---
title: "What is a subagent in a coding agent?"
url: https://helicon.sh/glossary/subagent
description: "A subagent is a separate agent a main agent spawns to do part of the work in parallel. Why it saves wall clock time and why it is unreadable in a terminal."
updated: 2026-09-19
site: Helicon
---

# What is a subagent in a coding agent?

A subagent is a separate agent that a main agent spawns to handle part of a task, usually in parallel with others. It saves wall clock time on work that splits cleanly, such as searching several subsystems at once, and it produces interleaved output that a terminal cannot render legibly.

## When fan out helps

- Searching or reading across many files or subsystems.
- Reviewing one change from several independent angles.
- Any work where the parts do not depend on each other's results.

## When it does not

- Sequential work where each step needs the previous answer.
- Small tasks, where the coordination costs more than it saves.
- Anything where you need one consistent view of a file being edited.

## The rendering problem

Seven agents writing to one stream is not a log. A client that reads the protocol can show each subagent separately, cancel a run, or skip and retry an individual agent, which is the difference between a fan out you can supervise and one you can only hope about.

## Frequently asked questions

### Do subagents cost more?

They use more tokens in the same wall clock time. A per thread cost view makes the tradeoff visible.

### Can I stop one subagent?

In Helicon, yes. Individual agents in a workflow run can be skipped or retried, and the run can be cancelled on its own.

### Is a subagent a separate session?

It belongs to the parent thread. The session is still the thing you resume.

## Related

- [Subagents and workflows](https://helicon.sh/features/subagents-and-workflows): Parallel subagents and workflow runs are hard to follow in a terminal. Helicon shows them as structure: what is running, what finished, and what you can cancel or retry.
- [Background work](https://helicon.sh/features/background-tasks): Send a running tool call to the background, stop one, or stop them all. Cancel a workflow run, or skip and retry its agents, without abandoning the thread.
- [Cost at API rates](https://helicon.sh/features/cost-and-usage): See what every Muse Code thread would have cost at published per token rates, broken down by day, by model and by thread. A meter reading on your subscription, not a bill.

---

Helicon is a free, MIT licensed, unofficial community client for Meta's Muse Code CLI. Not made, sponsored or endorsed by Meta. Source: https://helicon.sh/. Machine readable index: https://helicon.sh/llms.txt