The Horizon plugin is meant to be extensible, both through the release of official plugins and through an open-source SDK which provides a template of two-way communication between the Horizon core app and external plugins.

You can check out the Horizon SDK yourself in order to develop software that interacts with the Horizon core. Official plugins are run internally with the Horizon SDK on Horizon's own infrastructure.

In future Horizon versions you will be able to deploy your own Horizon build on-premises, where you will be able to run plugins internally.

For unofficial custom plugins you can use the SDK as an API. Coming soon, Horizon will allow users to set webhooks for outgoing events, and the Horizon SDK will be used to enable incoming events.

It is recommended that users treat HTTP latency as a reasonable timeframe for actions being supported by the Horizon application (around 1 second). For applications requiring sub-second latency contact us.

We are also developing a Horizon sandboxing utility which will allow for a more isolated environment to run custom plugins off of Horizon core infrastructure.