First Early Access release
The official initial Early Access feature list describes single-player support. The material checked does not establish a co-op mode available in the first release.
The later co-op target
The September 12 preview used an after-1.0 description for co-op. In the later developer-team interview published by Zizaran, the team twice described co-op as a target by 1.0.
Use that later target when describing the plan, while keeping it a development target rather than a guaranteed schedule. It would be misleading to state categorically that co-op must wait until after 1.0.
What is not confirmed?
This material does not confirm a specific co-op release date, player limit, dedicated-server support, cross-platform play or working invite procedure. There are no tested multiplayer setup steps to follow here.
See release and platform information for the planned first Early Access release. The game systems overview explains the announced single-player systems without assuming multiplayer versions of them.