fix(anthropic,bedrock): omit thinking/output_config when reasoning_effort="none"

Setting reasoning_effort="none" on Anthropic chat models (direct, Bedrock
Invoke, Bedrock Converse, Vertex AI Anthropic, Azure AI Anthropic) crashed
LiteLLM with:

  litellm.APIConnectionError: 'NoneType' object has no attribute 'get'

Both the Anthropic chat transformation and Bedrock Converse called
``AnthropicConfig._map_reasoning_effort`` and assigned the ``None`` it returns
for ``"none"`` directly to ``optional_params["thinking"]``. Downstream
``is_thinking_enabled`` then did ``optional_params["thinking"].get("type")``
and crashed.

Pop ``thinking`` (and on Claude 4.6/4.7, ``output_config``) instead of
assigning ``None``, restoring the documented contract that
``reasoning_effort="none"`` means "do not enable thinking". This also
prevents downstream Anthropic 400s ("thinking: Input should be an object",
"output_config.effort: Input should be ...") if the bug were ever masked.

Verified end-to-end against the live Anthropic API and Bedrock Converse
on claude-opus-4-{5,6,7} and claude-sonnet-4-6, plus Bedrock Invoke for
Claude 4.5/4.6. Vertex AI Anthropic and Azure AI Anthropic inherit the
fixed ``map_openai_params`` from ``AnthropicConfig`` and need no further
changes.

litellm/llms/anthropic/chat/transformation.py

@@ -1088,24 +1088,29 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
             elif param == "thinking":
                 optional_params["thinking"] = value
             elif param == "reasoning_effort" and isinstance(value, str):
-                optional_params["thinking"] = AnthropicConfig._map_reasoning_effort(
+                mapped_thinking = AnthropicConfig._map_reasoning_effort(
                     reasoning_effort=value, model=model
                 )
-                # For Claude 4.6+ models, effort is controlled via output_config,
-                # not thinking budget_tokens. Map reasoning_effort to output_config.
-                if AnthropicConfig._is_claude_4_6_model(
-                    model
-                ) or AnthropicConfig._is_claude_4_7_model(model):
-                    effort_map = {
-                        "low": "low",
-                        "minimal": "low",
-                        "medium": "medium",
-                        "high": "high",
-                        "xhigh": "xhigh",
-                        "max": "max",
-                    }
-                    mapped_effort = effort_map.get(value, value)
-                    optional_params["output_config"] = {"effort": mapped_effort}
+                if mapped_thinking is None:
+                    optional_params.pop("thinking", None)
+                    optional_params.pop("output_config", None)
+                else:
+                    optional_params["thinking"] = mapped_thinking
+                    # For Claude 4.6+ models, effort is controlled via output_config,
+                    # not thinking budget_tokens. Map reasoning_effort to output_config.
+                    if AnthropicConfig._is_claude_4_6_model(
+                        model
+                    ) or AnthropicConfig._is_claude_4_7_model(model):
+                        effort_map = {
+                            "low": "low",
+                            "minimal": "low",
+                            "medium": "medium",
+                            "high": "high",
+                            "xhigh": "xhigh",
+                            "max": "max",
+                        }
+                        mapped_effort = effort_map.get(value, value)
+                        optional_params["output_config"] = {"effort": mapped_effort}
             elif param == "web_search_options" and isinstance(value, dict):
                 hosted_web_search_tool = self.map_web_search_tool(
                     cast(OpenAIWebSearchOptions, value)

litellm/llms/bedrock/chat/converse_transformation.py

@@ -449,9 +449,13 @@ class AmazonConverseConfig(BaseConfig):
             optional_params.update(reasoning_config)
         else:
             # Anthropic and other models: convert to thinking parameter
-            optional_params["thinking"] = AnthropicConfig._map_reasoning_effort(
+            mapped_thinking = AnthropicConfig._map_reasoning_effort(
                 reasoning_effort=reasoning_effort, model=model
             )
+            if mapped_thinking is None:
+                optional_params.pop("thinking", None)
+            else:
+                optional_params["thinking"] = mapped_thinking
 
     @staticmethod
     def _clamp_thinking_budget_tokens(optional_params: dict) -> None:

tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py

@@ -1687,9 +1687,7 @@ def test_max_effort_rejected_for_opus_45():
 
     messages = [{"role": "user", "content": "Test"}]
 
-    with pytest.raises(
-        ValueError, match="effort='max' is not supported by this model"
-    ):
+    with pytest.raises(ValueError, match="effort='max' is not supported by this model"):
         optional_params = {"output_config": {"effort": "max"}}
         config.transform_request(
             model="claude-opus-4-5-20251101",
@@ -2251,9 +2249,7 @@ def test_max_effort_rejected_for_sonnet_46():
     config = AnthropicConfig()
     messages = [{"role": "user", "content": "Test"}]
 
-    with pytest.raises(
-        ValueError, match="effort='max' is not supported by this model"
-    ):
+    with pytest.raises(ValueError, match="effort='max' is not supported by this model"):
         config.transform_request(
             model="claude-sonnet-4-6-20260219",
             messages=messages,
@@ -2315,6 +2311,30 @@ def test_effort_beta_header_not_injected_for_46_models():
         assert result is False, f"is_effort_used should return False for {model}"
 
 
+@pytest.mark.parametrize(
+    "model",
+    [
+        "claude-opus-4-5-20251101",
+        "claude-opus-4-6-20250514",
+        "claude-sonnet-4-6-20260219",
+        "claude-opus-4-7",
+    ],
+)
+def test_reasoning_effort_none_omits_thinking_and_output_config(model):
+    """reasoning_effort="none" must omit thinking and output_config from the request."""
+    config = AnthropicConfig()
+
+    result = config.map_openai_params(
+        non_default_params={"reasoning_effort": "none"},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+
+    assert "thinking" not in result
+    assert "output_config" not in result
+
+
 def test_effort_beta_header_still_injected_for_older_models():
     """
     Test that is_effort_used still returns True for pre-4.6 models

tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py

@@ -288,6 +288,28 @@ def test_reasoning_with_forced_tool_choice_switches_to_auto():
     assert optional_params["tool_choice"] == {"auto": {}}
 
 
+@pytest.mark.parametrize(
+    "model",
+    [
+        "bedrock/converse/us.anthropic.claude-opus-4-5-20251101-v1:0",
+        "bedrock/converse/us.anthropic.claude-opus-4-6-v1",
+        "bedrock/converse/us.anthropic.claude-opus-4-7",
+    ],
+)
+def test_reasoning_effort_none_omits_thinking_for_anthropic_converse(model):
+    """reasoning_effort="none" must omit thinking from the Bedrock Converse request."""
+    config = AmazonConverseConfig()
+
+    optional_params = config.map_openai_params(
+        non_default_params={"reasoning_effort": "none"},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+
+    assert "thinking" not in optional_params
+
+
 def test_get_supported_openai_params():
     config = AmazonConverseConfig()
     supported_params = config.get_supported_openai_params(