ADK Dev UI - Graph error

[weimeilin79]

** Please make sure you read the contribution guide and file the issues in the right place. **
Contribution guide.

Describe the bug
The agent graph was not displaying with LoopAgent
it was correctly displaying in ADK version 0.4.0, but throwing errors in 1.2.1

This is my Loop Agent, and one of my subagent

profile_agent = LlmAgent(
    name="profile_agent",
    model="gemini-2.0-flash",
    description=(
        "Agent to answer questions about the this person's social profile. User will ask person's profile using their name, make sure to fetch the id before getting other data."
    ),
    instruction=(
        "You are a helpful agent who can answer user questions about this person's social profile."
    ),
    tools=[get_person_posts,get_person_friends,get_person_id_by_name,get_person_attended_events],
)

.....

root_agent = LoopAgent(
    name="InteractivePipeline",
    sub_agents=[
        profile_agent,
        summary_agent,
        check_agent,
        CheckCondition(name="Checker")
    ],
    description="Find everyone's social profile on events, post and friends",
    max_iterations=10,
    after_agent_callback=modify_output_after_agent
)

Expected behavior
It was showing all the sub-agents and the tools with version 0.4.0
https://codelabs.developers.google.com/static/instavibe-adk-multi-agents/img/09-02-ui-graph_1920.png

Are there any breaking changes for defining the loop agent?

Desktop (please complete the following information):

• Python version(python -V): 3.12
• ADK version(pip show google-adk): 1.2.1

Additional context
Error Log

2025-06-05 03:44:42,998 - ERROR - __init__.py:157 - Failed to detach context
Traceback (most recent call last):
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/opentelemetry/trace/__init__.py", line 589, in use_span
    yield span
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/opentelemetry/sdk/trace/__init__.py", line 1105, in start_as_current_span
    yield span
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/opentelemetry/trace/__init__.py", line 454, in start_as_current_span
    yield span
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/google/adk/agents/base_agent.py", line 148, in run_async
    yield event
GeneratorExit

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/opentelemetry/context/__init__.py", line 155, in detach
    _RUNTIME_CONTEXT.detach(token)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/opentelemetry/context/contextvars_context.py", line 53, in detach
    self._current_context.reset(token)
ValueError: <Token var=<ContextVar name='current_context' default={} at 0x78357cf7dee0> at 0x783554416c80> was created in a different Context
INFO:     127.0.0.1:47558 - "GET /apps/social/users/user/sessions/380227d3-6e5b-4502-8d72-bcc13907b0e3 HTTP/1.1" 200 OK
INFO:     127.0.0.1:47404 - "GET /debug/trace/session/380227d3-6e5b-4502-8d72-bcc13907b0e3 HTTP/1.1" 200 OK
build graph
INFO:     127.0.0.1:47404 - "GET /apps/social/users/user/sessions/380227d3-6e5b-4502-8d72-bcc13907b0e3/events/mGzfci53/graph HTTP/1.1" 500 Internal Server Error
ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/uvicorn/protocols/http/h11_impl.py", line 403, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in __call__
    return await self.app(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/fastapi/applications.py", line 1054, in __call__
    await super().__call__(scope, receive, send)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/applications.py", line 112, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/middleware/errors.py", line 187, in __call__
    raise exc
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/middleware/errors.py", line 165, in __call__
    await self.app(scope, receive, _send)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 62, in __call__
    await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/routing.py", line 714, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/routing.py", line 734, in app
    await route.handle(scope, receive, send)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/routing.py", line 288, in handle
    await self.app(scope, receive, send)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/routing.py", line 76, in app
    await wrap_app_handling_exceptions(app, request)(scope, receive, send)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/starlette/routing.py", line 73, in app
    response = await f(request)
               ^^^^^^^^^^^^^^^^
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/fastapi/routing.py", line 301, in app
    raw_response = await run_endpoint_function(
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/fastapi/routing.py", line 212, in run_endpoint_function
    return await dependant.call(**values)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/google/adk/cli/fast_api.py", line 827, in get_event_graph
    dot_graph = await agent_graph.get_agent_graph(
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/google/adk/cli/agent_graph.py", line 286, in get_agent_graph
    await build_graph(graph, root_agent, highlights_pairs)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/google/adk/cli/agent_graph.py", line 267, in build_graph
    draw_node(agent)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/google/adk/cli/agent_graph.py", line 232, in draw_node
    build_cluster(cluster, agent, name)
  File "/home/meerabaelish_560773/instavibe-bootstrap/env/lib/python3.12/site-packages/google/adk/cli/agent_graph.py", line 150, in build_cluster
    draw_edge(parent_agent.name, agent.sub_agents[0].name)
              ^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'name'