"Multi-platform" means the same thing runs on iOS and Android. Two binaries, two stores, one feature set. "Multi-surface" means the same cognitive context is available at the terminal, in Obsidian, in the browser, over voice — and the context survives the crossing. Confusing the two kills agent portability. The platform is where the code runs. The surface is where the thinking happens.
Most AI products ship as multi-platform apps that pretend to be multi-surface. You can open them in three places, but each instance is amnesiac. The preferred state you declared in the morning terminal session doesn't inform the evening voice call. The draft you started in the browser is gone by the time you're in the editor. Every surface is an island.
Totem Protocol operates at the surface layer. The primitive is the context that travels, not the app that renders. When the protocol works, the tool at hand is whichever one fits the moment — and the thread doesn't break when you switch.
What this lets stakeholders do: pick the surface that fits the task without negotiating with the platform tax. Keep one working memory across a day, a project, a lifetime of notes.
What's still open: what's the canonical handoff format between surfaces, and who runs the reference implementation?