[Bug] .NET 10 NativeApi.PushArg<T> throws "Unsupported type String" when passed null, breaking AddStateBagChangeHandler wildcard bagName

[unknown-urge]

Summary

CitizenFX.Base.NativeApi.PushArg<T>(T arg) throws System.Exception: Unsupported type String whenever it is called with T = string and arg == null, which makes it impossible to pass null for any nullable/optional string native argument from C# resource code.

The clearest manifestation is ADD_STATE_BAG_CHANGE_HANDLER's bagName parameter, documented (and functional from Lua/JS) as "pass no value / nil to match every bag for the given key" (see the wildcard listener pattern in the migration guide). In C#, Native.AddStateBagChangeHandler(keyName, null, funcRef) cannot be used to reach this behavior at all — it throws immediately.

In my testing this was not a contained, per-call failure: it crashed the entire client script host for the resource, with every other IScript in that resource then logging Script not found on subsequent events.

Issue type

Client, Server (the affected type, CitizenFX.Base.NativeApi, is shared by both CitizenFX.FiveM.Client and CitizenFX.FiveM.Server)

Repro rate

Always

Server build version

No response

OS

Windows

CPU

No response

GPU

No response

RAM

No response

Storage type

No response

Connection type

No response

ISP and bandwidth

No response

DxDiag

No response

Network graph

No response

Platform

Windows

OS version / distribution

Windows 11

CPU

No response

RAM

No response

Using txAdmin?

No response

Hosting provider

No response

Machine type

No response

/perf endpoint output

No response

DDoS protection

No response

ulimit -n value (Linux only)

No response

Docker Compose file (Docker only)

No response

Steps to Reproduce

1. Reference CitizenFX.FiveM.Client 0.0.3-alpha (NuGet, nuget.org) from a client resource script.
2. In an IScript.Initialize(), register a state bag change handler with a null bagName, mirroring the documented wildcard-listener pattern:

var funcRef = SharedAPI.GetCore().FuncRefManager.Register(
    (Action<string, string, object, int, bool>)OnStateBagChanged);
Native.AddStateBagChangeHandler("testKey", null!, unchecked((int)funcRef));

3. Start the resource.

Expected Behavior

The handler registers successfully and fires for any bag (not just one specific bag name) whenever testKey changes, matching the documented Lua/JS behavior for a nil/omitted bagName.

Actual Behavior

[patch-test] FAILURE: wildcard handler registration threw: System.Exception: Unsupported type String
   at CitizenFX.Base.NativeApi.PushArg[T](T arg)
   at CitizenFX.FiveM.Client.Native.AddStateBagChangeHandler(String keyName, String bagName, Int32 funcRef)
   at PatchTest.Client.PatchTestClientScript.Initialize()

This is not specific to AddStateBagChangeHandler — it is a bug in PushArg<T>'s own generic dispatch logic. Any native wrapper that calls PushArg<string>(null) for a nullable string parameter hits the same throw.

Evidence

System.Exception: Unsupported type String
   at CitizenFX.Base.NativeApi.PushArg[T](T arg)
   at CitizenFX.FiveM.Client.Native.AddStateBagChangeHandler(String keyName, String bagName, Int32 funcRef)

Additional Context

[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.

Additionally there's a new API for easier StateBag management: you can use API.AddStateBagChangeHandler, entity.State.AddChangeHandler or API.GlobalState.AddChangeHandler instead.
Currently there's a known issue that state bag change handlers registered directly via native call will be invoked on the wrong thread. This does not happen if you register handler via API, and will be properly addressed in the future FiveM patches.

[unknown-urge]

Since there is a new API, this issue can be closed.