Which thresholds does Premiere Pro apply to offload Lumetri Color effects to the GPU versus CPU rendering?

Premiere Pro's Mercury Playback Engine can offload Lumetri Color effects to the GPU when a compatible CUDA, OpenCL, or Metal device is detected and the effect is supported. The software determines rendering mode based on runtime conditions that are not publicly documented, particularly regarding GPU memory availability, texture dimensions, and driver compatibility. Users observe intermittent GPU utilization spikes or temporary stalls, suggesting an internal heuristic that triggers fallback to CPU‑only processing under unspecified thresholds.

This behavior varies across Premiere Pro releases (2023, 2024) and GPU vendor implementations, and third‑party plugins or LUTs may force software rendering regardless of hardware capability. The precise goal is to identify the undocumented criteria Premiere Pro uses to decide between GPU‑accelerated and software‑only Lumetri Color rendering under memory‑constrained conditions.

Which specific resource thresholds govern this switch? How can they be reliably observed or predicted?