Last-resort compaction can put back dropped messages, behind a new flag

What

Compaction is how Claude Code shortens a long conversation so it still fits: it summarizes older parts. The reactive, last-resort compaction path gains new pieces, and the remote switch for one of them has changed:

• A put-back step splices extra messages back into the set being summarized. It is tracked by compactionApiAttemptsLeft and a putBack list.
• After a successful compaction that had to cut messages from the start of the conversation (head truncation), Claude Code records compact_rounds_dropped with the reason prompt_dropped, summary_dropped or prompt_and_summary_dropped.
• The compaction summary footer is restructured. The note pointing to the saved transcript is added only when a transcript path exists.
• The helper eMi() decides whether the putBack list is built. It now reads the server-side flag tengu_hazy_prism instead of tengu_mill_orange. When the flag is on, the list is oo.filter(Xoe). Otherwise it is empty. The fallback is false, so the put-back path stays off when no server value exists.
• A separate helper that read tengu_quiet_slate_wren now reads tengu_valiant_teapot, also with fallback false.

A flag is a remote switch Anthropic can turn on for some accounts. For tengu_hazy_prism, tengu_mill_orange, tengu_valiant_teapot and tengu_quiet_slate_wren, the flag server returned off for this site's account and for the anonymous baseline. None of those readings was taken under this release. Nothing has been read about tengu_reactive_compact_attempt, the gate listed for the new compaction helpers.

Why

When compaction has to throw part of the conversation away, this can bring some of it back, and it records when your prompt or the summary was lost. The put-back path now follows the server value of tengu_hazy_prism, not the old flag.