STS2 Twitch Overlay Mod

Broadcasts live Slay the Spire 2 game state to a Twitch extension so viewers can see your deck, relics, enemies, and more in real time.

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For players

Prerequisites

• Slay the Spire 2 (Steam)
• A Twitch account and channel

1. Install the mod

Copy both files into your STS2 mods folder:

C:\Program Files (x86)\Steam\steamapps\common\Slay the Spire 2\mods\

• TwitchOverlayMod.dll
• TwitchOverlayMod.json

2. Authenticate

Launch STS2. A default config file is created automatically at %APPDATA%\SlayTheSpire2\TwitchOverlayMod.config.json if one does not exist. A Twitch icon button appears on the main menu below the profile selector.

Color	Meaning
Purple	Not connected
Yellow	Connecting…
Green	Authenticated
Red	Error

Click the button — your browser will open for Twitch OAuth. After authorizing, the button turns green and the mod begins broadcasting.

4. Install the Twitch extension

Install the extension from the Twitch Extension Dashboard and activate it as a video overlay on your channel. Viewers will see your game state in real time.

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For developers — self-hosting

Use this section if you want to run your own EBS and register your own Twitch extension (e.g. to fork the overlay frontend or change the broadcast format).

Prerequisites

• A Netlify account
• A Twitch developer account at dev.twitch.tv
• Node.js
• .NET 9 SDK

1. Register a Twitch Extension

1. Go to dev.twitch.tv → Extensions → Create Extension
2. Set type: Video Overlay
3. Note your Client ID and Client Secret
4. Add an OAuth redirect URI:

   https://<your-netlify-site>.netlify.app/.netlify/functions/callback
   

2. Deploy the EBS to Netlify

cd ebs
npm install
npx netlify deploy --prod

Alternatively, connect the repo in the Netlify dashboard and it will deploy automatically.

Then in Netlify dashboard → Site configuration → Environment variables, add:

Variable	Value
CLIENT_ID	Twitch extension client ID
CLIENT_SECRET	Twitch extension client secret
TWITCH_EXTENSION_SECRET	Base64-encoded extension secret (from the Twitch dev console, not the client secret)

The three serverless functions are:

Endpoint	Role
/.netlify/functions/auth	Starts the OAuth flow
/.netlify/functions/callback	Exchanges code, mints JWT, redirects to local callback
/.netlify/functions/refresh	Refreshes the broadcast JWT (30-day refresh tokens)

3. Build the mod

The project references STS2 game DLLs from the default Steam install path.

dotnet build

The output DLL is copied automatically to the STS2 mods folder on build.

4. Configure the mod to point to your EBS

In %APPDATA%\SlayTheSpire2\TwitchOverlayMod.config.json:

{
  "ebsUrl": "https://<your-netlify-site>.netlify.app",
  "extensionClientId": "<your Twitch extension client ID>",
  "broadcastIntervalSeconds": 2.0
}

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Broadcast payload

The mod sends a JSON payload every broadcastIntervalSeconds containing:

• Player — health, deck, relics, potions, gold
• Combat — enemies, intents, turn count
• Map — current location and map state
• UI — current screen

Cards, relics, enemies, and powers are referenced by sequential integer IDs defined in data/*.json. These IDs are assigned by the STS2 Content Exporter mod and must remain stable across exports.

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License

MIT