fix(anthropic): upgrade legacy thinking after the Bedrock Invoke and Vertex structured-output stub swap

litellm/llms/bedrock/chat/invoke_transformations/anthropic_claude3_transformation.py

@@ -107,6 +107,10 @@ class AmazonAnthropicClaudeConfig(AmazonInvokeConfig, AnthropicConfig):
         # Restore original model name
         model = original_model
 
+        AnthropicModelInfo.translate_legacy_thinking_for_adaptive_model(
+            model=original_model, optional_params=optional_params, custom_llm_provider="bedrock"
+        )
+
         # The stub model hides the original model from the parent's forced-tool-use backstop
         response_format_tool_choice: Final = optional_params.get("tool_choice")
         if (

litellm/llms/vertex_ai/vertex_ai_partner_models/anthropic/transformation.py

@@ -177,6 +177,10 @@ class VertexAIAnthropicConfig(AnthropicConfig):
         # Restore original model name for any other processing
         model = original_model
 
+        AnthropicModelInfo.translate_legacy_thinking_for_adaptive_model(
+            model=original_model, optional_params=optional_params, custom_llm_provider="vertex_ai"
+        )
+
         return optional_params
 
     def transform_response(

tests/test_litellm/llms/bedrock/chat/invoke_transformations/test_bedrock_chat_invoke_transformations_anthropic_claude3_transformation.py

@@ -671,3 +671,27 @@ def test_bedrock_chat_invoke_fable_5_1_response_format_avoids_forced_tool_choice
     assert "output_format" not in result
     assert "tools" in result
     assert "tool_choice" not in result
+
+
+@pytest.mark.parametrize("model", ["us.anthropic.claude-sonnet-5", "us.anthropic.claude-fable-5-1"])
+def test_bedrock_chat_invoke_tool_based_response_format_still_upgrades_legacy_thinking(local_model_cost_map, model):
+    result = AmazonAnthropicClaudeConfig().map_openai_params(
+        non_default_params={
+            "response_format": {
+                "type": "json_schema",
+                "json_schema": {
+                    "name": "test_schema",
+                    "schema": {"type": "object", "properties": {"result": {"type": "string"}}},
+                },
+            },
+            "thinking": {"type": "enabled", "budget_tokens": 4096},
+            "max_tokens": 8192,
+        },
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+
+    assert "tools" in result
+    assert result["thinking"] == {"type": "adaptive"}
+    assert result["output_config"] == {"effort": "high"}

tests/test_litellm/llms/vertex_ai/vertex_ai_partner_models/anthropic/test_vertex_ai_partner_models_anthropic_transformation.py

@@ -752,3 +752,26 @@ def test_vertex_ai_fable_5_1_response_format_uses_native_output_format(local_mod
     assert "output_format" in result_params
     assert "tool_choice" not in result_params
     assert "tools" not in result_params
+
+
+def test_vertex_ai_anthropic_tool_based_response_format_still_upgrades_legacy_thinking(local_model_cost_map):
+    result_params = VertexAIAnthropicConfig().map_openai_params(
+        non_default_params={
+            "response_format": {
+                "type": "json_schema",
+                "json_schema": {
+                    "name": "test_schema",
+                    "schema": {"type": "object", "properties": {"result": {"type": "string"}}},
+                },
+            },
+            "thinking": {"type": "enabled", "budget_tokens": 4096},
+            "max_tokens": 8192,
+        },
+        optional_params={},
+        model="claude-opus-4-8",
+        drop_params=False,
+    )
+
+    assert "tools" in result_params
+    assert result_params["thinking"] == {"type": "adaptive"}
+    assert result_params["output_config"] == {"effort": "high"}