Launch HN: Bitrig (YC S25) – Build Swift apps on your iPhone

Hi HN, we’re Kyle, Jacob, and Tim. We’re building Bitrig (https://www.bitrig.app).

Bitrig lets you create native Swift apps for your phone, on your phone, just by chatting with AI. It’s like Lovable for iPhone apps.

Here's a video of Bitrig in action: https://youtu.be/CUlWhF3ERME

We created SwiftUI at Apple to help developers make better apps with less code. Bitrig lets anyone build at this level of polish. If you've thought about making an iPhone app, Bitrig is the easiest possible way to get started with Swift.

Bitrig uses Claude Sonnet 4.0 with a simple system prompt and tool definitions to generate native Swift code. Normally running this on an iPhone would require compiling and signing it with Xcode, and you can’t run Xcode on an iPhone. So we did something… creative. We wrote a custom Swift interpreter! Among other things this lets you instantly preview your app in Bitrig and share it with just a URL.

If you have a paid Apple developer account, you can connect it with Bitrig. We’ll compile your app on our server and upload it to App Store Connect, so you can distribute it on TestFlight or the App Store. This last step also gives you a fully optimized build of your app that you can install right on your Home Screen.

We think there’s something electric about building apps directly on your phone. We hope you give Bitrig a try!

We’re ingesting Apple’s SDK frameworks into Bitrig piece by piece. If you try to build something and hit a missing framework, let us know and we’ll prioritize adding it.

Download Bitrig on the App Store: https://apps.apple.com/us/app/bitrig/id6747835910

Very cool! Was it difficult to get Bitrig approved on the App Store? If I had to guess just based on the idea, it seems like the sort of thing Apple would take issue with.

Heh... it definitely wasn't an overnight approval. However, Apple has relaxed the guidelines for developer tools compared to the early days of the App Store. If you look today there are Python IDEs, Jupyter Notebooks, and various other apps that execute user generated code. The key guideline to be mindful of is 2.5.2.

Styling apps is an area we're excited to spend time exploring. Today in our system prompt we say "ALWAYS make the design Apple-like. Use clean typography and consistent padding/spacing." However, tbh it's not something we carefully tested.

For the most part, I think the look and feel of the apps benefits from SwiftUI baking Apple's design system into the defaults so heavily.

This is a really good idea, but I’ve noticed that, even with developer experience and using Claude code, building a complex app is extremely difficult and takes dozens of prompts to get things actually working. This is probably a great prototyping tool, but I’m curious to know how far this can go to build production level apps.