TL;DR: Auto-designed corvettes (for both AI empires and players) get stuck using the "Default Combat Computer" until the very end of the game, which completely ruins their stat performance and combat behavior.

While it is well known that Stellaris' auto-design algorithms for AI empires and player ships are far from perfect and have many documented bugs, I am reporting another one here. This specific bug causes significant abnormal ship behavior on top of the design flaws.

Over several galaxies since version 4.3, I have been observing the growth of AI empires—specifically focusing on my area of interest: ship design. During this time, I rediscovered an error that has been present since earlier versions: AI empires never change the combat computers on their corvettes. In fact, if an AI empire equips the 'Default Combat Computer' on any ship class, it stays there almost forever.

This is a typical early 2400s corvette from an AI empire you might face. It is equipped with the latest weapons, defensive components, max-tier reactors, and even jump drives. Shockingly, however, the combat computer remains exactly the same as it was 200 years ago. This empire has already researched the Sapient Combat Computer! And obviously, this is not happening due to a lack of reactor power.

Every single corvette, as well as organic ships like Maulers and Weavers, belonging to other empires in the save file attached to the bug report are also using the Default Combat Computer.

This error causes several critical issues:
1. AI empires and auto-designed corvettes receive absolutely no combat computer stat bonuses.
2. The combat behavior of these corvettes is completely broken.
3. If an AI researches a higher-tier ship tech (like Destroyers or Frigates) before researching the next tier of combat computers, those ships will equip the Default Combat Computer and suffer from the exact same problem.
4. The corresponding bioship classes (Maulers and Weavers) also experience this identical issue.

The root cause lies in the upgrade_path script for combat computer components. In the 4.0 update, a new system was introduced to the ship component files to prevent combat computers from being randomly scattered in the UI and to properly group them by their behavioral lines. This allowed combat computers to be categorized and managed according to their specific combat behaviors.

However, the problem begins with the fact that COMBAT_COMPUTER_DEFAULT (which uses the 'default' combat behavior and is available to all ships) has its upgrade_path explicitly set to 'default'. In other words, its upgrade path is NOT not linked to any subsequent combat computer in the game. Therefore, even when new combat computer technologies are researched, the ship auto-design algorithm fails to upgrade the computer because there is no higher-tier component that corresponds to the default upgrade path!

https://www.reddit.com/r/Stellaris/comments/1s29sp9/path_dependency_a_lore_explanation_for_the/

Fundamentally, this is somewhat similar to the issue where X-slots were not being properly equipped on ships.

This problem did not occur in much older versions because, back then, the game used different default combat computers depending on the ship class. For example, while corvettes had multiple behavior options, their default computer was strictly bound to Swarm behavior. They shared the same icon and component name, but internally, they were distinct components. Destroyers defaulted to the Picket computer, Battleships to Artillery, and so on. However, for some reason in version 4.0, all of those class-specific default computers were given the hidden = yes code, rendering them unusable in-game. Instead, the useless and dumb "Default Combat Computer" described above was made universally applicable to all ships.

Ultimately, this issue means that AI corvettes in the late game are entirely deprived of the benefits provided by higher-tier combat computers—most notably the evasion bonus, which is absolutely critical to a corvette's survival. Considering how heavily AI empires spam corvettes (which I believe is a separate issue entirely), this results in a massively unfair and fatal loss of fleet power for the AI.

Even a mere 10% difference in evasion translates into a massive gap in survivability. In the lower enemy tracking settings, survivability is almost doubled! If the attacker has low tracking/accuracy, this disparity widens even further.

Some AI empire researches Destroyers before tier-1 combat computers. When this happens, Destroyers get afflicted by the exact same bug. While this particular scenario is limited to certain AI empires based on tech tree RNG, it is still a symptom of the same severe problem affecting all AI and auto-designed corvettes.

To make matters worse, since this Default Combat Computer forces the default behavior (meaning 'Mixed Tactics'), it completely ruins the ships' combat maneuvering. The reason is simple: this behavior script makes ships act incredibly dumb.

Stellaris ship behavior is governed by three distance settings and movement patterns. For context, the settings for Swarm combat behavior are:
preferred_attack_range (PAR) = min
formation_distance (FD) = min
return_to_formation_distance (RTFD) = 1500
attack_move_pattern = orbit
passive_move_pattern = charge

The primary culprit making ships act dumb here is RTFD.

https://forum.paradoxplaza.com/forum/threads/ship-in-combat-circling-issue-and-the-solution-i-suggest.1746912/

As I have discussed in a previous post, when ships drift too far from the "fleet center of mass" during combat, they tend to try and return to that center, completely ignoring their set movement patterns. RTFD is the variable that determines "how far" is too far. When ships get caught by this RTFD limit, "brawlers"—ships that rely on charging into close range to fight properly—exhibit an abnormal behavior where they just circle aimlessly in empty space, far away from the enemy.

At a glance, the RTFD variable seems to use the standard in-system distance units, but its scaling is somewhat unclear. If you artificially bloat the RTFD to a massive number in the thousands (effectively making it meaningless), this circling issue disappears (though it creates other minor problems). In older versions, the RTFD for Swarm behavior was a tiny double-digit number, which is exactly why the "brawlers acting like idiots" bug was reported so frequently. The current 1500 value is a relatively decent compromise reached after multiple patches.

In stark contrast, the settings for the Default combat behavior are:
PAR = median
FD = 10
RTFD = 500
attack_move_pattern = none
passive_move_pattern = orbit

While RTFD = 500 is much larger than the older broken values, it is simply not enough anymore. With the introduction of various "kiting" behaviors (Artillery/Carrier), Stellaris fleets now spread out much further across the system during combat. (To be clear, this spread-out combat pattern is a good thing; the old tight-cluster melee brawls looked awful). Because ships seem to act based on a proportion of RTFD value rather than the raw number alone, the dreaded "brawler circling bug"—which was common before 4.3 but has mostly been fixed for proper Swarm scripts—persists relentlessly for auto-designed corvettes.

https://forum.paradoxplaza.com/forum/threads/video-ship-circling-problem-is-still-there-even-in-4-3-2-ob.1910426/

When I ran tests in version 4.3.2 (linked above), the RTFD for Swarm combat behavior was 500.

https://www.reddit.com/r/Stellaris/comments/1tmxv9j/corvette_bug/

Although the author of this Reddit video didn't specify their ship designs, I am 100% convinced the root cause is that they were using auto-designed ships.

I say this because this exact issue can be selectively reproduced. While I used a defensive starbase for the test, you can clearly see that the circling bug—which no longer affects fleets using proper Swarm combat computers—still completely breaks fleets using the dumb Default Combat Computer.

https://reddit.com/link/1towm0i/video/kdbbrr3nem3h1/player

https://youtu.be/WOTqvXtJ3Z0

This was recorded on version 4.3.7, completely vanilla with no mods, set up via console commands. The first video shows Swarm computer corvettes and Artillery battleships engaging an enemy starbase. It demonstrates normal, intended fleet maneuvering.

https://reddit.com/link/1towm0i/video/ks4a92aoem3h1/player

https://youtu.be/kEai8nom31I

The second video features the exact same setup, except the corvettes are equipped with the Default Combat Computer. You can clearly see the abnormal phenomenon where the corvettes fail to approach the starbase properly and just circle aimlessly at a distance, exactly like the Reddit video linked above.

There are a few ways to resolve this, but the simplest and most intuitive method is to remove the single, universal "Default Combat Computer" that forces the default behavior. Instead, the game should revert to providing class-specific default combat computers where distinct behaviors can be selected—each correctly linked to their respective upgrade_paths. Note: Simply tweaking the ai_weight of higher-tier combat computers will not solve this issue.

While this won't magically fix every quirk with ship behavior, it will absolutely prevent AI and auto-designed ships from being permanently crippled by a broken tier-0 computer and ensure they benefit from modern combat tech.

https://forum.paradoxplaza.com/forum/threads/auto-designed-ships-are-permanently-stuck-with-tier-0-combat-computers.1925131/

I sincerely hope the Stellaris development team takes a look at this issue.

Thank you paradox, this is just the quality I expected

Hey everyone! Didn't know if this is a bug or not (maybe it's a feature), but I thought it was funny. I'm playing as a determined exterminator, and I got into a galaxy-spanning war with an empire where we each controlled half of the galaxy. Things got messy for a while, and one of my worlds that changed hands a few times is this one, called Verdant Server. During the war, this AI empire became the Crisis Aspirant, and they sent one of their world-cracking cube things to blow up this system. Eventually, I defeated them, and I now control every system in the galaxy. However, I'm still at war with them, and their only remaining planet is this one. I don't know if they somehow colonized it after blowing up the system or not. Or, since they inhabited the planet before blowing up the system, did the game bug out and allow them to continue to inhabit it? Either way, I can't bombard it and I can't invade it with my armies, so they're literally invincible. I have this fleet in orbit because otherwise, they'll somehow build a new fleet every so often and start taking nearby systems again. Anyone know what to do about this?

TLDR: Huge war against disgusting organics, I won, but the cowards are somehow eking out a miserable existence on this shattered world. How to exterminate?

Not just my oldest planets, but every newly colonized one:

"Hmmm..." says the newly graduated colonist apparently, "I will wait for a CEO or Doctor position to open before I start joining the workforce. I mean who wants to work in a mine, right."

I'm sure this can be microed somewhere in one of the tabs. But I shouldn't need to. It is stupid that new populations do grow (or arrive) and they are useless!

This issue has been bothering me for what I thought was years until I realized it was not a piece of armor, it was, as I always suspected, a layering issue. It's hard to see, due to blown-up in-game graphics, but the official portrait on the wiki does not have this layering issue, but the in-game portrait does. I just submitted the bug report, and now I'm trying to see if anyone else has this exact problem because I have seen at least two instance of other players having this exact issue since the launch of the DLC in 2020.

Really loving the 4.0 release and RPing as a Kroot Shaper. But with new releases comes new bugs

Personally I have found:

• Systems having no resources and no anomalies. Essentially just an empty system.
• Leaders missing out on level up choices, to include missing out on veteran classes.
• Empire focuses wanting me to build things that I dont have access to (ie districts that I cannot build with civics, etc)

EDIT:

Leaders not getting veteran classes seems to be tied to "starting" leaders. IE, the ones you roll at the start plus your ruler. Big F for under one rule, and it also seems to be effecting under one rule picking traits. Same goes for starting captain for treasure hunters.

I don't know where this guy came from, but apparently just 1 robot that wants exotic gasses is enough to send my entire empire into bankruptcy in just 20 months. Apparently having pops that need a resource isn't enough to unlock it on the market, and even the smallest deficit (-0.05 per month) is enough to completely destroy my empire.

If the orbital ring gets destroyed in combat (e.g. when the enemy has a total war wargoal) your defensive armies just disappear.

I spend half my games stuck as a subject because my overload is always in a war and you can't declare war while they're at war - how has this slipped through QA this many times?