Of course I echo the universal: Opus 5 sucks. But what also sucks is still using 4.8. Are you all seeing this? It's like the older models got dumber just before Fable and Opus 5 were coming out? I've heard the theory that it's because 4.8 is getting put on older hardware? And I imagine that just ratchets down reasoning time then possibly? Sometimes I'm just trying to sus out if I'm truly seeing things these days or g…
I'm not an expert by any means whatsoever but deploying models is not a straightforward task. There's a lot of levers to pull and I bet when models get "downgraded" to older hardware they do so WITHOUT the same stringent quality control of the output as they do when they release it. I don't think it's something deliberately malicious like planned obsolescence but it's more like startup culture of "just make it fit in…
Your explanation is probably the most likely and largest contributor. Anthropic states that Opsu 5 is a "pinned snapshot". They claim the weights and model configuration are not silently updated, BUT the surrounding serving infrastructure can change, including the request router, safety classifiers, and sampling logic. Anthropic has stated that if behaviour unexpectedly changes on a stable model ID, an infrastructure update is the most likely cause.
Further, "High" isn't a fixed amount of compute. Anthropic describes effort as a "behavioural signal" and not a token budget, with the model deciding how much thinking to do. So their "High" might be "Low" now, and we would never know.
Finally, I strongly suspect some quantisation or KV-cache compression is happening. Anthropic doesn't clearly delineate whether this would fall under the pinned weights and configuration, or the infrastructure, which almost certainly guarantees it's the latter. Forgetting earlier information, poor retrieval of details, contradicting previous conclusions, hallucination, degraded instruction-following, and losing the thread during complicated tasks are all symptoms of quantisation and compression.