FNiagaraScalabilityManager incorrectly reactivates a NiagaraComponent that was deactivated by runtime user code

UE - Rendering - Architecture - Niagara - Oct 1, 2025

Context: The Niagara System is the primary tool to do visual effects inside Unreal. Niagara systems can be culled due to distance. Problem: Once a deactivated Niagara System is culled due to distan ...

Wrong density calculation in UBodySetup::CalculateMass

UE - Runtime - Simulation - Sep 29, 2025

Wrong density calculation in UBodySetup::CalculateMass. The licensee has provided the following analysis and suggested fix: In UBodySetup::CalculateMass, the following code is present: // physical ...

[Mobile/Forward Rendering] PlanarReflection does not work when the reflection plane faces certain directions

UE - Platform - Mobile - Systems - Sep 24, 2025

Note: This repros on 4.27 and all 5.x versions. When using the mobile renderer and/or forward shading, Planar Reflection will simply not work if the reflection plane normal has components that add ...

Post Process Animation Blueprint Crash When Using Blend Node

UE - Runtime - Anim BP - Sep 24, 2025

When using a Blend node inside a Post Process Animation Blueprint, the editor crashes while rendering thumbnails. The crash occurs because USkeletonThumbnailRenderer attempts to draw a thumbnail wit ...

Cook Warning "Saving FText which has been initialized from FString" when a user-defined BP structure contains a native C++ struct with an FText

UE - Framework - Blueprint - Sep 23, 2025

Consider a C++ struct containing an FText. Now consider a used-defined BP structure containing that C++ struct. When cooking an asset that references such a user-defined BP structure, the following ...

TMap "Categories" meta propagates into structs it shouldn't apply to

UE - Gameplay - Gameplay Tags - Sep 22, 2025

When using TMap with "Categories" meta UPROPERTY tag for gameplay tags, it propagates into structs that it shouldn't reaching into. The expectation is that it would only impact the layer of gameplay ...

In 5.6, bWarningsAsErrors does not work with clang

UE - Core - Cpp Tools - UnrealBuildTool - Sep 20, 2025

In 5.6, many warnings and errors specify their command line arguments to the compiler with these new C# attributes:    [WarningsClangToolChain(["-Wno-date-time"], ["-Wdate-time", "-Wno-error=date-ti ...

Ray tracing scene doesn't reflect WPO with instance custom data

UE - Rendering - Features - Ray Tracing - Sep 19, 2025

When custom instance data is used to calculate WPO in a Material and applied to an ISM the WPO value in the Lumen scene (ray tracing scene) is different than the visible scene resulting in incorrect ...

Ensure when calling server RPC from BeginPlay for a component that is not replicated by default

UE - Framework - Networking - Sep 18, 2025

This seems to occur due to the order in which the component is registered and set to replicate in UActorComponent::OnCreatedFromReplication. The component is first registered with the world, which c ...