What deleting something removes

Deletes cascade downwards: deleting a container deletes everything inside it. There's no undo, so every delete dialog lists what goes with it before you confirm.

Deleting…	Also removes
A project	All its knowledge bases (with every file and folder), all its agents and their channels. For a project with content, you type its name to confirm.
A knowledge base	All its files and folders. Agents that used it stop answering clients until you choose another knowledge base for them; the dialog names them.
A folder	Everything inside it, including subfolders.
A file	Just that file (for a recording, its transcript). Agents stop using it within a minute or two.
An agent	All its channels. Telegram and WhatsApp stop answering, and the widget stops working on your site.
A channel	Just that connection. The agent and its knowledge base are unaffected.

To pause instead of deleting, Stop a channel on the assistant's Channels tab (open it under Assistants).

On Insights, a deleted agent's past messages are still counted, under Deleted agent.