Martin Fowler documents an accidental coordination pattern that surfaced during a real agentic engineering experiment: multiple agents spontaneously began using a shared artifact — effectively a blackboard — as an implicit coordination mechanism, without that pattern being deliberately designed in. The blackboard functioned as shared working memory, letting agents read each other's partial outputs and orient their own work accordingly.
The significance for designers is that this coordination wasn't prescribed — it emerged from the structure of the task and the agents' shared access to a common artifact space. That emergence is a signal: when you give multiple agents access to overlapping context, coordination strategies will appear whether you planned for them or not. Designing for multi-agent systems means accounting for these uninstructed behaviors, not just the ones you explicitly wire up.
For UX practitioners, the implication is that the interfaces we build around multi-agent work need to surface shared state legibly — not just what each agent is doing, but what they're all reading and writing to. If a blackboard pattern can appear by accident, it can also disappear by accident, or produce conflicts designers never anticipated. Making that shared surface visible and editable is a first-order design problem, not an implementation detail.