feat(anthropic): support adaptive thinking mode (#36293)

Thank you!

libs/partners/anthropic/langchain_anthropic/chat_models.py

@@ -1652,7 +1652,7 @@ class ChatAnthropic(BaseChatModel):
         # _get_llm_for_structured_output_when_thinking_is_enabled.
         if (
             self.thinking is not None
-            and self.thinking.get("type") == "enabled"
+            and self.thinking.get("type") in ("enabled", "adaptive")
             and "tool_choice" in kwargs
             and kwargs["tool_choice"].get("type") in ("any", "tool")
         ):
@@ -1781,7 +1781,10 @@ class ChatAnthropic(BaseChatModel):
             # The result of convert_to_anthropic_tool for 'method=function_calling' will
             # always be an AnthropicTool
             tool_name = formatted_tool["name"]
-            if self.thinking is not None and self.thinking.get("type") == "enabled":
+            if self.thinking is not None and self.thinking.get("type") in (
+                "enabled",
+                "adaptive",
+            ):
                 llm = self._get_llm_for_structured_output_when_thinking_is_enabled(
                     schema,
                     formatted_tool,
@@ -1993,7 +1996,7 @@ def _tools_in_params(params: dict) -> bool:
 
 
 def _thinking_in_params(params: dict) -> bool:
-    return params.get("thinking", {}).get("type") == "enabled"
+    return params.get("thinking", {}).get("type") in ("enabled", "adaptive")
 
 
 def _documents_in_params(params: dict) -> bool:

libs/partners/anthropic/tests/unit_tests/test_chat_models.py

@@ -29,6 +29,7 @@ from langchain_anthropic.chat_models import (
     _format_messages,
     _is_builtin_tool,
     _merge_messages,
+    _thinking_in_params,
     convert_to_anthropic_tool,
 )
 
@@ -2675,6 +2676,57 @@ def test_bind_tools_drops_forced_tool_choice_when_thinking_enabled() -> None:
     assert len(w) == 1
 
 
+def test_bind_tools_drops_forced_tool_choice_when_adaptive_thinking() -> None:
+    """Adaptive thinking has the same forced tool_choice restriction as enabled."""
+    chat_model = ChatAnthropic(
+        model=MODEL_NAME,
+        anthropic_api_key="secret-api-key",
+        thinking={"type": "adaptive"},
+    )
+
+    # tool_choice="any" should be dropped with warning
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter("always")
+        result = chat_model.bind_tools([GetWeather], tool_choice="any")
+    assert "tool_choice" not in cast("RunnableBinding", result).kwargs
+    assert len(w) == 1
+    assert "thinking is enabled" in str(w[0].message)
+
+    # tool_choice="auto" should NOT be dropped (auto is allowed)
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter("always")
+        result = chat_model.bind_tools([GetWeather], tool_choice="auto")
+    assert cast("RunnableBinding", result).kwargs["tool_choice"] == {"type": "auto"}
+    assert len(w) == 0
+
+    # tool_choice=specific tool name should be dropped with warning
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter("always")
+        result = chat_model.bind_tools([GetWeather], tool_choice="GetWeather")
+    assert "tool_choice" not in cast("RunnableBinding", result).kwargs
+    assert len(w) == 1
+
+    # tool_choice=dict with type "tool" should be dropped with warning
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter("always")
+        result = chat_model.bind_tools(
+            [GetWeather],
+            tool_choice={"type": "tool", "name": "GetWeather"},
+        )
+    assert "tool_choice" not in cast("RunnableBinding", result).kwargs
+    assert len(w) == 1
+
+    # tool_choice=dict with type "any" should also be dropped
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter("always")
+        result = chat_model.bind_tools(
+            [GetWeather],
+            tool_choice={"type": "any"},
+        )
+    assert "tool_choice" not in cast("RunnableBinding", result).kwargs
+    assert len(w) == 1
+
+
 def test_bind_tools_keeps_forced_tool_choice_when_thinking_disabled() -> None:
     """When thinking is not enabled, forced tool_choice should pass through."""
     chat_model = ChatAnthropic(
@@ -2703,3 +2755,12 @@ def test_bind_tools_keeps_forced_tool_choice_when_thinking_disabled() -> None:
     )
     result = chat_model_disabled.bind_tools([GetWeather], tool_choice="any")
     assert cast("RunnableBinding", result).kwargs["tool_choice"] == {"type": "any"}
+
+
+def test_thinking_in_params_recognizes_adaptive() -> None:
+    """_thinking_in_params should recognize both enabled and adaptive types."""
+    assert _thinking_in_params({"thinking": {"type": "enabled", "budget_tokens": 5000}})
+    assert _thinking_in_params({"thinking": {"type": "adaptive"}})
+    assert not _thinking_in_params({"thinking": {"type": "disabled"}})
+    assert not _thinking_in_params({"thinking": {}})
+    assert not _thinking_in_params({})