From 209e9e05aa3a5543639df154fe54974e0b708e9a Mon Sep 17 00:00:00 2001
From: Sameer Kankute <sameer@berri.ai>
Date: Wed, 3 Dec 2025 10:13:59 +0530
Subject: [PATCH] Fix gemini 3 last chunk thinking block

---
 .../vertex_and_google_ai_studio_gemini.py     |  5 +++++
 .../test_gemini_reasoning_content.py          | 20 +++++++++++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 tests/local_testing/test_gemini_reasoning_content.py

diff --git a/litellm/llms/vertex_ai/gemini/vertex_and_google_ai_studio_gemini.py b/litellm/llms/vertex_ai/gemini/vertex_and_google_ai_studio_gemini.py
index 5fef8c1ec49..cfc13f5601d 100644
--- a/litellm/llms/vertex_ai/gemini/vertex_and_google_ai_studio_gemini.py
+++ b/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",
diff --git a/tests/local_testing/test_gemini_reasoning_content.py b/tests/local_testing/test_gemini_reasoning_content.py
new file mode 100644
index 00000000000..7e516ae8439
--- /dev/null
+++ b/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"