Crate nah_chat 

Introduction

This crate exposes an async stream API for the widely-used OpenAI chat completion API.

Supported features:

• Stream generation
• Tool calls
• Reasoning content (Qwen3, Deepseek R1, etc)

This crate is built on top of tokio, reqwest and serde_json.

use nah_chat::{ChatClient, ChatMessage};
use futures_util::{pin_mut, StreamExt};


let chat_client = ChatClient::init(base_url, auth_token);

// create and pin the stream
let stream = chat_client
       .chat_completion_stream(model_name, &messages, &params)
       .await
       .unwrap();
pin_mut!(stream);

// buffer for the new message
let mut message = ChatMessage::new();

// consume the stream
while let Some(delta_result) = stream.next().await {
  match delta_result {
    Ok(delta) => {
      message.apply_model_response_chunk(delta);
    }
    Err(e) => {
      eprintln!("Error occurred while processing the chat completion: {}", e);
    }
  }
}

Notice

Copyright 2025, Mengxiao Lin. This is a part of nah project. nah means “Not A Human”. Source code is available under MPL-2.0.

Structs

ChatClient

The object to hold information about the model server and reqwest HTTP client.

ChatCompletionParamsBuilder

A builder for creating parameters for chat completion requests.

ChatMessage

Data structure of a chat message, could be from the user, the assistant or the tool.

ChatResponseChunkDelta

Chunk delta of chat message from the assistant.

Error

Error type of nah_chat.

FunctionCallRequest

A function call request.

FunctionCallRequestChunkDelta

A function call request chunk received from stream api.

ToolCallRequest

A tool call request. Only function call is supported now.

ToolCallRequestChunkDelta

A tool call request chunk received from stream api.

TypedChatMessageContent

This is used to represent a message content that can have multiple types with a type annotation. Currently, it supports text and image_url.

URLObject

This is used to represent a URL in the message content. Currently, only images will be represented in this format.

Enums

ChatMessageContentValue

Type for message contents.

ChatResponseChunk

A chunk of chat message response from the assistant.

ErrorKind

Error kinds that may occur in nah_chat.

Type Aliases

Result