Build for iOS and macOS

Scaffold the app and build loop

For greenfield work, start with plain prompting. Ask Codex to scaffold a starter SwiftUI app and write a small build-and-launch script you can wire to a Build action in a local environment.

Keep the loop CLI-first. Apple’s xcodebuild can list schemes and handle build, test, archive, build-for-testing, and test-without-building actions from the terminal, which lets Codex stay in an agentic loop instead of bouncing into the Xcode GUI.

If you want a cleaner project generator and you’re comfortable with third-party tooling, Tuist is a good next step. It can generate and build Xcode projects without needing the GUI, while still letting Codex build and launch the app from the terminal.

Use XcodeBuildMCP once you’re inside a full Xcode project and need deeper automation. That’s when schemes, targets, simulator control, screenshots, logs, and UI interaction matter enough that plain shell commands stop being the whole story.

Leverage skills

For the first pass, you often don’t need a skill or MCP server. Add skills once the work gets specialized or you want stronger SwiftUI conventions baked into the run.

• SwiftUI expert is a strong general-purpose SwiftUI skill with a lot of best practices already baked in.

• SwiftUI Pro is a broad SwiftUI review skill for modern APIs, maintainability, accessibility, and performance.

• Liquid glass expert allows the agent to understand how the new iOS and macOS 26 Liquid Glass API work and fix your components so they look good on the latest versions

• SwiftUI performance is a great skill to use almost anytime you have a performance issue or doubt about some code as it will scan for the most common SwiftUI mistakes humans or agents make and produce a report with a priority list of what to fix and where the biggest gains are.

• Swift concurrency expert helps when cryptic errors and compiler warnings start fighting the change you want to make. On GPT-5.4, you may need it less often, but it’s still useful when Swift concurrency diagnostics get noisy.

• SwiftUI view refactor helps keep files smaller and make SwiftUI code more consistent across the repo.

• SwiftUI patterns helps reach for predictable @Observable and @Environment architecture patterns as the app grows.

To learn more about how to install and use skills, see our skills documentation.

Iterate

Once you have a first pass working, or if you’re starting from an existing project, you can start iterating on the UI or behavior.

For this part, be specific about what you want to change and how you want to change it.

Make that prompting layer explicit: tell Codex whether it’s working in a greenfield repo or an existing Xcode project, which platforms must keep working, and what validation loop you expect.

Example prompt

For example, if you want to add a feature to an existing app, you can ask Codex for a change like this:

Practical tips

Start with basics

Start with plain prompting for greenfield work. Ask Codex to scaffold a starter SwiftUI app and write a small build-and-launch script you can wire to a Build action in a local environment. For that first pass, you often don’t need any skill or MCP server.

Use a small trustworthy validation loop

Tell Codex to run after each change the narrowest command that actually proves the contract you touched. Expand to broader builds later. This keeps Codex fast without pretending a full app build is required for every edit.

Keep the loop CLI-first

Keep the loop CLI-first. Apple’s xcodebuild tool can list schemes and run build, test, archive, build-for-testing, and test-without-building actions from the terminal, which lets Codex stay in an agentic loop instead of bouncing into the Xcode GUI.

Leverage XcodeBuildMCP

Use XcodeBuildMCP as soon as you are inside a full Xcode project and need deeper automation. That’s the point where schemes, targets, simulator control, screenshots, logs, and UI interaction matter enough that plain shell commands stop being the whole story.