fix(bedrock): route reasoning_effort to reasoning.effort for OpenAI GPT-5.x on Converse

OpenAI GPT-5.x models on Bedrock Converse expect reasoning effort under
additionalModelRequestFields as {"reasoning": {"effort": ...}}. They were
falling into the Anthropic branch and emitting a `thinking` block, which
Converse rejects with unknown_parameter.

The bedrock_converse gpt-5.6 entries were also missing supports_reasoning,
so reasoning_effort was dropped before mapping. Setting the flag lets the
existing config-driven supported-params path accept it, rather than adding
another model-name branch.

litellm/llms/bedrock/chat/converse_transformation.py

@@ -418,12 +418,18 @@ class AmazonConverseConfig(BaseConfig):
         Handle the reasoning_effort parameter based on the model type.
 
         - GPT-OSS models: passed through unchanged via additionalModelRequestFields.
+        - OpenAI GPT-5.x models: mapped to ``reasoning.effort`` via additionalModelRequestFields.
         - Nova 2 models: transformed to reasoningConfig.
         - Anthropic models: mapped to ``thinking`` (and ``output_config.effort`` on
           adaptive Claude 4.6 / 4.7).
         """
         if "gpt-oss" in model:
             optional_params["reasoning_effort"] = reasoning_effort
+        elif "openai.gpt-5" in model:
+            # Converse rejects Anthropic's `thinking` for OpenAI GPT-5.x; effort goes
+            # under additionalModelRequestFields as {"reasoning": {"effort": ...}}.
+            optional_params.pop("thinking", None)
+            optional_params["reasoning"] = {"effort": reasoning_effort}
         elif self._is_nova_2_model(model):
             reasoning_config: Final = self._transform_reasoning_effort_to_reasoning_config(reasoning_effort)
             optional_params.update(reasoning_config)

litellm/model_prices_and_context_window_backup.json

@@ -49473,6 +49473,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "global.openai.gpt-5.6-sol": {
@@ -49498,6 +49499,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "us.openai.gpt-5.6-terra": {
@@ -49523,6 +49525,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "global.openai.gpt-5.6-terra": {
@@ -49548,6 +49551,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "us.openai.gpt-5.6-luna": {
@@ -49573,6 +49577,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "global.openai.gpt-5.6-luna": {
@@ -49598,6 +49603,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "bedrock_mantle/openai.gpt-5.5": {

model_prices_and_context_window.json

@@ -49473,6 +49473,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "global.openai.gpt-5.6-sol": {
@@ -49498,6 +49499,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "us.openai.gpt-5.6-terra": {
@@ -49523,6 +49525,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "global.openai.gpt-5.6-terra": {
@@ -49548,6 +49551,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "us.openai.gpt-5.6-luna": {
@@ -49573,6 +49577,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "global.openai.gpt-5.6-luna": {
@@ -49598,6 +49603,7 @@
         ],
         "supports_function_calling": true,
         "supports_tool_choice": true,
+        "supports_reasoning": true,
         "supports_vision": true
     },
     "bedrock_mantle/openai.gpt-5.5": {

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

@@ -284,6 +284,37 @@ def test_reasoning_with_forced_tool_choice_switches_to_auto():
     assert optional_params["tool_choice"] == {"auto": {}}
 
 
+@pytest.mark.parametrize(
+    "model",
+    [
+        "us.openai.gpt-5.6-sol",
+        "global.openai.gpt-5.6-terra",
+        "bedrock/converse/us.openai.gpt-5.6-luna",
+    ],
+)
+def test_reasoning_effort_maps_to_reasoning_effort_for_openai_gpt5_converse(model, local_model_cost_map):
+    """OpenAI GPT-5.x on Bedrock Converse routes reasoning_effort to
+    ``additionalModelRequestFields.reasoning.effort`` rather than Anthropic ``thinking``."""
+    config = AmazonConverseConfig()
+
+    assert "reasoning_effort" in config.get_supported_openai_params(model=model)
+
+    optional_params = config.map_openai_params(
+        non_default_params={"reasoning_effort": "high"},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+
+    assert optional_params["reasoning"] == {"effort": "high"}
+    assert "thinking" not in optional_params
+    assert "reasoning_effort" not in optional_params
+
+    _, additional_request_params, _, _ = config._prepare_request_params(optional_params, model)
+    assert additional_request_params["reasoning"] == {"effort": "high"}
+    assert "thinking" not in additional_request_params
+
+
 @pytest.mark.parametrize(
     "model",
     [