cmux_move_surface

THE RISK

Medium Risk

Why cmux_move_surface needs a policy

This tool repositions/relocates a surface within the workspace hierarchy. It's a reversible modification (the surface can be moved back), so it fits Write. It doesn't delete data, execute code, or involve financial operations. The blast radius is medium since misuse could disrupt workspace layout and confuse active sessions.

From the tool's definition Move a surface to a different pane, workspace, or window

Documented attack patterns abuse exactly the kind of access cmux_move_surface gives an agent:

POLICY

How to control cmux_move_surface

PolicyLayer is an MCP gateway — it sits between your AI agents and Cmux Agent, and nothing reaches the server without passing your rules. This is the rule we recommend for cmux_move_surface:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "cmux_move_surface": {
      "limits": [
        {
          "counter": "cmux_move_surface_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

cmux_move_surface stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register Cmux Agent — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Cmux Agent tools

Destructive cmux_clear_notifications Clear all notifications. Destructive cmux_close_all Close ALL workspaces (or all except specific ones). Use Destructive cmux_close_surface Close a surface (tab). Destructive cmux_close_window Close a window. Destructive cmux_close_workspace Close one or more workspaces and all their panes. Pass a single ref or an array of refs. Execute cmux_browser_console Get or clear browser console logs/errors. Execute cmux_batch Execute multiple CMUX operations in a single MCP call. Each step references an existing cm Execute cmux_browser_eval Execute JavaScript in the browser page.

All 63 Cmux Agent tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about cmux_move_surface

What does the cmux_move_surface tool do? +

Move a surface to a different pane, workspace, or window. It is categorised as a Write tool in the Cmux Agent MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on cmux_move_surface? +

Register the Cmux Agent MCP server in PolicyLayer and add a rule for cmux_move_surface: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Cmux Agent. Nothing to install.

What risk level is cmux_move_surface? +

cmux_move_surface is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit cmux_move_surface? +

Yes. Add a rate_limit block to the cmux_move_surface rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block cmux_move_surface completely? +

Set action: deny in the PolicyLayer policy for cmux_move_surface. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides cmux_move_surface? +

cmux_move_surface is provided by the Cmux Agent MCP server (multiagentcognition/cmux-agent-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Cmux Agent tool call.

Start from Cmux Agent, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →