4.3.4 Open Beta (part two) is now on stellaris_test (10th April 2026)
Patch Notes1 min read

4.3.4 Open Beta (part two) is now on stellaris_test (10th April 2026)

The second part of Stellaris's 4.3.4 'Cetus' open beta is live on stellaris_test, bringing disruptor reworks, fleet size fixes, and a stack of bugfixes.

Nathan Lees
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The 4.3.4 'Cetus' open beta part two is now live on the stellaris_test branch, following up on the fixes Paradox flagged yesterday. The full release is expected next Thursday, with a few more fixes still to come.

The headlining balance change is a rework to disruptor weapons, which now apply a regeneration effectiveness debuff on hit. Tier 3 disruptors cut shield regen by 50% and armor/hull regen by 30% for 10 days, which meaningfully shifts how sustained fleet engagements play out. There's also a significant bugfix to fleet creation effects that were spawning fleets five times their intended size, primarily hitting GDF reinforcements, revolts, and machine uprisings. The Doom of the Eater fleet has been bumped up to compensate.

Beyond that, Scourge Missiles were quietly dealing five times intended damage after a torpedo fix missed them, purges now correctly pause during active ground battles, and the AI has been updated to better manage alloy and food budgets post-Starbase cost changes. Credit where it's due: Paradox is also teasing a job assignment refactor on an internal experimental branch that could land in a 4.3.5 if testing goes cleanly. Full patch notes below.

Full Patch Notes

Hello everyone!

We've just updated the stellaris_test branch with the fixes we were talking about yesterday.

4.3.4 ‘Cetus’ Release Notes (ONGOING)​

Notes in italics were not in the 2026-04-02 Open Beta update.

Balance​

  • Added a cap of 10 years (in defines) for how long a fleet can go MIA. (Exceptions: Phased or Eaten fleets, and those exploring Astral Rifts.)
  • Disruptor weapons now also reduce Regeneration Effectiveness on hit for 10 days.
  • T1: -20% Shield, -10% Armor/Hull Regen.
  • T2: -35% Shield, -20% Armor/Hull Regen.
  • T3: -50% Shield, -30% Armor/Hull Regen.
  • Psionic: -35% Shield Regen, -20% Fire Rate, but remains on the anti-fire-rate channel so will stack with other disruptors.
  • Increased Exotic Gas production of Advanced Bio-Reactor to 0.1 from 0.05.
  • Increased Ministry of Production and Production Center Alloy and Consumer Goods bonus to 0.2 from 0.1.
  • Faculty of Archaeostudies:
    • Biologists on a Relic World now produce +0.25 Minor Artifacts (was +0.1)
    • Archaeo-Engineering AP now increases Biologist Minor Artifact Production by +0.15 (was +0.05)
    • Increased Minor Artifact storage cap to 2000 (was 1000) and the Archaeo-Engineering bonus to 3000 (was 2000)
    • Reduced Building Upkeep to 8 Energy from 10 Energy
    • Corrected tooltip that has been very wrong for a very long time
  • Astral Siphon:
    • Increased Astral Siphon thread production to +0.2, +0.35, and +0.50 (was +0.1, +0.2, +0.3).
    • Reduced Astral Siphon Physics bonus to +0.2, +0.35, and +0.50 (was +0.25/+0.5/+0.75)
    • Reduced additional upkeep to +1/+1.5/+2 CG or +2/+3/+4 E/M for Gestalts. (Was +1/+2/+4, +2/+4/+8, and +2.5/+5/+10)
    • Increased thread storage to +200, +400, +600 (was +100, +200, +300).
  • Reduced the fleet power of Voidworms to be more accurate to their capabilities. (Especially if you use Point Defense against them.)

    Bugfix​

    • Fixed Mutagenic Habitability being capped at a lower threshold than stated.
    • Fixed an issue in the create_random_fleet and create_fleet_from_naval_cap effects that didn't recognize that ships are much bigger than they used to be, so was typically creating fleets five times the size it was supposed to.
    • This will primarily impact the GDF reinforcement fleet, Revolts, Machine Uprisings, and Civil Wars, Habinte, and a Zevox ending.
    • The Doom of the Eater fleet has been increased to compensate for this change - plus a little extra on top.
  • Fixed the "Volcanic Forge" technology from "Planet Forgers" not appearing for certain origins
  • Adjusted the name of the "Conduit" ship class in the German translation
  • Purges like the Prethoryn, Sentinels, and others now really only occur while they are left alone on the planet. ALL purges now pause any time there is a ground battle for the planet going on. (This includes normal purges, though collateral damage may still kill pops.)
    • Updated Mechanocalibrator, Terraforming Mutants, Mutant Horrors, and Titanic Guardian events to clean up properly as well.
    • Corrected a logical error where if an empire was bad at purging, they’d be able to slow the decline of pops by setting them as Undesirable.
  • Updated Luminary tooltip to reflect their improved lifespan.
  • Scourge Missiles were missed in the initial pass that kept torpedoes and similar weapons from dealing 5x intended damage. Your behemoths are now slightly safer.
  • Oppressive Autocracies can now build medical centers.
    • Reminder: Only Elite stratum jobs generate amenities in Oppressive Autocracies and Medical Workers & Genomic Researchers are Specialists.
  • Fixed Necrophage+Planet Forgers pre-FTL worlds becoming volcanic at game start
  • Fixed Necrophage+Planet Forgers not getting Volcanic Forge as guaranteed research
  • Fixed Ministry of Acquisition tooltip showing blank consumer goods job name
  • Fixed star_eater_cap displaying as raw LOC key instead of ship name
  • Fixed Offworld Foundry job localization tooltip
  • Corrected Ion Cannon collateral damage. (Should be 100, was 20)
  • Storm Chasers should have an increased chance to draw Storm techs, not decreased.

    Also fixed the math error that was causing the cost of level 1 leaders to be too high again, and made sure it stuck this time. (Bug only affected the beta branch.)

    AI​

    • Updated AI alloy and food budgets to better handle new Starbase costs.
    • Adjusted AI food budget so bio-ship empires will rebuild their fleets if they recently lost a war.
    • Adjusted AI influence budgets so they'll be less prone to immediately allocate their entire influence stockpile to changing vassalization contract terms if they become an Overlord.

    Stability​

    • Fixes an OOS when a hotjoiner is accepted during a hotjoin, after the "start" button had become active in the hotjoin status window
    • Fixed an OOS when a player leaves and rejoins
    • Fixed an OOS related to Spy Networks.
    • Fixed an OOS at start when players don't have the same DLC as the host, and someone choses a random empire.

    We expect this patch to go live next Thursday with a few more fixes.

    We currently have an internal experimental branch relating to refactoring job assignment - I'm hoping we'll be able to have another "YOLO" branch update sometime next week. Those changes definitely won't go live in 4.3.4 - but if we don't see any problems during the Open Beta they might go into a 4.3.5. That refactor seems to clean up most of the issues we still have around promotion, demotion, job displacement, and the like.

    • Tags:Patch NotesStellaris
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    Written by

    Nathan Lees

    Gaming journalist and founder of XP Gained. Covering patch notes, breaking news, and updates across 160+ games.

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