In the story, they are building an app nobody can listen in on. This is it — or something close: convene, a private group chat riding a mix-net carrier, its whole behaviour specified in plain language and compiled to the WebAssembly running on this page. Pick a username and a shown name, choose a password, and you are holding a seat. Open this page anywhere else, log in as someone new, and invite them — the relay between you holds sealed cells and learns nothing it carries.