Support for Realtime - Server Side Updates and Streams like LiveView and PhoenixSync

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Hi @krezicoder!
Great to hear you’re building with Hologram!

You’re not missing anything - currently, data from the server can only be sent in response to commands. Server-initiated updates aren’t supported yet, but there are two features on the roadmap that directly address your use cases:

  1. Server-Triggered Actions - Enable triggering actions from server code outside of commands, such as background jobs (e.g. Oban) or scheduled tasks.
  2. Local-First Support - Implement local-first architecture with offline-capable local database, auto-sync, and conflict resolution for resilient applications.

Initially I planned to provide a PubSub API, but after deep exploration and Time to Implement Pub/Sub in Hologram - Looking for Your Input!, I shifted toward a local-first auto-sync approach - along the lines that @garrison advocated in that thread. The key insight: using PubSub for data sync forces you to manually wire up message passing and maintain synchronization yourself. This leads to bugs and tangled imperative synchronization code. A local-first layer gives you declarative, automatic sync - data just appears in your components when it changes, no manual routing needed. You want top-down data flow from a central source of truth, not component-to-component messaging.

We’d still have Server-Triggered Actions for ephemeral events (notifications, typing indicators) where they make sense - playing a role similar to cast (fire-and-forget, no delivery guarantee).

The local-first space is enormous and I’ve been analyzing it for some time, hence the silence on this topic.

What you can do today

With some creativity, you can support your use cases now with a combination of these:

  • Polling command - a command that periodically checks for updates from the server using the delayed param
  • Phoenix Channel alongside Hologram - store channel events in a global JS object, then read from it via Hologram.JS.exec/1 in a polling action
  • Hologram.JS.exec/1 for general but basic JS interop

The polling is needed because proper JS interop (Time for Hologram <> JavaScript Interop - What Would You Like to See?) hasn’t been implemented yet.

Hope this helps!

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