tmux_split_window · Tmux MCP Server MCP: Risk & Policy

WHAT IT DOES

What tmux_split_window does on Tmux MCP Server

AI agents invoke tmux_split_window to trigger actions in Tmux MCP Server. 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 tmux_split_window needs a policy

Splitting a tmux window creates a new terminal pane, which is an execution-context modification. While it doesn't run arbitrary commands itself, it creates a new interactive shell pane in a live terminal session. This is an Execute-category action (triggering external terminal operations) rather than a simple Write, as it affects the live process environment.

From the tool's definition 'Split the current window in a tmux session horizontally or vertically to create a new pane' — creates a new pane in a tmux session, which is a terminal environment modification that triggers an external operation

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

tmux_split_window Rate-limited

tmux_split_window 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": {
    "tmux_split_window": {
      "limits": [
        {
          "counter": "tmux_split_window_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 Tmux MCP Server, so you can run agents against it safely.

FAQ

Questions about tmux_split_window

What does the tmux_split_window tool do? +

Split the current window in a tmux session horizontally or vertically to create a new pane. It is categorised as a Execute tool in the Tmux MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on tmux_split_window? +

Register the Tmux MCP Server MCP server in PolicyLayer and add a rule for tmux_split_window: 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 Tmux MCP Server. Nothing to install.

What risk level is tmux_split_window? +

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

Can I rate-limit tmux_split_window? +

Yes. Add a rate_limit block to the tmux_split_window 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 tmux_split_window completely? +

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

tmux_split_window is provided by the Tmux MCP Server MCP server (mediocretriumph/tmux-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.