Claude Opus 4.6 vs Chatgpt 5.3 Codex

•  GPT-5.3 absolutely cooked on Terminal-Bench. 77.3% vs 65.4%, not even close. If you're running agents that need to hammer out CLI commands all day, this is the one. Speed is legit too — 25% faster and burns half the tokens for the same work.
•  Opus 4.6?? Near-human on OSWorld. 72.7% when humans score ~72%. GPT-5.3 is at 64.7% there. For anything where the model needs to actually think its way through a messy problem on a computer, Opus pulls ahead. 
• The 1M context thing is lowkey the biggest deal nobody's paying attention to. Opus scores 76% on needle-in-a-haystack at 1M tokens. That's not "we accept 1M and forget 90% of it" — it's actually tracking stuff across the whole input. 
• Every.to ran independent tests and found something that matches what I've been feeling too: Opus is better when you throw a vague problem at it and let it cook. GPT-5.3 is better when you write a tight spec and want precise execution.

I know most devs swear by Claude , Cursor or Gemini at this point.  and honestly I get it, I've been a Claude Code user for months. But I gave GPT-5.3 Codex a proper shot today and... it's actually really good?

Like the terminal stuff is noticeably faster. I threw a mid-size Node project at it (auth system, REST API, Postgres migrations) and it just went. Didn't overthink, didn't ask 15 clarifying questions, just shipped working code. That 25% speed boost they advertised feels real in practice.