning_start_token = JSON::Get<std::string_view>(value);
+    } else if (name == "reasoning_end_token") {
+      v_.reasoning_end_token = JSON::Get<std::string_view>(value);
+    }
+  }
+
+  Config::Reasoning& v_;
+};
+
 struct Root_Element : JSON::Element {
   explicit Root_Element(Config& config) : config_{config} {}
 
@@ -1556,13 +1584,17 @@ struct Root_Element : JSON::Element {
     if (name == "model") return model_element_;
     if (name == "search") return search_element_;
     if (name == "engine") return engine_element_;
+    if (name == "tool_calling") return tool_calling_element_;
+    if (name == "reasoning") return reasoning_element_;
     throw JSON::unknown_value_error{};
   }
 
   Config& config_;
   Model_Element model_element_{config_.model};
   Search_Element search_element_{config_.search};
   Engine_Element engine_element_{config_.engine};
+  ToolCalling_Element tool_calling_element_{config_.tool_calling};
+  Reasoning_Element reasoning_element_{config_.reasoning};
 };
 
 struct RootObject_Element : JSON::Element {

src/config.h

@@ -451,6 +451,16 @@ struct Config {
     std::optional<StaticBatching> static_batching;  // Static batching settings
   } engine;                                         // Engine settings
 
+  struct ToolCalling {
+    std::string tool_call_start_token;  // e.g., "<tool_call>"
+    std::string tool_call_end_token;    // e.g., "</tool_call>"
+  } tool_calling;
+
+  struct Reasoning {
+    std::string reasoning_start_token;  // e.g., "<think>"
+    std::string reasoning_end_token;    // e.g., "</think>"
+  } reasoning;
+
   void AddMapping(const std::string& nominal_name, const std::string& graph_name);
   // Returns graph name and true if the nominal name is found in the mapping
   // otherwise returns the nominal name and false

src/models/model.cpp

@@ -6,11 +6,13 @@
 #include <algorithm>
 #include <array>
 #include <climits>
+#include <functional>
 #include <random>
 #include <set>
 #include <string>
 #include <string_view>
 #include <thread>
+#include <unordered_map>
 
 #include "../generators.h"
 #include "../search.h"
@@ -285,6 +287,11 @@ Tokenizer::Tokenizer(Config& config) : bos_token_id_{config.model.bos_token_id},
   // Resolve tokenizer_dir (may be empty, relative, absolute, or "package:"-scheme).
   const fs::path tokenizer_dir = config.ResolvePath(config.model.tokenizer_dir);
   CheckResult(OrtxCreateTokenizerWithOptions(tokenizer_.Address(), tokenizer_dir.string().c_str(), keys, values, 2));
+
+  // TODO: Once ORT Extensions supports an "additional_special_tokens" option, pass the generation
+  // tags (tool_calling/reasoning tokens) here so that models which don't already mark them as
+  // special in their tokenizer_config.json will still get correct skip_special_tokens behavior.
+  // This is needed for the FL SDK's dual-stream special token detection in OnnxChatGenerator::Decode().
 }
 
 std::unique_ptr<TokenizerStream> Tokenizer::CreateStream() const {
@@ -817,6 +824,51 @@ bool Model::IsPruned() const {
   return logits_shape[1] == 1;
 }
 
+namespace {
+
+// Fallback map for models whose genai_config.json doesn't yet have tool_calling/reasoning sections.
+// Keyed by model.type string from genai_config.json.
+// Inner map: tag_name -> value
+const std::string* GetFallbackTag(const std::string& model_type, const std::string& tag_name) {
+  static const std::unordered_map<std::string, std::unordered_map<std::string, std::string>> fallback_map = {
+      {"qwen2", {{"tool_call_start", "<tool_call>"}, {"tool_call_end", "</tool_call>"}}},
+      {"qwen3", {{"tool_call_start", "<tool_call>"}, {"tool_call_end", "</tool_call>"}, {"reasoning_start", "<think>"}, {"reasoning_end", "</think>"}}},
+      {"phi3", {{"tool_call_start", "<tool_call>"}, {"tool_call_end", "</tool_call>"}}},
+      {"gptoss", {{"tool_call_start", "<|start|>"}, {"tool_call_end", "<|call|>"}}},
+  };
+  auto type_it = fallback_map.find(model_type);
+  if (type_it == fallback_map.end()) return nullptr;
+  auto tag_it = type_it->second.find(tag_name);
+  if (tag_it == type_it->second.end()) return nullptr;
+  return &tag_it->second;
+}
+
+}  // namespace
+
+const std::string& Model::GetTag(const std::string& tag_name) const {
+  // Check config first (tool_calling and reasoning sections)
+  static const std::unordered_map<std::string, std::function<const std::string&(const Config&)>> config_accessors = {
+      {"tool_call_start", [](const Config& c) -> const std::string& { return c.tool_calling.tool_call_start_token; }},
+      {"tool_call_end", [](const Config& c) -> const std::string& { return c.tool_calling.tool_call_end_token; }},
+      {"reasoning_start", [](const Config& c) -> const std::string& { return c.reasoning.reasoning_start_token; }},
+      {"reasoning_end", [](const Config& c) -> const std::string& { return c.reasoning.reasoning_end_token; }},
+  };
+
+  auto accessor_it = config_accessors.find(tag_name);
+  if (accessor_it != config_accessors.end()) {
+    const std::string& config_val = accessor_it->second(*config_);
+    if (!config_val.empty())
+      return config_val;
+  }
+
+  // Fallback to model-type-based map
+  const auto* fallback = GetFallbackTag(config_->model.type, tag_name);
+  if (fallback) return *fallback;
+
+  static const std::string empty;
+  return empty;
+}
+
 std::shared_ptr<Model> CreateModel(OrtEnv& ort_env, const char* config_path, const RuntimeSettings* settings /*= nullptr*/) {
   std::string config_overlay;
   if (settings) {

src/models/model.h

@@ -163,6 +163,11 @@ struct Model : std::enable_shared_from_this<Model>, LeakChecked<Model>, External
 
   bool IsPruned() const;
 
+  // Generic tag accessor (reads from config with model-type fallback).
+  // Known tag names: "tool_call_start", "tool_call_end", "reasoning_start", "reasoning_end".
+  // Returns the tag value, or an empty string if the model doesn't define the tag.
+  const std::string& GetTag(const std::string& tag_name) const;
+
   std::unique_ptr<Config> config_;
   std::unique_ptr<OrtSessionOptions> session_options_;
 

src/ort_genai.h

@@ -258,6 +258,12 @@ struct OgaModel : OgaAbstract {
     return p;
   }
 
+  OgaString GetTag(const char* tag_name) const {
+    const char* p;
+    OgaCheckResult(OgaModelGetTag(this, tag_name, &p));
+    return p;
+  }
+
   static void operator delete(void* p) { OgaDestroyModel(reinterpret_cast<OgaModel*>(p)); }
 };
 

src/ort_genai_c.cpp

@@ -378,6 +378,13 @@ OgaResult* OGA_API_CALL OgaModelGetDeviceType(const OgaModel* model, const char*
   OGA_CATCH
 }
 
+OgaResult* OGA_API_CALL OgaModelGetTag(const OgaModel* model, const char* tag_name, const char** out) {
+  OGA_TRY
+  *out = AllocOgaString(model->GetTag(tag_name).c_str());
+  return nullptr;
+  OGA_CATCH
+}
+
 OgaResult* OGA_API_CALL OgaCreateGeneratorParams(const OgaModel* model, OgaGeneratorParams** out) {
   OGA_TRY
   auto params = std::make_shared<Generators::GeneratorParams>(*model);

src/ort_genai_c.h

@@ -406,6 +406,19 @@ OGA_EXPORT OgaResult* OGA_API_CALL OgaModelGetType(const OgaModel* model, const
  */
 OGA_EXPORT OgaResult* OGA_API_CALL OgaModelGetDeviceType(const OgaModel* model, const char** out);
 
+/**
+ * \brief Returns a tag value for this model by name.
+ *
+ * Known tag names: "tool_call_start", "tool_call_end", "reasoning_start", "reasoning_end".
+ * Returns an empty string if the model doesn't define the requested tag.
+ *
+ * \param[in] model The model to query.
+ * \param[in] tag_name The name of the tag to retrieve.
+ * \param[out] out The tag value string. Must be destroyed with OgaDestroyString.
+ * \return OgaResult containing the error message if the call failed.
+ */
+OGA_EXPORT OgaResult* OGA_API_CALL OgaModelGetTag(const OgaModel* model, const char* tag_name, const char** out);
+
 /**
  * \brief Destroys the given config
  * \param[in] config The config to be destroyed.

test/c_api_tests.cpp

@@ -1816,3 +1816,81 @@ TEST(CAPITests, ParakeetTdtTranscribeLong) {
   auto transcription = RunParakeetTdt(PARAKEET_TDT_AUDIO_TEDLIUM);
   EXPECT_FALSE(transcription.empty());
 }
+
+// Test tool_calling and reasoning config parsing and fallback map
+TEST(CAPITests, Tags_Fallback) {
+  // tiny-random-gpt2 model has type "gpt2" which is NOT in the fallback map → empty tags
+  auto model = OgaModel::Create(MODEL_PATH "hf-internal-testing/tiny-random-gpt2-fp32");
+
+  auto tool_start = model->GetTag("tool_call_start");
+  auto tool_end = model->GetTag("tool_call_end");
+  auto reasoning_start = model->GetTag("reasoning_start");
+  auto reasoning_end = model->GetTag("reasoning_end");
+
+  EXPECT_STREQ(static_cast<const char*>(tool_start), "");
+  EXPECT_STREQ(static_cast<const char*>(tool_end), "");
+  EXPECT_STREQ(static_cast<const char*>(reasoning_start), "");
+  EXPECT_STREQ(static_cast<const char*>(reasoning_end), "");
+}
+
+TEST(CAPITests, Tags_FromConfig) {
+  // Create a temporary model directory with tool_calling and reasoning sections
+  auto temp_dir = std::filesystem::temp_directory_path() / "oga_test_tool_tags";
+  std::filesystem::create_directories(temp_dir);
+
+  // Copy minimal model files from tiny-random-gpt2
+  std::string src_dir = MODEL_PATH "hf-internal-testing/tiny-random-gpt2-fp32";
+  for (const auto& entry : std::filesystem::directory_iterator(src_dir)) {
+    if (entry.path().filename() != "genai_config.json") {
+      std::filesystem::copy_file(entry.path(), temp_dir / entry.path().filename(),
+                                 std::filesystem::copy_options::overwrite_existing);
+    }
+  }
+
+  // Write genai_config.json with tool_calling and reasoning sections
+  {
+    std::ofstream f((temp_dir / "genai_config.json").string());
+    f << R"({
+  "model": {
+    "type": "gpt2",
+    "pad_token_id": 98,
+    "bos_token_id": 98,
+    "eos_token_id": 98,
+    "vocab_size": 1000,
+    "context_length": 512,
+    "decoder": {
+      "session_options": { "provider_options": [] },
+      "filename": "past.onnx",
+      "num_key_value_heads": 4,
+      "head_size": 8,
+      "num_hidden_layers": 5,
+      "inputs": { "past_names": "past_%d" },
+      "outputs": { "present_names": "present_%d" }
+    }
+  },
+  "tool_calling": {
+    "tool_call_start_token": "<tool_call>",
+    "tool_call_end_token": "</tool_call>"
+  },
+  "reasoning": {
+    "reasoning_start_token": "<think>",
+    "reasoning_end_token": "</think>"
+  }
+})";
+  }
+
+  auto model = OgaModel::Create(temp_dir.string().c_str());
+
+  auto tool_start = model->GetTag("tool_call_start");
+  auto tool_end = model->GetTag("tool_call_end");
+  auto reasoning_start = model->GetTag("reasoning_start");
+  auto reasoning_end = model->GetTag("reasoning_end");
+
+  EXPECT_STREQ(static_cast<const char*>(tool_start), "<tool_call>");
+  EXPECT_STREQ(static_cast<const char*>(tool_end), "</tool_call>");
+  EXPECT_STREQ(static_cast<const char*>(reasoning_start), "<think>");
+  EXPECT_STREQ(static_cast<const char*>(reasoning_end), "</think>");
+
+  // Cleanup
+  std::filesystem::remove_all(temp_dir);
+}