llamacpp has a reasoning-budget and reasoning-message setting that can both be a global or per header setting. Using it, you can stop it's reasoning token count and insert a message at the point you stopped it.

This allows both the client and server to customize it. I typically use a message that tells it to compact the conversation and use subagents. I find the reasoning gets bloated when it's failed to do whatever task it's doing and often times it either has too little context (subagents) or its context is bloated (compact).

This works fairly well to get it to extend workable life up to ~1M on a local model.