Fwiw Sonnet 4.5 is very far ahead of where sonnet was a year ago

From my experience, Kimi K2, GLM 4.7 (not flash, full), Mistral Large 3, and DeepSeek are all about Sonnet 4 level. I prefer GLM of the bunch.

If you were happy with Claude at its Sonnet 3.7 & 4 levels 6 months ago, you'll be fine with them as a substitute.

But they're nowhere near Opus 4.5