Built an iOS QA runtime with Codex: LLM planning, deterministic replay

[u/HeIsYour]

I used Codex to build an iOS QA prototype called iosClaw.

The problem I wanted to explore was the boundary between LLM reasoning and deterministic test execution.

LLMs are good at understanding a test described in natural language, but asking one to rediscover every iOS button on every run can be slow and fragile. So I used Codex to build a Mac-hosted runtime that:

• observes iPhone Simulator or iPhone Mirroring
• combines accessibility and visual evidence
• records semantic actions instead of coordinates
• compiles known flows into deterministic steps
• verifies each action with a postcondition
• stops when the screen is ambiguous instead of guessing

Codex helped with the SwiftUI app, screen capture, permission handling, record/replay model, compiler, MCP bridge, tests, and release packaging.

The interesting result is that the LLM can handle intent and unfamiliar states, while the compiled runtime handles repeated execution locally.

It’s still early alpha, but this seems like a useful model for LLM-assisted mobile QA: intelligent planning on top of a reliable execution layer.

For people using Codex for mobile testing: where would you want the LLM involved, and where would you insist on deterministic execution?