Sub-agent
Also called subagent
A separate agent that a coding agent hands one job to. It works in its own context and returns only a summary.
Everything a coding agent reads stays in its session and is re-sent with each request after it. A sub-agent moves the reading somewhere else. The main agent passes it one job, it searches, reads and runs things in a context of its own, and only its summary comes back.
That suits noisy jobs: a wide search, a long log, a test run. It suits poorly anything that depends on the conversation so far, because the sub-agent never saw it. Whatever matters has to be in the request it's given.
For example
"Find every call to the old payments client" goes to a sub-agent, which reads dozens of files and hands back a list of 14 call sites.
Put it to use
Where you'll meet sub-agent in ChatGPT, Gemini and Claude, how to use it there, and the mix-up most people make.
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