fix(databricks,base_llm): narrow gemini-2.5 match and guard thinking-tokens helper.

litellm/llms/base_llm/chat/transformation.py

@@ -14,7 +14,6 @@ from typing import (
     Tuple,
     Type,
     Union,
-    cast,
 )
 
 import httpx
@@ -124,7 +123,15 @@ class BaseConfig(ABC):
         if is_thinking_enabled and (
             "max_tokens" not in non_default_params and "max_completion_tokens" not in non_default_params
         ):
-            thinking_token_budget = cast(dict, optional_params["thinking"]).get("budget_tokens", None)
+            # `is_thinking_enabled` is True when `reasoning_effort` is set OR
+            # when `thinking` is set. Providers that pass `reasoning_effort`
+            # through natively (e.g. Databricks-Gemini-3+, Databricks-GPT-5)
+            # never populate an Anthropic-style `thinking` block, so guard
+            # against that case here.
+            thinking = optional_params.get("thinking")
+            if not isinstance(thinking, dict):
+                return
+            thinking_token_budget = thinking.get("budget_tokens", None)
             if thinking_token_budget is not None:
                 optional_params["max_tokens"] = thinking_token_budget + DEFAULT_MAX_TOKENS
 

litellm/llms/databricks/chat/transformation.py

@@ -276,7 +276,10 @@ class DatabricksConfig(DatabricksBase, OpenAILikeChatConfig, AnthropicConfig):
         model_lower = model.lower()
         if "claude" in model_lower:
             return True
-        if "gemini-2" in model_lower:
+        # Match gemini-2-5 / gemini-2.5 only — not the broader 2.x range, which
+        # could catch hypothetical future 2.0/2.6/etc variants that may use a
+        # different reasoning contract.
+        if "gemini-2-5" in model_lower or "gemini-2.5" in model_lower:
             return True
         return False
 

tests/test_litellm/llms/databricks/chat/test_databricks_chat_transformation.py

@@ -441,15 +441,8 @@ def test_transform_request_keeps_parallel_tool_calls_for_claude():
 
 
 def _map_reasoning_effort(model: str, reasoning_effort, **extra_non_default):
-    """Run map_openai_params with reasoning_effort + optional extras.
-
-    `max_tokens` is included by default to mirror real client behavior. Without
-    it the base-class `update_optional_params_with_thinking_tokens` helper
-    KeyErrors on pure pass-through models (a pre-existing issue orthogonal to
-    this fix — `is_thinking_enabled` returns True whenever `reasoning_effort` is
-    set, but the helper then assumes `optional_params["thinking"]` exists).
-    """
-    non_default = {"reasoning_effort": reasoning_effort, "max_tokens": 1024}
+    """Run map_openai_params with reasoning_effort + optional extras."""
+    non_default = {"reasoning_effort": reasoning_effort}
     non_default.update(extra_non_default)
     return DatabricksConfig().map_openai_params(
         non_default_params=non_default,
@@ -506,6 +499,25 @@ def test_gemini_2_5_pro_translates_to_thinking_budget():
     assert "reasoning_effort" not in params
 
 
+def test_gemini_2_5_with_dot_notation_translates():
+    """A user passing the upstream Google-style `gemini-2.5-...` form should
+    still trigger the Anthropic-thinking translation, not pass through."""
+    params = _map_reasoning_effort("databricks-gemini-2.5-flash", "low")
+    assert params.get("thinking") == {
+        "type": "enabled",
+        "budget_tokens": DEFAULT_REASONING_EFFORT_LOW_THINKING_BUDGET,
+    }
+    assert "reasoning_effort" not in params
+
+
+def test_gemini_2_0_does_not_match():
+    """Guard against over-matching: `gemini-2-0` (hypothetical or future) is
+    NOT a Gemini 2.5 endpoint and must not get the thinking translation."""
+    params = _map_reasoning_effort("databricks-gemini-2-0-flash", "low")
+    assert "thinking" not in params
+    assert params.get("reasoning_effort") == "low"
+
+
 def test_gemini_2_5_none_drops_thinking_and_reasoning_effort():
     """`reasoning_effort='none'` mirrors the Claude behavior: no thinking emitted."""
     params = _map_reasoning_effort("databricks-gemini-2-5-flash", "none")