Simon Willison’s Weblog

Introducing the Codex app. OpenAI just released a new macOS app for their Codex coding agent. I've had a few days of preview access - it's a solid app that provides a nice UI over the capabilities of the Codex CLI agent and adds some interesting new features, most notably first-class support for Skills, and Automations for running scheduled tasks.

The app is built with Electron and Node.js. Automations track their state in a SQLite database - here's what that looks like if you explore it with uvx datasette ~/.codex/sqlite/codex-dev.db:

Here’s an interactive copy of that database in Datasette Lite.

The announcement gives us a hint at some usage numbers for Codex overall - the holiday spike is notable:

Since the launch of GPT‑5.2-Codex in mid-December, overall Codex usage has doubled, and in the past month, more than a million developers have used Codex.

Automations are currently restricted in that they can only run when your laptop is powered on. OpenAI promise that cloud-based automations are coming soon, which will resolve this limitation.

They chose Electron so they could target other operating systems in the future, with Windows “coming very soon”. OpenAI’s Alexander Empiricos noted on the Hacker News thread that:

it's taking us some time to get really solid sandboxing working on Windows, where there are fewer OS-level primitives for it.

Like Claude Code, Codex is really a general agent harness disguised as a tool for programmers. OpenAI acknowledge that here:

Codex is built on a simple premise: everything is controlled by code. The better an agent is at reasoning about and producing code, the more capable it becomes across all forms of technical and knowledge work.

Claude Code had to rebrand to Cowork to better cover the general knowledge work case. OpenAI can probably get away with keeping the Codex name for both.