Paradox Interactive pushed out Stellaris patch 4.5.4, nicknamed “Cygnus,” on 11 November 2026. The update is live on Steam, GOG, and the Microsoft Store. It’s a focused hotfix aimed mostly at multiplayer stability problems that showed up after the previous patch.
The team says the bulk of the fixes target out-of-sync (OOS) errors during hotjoin, the moment a player joins a game already in progress. These desyncs could come from almost anywhere: border colors, fleet modifiers, storm pathing, waystation links, cloak states on ships, and even arkships generating with an extra armor part. The patch note list runs long, covering dozens of individual OOS triggers tied to colonies, fleets, cosmic storms, federations, and AI behavior.
What else got fixed
Outside of the sync work, 4.5.4 also patches a handful of general bugs. Federation members joining a game were losing their custom ship designs, which is now fixed. Governor and general modifiers were disappearing permanently if a colony changed hands and came back, and colony modifiers from species traits or cosmic storms were stacking incorrectly every day until a recalculation reset them.
Market prices and trade statistics were also double-counting a month of trades every time a save loaded, which has been corrected. Paradox addressed a login issue where players were getting logged out of their Paradox account mid-load, along with crashes tied to scripted fleet arrival effects and empty name lists.
What this means if you run mods
Anyone running a heavily modded Stellaris campaign, especially in multiplayer, should treat this as a good moment to check compatibility. Mods that touch fleets, storms, colony modifiers, or custom ship designs are the most likely to interact with the systems this patch changed. Back up your save before updating, and if you host or join modded multiplayer games, make sure everyone at the table is on 4.5.4 before loading in, since mismatched versions are a common source of the exact desync errors this patch tries to squash.
Paradox has asked players to keep reporting out-of-sync issues if they persist, so the fixes here aren’t necessarily the end of that particular saga. If your mod list includes anything that overrides storm behavior or AI attitude scripts, keep an eye on patch notes for follow-up fixes.
Source: Steam · Image: Steam
