Code & Dev

I need to build [FEATURE NAME] in my [FRAMEWORK/LANGUAGE] project.

Context:
- Project stack: [e.g., Next.js 14, TypeScript, Supabase, Tailwind]
- The feature should: [describe behavior in plain English]
- It must NOT: [list constraints or things to avoid breaking]
- Existing related files: [list file paths]
- Auth/session context: [describe how auth works in this project]

Please:
1. List the files you'll create or modify before writing any code
2. Write the complete implementation with no placeholders
3. Include TypeScript types for all new data structures
4. Add inline comments only where logic is non-obvious
5. Write one Vitest unit test for the core logic

Do not ask clarifying questions — make the most reasonable assumption and note it.

Act as a senior software engineer doing a debugging session. I have a bug I cannot solve.

Here is what I know:
- Expected behavior: [DESCRIBE]
- Actual behavior: [DESCRIBE]
- Error message (if any): [PASTE]
- Relevant code: [PASTE]
- What I've already tried: [LIST]
- Stack: [LANGUAGE/FRAMEWORK/VERSION]

Your process:
1. Identify the 3 most likely root causes, ranked by probability
2. For each cause, explain the mechanism (why it would produce this exact symptom)
3. Give me the exact diagnostic step to confirm or rule out each cause
4. Once I confirm the cause, provide the minimal fix — no refactoring unless the bug requires it

Think step by step before answering.