Changing a record's owner has always wiped its manual shares. Winter '27 makes that behavior optional.
Where
Setup, under Sharing Settings: a new option named Keep Manual Shares When Transferring Records.
How
Enable the setting and manual shares survive ownership transfers org-wide. The setting is off by default to preserve existing behavior, and when enabled it applies to all records rather than per record. The change resolves a long-standing IdeaExchange request.
Why
Losing manual shares on owner change caused silent access loss for collaborators, often discovered only when someone could no longer see a record they had been working on. Territory reassignments and rep turnover no longer require rebuilding shares by hand, though note the setting is all-or-nothing rather than granular per record.