Sensei is a plugin for firewalls complementing them with state of the art next generation features. If you are running a L4 firewall (all open source firewalls fall into this category) and looking for features like Application Control, Network Analytics and TLS Inspection, Sensei is the product you're looking for.
Sensei empowers your firewall with the following next generation features
Cloud Application Control (Web 2.0 Controls)
Advanced Network Analytics
All-ports full TLS Inspection (for every TCP port, not just HTTPS)
Cloud Threat Intelligence
Encypted Threats Prevention
Web Filtering & Security
Active Directory Integration
Freemium Edition is the free-of-charge Sensei edition. Freemium is forever free for OPNsense users.
Currently Freemium Edition is available and ready to download & deploy.
Premium Subscription is the paid Sensei Subscription which provides features for more advanced business use cases. Premium Edition is currently in the makings and will be available shortly.
Premium Edition features will be available in July 2019.
For a complete feature comparison see "Sensei Editions"