OpenAI just launched GPT-5.5. The OpenAI team was nice enough to give me early access over the last several weeks, and I just want to flag: there is a certain class of models (one that we’re hitting now) where unless you are deep in code or scientific research, you might not
GENERATIVE AI
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GPT-5.5 Available via Codex API Backdoor for Image Generation
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GPT-5.5 may not be in the official OpenAI API… but it's available via the apparently approved-of Codex API backdoor So I used that to make these pelicans (default and xhigh)! https://
simonwillison.net/2026/Apr/23/gp
t-5-5/
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GPT-5.5 Builds Playable Three.js Game in One Shot
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This is the game GPT-5.5 built for me in one shot, featured on the release page.
— Pietro Schirano (@skirano) 23 avril 2026
What makes it different from previous AI-generated games is how fun it actually feels to play.
The controls are smooth, and every shape is generated from scratch in Three.js. pic.twitter.com/dMQE2JbZvzThis is the game GPT-5.5 built for me in one shot, featured on the release page. What makes it different from previous AI-generated games is how fun it actually feels to play. The controls are smooth, and every shape is generated from scratch in Three.js.
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OpenAI Rolls Out Codex to Enterprise Customers
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we're rolling codex out to whole companies/enterprises. ping me gdb@openai.com if of interest!
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Anthropic Mythos vs GPT-5.5 CyberGym Benchmark Scores Compared
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Also, a detail some of you may have missed: Anthropic’s gated Mythos model scored 83% on CyberGym. OpenAI just dropped GPT-5.5 at 82%. Except GPT-5.5 is actually available for people to use.
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AI Models Automate Self-Jailbreaking Process Advancement
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I mentioned this project in this week's AI Lab newsletter. It suggests a kind of flip side to the idea of self-improvement in AI models. As models become more powerful, it shows they can automate the process of figuring out how to jailbreak themselves and other models remarkably
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New Model Uses Fewer Tokens While Maintaining Intelligence
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it quite literally uses much less tokens when compared to 5.4 – use it for awhile on some tasks and you'll see it doesn't have as big of difference on usage compared to the intelligence you get access too
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NVIDIA Advances Codex and GPT-5.5 Development at HQ
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Codex + GPT-5.5 is moving fast here at NVIDIA HQ.
— NVIDIA AI (@NVIDIAAI) 23 avril 2026
We’ve even got our own Codex Lab for NVIDIANs to get started. https://t.co/PTqytJWp0f pic.twitter.com/zWnSnKfansCodex + GPT-5.5 is moving fast here at NVIDIA HQ. We’ve even got our own Codex Lab for NVIDIANs to get started.
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Codex Ambassadors Program Now Open for Applications
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yes! we've got codex ambassadors program, apply if you haven't already!
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Claude 5.5 Outperforms Opus Beyond Frontend Work Analysis
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Having used both extensively, this doesn’t track with my experience. Aside from frontend work, 5.5 is leaps and bounds ahead of Opus. I don’t think this benchmark tells us anything useful anymore.