A mashup session manager maintains state of the mashup session to ensure presentation consistency/uniformity across the execution environments. The mashup session manager also tracks the participating execution environments associated with a mashup session (e.g., usernames, device identifiers, network addresses, etc.), and transmits data for presentation consistency to the participating execution environments. In some cases, a view of the mashup session at a participating execution environment may not be current (“stale mashup session view”). The mashup session manager can detect if a view at a participating execution environment is of a past mashup session state, and provide data for the stale mashup session view to become current. In addition, the mashup session manager can propagate design modifications to the participants of the mashup session.