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1chat is an iOS app that lets you chat with the DeepSeek-R1 model locally.

Designed with privacy and security in mind, 1chat requires no internet connection or special permissions. It runs entirely on-device with an integrated model, ready to use right out of the box.

1chat is based on the open-source project fullmoon-ios, with custom development and integration of the DeepSeek-R1-Distill-Qwen-1.5B model.

It is fully compatible with DeepSeek R1 and supports deep thinking (DeepThink).

You can download 1chat from App Store

1chat can run on iPhone, iPad, Mac, and Vision Pro.

Features

• Built-in DeepSeek-R1 model(qwen-q4-1.5b), ready to use.
• Runs entirely offline—no internet required.
• Fully adapted for the R1 model.
• Supports multiple conversation management.
• Optimized for Apple chips.

Differences from fullmoon

1. Removed the system prompt(temporarily).
2. Localize for Chinese.
3. Removed the model downloader.
4. Currently supports only DeepSeek-R1 (temporarily).

How to build

Clone the repository

git clone https://github.com/OJZen/1chat.git

Download the model

Download DeepSeek-R1 model files from huggingface

Alternatively, you can use another model, but it must meet these requirements:

1. It must be a DeepSeek-R1 distill model.
2. It must be in MLX format.

The 1.5B model work best on my iPhone 15 pro -- it's fast enough for smooth performance.

Place the model

Place all model files into the model folder.

Xcode, launch!

Open the 1chat project in Xcode, then build and run.

Known issues

DeepSeek-R1 currently has an annoying issue where the output sometimes repeats endlessly.

I don’t know how to fix it, so for now, I’ve added a method that automatically truncates the output when repetition is detected.