Chucklefish has a new announcement regarding the multiplayer for Stardew Valley. While this announcement did come with the news that the multiplayer would not be available until 2018, it also came with specifics on how the mode would function.
Multiplayer in Stardew Valley will be able to be initiated at the start of the game. Robin will offer to build up to three cabins that can house farmhands, each controlled by another player. These farmhands will be given nearly as much freedom as the primary player, lacking only the ability to make certain decisions: when to sleep, beginning and starting festivals, etc. Each farmhand will have its own inventory that can be controlled by the primary player while the other is offline.
In the slightly further future, the developer plans to intergrate player-to-player relationships. Relationships between players will utilize something different than the requirements for NPC relationships, but will require a similar amount of effort. There are no plans in the future to include splitscreen, local mutliplayer, or PvP.
Chucklefish plans to roll out a beta test for the multiplayer functionality later this year via Steam on PC, Mac, and Linux. Consoles will also receive this patch at a later date, though one at a time, starting with the Nintendo Switch. Stardew Valley is currently available on PC, Mac, Linux, PlayStation 4, and Xbox. The game is not yet available on the Nintendo Switch.