I ran Claude Sonnet 4, Kimi K2, and Gemini 2.5 Pro on the same Next.js app and measured cost, speed, and whether the code actually shipped without follow-ups.

An in-depth comparison of Claude Sonnet 4 and Gemini 2.5 Pro Preview for AI-assisted coding, evaluating their efficiency, cost-effectiveness, and critical instruction adherence in real-world development workflows.