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https://github.com/kriasoft/ws-kit

Type-safe WebSocket message routing & RPC for Bun, Cloudflare, and browser runtimes.
https://github.com/kriasoft/ws-kit

bun hono honojs http pubsub real-time schema server socket socket-io web websocket websockets ws zod zod-validation

Last synced: 26 days ago
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Type-safe WebSocket message routing & RPC for Bun, Cloudflare, and browser runtimes.

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README 

          
# WS-Kit — Type-Safe WebSocket Router



[![npm version](https://img.shields.io/npm/v/@ws-kit/zod.svg)](https://www.npmjs.com/package/@ws-kit/zod)

[![npm downloads](https://img.shields.io/npm/dm/@ws-kit/zod.svg)](https://www.npmjs.com/package/@ws-kit/zod)

[![GitHub Actions](https://github.com/kriasoft/ws-kit/actions/workflows/main.yml/badge.svg)](https://github.com/kriasoft/ws-kit/actions)

[![Chat on Discord](https://img.shields.io/discord/643523529131950086?label=Discord)](https://discord.gg/aW29wXyb7w)



Type-safe WebSocket router for Bun and Cloudflare with **Zod** or **Valibot** validation. Routes messages to handlers with full TypeScript support on both server and client.



## ⚠️ Environment Requirements



**WS-Kit is ESM-only** and optimized for modern runtimes:



- **Bun** (recommended) — native ESM and WebSocket support

- **Cloudflare Workers/Durable Objects** — native ESM support

- **Node.js** (with bundler) — requires Node 18+ and a bundler like Vite, esbuild, or Rollup

- **Browser** — works with modern bundlers



**Not compatible** with CommonJS-only projects or legacy runtimes.



## Monorepo Structure



WS-Kit is organized as a modular monorepo with independent packages:



- **`@ws-kit/core`** — Platform-agnostic router and type system (foundation)

- **`@ws-kit/zod`** — Zod validator adapter with `createRouter()` helper

- **`@ws-kit/valibot`** — Valibot validator adapter with `createRouter()` helper

- **`@ws-kit/bun`** — Bun platform adapter with `serve()` high-level and `createBunHandler()` low-level

- **`@ws-kit/cloudflare-do`** — Cloudflare Durable Objects adapter

- **`@ws-kit/client`** — Universal browser/Node.js client

- **`@ws-kit/redis-pubsub`** — Optional Redis PubSub for multi-server scaling



Combine any validator adapter with platform-specific packages. Each platform package (e.g., `@ws-kit/bun`) exports both high-level convenience (`serve()`) and low-level APIs (`createBunHandler()`).



### Key Features



**Server (Bun)**



- 🔒 Type-safe message routing with Zod/Valibot validation

- 🚀 Built on Bun's native WebSocket implementation

- 📡 PubSub with schema-validated broadcasts

- 🧩 Composable routers and middleware support



**Client (Browser)**



- 🔄 Auto-reconnection with exponential backoff

- 📦 Configurable offline message queueing

- ⏱️ Request/response pattern with timeouts

- 🔐 Built-in auth (query param or protocol header)



**Shared**



- ✨ Shared schemas between server and client

- ⚡ Choose Zod (familiar) or Valibot (60-80% smaller)

- 🔒 Full TypeScript inference on both sides



## Installation



Choose your validation library and platform:



```bash

# With Zod on Bun (recommended for most projects)

bun add @ws-kit/zod @ws-kit/bun

bun add zod bun @types/bun -D



# With Valibot on Bun (lighter bundles)

bun add @ws-kit/valibot @ws-kit/bun

bun add valibot bun @types/bun -D

```



## Quick Start



The **export-with-helpers pattern** is the first-class way to use WS-Kit —no factories, no dual imports:



```ts

import { z, message, createRouter } from "@ws-kit/zod";

import { serve } from "@ws-kit/bun";



// Define message schemas with full type inference

const PingMessage = message("PING", { text: z.string() });

const PongMessage = message("PONG", { reply: z.string() });



// Create type-safe router with optional connection data

type AppData = { userId?: string };

const router = createRouter();



// Register handlers — fully typed!

router.on(PingMessage, (ctx) => {

  console.log(`Received: ${ctx.payload.text}`); // ✅ Fully typed

  ctx.send(PongMessage, { reply: `Got: ${ctx.payload.text}` });

});



// Serve with type-safe handlers

serve(router, {

  port: 3000,

  authenticate(req) {

    const token = req.headers.get("authorization");

    return token ? { userId: "u_123" } : undefined;

  },

});

```



**That's it!** Validator, router, messages, and platform adapter all come from focused packages. Type-safe from server to client.



### Eliminating Verbose Generics with Declaration Merging



For applications with multiple routers, reduce repetition by declaring your connection data type once using TypeScript **declaration merging**. Then omit the generic everywhere — it's automatic:



```ts

// types/app-data.d.ts

declare module "@ws-kit/core" {

  interface AppDataDefault {

    userId?: string;

    email?: string;

    roles?: string[];

  }

}

```



Now all routers automatically use this type — no repetition:



```ts

// ✅ No generic needed — automatically uses AppDataDefault

const router = createRouter();



router.on(SecureMessage, (ctx) => {

  // ✅ ctx.ws.data is properly typed with all default fields

  const userId = ctx.ws.data?.userId; // string | undefined

  const roles = ctx.ws.data?.roles; // string[] | undefined

});

```



If you need custom data for a specific router, use an explicit generic:



```ts

type CustomData = { feature: string; version: number };

const featureRouter = createRouter();

```



### Do and Don't



```

✅ DO:  import { z, message, createRouter } from "@ws-kit/zod"

❌ DON'T: import { z } from "zod"  (direct imports cause dual-package hazards)

```



## Validation Libraries



Choose between Zod and Valibot — same API, different trade-offs:



```ts

// Zod - mature ecosystem, familiar method chaining API

import { z, message, createRouter } from "@ws-kit/zod";

import { serve } from "@ws-kit/bun";



// Valibot - 60-80% smaller bundles, functional composition

import { v, message, createRouter } from "@ws-kit/valibot";

import { serve } from "@ws-kit/bun";

```



### Quick Comparison



| Feature     | Zod                      | Valibot                  |

| ----------- | ------------------------ | ------------------------ |

| Bundle Size | ~5-6 kB (Zod v4)         | ~1-2 kB                  |

| Performance | Baseline                 | ~2x faster               |

| API Style   | Method chaining          | Functional               |

| Best for    | Server-side, familiarity | Client-side, performance |



## Serving Your Router



Each platform adapter exports both high-level convenience and low-level APIs. All approaches support authentication, lifecycle hooks, and error handling.



### Platform-Specific Adapters (Recommended)



Use platform-specific imports for production deployments — they provide correct options, type safety, and clear errors:



**High-level (recommended):**



```ts

import { serve } from "@ws-kit/bun";

import { createRouter } from "@ws-kit/zod";



const router = createRouter();

serve(router, { port: 3000 });

```



**Low-level (advanced control):**



```ts

import { createBunHandler } from "@ws-kit/bun";

import { createRouter } from "@ws-kit/zod";



const router = createRouter();

const { fetch, websocket } = createBunHandler(router);



Bun.serve({

  port: 3000,

  fetch(req, server) {

    if (new URL(req.url).pathname === "/ws") {

      return fetch(req, server);

    }

    return new Response("Not Found", { status: 404 });

  },

  websocket,

});

```



Benefits:



- **Zero runtime detection** — No overhead, optimal tree-shaking

- **Type-safe options** — Platform-specific settings built-in (e.g., port for Bun)

- **Clear error messages** — Misconfigurations fail fast with helpful guidance

- **Deterministic behavior** — Same behavior across all environments



**For Cloudflare Durable Objects:**



```ts

import { createDurableObjectHandler } from "@ws-kit/cloudflare-do";

import { createRouter } from "@ws-kit/zod";



const router = createRouter();

const handler = createDurableObjectHandler(router, {

  authenticate(req) {

    /* ... */

  },

});



export default {

  fetch(req: Request) {

    return handler.fetch(req);

  },

};

```



### Authentication



Secure your router by validating clients during the WebSocket upgrade. Pass authenticated user data via the `authenticate` hook — all handlers then have type-safe access to this data:



```ts

import { z, message, createRouter } from "@ws-kit/zod";

import { serve } from "@ws-kit/bun";

import { verifyIdToken } from "./auth"; // Your authentication logic



// Define secured message

const SendMessage = message("SEND_MESSAGE", {

  text: z.string(),

});



// Define router with user data type

type AppData = {

  userId?: string;

  email?: string;

  roles?: string[];

};



const router = createRouter();



// Global middleware for auth checks

router.use((ctx, next) => {

  if (!ctx.ws.data?.userId && ctx.type !== "LOGIN") {

    ctx.error("UNAUTHENTICATED", "Not authenticated");

    return; // Skip handler

  }

  return next();

});



// Handlers have full type safety

router.on(SendMessage, (ctx) => {

  const userId = ctx.ws.data?.userId; // ✅ Type narrowed

  const email = ctx.ws.data?.email; // ✅ Type narrowed

  console.log(`${email} sent: ${ctx.payload.text}`);

});



// Authenticate and serve

serve(router, {

  port: 3000,

  authenticate(req) {

    // Verify JWT or session token

    const token = req.headers.get("authorization")?.replace("Bearer ", "");

    if (token) {

      const decoded = verifyIdToken(token);

      return {

        userId: decoded.uid,

        email: decoded.email,

        roles: decoded.roles || [],

      };

    }

  },

  onError(error, ctx) {

    console.error(`ws-kit error in ${ctx?.type}:`, error);

  },

  onOpen(ctx) {

    console.log(`User ${ctx.ws.data?.email} connected`);

  },

  onClose(ctx) {

    console.log(`User ${ctx.ws.data?.email} disconnected`);

  },

});

```



The `authenticate` function receives the HTTP upgrade request and returns user data that becomes `ctx.ws.data` in all handlers. If it returns `null` or `undefined`, the connection is rejected.



## Message Schemas



Use the `message()` helper directly — no factory pattern needed:



```ts

import { z, message } from "@ws-kit/zod";



// Define your message types

export const JoinRoom = message("JOIN_ROOM", {

  roomId: z.string(),

});



export const UserJoined = message("USER_JOINED", {

  roomId: z.string(),

  userId: z.string(),

});



export const UserLeft = message("USER_LEFT", {

  userId: z.string(),

});



export const SendMessage = message("SEND_MESSAGE", {

  roomId: z.string(),

  text: z.string(),

});



// With Valibot

import { v, message } from "@ws-kit/valibot";



export const JoinRoom = message("JOIN_ROOM", {

  roomId: v.string(),

});

```



Simple, no factories, one canonical import source.



### Request-Response Pairs with `rpc()`



For request-response patterns, use `rpc()` to bind request and response schemas together — no schema repetition at call sites:



```ts

import { z, rpc, createRouter } from "@ws-kit/zod";



// Define RPC schema - binds request to response type

const Ping = rpc("PING", { text: z.string() }, "PONG", { reply: z.string() });

const Query = rpc("QUERY", { id: z.string() }, "RESULT", { data: z.string() });



// With Valibot

import { v, rpc } from "@ws-kit/valibot";

const Ping = rpc("PING", { text: v.string() }, "PONG", { reply: v.string() });

```



The client auto-detects the response type from the RPC schema, eliminating the need to specify it separately on every request.



### RPC Handlers



Register RPC handlers with `router.rpc()` to use request/response pattern with `ctx.reply()` and `ctx.progress()`:



```ts

import { z, rpc, createRouter } from "@ws-kit/zod";



const GetUser = rpc("GET_USER", { userId: z.string() }, "USER_DATA", {

  name: z.string(),

  email: z.string(),

});



const router = createRouter();



router.rpc(GetUser, (ctx) => {

  const { userId } = ctx.payload;



  // Send terminal response (one-shot)

  ctx.reply({ name: "Alice", email: "alice@example.com" });

});

```



For streaming responses, use `ctx.progress()` for non-terminal updates before the final `ctx.reply()`:



```ts

const DownloadFile = rpc(

  "DOWNLOAD_FILE",

  { fileId: z.string() },

  "FILE_CHUNK",

  { chunk: z.string(), finished: z.boolean() },

);



router.rpc(DownloadFile, (ctx) => {

  const { fileId } = ctx.payload;



  // Send progress updates (non-terminal)

  ctx.progress({ chunk: "data...", finished: false });

  ctx.progress({ chunk: "more...", finished: false });



  // Send terminal response (final)

  ctx.reply({ chunk: "end", finished: true });

});

```



**Fire-and-forget vs RPC:**



- `router.on(Message, handler)` — Use `ctx.send()` for fire-and-forget messages

- `router.rpc(RpcSchema, handler)` — Use `ctx.reply()` (terminal) and `ctx.progress()` (streaming) for request/response



## Handlers and Routing



Register handlers with full type safety. The context includes schema-typed payloads, connection data, and lifecycle hooks:



```ts

import { z, message, createRouter } from "@ws-kit/zod";

import { JoinRoom, UserJoined, SendMessage, UserLeft } from "./schema";



type ConnectionData = {

  userId?: string;

  roomId?: string;

};



const router = createRouter();



// Handle new connections

router.onOpen((ctx) => {

  console.log(`Client connected: ${ctx.ws.data.userId}`);

});



// Handle specific message types (fully typed!)

router.on(JoinRoom, (ctx) => {

  const { roomId } = ctx.payload; // ✅ Fully typed from schema

  const userId = ctx.ws.data?.userId;



  // Update connection data

  ctx.assignData({ roomId });



  // Subscribe to room broadcasts

  ctx.subscribe(roomId);



  console.log(`User ${userId} joined room: ${roomId}`);

  console.log(`Message received at: ${ctx.receivedAt}`);



  // Send confirmation (type-safe!)

  ctx.send(UserJoined, { roomId, userId: userId || "anonymous" });

});



router.on(SendMessage, (ctx) => {

  const { text } = ctx.payload;

  const userId = ctx.ws.data?.userId;

  const roomId = ctx.ws.data?.roomId;



  console.log(`[${roomId}] ${userId}: ${text}`);



  // Broadcast to room subscribers (type-safe!)

  router.publish(roomId, SendMessage, { text, userId: userId || "anonymous" });

});



// Handle disconnections

router.onClose((ctx) => {

  const userId = ctx.ws.data?.userId;

  const roomId = ctx.ws.data?.roomId;



  if (roomId) {

    ctx.unsubscribe(roomId);

    // Notify others

    router.publish(roomId, UserLeft, { userId: userId || "anonymous" });

  }

  console.log(`Disconnected: ${userId}`);

});

```



**Context Fields:**



- `ctx.payload` — Typed payload from schema (✅ fully typed!)

- `ctx.ws.data` — Connection data (type-narrowed from ``)

- `ctx.type` — Message type literal (e.g., `"JOIN_ROOM"`)

- `ctx.meta` — Client metadata (correlationId, timestamp)

- `ctx.receivedAt` — Server receive timestamp

- `ctx.send()` — Type-safe send to this client only

- `ctx.assignData()` — Type-safe partial data updates

- `ctx.subscribe()` / `ctx.unsubscribe()` — Topic management

- `ctx.error()` — Send type-safe error messages



## Broadcasting and Subscriptions



Broadcasting messages to multiple clients is type-safe with schema validation:



```ts

import { z, message, createRouter } from "@ws-kit/zod";



const RoomUpdate = message("ROOM_UPDATE", {

  roomId: z.string(),

  users: z.number(),

  message: z.string(),

});



const router = createRouter<{ roomId?: string }>();



router.on(JoinRoom, (ctx) => {

  const { roomId } = ctx.payload;



  // Subscribe to room updates

  ctx.subscribe(roomId);

  ctx.assignData({ roomId });



  console.log(`User joined: ${roomId}`);



  // Broadcast to all room subscribers (type-safe!)

  router.publish(roomId, RoomUpdate, {

    roomId,

    users: 5,

    message: "A user has joined",

  });

});



router.on(SendMessage, (ctx) => {

  const roomId = ctx.ws.data?.roomId;



  // Broadcast message to room (fully typed, no JSON.stringify needed!)

  router.publish(roomId, RoomUpdate, {

    roomId,

    users: 5,

    message: ctx.payload.text,

  });

});



router.onClose((ctx) => {

  const roomId = ctx.ws.data?.roomId;

  if (roomId) {

    ctx.unsubscribe(roomId);

    router.publish(roomId, RoomUpdate, {

      roomId,

      users: 4,

      message: "A user has left",

    });

  }

});

```



**Broadcasting API:**



- `router.publish(scope, schema, payload)` — Type-safe broadcast to all subscribers on a scope

- `ctx.subscribe(topic)` — Subscribe connection to a topic (adapter-dependent)



```ts

import { z, message, createRouter } from "@ws-kit/zod";



type AppData = { userId?: string; roomId?: string };

const router = createRouter();



const JoinRoom = message("JOIN_ROOM", { roomId: z.string() });

const UserJoined = message("USER_JOINED", {

  roomId: z.string(),

  userId: z.string(),

});

const SendMessage = message("SEND_MESSAGE", {

  roomId: z.string(),

  message: z.string(),

});

const NewMessage = message("NEW_MESSAGE", {

  roomId: z.string(),

  userId: z.string(),

  message: z.string(),

});

const UserLeft = message("USER_LEFT", { userId: z.string() });



router.on(JoinRoom, (ctx) => {

  const { roomId } = ctx.payload;

  const userId = ctx.ws.data?.userId || "anonymous";



  // Store room ID and subscribe to topic

  ctx.assignData({ roomId });

  ctx.subscribe(roomId);



  // Send confirmation back

  ctx.send(UserJoined, { roomId, userId });



  // Broadcast to room subscribers with schema validation

  ctx.publish(roomId, UserJoined, { roomId, userId });

});



router.on(SendMessage, (ctx) => {

  const { roomId, message: msg } = ctx.payload;

  const userId = ctx.ws.data?.userId || "anonymous";



  console.log(`Message in room ${roomId} from ${userId}: ${msg}`);



  // Broadcast the message to all room subscribers

  ctx.publish(roomId, NewMessage, { roomId, userId, message: msg });

});



router.onClose((ctx) => {

  const userId = ctx.ws.data?.userId || "anonymous";

  const roomId = ctx.ws.data?.roomId;



  if (roomId) {

    ctx.unsubscribe(roomId);

    // Notify others in the room

    router.publish(roomId, UserLeft, { userId });

  }

});

```



The `publish()` function ensures that all broadcast messages are validated against their schemas before being sent, providing the same type safety for broadcasts that you get with direct messaging.



## Error handling and sending error messages



Effective error handling is crucial for maintaining robust WebSocket connections. WS-Kit provides built-in error response support with standardized error codes.



### Error handling with ctx.error()



Use `ctx.error()` to send type-safe error responses:



```ts

import { z, message, createRouter } from "@ws-kit/zod";



type AppData = { userId?: string };

const router = createRouter();



const JoinRoom = message("JOIN_ROOM", { roomId: z.string() });



router.on(JoinRoom, async (ctx) => {

  const { roomId } = ctx.payload;



  // Check if room exists

  const roomExists = await checkRoomExists(roomId);

  if (!roomExists) {

    // Send error with standardized code

    ctx.error("NOT_FOUND", `Room ${roomId} does not exist`, { roomId });

    return;

  }



  // Continue with normal flow

  ctx.assignData({ roomId });

  ctx.ws.subscribe(roomId);

});

```



### Standard error codes



The standard error codes (aligned with gRPC) are:



**Terminal errors (don't retry):**



- `UNAUTHENTICATED` — Authentication failed

- `PERMISSION_DENIED` — Authenticated but lacks rights

- `INVALID_ARGUMENT` — Invalid payload or schema mismatch

- `FAILED_PRECONDITION` — Operation preconditions not met

- `NOT_FOUND` — Resource not found

- `ALREADY_EXISTS` — Resource already exists

- `ABORTED` — Operation aborted



**Transient errors (retry with backoff):**



- `DEADLINE_EXCEEDED` — Request deadline exceeded

- `RESOURCE_EXHAUSTED` — Rate limit, backpressure, or quota exceeded

- `UNAVAILABLE` — Service temporarily unavailable



**Server & evolution:**



- `UNIMPLEMENTED` — Feature not implemented

- `INTERNAL` — Server error

- `CANCELLED` — Request cancelled by client



See [ADR-015](docs/adr/015-error-handling.md) for the complete error code taxonomy.



### Custom error handling



You can add error handling middleware or lifecycle hooks:



```ts

// Error handling in connection setup

router.onOpen((ctx) => {

  try {

    console.log(`Client ${ctx.ws.data?.clientId} connected`);

  } catch (error) {

    console.error("Error in connection setup:", error);

    ctx.error("INTERNAL", "Failed to set up connection");

  }

});



// Error handling with middleware

router.use((ctx, next) => {

  try {

    return next();

  } catch (error) {

    ctx.error("INTERNAL", "Request failed");

  }

});



// Error handling in message handlers

const AuthenticateUser = message("AUTH", { token: z.string() });

router.on(AuthenticateUser, (ctx) => {

  try {

    const { token } = ctx.payload;

    const user = validateToken(token);



    if (!user) {

      ctx.error("UNAUTHENTICATED", "Invalid authentication token");

      return;

    }



    // Use assignData for type-safe connection data updates

    ctx.assignData({ userId: user.id, userRole: user.role });

  } catch (error) {

    ctx.error("INTERNAL", "Authentication process failed");

  }

});

```



## How to compose routes



Organize code by splitting handlers into separate routers, then merge them into a main router using the `merge()` method:



```ts

import { createRouter } from "@ws-kit/zod";

import { chatRoutes } from "./chat";

import { notificationRoutes } from "./notification";



type AppData = { userId?: string };



// Create main router

const mainRouter = createRouter();



// Compose with sub-routers

mainRouter.merge(chatRoutes).merge(notificationRoutes);

```



Where `chatRoutes` and `notificationRoutes` are separate routers created with `createRouter()` in their own files. The `merge()` method combines handlers, lifecycle hooks, and middleware from the composed routers.



## Browser Client



Type-safe browser WebSocket client with automatic reconnection, authentication, and request/response patterns — using the same validator and message definitions:



```ts

import { rpc, message, wsClient } from "@ws-kit/client/zod";



// Define message schemas

const Hello = rpc("HELLO", { name: z.string() }, "HELLO_OK", {

  text: z.string(),

});

const ServerBroadcast = message("BROADCAST", { data: z.string() });



// Create type-safe client with authentication

const client = wsClient({

  url: "wss://api.example.com/ws",

  auth: {

    getToken: () => localStorage.getItem("access_token"),

  },

});



await client.connect();



// Send fire-and-forget message

client.send(Hello, { name: "Anna" });



// Listen for server broadcasts with full type inference

client.on(ServerBroadcast, (msg) => {

  // ✅ msg.payload.data is typed as string

  console.log("Server broadcast:", msg.payload.data);

});



// Request/response with auto-detected response schema (modern RPC-style)

try {

  const reply = await client.request(

    Hello,

    { name: "Bob" },

    {

      timeoutMs: 5000,

    },

  );

  // ✅ reply.payload.text is fully typed from RPC schema

  console.log("Server replied:", reply.payload.text);

} catch (err) {

  console.error("Request failed:", err);

}



// Graceful disconnect

await client.disconnect();

```



You can also use explicit response schemas for backward compatibility (traditional style):



```ts

// Traditional: client.request(schema, payload, responseSchema, options)

const reply = await client.request(Hello, { name: "Bob" }, HelloOk, {

  timeoutMs: 5000,

});

```



**Client Features:**



- Auto-reconnection with exponential backoff

- Configurable offline message queueing

- Request/response pattern with timeouts

- Built-in auth (query param or protocol header)

- Full TypeScript type inference from schemas



See the [Client Documentation](./docs/specs/client.md) for complete API reference and advanced usage.



## Breaking Changes & Migration



### Validator is Required



The router now requires a validator to be configured. All imports should come from validator packages to ensure the correct validator is set up:



```ts

// ✅ Correct: Validator is included

import { createRouter } from "@ws-kit/zod";

const router = createRouter();



// ❌ Incorrect: Will throw if no validator is set

import { WebSocketRouter } from "@ws-kit/core";

const router = new WebSocketRouter(); // ← Error: validator is required

```



**Migration:** Always import `createRouter()` from `@ws-kit/zod` or `@ws-kit/valibot`, not from `@ws-kit/core`.



### Heartbeat is Now Opt-In



Heartbeat is no longer enabled by default. Enable it explicitly if you need client liveness detection:



```ts

import { createRouter } from "@ws-kit/zod";

import { serve } from "@ws-kit/bun";



const router = createRouter();



serve(router, {

  port: 3000,

  heartbeat: {

    intervalMs: 30_000, // Ping every 30s (default)

    timeoutMs: 5_000, // Wait 5s for pong (default)

    onStaleConnection(clientId, ws) {

      console.log(`Connection ${clientId} is stale, closing...`);

      ws.close();

    },

  },

});

```



**Migration:** Add `heartbeat` config to `serve()` options if you previously relied on default heartbeat behavior.



### PubSub is Lazily Initialized



PubSub (for `ctx.publish()` and subscriptions) is now created only on first use. Apps without broadcasting incur zero overhead.



**Migration:** No action needed. Broadcasting works the same way; initialization is just deferred.



## Design & Architecture



See [Architectural Decision Records](./docs/adr/) for the core design decisions that shaped ws-kit, including type safety patterns, platform adapters, and composability.



## Support



Questions or issues? Join us on [Discord](https://discord.gg/aW29wXyb7w).



## Backers



              



## License



This project is licensed under the MIT License. See the [LICENSE](LICENSE) file for details.