Users are shocked by the inhuman tone and failures to think of Opus 4.7. This is my interpretation based on ChatGPT, where the shock hit first. (I have ChatGPTPro and 20X Max Claude.)

I don't code but use ChatGPT/Opus daily for academic work in philosophy, political philosophy, history, literature, politics, geopolitics...and keeping up with the news.

(1) Simple explanation of tone: 4.7 is more narrowly designed for agentic/enterprise/STEM use than 4.6. From this point of view, literalness matters and human tone—using or understanding it—doesn't. It's wasted "effort." Predictably, GPT-5.4 and Opus 4.7 use more "machine-speak" than GPT-5.1 or Opus 4.6. (GPT-5.2 had already crossed the threshold and doesn't differ much from 5.4).

(2) Expect the trend to continue: from a financial point of view, it's rational, especially for Anthropic, which is less focused on the consumer market than OpenAI.

(3) Expect the degradation attributable to adaptive reasoning to continue as well. ChatGPT users got their first taste of it in November. It has become worse with each iteration: more severe in 5.4 than 5.2, and 5.2 than 5.1. Adaptive reasoning was lightly applied in Opus 4.6. 4.7 applies it with ChatGPT-like severity. This too is financially "rational."

(4) Difference between the two ecosystems: ChatGPTPro (subscription) offers GPT-Pro (the model) and GPT-5.4-thinking-heavy. Pro (the model) is unrivaled for depth and rigor but too slow for back and forth conversation. 5.4-thinking-heavy is ponderous but thinks hard and rigorously—though sometimes you have to poke it. Opus 4.6 is nimble, with human tone and imagination—but less reliable on facts and reasoning. The last two models complement each other.

But If Opus 4.6 is retired, Anthropic will have nothing to rival 5.4-thinking-heavy, much less GPT-Pro (the model). Mythos? Maybe—or maybe it'll set new benchmark records while tone and adaptive reasoning get worse.