A first-person comparison of Codex 5.3 and Claude Opus 4.6 on a real Java monolith: streaming bugs, tests, reviews, and vibe-coding risk.

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I copied the same Java project into two branches, gave Codex 5.3 and Claude Opus 4.6 the same vague prompt, and compared what actually survived tests, reviews, and real Telegram bot behavior.

The result: cheaper is better.