# Layer 8 · Agents

URL: https://justuju.org/layer/agents/

Systems that pursue a goal over many steps: plan, act with tools, check the result, repeat.

Gives the layer above: Completed multi-step tasks, not just single answers.
Needs from the layer below: Tools, retrieval and model calls arranged by Orchestration & Tooling.

## Concepts

- [The agent loop](https://justuju.org/concept/agent-loop/): Plan, act with a tool, observe the result, and repeat until the goal is met.
- [Agent harnesses](https://justuju.org/concept/agent-harnesses/): The program wrapped around a model that turns it into an agent: it runs tools, asks permission, manages context and keeps memory.
- [Coding agents](https://justuju.org/concept/coding-agents/): Agents that work inside a code repository: read files, make edits, run commands and tests, and iterate until the checks pass.
- [Computer & browser use](https://justuju.org/concept/computer-use/): Agents that operate a screen like a person: look at a screenshot, then click, type and scroll.
- [Multi-agent systems](https://justuju.org/concept/multi-agent/): Several agents with different roles or contexts work together on one task.

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