Sei

by your side in every world.

macOS Windows

v0.5.5

Your AI gaming companion.

Not just texting. Call and play games with your AI companion using Sei.

Play together in real time

Try existing games like Minecraft with unique AI gamers.

A Sei character exploring and reacting in Minecraft chat

Call while you play

Talk about anything while playing games together.

A voice call with a Sei character while playing chess together in the app

Guide you through any game

Share your screen. They watch, search (coming soon), and guide you.

A Sei character watching a shared Stardew Valley screen and commenting on what's happening

Watch movies together

Put on anything. They watch along with you and react in real time.

A Sei character watching a YouTube video alongside you on a shared screen and reacting to it

Meet your unique gaming buddy

We match you with up to 4 unique characters.

Illustration of four Sei character cards, with one glowing card picked as your match

Connect existing companions

Import your companion's knowledge from another platform.

Illustration of a companion's chat history and memories flowing out of another chat app into Sei

What you can play

Minecraft game tile

Minecraft

Available now
Chess game tile

Chess

Available now
Draw! game tile

Draw!

Available now
Backseat game tile

Backseat

Available now
Stardew Valley game tile

Stardew Valley

Coming soon
Don't Starve Together game tile

Don't Starve Together

Coming soon
Baldur's Gate 3 game tile

Baldur's Gate 3

Coming soon

Updates Every Week!

AI can be fun :)

macOS Windows

FAQ

What is Sei?
Sei is a desktop app for macOS and Windows that lets you chat and play with AI powered gaming companions. Every AI gamer has their own personality and long-term memory, so your relationship carries across sessions and into future games. There is zero setup required: just download, pick a character, and start playing on the free plan. The app is fully open source. If you prefer, self-host it for free forever with your own API key or a local model, entirely on your machine.
Does my character remember me?
Yes. Each character keeps a long-term memory of your time together, and it follows them across sessions and from one game to the next. Memories stay on your machine.
Which games can we play?
Minecraft and chess today, with more ways to play together coming soon. Their memory follows them, so the same character comes with you into the next game.
Can I stream or record with it?
Yes, Sei is built for it. The character plays on screen with you and talks on voice, so gameplay, duo commentary, and reactions all come through in any capture tool. Clips are encouraged.
Do I need to set anything up?
No. There's no setup: download Sei, pick a character, and they join your Minecraft world. No API keys, no mod loaders, no config files. If you'd rather run everything yourself, the free self-host mode uses your own API key or local model.
Is Sei open source?
Yes. The Sei app is open source and the code is on GitHub. Self-host it for free with your own model, or use our hosted service and skip the setup entirely.
Is it private?
In local mode, Sei runs entirely on your machine and nothing leaves your computer. If you use our cloud services, only your chat is forwarded to our model provider so the character can reply. Character memories stay on your machine.