Lightweight JavaScript library (similar in spirit to HTMX but with a smaller API doing more) that keeps a long-lived SSE connection open to the server and morphs server-rendered HTML patches into the DOM using an algorithm similar to idiomorph from Hotwire. Can receive Phlex components, raw HTML strings, JavaScript to execute, and reactive signal values for client variables — enabling a hypermedia model where the server fully drives the UI. Ismael Celis wrote the Ruby SDK for Datastar; when it pushes data over SSE it uses Brotli compression, achieving >80% ratios on HTML so replacing full pages is cheap. Used as the client layer of Cidurial.