OpenAI dropped the 5.6 announcement and I've been going through what we actually know so far.
Three models: Sol, Terra, Luna. None are public yet so we're working off what OpenAI put out. From what they've shared, Terra is supposed to match 5.5 capability at about half the cost, Luna cheaper and faster but less capable. OpenAI is genuinely winning on the cost side right now. Anthropic keeps shipping smarter models but without the pricing coming down, and that gap is getting harder to ignore if you're doing high-volume API work.
The Sol vs. Mythos question is where I'm more skeptical. OpenAI is positioning Sol as a Mythos competitor, but the benchmark situation is not convincing. They're only showing a handful, they picked the ones where their model does well (which every model maker does), and when they do include Mythos in the comparison, it's Mythos Preview, which is over two months old. If Sol were actually in that territory it seems like it would be easier to demonstrate.
5.5 is already a capable model and 5.6 Sol looks like a real upgrade. But "comparable to Fable or Mythos" is a high bar and I don't think they've cleared it yet.
One thing worth remembering if you're on a subscription: you're already paying somewhere between 4% and 12% of actual API usage cost. So the raw cost comparison between the platforms matters a lot less if your work fits in a subscription tier. At that point you're mostly comparing model quality, and for anything ambitious, I still think Claude is the better call right now.
Fable 5 is supposed to be coming back soon too.
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