One-Letter Typo To Blame For Aliens: Colonial Marines’ Bad AI

One-Letter Typo To Blame For Aliens: Colonial Marines’ Bad AI
Image: Gearbox / SEGA

Thanks to the work of modder James Dickinson, Gearbox’s notoriously awful Aliens: Colonial Marines can now be played as something other than a form of punishment. You can imagine Dickinson’s uncovered some nutty bugs in his time poring over the game, but none hold a candle to a single-letter typo that lobotomised the Xeno AI.

Dickinson wrote about the typo in late 2017 when he first discovered it, describing it as “the biggest BUG in the game”:

Inside your games config file (My Document\My Games\Aliens Colonial Marines\PecanGame\Config\PecanEngine.ini) is the following line of code:

ClassRemapping=PecanGame.PecanSeqAct_AttachXenoToTether -> PecanGame.PecanSeqAct_AttachPawnToTeather

Yep, “teather” instead of “tether”. According to Dickinson, the logic attached to this is rather important, allowing the AI to “[control] tactical position adjustment, patrolling and target zoning”.

By simply removing the “a”, the AI is transformed — it will happily flank you and “disperse [Xenos] so they aren’t so grouped”. Which, as you can imagine, makes a big difference.

There's A Reason To Play Aliens: Colonial Marines Again

I know it's a tad impossible, but hear me out. Let's go back to the launch of Aliens: Colonial Marines (ACM). Remember the fury, the outrage, the disappointment. Most of all, remember what was missing.

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If you ever wanted proof as to how big a shitshow ACM was, it doesn’t get much better than this.

A typo found in the INI file after all this time appears to be one of the major causes for terrible AI mechanics in the game. Thankfully typo’s are easy to fix! [ModDB, via ResetEra]


  • Is there an example that shows how much this one bug fix changes things? I had so many issues with the game that I struggle to believe that this fixes the game, even at a fundamental level.

  • Jesus, this has to be up there with glitches on discs such as the Baldurs gate one where opening a single door would crash the entire game, or when Warhammer Online shipped a batch of discs with a corrupted EXE file to actually launch the game with XD

    • Those games got patched though.

      This bug seemingly was not; it actually sounds like this “mod” is really a patch from an unofficial source.

      • Oh I just mean in the sense of a gamebreaking bug launching with a game… but yeah they were patched soon after. Though the Warhammer one should’ve stayed a bug because BOY that game sucked…

        • Those dark days when everyone was releasing an MMO and every one before release was called a “WoW Killer”.

          • I didn’t mind Warhammer Online. It showed the way with Public Quests, so added something new to the genre. It just pushed you into PvP with little way to advance without it, which I didn’t want.

            Was the only MMO where I enjoyed battlegrounds though, mostly because I had a simple but effective way to take early control of one of the early maps.

          • I agree WHO had some features which were a definite plus for the MMO genre. The game simply wasn’t complete enough which is the same sin many defunct MMOs made. It’s silly to make an MMO that competes with vanilla WoW when they need to compete with the given time period WoW.

    • Half Life 2 had bad discs too. 5 discs to install from memory and disc 3 threw an error. I returned to store, got another copy same thing. At that point I went online and found the “Update steam online, don’t use the one on the disc and it went fine.

  • and NASA lost a Mars lander because one lot of contractors used metric and another lot used imperial, sometimes human error happens. Not sure a simple typo is conclusive proof of “how big a shitshow” something is.

    • It shows how inept the studio was that something so simple made it into the retail copies even after several patches. Youd think there would be processes in place to pick up something so simple. Clearly not.

  • So there was some half decent AI, but nobody noticed it was misbehaving in a big way? Seriously lacking in the QA department there.
    (Well duh, everyone says)

      • …yes it is??? They have play testers to do quality control generally through a games construction? That’s exactly how quality control/quality assurance is meant to work.

        • QA tells the devs whats wrong.

          Its up to the devs to fix it.

          QA could have told the devs this was an issue but they dev team instead decided to leave it as it. QA does not fix the game, They just tell them whats wrong.

          • I’m well aware of that. It tells them what’s wrong so the devs can go fix it, that’s why they have playtesters. Noone expects the playtesters to go fix it now do they…

          • Thats the point im making. QA could have made the devs aware of this. But the devs either through publisher pressure or of their own volition could have decided not to fix this.

          • Or, in the millions of lines of code, failed to identify the single letter causing the problem… Thats a pretty small needle in a pretty big haystack.

          • It wasnt in millions of lines of code.

            It was in an INI file containing around a page of settings.

          • @djbear

            huh, so it was. Missed that. Doesn’t really change it though. One of the big problems with bug testing is finding the damn thing. Its easy to say “the thing is doing stuff”, but not so easy to find out WHY the thing was doing stuff. Tucked away in an ini file could have made it even harder to find. Its effectively just text with any issues like this being ignored (which seems to have caused all the issues) rather than prompting an error message.

            When a bug is happening at a certain point of scripting you can just follow it along, but when that doesn’t solve it, you might need to go through EVERYTHING, whether its a 2 line ini file or a million line core code. That’s not fun when the bug doesn’t cause an error.

            Not disagreeing with you by the way (to borrow your line 🙂 ) just pointing out another reason why it might not have been fixed. It simply wasn’t found. It only made the game flawed, not broken – it still booted up and played, albeit badly. So they might have just wrote it off as a ghost in the machine.

          • Just think about it though. If you were the dev and you knew the AI was broken like this. Would you not go through all the AI settings in things like the INI config file to check that everything is okay?

          • All good man. Ive made the same mistake before. I always feel shit afterwards. Its why i always take a few moments to read over stuff rather than jumping straight into commenting 🙂

          • It depends on the company / team. In many it’s like that, but in others the QA/E (e.g. myself) is capable of managing code and can debug or even fix/suggest errors – depending on the level of freedom they have. I’d never again work in a company where the QA was forbidden from code changes.
            “Playtesters” would come well after component QA, and if the organisation has even the basic of respect for their quality engineering then something like this would not have QA approval and would not be released.
            But then, going by the comments, perhaps Gearbox is not one of those…

      • Could you elaborate on your comment? I’d like to understand your perspective.

        As I see it, the “intent” was to have the enemy move a certain way based on player location, environment and such, for example flanking and charging. Clearly this was not working “as intended” and it should have been recognised, especially as a core component of the product.

  • PC Gamer has a write up about it with gif/video of it in action. it doesnt automatically make the AI great, as its still pretty shit, but it does so an improvement

  • Well shit. I own this on PS3, so I’m probs not gonna get any benefit from this, but it’d be nice to be able to play it and enjoy it.

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