[Bug]: StrandsAgent does not forward inner tool call events when an agent is used as a tool (agent-as-tool)

[NicolasBelliard]

Pre-flight Checklist

• I have searched existing issues and this hasn't been reported yet.
• I am using the latest version AG-UI.

Describe the Bug

When using the agent-as-tool pattern (a Strands Agent wrapped as a tool of a parent agent), ag_ui_strands.StrandsAgent does not emit ToolCallStartEvent, ToolCallEndEvent, or ToolCallResultEvent for the tools executed by the inner sub-agent. The frontend has no visibility into sub-agent tool execution.

Steps to Reproduce

from strands import Agent, tool
from ag_ui_strands import StrandsAgent, StrandsAgentConfig, create_strands_app

# An inner agent with its own tools
inner_agent = Agent(tools=[some_tool_a, some_tool_b])

# Wrap the inner agent as a tool of the parent agent
@tool
async def research_agent(query: str):
    """A sub-agent that uses tools internally."""
    async for event in inner_agent.stream_async(query):
        yield event
    yield inner_agent.result

# Parent agent using the sub-agent as a tool
parent_agent = Agent(tools=[research_agent])

# AG-UI wiring
agui_agent = StrandsAgent(agent=parent_agent, name="MyAgent")
app = create_strands_app(agui_agent, config=StrandsAgentConfig())

# When parent_agent calls research_agent, and research_agent internally calls
# some_tool_a and some_tool_b, the frontend never receives
# ToolCallStartEvent / ToolCallEndEvent / ToolCallResultEvent
# for some_tool_a or some_tool_b.

Expected Behavior

Expected behavior

When a parent agent calls a sub-agent-as-tool, and that sub-agent executes its own tools, the frontend should receive the full tool lifecycle events (ToolCallStartEvent, ToolCallEndEvent, ToolCallResultEvent) for those inner tool calls — allowing the UI to show real-time progress.

Actual behavior

Only the parent-level tool call (the sub-agent itself) emits start/end/result events. All inner tool calls made by the sub-agent are invisible to the frontend — their events are never forwarded through the AG-UI event stream.

Environment

- `ag_ui_strands`: 0.2.3
- `strands-agents-sdk`: latest
- Python 3.12+

Screenshots

No response

Logs & Errors

Additional Context

Impact

The UI cannot show what the sub-agent is doing in real-time. For long-running sub-agents with multiple tool calls, the user sees a black box with no progress indication.