Stability

fx is experimental. Its releases are numbered 0.0.x, and any release can change or remove commands, flags, settings, saved-data formats, and the libfx API. Each release's entry in the changelog lists the changes that need action from you under Breaking Changes.

fx also starts in auto permission mode, so it does most work without asking you first. Read Auto mode before you give it a task in a directory you can't restore.

What can change between releases

When a command, flag, or setting is renamed, the old name sometimes keeps working for a few releases. fx then prints a warning that names the replacement and the release where the old name stops working:

fx setup is deprecated and stops working in fx 0.0.18; use fx login vercel --api-key

Other old names are removed at once. Using one fails with an error that names its replacement, as fx resume does now.

fx converts conversations saved by earlier versions the first time you open them. See Sessions from earlier versions.

A newer libfx can save sessions and checkpoints that older versions can't open. When several workers share a session store, upgrade all of them before they start new turns. See Compatibility.

Control updates

fx installs updates in the background while it's open. To stay on one release, install that release and turn off automatic updates:

The dev channel follows changes as they merge, before they reach a release. See Use development releases.

Auto mode

In auto mode, fx reads and edits project files, searches, and runs recognized commands such as tests, builds, and dependency installs without asking. It sends other actions, such as unrecognized shell commands and MCP tool calls, to a review model first. That review holds an action only for prompt injection or for harm to your machine, so fx can still delete code or tests, push branches, and run scripts it wrote without asking you. Auto mode lists what runs directly and what gets reviewed.

The fx CLI doesn't run commands in a sandbox. Shell commands run with your user account's access. /undo reverts changes made by fx's file tools, but not shell commands or changes to external services, so keep work you care about in version control.

To approve each action yourself, switch to ask mode:

fx saves the mode you choose for later sessions. To use ask for one session only, start fx with fx --ask. See Permissions for the other modes and for rules that allow or deny specific actions.

Report a problem

Run /feedback to open the fx issue form. See Share feedback for traces and recordings that help reproduce a problem.