When a permanent agent has allowParallelExecution=false, TaskExecutor.execute()
defers if the agent has an active heartbeat run, and HeartbeatScheduler defers
a heartbeat if the agent's bound task has an active executor session. Each side
re-dispatches the other's deferred work on completion via resumeTaskForAgent
and the in-process runtime's onRunCompleted hook.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
