Curve Retargeting does not work with SourcePose retarget mode

UE - Anim - Rigging - Retargeting - Jan 14, 2026

Currently we build what source curves we are going to remap is done inside of: FIKRetargetCurveRemapOp::AnimGraphPreUpdateMainThread But in our ikretarget processor code we skip calling that functi ...

Detaching a component may not be replicated to clients

UE - Networking - Jan 13, 2026

Because the archetype for scene/static mesh components has a null value for AttachParent, there are some situations where changes to a replicated component's AttachParent are not replicated to clien ...

Detaching a component with "KeepRelative" location rule can result in incorrect location on client

UE - Networking - Jan 13, 2026

When receiving a replicated detachment, USceneComponent::PostRepNotifies will call DetachFromComponent with the KeepWorldTransform detachment rule. If the component is detached on the server with th ...

bWeldSimulatedBodies not replicated with attachment

UE - Simulation - Core - Jan 13, 2026

The bWeldSimulatedBodies attachment parameter is not replicated to clients, both in USceneComponent's attachment replication handling and in AActor's FRepAttachment struct. If AttachToComponent is c ...

USceneComponent::AttachToComponent may not be called on client depending on replication order

UE - Networking - Jan 13, 2026

If the component being attached is received first, OnRep_AttachParent will set bNetUpdateAttachment to true, so USceneComponent::PostRepNotifies will call AttachToComponent. If the attach parent is ...

HISM flickering when any character is visible

UE - Rendering - Architecture - RHI - Jan 12, 2026

On an NVIDIA GPU, Instanced Static Meshes can flicker when a Groom card or mesh LOD is visible. This appears related to an issue rendering the ISM into the Scene Depth. At the end of the Prepass, t ...

Light Function Materials containing a Texture Sample and Rotator nodes will fail RHI Validation

UE - Rendering - Architecture - RHI - Jan 12, 2026

Using a Light Function Material that contains a Texture Sample and Rotator nodes will cause RHI Validation to fail with the following error: LogOutputDevice: Error: Ensure condition failed: Bindings ...

Lumen Global Distance Field Trace Leaking due to Surface Cache Sampling

UE - Rendering - Graphics Features - Jan 12, 2026

At specific distances from a thin wall, surfaces inside of a sealed chamber can receive indirect lighting from outside, leaking light into the chamber. This appears to be due to how SWRT handles sa ...

Temporal blur artifacts on Geometry Cache Components in Blueprint actor

UE - Editor - Content Pipeline - Alembic - Jan 9, 2026

When a Geometry Collection is in a Blueprint, attached to other components, it can render incorrect motion vectors at some angles. In the test project, any angle that is not a multiple of 45 will re ...