Whenever I work on a challenging question I worry about this, because Opus will easily think for 200k tokens on the first prompt. I fear any follow up discussion is lobotomised!
Yeah totally feel you on this one! To avoid it or at least limit that I usually ask it to create external memories, clearing the context window and leaving just a trace to recall the memory created for that run. I hope it might help!
I try to avoid > 200k contexts, as the 1M context is where I first saw the massive decrease in reliability.
And my AGENTS is really short, and I said it was ignoring decisions in the prompt.