Subagent
Subagent: A helper the main agent hands part of a task to, working on it in its own separate context.
Not the same as a second session
A second session is another conversation you run yourself. A subagent is started by the main agent inside your session, works in its own context window, and hands back a summary: you see its result, not everything it read on the way.
Where it bites
It starts blank. A new subagent does not see your conversation, the files the main agent already read, or the constraint you agreed on three turns ago, so anything it needs has to be in the request it is given. Its work also counts toward the same usage limits as your main conversation.
Covered in these lessons
Related terms
Where this comes up
Also written as subagent, sub-agent. Checked 2026-10-22.