Chat SDK Durable Object State Adapater

Cloudflare Durable Object state adapter for chat. Provides persistent subscriptions, distributed locking, and key-value cache via a Durable Object (RPC only, no fetch handler).

Installation

pnpm add chat-adapter-state-durable-object chat

Setup

1. Export the Durable Object from your Worker and bind it in wrangler.toml. The DO uses SQLite storage (one row per subscription, lock, and cache entry), so you must use a SQLite-backed Durable Object:

// src/index.ts
export { ChatStateDurableObject } from "chat-adapter-state-durable-object";

# wrangler.toml
[[durable_objects.bindings]]
name = "EXPORTED_DO"
class_name = "ChatStateDurableObject"

# Required: enable SQLite for this DO class (run once, then optional to remove)
[[migrations]]
tag = "v1"
new_sqlite_classes = ["ChatStateDurableObject"]

2. Create the state adapter with a stub and pass it to Chat:

import { Chat } from "chat";
import { createDurableObjectState } from "chat-adapter-state-durable-object";

export default {
  async fetch(req: Request, env: Env, ctx: ExecutionContext) {
    // Get a stub - ID could be per tenant, or just a single DO.
    const stub = env.EXPORTED_DO.getByName("chat-state");

    const chat = new Chat({
      state: createDurableObjectState(stub),
      // ...adapters, handlers
    });

    // ...
  },
};

Optional logger for errors:

const state = createDurableObjectState(stub, { logger: myLogger });

API

• createDurableObjectState(stub, options?) – Returns a StateAdapter that forwards all operations to the Durable Object via RPC.
• ChatStateDurableObject – Durable Object class to bind.

Development

Tests use Cloudflare’s Vitest Workers integration and run against a real Durable Object (no mocks). Ensure wrangler.toml and src/worker.ts are present, then:

pnpm test

License

MIT