(I have both and haven't run into any limits yet, so I'm probably not a very heavy user.)
I'm quite impressed with the model. I have been using GLM-4.6 in Claude Code instead of Sonnet, and finding it fine for my use cases. (Simple scripting and web stuff.)
(Note: Z.ai's GLM doesn't seem to support web search (fails) or image recognition (hallucinates). To fix that I use Claude Code Router and hooked up those two features to Gemini (free) instead.)
I find that Sonnet produces much nicer code. I often find myself asking Sonnet to clean up GLM's code. More recently, I just got the Pro plan for Claude so I'm mostly just using Sonnet directly now. (Haven't had the rate limits yet but we'll see!)
So in my experience if you're not too fussy you can currently get "80% of Claude Code" for like $3/month, which is pretty nuts.
GLM also works well in Charm Crush, though it seems to be better optimized for Claude Code (I think they might have fine tuned it.)
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I have tested Kimi K2 at 1000 tok/s via OpenRouter, and it's bloody amazing, so I imagine this supercharged GLM will be great too. Alas, $50!