fix(fireworks_ai): default supports_tool_choice=True for unmapped models

Fireworks models absent from the cost map defaulted supports_function_calling to True but left supports_tool_choice unset, so tool_choice was rejected with UnsupportedParamsError even though the upstream request would succeed. Default supports_tool_choice to True in get_provider_info, mirroring supports_function_calling, while still letting an explicit cost-map value override it.

Fixes #35382

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm/llms/fireworks_ai/chat/transformation.py

@@ -439,18 +439,23 @@ class FireworksAIConfig(FireworksAIMixin, OpenAIGPTConfig):
         supports_function_calling_value = self._get_model_cost_capability(
             model=model, capability="supports_function_calling"
         )
+        supports_tool_choice_value = self._get_model_cost_capability(model=model, capability="supports_tool_choice")
         supports_reasoning_value = self._get_model_cost_capability(model=model, capability="supports_reasoning")
         supports_vision_value = self._get_model_cost_capability(model=model, capability="supports_vision")
         supports_pdf_input_value = self._get_model_cost_capability(model=model, capability="supports_pdf_input")
 
         provider_specific_model_info: ProviderSpecificModelInfo = {
             "supports_function_calling": True,
+            "supports_tool_choice": True,
             "supports_prompt_caching": True,  # https://docs.fireworks.ai/guides/prompt-caching
         }
 
         if supports_function_calling_value is not None:
             provider_specific_model_info["supports_function_calling"] = supports_function_calling_value
 
+        if supports_tool_choice_value is not None:
+            provider_specific_model_info["supports_tool_choice"] = supports_tool_choice_value
+
         # Only include supports_reasoning if True
         if supports_reasoning_value:
             provider_specific_model_info["supports_reasoning"] = supports_reasoning_value

tests/test_litellm/llms/fireworks_ai/chat/test_fireworks_ai_chat_transformation.py

@@ -20,6 +20,7 @@ from litellm.types.utils import (
     Message,
     ModelResponse,
 )
+from litellm.utils import supports_tool_choice
 
 
 @pytest.fixture(autouse=True)
@@ -467,6 +468,30 @@ def test_unmapped_model_fallback_function_calling():
     assert info["supports_function_calling"] is True
 
 
+def test_unmapped_model_fallback_tool_choice(monkeypatch):
+    """A Fireworks model absent from the cost map must still advertise tool_choice, matching supports_function_calling. Regression for #35382 (Kimi K3)."""
+    monkeypatch.setenv("LITELLM_LOCAL_MODEL_COST_MAP", "True")
+    litellm.model_cost = litellm.get_model_cost_map(url="")
+
+    config = FireworksAIConfig()
+    model = "accounts/fireworks/models/kimi-k3"
+
+    info = config.get_provider_info(model)
+    assert info["supports_tool_choice"] is True
+    assert supports_tool_choice(model=model, custom_llm_provider="fireworks_ai") is True
+    assert "tool_choice" in config.get_supported_openai_params(model)
+
+
+def test_provider_info_tool_choice_false_override(monkeypatch):
+    """An explicit supports_tool_choice=False in the cost map still wins over the Fireworks default."""
+    config = FireworksAIConfig()
+    model = "fireworks_ai/test-no-tool-choice"
+    monkeypatch.setitem(litellm.model_cost, model, {"supports_tool_choice": False})
+
+    info = config.get_provider_info(model)
+    assert info["supports_tool_choice"] is False
+
+
 def test_transform_messages_helper_strips_thinking_blocks():
     """thinking_blocks must not be forwarded to Fireworks chat completions."""
     config = FireworksAIConfig()