cmux_close · Cmux MCP: Risk & Policy

WHAT IT DOES

What cmux_close does on Cmux

AI agents use cmux_close to create or update resources in Cmux — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Cmux environment.

WHY IT NEEDS A POLICY

Why cmux_close needs a policy

An AI agent can call cmux_close faster than any human can review — one bad instruction and it creates or modifies resources in Cmux by the hundred, each call as confident as the last.

Risk signalsBulk/mass operation — affects multiple targets

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

cmux_close Rate-limited

cmux_close 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.

View as policy code

policy.json

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

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_close

What does the cmux_close tool do? +

Close a surface (tab) or an entire workspace. For kind. It is categorised as a Write tool in the Cmux 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_close? +

Register the Cmux MCP server in PolicyLayer and add a rule for cmux_close: 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_close? +

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

Can I rate-limit cmux_close? +

Yes. Add a rate_limit block to the cmux_close 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_close completely? +

Set action: deny in the PolicyLayer policy for cmux_close. 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_close? +

cmux_close 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.