A Valheim AI companion that watches you play

Valheim is a long game, and many nights you play it alone. With Sei's Backseat mode, your AI companion watches you play, reacts when the troll shows up, and talks with you out loud on a voice call. It works on Mac and Windows, with no mod.

macOS Windows

Free to start · Open source

An illustration of Backseat. Your companion's avatar sits on top of your game, with captions of what they say.

Not a Valheim mod: what Sei is

Most Valheim AI companions are mods that add an NPC to your world, a Viking who follows you, chops wood, and fights. Sei is a separate desktop app instead. You share your screen, and your companion watches and talks with you on a voice call. There is no mod loader to install, nothing to add to your world or your server, and nothing to update when the game patches. Your companion cannot swing an axe for you. They watch, react, and talk.

What your companion does while you play

Reacts to what just happened. Each look is a handful of frames from the last six seconds, so they see the fight you just had or the tree that just fell, not a single still picture.
Hears the game. The sound comes along with the share. A sudden loud moment, like a fight starting, makes them take a look right away, and any speech in it is turned into text on your computer.
Answers when you talk. Ask whether your base needs another wall, or whether it is too late in the day to set out. Your questions come first.
Talks about the game. They know what the AI model behind them knows about Valheim, which is a fair amount for a game this widely played. It can still be wrong on exact recipes or numbers.
Saves clips. A boss down, a longship landing in one piece, or a tree falling on your head: they can save the last 15 seconds or so as a video and drop it in your chat.
Remembers you. They remember what was said earlier in the call, and can save what you tell them, so next time they know where your base is and what you were building.

How they say it depends on the companion. Sui teases you a little. One you make yourself can be calm, dry, or very Viking.

Valheim moments it is made for

Night falls and you are far from home. They noticed it is getting dark before you did, and they say so.
The corpse run. You died somewhere unpleasant and have to go back for your things. Someone keeps you company on the walk.
A storm at sea. The waves get big and the boat starts to creak. They ask if you really packed enough food.
Building the longhouse. You spend an hour on the roof. They have opinions about it.
The boss. You finally summon it. They are on the call for every try, and the clip of the win is in your chat.

Set it up for Valheim

Install Sei on your Mac or Windows PC and pick a companion, or make your own.
Start Valheim and load your world, or join a friend's server.
Press the Backseat button in a chat with your companion. Pick the Valheim window or your whole screen. The sound comes along too.
Play. Sharing starts a voice call. Talk whenever you like, or just let them watch.

On a Mac, allow Screen Recording for Sei the first time. Sei shows you where. Game sound needs macOS 13 or newer. If the shared picture comes up black, try the game's windowed or borderless mode, or share your whole screen instead of the window.

Honest limits with Valheim

Valheim 1.0 is new. Your companion knows what the AI model behind them knows, and that can be thin or wrong for content added in 1.0. What they see on your screen is always current.
It is not a guide. In an ordinary screen share your companion does not search the web. For a recipe or a boss location, check a wiki.
It looks, it does not play. They cannot press keys or move your character, and they do not read game memory or change game or world files.
It runs on a voice call and uses your allowance. Sharing ends when the call ends, and there is no pause button yet. Every look is a call to the AI model, so it draws on the same weekly allowance as chat. Backseat is in beta.
It hears your computer's sound, not only the game's. If you are on voice chat with friends, what they say can end up in the text your companion gets, and on speakers your microphone can pick it up too. Headphones help.

Everything else about Backseat, including what stays on your computer, is on the Backseat page.

Is it OK to use Sei with Valheim?

Sei never touches Valheim itself. It does not install a mod, read the game's memory, change game or world files, or press keys. It captures the window you share, the way a streaming app does. Valheim's end user license agreement from Coffee Stain Publishing (last updated 11 June 2025) lets you stream and record videos of your play, as long as it does not look like Coffee Stain endorses it. Sei is not endorsed by Iron Gate or Coffee Stain. We found no anti-cheat in Valheim and no rule about screen sharing or companion apps.

Last checked 2026-10-25. Rules can change, so check the current agreement if you are unsure.

Questions

Is this a Valheim mod?

No. Sei is a separate desktop app. It watches the screen you share and listens to its sound. Nothing is installed into the game, your world, or your server, so game updates do not break it.

Can my companion join my Valheim world as a player?

No. Your companion does not appear in the game, fight, or carry anything. They watch your screen and talk with you. If you want a companion who plays beside you in the world, Sei does that in Minecraft, Stardew Valley, and Don't Starve Together.

Does it work when I play Valheim with friends?

Yes. Your companion watches your screen whether you play alone or on a friend's server. Nothing is added to the server, so your friends do not need anything. Your companion talks with you, not with them, but the sound Sei listens to is your computer's sound, so if your friends are on voice chat, your companion may hear them too.

Does it work on Mac?

Yes. Sei runs on Mac and Windows, and so does Valheim. On a Mac you allow Screen Recording for Sei once, and game sound needs macOS 13 or newer.

Does my companion know Valheim 1.0?

They know what the AI model behind them knows. The early access years of Valheim are well covered, but content new in 1.0 may be thin or missing. What they see on your screen is always current, and they do not search the web during an ordinary screen share.

Will Valheim treat Sei as a cheat?

Sei does not touch the game. It does not read game memory, change files, or press keys, and it sees only the window you share. As of 2026-10-25 we found no anti-cheat in Valheim and nothing in its license agreement about screen sharing apps. A server run by someone else can have its own rules, so ask the host if you are unsure.

Is it free?

You can start for free with no card. Backseat uses the same weekly allowance as calls and chat. You can also run Sei with your own API key or a local model, as long as the model can see images.

Try it

Download Sei, pick a companion, start Valheim, and press the Backseat button in your chat.