Claude Code vs Codex: which is best?

Mike Cann compared Claude Code and Codex by having each build a React, Vite, and TypeScript collaborative project-management application using Convex, Supabase, and Firebase in isolated Docker environments. The six builds were evaluated for 40 functional requirements, security, and code quality, with additional runs measuring time and cost; manual functional testing was used after automated Playwright-based testing proved too unreliable. Claude Code generally produced more maintainable, modular, and better-typed code, receiving a code-quality grade one level above Codex across all backends, while Codex was typically two to three times faster and slightly cheaper overall. Both agents achieved full functionality with Convex and Supabase, though Firebase caused major difficulties: Claude Code exceeded the 45-minute limit and Codex required multiple repairs while still missing file-upload requirements. Security outcomes were broadly similar between the agents but varied substantially by backend, with Firebase earning D grades due to flawed authorization rules, Supabase receiving C grades for row-level-security weaknesses, and Convex receiving B grades because of unsafe file-serving behavior. Based on this benchmark, Convex appeared most suitable for AI-generated applications because its default transactions and reactive queries led to simpler front-end code and fewer severe authorization issues, although the author notes that results are limited to this application and methodology.

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