The two controls
On the INPUT panel, "Auto-stop on silence" turns the feature on, and the slider below it, "Auto-stop after: 5 sec", sets how long the silence must last. New installs wait 5 seconds.
Silence here means no new speech. The hum of a fan or a busy office does not keep a recording alive.
Online engines: always on, one minute at most
With Soniox or Google, auto-stop cannot be switched off. The checkbox is grey and the slider goes from 5 to 60 seconds. This keeps a forgotten open microphone from running on: with Soniox every minute of a recording, pauses included, uses Pro credits.
Offline models: up to two minutes, or never
With a model on the LOCAL side, you choose. The slider goes from 5 to 120 seconds, and if you untick the checkbox the recording runs until you press the hotkey again. That suits long dictation with pauses to think.
Your offline setting is kept while you use an online engine and comes back when you return to LOCAL.
See it coming
When the silence is nearly over, the STATE line on the status screen counts down, for example SILENCE · STOP 4S. Say anything and the count starts again.
Recordings can also stop for two other reasons: you pressed the hotkey, or, on the free plan, today's 2,000 words are used up. The second case shows a message; see Free and Pro.