The summary ledger is regenerated every turn. At the head of history it
invalidated the cached retained turns on every request once trimming
started. Insert it immediately before the current turn's HumanMessage so
system, tools and retained history stay byte-identical; excerpts of dropped
turns stay at the head since they only change when the cut moves.
Reserve a fixed ledger ceiling (SUMMARY_RESERVE_TOKENS) rather than its
current size, so a shrinking ledger cannot pull the cut back and change the
retained prefix; fall back to the actual size for tight budgets.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
ryan
1e638e1e3b