@langchain/protocol

@langchain/protocol

TypeScript bindings for the LangChain agent streaming protocol.

This package publishes the generated TypeScript schema bindings from protocol.cddl so TypeScript applications can type protocol commands, events, results, and content blocks consistently.

What this package includes

• Generated TypeScript protocol bindings in protocol.ts
• Types for top-level messages such as Command, Message, and protocol events
• Types for protocol modules including run, subscription, agent, input, state, and usage

What this package does not include

This package does not currently ship a runtime client, transport, or helper APIs. It is intended for typing protocol payloads and generated bindings only.

Installation

npm install @langchain/protocol

Usage

Use type-only imports when consuming the protocol schema:

import type {
  Command,
  Message,
  SubscribeParams,
  MessagesEvent,
} from "@langchain/protocol";

You can then use the exported types to model protocol payloads in your own transport or client implementation:

import type { Command, SubscribeParams } from "@langchain/protocol";

const params: SubscribeParams = {
  channels: ["messages", "lifecycle"],
};

const subscribeCommand: Command = {
  id: 1,
  method: "subscription.subscribe",
  params,
};

Source of truth

The canonical protocol definition lives at protocol.cddl. The TypeScript bindings in this package are generated from that schema.