Something felt different in ChatGPT this week—and a lot of people noticed at once.
Across X, testers spent the past two days swapping screenshots and stopwatch times, all pointing to one theory: OpenAI is quietly A/B testing GPT-5.6 inside ChatGPT, swapped in for some users who select GPT-5.5 Pro.
Well well well, I'm one of the lucky ones with early GPT-5.6 Pro access!
The clearest pattern across the posts is time. Conor Dart, one of the many X users amplifying the rumors, ran the test with a one-prompt 3D browser game—with physics and camera controls—that took just over an hour to generate, versus GPT-5.5 Pro's usual 10-minute mark.
"Not perfect, but for a one-prompt AI game dev test, this is seriously impressive," Dart wrote.
Possibly GPT-5.6 Pro inside ChatGPT using GPT 5.5 Pro....
I ran the same style of game build after testing GLM 5.2, and this honestly felt a lot smoother.
The full game took literally 60 minutes and 15 seconds to create. ( GPT 5.5 Pro always responded with in a 10min mark)
In a separate post, he noted response times stretching to 20 or 40 minutes, a pace he said hadn't shown up since before GPT-5.5 shipped.
GPT 5.6 Pro first output on the same prompt
Not every comparison flattered the rumored model. Chris, an AI benchmarker on X, gave two models the same spaceship-building prompt—the suspected GPT-5.6 Pro worked for 87 minutes against GPT-5.5 Extra High's 34 minutes and 42 seconds.
None of it comes from OpenAI—but the details are consistent across accounts: stronger reasoning, an unfinished front end, and a release candidate nicknamed Kindle-Alpha.
If you're wondering how people on your timeline seem to have access to GPT-5.6 Pro, it's now being stealth tested when 5.5 Pro is selected in ChatGPT (*at least for some Pro accounts)!
I have also been told next Thursday is the planned launch date for 5.6
Decrypt reached out to OpenAI to ask whether GPT-5.6 is being tested inside ChatGPT, but the company did not respond by the time of publication.
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