fix(core): (WIP) google tool call streaming fixes

libs/core/langchain_core/messages/block_translators/google_genai.py

@@ -542,12 +542,41 @@ def translate_content(message: AIMessage) -> list[types.ContentBlock]:
 def translate_content_chunk(message: AIMessageChunk) -> list[types.ContentBlock]:
     """Derive standard content blocks from a chunk with Google (GenAI) content.
 
+    For intermediate streaming chunks (`chunk_position != 'last'`), tool calls are
+    returned as `tool_call_chunk` blocks. For final/aggregated chunks, tool calls are
+    returned as `tool_call` blocks.
+
     Args:
         message: The message chunk to translate.
 
     Returns:
         The derived content blocks.
     """
+    # For intermediate streaming chunks with tool_call_chunks,
+    # produce tool_call_chunk blocks
+    if message.tool_call_chunks and message.chunk_position != "last":
+        # Start with non-tool-call content from the base conversion
+        blocks = _convert_to_v1_from_genai(message)
+
+        # Remove any tool_call blocks added by _convert_to_v1_from_genai
+        # (they were derived from message.tool_calls which auto-parses tool_call_chunks)
+        blocks = [b for b in blocks if b.get("type") != "tool_call"]
+
+        # Add tool_call_chunk blocks from tool_call_chunks
+        for chunk in message.tool_call_chunks:
+            tool_call_chunk_block: types.ToolCallChunk = {
+                "type": "tool_call_chunk",
+                "id": chunk.get("id"),
+                "name": chunk.get("name"),
+                "args": chunk.get("args"),
+            }
+            if (idx := chunk.get("index")) is not None:
+                tool_call_chunk_block["index"] = idx
+            blocks.append(tool_call_chunk_block)
+
+        return blocks
+
+    # Final/aggregated chunk or no tool_call_chunks: use standard conversion
     return _convert_to_v1_from_genai(message)
 
 

libs/core/tests/unit_tests/messages/block_translators/test_google_genai.py

@@ -1,8 +1,11 @@
 """Tests for Google GenAI block translator."""
 
+from langchain_core.messages import AIMessageChunk
 from langchain_core.messages.block_translators.google_genai import (
+    translate_content_chunk,
     translate_grounding_metadata_to_citations,
 )
+from langchain_core.messages.tool import tool_call_chunk
 
 
 def test_translate_grounding_metadata_web() -> None:
@@ -216,3 +219,80 @@ def test_translate_grounding_metadata_multiple_chunks() -> None:
     assert (
         citations[1].get("extras", {})["google_ai_metadata"]["place_id"] == "places/123"
     )
+
+
+def test_translate_content_chunk_intermediate_streaming() -> None:
+    """Intermediate chunks should have `tool_call_chunk` in `content_blocks`."""
+    chunk = AIMessageChunk(
+        content=[],
+        tool_call_chunks=[
+            tool_call_chunk(name="my_tool", args='{"arg": "value"}', id="123", index=0)
+        ],
+        response_metadata={"model_provider": "google_genai"},
+        # No chunk_position set (intermediate chunk)
+    )
+
+    blocks = translate_content_chunk(chunk)
+    tool_blocks = [b for b in blocks if b.get("type") == "tool_call_chunk"]
+    assert len(tool_blocks) == 1
+    assert tool_blocks[0].get("name") == "my_tool"
+    assert tool_blocks[0].get("args") == '{"arg": "value"}'
+    assert tool_blocks[0].get("index") == 0
+
+
+def test_translate_content_chunk_final_chunk() -> None:
+    """Final chunks should have `tool_call` in `content_blocks`."""
+    chunk = AIMessageChunk(
+        content=[],
+        tool_call_chunks=[
+            tool_call_chunk(name="my_tool", args='{"arg": "value"}', id="123")
+        ],
+        response_metadata={"model_provider": "google_genai"},
+        chunk_position="last",  # Final chunk
+    )
+
+    blocks = translate_content_chunk(chunk)
+    tool_blocks = [b for b in blocks if b.get("type") == "tool_call"]
+    assert len(tool_blocks) == 1
+    assert tool_blocks[0].get("name") == "my_tool"
+
+
+def test_translate_content_chunk_multiple_tool_calls() -> None:
+    """Test intermediate chunk with multiple `tool_call_chunks`."""
+    chunk = AIMessageChunk(
+        content=[],
+        tool_call_chunks=[
+            tool_call_chunk(name="tool_a", args='{"a": 1}', id="1", index=0),
+            tool_call_chunk(name="tool_b", args='{"b": 2}', id="2", index=1),
+        ],
+        response_metadata={"model_provider": "google_genai"},
+    )
+
+    blocks = translate_content_chunk(chunk)
+    tool_blocks = [b for b in blocks if b.get("type") == "tool_call_chunk"]
+    assert len(tool_blocks) == 2
+    assert tool_blocks[0].get("name") == "tool_a"
+    assert tool_blocks[0].get("index") == 0
+    assert tool_blocks[1].get("name") == "tool_b"
+    assert tool_blocks[1].get("index") == 1
+
+
+def test_translate_content_chunk_with_text_and_tool_call() -> None:
+    """Test intermediate chunk with both text `content` and `tool_call_chunks`."""
+    chunk = AIMessageChunk(
+        content=[{"type": "text", "text": "Let me call a tool."}],
+        tool_call_chunks=[
+            tool_call_chunk(name="my_tool", args='{"arg": "value"}', id="123", index=0)
+        ],
+        response_metadata={"model_provider": "google_genai"},
+    )
+
+    blocks = translate_content_chunk(chunk)
+
+    text_blocks = [b for b in blocks if b.get("type") == "text"]
+    tool_chunk_blocks = [b for b in blocks if b.get("type") == "tool_call_chunk"]
+
+    assert len(text_blocks) == 1
+    assert text_blocks[0].get("text") == "Let me call a tool."
+    assert len(tool_chunk_blocks) == 1
+    assert tool_chunk_blocks[0].get("name") == "my_tool"