The fairest way to evaluate Cursor and Codex is to drop them into an existing production codebase. On one hand, you have a sprawling legacy repository with thousands of files, dependency drift, and nested architecture patterns. On the other hand, you have two AI systems designed to read, understand, and modify that complex codebase without breaking the existing features. The true test of these agents is not generating simple landing pages; it is safely making a structural change to a live system.
This workflow is where the two tools genuinely diverge. Cursor integrates AI directly into your editor visual canvas, making it a natural fit for real-time refactoring and interactive debugging. OpenAI Codex works as a CLI-driven terminal agent that targets parallel branch modifications and git worktrees directly from command-line prompts. When applying edits to production code, the choice between them hinges on whether you want an AI-first IDE or a terminal agent running commands on your branch.