jasonstong/codex-theme-studio

Codex Theme Studio is a local first visual theme editor for Codex Desktop on macOS. It lets you design a theme in a browser window, save it on your own machine, and apply it live to Codex through a restricted connection to the app, without editing Codex's installed files or being an official OpenAI product. The editor works as a studio you preview and adjust in real time. You can browse a read only library of built in themes plus your own saved ones, switch between light and dark variants, and add a background image in PNG, JPEG, or WebP up to 8 megabytes, with accent and text colors pulled automatically from the picture. Material controls adjust background blur, opacity, corner rounding, and dimming. You can edit the homepage headline, subtitle, and four shortcut card labels, then drag icons, text, and cards to reposition them, or hide any of them. The sidebar's brand text and its six built in entries can also be customized or hidden. Turning a theme on or off is reversible: pausing it only removes the tool's own changes and leaves the underlying Codex installation untouched. Under the hood, the browser based studio talks to a small local helper program over a token protected local API. The helper validates each theme against a strict schema, stores it as JSON plus an optional image, and applies it to Codex through a locked down connection that only accepts a fixed set of generated styling changes, never arbitrary code. The first time a theme is applied, Codex needs a normal restart so the helper can attach, after that, switching themes updates the running app without restarting it, and the helper automatically reapplies the current theme if the app's interface reloads on its own. To run it you need macOS, Codex Desktop already installed, and Node.js 22 or newer. Cloning the repository and running the start command launches a local web address protected by a one time token, which should not be bookmarked or shared. All theme files and images are stored only on your machine, with no remote servers, analytics, or cloud syncing involved, and deleting a theme only removes that theme's own folder.