I’m guessing Opus 4.8 to be based on the same pretrain as Opus 4.0
Opus 4.0 (and 4.1) is priced at $15/$75. Opus 4.5+ is priced at $5/$25. Opus 4.5 runs faster than 4.0 (i.e. for a given prompt, you get output tokens faster when running 4.5 than 4.0). This makes me think that Opus 4.5 is a significantly smaller model than 4.0.
Also of note is that Opus 3.0 is $15/$75 and all Sonnets are $3/$15.
I’m assuming Opus 4 targets Trainium 2 Ultra, necessary for both efficient serving and RL training. The buildout of this system was happening over 2025, so it wasn’t yet available in the times of Opus 4.0-4.1, which is why they were slow and expensive, and not properly RLVR-trained. By the time of Opus 4.5, Trainium 2 Ultra racks were probably sufficiently available to start serving it, after it was RLVRed either on Trainium 2 Ultra or on TPU v6e pods.
Opus 4.0 (and 4.1) is priced at $15/$75. Opus 4.5+ is priced at $5/$25. Opus 4.5 runs faster than 4.0 (i.e. for a given prompt, you get output tokens faster when running 4.5 than 4.0). This makes me think that Opus 4.5 is a significantly smaller model than 4.0.
Also of note is that Opus 3.0 is $15/$75 and all Sonnets are $3/$15.
I’m assuming Opus 4 targets Trainium 2 Ultra, necessary for both efficient serving and RL training. The buildout of this system was happening over 2025, so it wasn’t yet available in the times of Opus 4.0-4.1, which is why they were slow and expensive, and not properly RLVR-trained. By the time of Opus 4.5, Trainium 2 Ultra racks were probably sufficiently available to start serving it, after it was RLVRed either on Trainium 2 Ultra or on TPU v6e pods.