From c5ca2afec3b0e98cb014c36c439a749226e434d3 Mon Sep 17 00:00:00 2001
From: Tim Elfrink <Tim.Elfrink@stepstone.de>
Date: Mon, 15 Sep 2025 21:11:13 +0200
Subject: [PATCH 1/2] Add test for tool call sequential index assignment

- Test multiple tool calls without explicit indices receive sequential indices
- Verify Delta class assigns indices 0, 1, 2... instead of defaulting all to 0
- Add comprehensive assertions for tool call details preservation
- Cover provider-agnostic streaming response scenarios
---
 tests/litellm_utils_tests/test_utils.py | 50 +++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/tests/litellm_utils_tests/test_utils.py b/tests/litellm_utils_tests/test_utils.py
index 8d4fc3ac451..482cda1e104 100644
--- a/tests/litellm_utils_tests/test_utils.py
+++ b/tests/litellm_utils_tests/test_utils.py
@@ -2326,3 +2326,53 @@ def test_get_whitelisted_models():
             file.write(f"{model}\n")
 
     print("whitelisted_models written to whitelisted_bedrock_models.txt")
+
+
+def test_delta_tool_calls_sequential_indices():
+    """
+    Test that multiple tool calls without explicit indices receive sequential indices.
+
+    When providers don't include index fields in tool calls, the Delta class
+    should automatically assign sequential indices (0, 1, 2, ...) instead of
+    defaulting all tool calls to index=0.
+    """
+    import json
+    from litellm.types.utils import Delta
+
+    # Simulate tool calls from streaming responses without explicit indices
+    tool_calls_without_indices = [
+        {
+            "id": "call_1",
+            "function": {
+                "name": "get_weather_for_dallas",
+                "arguments": json.dumps({})
+            },
+            "type": "function",
+            # Note: no "index" field - simulates provider response
+        },
+        {
+            "id": "call_2",
+            "function": {
+                "name": "get_weather_precise",
+                "arguments": json.dumps({"location": "Dallas, TX"})
+            },
+            "type": "function",
+            # Note: no "index" field - simulates provider response
+        }
+    ]
+
+    # Create Delta object as LiteLLM would when processing streaming response
+    delta = Delta(
+        content=None,
+        tool_calls=tool_calls_without_indices
+    )
+
+    # Verify tool calls have sequential indices
+    assert delta.tool_calls is not None, "Tool calls should not be None"
+    assert len(delta.tool_calls) == 2
+    assert delta.tool_calls[0].index == 0, f"First tool call should have index 0, got {delta.tool_calls[0].index}"
+    assert delta.tool_calls[1].index == 1, f"Second tool call should have index 1, got {delta.tool_calls[1].index}"
+
+    # Verify tool call details are preserved
+    assert delta.tool_calls[0].function.name == "get_weather_for_dallas"
+    assert delta.tool_calls[1].function.name == "get_weather_precise"

From 802f7011e260d729410fe152151811b24ff90913 Mon Sep 17 00:00:00 2001
From: Tim Elfrink <Tim.Elfrink@stepstone.de>
Date: Mon, 15 Sep 2025 21:11:31 +0200
Subject: [PATCH 2/2] Fix tool call index assignment in Delta class

- Update tool call index logic to assign sequential indices when missing
- Replace default index=0 behavior with proper sequential assignment
- Maintain OpenAI API compatibility with correct tool call indexing
- Preserve existing behavior for tool calls with explicit indices
- Universal fix benefiting all providers using Delta class
---
 litellm/types/utils.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/litellm/types/utils.py b/litellm/types/utils.py
index 289291bde08..228677a17a7 100644
--- a/litellm/types/utils.py
+++ b/litellm/types/utils.py
@@ -754,10 +754,12 @@ class Delta(OpenAIObject):
             self.function_call = function_call
         if tool_calls is not None and isinstance(tool_calls, list):
             self.tool_calls = []
+            current_index = 0
             for tool_call in tool_calls:
                 if isinstance(tool_call, dict):
                     if tool_call.get("index", None) is None:
-                        tool_call["index"] = 0
+                        tool_call["index"] = current_index
+                        current_index += 1
                     self.tool_calls.append(ChatCompletionDeltaToolCall(**tool_call))
                 elif isinstance(tool_call, ChatCompletionDeltaToolCall):
                     self.tool_calls.append(tool_call)