TL;DW:
Vast are scheduled to launch a Haven demo satellite this April on the Bandwagon-3 rideshare mission. The purpose of the demo satellite will be to test propulsion and avionics.
Haven-1 to launch in 2026. Vast's near-term goal is to have Haven-1 operational before NASA issues contracts for ISS replacements. Haven-1 will consist of a single 3.8 meter diameter module, designed to max out the payload volume of a Falcon 9 fairing. Haven-1 won't be permanently crewed from day 1, or have closed-loop life support from day 1. Will rely mostly on consumables.
Haven-2: Current design is to launch several 3.8-meter diameter modules on Falcon Heavys (with stretched fairing), and dock them to a 7-meter diameter core module launched on Starship. Each module would have its own power and propulsion, to allow for reconfiguration on orbit.
Long-term goals are to build a 100-meter "spinning stick" space station of 7-meter diameter modules which could simulate earth, martian, and lunar gravity.