getContextBreakdown used message position (anchorIndex >= pending.cutoffCount) as a proxy for usage freshness. After a mid-run compaction rebased the in-flight snapshot, an in-flight provider response whose request predated the compaction landed past the rebase cutoff carrying pre-compaction usage, so it out-ranked the rebased estimate and reported the pre-compaction token count (~2.6x the real one). That phantom overflow tripped the "freed too little context to make progress" guard and drove the frame-rescue path on a byte-identical tokensBefore.
Assistant context snapshots now carry a monotonic compaction epoch, bumped in rebaseAfterCompaction and stamped at message-record time. A post-cutoff anchor whose epoch predates the pending snapshot's epoch is no longer trusted over the rebased estimate.
Fixes#8887
roboomp
e6c0cf90a4