Build an iOS app with Devin

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Before you start

• macOS VMs: Devin’s sessions need to run on macOS. If you’re on a Dedicated SaaS deployment, ask your account team to enable macOS VMs. See macOS support.
• A repository: create an empty repository (for example, habit-tracker) and give Devin access to it through your Git integration.
• Desktop mode: turn on Enable desktop mode in Settings > Customization so Devin can interact with the Simulator and record its testing. See Computer Use.

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Step 1: Prompt Devin to build the app

Build a SwiftUI iOS app called HabitTracker in this repo.

Requirements:
- Target iOS 17+. Use SwiftUI and the Observation framework.
- Main screen: a list of habits, each with a name, an SF Symbol icon, and
  a checkmark button that marks the habit done for today.
- Show the current streak (consecutive days completed) next to each habit.
- A "+" toolbar button opens a sheet to add a habit. Swipe to delete.
- Keep habits in memory for now. No persistence yet.

Project setup:
- Install xcodegen, swiftlint, and xcbeautify with Homebrew.
- Define the project in project.yml with XcodeGen. Commit project.yml
  and add the generated .xcodeproj to .gitignore.
- Add a unit test target with XCTest tests for the streak calculation.
- Make sure swiftlint passes.

Verification:
- Build and run the tests on the iPhone 17 simulator.
- Install and launch the app in the Simulator. Add two habits, mark one
  as done, and delete one. Record this and send me a screenshot of the
  main screen.
- Open a PR with a short summary and the screenshot.

• Names the platform version and frameworks, so Devin doesn’t guess the deployment target or architecture.
• Names the simulator device, so build commands use a destination that exists on the VM.
• Describes a concrete verification flow, so Devin tests the behavior you care about instead of only checking that it compiles.

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Step 2: Watch Devin build and test

1. Scaffolds the project: writes project.yml, the SwiftUI views, the habit model, and the test target, then runs xcodegen generate.
2. Builds and fixes errors: runs xcodebuild from its shell, reads the compiler output, and fixes errors until the build and tests pass.
3. Runs the app in the Simulator: boots the device and installs and launches the build:
   xcrun simctl boot "iPhone 17"
   xcrun simctl install booted <path-to-HabitTracker.app>
   xcrun simctl launch booted <bundle-id>
   
4. Tests the flow you described: taps through the app with Computer Use, checks the result on screen, and records the run.
5. Opens a pull request with the summary and screenshot.

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Step 3: Review and iterate

Persist habits and completion history with SwiftData so they survive app
relaunches. Add a test that inserts a habit into an in-memory model
container and verifies the streak. Relaunch the app in the Simulator to
confirm habits persist, then push to the same PR.

Add a UI test target with an XCUITest that adds a habit, marks it done,
and checks that the streak shows 1. Run it on the iPhone 17 simulator.

Support Dark Mode and Dynamic Type. Check the main screen in the
Simulator in dark appearance and at the largest accessibility text size,
and send screenshots of both.

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Step 4: Ship a beta to TestFlight

1. Set up App Store Connect: accept agreements, register the bundle ID, create the app record, create a beta group, and answer export compliance.
2. Create an App Store Connect API key and download its .p8 file.
3. Add Devin secrets: ASC_KEY_ID, ASC_ISSUER_ID, ASC_PRIVATE_KEY, and APPLE_TEAM_ID.
4. Allow network access to Apple’s servers if your organization uses a restricted network policy.

Archive the HabitTracker scheme and upload it to TestFlight. Use a build
number higher than the latest build in App Store Connect, add the build
to the "QA" beta group, and send me the build number when it's done.

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Tips

• Pin the toolchain: macOS images include more than one Xcode version. Use DEVELOPER_DIR or xcode-select in the blueprint to choose one. See Selecting an Xcode version.
• Store credentials as secrets: App Store Connect API keys, signing certificates, and private package registry tokens belong in Secrets. Devin reads them as environment variables.
• Allow package registries: if your organization uses a restricted network policy, make sure the macOS allowlist includes Swift Package Manager, CocoaPods, or any private registries your app uses. See Network access.
• Restart the Simulator after a wake: when a session sleeps and wakes, files survive but running processes don’t. Ask Devin to boot the Simulator again before testing.
• Ask for evidence: ask for screenshots or a recording of specific screens so you can check the UI without running the app yourself.

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Limitations

• Devin runs apps on simulators, not physical iPhones or iPads. To test on a device, install a TestFlight build.
• Timing and profiling results inside a VM don’t reflect real device performance.
• Containers run under software emulation on macOS VMs, so container-heavy work is slow.

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Next steps