fix(transformation): convert 'thinking' parameter to 'reasoning_effort' for Claude models

litellm/llms/github_copilot/chat/transformation.py

@@ -130,6 +130,54 @@ class GithubCopilotConfig(OpenAIConfig):
 
         return base_params
 
+    def map_openai_params(
+        self,
+        non_default_params: dict,
+        optional_params: dict,
+        model: str,
+        drop_params: bool,
+    ) -> dict:
+        """
+        Map OpenAI params to GitHub Copilot params.
+
+        GitHub Copilot uses an OpenAI-compatible API and does not understand the
+        Anthropic-native ``thinking`` parameter. When Claude Code calls the proxy's
+        ``/v1/messages`` endpoint with ``thinking`` and the request is routed to a
+        ``github_copilot/claude-*`` model, ``thinking`` must be converted to
+        ``reasoning_effort`` before being forwarded to the Copilot API.
+
+        ``reasoning_effort`` is written directly to ``optional_params`` rather than
+        deferred to the parent: ``OpenAIConfig.map_openai_params`` dispatches to the
+        global ``openAIGPTConfig`` whose supported-params list does not include
+        ``reasoning_effort`` for Claude models, so a deferred write would be dropped.
+        """
+        thinking = non_default_params.pop("thinking", None)
+        existing_reasoning_effort = non_default_params.get("reasoning_effort")
+        if (
+            thinking is not None
+            and isinstance(thinking, dict)
+            and thinking.get("type") == "enabled"
+            and existing_reasoning_effort is None
+        ):
+            budget_tokens = thinking.get("budget_tokens", 0)
+            if budget_tokens >= 10000:
+                reasoning_effort = "high"
+            elif budget_tokens >= 5000:
+                reasoning_effort = "medium"
+            elif budget_tokens >= 2000:
+                reasoning_effort = "low"
+            else:
+                reasoning_effort = "minimal"
+            optional_params["reasoning_effort"] = reasoning_effort
+        elif existing_reasoning_effort is not None:
+            optional_params["reasoning_effort"] = non_default_params.pop(
+                "reasoning_effort"
+            )
+
+        return super().map_openai_params(
+            non_default_params, optional_params, model, drop_params
+        )
+
     def _determine_initiator(self, messages: List[AllMessageValues]) -> str:
         """
         Determine if request is user or agent initiated based on message roles.

tests/test_litellm/llms/github_copilot/test_github_copilot_transformation.py

@@ -433,6 +433,108 @@ def test_get_supported_openai_params_case_insensitive():
     assert "reasoning_effort" not in supported_params_35
 
 
+def test_map_openai_params_converts_thinking_to_reasoning_effort():
+    """
+    Test that Anthropic-native ``thinking`` is converted to ``reasoning_effort`` for
+    GitHub Copilot Claude models.
+
+    GitHub Copilot uses an OpenAI-compatible API and does not understand the
+    Anthropic ``thinking`` parameter. When Claude Code sends ``thinking`` via the
+    proxy's ``/v1/messages`` endpoint, litellm must translate it to
+    ``reasoning_effort`` before forwarding to Copilot.
+    """
+    config = GithubCopilotConfig()
+    model = "claude-sonnet-4-20250514"
+
+    # budget_tokens < 2000 -> "minimal"
+    optional_params = config.map_openai_params(
+        non_default_params={"thinking": {"type": "enabled", "budget_tokens": 1024}},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+    assert "thinking" not in optional_params
+    assert optional_params["reasoning_effort"] == "minimal"
+
+    # 2000 <= budget_tokens < 5000 -> "low"
+    optional_params = config.map_openai_params(
+        non_default_params={"thinking": {"type": "enabled", "budget_tokens": 2000}},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+    assert "thinking" not in optional_params
+    assert optional_params["reasoning_effort"] == "low"
+
+    # 5000 <= budget_tokens < 10000 -> "medium"
+    optional_params = config.map_openai_params(
+        non_default_params={"thinking": {"type": "enabled", "budget_tokens": 5000}},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+    assert "thinking" not in optional_params
+    assert optional_params["reasoning_effort"] == "medium"
+
+    # budget_tokens >= 10000 -> "high"
+    optional_params = config.map_openai_params(
+        non_default_params={"thinking": {"type": "enabled", "budget_tokens": 15000}},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+    assert "thinking" not in optional_params
+    assert optional_params["reasoning_effort"] == "high"
+
+
+def test_map_openai_params_thinking_does_not_overwrite_existing_reasoning_effort():
+    """Caller-supplied ``reasoning_effort`` must not be overwritten by the
+    ``thinking`` translation."""
+    config = GithubCopilotConfig()
+
+    optional_params = config.map_openai_params(
+        non_default_params={
+            "thinking": {"type": "enabled", "budget_tokens": 15000},
+            "reasoning_effort": "low",
+        },
+        optional_params={},
+        model="claude-sonnet-4-20250514",
+        drop_params=False,
+    )
+    assert "thinking" not in optional_params
+    assert optional_params["reasoning_effort"] == "low"
+
+
+def test_map_openai_params_disabled_thinking_is_dropped():
+    """``thinking`` with ``type=disabled`` should be dropped without producing
+    ``reasoning_effort``."""
+    config = GithubCopilotConfig()
+
+    optional_params = config.map_openai_params(
+        non_default_params={"thinking": {"type": "disabled"}},
+        optional_params={},
+        model="claude-sonnet-4-20250514",
+        drop_params=False,
+    )
+    assert "thinking" not in optional_params
+    assert "reasoning_effort" not in optional_params
+
+
+def test_map_openai_params_no_thinking_leaves_params_unchanged():
+    """A request without ``thinking`` should not gain a ``reasoning_effort`` value."""
+    config = GithubCopilotConfig()
+
+    optional_params = config.map_openai_params(
+        non_default_params={"temperature": 0.5},
+        optional_params={},
+        model="claude-sonnet-4-20250514",
+        drop_params=False,
+    )
+    assert "thinking" not in optional_params
+    assert "reasoning_effort" not in optional_params
+    assert optional_params.get("temperature") == 0.5
+
+
 def test_copilot_vision_request_header_with_image():
     """Test that Copilot-Vision-Request header is added when messages contain images"""
     config = GithubCopilotConfig()