Stellaris 4.5.4 Cygnus Hotfix Patch Notes - All Changes

Paradox released Stellaris patch 4.5.4 on November 11, 2026. It's a small hotfix, and most of it goes after multiplayer stability problems that crept in with the previous version. It's rolling out on Steam, GOG and the MS Store.

If your multiplayer sessions have been falling out of sync since the last update, or your federation partners keep losing their ship designs, this is the patch you've been waiting for. We will go over every change in Stellaris 4.5.4, from the handful of gameplay fixes to the long list of desync and hotjoin repairs.

Stellaris 4.5.4 Highlights

• Multiplayer stability: the bulk of the patch is dozens of out-of-sync fixes, most of them for players hotjoining a game already in progress.
• Ship designs: joining a federation no longer wipes your custom ship designs.
• Modifiers: governor and general modifiers, plus colony modifiers from species traits and cosmic storms, behave correctly again.
• Trade data: market prices and trade statistics no longer re-count a month of trades every time you load a save.
• Paradox account: you should stop getting logged out of your account while the game loads.

4.5.4 Bug Fixes

Five gameplay fixes sit under the Bugfix heading, and a couple of them explain some odd economy numbers you may have seen since 4.5.3.

• Federation ship designs: empires that join a federation no longer lose the custom ship designs they built.
• Governor and general modifiers: when a colony switched controller and later came back, its governor and general modifiers stayed missing. They now return with it.
• Runaway colony modifiers: colony modifiers granted by species traits and by cosmic storms were growing every day until the next recalculation. That daily creep is gone.
• Market and trade statistics: loading a save no longer makes market prices and trade stats count a full month of trades a second time.
• Account logouts: the game no longer signs you out of your Paradox account during loading.

4.5.4 Multiplayer Stability Fixes

The Stability section is where the real work went, and nearly every line is an OOS (out-of-sync) fix. Many are specifically hotjoin fixes, meaning the desync only showed up for a player joining a game that was already running. We've grouped them by what they touch.

Hotjoin Desyncs

• A joining player could end up with different random border colors from everyone else.
• Travel shortcuts could desync because the joiner had out-of-date system status.
• Astral rift owners were only recalculated on the joining machine.
• Waystation links could differ after a join, most often following an expulsion, and throw the modifiers out of sync.
• Ships added to a fleet kept their old cloak state, which broke ship modifiers for the joiner.
• A joining player could receive an arkship with an extra armor part.
• A ship aura that wasn't cleared on the joiner, and crisis empires picking different enemies, could each cause a desync.
• Cosmic storms changing course only on the host, storm lists sorted differently on the joiner, storm sector blocking after a reroute, and border ranges when a storm covers a relay are all fixed.
• Several fleet orders and queued fleet actions lost their state or effect after a save or join.
• Nomad waystation orders could be refused on the joining side after a join.
• Colony, Arkship, fleet (federation unity and navy size) and ship bonus modifiers could all drift after a join, and modifiers could be recalculated on different days.
• A finished focus reward could complete a second time on one machine, the spy network check could flag a false OOS, and a country could stay flagged as human only on the joiner.

General Desyncs

• Country intel was calculated before other updates finished.
• Devastation could target a pop that had already left its colony.
• Players using different languages could desync when a stored name used grammar, and names stored by event effects could mismatch.
• A delayed event could be dropped on only one machine.
• Computer-controlled empires could differ between machines, and their attitude updates could fall out of sync.
• Two starbases in the same system updating the same list at once, and the starbase design fallback running on a worker thread, both caused desyncs.
• Tempest relic storms could trigger an OOS and a crash; their names now match on every machine. Modded games whose scripts wipe out a storm field are covered too.
• Wilderness empire biomass counts, galactic market price changes, and enclave and mercenary trade offers (the last one also a crash) are all back in sync.

Lobby, Login and Crashes

• The lobby list now refreshes if the online connection only comes through once you already have the screen open, and it tells you when it's waiting for that connection.
• You can no longer join a game before the online connection is ready, and the game offers a fresh login after the connection drops.
• A crash when a fleet ran a scripted effect on arrival, and a crash from empty name lists, are both fixed. Random name lookups are faster as a bonus.

And that covers all of the changes in Stellaris 4.5.4. Paradox asks players to report any out-of-sync issues that survive the patch. You can read the official patch notes on the Steam news page. If you missed the previous update, our Stellaris 4.5.3 patch notes cover the district specialization and Habitability changes, and the 4.5.3 experimental branch notes show where that patch started. For a look at what's coming next, see the dev diary on Great Mosaic, Path of the Self and Ideological Paragons.