Callstack ships a Codex plugin that puts iOS simulators and Android emulators beside the chat

Working with a coding agent on a mobile app meant three windows open at once: Codex, the simulator, and whichever log tail happened to be running. Callstack Incubator published a Codex plugin on 30 September 2026 that puts the simulator inside the Codex sidebar, so a mobile developer runs the whole loop in one window.

The plugin is on GitHub as callstackincubator/codex-mobile-dev-plugin. It had 90 stars at publication and installs through the Codex CLI marketplace. It supports iOS simulators, Android emulators, and physical devices, and the project description names React Native, Expo and SwiftUI as projects it is built for.

What it does inside Codex

The plugin brings five capabilities into the chat panel. Devices can be booted and controlled from a prompt. A tap or a drag can be scripted against the running simulator. An element inspector reads the accessibility tree and, for React Native projects, the component tree. A unified log view mixes iOS system logs, Android logcat and the Metro bundler output into one stream. A performance monitor records CPU, memory and display frames per second during a scripted session so the next run can be compared to it.

The repository's own examples in the README are the shape of a prompt a developer would send: "Build and run my Expo app in the simulator beside this chat" and "Record CPU and memory for 30 seconds while I scroll checkout." Both are routine tasks that would normally happen outside the editor.

Who ships it, and under what terms

The maintainer is Callstack Incubator, the open-source arm of the React Native consultancy that already ships Reassure, Flashlist and other mobile tooling. The repository was created on 30 September 2026, has 211 commits on main, and had been pushed to within the day. The licence field is empty on the repository metadata at publication, so a team planning to depend on it should check the LICENSE file before shipping anything that embeds it.

The scope of the plugin is also narrower than it may read. It streams the simulator and the device and reads from them. It does not sign releases, upload to a store, or run tests on its own. The capability is the window and the readouts, not the pipeline.

For a mobile team

The honest reading is that this is the piece that was missing. Codex already drafts code against a React Native or SwiftUI project, and the simulator already runs on the laptop. What was missing was a way to ask the agent to run what it has just written, read what the device shows, and compare one run against the next. Those three steps in one place are the saving. A team that already uses Codex for backend work gets a mobile loop without buying a second tool, and a team that writes mobile code day to day can hand off the parts that happen between the keystroke and the screenshot.

Source

Primary source: callstackincubator/codex-mobile-dev-plugin on GitHub.