From 0716a4cf15b06059ccef9f9d44b6293706939d34 Mon Sep 17 00:00:00 2001
From: Felipe Rodrigues Gare Carnielli <felipe.gare@hotmail.com>
Date: Fri, 22 May 2026 00:55:38 -0300
Subject: [PATCH] fix(anthropic): handle empty streaming tool calls

---
 .../adapters/transformation.py                |  2 +-
 ...al_pass_through_adapters_transformation.py | 45 +++++++++++++++++++
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py b/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py
index 0e198daf089e..51a1e739a0f3 100644
--- a/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py
@@ -1476,7 +1476,7 @@ def _translate_streaming_openai_chunk_to_anthropic(
         for choice in choices:
             if choice.delta.content is not None and len(choice.delta.content) > 0:
                 text += choice.delta.content
-            if choice.delta.tool_calls is not None:
+            if choice.delta.tool_calls:
                 partial_json = ""
                 for tool in choice.delta.tool_calls:
                     if (
diff --git a/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py b/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py
index 11465e6f7180..44530fecebdf 100644
--- a/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py
+++ b/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py
@@ -1203,6 +1203,51 @@ def test_streaming_chunk_with_both_text_and_tool_calls_issue_18238():
     assert content_block_start["id"] == "toolu_bdrk_013xRVejhv3ybmLEGCoZib2b"
 
 
+def test_streaming_chunk_with_text_and_empty_tool_calls_returns_text_delta():
+    """
+    Some OpenAI-compatible providers emit `tool_calls: []` on regular text chunks.
+
+    Empty tool_calls should be treated as no tool call so the Anthropic adapter
+    does not shadow text with an empty input_json_delta.
+    """
+    choices = [
+        StreamingChoices(
+            finish_reason=None,
+            index=0,
+            delta=Delta(
+                provider_specific_fields=None,
+                content="Hello from vLLM",
+                role="assistant",
+                function_call=None,
+                tool_calls=[],
+                audio=None,
+            ),
+            logprobs=None,
+        )
+    ]
+
+    adapter = LiteLLMAnthropicMessagesAdapter()
+
+    (
+        type_of_content,
+        content_block_delta,
+    ) = adapter._translate_streaming_openai_chunk_to_anthropic(choices=choices)
+
+    assert type_of_content == "text_delta"
+    assert content_block_delta["type"] == "text_delta"
+    assert content_block_delta["text"] == "Hello from vLLM"
+
+    (
+        block_type,
+        content_block_start,
+    ) = adapter._translate_streaming_openai_chunk_to_anthropic_content_block(
+        choices=choices
+    )
+
+    assert block_type == "text"
+    assert content_block_start == {"type": "text", "text": ""}
+
+
 # ============================================================================
 # Cache Control Transformation Tests
 # ============================================================================