Project: portal users: portal and following [ '&', ('privacy_visibility', '=', 'portal'), ('message_partner_ids', 'child_of', [user.partner_id.commercial_partner_id.id]), ] Project/Task: portal users: (portal and following project) or (portal and following task) [ '|', '&', ('project_id.privacy_visibility', '=', 'portal'), ('project_id.message_partner_ids', 'child_of', [user.partner_id.commercial_partner_id.id]), '&', ('project_id.privacy_visibility', '=', 'portal'), ('message_partner_ids', 'child_of', [user.partner_id.commercial_partner_id.id]), ]