How to plan agent coding projects

Non-trivial coding project? Planning is the most important part. Resist the urge to start building immediately.

Quick tips on planning:

1. Mindset: you're a product designer, talking to an engineer. Your job is to make a good plan.¹
2. Start by telling the agent about your problem—not the thing you think you want to build.
3. Ask the agent to brainstorm ways to solve the problem. Try requesting that brainstorm before you share your own thoughts on what to build.
4. If the agent is too eager to switch from thought partnership to building, use question mode.
5. After open discussion, switch to plan mode (Shift + Tab).
6. Review the agent's plan carefully. Ask it to explain things you don't understand, or that strike you as questionable.
7. Make big plans, so the agent can run independently for longer. Assign 10 tickets at a time, not 1.
8. Your plan should usually include "comprehensively test using Chrome" and "do code review". Make sure the agent can use Chrome. To test a browser extension, use this skill.
9. For web apps, use an agent-friendly framework like Convex.
10. For planning, Codex 5.4 is as good or better than Opus 4.6. YMMV.
11. For big projects, make a proper PRD. If you're doing this often, try ChatPRD.
12. When planning, consider using fast mode (/fast on). You'll save a bunch of time, and the cost may make you think harder.¹
13. For difficult projects, ask several models.