Merge pull request #17403 from BerriAI/litellm_streaming_gemini_3_fix

Fix gemini 3 last chunk thinking block

litellm/llms/vertex_ai/gemini/vertex_and_google_ai_studio_gemini.py

@@ -1091,6 +1091,11 @@ class VertexGeminiConfig(VertexAIBaseConfig, BaseConfig):
             if "thoughtSignature" in part:
                 part_copy = part.copy()
                 part_copy.pop("thoughtSignature")
+
+                text_content = part_copy.get("text")
+                if isinstance(text_content, str) and text_content.strip() == "":
+                    continue
+
                 thinking_blocks.append(
                     ChatCompletionThinkingBlock(
                         type="thinking",

tests/local_testing/test_gemini_reasoning_content.py

@@ -0,0 +1,20 @@
+import json
+from litellm.llms.vertex_ai.gemini.vertex_and_google_ai_studio_gemini import VertexGeminiConfig
+
+
+def test_empty_part_does_not_create_thinking_block():
+    parts = [{"text": "", "thoughtSignature": "sig-1"}]
+    config = VertexGeminiConfig()
+    thinking_blocks = config._extract_thinking_blocks_from_parts(parts)
+    assert thinking_blocks == []
+
+
+def test_non_empty_part_creates_thinking_block():
+    parts = [{"text": "Some thinking", "thoughtSignature": "sig-2"}]
+    config = VertexGeminiConfig()
+    thinking_blocks = config._extract_thinking_blocks_from_parts(parts)
+    assert len(thinking_blocks) == 1
+    block = thinking_blocks[0]
+    # thinking should be valid JSON containing the text
+    parsed = json.loads(block["thinking"]) if isinstance(block["thinking"], str) else None
+    assert parsed is not None and parsed.get("text") == "Some thinking"