If asyncio.CancelledError arrived during the heartbeat HTTP push inside
set_current_task() (the increment call), the code raised before entering
the try/finally block in _execute_locked. The finally block never ran,
so active_tasks stayed at 1 forever. Every subsequent heartbeat reported
active_tasks=1, the server saw active_tasks < max_concurrent_tasks as
false (1 < 1), and DrainQueueForWorkspace never fired. Queued A2A
requests were permanently stuck.
Fix: move set_current_task(increment) to be the FIRST statement inside
the try block, not before it. set_current_task's synchronous portion
(heartbeat.active_tasks mutation) still runs unconditionally; only the
optional HTTP push can be cancelled. The finally block now always runs
and always decrements active_tasks back to 0.
Affected executors: claude_sdk_executor, cli_executor, a2a_executor.
hermes_executor is not affected (does not call set_current_task).
Root cause of today's "active_tasks: 1 + queue drain never triggers"
P1 pattern across three workspaces.
All 167 executor tests pass.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
