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Stellaris
Stellaris
4.3|Feb 26, 2026
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Stellaris Dev Diary #411 - Our Next 4.3 Experiment

4/5 Significant

Major overhaul to Pop Ethics allowing mixed ethics within single pop groups, alongside significant balance reworks for Mutagenic Spas and the Biomorphosis ascension path.

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Key Changes

  • 1Pop Groups now support mixed ethics and factions via a percentage-based system
  • 2Mutagenic Spas reworked with massive amenity buffs (100 to 500) and new job scaling
  • 3Biomorphosis ascension path reorganized with several perk swaps and bonus changes
  • 4Hyperlane Registrar buffed with a new -40% cooldown aura and scaling trade bonuses
  • 5Virtuality housing bonus (-90%) removed for organic/lithoid/infernal species
  • 6Combat targeting code optimized to prevent crashes in large-scale fleet battles
  • 7Social Welfare living standard happiness and unity production reduced
  • 8Offworld Trading Company trade bonus doubled from +2 to +4 per module
  • 9Planet Automation fixed and currently undergoing a script improvement pass
  • 10Mercantile and Unyielding traditions renamed to Commerce and Fortification

All Changes

👥Pop Systems(3)

  • changePop Groups: Introduced Mixed Ethics within Pop Groups, allowing a single group to have multiple ethics and factions simultaneously via percentage values.
  • buffEthics Drift: Improved ethics and faction drift logic to occur more reliably and frequently.
  • newUI: Added a detailed breakdown of ethic attractions accessible by holding the Alt key in the planet Management tab.

🏢Buildings & Districts(12)

  • nerfMutagenic Spas: Mutagenic Spas now only grant the Substance Abuser trait to the governor of the planet where they are located.
  • buffSpa Attendants: Spa Attendants for Worker Coops now provide a buff to Union Stewards.
  • buffSpa Attendants: Non-corporate Spa Attendant amenity production increased from 100 to 500.
  • newSpa Attendants: Corporate Spa Attendants now provide 2 Trade Value.
  • buffMutagenic Spa Councilors: Mutagenic Spa Councilors now increase the number of spa attendant jobs, with the effect amplified if they are a substance abuser.
  • changeMutagenic Spas: Mutagenic Spas can now be placed in Research or Unity district specializations.
  • buffResource Buildings: Increased the resource bonuses provided by Food Processing, Mineral Purification, and Energy Grid buildings.
  • changeExperimentation Chambers: Experimentation Chambers now provide a static number of experiment engineer jobs and a scaling number of test subject jobs based on building tier.
  • buffExperimentation Chambers: Test subject jobs from Experimentation Chambers are increased by 50% on Penal Colonies.
  • nerfExperiment Engineers: Consumer goods upkeep for experiment engineers now increases with planetary crime.
  • nerfOrderlies: Orderlies no longer reduce housing requirements on the planet.
  • changeOrderlies: Orderlies now increase the job efficiency of experiment engineers and test subjects instead of their raw output.

📜Traditions & Ascension(10)

  • changeMercantile Tradition: Renamed Mercantile tradition to Commerce.
  • changeUnyielding Tradition: Renamed Unyielding tradition to Fortification.
  • changeBiomorphosis: Swapped the positions of Optimized Neurology and Heightened Attributes in the Biomorphosis tree.
  • changeBiomorphosis: Swapped the positions of Biochemical Composure/Regenerative Cloning and Artificial Population in the Biomorphosis tree.
  • nerfBiomorphosis: Removed Organic Job Efficiency bonuses from Somatic Subversiveness and Artificial Population.
  • changeOptimized Neurology: Optimized Neurology now grants -1 Leader Maximum Negative Traits instead of +1 Effective Leader Level.
  • buffSomatic Subversiveness: Somatic Subversiveness now grants an additional +1 Effective Leader Level.
  • newArtificial Population: Artificial Population now provides -10% Empire Size from Vat Grown pops.
  • changeBiomorphosis: The -10% Empire Size from Pops bonus was moved from Heightened Attributes to Imperfection Remediation.
  • nerfVirtuality: Synthetic ascension for organic, lithoid, or infernal species no longer grants -90% housing when adopting partial virtuality.

👤Leaders & Traits(2)

  • nerfRuthless Developer: Halved the effectiveness of the Ruthless Developer trait on workers and slaves.
  • nerfUnifier Trait: Unifier trait effects no longer scale with leader level.

🛰️Starbases(3)

  • buffOffworld Trading Company: Offworld Trading Company trade bonus increased from +2 to +4 per Trade Hub module.
  • buffHyperlane Registrar: Hyperlane Registrar now grants +2 Trade per Trade Hub module (previously a flat +2) and adds the Subspace Amplifier aura.
  • newHyperlane Registrar: Subspace Amplifier aura added to Hyperlane Registrar, providing -40% Hyperlane and Jump Drive cooldown/charge time.

⚖️Gameplay & Balance(3)

  • nerfSocial Welfare: Reduced happiness and unity production from civilians under the Social Welfare living standard.
  • buffComputation Core Focus: Computation Core Focus policies now grant +2.5% job efficiency per 100 roboticists/identity designers instead of +0.5% per 100 civilians.
  • changePirates: Adjusted the scaling of event-spawned pirate fleets to be more reasonable for current balance numbers.

🐞Bug Fixes(16)

  • fixPlanet Automation: Fixed Planet Automation functionality and began a design pass to improve scripts.
  • fixPlanetary Populations: Fixed inverted founder species happiness check that applied incorrect amenity buffs.
  • fixSubterranean Origin: Fixed Subterranean origin not providing extra housing on mining districts.
  • fixCyber Imperials: Fixed nobles from cyber imperials failing to provide stability.
  • fixWenkwort: Wenkwort planet modifiers are now correctly removed if the planet is no longer a Gaia world.
  • fixTechnologies: Fixed several technologies providing incorrect housing modifier amounts.
  • fixChosen of the Eater: Updated Gestalt version of Chosen of the Eater to match non-gestalt changes.
  • fixAscension: Fixed Mutation and Cloning ascensions being unable to remove advanced traits.
  • fixProspectorium Optimizer: Fixed Prospectorium Optimizer trait modifiers.
  • fixDomination Tradition: Corrected Domination tradition finisher tooltip.
  • fixCivics: Corporate Vampires and Entropy Drinkers can now swap seamlessly when changing government types.
  • fixCrisis Events: Added abort triggers for Prethoryn, Unbidden, and Contingency event chains for proper cleanup after defeat.
  • fixEndbringers: Prevented Endbringers from being declared a crisis if they are already the active crisis.
  • fixSector Governors: Fixed sector governors failing to propagate non-triggered trait modifiers to all planets in a sector.
  • fixShip Upkeep: Fixed ship upkeep reduction modifiers not being properly applied to the simulation.
  • fixCombat Simulation: Reduced stack usage in combat targeting code to prevent crashes (CTD) in large fleet battles.

⚡Performance(5)

  • buffEngine: Reduced the total number of memory allocations.
  • buffEngine: Optimized string allocations and localization lookups.
  • buffPlanet Modifiers: Reduced repeated localization lookups during planet modifier calculations.
  • buffSimulation: Moved modifier name calculations from the game simulation to tooltip generation.
  • buffLocalization System: Micro-optimized the localization system to reduce allocations, recursions, and length calculations.

🛠️Modding(4)

  • removeModding Triggers: Removed pop_has_ethic and pop_group_has_ethic triggers.
  • changeModding Triggers: Updated has_ethic to return true if any pop within a group follows the specified ethic.
  • newModding Triggers: Added has_ethos trigger to check if a country or pop group contains all ethics of a target ethos.
  • newModding Triggers: Added pop_ethic_percentage trigger to check the percentage of pops following an ethic within a group.

Summary

Pop Ethics & Performance Rework

The headline change in the 4.3 'Cetus' Open Beta is a fundamental shift in how ethics are handled. Instead of splitting pops into different groups based on their ethics, a single Pop Group can now contain multiple ethics and factions simultaneously, tracked via percentage values. This is intended to reduce late-game lag by significantly lowering the total number of pop groups while making ethics drift more reliable.

Balance & Ascension Overhaul

This update features a massive balance pass on several systems. Mutagenic Spas and Experimentation Chambers have been redesigned with new job scaling and requirements. The Biomorphosis ascension path has seen its perks reorganized, with several bonuses swapped or replaced to better align with leader and empire-size mechanics. Additionally, Starbase modules like the Offworld Trading Company and Hyperlane Registrar have received substantial buffs to their trade output and utility.

← OlderStellaris 4.3 "Cetus" Open Beta Updated (2026-02-19)Feb 19, 2026Newer →Stellaris 4.3 "Cetus" Open Beta Updated (2026-02-26)Feb 27, 2026

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