Camera Raw 18.7 AI Denoise performance regression on M2 Ultra Mac Studio

I am seeing a significant performance regression with AI Denoise in Camera Raw 18.7 on a 2023 Mac Studio with an Apple M2 Ultra.

System

• Mac Studio (2023)
• Apple M2 Ultra, 24-core CPU
• 128 GB unified memory
• macOS 27.0.1
• Camera Raw 18.7
• Photoshop 2026
• Sony A1 II RAW files, approximately 49.8 MP (8640 × 5760)

Problem

AI Denoise on comparable Sony A1 II RAW files previously completed in under 10 seconds on this same Mac. It now typically takes approximately 15–20 seconds.

I reproduced the problem by opening a Sony A1 II ARW directly in Photoshop/Camera Raw, so Lightroom Classic, its catalog, previews, and the location of the Lightroom photo library are not involved.

During a recent Camera Raw Denoise test, Camera Raw estimated approximately 20 seconds. While Denoise was running, Activity Monitor showed the Mac remaining approximately 86–94% CPU idle. GPU History also showed relatively low GPU activity rather than sustained heavy utilization.

Camera Raw Preferences > Performance identifies the Apple M2 Ultra and reports: “Your system automatically supports full acceleration.” Graphics Processor is set to Auto.

Hardware/performance checks already performed

• Apple hardware diagnostics completed successfully with no reported hardware problems.
• Geekbench 7 Metal GPU score: 198,647
• Internal SSD Blackmagic Disk Speed Test: approximately 7,148 MB/s write and 5,736 MB/s read
• Memory pressure is low with 0 bytes compressed and 0 swap used
• 128 GB unified memory
• The slower Denoise performance also occurs with the RAW file on the internal SSD.

The computer therefore appears to have substantial CPU, GPU, memory, and storage resources available while Denoise is running.

Expected behavior

Denoise performance comparable to what I previously experienced on this same hardware and similar Sony A1 II RAW files — generally under 10 seconds.

Actual behavior

Approximately 15–20 seconds per image, with relatively low CPU and GPU utilization during processing.

Has there been a change in the AI Denoise processing path in recent Camera Raw versions that could account for this performance regression on Apple Silicon/M2 Ultra systems?