Missing WebSocket / Subscription Support

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Missing WebSocket / Subscription Support

Description

The current implementation lacks WebSocket support for real-time subscriptions, which is a core feature of tRPC v10. While the subscription procedure type exists, it is not implemented. This prevents server-sent events or WebSocket-based real-time data streaming.

Current State

// In procedure.ts
subscription<TOutput>(
    resolver: (opts: { ctx: any; input: any }) => TOutput | Promise<TOutput>
): Procedure<...>

Issues:

• No WebSocket server implementation
• No subscription handler in dispatch.ts
• No client-side subscription link
• No observable/async iterator support
• No connection lifecycle management

Expected Implementation

Server-side:

• Add WebSocket adapter (packages/server/src/adapters/ws.ts)
• Update dispatch to handle subscriptions (executeSubscription)
• Add observable utilities (packages/server/src/observable.ts)

Client-side:

• Add WebSocket link (packages/client/src/links/ws.ts)
• Update proxy to handle subscriptions
• Add subscription types (packages/client/src/types.ts)

Impact

High priority — blocks:

• Real-time features (live updates, notifications, chat)
• Server-sent events
• Streaming data (logs, metrics, progress)
• Any push-based updates

Affected Files

Server:

• adapters/ws.ts (new)
• observable.ts (new)
• dispatch.ts (modify)
• procedure.ts (modify)
• types.ts (add Observable types)

Client:

• links/ws.ts (new)
• observable.ts (new)
• proxy.ts (modify for subscriptions)
• types.ts (add Observable types)

Example:

• example/src/server.ts (WebSocket server)
• example/src/client.ts (subscription demo)

References

• tRPC v10 subscriptions: https://trpc.io/docs/subscriptions
• WebSocket protocol: https://datatracker.ietf.org/doc/html/rfc6455
• Observable pattern: https://github.com/tc39/proposal-observable