OpenAI put a Codex Edition of ModRetro's Chromatic handheld on sale through its Supply Co. merchandise store on November 9, 2026, the OpenAI Developers account (@OpenAIDevs) announced on X. The $200 device comes with one programmable cartridge, and it pairs with the ModRetro Chromatic plugin for Codex, OpenAI's coding agent, which builds Game Boy Color games from text prompts.
The plugin isn't new. ModRetro and OpenAI announced the partnership on September 29 at OpenAI's DevDay 2026, where attendees received a transparent DevDay Edition of the handheld, as The Shortcut and Generation Amiga reported the next day. The Supply Co. product page says the Codex Edition is that DevDay exclusive "back with a new look."
Alongside the sale, OpenAI published a walkthrough on its developer blog by Kevin Whinnery. In it, the plugin turns a single prompt into a GB Studio project, draws sprite sheets, and puts a scene's background next to its collision map so you can say which tiles the player can cross. Codex can run the ROM in an emulator in its built-in browser, play through a list of button presses and grab a frame after each one. The plugin can also compile C code with GBDK-2020.
To play on the hardware, you update the Chromatic's firmware, turn on Developer Mode and connect it over USB, then install the ROM on a rewritable homebrew cartridge. According to the blog, installing overwrites whatever game is on that cartridge and may wipe its save data, with no automatic backup.
OpenAI's developer site also hosts 13 games made with Codex for the Game Boy Color, including FlapGPT and Ember Escape. Each can be played in a browser or downloaded as a ROM.
Why it matters: it pairs an AI coding agent with a real, tightly limited retro target and a way to put the result on physical hardware. Because the projects are ordinary GB Studio and GBDK files, a developer can take over by hand at any point, and the emulator controls let the agent playtest its own work.
Caveat: we haven't tested the plugin or the device, and the claims about what it can build are OpenAI's own. The Supply Co. page ships to the US, Canada, Australia, New Zealand, Japan, the UK and the EU only.
As of November 10, the product page listed the Codex Edition as "Restock soon," with a restock expected on November 19.
