[Bug] [Partially solved] Client crashes when having more than 1 C# project/dll with API code in a single resource.

[TomGrobbe]

Summary

I'm testing out the new C# API while working on vMenu for Enhanced, and I'm extremely confused by one DLL that I'm trying to load causing the following client crash to occur:

---------------------------
C# Unhandled Exception
---------------------------
System.ArgumentException: An item with the same key has already been added. Key: 2221991672336

   at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)

   at CitizenFX.Host.Host.StartScript(IntPtr scriptPtr, IntPtr resourceNamePtr, IntPtr pathPtr)
---------------------------
OK   
---------------------------

The source code for the DLL in question can be found here
Resource files can be found here

The project is called "IamAproblem", I've tried many different names, it started out with NoClip, as that's what I was working on. But something with this project is causing a crash once it's being loaded, and I don't understand why. The class it has is empty, just like the other projects in my code. There are no references to that class (so it's never being initialized). It has no references to other projects or to any CFX dependencies. It SHOULD not be loaded, yet it somehow is and causes a crash.

If you remove the dll from the server resource folder and restart the resource, everything works fine. Add the DLL back, and it's broken again. (It's registered in the fxmanifest under client_scripts).
fivem-for-gtav-enhanced.log-2026-07-28_22-01-27.log

Server info:

{
    "vars": {
        "gamename": "gta5enhanced",
        "sv_projectName": "[FiveM Basic Server] Pizza Party",
        "sv_projectDesc": "Recipe for the base resources required to run a minimal FiveM server.",
        "txAdmin-version": "9.0.0-beta-646aba9a",
        "tags": "enhanced, default, deployer",
        "sv_appearAllowlisted": "false",
        "locale": "root-AQ",
        "sv_voiceChat": "false",
        "onesync_enabled": "true",
        "sv_maxClients": "8"
    },
    "resources": [
        "basic-gamemode",
        "chat",
        "fivem-map-hipster",
        "mapmanager",
        "sessionmanager",
        "spawnmanager",
        "txadmin",
        "vMenu.Enhanced"
    ],
    "requestSteamTicket": "on",
    "server": "FXServer-early-access b98 win32"
}

Issue type

Client

Repro rate

Always

Server build version

FXServer-early-access b98 win32

OS

Windows 11 Pro 25H2

CPU

Intel(R) Core(TM) i7-14700K (3.40 GHz)

GPU

NVIDIA GeForce RTX 3080

RAM

32 GB DDR5

Storage type

SSD NVMe

Connection type

Ethernet

ISP and bandwidth

1000/1000

DxDiag

Network graph

No response

Platform

Windows

OS version / distribution

Windows 11 Pro 25H2

CPU

Intel(R) Core(TM) i7-14700K (3.40 GHz)

RAM

32 GB DDR5

Using txAdmin?

Yes

Hosting provider

Self-hosted

Machine type

None

/perf endpoint output

Unauthorized.

DDoS protection

No

ulimit -n value (Linux only)

No response

Docker Compose file (Docker only)

No response

Steps to Reproduce

1. Download the source and compile the project, copy fxmanifest from the assets folder and create a new server and put the resource in. (Or download the files from the release, see initial issue description for link).
2. Join server with resource started, or join server first then start resource.
3. Game crashes.

Expected Behavior

Script isn't referenced, so it shouldn't load and I should be able to simply join the server without crashing my game.

Actual Behavior

Join server, game crashes.

Evidence

---------------------------
C# Unhandled Exception
---------------------------
System.ArgumentException: An item with the same key has already been added. Key: 2221991672336

   at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)

   at CitizenFX.Host.Host.StartScript(IntPtr scriptPtr, IntPtr resourceNamePtr, IntPtr pathPtr)
---------------------------
OK   
---------------------------

Additional Context

Contact me if you need anything else.

[TomGrobbe]

I have a feeling that some of the testing I was doing was clouded by some cache issues. Clearing server/client caches and fully rebuilding assets seems to change the result sometimes.

What I can at least consistently reproduce is the following:

Have a resource with 2 C# projects, both containing at least some Cfx API calls (whether they have an entrypoint or not is irrelevant, I had for example 1 project with an entrypoint and IScript, the other without, and the one without just had 1 class with 1 random method with an API call)

It's like the script is being duplicated as soon as you have 2 projects (dll's) with API code in your resource, which is causing a crash.

I'd like to point out that without this fixed, making any cleanly setup resource is fairly difficult (pretty much impossible) because I can only have 1 (client) DLL/project per resource.

[TomGrobbe]

This seems fixed now with the latest version and I also figured out that I was doing stuff wrong (probably), I moved all other DLL's to the "files" section of the fxmanifest, instead of having them all as client scripts. And that seems to have solved it.

I'm not sure if this had something to do with the latest Cfx API release, or if moving all projects except one to "files" instead of client_scripts in the fxmanifest solved it. Or if that is even intended behavior or a bug, but at least I can continue working now.

Leaving this thread open just in case it's still considered a bug that you can't have multiple dll's in client_scripts in a single resource.

[europium-cfx]

Hey! This issue has been fixed in the latest patch b123 and CitizenFX.FiveM NuGets 0.0.4-alpha. Please try again and let us know if the issue persists.

Loading multiple DLLs in client_script or server_script should work properly now.

[TomGrobbe]

Confirmed working!