Subagents do summarization - usually with the cheaper models like Haiku. Summarizing tool outputs doesn't work well because of the information loss: https://arxiv.org/pdf/2508.21433. Compression is different because we keep preserved pieces of context unchanged + we condition compression on the tool call intent, which makes it more precise.
I can control the model, prompt, and permissions for the subagents. Can you show how your compression differs from summarization by example? What do you mean by "we keep preserved pieces of context unchanged" ?