MacBook Pro very slow, lagging, running very hot after upgrading to macOS 26

michaelfrommalmø wrote:

I don't think Bitdefender is the problem. Even when no Bitdefender processes are running the fan runs crazy and the MBP run very warm and lagging like **** ...

I had Bitdefender also before upgrading and there was no problem ... the upgrade to Tahoe 26 started this trouble

What do you think "BDLDaemon" is in your first screenshot? That is part of the background processes from Bitdefender. It is even the top most in the CPU utilization column. Uninstall Bitdefender by following the developer's instructions and hope it removes all traces of the software from macOS. You can run EtreCheck afterwards to see if any remnants of Bitdender remain.

FYI, anti-virus apps are always running in the background at a very low level in the OS where they interfere with the normal operations of macOS.

In addition to anti-virus software......cleaning/optimizer apps, and third party security software also run in the background at very low levels within macOS and interfere with the normal operations of macOS. These types of apps tend to cause more problems than they solve. There is no reason to have any of these types of apps on a Mac since macOS has great built-in security as long as the user also practices safe computing habits as outlined in the following article:

Effective defenses against malware and other threats - Apple Community

FYI, I don't even recommend these types of apps for Windows anymore for the same reasons. Plus many of these types of apps now contains ads and will sell your personal information. Plus they can actually decrease system security.

Part 1 of 3

Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.

Safe Mode will also eliminate Third Party Software, extensions and drivers from loading. It will only load the Minimum amount of Core Apple Processes to allow the the computer to function at a reduced Level of Performance 

Does the issue present in this mode ?

Sometimes a Safe Boot followed by a Normal Boot will just put things right.

If not - there could be something in the main User Account playing up. To further isolate this - Set up users, guests, and groups on Mac. Then log out of the Main User account and log into the dummy account and test again if the issue persists.

If the issue is present in the dummy account - then, this appears to be a System Wide issue on the computer.

Part 2 of 3

To Drill Down further and to avoid a session of Q&A, Q&A  and Q&A  

Download the Application Etrecheck  ( External Link ) directly from the Developer.

The Application is Not a " Silver Bullet "  and is  only a tool to examine the Hardware / Software used on this computer 

This is a Diagnostic Tool that makes no changes to the computer Hardware / Software used on this computer 

The application is free or paid from added features. 

The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<

Part 3 of 3

There are 4 Categories of Third Party Software / Services that are baffling.

In no special order 

Third Party 2 Way Firewalls 

like Lulu and Little Snitch 

Commercial VPNs 

They may not be what one believes they are doing for the computer and what they actually are doing behind the scenes They may also reduce you Internet Speeds by upwards of 30% 

https://gist.github.com/joepie91/5a9909939e6ce7d09e29

VPN: What you need to know - Apple Community

Third Party Security Software 

There are no known Windows-like Viruses in the wild that self replicate and affect macOS, because of the underling UNIX  Foundation and Permission Limitation. 

The Operating System resides in a Sealed and Read Only Volume that cannot be opened by the User nor by Third Party Applications.

The Only thing this Antivirus software is protecting is the Bank Account of the Developers and for zero return to the User aside from the problems this software creates.

Security. Built right in

Mac app security enhancements

The Built in Security  is all that is required to protect the computer.

Protecting against malware in macOS

Third Party Disk Cleaners / Optimizer 

Any Third Party Applications that will interfere with the normal operation of the OS,  is an invitation for disaster. 

Certain Applications maybe available on the Apple Apps Store - this only means the Developer is prepared to pay Apple a percentage on each sale. 

What the Application may do to the computer is up to the User to check this out before purchase

To put the Third Party Disk Cleaner / Optimizer in context and the damages it may have or has already done.

This type of applications can or will Muck Up your User Account ( Home Folder ) of this machine.

It does not touch the Operating System itself unless you consider your User Account ( Home Folder ) as part of the Operating System.

The Operating System is hosed

michaelfrommalmø wrote:

I don't think Bitdefender is the problem. Even when no Bitdefender processes are running the fan runs crazy and the MBP run very warm and lagging like **** ...

I had Bitdefender also before upgrading and there was no problem ... the upgrade to Tahoe 26 started this trouble

Your choice. I mean, Bitdefender is using the most CPU resource in your screenshot so it seems a very likely culprit to me. If you weren't sure what BDLDaemon was, this was the first google hit: https://www.bitdefender.com/consumer/support/answer/1728/.

Not sure why 'my system was fine on Sequoia but not on Tahoe' means it must be Tahoe that is the problem. It's not. It's almost always software the user has installed that is not fully compatible with Tahoe.

So I'll repeat...Completely uninstall bitdefender. It's unnecessary, and if you read the article linked above you'll see that they admit, "If your Mac is running slower after installing Bitdefender Antivirus, it’s probably because of the background scanning done by BDLDaemon."

michaelfrommalmø wrote:

Any ideas?

Completely uninstall bitdefender. Hopefully the developer provides an UnInstaller.

After updating it is common that Spotlight re-indexes your Mac. Depending on configuration and the amount of data you have on your Mac, it can take up to two days for Spotlight to re-index your Mac.

As for Downgrading to a pervious version of macOS like Sequoia ?

What is the users tolerance for " Risk " ?

1 - Is this your Only computer and you would not be able to live without it for a fews days if the downgrade procedure goes wrong ?

2 - Does the user have access to another Apple computer, that currently is running macOS 15 / 26 , that could be used to Revive or Restore the computer  Firmware  ?

3 - Does the user have at least 2 -  no -  make that 3 backups from a time before the computer was upGraded to macOS 26 Tahoe ?

Have a 3-2-1 Rescue Plan in place and always current

3 Backups using 2 methods and 1 off site incase of natural disaster or un-natural disaster.

Each of the above should be done to a Dedicated Single Purposed External Drive 

Below link is intended to augment what TM Backup does 

https://bombich.com

If the owner of this computer should answer NO  to any of the above questions

Then downgrading the computer Is Not Recommended 

There has been sufficient advice offered, from more than 1 knowledge contributor for the User ( you ) to make an informed and educated choice what remedial actions are required for this computer.

The suggestions have been put forth on a volunteer basis, in good faith and in the best interests of the computer.

Which do not always align with the User's ( your ) expectations

michaelfrommalmø wrote:

Thank you for all the inputs ... I will work my way through them.

Sorry, for taking up your precious time ...

When you have worked through all the points and reported back the findings

That is when our collective times will have been well spent for the user ( you )

EDITED - 🦉-53