run_outside_async f schedules f to run at some point in the future, outside of Async, i.e. not during an Async cycle and without holding the Async lock. run_outside_async returns a deferred that is filled with the result of f. Use run_outside_async to wrap blocking Elisp functions, e.g. read-from-minibuffer. For such functions, Emacs, while waiting, will run timers and network handlers, and hence will run Async cycles. Because run_outside_async runs f outside of a Async, Emacs will be able to run cycles as needed. Also, because run_outside_async releases the Async lock, the Async scheduler thread will be able to run and request cycles.