Have you tried writing that as a skill? Compaction is just a prompt with a convenient UI to keep you in the same tab. There's no reason you can't ask the model to do that yourself and start a new conversation. You can look up Claude's /compact definition, for reference.

However, in some harnesses the model is given access to the old chat log/"memories", so you'd need a way to provide that. You could compromise by running /compact and pasting the output from your own summarizer (that you ran first, obviously).

This is exactly how it should work. I imagine it as a tree view showing both full and summarized token counts at each level, so you can immediately see what’s taking up space and what you’d gain by compacting it.

The agent could pre-select what it thinks is worth keeping, but you’d still have full control to override it. Each chunk could have three states: drop it, keep a summarized version, or keep the full history.

That way you stay in control of both the context budget and the level of detail the agent operates with.