Once you have the plan you don't need to keep the 2hrs of research in the context (which is most of it) you can drop that plan into a file and start fresh for implementation.
If I feel like the model and I explored a lot of options I won't want to keep context as it might be confusing.
I think the more you use it the better judge you are of whether you should purge, compress, or just keep the context before executing the plan.
I use handoff skill to ask model to write a prompt for itself.
I've found Opus 5 far better as a subagent with very limited context window use, which could suggest that it might not have good long context performance unlike its predecessors. (I was one of many tearing my hair out trying to work with Opus 5 for the past week.)
Yes, pretty much - if there’s a lot of noise and jumping around and wrong conclusions and corrections, compress and only leave the correct stuff (maybe make some plan file briefly mention what NOT to look at/do). But if it’s all fairly straightforward then can just proceed with the execution.
Most of the time the planning stage ends up short of 200k tokens anyways, it mostly takes hours just cause I’m slow and need to explore the various options - still cheaper than building the wholly wrong thing and having to redo everything.
Compressing the context can also drop important information so it might be better to only do that when you need to / use the plan mechanism/files / do it after completing some large stage of the plan and so on - so a judgement call.