The crossplay answer
Slay the Spire 2 does not feature full cross-platform play. The co-op mode is built for Steam friends, not for mixing players across console and PC.
What co-op needs
Co-op is Steam-based. Everyone in a lobby needs the Steam version and a place on your friends list. There is no console cross-play in early access.
Platforms
STS2 is a Steam title. The exact OS support (Windows, macOS, Linux) is listed on the Steam store page and can change during early access.
Before you buy, open the store page and read the system row. That is the source of truth, not a guide.
Steam Deck
Because STS2 is on Steam, it runs on Steam Deck. Check the Deck compatibility badge on the store page for the current verified status — badges update as patches ship.
At a glance
| Feature | Status |
|---|---|
| Full cross-platform play | No |
| Co-op | Steam friends only |
| Public matchmaking | No |
| Storefront | Steam (early access) |
| Steam Deck | Runs on Steam; check the compatibility badge |
| OS support | Listed on the Steam store page; can change in early access |
Bottom line
No crossplay. Steam friends only. Confirm OS and Deck support on the store page, since early access specs still move.
Know who can join
Because there is no crossplay, only Steam friends on supported OS can join your lobby, and early access specs shift. Confirm your group is on the same platform before planning a co-op run, or the lobby will not show for them.