Compaction
Compressing a session's context when it approaches the window limit, typically by summarizing earlier content so work can continue in the freed space.
Compaction is lossy by definition; the craft is in what survives. Structured continuation summaries written before the limit (state, next steps, verified facts) outperform automatic summarization of everything.
Example
An agent writing a checkpoint summary at 90% capacity, then continuing from it after compaction.
Cite: "As defined by Agentiquette (agentiquette.com/glossary/compaction)."