PET BUILDER
Build a little companion
with a big personality.
Choose a look, shape the details, and hatch a complete animated pet ready for ChatGPT, Codex and OpenPets.
FROM THE FOUNDRY
Three we made first.
LATEST DROPS
A new pet every day.
Get the drops.
One short email when new pets land or the foundry gains something worth knowing about. No other mail, unsubscribe in one click.
FAQ
Questions people actually ask.
What is Hatchery?
A free browser tool that turns a style, a character and a few details into a finished pet sprite pack. It draws the artwork, cuts every frame, builds the atlas, checks it against the format, and hands you a zip. No account, no install.
Which apps do these pets work in?
OpenAI Codex (desktop app and CLI) natively, and OpenPets, which brings the same pet to Claude Code, Cursor, OpenCode, Gemini CLI and Pi CLI. Any player that reads the Codex pet format works. See the install guide.
How much does it cost?
Nothing. Two hatches per person per day, plus a site wide daily cap, because every hatch costs us image generation.
Where do the files go?
Unzip the pack into ~/.codex/pets/ on macOS and Linux, or %USERPROFILE%\.codex\pets\ on Windows, then refresh pets in Codex Settings › Appearance › Pets.
What is the sprite sheet format?
A 1536 by 1872 transparent atlas: 8 columns by 9 rows of 192 by 208 cells, one row per animation state (idle, run right, run left, wave, jump, failed, waiting, working, review), plus a small pet.json manifest. It is validated against OpenAI's open-source checker before you download it.
Who owns the pet I hatch?
You do. Use it anywhere. If you submit it to the gallery it is shared with your name on it so others can install it too.
Why did my pet fail validation?
Usually one row came back with a detached effect or a missing pose. Re-hatch that single row from the result card; the rest of the pet is kept.
Do you keep my images?
The base pose is kept on the server for two hours so the animation rows can reference it, then deleted. Frame cutting, atlas composition and validation happen in your browser.