- Add Store::for_each_addressed_id (default: every id; MemStore filters) so custody selection no longer clones every broadcast observation on each poll. - Factor fragment sizing into frag::plan and MAX_FRAGMENTS, used by both frag::fragment and the exchange, and by the reassembler's bounds. - Document `to` in the Observation::id hash input, matching the addressed-delivery plan. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>