DL-488
A shared space is a root channel with channels.shared = TRUE, visible to every account in the tenant through one predicate arm c.kind = 0 AND c.shared; names are unique per tenant among shared channels (channels_shared_name_key). channels_shared_root_only (shared implies no parent_agent_id and kind CHANNEL) replaces channels_group_xor_agent as the permanent rule that shared spaces never hang in a tree, so user trees never cross. Replaces only DL-397’s permanent-CHECK clause; DL-397’s other rulings stay Active.
Status: Active (proposed, pending Matt, 2026-10-11)