World/Udon Bugs & Feature Requests

Under certain conditions that I can't reproduce reliably, all network events stop working for a player. It looks like it always happens when the owner/master changes. This causes big issues in high frequented instances where the master changes a lot. World where it happens to me: https://vrchat.com/home/world/wrld_3fb6208d-54d7-4a9f-9cf9-11341fa36037 All objects are active and never get deactivated. Serialization and Deserialization works fine for all players. The network is not clogged and is happy. The network events stop working completely for the client that experiences this behavior regardless of the target (All, Owner) and they don't send or receive any events anymore. The behavior never recovers. If another client tries to send a network event directly to that player (owner) the event gets blocked. I verified that the code works by executing the methods on the client with the bug by hand. (Thanks BobyStar) The code sends maybe 3 events in 20 seconds on multiple UdonSharpBehaviours. I attached some code examples that don't get executed from the network event, but if I execute them by hand it works. The error that's after the rpc call was captured on a non-owner client that tried to send a network event to the owner who was experiencing the behavior described above. This was after I pressed a button that executes the "StartLobby" method. In the code example with the Debug logs I see the first log "All players finished race!" but I don't see the "OnGame Done!" on any client.

When calling SetLoops on a VRCTweenHandle created from VRCTween.DelayedCall, it is expected that the tween periodically invokes its callback according to the specified duration and loop count. In actuality however the tween invokes its callback once then terminates, as if SetLoops wasn't called at all.

Log the bool "value" argument for InputUse. Click your mouse and release. Expected: receive "True" once, receive "False" once Actual:

There is a canny asking to whitelist playable director and signal receivers in late 2020. Marked as complete. There are more of them in 2021 saying they don't allow Udon interactions at all I've been using them for days making a complex animation with events firing with them, only to find out nothing works in VRChat. Why was it marked as complete but doesnt work ? Was it removed ? Why is it not available for world creators ? This is way better of a method than any other solutions we need to deal with to achieve events synced with a playable timeline, which this issue rises as the only possibility despite the components being whitelisted. Please allow world creators to fire UdonCustomEvents through the director, signal receiver and animation clips. I was going to make a free prefab that would allow people to easily make synced song animations and its lyrics in an optimized way, but the only solution i see now is an update loop and spam toggle objects with if statements, or other random solutions that feel like a hack rather than a proper way to do this when the components to do it are literally right there. Please make this change to allow creators to make emotional animations with more ease. This is extremely frustrating to have such a limitation suddenly appear in front of me for no reason. Thank you.

Environment: Unity version: 2022.3.22f1 VRChat SDK Worlds: 3.10.3 VRChat SDK Base: 3.10.3 UdonSharp included with SDK Project uses Prefab Mode / PrefabStage with UdonSharpBehaviour components YamaPlayer package present: net.kwxxx.yama-stream 1.5.18 Observed: When opening or editing prefabs containing UdonSharpBehaviour components in Prefab Mode, Unity logs repeated ArgumentNullException errors from OdinSerializer UnitySerializationUtility. Error: ArgumentNullException: Value cannot be null. Parameter name: unityObject VRC.Udon.Serialization.OdinSerializer.UnitySerializationUtility.SerializeUnityObject(...) UdonSharp.UdonSharpBehaviour.UnityEngine.ISerializationCallbackReceiver.OnBeforeSerialize() and similarly: UnitySerializationUtility.DeserializeUnityObject(...) UdonSharp.UdonSharpBehaviour.UnityEngine.ISerializationCallbackReceiver.OnAfterDeserialize() Trigger: Open a prefab containing UdonSharpBehaviour in Prefab Mode Move a child object or let PrefabStage autosave run Errors repeat, sometimes dozens/hundreds per save Expected: PrefabStage autosave should not throw if a Unity pseudo-null UdonSharpBehaviour or serialized target is encountered. It should skip invalid objects or handle UnityEngine.Object pseudo-null safely. Additional finding: For diagnosis only, I temporarily tested a local guard around the SDK serialization path. The test indicated that the affected object was not a normal C# null reference, but behaved as null through Unity's overloaded UnityEngine.Object null comparison. With that guard in place, the exception stopped. I am not using this as a permanent workaround and do not intend to publish content with a modified SDK. This observation is included only to help identify the likely failure path. Additional observation: I have encountered this issue twice. In both cases, once the issue started occurring in the project, checking out older repository commits did not reliably make the issue disappear. This suggests that the trigger may involve Unity Library/cache/generated SDK state or some project-local serialized state, not only the currently checked out asset files.

Components sometimes "break" in Unity 2022. They are collapsed, and expanding them reveals nothing. It affects different types of components, i.e. UdonBehaviours or MeshRenderers. It can be fixed by selecting a different game GameObject. In my world projects, it's caused by the following error: ArgumentNullException: Value cannot be null. Parameter name: unityObject VRC.Udon.Serialization.OdinSerializer.UnitySerializationUtility.SerializeUnityObject (UnityEngine.Object unityObject, VRC.Udon.Serialization.OdinSerializer.SerializationData& data, System.Boolean serializeUnityFields, VRC.Udon.Serialization.OdinSerializer.SerializationContext context) (at ./Packages/com.vrchat.worlds/Runtime/Udon/Serialization/OdinSerializer/Unity Integration/UnitySerializationUtility.cs:1031) UdonSharp.UdonSharpBehaviour.UnityEngine.ISerializationCallbackReceiver.OnBeforeSerialize () (at ./Packages/com.vrchat.worlds/Integrations/UdonSharp/Runtime/UdonSharpBehaviour.cs:272) UnityEditor.EditorApplication:Internal_CallGlobalEventHandler()

When attempting to use String Loading to download a file through Udon, if for whatever reason the download never completes, neither the success or error functions will be called without any indicator or way to know what's going on. This is different with Image Loading where there's a progress float that tells us the progress of the download. https://creators.vrchat.com/worlds/udon/string-loading https://creators.vrchat.com/worlds/udon/image-loading This causes problems in practice because Udon will be waiting for a callback that will never be called, and we don't know if it's because of slow internet or a failure of the request that hasn't and will never thrown any error. Requesting parity for String Loading to be able to get the download progress, both so we can display the state to users as well as handle the scenario by providing fallback logic.

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

Repro: var bounds = new Bounds( Vector3.zero , Vector3.one ); Debug.Log("Bounds: " + bounds.size); bounds.Expand(100f); Debug.Log("Bounds: " + bounds.size);

Vector3Int.Clamp doesn't change anything when I tested it with this simple U# code: https://gist.github.com/nuip/9f249bcdd1f800483c1e971cf9e1a102