Bannerlord Software Extender and HarmonyX

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The ecosystem for modding Mount & Blade 2: Bannerlord is about to undergo two significant changes with the introduction of the Bannerlord Software Extender (BLSE) and a switch from Harmony to HarmonyX. We caught up with Aragas - the BUTR modding team lead - who has made extensive contributions to essential mods like ButterLib, Mod Configuration Menu and UIExtenderEx about what's new and how it will impact both players and mod authors. 

Bannerlord Software Extender

The first and most interesting change is the introduction of the Bannerlord Software Extender (BLSE) - for the Elder Scrolls and Fallout players out there, that acronym might be familiar. This new tool - an evolution of the popular BUTRLoader - will expand modding capabilities and add additional functionality to the game. It will also unlock modding for players of Bannerlord who are using the version from Xbox Game Pass for PC which was quietly released by TaleWorlds a short time ago. BLSE will be required to mod the Game Pass version but will be optional for the Steam, Epic Games and GOG releases. The Vortex extension for Bannerlord will also be updated in the near future to support BLSE, allow users to view and manage saved games and give more useful load order results during automatic sorting.

You can download Bannerlord Software Extender here. 

Switching from Harmony to HarmonyX

A new game version based on .NET Core has been introduced (Xbox Game Pass for PC) which offers better performance and cross-platform compatibility but no longer works well with the Harmony library which is currently a staple of the modding ecosystem. HarmonyX is a drop-in replacement that uses a different backend for patching the game. It also offers richer low-level access for patching and provides better patching behaviour for mod authors. It does have some minor behavioural differences but in testing the majority of existing mods worked without issue. The other advantage of switching to HarmonyX is that mod authors won't have to create different versions of their mod to support the different releases of the game, which is great news!

You can read the full, technical explanation by Aragas here. 

What does this mean for me?

Hooray! Players with the Xbox Game Pass version can now install all the mods players on other platforms have been enjoying. They just need to install BLSE and ensure they start the game from the BLSE executable rather than from the game executable or the Xbox store. For everyone else, you can install BLSE and start playing with the beta version of the core Bannerlord mods. The transition should be as painless as possible, with less than 10% of mods not working correctly on the new frameworks so far. 

If you currently use a large collection or have a particularly complex load order (50+ mods) you should take care when updating. It is recommended that you don't use BLSE or update to the beta versions of Harmony, UIExtenderEx, ButterLib and MCM for at least a week to allow time for any major issues to be patched out.  

For mod authors, all you need to do is check that your mod still works correctly with HarmonyX and the beta versions of the core mods (if it depends on them!). 


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  1. Pickysaurus
    • Community Manager
    • 680 kudos
    An update to this article has been posted here:
  2. RavenknightIndustries
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    Ahh, life is good. Thanks for all the hard work you put into this. 
  3. SpElLcHaSeR
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    • 2 kudos
    omg its happening
  4. MASK2499
    • member
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    god bless this is the start of something special 
  5. 2marcin2212
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    bro revolutionized whole modding scene of bannerlord 💀
    thank you dude, I love you
  6. fistingcthulu
    • member
    • 1 kudos
    Looking to get into modding Bannerlord, will BLSE be a beneficial tool for someone starting out knowing nothing outside of XML changes?
    1. Aragas
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      • 179 kudos
      You can create non XML mods (C#) without BLSE, but with BLSE we provide a more stable and predictable experience for both players and modders!
  7. Maelstrom89
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    • 23 kudos
    Currently organizing an MO2-based list that'll be on Wabbajack soon, and as said, things like MCM 5.6.0 need some time, so I can't really use any of this yet, but all the same this is very good news for this game.
  8. dzpliu
    • supporter
    • 1 kudos
    Thank you for your work Aragas! Especially when XGP version of the game is a pain to mod.
  9. KillaKhan69
    • supporter
    • 3 kudos
    Wonderful work. Here's hoping future mod works will be less headache inducing especially after each patches.
  10. YRZ
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    Will BLSE just allow a universal compatibility between game platforms, or will it server also like SKSE and make the game a lot more moddable? Or is it Modding capabilities expanded for only gamepass, while no difference for other game platforms.
    1. Aragas
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      • 179 kudos
      We help with making the mods universally compatible between game platforms and we extend the modding capabilities for all platforms!
      We do not enforce BLSE for Steam/GOG/Epic right now, but we expect mods that will require BLSE in the future!
      EDIT: BLSE will be a requirement on Steam/GOG/Epic too!