GPT-5.3 Codex VS Opus 4.6 : I TESTED BOTH Models EXTENSIVELY & ONE IS A CLEAR WINNER!

Description

In this video, I break down the massive release day where Anthropic dropped Opus 4.6 and OpenAI released GPT-5.3 Codex within an hour of each other. I analyze their official capabilities, run them through my custom KingBench suite, and put them head-to-head in real-world agentic coding scenarios to see which model actually reigns supreme for developers. -- Key Takeaways: 🔥 Opus 4.6 and GPT-5.3 Codex released simultaneously, bringing massive upgrades to agentic coding. 🤖 Opus 4.6 introduces adaptive thinking, a 1M token context window, and sustained agentic performance. 🛡️ GPT-5.3 Codex helped debug its own training and excels in cybersecurity, but currently lacks API access. 💯 Opus 4.6 scored a perfect 100% on KingBench, tying with Gemini 3 Pro for the top spot. 📉 GPT-5.3 Codex struggled in agentic tests, often using inefficient commands and failing to build functional apps. 🏆 Opus 4.6 dominated the agentic showdown, flawlessly building Svelte, Nuxt, and Expo apps. 💻 The verdict: Opus 4.6 offers a superior developer experience and is available now in Verdent and Kilo Code.