cmux_focus_pane · Cmux MCP: Risk & Policy

WHAT IT DOES

What cmux_focus_pane does on Cmux

AI agents invoke cmux_focus_pane to trigger actions in Cmux. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why cmux_focus_pane needs a policy

Focusing a pane triggers an external terminal/UI operation (changing window/pane focus in a terminal multiplexer). It's not a simple read and doesn't create/modify data, but it does trigger an external operation. The blast radius is low since it only changes UI focus state, which is easily reversible.

From the tool's definition Move focus to the given pane

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

cmux_focus_pane Rate-limited

cmux_focus_pane stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "cmux_focus_pane": {
      "limits": [
        {
          "counter": "cmux_focus_pane_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Cmux, so you can run agents against it safely.

FAQ

Questions about cmux_focus_pane

What does the cmux_focus_pane tool do? +

Move focus to the given pane. It is categorised as a Execute tool in the Cmux MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on cmux_focus_pane? +

Register the Cmux MCP server in PolicyLayer and add a rule for cmux_focus_pane: 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. Nothing to install.

What risk level is cmux_focus_pane? +

cmux_focus_pane is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit cmux_focus_pane? +

Yes. Add a rate_limit block to the cmux_focus_pane 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_focus_pane completely? +

Set action: deny in the PolicyLayer policy for cmux_focus_pane. 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_focus_pane? +

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