sealing decompressed and re-walked the whole ~1.3GB segment under the archive mutex to build the block index and blooms; every append (and so every live subscriber) went quiet for the duration — measured 44-52s per seal, matching a 52s delivery hole observed live. blocks now feed the footer builder at flush time, commitPrepared patches offset/frame size, and recovery pays its one walk at startup via rebuildIndex. the full walk remains only as a fallback when the index is out of lockstep. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>