Opus 5.5 vs GPT-6 Sol and Luna

Nathaniel Whittemore (0:00)

The first half of this week has seen not one, not two, not three, but four major model releases, including two on Tuesday this week, a pair from OpenAI and one from Anthropic. For OpenAI, GPT-6 Sol and Luna continued their quest to build cost-efficient models at every level of the intelligence stack. And for Anthropic, early indications suggest that Opus 5.5 is a return to glory, or at least early adopter acclaimed that the company has not seen since Opus 4.6.

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All right, friends, quick announcements before we dive in. Now, as is normal when it comes to big new model releases, this will be a main only episode. And honestly, we're going to have a hard time getting it all in even with that. So let's dive in.

Welcome back to the AI Daily Brief. It's fairly undeniable that the best days on the AI Daily Brief, certainly the most fun, exciting, dynamic, oh boy, I can't wait to be done with this episode because now I get to go do things types of episodes, are ones where we get new models. And yesterday, we got the absolute rarest of treats, a thing which I can't frankly remember ever happening before, which is the two most important labs of the moment, OpenAI and Anthropic, both releasing new models on the same day. Certainly, we've had models released close together before. In fact, usually the pattern that we see is what SpaceX AI did yesterday releasing their model in advance so as not to be drowned out by models that they knew would get more attention than them. The challenge of the same day release is that it inevitably gets people to ask not what's valuable about this particular model and where it's going to fit in my rotation, but instead, which of these is better and what does it say about which lab is in the lead. So today, we are going to go through what was released, where things stand on the benchmarks, the first reactions, examples around some particular use cases, the impact on the competitive landscape, what it says about the whole pacing the frontier thing, and in the community's estimation, who won the day.

The first model we got was Claude Opus 5.5. And frankly, it's been some time since an Opus class model was the big show. Now, the biggest reason for that is, of course, the introduction of Mythos and then Fable. But even before that, people had so much love for Opus 4.6, that 4.7 and 4.8 were, for many, if not a regression, certainly very incremental at best and not even incrementally ahead in certain cases. And in fact, when it came to Opus 5, people just genuinely did not like the thing at all. Now, jumping ahead to where this conversation is landing, the perfect encapsulation comes from AI content creator Peter Yang, who used a meme of an illustration of a horse, beautiful and complete at the beginning, representing Opus 4.6, of course, to a much scratchier, more simplistic and childlike line drawing for Opus 4.7 and Opus 4.8, culminating in near scribbles for Opus 5, to finally once again, the beautiful front side of a horse in perfect illustrated detail for Opus 5.5. The people, in other words, are really liking this model. But how did Anthropic pitch it? In their announcement post, they said that Opus 5.5 performs at the level of quad Fable 5.1 for most tasks, but costs 40 percent less to run, not even just in Fable 5.1, but then Opus 5

In their announcement thread, they point out that it is a major step up from Opus 5, but also frankly, at least when it comes to the benchmarks, it's also a step up from Fable 5.1.

On Terminal Bench 4.0, the model jumped from Fable 5.1's 55.8 percent to Opus 5.5's 66.4 percent. Cursor Bench, Frontier Code V11, and Humanities Last Exam also all saw jumps, not only from Opus 5, but from Fable 5.1 as well. In fact, there wasn't a single benchmark that Opus 5.5 wasn't ahead of the other Anthropic models, Fable 5.1 and Opus 5, and only two, Automation Bench, which measures business workflows, and Terminal Bench Science, which measures agentic scientific research, where Opus 5.5 wasn't ahead of GPT-6 Astra as well. Importantly, this is not just a performance gain, but also a pricing gain as well. The Cloud account wrote that because Opus 5.5 requires less compute to serve than Opus 5, its pricing is consequently down compared to Opus 5's $5 per million input tokens 25 per million output, Opus 5.5 is $4 per million input and $20 per million output. However, because of additional efficiencies, they said that the cost gains will actually be about 40% as opposed to just the 20% reflected in the cost.