Stellaris 4.3 "Cetus" Open Beta Updated (2026-02-26)

Hello Stellaris Community!

We're back updating the "Cetus" Open Beta again, with more balance changes based on your feedback as well as more bug fixes and performance improvements.

Please note: Next week's Open Beta update will contain a save breaking change to pop groups. There will be a rollback branch available for those who want to continue your saves from this version.

Improvement​

• Renamed Mercantile and Unyielding traditions to Commerce and Fortification to match the naming structure of all other traditions.

Balance​

• More Mutagenic Spa balance:

  • Mutagenic Spas now only grant Substance Abuser to the governor of a planet with the baths on.

  • Spa Attendants for Worker Coop buff the Union Stewards.

  • Non-corporate Spa Attendants now produce 500 Amenities (was 100). Corporate Spa Attendants now provide 2 trade.

  • Mutagenic Spa Councilors now increase the number of spa attendant jobs, this effect is amplified if they are a substance abuser.

  • Mutagenic Spas can now be placed in research or unity district specializations

  • Increased the bonuses from Food Processing, Mineral Purification, and Energy Grid buildings.

• Experimental Sentencing changes:

  • Experimentation Chambers now provide a static number of experiment engineer jobs, and a scaling number of test subject jobs (depending on building tier). The number of test subject jobs is increased by 50% on Penal Colonies.

  • Rebalanced the amount of research experiment engineers produce per crime on the planet. The bug in which the modifiers considered the uncapped crime on the colony has also been fixed.

  • Consumer goods upkeep of experiment engineers now also increases with crime.

  • Orderlies no longer reduce housing requirements on the planet.

  • Orderlies now increase the job efficiency of experiment engineers and test subjects not their output.

• Halved the effects on workers and slaves of the Ruthless Developer trait.

• Unifier trait effects no longer scale with leader level.

• Reduced happiness from Social Welfare.

• Reduced unity from civilians under Social Welfare.

• Biomorphosis changes:

  • Switched Optimized Neurology (Purity flex 1) and Heightened Attributes (Purity flex 2).

  • Switched Biochemical Composure/Regenerative Cloning (Cloning flex 2) and Artifical Population (Cloning flex 3).

  • Removed Organic Job Efficiency bonuses from Somatic Subversiveness (Mutation flex 2) and Artificial Population.

  • Optimized Neurology now gives -1 Leader Maximum Negative Traits instead of +1 Effective Leader Level

  • Somatic Subversiveness now grants an additional +1 Effective Leader Level.

  • Artificial Population now provides -10% Empire Size from Vat Grown pops

  • -10% Empire Size from Pops from Heightened Attributes moved to Imperfection Remediation.

• Starbase building Offworld Trading Company now grants +4 trade per Trade Hub module (was +2 Trade).

• Starbase building Hyperlane Registrar now grants +2 Trade per Trade Hub module (was a non-scaling +2 Trade) and adds the Subspace Amplifier aura to the Starbase (-40% Hyperlane and Jump Drive cooldown/change time).

• Adopting partial virtuality by undergoing Synthetic ascension as an organic, lithoid or infernal species no longer grants -90% housing.

• The Computation Core Focus policies now grant +2.5% job efficiency per 100 roboticists or identity designers instead of +0.5% per 100 civilians.

• Adjusted scaling of event spawned pirate fleets to be more reasonable for 4.3 numbers.

Bugfix​

• Planet Automation should work again. A design pass is in progress to improve the scripts.

• Fixed founder species has happiness check being reversed applying wrong amenities buffs on planetary populations

• Fixed the flavor text of a number of council position displaying the default name instead of the renamed title if the player had renamed them.

• Fixed Subterranean origin not giving extra housing on mining districts.

• Fixed nobles from cyber imperials not giving stability.

• Wenkwort planet modifiers are now correctly removed if the planet stops being a gaia world.

• Fixed a number of technologies having incorrect amounts for the housing modifiers they provide.

• Updated the Gestalt version of Chosen of the Eater to match the changes made to the non-gestalt version.

• Fixed mutation and cloning ascension not being able to remove advanced traits.

• Fixed modifiers from the Prospectorium Optimizer trait.

• Fixes an issue with ship size map icons.

• Corrected erroneous tooltip for the Domination tradition finisher.

• Corporate Vampires and Entropy Drinkers can now be swapped seamlessly when transitioning between corporate and oligarchic .governments

• Fixed several issues with secondary district names for Spiritualist empires and Ring World districts.

• Added abort triggers for the Prethoryn, Unbidden and Contingency event chain so they get properly cleaned up after their related crisis is defeated.

• Endbringers can no longer be declared a crisis if they are already the current crisis, which was restarting their war.

• Fixed incorrect founder species have happiness calculation resulting in inverted behavior that caused for example hive minds getting happiness bonuses.

• Fixed sector governor missing propagation of non triggered trait modifiers to all planets in the sector and not only the capital.

• Adjusted various conditions in modifier tooltip generation to not show unintentional data, ex “planet:”

• Fixed ship/fleet special modifiers being applied properly to the simulation and not only show up in tooltip ex docked ship upkeep reduction.

• Reduced stack usage in combat targeting code that could cause a CTD/undefined behaviour when larger numbers of ships are involved in combat.

Performance​

• Reduced number of memory allocations

• Optimized string allocations

• More string optimizations

• Reduced repeated localization lookups when calculating planet modifiers

• Moved modifier name calculations to tooltip generation where this was done in the game simulation.

• Micro optimized localization system even more, reducing amount of allocations, recursions and length calculations.

For the entire set of 4.3 Open Beta patch notes, please visit the paradox forums.

You can leave your feedback on the latest version of the open beta here: https://pdxint.at/4rN5fU1 and if you experience a bug or other issue, please make a bug report!

Thank you all for your interest in the 4.3 "Cetus" Open Beta, and thank you for playing Stellaris!