[InsideOutSanta]

> But long-context is a trap, because performance still falls dramatically after 150k-200k context.

I'm not sure exactly what causes the difference, but this heavily depends on the model. In my experience with Opus 4.8, I can go well over 500k and still get extremely good results. A drastically different example was GLM-5.1, which worked great until about 100k and then turned insane almost immediately. They did fix that with 5.2, though.

[subscribed]

I'm an amateur so it influences my setup a lot, but Opus 4.8 above 250k context in my experience with planning and implementing its own plans gets much dumber than fresh Sonnet 5, to the point of forgetting / ignoring things in the last prompt, forgetting half of the convention for the (very small and simple) codebase, etc.

[gunalx]

5.1 going insane was probably also a inference quirk. Because it sometimes remained coherent the entire 200k context length.