Yeah it was very disappointing that so few details were provided. One of the reasons I think it's going to be an open source project or effort that is going to show, sooner or later, how effective these things actually are.

In their podcast interview, they mention that it's an Electron app that users download, and so they periodically create a new build. See section "Autonomous Merging Flow" here: https://www.latent.space/p/harness-eng