What should context compression keep? I looked at how six agents handle it[D]

I use Claude Code, Codex CLI, OpenCode, Cline, Cursor, and Amp enough to notice a pattern in how they handle long context. They are all converging on layered progressive compression, but they disagree on what to protect. Most protect recent user messages as a first-class asset. That makes sense. The user said it, which is the source of truth. Most also protect tool outputs that carry state. What surprised me was how differently they treat old assistant messages. Artifacts keeps recent tool calls verbatim bu