How to Fix a Unity Mod DLL That Won't Load at Runtime with Assembly.Load

Players drop a compiled mod DLL into your mods folder, but nothing happens and you see no Mod found logs. The assembly never loads because IL2CPP AOT cannot run arbitrary new IL, and stripping removed the API surface mods compile against.

How to fix it

1. Use a backend that allows runtime IL

IL2CPP is ahead-of-time compiled and cannot execute new managed code from a DLL. Build the modded target with the Mono backend, or restrict mods to data and Lua. Verify with Application.platform and a startup log of the scripting backend.

2. Preserve your mod API surface

The managed stripper deletes types no game code references, so the mod's using targets vanish. Add a link.xml that preserves your modding namespace and any reflection-only types, and ship the matching API DLL for modders to compile against.

3. Load from a stable folder with full paths

Enumerate *.dll under Application.persistentDataPath/Mods and call Assembly.LoadFile(Path.GetFullPath(p)). Relative paths and LoadFrom resolve probing differently; full paths avoid a silent FileNotFound.

4. Surface load failures, do not swallow them

Wrap each load in try/catch and log ReflectionTypeLoadException.LoaderExceptions. The default catch hides the real missing-dependency, making every mod look like it simply did not load.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Unity error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.