Lightroom Classic 15.5.1: Progressive physical-memory accumulation during Develop navigation with GPU acceleration enabled; memory remains retained while idle

I've spent a couple of hours researching this thinking it was some other process i was doing and it's causing some memory issues and eventually maxing out my swap memory on my m1 max 64GB Ram macbook pro. Please advise (using Tahoe 26.5.1 (25F80))

Title: Lightroom Classic 15.5.1: Progressive physical-memory accumulation during Develop navigation with GPU acceleration enabled; memory remains retained while idle

Summary:
On Lightroom Classic 15.5.1, simply navigating through previously edited RAW photos in Develop, without making any new edits, causes Lightroom's OS-measured physical footprint to increase by several gigabytes per image. In a clean reproduction, Lightroom grew from ~1GB to ~31GB after viewing five images. No material reclamation occurred during a three-minute idle period. The same behavior reproduced on 15.5, where Lightroom reached ~48-51GB and remained at that level for ten minutes idle; quitting and relaunching Lightroom reset the process footprint to ~946MB.

Disabling Use Graphics Processor dramatically changes the behavior: on the same first two images, GPU-enabled Lightroom grew by +13GB and +6GB, while GPU-disabled Lightroom grew by only +1.7GB and +0.6GB. This strongly implicates Lightroom Classic's GPU-accelerated Develop path.

In ordinary editing sessions this progressive footprint growth eventually produces macOS memory compression and multi-gigabyte swapouts, corresponding with severe Lightroom sluggishness/freezing.

Environment:
- Lightroom Classic version: 15.5.1 [202608131348-cab7eed5] (also reproduced on 15.5 [202607291506-b8869fa7] before updating)
- Camera Raw: 18.5.1 [2687]
- macOS: 26.5.1 (25F80)
- Hardware: Apple M1 Max (arm64), 64GB unified memory — Adobe's documented minimum for full GPU acceleration/AI features on Apple Silicon is 16GB; this system has 4x that
- GPU config tested: Custom, with Display/Image Processing/Export all enabled and Preview Generation set to Auto (a valid, Adobe-supported manual configuration — Lightroom's own UI confirmed "Full graphics acceleration is enabled")
- Catalog: ~5.1GB, local SSD, no network/cloud storage involved
- Measurement tools: Lightroom's own Preferences > Performance > System Info panel, and macOS's `footprint` command-line tool (reports phys_footprint, the same physical-memory accounting macOS uses for memory-pressure and jetsam decisions)

Steps to reproduce:
- Launch Lightroom Classic fresh (confirm low baseline memory via Activity Monitor or footprint)
- Open a catalog containing photos with substantial existing, saved Develop-module edit history (prior local retouch/heal work, correction masks — some with Remove/AI-related edits from earlier sessions). Performing a new AI/Remove operation during the reproduction itself is not required
- In the Develop module, navigate to a previously-edited photo, let it render a few seconds
- Navigate to a different previously-edited photo, repeat for 4-5 photos total, viewing only — no new edits
- At each step, check Preferences > Performance > System Info for "Dedicated GPU memory used by Lightroom," and independently check `footprint -p <pid>` for phys_footprint

Expected result:
Memory should remain bounded, or be reclaimed sufficiently, that ordinary Develop navigation does not progressively consume tens of gigabytes of physical memory and drive macOS into compression/swap.

Actual result:
Physical memory footprint climbs steadily across successive images and shows no material reclamation over the idle periods tested, even though the per-image entries in the System Info "Cache1" list do change/rotate as you move between photos. The total physical footprint is not accounted for by what's visible in that panel.

Data — GPU acceleration ON, version 15.5.1, fresh launch:
- Baseline: 194MB GPU-reported / 1.05GB phys_footprint
- Photo 1 (aar05249.ARW): 7.9GB GPU-reported / 14GB phys_footprint (+13GB)
- Photo 2 (aar05189.ARW): 14.2GB GPU-reported / 20GB phys_footprint (+6GB)
- Photo 3 (aar05367.ARW): 19.0GB GPU-reported / 25GB phys_footprint (+5GB)
- Photo 4 (aar05078.ARW): 20.2GB GPU-reported / 27GB phys_footprint (+2GB)
- Photo 5 (aar04996.ARW): 22.9GB GPU-reported / 31GB phys_footprint (+4GB)
- +1 min idle in Library view, no navigation: 31GB (peak 34GB), no change
- +2 min idle: 31GB (peak 34GB), no change
- +3 min idle: 31GB (peak 34GB), no change
- No new edits, exports, or AI operations were performed during this sequence — only viewing already-edited photos

Data — same test on 15.5 (before updating to 15.5.1), same pattern, larger absolute numbers:
- Growth across a comparable 5-6 image sequence (phys_footprint, peak in parentheses): 30GB (31GB) -> 33GB (37GB) -> 42GB (42GB) -> 51GB (51GB)
- After navigation stopped, footprint settled to 48GB (peak 54GB), then held at exactly 48GB for a separately-logged, full 10-minute idle period with zero photos touched
- Quitting and relaunching Lightroom immediately reset phys_footprint from 48GB to 946MB, demonstrating a full quit/relaunch reliably reclaims the memory; no other reclamation action was tested

Data — GPU acceleration OFF (Preferences > Performance > Use Graphics Processor > Off), version 15.5.1, fresh launch, same photos:
- Baseline: 0MB GPU-reported / 912MB phys_footprint
- Photo 1 (aar05249.ARW): 0MB GPU-reported / 2.65GB phys_footprint (+1.7GB)
- Photo 2 (aar05189.ARW): 0MB GPU-reported / 3.25GB phys_footprint (+0.6GB)
- Compare to the same two photos with GPU on: +13GB and +6GB respectively — roughly a 7-10x smaller increase with GPU disabled
- Idle reclamation with GPU disabled was not separately tested, so this speaks only to growth rate, not whether GPU-off allocations are themselves fully reclaimed

Additional context:
- Related but not identical: an existing report describes GPU memory filling during Panorama/HDR merge and not being released until Lightroom is restarted (community.adobe.com/t5/lightroom-classic-discussions/hdr-panorama-merging-ram-not-being-released). Adobe's response there was to ask the reporter to test under 15.5. This report reproduces the same underlying retention pattern via a different trigger — ordinary Develop-module navigation, no Panorama or HDR involved — confirmed still present on 15.5.1
- Adobe's published fixed-issues list for the 15.x line does not mention this Develop/GPU memory-retention behavior as addressed

Why this matters:
This reproduces from ordinary use of the Develop module on hardware well above Adobe's own stated minimum for full GPU/AI feature support. In real editing sessions working through a shoot of dozens to hundreds of photos, this progressive footprint growth has been independently measured (via a custom 1-second-resolution system sampler run over several days of normal use) to correspond with macOS memory compression and eventual multi-gigabyte real disk swapouts, alongside severe application sluggishness — observed on multiple separate occasions, both before and after updating to 15.5.1.

Full minute-by-minute and second-by-second system telemetry covering this entire investigation is available on request.