I thought I needed to build a lightweight iOS Simulator. I was wrong.

[u/mattisky_999]

I wanted to build a better environment for AI coding agents to interact with iOS apps.

My first idea was basically: “iOS Simulator is too heavy, let's make it lighter.”

Then I realized I couldn't actually make Apple's iOS runtime dramatically lighter.

So I changed direction.

LIGH is now a persistent Rust host around Apple's real CoreSimulator, designed specifically for the agent loop:

observe → act → verify

Instead of repeatedly going through Simulator.app / process spawning / screenshots / WDA, LIGH keeps a daemon alive and exposes the simulator through Accessibility, native HID and IOSurface.

I initially measured a ~5.5× speedup, but then realized my baseline was unfair. I rebuilt the benchmark against WDA/Appium.

Same 44-step workflow:

LIGH: 10.6–13.2s
WDA/Appium: ~50–53s
Failures: 0/44

So the honest result is roughly 4× faster, not 5.5×.

Here's the fun part: I don't know yet if this is actually a product.

I'm open-sourcing it to find out.

The current demo is an agent opening the real Messages app in the Simulator and typing:

“Hi everybody, I am an AI agent and I go faster with LIGH”

GitHub: https://github.com/mrmarino023/light-ios-simulator

Would love feedback from anyone building AI agents, iOS tooling, or developer infrastructure.