World/Udon Bugs & Feature Requests

Ever since I went ahead to update my world with the latest update in mind (SDK 3.9.1-beta.1], anyone trying to join it will receive an "Unusual Client Behavior" and be kicked out of the world immediately. I tried to delete any changes done in the world in the hope to pinpoint the problem but the problem still occurred and even after downgrading to SDK 3.9.0 it still gives the error. If it helps to solve the issue, I noticed that messing with my PlayerObject pool (despite the fact I have not touched it once for the update) and removing then adding back some object prevented the error from showing up. Alas when I decided to arrange it after I noticed some script were broken with the newer PlayerObject setup in the world that fixed the error, the error showed up again, even when I used the backup scene I saved that worked before, that one ALSO DIDN'T WORK. This is the world currently being affected by this issue : https://vrchat.com/home/world/wrld_37abea33-f34c-4706-8e6b-2f69e414fc5d/info I have tried everything to see if the problem came from my world but the problem feels way too random for it to be the case.

Defining a method parameter of a user-defined enum type with a default value causes the UdonSharp compiler to throw during binding. The same method compiles successfully when the default value is removed. This issue does not reproduce with Unity/SDK-defined enums (e.g., UnityEngine.HumanBodyBones , VRC_Pickup.PickupHand). Reproduction using UdonSharp; public class EnumTest : UdonSharpBehaviour { // Compile error public void TestMethod(TestEnum testEnum = TestEnum.ValueB) { } } public enum TestEnum { ValueA, ValueB, ValueC } Actual Behavior Compile fails with Assets/Main/Misc/Enum/EnumTest.cs(6,0): System.ArgumentException: Type provided must be an Enum. Parameter name: enumType at System.Enum.ToObject (System.Type enumType, System.Int32 value) at System.Enum.ToObject (System.Type enumType, System.Object value) at UdonSharp.Compiler.Symbols.ParameterSymbol..ctor (...) at UdonSharp.Compiler.Symbols.UdonSharpBehaviourTypeSymbol.CreateSymbol (...) ... (Full message attached below) The exception is thrown inside ParameterSymbol when UdonSharp tries to evaluate a parameter’s default value using Enum.ToObject(enumType, value) during compilation. For user-defined enums, this call receives an argument that is not recognized as a valid enum type for some reason, which causes System.ArgumentException: Type provided must be an Enum . Workarounds Avoid using default parameter values for enums and provide an overload as a pseudo-default instead public void TestMethod(TestEnum testEnum) { } public void TestMethod() => TestMethod(TestEnum.ValueA);

I tried this both with udon graph and udon sharp. Both times, when calling the Respawn function, the udon script throws an error and halts. It says that the reference is not set to an instance of an object, even though every time, I check, and there is an object with a VRCObjectSync attached to it that Respawn() is called from. And Respawn() is called from the VRCObjectSync, and not the GameObject. This is the error I get from udon graph: [UdonBehaviour] An exception occurred during Udon execution, this UdonBehaviour will be halted. VRC.Udon.VM.UdonVMException: The VM encountered an error! Exception Message: An exception occurred during EXTERN to 'VRCSDK3ComponentsVRCObjectSync.__Respawn__SystemVoid'. Parameter Addresses: 0x00000000 Object reference not set to an instance of an object ---------------------- Program Counter was at: 28 ---------------------- Stack Dump: ---------------------- Heap Dump: 0x00000000: Microphone (VRC.SDK3.Components.VRCObjectSync) 0x00000001: Microphone (VRC.SDK3.Components.VRCObjectSync) 0x00000002: VRCSDK3ComponentsVRCObjectSync.__Respawn__SystemVoid ---------------------- Inner Exception: ---> VRC.Udon.VM.UdonVMException: An exception occurred during EXTERN to 'VRCSDK3ComponentsVRCObjectSync.__Respawn__SystemVoid'. Parameter Addresses: 0x00000000 ---> System.NullReferenceException: Object reference not set to an instance of an object at VRC.SDK3.ClientSim.ClientSimObjectSyncHelper.RespawnObject (VRC.SDK3.Components.VRCObjectSync sync) [0x00000] in .\Packages\com.vrchat.worlds\Integrations\ClientSim\Runtime\Helpers\ClientSimObjectSyncHelper.cs:18 at VRC.SDK3.Components.VRCObjectSync.Respawn () [0x00009] in <6ff4ff48394b436282bb70dc0ff277c2>:0 at VRC.Udon.Wrapper.Modules.ExternVRCSDK3ComponentsVRCObjectSync.__Respawn__SystemVoid (VRC.Udon.Common.Interfaces.IUdonHeap heap, System.Span`1[T] parameterAddresses) [0x0001d] in <b001fa9908f1453c979dae8b67f4c4f7>:0 at VRC.Udon.VM.UdonVM.Interpret () [0x00273] in <62e4a0d35446446b8fa1f8e5755bcfaa>:0 --- End of inner exception stack trace --- at VRC.Udon.VM.UdonVM.Interpret () [0x0033c] in <62e4a0d35446446b8fa1f8e5755bcfaa>:0 --- End of inner exception stack trace --- at VRC.Udon.VM.UdonVM.Interpret () [0x00436] in <62e4a0d35446446b8fa1f8e5755bcfaa>:0 at VRC.Udon.UdonBehaviour.RunProgram (System.UInt32 entryPoint) [0x00063] in .\Packages\com.vrchat.worlds\Runtime\Udon\UdonBehaviour.cs:1098 UnityEngine.Debug:LogError (object,UnityEngine.Object) VRC.Core.Logger:LogError (string,string,UnityEngine.Object) VRC.Udon.UdonBehaviour:RunProgram (uint) (at ./Packages/com.vrchat.worlds/Runtime/Udon/UdonBehaviour.cs:1112) VRC.Udon.UdonBehaviour:RunEvent (string) (at ./Packages/com.vrchat.worlds/Runtime/Udon/UdonBehaviour.cs:1306) VRC.Udon.UdonBehaviour:ManagedUpdate () (at ./Packages/com.vrchat.worlds/Runtime/Udon/UdonBehaviour.cs:551) VRC.Udon.UdonManager:Update () (at ./Packages/com.vrchat.worlds/Runtime/Udon/UdonManager.cs:354)

This was reported as fixed in 2024.4.1p3 but it looks like the problem crept back in and exists in SDK 3.8.2 / 2025.3.1 (haven't tested any other versions). Since the previous canny was closed out as complete, thought I'd open a new one. Prior bug report on this issue: https://feedback.vrchat.com/udon/p/braces-inside-strings-in-vrcjson-can-fail-to-deserialize // This works if(VRCJson.TryDeserializeFromJson("\"{\"data\":\"test\"}", out DataToken token2)) Debug.LogError("Failed to deserialize JSON"); else Debug.Log("Successfully deserialized JSON"); // This fails. Only difference is the braces after the word test in the JSON string. Number of braces or their configuration doesn't seem to make a difference. if(VRCJson.TryDeserializeFromJson("{\"data\":\"test{}\"}", out DataToken token1)) Debug.LogError("Failed to deserialize JSON"); else Debug.Log("Successfully deserialized JSON"); Thanks! -Tea

Whenever I create an OnVariableChanged event through the Plus button in the events sidebar, it produces the error shown in the second image. This occurs regardless of the program asset I try it in, and also on SDK 3.7.1 Soon afterward, it fails to load the event node and removes it as shown in the first image. The node is never visible in the graph view.

Checking the equality/inequality of a system-defined enum with equality/inequality operators ( == / != ) will fail. As a result, this example codes in the document don't work as expected: https://creators.vrchat.com/platforms/android/android-best-practices/#2-detect-mobile-players-in-your-world-automatically public override void OnInputMethodChanged(VRCInputMethod inputMethod) { if (inputMethod == VRCInputMethod.Touch) { // Run code for touch input } else { // Run code for non-touch input } } (The UdonGraph version (attached image) also has an identical issue.) Workaround Cast to underlying values and compare them. if ((int)inputMethod == (int)VRCInputMethod.Touch) Analysis UdonSharp compiles the expression inputMethod == VRCInputMethod.Touch into EXTERN, "SystemObject.__Equals__SystemObject__SystemBoolean" Although Object.Equals(Object) is overridden by Enum.Equals(Object) , which the inputMethod may have, with comparing underlying value, this EXTERN seems to call the Object.Equals directly (maybe via reflection API), and it returns the unexpected result (by only comparing the referencing instances). The EXTERN, "SystemObject.__Equals__ comes from here https://github.com/vrchat-community/UdonSharp/blob/22307065bd408dfd163fe46b0b8b701a4efcbc00/Packages/com.vrchat.UdonSharp/Editor/Compiler/Binder/BoundNodes/BoundInvocationExpression.cs#L420 And replacing the System_Object of this line with System_Enum doesn't work because the Enum.Equals is not exposed. Suggestions Temporary, rewrite the example codes using cast operator Expose System.Enum.Equals And replace the EXTERN with System.Enum.Equals

Maybe this has been the case since VRChat supported SteamVR Input 2.0. Regarding the OnInputMethodChanged(VRCInputMethod inputMethod) argument, on smartphones and desktop PCs, it has the expected values such as VRCInputMethod.Touch and VRCInputMethod.Keyboard. Touch and VRCInputMethod.Keyboard. On the other hand, many VR controllers seem to have unified to VRCInputMethod.SteamVR2. This means that there is no longer a way to distinguish mainstream Vive Wand/Quest/Pico/INDEX controllers, etc. from Udon. This means that automatic tuning according to the characteristics of each controller is impossible. Are there any plans to fix this?

Input Fields selection highlight doesn't appear in-client, despite it appearing in the Unity editor. The selection highlight works in-client, but just not visible. My setup with a properly setup canvas: "Input Field - TextMeshPro (VRC)" with Read Only set to True VRCInputFieldKeyboardOverride component set to Override To note: It previously worked in my project, then stopped out of nowhere. Tried to recreate the input field with a working one in the scene, then the one that was working stopped working.

Gravity and Kinematic flags on VRCObjectSync components don't sync correctly right now and also cannot be set correctly while holding the pickup. To set gravity or kinematic flags, VRChat added two new methods for us: https://udonsharp.docs.vrchat.com/vrchat-api/#vrcobjectsync (they are supposed to behave like a synced variable) There are two bugs related to this: ~ Bug 1: ~ All you need is to create a pickup that has no gravity and then toggle the gravity flag on the VRCObjectSync component with an external button after claiming ownership. Then you let different people in the world pick up the pickup and drop it (to show their own local state). In my tests, this resulted in a pickup where the gravity flag is wildly different on each client and only syncs occasionally or not at all. They would see the pickup drop on my end, but when they pick it up it has no gravity for them. ~ Bug 2: ~ All you need is to create a pickup that has no gravity and then toggle the gravity flag on the VRCObjectSync component in OnPickupUseDown() . In my tests, this resulted in a pickup where the gravity stays enabled after the first OnPickupUseDown() and I am unable to turn gravity off again. To check gravity, the pickup is dropped. You can also just test it out here: Right setup: Bug 1 / Left setup: Bug 2 https://vrchat.com/home/world/wrld_9cefd5ec-4492-43c5-8cd3-05036c494556 Additional note: Since we only got a setter and not a getter method, we are left in the dark here when it comes to analyzing the problem. Reading out the local rigidbody state doesn't give us access to the real synced state. A getter method should be added.

"Op Division" of int node crashes VRChat.exe when the divisor is zero. However, when running in Unity editor it only stops the UdonBehaviour with appropriate error message. --- The head of crash report error.log (local testing and published world case) VRChat by VRChat [version: Unity 2018.4.20f1_008688490035] GameAssembly.dll caused an Integer Divide by Zero (0xc0000094) in module GameAssembly.dll at 0033:2102cb7d. -- The message appears in Unity editor console (running in Unity editor case) [UdonBehaviour] An exception occurred during Udon execution, this UdonBehaviour will be halted. VRC.Udon.VM.UdonVMException: The VM encountered an error! Exception Message: An exception occurred during EXTERN to 'SystemInt32.__op_Division__SystemInt32_SystemInt32__SystemInt32'. Parameter Addresses: 0x00000001, 0x00000002, 0x00000000 Attempted to divide by zero.