OS 26: Long lag with "Open …" and "Save as …" dialogs.

Christoph Drösser wrote:

Since I installed OS 26, it suddenly takes a loooong time either picking a file (with the "Open …" dialog, or picking an attachment in Mail etc.) or saving a document – anything that brings up the Finder-like file structure. I get the spinning wheel for around 15 seconds! When I do the same thing immediately afterwards, there's no lag. But an hour later it might be the same.

I'm hoping this will sort itself out, maybe some indexing going on in the background or whatever. Has anybody experienced the same phenomenon?

Have you shut down and restarted more than once since your upgrade...

>Shut Down

To trouble shoot further you can:

—A SafeBoot Start up your Mac in safe mode - Apple Support will sort many anomalies

Does a quick disk repair before it fully boots up, and certain system caches get cleared and rebuilt, third party system modifications and system accelerations are disabled temporarily.

Login and test. Reboot as normal and test. Caches get rebuilt automatically.

This test will tell you if third party interference; most extensions etc are not loaded in safe boot mode.

—Test issue in another user (or guest user) account Change Users & Groups settings on Mac - Apple Support

This will tell you if it a universal issue or isolated to your user/admin account. 

***wireless keyboard with rechargeable batteries— connect the charging cable, this will make the wired keyboard successful Safe Boot your Mac.

unplug all non-essential peripherals when testing

Uninstall all third party apps that are Cleaners/Optimizers/VPN/Anti-Virus

all known to cause issues on the macOS

if no insight or resolve to sort upgrade issues re-install the macOS on to of the existing macOS

How to reinstall macOS

Recovery (both M1/M2/M3/M4 and Intel) — How to reinstall macOS - Apple Support

I just want to confirm that I am experiencing this issue also.

I have over 160GB of available storage on my Mac Studio 2025 M4 Max and 36GB of RAM with only 15% used.

Finder works fine, it's just whenever when that small window is displayed for saving or opening files.

Found an old thread back from an identical issue under Mavericks and that said to basically delete iCloud cached data using the following command:

rm ~/Library/Caches/CloudKit/CloudKitMetadata*;killall cloudd

Pleased to say, that seems to have fixed it, at least for now.

Christoph Drösser wrote:

I think what this article talks about is hard disk space – I have a ton of that, if there's any problem it would rather be RAM memory.

Additional info: a barebones test user account seem to run flawlessly. But my main account is behaving fine too all of a sudden. Maybe the OS update helped. Will post back if it gets worse again.

Nope, the problem persists.

EtreCheckPro is an excellent tool for finding and sorting out various problems.

Download and run the free version of EtreCheckPro, from > https://etrecheck.com/en/index.html

Then post back here with your Report, as per > How to use the Add Text Feature When Post… - Apple Community

Run EtreCheck Pro while logged into your main user account.

On a hunch, i disabled "Optimize Mac Storage" and restarted. This seems to have resolved the problem.

Sounds like your running low on free storage space.

see > Free up storage space on Mac - Apple Support

Having this same problem - suddenly over the past week. M2 MacBook Air, fully maxed out spec, mac os26.1. 900gigs available disk space (with about half purgeable and half actually there). The problem doesn't seem to be associated with any recent macOS update, just randomly started. I suspect the culprit is iCloud, but none of the solutions - safe mode, terminal flush of CloudKit cache seem to resolve it. I can confirm that an alternate user account that has little associated with it works fine.

Just started to experience this as well, I get the rainbow wheel and lag and folders to save to populate very slow. Mac is less then a month old

Seeing exactly the same slow issue with "rainbow wheel" (SBBoF) and no idea of the cause.

Thanks