A write made during a full sync could be scanned in the replica but not in the (read-ahead) source scan, so the diff removed it, and echo tracking then consumed the server's echo. Keys written during a sync are now left out of the diff. Deterministic regression test with a read-ahead source. Also exclude -0 from the Extended JSON property test (JSON has no -0). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_017Qxbkp4tA7G5SCWjzWuxmE