# Background agent

**Source:** https://promtable.com/glossary/background-agent

> A background agent is an LLM-driven worker that runs asynchronously — receives a task, executes for minutes/hours without a user attached, posts results when done. Cursor's Background Agents, Claude Code's async tasks, Devin are 2026 examples.

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A background agent is an LLM-driven worker that runs asynchronously — receives a task, executes for minutes/hours without a user attached, posts results when done. Cursor's Background Agents, Claude Code's async tasks, Devin are 2026 examples.

Synchronous chat agents block the user while running. Background agents flip that: queue a task ('fix this issue', 'review this PR', 'write this report'), the agent runs in a sandbox ([[agent-sandbox]]) for minutes or hours, results post to a channel / PR / inbox when ready. The pattern unlocks longer reasoning chains, more thorough multi-step work, and parallelism (10 agents on 10 issues at once). Production examples in 2026: Cursor Background Agents, Claude Code task queue, Devin, Replit Agents, Charlie Labs, Trae. Engineering challenges: durable execution ([[workflow-engine]]), credit / cost limits, prompt injection safety (background agents run with elevated permissions), result notification, and observability of long traces.

## When to use

- Long-horizon tasks where blocking the user is wasteful.
- Parallelizable work (review N PRs, fix M issues).

## Common mistakes

- Skipping sandbox — background agents run with elevated trust, blast radius is huge.
- No cost cap — runaway agent can burn $100s before anyone notices.

## Related terms

- [agent-sandbox](https://promtable.com/glossary/agent-sandbox)
- [workflow-engine](https://promtable.com/glossary/workflow-engine)
- [stateful-agent](https://promtable.com/glossary/stateful-agent)

*Last updated: 2026-06-01*
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Original page: https://promtable.com/glossary/background-agent
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