UnboundLocalError: user_can_view referenced before assignment when on_shared_thread_view hook is not set (2.9.6)

[alexniculescu23]

Describe the bug
In Chainlit 2.9.6, the shared thread endpoint can crash with an UnboundLocalError because user_can_view is only assigned inside the optional @cl.on_shared_thread_view hook. When the hook is not defined / not executed, the code still evaluates (not user_can_view) and raises:
UnboundLocalError: cannot access local variable 'user_can_view' where it is not associated with a value.

This reproduces on a fresh install using the installed wheel at .venv/lib/python3.12/site-packages/chainlit/server.py (around line 1019).

To Reproduce
Steps to reproduce the behavior:

1. Install Chainlit 2.9.6 (fresh venv).
2. Create a minimal Chainlit app without defining @cl.on_shared_thread_view.
3. Start the server (e.g., chainlit run server.py).
4. Call the shared thread endpoint (example):

Open the share URL in the browser

5. See error.

Expected behavior
When @cl.on_shared_thread_view is not implemented, Chainlit should not crash. The request should be handled gracefully (e.g., return a 403/404 or a safe default behavior), and user_can_view should have a default value (e.g. False) before being checked.

Screenshots
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Desktop (please complete the following information):

• OS: wsl Ubuntu 22.04
• Browser chrome
• Version latest

Suggested fix/workaround: set a safe default before the optional hook runs, e.g. user_can_view = False prior to evaluating (not user_can_view).

Stack trace:
ERROR: Exception in ASGI application
Traceback (most recent call last):
File ".../site-packages/uvicorn/protocols/http/h11_impl.py", line 403, in run_asgi
result = await app(...)
File ".../site-packages/fastapi/applications.py", line 1054, in call
await super().call(scope, receive, send)
File ".../site-packages/starlette/routing.py", line 75, in app
response = await f(request)
File ".../site-packages/fastapi/routing.py", line 302, in app
raw_response = await run_endpoint_function(
File ".../site-packages/fastapi/routing.py", line 213, in run_endpoint_function
return await dependant.call(**values)
File ".../site-packages/chainlit/server.py", line 1019, in get_shared_thread
if (not user_can_view) and (not is_shared):
UnboundLocalError: cannot access local variable 'user_can_view' where it is not associated with a value

• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.

[github-actions]

This issue is stale because it has been open for 14 days with no activity.

[github-actions]

This issue was closed because it has been inactive for 7 days since being marked as stale.