fix(litellm): generate toolUseId when missing from provider

src/strands/models/litellm.py

@@ -5,6 +5,7 @@
 
 import json
 import logging
+import uuid
 from typing import Any, AsyncGenerator, Optional, Type, TypedDict, TypeVar, Union, cast
 
 import litellm
@@ -321,7 +322,11 @@ async def stream(
                 break
 
         for tool_deltas in tool_calls.values():
-            yield self.format_chunk({"chunk_type": "content_start", "data_type": "tool", "data": tool_deltas[0]})
+            first_delta = tool_deltas[0]
+            if not first_delta.id:
+                first_delta.id = f"call_{uuid.uuid4()}"
+
+            yield self.format_chunk({"chunk_type": "content_start", "data_type": "tool", "data": first_delta})
 
             for tool_delta in tool_deltas:
                 yield self.format_chunk({"chunk_type": "content_delta", "data_type": "tool", "data": tool_delta})

tests/strands/models/test_litellm.py

@@ -478,3 +478,39 @@ def test_format_request_messages_cache_point_support():
     ]
 
     assert result == expected
+
+
+@pytest.mark.asyncio
+async def test_stream_generates_tool_call_id_when_null(litellm_acompletion, model, agenerator, alist):
+    """Test that stream generates a tool call ID when LiteLLM returns null."""
+    mock_tool_call = unittest.mock.Mock(index=0)
+    mock_tool_call.id = None
+    mock_tool_call.function.name = "test_tool"
+    mock_tool_call.function.arguments = '{"arg": "value"}'
+
+    mock_delta = unittest.mock.Mock(content=None, tool_calls=[mock_tool_call], reasoning_content=None)
+
+    mock_event_1 = unittest.mock.Mock(choices=[unittest.mock.Mock(finish_reason=None, delta=mock_delta)])
+    mock_event_2 = unittest.mock.Mock(
+        choices=[
+            unittest.mock.Mock(
+                finish_reason="tool_calls",
+                delta=unittest.mock.Mock(content=None, tool_calls=None, reasoning_content=None),
+            )
+        ]
+    )
+
+    litellm_acompletion.side_effect = unittest.mock.AsyncMock(return_value=agenerator([mock_event_1, mock_event_2]))
+
+    messages = [{"role": "user", "content": [{"text": "test"}]}]
+    response = model.stream(messages)
+    tru_events = await alist(response)
+
+    tool_start_event = next(
+        e for e in tru_events if "contentBlockStart" in e and "toolUse" in e["contentBlockStart"]["start"]
+    )
+
+    tool_id = tool_start_event["contentBlockStart"]["start"]["toolUse"]["toolUseId"]
+    assert tool_id is not None
+    assert tool_id.startswith("call_")
+    assert len(tool_id) > 5