ATCHED
Stellaris
Stellaris
4.5|Sep 22, 2026
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Stellaris 4.5 "Cygnus" now available!

3/5 Moderate

The 4.5 'Cygnus' update introduces a massive Pop Group rework to improve late-game performance and unlocks the Cosmogenesis Ambition and two Origins for Nomadic Empires.

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Key Changes

  • 1Pop Group rework changes how Pops are stored to reduce late-game lag and UI clutter
  • 2Save compatibility is broken; version 4.4 saves will not work in version 4.5
  • 3Nomadic Empires gain access to Cosmogenesis Ambition, Knights of the Toxic God, and Storm Chasers
  • 4Native Apple Silicon support added for MacOS, improving performance on M-series chips
  • 5New Government policies introduced to weight Ship Autodesigner and Starbase weapon preferences
  • 6Federations can now enact Economic Laws for free Research Agreements and Commercial Pacts
  • 7Empire customization expanded with independent map border, fill, and ship color options
  • 8Over 350 bug fixes and stability improvements implemented
  • 9Nomad AI improved with better economic planning and system selection logic
  • 10Factions screen updated to show attractiveness drivers and improved suppression/embrace mechanics

All Changes

⚙️Gameplay Systems(7)

  • changePop Groups: Pop Groups are no longer split by Factions and Ethics; they now track percentages of Pops holding specific Ethics/Factions to reduce late-game clutter.
  • changePops: Pops now switch Ethics and Factions more readily than in previous versions.
  • newUI: Added new tooltips that break down the specific factors pulling Pops toward different Ethics and Factions.
  • newFactions: The Factions screen now displays attractiveness levels and the specific factors driving that attractiveness within the empire.
  • buffFactions: Suppressing and Embracing Factions now has a more visible and significant impact on their growth rates.
  • newFederations: Federations can now enact Economic Laws that grant members free Research Agreements and Commercial (or Wayline) Pacts.
  • changeFederations: Federation Economic Laws for free pacts are blocked for Federation types that already provide these benefits, such as Trade Leagues.

🛸Nomadic Empires(4)

  • changeNomadic Empires: Nomadic Empires can now access the Cosmogenesis Ambition (requires The Machine Age DLC).
  • changeNomadic Empires: Nomadic Empires can now use the Knights of the Toxic God Origin (requires Toxoids Species Pack).
  • changeNomadic Empires: Nomadic Empires can now use the Storm Chasers Origin (requires Cosmic Storms DLC).
  • buffNomadic Empires: Improved Nomad AI behavior including better Economic Plans, weights, and smarter system selection logic.

🚀Ship & Starbase Design(3)

  • newShip Autodesigner: New Government policies allow players to weight the weapon preferences used by the Ship Autodesigner.
  • newStarbases: Added Starbase Defense Preference Policies to control automated weapon and defense choices.
  • changeStarbases: Reworked Starbase defense modules to align with new preference policies.

💻Performance & Technical(3)

  • changeSave Games: The Pop Group rework breaks save compatibility; saves from version 4.4 and earlier will not load correctly in 4.5.
  • newMacOS: Added native Apple Silicon support via a universal binary, removing the requirement for Rosetta 2 on M-series Macs.
  • fixGeneral: Implemented various stability improvements and desync fixes.

🎨Customization(2)

  • newEmpire Customization: Players can now choose map border, map fill, and ship colors independently of primary and secondary empire colors.
  • fixEmpire Emblems: Corrected several Empire emblems that were previously rendered slightly off-center.

🐛Bug Fixes(1)

  • fixGeneral: Resolved over 350 bugs, making this the largest bugfix patch in the game's history.

Summary

The 4.5 "Cygnus" update is a major technical and quality-of-life release for Stellaris, featuring the largest bugfix collection in the game's history with over 350 fixes. The centerpiece is a fundamental rework of how Pops are stored and processed, shifting from individual Faction/Ethics splits to a percentage-based system within groups. This change significantly reduces late-game lag and UI clutter but necessitates a break in save compatibility with version 4.4.

Additionally, Nomadic Empires receive expanded content access, and players gain more granular control over their empires through new Ship Autodesigner policies and independent color customization for maps and ships.

← OlderStellaris Dev Diary #433 - 4.5 'Cygnus' Preliminary Release NotesSep 17, 2026

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