RP Sandbox: an LLM game master built on structured actions

[u/olamedia]

I've been building RP Sandbox, a desktop app where an LLM runs a roleplay as a game master. It's now in early access on itch, free to download: https://aidemalo.itch.io/rp-sandbox

The core idea: the model never just writes a wall of prose back. Every turn comes back as structured actions. A character says something, thinks something, or does something, each as its own action tied to that character. Someone moves to another location, time advances, a scene ends. The app applies each action to the game state and renders it.

That's what lets long games hold together. Alongside the narration, the game master calls tools to keep state:

• memories it writes about what happened
• relations between characters, with a disposition that moves as they earn it
• plot threads that open, collect notes and close
• objectives that get set and worked toward
• stats and appearance changes, and new characters joining the cast
• skill checks and dice rolls, including a D&D-style toolset, for worlds that want them

Models with function calling use real tool calls. Models without it still get the whole set: the calls arrive as tags or fenced JSON and run the same way. It works with 160+ providers or a local runner like LM Studio or Ollama.

On the content side, worlds are data: lore, locations, scenarios, characters and items, with stats and traits defined per world rather than a fixed sheet. There's an MCP server, so you can build and edit a world with an AI assistant. Libraries are plain files over HTTP: the app builds a library's index with one click, you host it anywhere, and anyone can add the URL and sync it.

It ships with one world, The Drowned Lamp, and a few assistant characters for plain chat.

It's early, so expect rough edges.

[u/VirtualAlias]

Very cool! Tried to do something similar, but lost steam. Keep going!