Server-Sent Events

Pro Feature

This feature is only available on paid plans. Please schedule a demo or email us to get started.

Fern’s SDKs support Server-Sent Events (SSE) out of the box. This feature is especially relevant for chat completions, where you want to stream LLM outputs in real-time.

TypeScript

Python

When an endpoint is configured to use Server-Sent Events, the TypeScript SDK method will return an AsyncIterable of the underlying data type. This allows you to use it in a for await loop.

Below is an example method signature for a stream endpoint:

1 import core from "../core";
2 
3 export interface ChatClient {
4 
5   /**
6   * Stream chat completions
7   * @param props 
8   * @returns An async iterable of chat completions
9   */
10   stream(
11     request: ChatStreamRequest, 
12     requestOptions: core.RequestOptions = {}
13   ): AsyncIterable<ChatCompletion>;
14 }

And here is an example of how a user would use the stream method:

1 const response = await client.chat.stream({
2   query: "What is the weather in New York?"
3 });
4 for await (const completion of response) {
5   console.log(completion);
6 }

Introduction

Getting Started

Features

Server-Sent Events

Pro Feature

TypeScript

Python

1	import core from "../core";
2
3	export interface ChatClient {
4
5	/**
6	* Stream chat completions
7	* @param props
8	* @returns An async iterable of chat completions
9	*/
10	stream(
11	request: ChatStreamRequest,
12	requestOptions: core.RequestOptions = {}
13	): AsyncIterable<ChatCompletion>;
14	}

1	const response = await client.chat.stream({
2	query: "What is the weather in New York?"
3	});
4	for await (const completion of response) {
5	console.log(completion);
6	}