The Snug Protocol · open spec · MIT
Describe a tiny app in chat and the agent writes it. It runs in a hard sandbox, thinks through the host agent at runtime, and lives — code, data, versions, chats — in one portable file you own.
the runtime agent bridge
A Snug app doesn't bundle a model — it sends versioned JSON envelopes to whatever agent its host runs, and animates the reply. Here is a chess app asking the host agent for its move, verbatim.
Thirteen frame types, all published as JSON Schemas. Read the wire protocol →
why it's different
Each app carries a compact runtime contract — what it is, what a good answer looks like — so its turns cost ~nothing and the same app runs well on a frontier model or a small local one. The agent plays chess with your app every move, forever.
Every app you build — code, versions, its own isolated database, its chats — lives in one portable .snug file (real SQLite, openable with ordinary tools, optionally sealed with a passphrase only you hold). Any hub, any LLM provider, sync where you choose. Leave whenever you like and take everything.
Apps run in a hard sandbox with zero network of their own. Your credentials never enter the app, never reach the LLM, never reach a publisher — every connected request goes through a host executor inside a ceiling you approved and the host froze.
try it
Snug runs entirely on your side of the screen — in a browser tab, or better, on your desktop where your smart home and your messages already live.
recommended
Completely private: your file on your disk, your keys or a local model, no account. And it reaches what a browser can't — Philips Hue on your LAN, your personal WhatsApp, Ollama running beside it.
.snug file, optional passphrase encryptionzero install
The hosted demo hub. Open a tab, describe a tiny app, watch the agent build it, run it in the sandbox — your file lives in the browser and exports whole whenever you want it.
for implementors
Your product already has an AI assistant. Snug makes it an app platform: users describe tiny apps in your chat, the assistant writes them, and they run in a hard sandbox against your agent — with their own storage, versioning, and a security model that has already been attacked in anger.
// a Snug app is one HTML file; the SDK is the bridge
const { isReady, sendMessage } = useSnugApp({ appId: 'ember-chess', displayName: 'Ember Chess' });
const db = useAppDB();
// the host agent is the app's brain — one call
const reply = await sendMessage('opponent-move', { lastMove: 'e7e5' });
// per-app isolated storage in the user's own file
if (reply.ok) await db.exec('INSERT INTO moves (san) VALUES (?)', [reply.data.move]);Software that's yours in the oldest sense: it sits with you, works for you, and fits in your pocket when you go.