Definition
Plain language
A fresh helper AI spun up to do one specific job so the main assistant doesn't have to clutter its own memory with the details.
As stated in the literature
A separate model invocation with a newly constructed context, given a bounded delegated task; the delegated instruction is typically written into the sub-agent's user slot, discarding its original provenance.
Also called: sub-agents, subagent, subagents
Why it matters: Delegation keeps long tasks manageable, but the handoff rewrites the context from scratch, which is exactly where the origin of a piece of text can get lost.
For example, the main assistant hands off "summarize these forty log files" to a helper that reads them all and returns three sentences, keeping the bulk out of the main conversation.
Heard on the show
“Claude Code has subagents.”Episode 028 — Teaching a Model to Hire Copies of Itself: Recursive Agent Optimization