From ad9e861ae701cc25e96e7e7daacbabc1e70806aa Mon Sep 17 00:00:00 2001
From: ryan-crabbe-berri <ryan@berri.ai>
Date: Tue, 13 Oct 2026 19:01:59 -0700
Subject: [PATCH] fix(anthropic): treat adaptive thinking as enabled when
 mapping response_format

is_thinking_enabled only recognised thinking.type=enabled, so a request that
paired thinking.type=adaptive with response_format took the synthetic JSON
tool path with a forced tool_choice, which Anthropic rejects alongside
thinking. The same check also gates the Bedrock Converse and Databricks
forced tool_choice downgrades, so they now see adaptive thinking too.
---
 litellm/llms/base_llm/chat/transformation.py  |  6 ++++-
 ...ations_anthropic_claude3_transformation.py | 25 +++++++++++++++++++
 tests/unit/test_thinking_enabled.py           |  1 +
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/litellm/llms/base_llm/chat/transformation.py b/litellm/llms/base_llm/chat/transformation.py
index 8275829765b..c410ba8c55d 100644
--- a/litellm/llms/base_llm/chat/transformation.py
+++ b/litellm/llms/base_llm/chat/transformation.py
@@ -124,7 +124,11 @@ class BaseConfig(ABC):
     def is_thinking_enabled(self, non_default_params: dict) -> bool:
         thinking: Final = non_default_params.get("thinking")
         thinking_type: Final = thinking.get("type") if isinstance(thinking, dict) else None
-        return thinking is True or thinking_type == "enabled" or non_default_params.get("reasoning_effort") is not None
+        return (
+            thinking is True
+            or thinking_type in ("enabled", "adaptive")
+            or non_default_params.get("reasoning_effort") is not None
+        )
 
     def is_max_tokens_in_request(self, non_default_params: dict) -> bool:
         """
diff --git a/tests/unit/llms/bedrock/chat/invoke_transformations/test_bedrock_chat_invoke_transformations_anthropic_claude3_transformation.py b/tests/unit/llms/bedrock/chat/invoke_transformations/test_bedrock_chat_invoke_transformations_anthropic_claude3_transformation.py
index 859b57c7cf3..e64f472a5d3 100644
--- a/tests/unit/llms/bedrock/chat/invoke_transformations/test_bedrock_chat_invoke_transformations_anthropic_claude3_transformation.py
+++ b/tests/unit/llms/bedrock/chat/invoke_transformations/test_bedrock_chat_invoke_transformations_anthropic_claude3_transformation.py
@@ -760,6 +760,31 @@ def test_bedrock_chat_invoke_tool_based_response_format_still_upgrades_legacy_th
     assert result["output_config"] == {"effort": "high"}
 
 
+def test_bedrock_chat_invoke_adaptive_thinking_with_tool_based_response_format_avoids_forced_tool_choice(
+    local_model_cost_map,
+):
+    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": "adaptive"},
+            "max_tokens": 8192,
+        },
+        optional_params={},
+        model="us.anthropic.claude-opus-5",
+        drop_params=False,
+    )
+
+    assert "tools" in result
+    assert "tool_choice" not in result
+    assert result["thinking"] == {"type": "adaptive"}
+
+
 def test_bedrock_chat_invoke_response_format_stub_still_upgrades_legacy_thinking(local_model_cost_map):
     """Regression: the tool-based ``response_format`` path swaps in a Claude 3 stub
     model before the shared Anthropic mapping, which hid the adaptive-only model
diff --git a/tests/unit/test_thinking_enabled.py b/tests/unit/test_thinking_enabled.py
index 744b258e617..60f0ec42483 100644
--- a/tests/unit/test_thinking_enabled.py
+++ b/tests/unit/test_thinking_enabled.py
@@ -50,6 +50,7 @@ class TestIsThinkingEnabled:
             ({"thinking": None}, False),
             # thinking={'type': 'enabled'} returns True
             ({"thinking": {"type": "enabled"}}, True),
+            ({"thinking": {"type": "adaptive"}}, True),
             # thinking key missing returns False
             ({}, False),
             # thinking={} returns False