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CMX is configured through its interactive terminal UI (run cmx) and a local config file (cmx.config.toml). Most users only need the CONFIG menu to connect agents and adjust preferences. Advanced users can edit the config file directly to tune gateway behavior such as compression thresholds and protected tools.

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Using the Terminal UI

Run cmx in your terminal to open the interactive interface. From here you can navigate menus, manage connections, and monitor live activity without touching any config files. Keyboard shortcuts for navigating the UI:

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CONFIG Menu

Open the CONFIG menu from the main CMX interface to manage all connection and preference settings. From CONFIG you can:
  • Connect or disconnect coding agents — set up Codex, OpenCode, or any other supported agent to route its requests through the CMX gateway.
  • Choose a provider per agent — select which model provider each agent should use when connecting through CMX.
  • Adjust preferences — toggle live activity display, enable reduced motion, and control automatic update checks.
Each provider listed in CONFIG shows its current connection status and available actions. Changes take effect immediately in the UI, though the connected agent typically needs a restart before it picks up the new routing.

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Config File (cmx.config.toml)

CMX stores its gateway configuration in a local cmx.config.toml file. Most settings are managed automatically by the terminal UI, but you can edit this file directly for fine-grained control.
Each key controls a specific aspect of gateway behavior:
  • port — the local port CMX listens on. Default is 17322. Your coding agent must point to this port when routing through CMX.
  • min_context_tokens — the session must exceed this token count before CMX considers compression. Default is 32000. Short conversations below this threshold are passed through unchanged.
  • preserve_tail_tokens — the most recent portion of context, up to this token count, is always kept intact and never compressed. Default is 12000.
  • protected_tools — tool calls matching these names, and their results, are never compressed. Defaults cover task, skill, write, and edit. Add any other tool names you want to protect.
  • client — the coding agent currently connected to CMX. Set automatically when you connect an agent through CONFIG.
  • provider — the model provider used for the connected agent. Set automatically through CONFIG.
Changes to cmx.config.toml take effect after restarting CMX. Run cmx stop followed by cmx start to apply updated settings.

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Background Service

CMX can run as a background process so it is always available during coding sessions without occupying a terminal window.
cmx start launches the gateway process in the background. cmx stop shuts it down cleanly. CMX does not install an auto-start service — you need to run cmx start again after a reboot if you want the gateway running. To run CMX in the foreground in the current terminal instead, use cmx serve.