A Practical Codex Workflow for Building Your First Mobile App

1. Start with a repository map

Ask Codex to inspect the project and report the stack, entry points, navigation, data layer, environment variables, and available commands. Do not ask for feature work until you understand where the feature belongs.

2. Write an acceptance test before code

Describe what a user can do when the task is complete. Include success, loading, empty, offline, and failure states. For example: “A signed-in user can create a reminder, see it in the list, retry if saving fails, and still see a useful empty state when there are no reminders.”

3. Build the smallest vertical slice

Have Codex implement the screen, data operation, validation, and navigation needed for one complete flow. Avoid asking it to build an entire feature area in one pass. A vertical slice gives you something you can run and demonstrate.

4. Review the diff like a product owner

Check whether the change matches the intended user experience. Then review technical risks: duplicated logic, hardcoded secrets, missing authorization, unsafe input handling, and accidental changes outside the task.

5. Ask for targeted tests

Useful requests include:

• Add a test for invalid form input
• Test the loading and empty states
• Verify unauthenticated users cannot access the screen
• Run the formatter and the relevant package tests

You can use Claude Code, Cursor, GitHub Copilot, or another agent in the same way. The workflow is more important than the brand.

6. Keep the agent aligned

Maintain a short PROJECT_CONTEXT.md with product rules, commands, architecture decisions, and known limitations. This prevents repeated explanations and helps future sessions make consistent changes.

AI makes implementation faster. Your judgment still defines what should be built, what is safe to ship, and what users will trust.