RealityKit portal crossing leaves a hard PBR lighting seam despite environmentLightingWeight being 0

I’m seeing a device-only lighting discontinuity on PBR entities that intersect a RealityKit portal plane in visionOS 27.

A sharp brightness boundary appears exactly where the portal plane cuts through the entity. The portion outside the portal receives a different physical environment-probe contribution from the portion inside.

The behavior is reproducible with two independent cases:

1. A completely static blue sphere positioned across the portal plane.
2. An orange sphere moved through the portal using ManipulationComponent and the standard visionOS pinch gesture.

Both spheres use:

var material = PhysicallyBasedMaterial()
material.baseColor = .init(tint: .orange)
material.metallic = 0
material.roughness = 1

Each sphere has the crossing and lighting components attached directly:

sphere.components.set(PortalCrossingComponent())
sphere.components.set(
    ImageBasedLightReceiverComponent(
        imageBasedLight: portalImageBasedLight
    )
)

var lightingConfiguration =
    EnvironmentLightingConfigurationComponent()

lightingConfiguration.environmentLightingWeight = 0
sphere.components.set(lightingConfiguration)

The portal is created using the visionOS 27 factory API:

let portal = PortalComponent.makePortal(
    surfaceStyle: .init(width: 1.2, height: 0.8),
    boundaryStyle: .infinitePlane(),
    boundaryMode: .clippingAndCrossing
)

if var component =
    portal.portalEntity.components[PortalComponent.self] {
    component.lightingBlendDistance = 0.2
    portal.portalEntity.components.set(component)
}

For the moving sphere, environmentLightingWeight stays at 0 for the entire interval in which any part of the sphere intersects the portal. The realtime environment-probe contribution only begins fading from 0 to 1 after the complete sphere has cleared the plane.

However, a spatially sharp edge remains:

• 1. In a bright physical environment, the outside portion is brighter.
• 1. In a dark physical environment, the outside portion is darker.
• 1. With UnlitMaterial, the edge disappears completely.
• 1. With PBR—even metallic 0 and roughness 1—the edge returns.
• 1. The static sphere reproduces the issue, so it does not appear to be caused by gesture or lighting-update timing.
• 1. Changing lightingBlendDistance does not soften this remaining edge.
• 1. The issue is visible on Apple Vision Pro but not in visionOS Simulator.

I watched the portal-lighting section of WWDC24 session 10103 and implemented the recommended EnvironmentLightingConfigurationComponent solution. I have also reviewed the documentation for PortalComponent, PortalCrossingComponent, PortalComponent.makePortal, ImageBasedLightReceiverComponent, and environmentLightingWeight.

Is there another component or entity-hierarchy requirement needed to fully suppress the physical environment probe on the host-side fragments of a crossing PBR entity? Or is this a RealityKit rendering issue on physical hardware?

Environment:

• Apple Vision Pro (M5)
• visionOS 27.0 (24M5326g)
• Xcode 27.0 (27A5228h)
• visionOS SDK 27.0 (24M5326e)

Here is a minimal standalone Xcode reproduction containing both the static and pinch-draggable spheres: https://drive.google.com/file/d/13qqOlDJVCCtlFcMaHCBpDkVJgRzmNjBK/view?usp=sharing