When the LLM returns multiple tool calls in one response, query.py
executes them concurrently via asyncio.gather. If more than one tool
requires user confirmation, each concurrent _ask_permission call emits
its own modal_request event. The React frontend overwrites its modal
state on every modal_request (setModal), so only the last dialog is
ever shown to the user. The earlier futures never receive a response
and time out after 300 s, causing silent "Permission denied" errors.
This edge case was not addressed by the recent deadlock fix (69c85e4).
Fix: add _permission_lock (asyncio.Lock) to ReactBackendHost and wrap
_ask_permission with 'async with self._permission_lock'. Only one
permission dialog is live at a time; the next concurrent caller waits
until the current modal is resolved or timed out.
Add test_concurrent_ask_permission_are_serialised to verify that two
concurrent _ask_permission calls are serialised and both resolve correctly.
Co-authored-by: Copilot
yl-jiang
55f7f8e906