Installation

Install Lumen from the App Store, or build it yourself from the source in Xcode.

Lumen is an iPhone app, and it needs iOS 18 or later. You can install it from the App Store or build it yourself from the source code.

From the App Store

The simplest route is the Lumen listing on the App Store. Installing it from there needs no developer account, and updates arrive the same way they do for any other app. Outside the App Store, the only way to get Lumen is to build it yourself.

Either way, the app downloads its language model later, the first time it needs the model, and that download needs about 1.2 GB of free space. First run explains when it happens.

Build from source

Building Lumen needs three things:

A Mac with Xcode 26.2 or later.
An Apple developer account, which Xcode uses to sign the app.
An iPhone on iOS 18 or later, or an iOS 18 simulator.

The language model does not run in the simulator. Pages still save to the library there, but without summaries, and Ask replies with fixed placeholder text in place of a real answer. Test anything involving summaries or answers on a physical iPhone.

Clone the repository

git clone https://github.com/Lux-Softworks/Lumen.git
cd Lumen

Open the project

Open Lumen.xcodeproj in Xcode, or run open Lumen.xcodeproj from the same folder. On the first open, Xcode fetches the four Swift packages the project depends on: mlx-swift, mlx-swift-lm, swift-readability, and SwiftSoup.

Sign it with your own team

The project arrives set to the original developer's team (XF6K537DNY), which your account cannot sign with. Signing is set in a file rather than in Xcode’s Signing & Capabilities tab. In the Configuration folder, copy Signing.local.example.xcconfig to Signing.local.xcconfig, then open the copy and set DEVELOPMENT_TEAM to your own team ID and LUMEN_BUNDLE_ID_PREFIX to a prefix of your own, such as com.yourname. Your team ID is listed under Membership details in your Apple Developer account. The app and both test targets read this file, and Git ignores it, keeping your team out of the repository.

Run it

Pick an iPhone or a simulator on iOS 18 or later as the destination, and press ⌘R. On a physical iPhone, the first launch may be blocked until you trust your developer profile under Settings → General → VPN & Device Management.

To run the tests, press ⌘U. Contributing covers the lint check every change has to pass and how to send a pull request.