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Your agents work on one plane: Steerholm. Your resources — files, repositories, databases, services — are connected to it. Your agents act on the plane; you control their actions on it, through policies. That is what an action plane for your agents, a control plane for you means — not two systems, but two faces of the same one.

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Everything on one plane

  • Resources are connected to the plane by their MCP servers — small connector programs that give agents tools for them. The plane runs those connections: it starts the ones it launches and connects to remote ones, keeps them up, and restarts one when you change it.
  • Agents join the plane: each is registered with an access key and the rules you grant it. Whatever an agent does with your resources, it does on the plane, and only as far as you granted.

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The action face

To an agent, the plane is where it acts. It joins with its access key at http://127.0.0.1:4767/mcp, sees the actions it is allowed — the tools of the resources it has been granted, and nothing else — and uses them.

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The control face

To you, the plane is where you control those actions. With holm you add agents and connect resources to it, and you grant each agent its rules: which actions, with which arguments (see Permissions). Your rules apply on the same plane, to the same actions, at the moment they happen:
  • Every action is checked against the agent’s rules before it reaches the resource. Anything not granted is refused, with the reason.
  • A change to a rule applies to the agent’s next action — there is nothing to restart. (The list of tools an agent sees refreshes when it reconnects.)
  • Every action, allowed or refused, is recorded. Read it with holm log — see the audit log.

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Why one plane

Control isn’t a separate system watching from the side — it is part of the plane where the action happens. A grant is a governed connection between an agent and a resource on the plane: the agent’s way to that resource and your rules for it are one and the same, so nothing reaches a resource around them. For how the plane carries a call from an agent to a resource’s MCP server, see Architecture.