[CedricGuillemet]

ScheduleFrame chained EndFrame as an AfterRenderScheduler continuation of the JS frame task. arcana releases the task's FrameCompletionScope before running its continuations, so the render thread could drain AfterRender before EndFrame was queued. EndFrame(N) then ran a frame late, consumed frame N+1 and left EndFrame(N+1) with a null Frame:

NativeXrImpl.cpp:410 assert(m_sessionState->Frame != nullptr)

Queue EndFrame on AfterRender from the FrameStart task instead. The frame completion scope acquired in that task still keeps the AfterRender tick from running until the JS callbacks are done, and FrameTask still completes only after EndFrame, which EndSessionAsync relies on.

NativeXrFrameLifecycle.EndFrameAlwaysHasActiveFrame aborted 10/10 runs within 2.4 s before this change and passes 60 s runs with it.

[Copilot]

🟢 Approval recommended

The focused scheduling change addresses the race while preserving callback synchronization and shutdown completion guarantees.

No open issues 🎉

What changed in this PR

Fixes NativeXr frame ordering so EndFrame runs on its own frame’s AfterRender tick.

Changes:

• Queues EndFrame directly from the FrameStart task instead of a JavaScript-task continuation.
• Preserves frame-completion synchronization and session-shutdown ordering.

File	Description
Plugins/​NativeXr/​Source/​NativeXrImpl.cpp	Schedules EndFrame earlier and documents the timing race.

_{Review effort: Balanced}