TL;DR
What did davedx (Hacker News) use Codex for?
A freelance developer wrote a spec and had Codex build a timesheet, invoicing and basic bookkeeping system for their business; they say it got everything right in one go except the PDF invoice layout. They say it "works pretty well" and Codex "one-shot the entire application except for the PDF invoice layout which needed iteration."
What they did
They used what they call spec-driven development: describe the whole app in a written spec, then hand it to Codex to build the timesheet entry, invoicing and bookkeeping pieces.
How it went
They say it "works pretty well" and Codex "one-shot the entire application except for the PDF invoice layout which needed iteration."
Worth knowing
- The poster is a developer, and the comment is short. Expect to iterate on anything visual, such as invoice PDFs.
Try it yourself
Paste this into a chatbot, then add your own details underneath.
Help me write a spec for a small app for my freelance business. It should log hours per client and project, turn unbilled hours into a numbered PDF invoice, track which invoices are paid, and export a simple income report for bookkeeping. Ask me questions until the spec is complete, then write it as a document I can give to a coding agent.
Original post
See davedx (Hacker News)'s original post on Hacker News → (Jun 9, 2026)
Sources
- davedx (Hacker News) on Hacker News, Jun 9, 2026 — the original post