You'll noticeTier: how much it should matter to you
3Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
CompactionArea: what it touches
ImprovementsKind: in v2.1.281,
ImprovementsSection of the release
What
Compaction is when Claude Code shortens a long conversation by replacing older parts with a summary, so it still fits in what the model can take in. Reactive compaction is the version that runs after the model has already rejected a conversation as too long.
When its usual steps run out, or its final summarize attempt is itself too long, it may now summarize only the opening round of the conversation and keep everything else. If that attempt fails, or the reply has no <summary> block, the result is thrown away and it falls back to dropping that opening round.
Why
The start of a conversation can now be kept as a summary instead of being removed outright, so less is lost when a conversation grows too long.
