Stellaris 4.3 Cetus open beta updates mixed ethics, population groups, save warnings

“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,” Paradox Development Studio wrote in the PDX_ladydzra Steam post that carries the 4.3 “Cetus” Open Beta Patch Notes 2026-02-26. The post, published on 27 Feb 2026, labels the patch notes with the 2026-02-26 date while warning players a follow-up open beta will alter pop groups and offer a rollback branch.

The announcement opens with “Hello Stellaris Community!” and the studio’s stated intent: “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.” The Steam Store mirror repeated the intro as “We have another open beta update for you this week. This update features a whole host of bug fixes, performance improvements and balance changes.” The Store text also explicitly invites feedback with “You can leave your feedback on the latest version of the open beta here:”.

Balance adjustments in the 26 Feb notes focus on population systems and late-game economy. Under “More Mutagenic Spa balance:” the patch notes say “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,” and “Mutagenic Spa Councilors now increase the number of spa attendant jobs, this effect is amplified if they are a substance abuser.” The notes also add that “Mutagenic Spas can now be placed in research or unity district specializations.”

Starbase and industry changes were explicit: “Starbase building Offworld Trading Company now grants +4 trade per Trade Hub module (was +2 Trade)” and “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).” Policy and tech changes include “The Computation Core Focus policies now grant +2.5% job efficiency per 100 roboticists or identity designers instead of +0.5% per 100 civilians,” and Steam mirrors list “Reduced Capital Productivity techs to +5% efficiency per tier from +10% per tier.”

Crisis and encounter tuning also feature. The Store text adds “When multiple End Game Crises are active in galaxy settings, End Game Crises are now allowed to spawn 25 years after another crisis has spawned instead of being blocked while there is an active crisis.” It also lists “Mercenary and Shroudwalker Enclaves now require 100 Naval Capacity in the fleet” and “The Crisis Beacon espionage operation now looks for larger fleets than before.”

The patch includes several bug fixes: “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,” and “Added abort triggers for the Prethoryn, Unbidden and Contingency event chain so they get properly cleaned up after their related crisis is defeated.” The PDX capture also notes “Endbringers can no longer be declared a crisis if they are already the current crisis, which was restarting their war. [...]”

Mirrors and trackers echoed the same material: Patchtracker.gg mirrored the post and added the aside “Thanks to Scirch for this abomination of a screenshot.” Inara.cz republished the post and listed related entries including “Stellaris Dev Diary #411 - Our Next 4.3 Experiment — Steam — 19 Feb 2026” and earlier Cetus open beta updates dated 12 Feb, 06 Feb (with “[Checksum 2e59]”), and 30 Jan 2026.

The immediate user-impact detail is the promised save-breaking pop-group change that will arrive the week after the 26 Feb patch and the availability of a rollback branch for saves from the current build; follow the PDX_ladydzra Steam news post for the exact timing and rollback branch details when the follow-up open beta lands.