The system card for GPT-5.5 mostly told us what we expected. See this thread from Drake Thomas for some comparisons to Anthropic's model card for Opus 4.7.

Now we move on to asking what it means in practice, and in what situations GPT-5.5 should become our new weapon of choice.

My answer is for some purposes yes, and for others no, but it is now competitive. GPT-5.5 is like GPT-5.4, only more so, and with improved capabilities in particular on raw intelligence and for well-specified coding and agent tasks, including computer use.

This is the first time since Claude Opus 4.5 came out, so in about four months, that I’ve considered a non-Anthropic model a competitive choice outside of some narrow tasks like web search. GPT-5.5 is not perfect, nor is it the best at everything, but basically everyone thinks this is a solid upgrade. Highly positive overall feedback.

My effective usage is now split between the two, depending on the nature of the task. If it's something that can be well-specified and all I want is the right answer, my instinct is I go with GPT-5.5. If I’m not sure what exactly I want [...]

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Outline:

(02:20) The Official Pitch

(07:49) Our Price Cheap

(08:29) Official Benchmarks

(11:58) SemiAnalysis Doublecheck

(12:38) Other Peoples Benchmarks

(16:00) Vend That Bench

(19:06) Planning Is Essential

(20:43) Choose Your Fighter

(22:44) Cyber Lack Of Security

(23:12) You Get What You Give

“GPT-5.5: Capabilities and Reactions” by Zvi