Sleep and wake
A desktop uses memory and CPU even when nobody uses it. So a session that is not being used goes to sleep, and comes back when it is needed. This page describes what that looks like from your side.
When a session sleeps
A session sleeps after 15 minutes without use. Use means a live view that is open and visible, an MCP call in progress, or a file being moved. A session page left in a background tab stops counting after a minute.
An MCP client that is merely connected does not keep a session awake. Many clients hold a connection open all day; if that counted, no session would ever sleep.
What is saved
Before it sleeps, the session takes a snapshot of the running desktop: its memory as well as its files. Waking restores that snapshot. The screen comes back as it was, including what was typed into a form and where a page was scrolled to. An agent that returns the next day finds the task where it left it.
Sometimes there is no snapshot to restore, for example because taking it failed. The session then starts afresh from its disk. Chromium reopens the tabs it had and reloads them. Logins are kept, because cookies are on the disk. What existed only in a page's memory is gone.
Waking
Any real use wakes a sleeping session:
- Wake in the app,
- an MCP tool call,
- sending, saving or deleting a file.
The caller waits while the session wakes. An agent sees a slow call, not an error. If waking takes too long, the call answers with an error that says to retry.
Stop is different
Stop is you saying the session should stay off. A stopped session does not wake for an agent. Only Resume starts it.
Stop also takes no snapshot. Resuming starts the desktop from disk, as in the case above: tabs reload, logins are kept.
New sessions start quickly
The service keeps a few desktops running that belong to nobody yet. A new session takes one of them, so it is usually ready in seconds. When none is free, the session starts from scratch, which takes longer.