Valheim1CompatBridges

BepInEx preloader patcher for Valheim 1.0 (Unity 6). It adds the old method overloads, fields and interface defaults back into assembly_valheim.dll at load time, so mods compiled against pre-1.0 builds stop crashing with MissingMethodException, MissingFieldException: ZRoutedRpc.Everybody, TypeLoadException: VTable setup failed or Harmony Undefined target method. No mod DLL is redistributed.

Tested with (client + dedicated server, BepInEx 5.4.2350):

Install

Put the patchers/Valheim1CompatBridges folder into BepInEx/patchers/ on the client and on the dedicated server (r2modman / Thunderstore Mod Manager do this automatically). Look for [Valheim1CompatBridges] Gotowe: N mostkow in BepInEx/LogOutput.log.

What it bridges

• Inventory.Changed() → Changed(false, false) (original renamed to ChangedEx, game calls rerouted so Harmony postfixes on Changed still fire)
• ZRoutedRpc.Everybody const → static field
• InventoryGrid.Element wrapper type (m_go, m_pos, mirrored fields), GetElement/GetHoveredElement overloads returning it, empty List<Element> m_elements_compat (deliberately not named m_elements: two same-named fields are legal in IL but make AccessTools.Field(type, "m_elements") throw AmbiguousMatchException, breaking mods that inject ___m_elements by reflection, such as AzuExtendedPlayerInventory and AzuAutoStore)
• InventoryGrid.Awake() (called from OnEnable), Minimap.OnMapRightClick() stub
• Hoverable.GetHoverOffset() default implementation
• old overloads of: Character.Message, MessageHud.ShowMessage, EffectList.Create, SEMan.AddStatusEffect (×2), ItemData.GetTooltip, Inventory.IsTeleportable, Humanoid.IsTeleportable, Inventory.AddItem (12 params), Terminal.ConsoleCommand ctor (12 params), Terminal.ConsoleEventArgs ctor, YesNoPopup ctor, Heightmap.Poke(bool), TerrainComp.Save(), Piece.SetCreator(long), VisEquipment.Set*Item(string, …) (prefab name → hash)

Using Marketplace as well?

Marketplace has two breakages the preloader cannot reach, because they live in the mod's own IL: its Hud.UpdatePieceList transpiler hardcodes local slot 12 for a Piece that Valheim 1.0 moved to 13 (InvalidProgramException, quest markers missing from the build menu), and it reads the old InventoryGrid.m_elements field from IL. The mod is closed-source, so there is no upstream fix to wait for. Run this once per machine, against your own copy of the DLL:

pwsh -File tools/fix-kg-marketplace.ps1 -Dll "<game>/BepInEx/plugins/KGvalheim-Marketplace/kg.Marketplace.dll" -Apply

It reads the real slot numbers out of your assembly_valheim.dll instead of trusting a hardcoded one, is idempotent, and refuses to guess if the layout it expects is gone. Keep the original DLL, and re-run it after every Marketplace update. The script lives in the repo, not in this package.

Source, and why this is a new project rather than pull requests: https://github.com/PawelSzymanski89/Valheim1CompatBridges

1.1.0

• m_elements shadow field renamed to m_elements_compat. Two fields of the same name made AccessTools.Field(type, "m_elements") throw AmbiguousMatchException, which broke AzuExtendedPlayerInventory and AzuAutoStore (both inject ___m_elements by reflection).
• Added tools/fix-kg-marketplace.ps1: retargets Marketplace's IL reference to the renamed field, and fixes its Hud.UpdatePieceList transpiler, which hardcoded local slot 12 for the Piece that Valheim 1.0 moved to slot 13 (InvalidProgramException, missing quest markers in the build menu).
• Verified alongside 21 plugins on client and dedicated server.

1.0.0

• First release: 29 bridges/injections; Weedheim, WeedheimShip and Marketplace And Server NPCs 9.8.1 load on Valheim 1.0.