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What an agent is

An agent is a participant in the harness: a model, a set of tools it may call, a budget, and a body of instructions. Give it a task and it works until the task is done or the budget runs out. An agent decides what to do next based on what it just learned. It reads a file, notices a suspicious call, traces the caller, runs a command to check a hypothesis, and either confirms or discards it. That loop — reason, act, observe, reason again — suits security work, where the question is usually reachability: can an attacker actually get there?

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How a run proceeds

  1. The agent receives a task. In chat that’s your message; in a workflow it’s the task Console composes for that step.
  2. It reasons and calls tools. Each call returns a result it reads before deciding the next step.
  3. It may load a skill with activate_skill when it hits a task a documented procedure covers.
  4. It may delegate with spawn_agent, handing focused work to a child and waiting for the summary.
  5. It records durable results — findings, patches, detections — rather than only replying in prose.
  6. It stops when the task is done, the budget is exhausted, or it’s cancelled.
Everything an agent does in step 2 is bounded by the tool surface.

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Budgets

Two ceilings keep a run from going forever, both settable per agent:
  • maxIterations — how many reasoning↔tool cycles it may take.
  • timeout — wall-clock milliseconds for the whole execution.
For an orchestrator, timeout covers every child it spawns, so it must exceed the worst-case sum of their durations. Leave both unset unless the agent is genuinely an outlier.

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Delegation and agent trees

An agent can spawn sub-agents, and those can spawn their own, forming a tree. This exists for two reasons:
  • Focus. A child starts with a clean context scoped to one job, so a broad scan doesn’t drown in detail from the first file it opened.
  • Parallelism. Independent work runs concurrently — one evaluator per detection, one patch generator per file.
A child returns a summary, not its full transcript. The parent sees the conclusion and quotes it forward. This is why an agent’s description and its final summary both matter so much: they’re the interface between agents. You can watch the tree live — as a nested view in the CLI, and in the web console’s chat while a turn runs.

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Where agents come from

Both appear together wherever agents are listed, and a workflow treats them identically. An organization agent whose name matches a platform agent shadows it — the supported way to customize built-in behavior.

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When to write your own

Reach for a new agent when:
  • The task is a distinct job with its own output — “audit dependencies”, “review IaC for public exposure”.
  • You want different tool permissions, like a read-only reviewer that can’t modify code.
  • You want a different model for cost or depth reasons.
Prefer a skill instead when you’re capturing how to do one thing well and an existing agent could follow it. Skills are cheaper: no separate budget, no separate model, loaded only when relevant.

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Next steps

Write an agent

The frontmatter reference.

Chain them

Sequence agents into a workflow.