Anita Kirkovska (Vellum) states that by June 2026 agent harnesses ought to be lightweight and highly extendable, and that Vellum is building toward that future. She links to Vellum's extensibility docs (vellum.ai/docs/extensibility), which outline plugin support and the composable surfaces plugins can provide for assistants.
On June 25, 2026, @anitakirkovska tweeted that agent harnesses should be lightweight and highly extendable, positioning that as the goal for Vellum.
It's June 2026, and your agent harness should be lightweight, and highly extendable. We're building towards that future here at vellum.
You can read more about our support for plugins here: vellum.ai/docs/extensibility
Link
Extensibility - Vellum Docs
All of the ways your Assistant can build on themselves. Overview of the surfaces a plugin can bundle and how they compose.
vellum.ai