Svelte Plugin for Streaming LLM Chats

The Goal

One newConnection() function that composes any streaming connection: WebSocket for local services, SSE for external APIs. Universal interface, provider-agnostic.

Current State

newConnection('websocket' | 'sse', url) handles both types of streams through the StreamConnection type.

WebSocket: Connect first, then send data over open socket. SSE: makes POST request with payload, consumes response stream through the web Response API.

The sendChat() client-side task is just to give you an idea of how you'd wire up the plugin to your UI. There's no client app or ui here.

Common Errors

SSE:

• "Please provide a payload for your SSE connection" - No payload provided to connect()
• "SSE connection failed with bad response: {status}" - HTTP error or (less commonly) there was no response body

Websocket:

• "Websocket not connected" - Usually happens when your connection tried to send data before connection opened.

Anything outside of these errors above will be thrown to your implementation.

What if I Want to Use Sveltekit Remote Functions?

Remote functions were launched with response-request patterns in mind. They cannot currently maintain persistent streaming connections. The Svelte Discord has hinted at adding a stream remote function type for SSE in the future, but use traditional server endpoints (+server.js/ts) for now.

IMPORTANT: Please do use +server.ts endpoints for your api key security!

To Do (January 2026)

There's no tests written for newConnection() yet so PRs with test coverage are more than welcome!