Why iPhone apps cannot promise that an agent will run at a set time

Apple's Background Tasks framework lets an app ask for time to work while it is not on screen. A request can carry an earliest begin date, but the documentation is explicit that this is a floor and not an appointment: the system promises only that the task will not start sooner. For content refresh tasks, Apple says the system picks the launch time and allows up to 30 seconds of runtime. Heavier processing tasks are also launched at the system's discretion, and Apple suggests them for periods of low activity such as overnight charging.

A newer option, the continued processing task, behaves differently. It must begin in the foreground in response to a person's action, such as tapping a button, and can then keep running if the person leaves the app. The system shows its progress in a Live Activity, and the person can cancel the job from there.

For developers building planning or agent features, the practical consequence is to keep a user's deadlines and reminders as durable records and alerts, and to treat background refresh as opportunistic. An interface that says a job is scheduled for 6 a.m. is making a promise iOS does not back.