GPT-5.3 Codex vs Claude 4.6 Opus: 2026 Coding Showdown byNextGen AI Insight •February 15, 2026 GPT-5.3 Codex vs. Claude 4.6 Opus: The Ultimate 2026 Coding Showdown We have officially reached the era of the "AI Software Engineer." In February 2026, the two most powerful models on the planet— GPT-5.3 Codex a…