MacBook Pro: AppleDCP kernel panics after macOS 26.3 upgrade

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Level 1

4 points

MacBook Pro: AppleDCP kernel panics after macOS 26.3 upgrade

Recurrent Kernel Panics After Upgrade to macOS 26.3 (DCPEXT / AppleDCP)

Hi,

Has anyone experienced or recognised issues related to DCPEXT / AppleDCP kernel panics after upgrading to macOS 26.3?

Since updating from macOS 26.2 to 26.3 (25D125), my Mac has started experiencing random kernel panics and unexpected reboots during normal use. There were no stability issues on 26.2 under the same hardware configuration and workload.

The panic log is consistent across crashes and includes:

DCPEXT1 PANIC - apt firmware: dual_pipe.c:180 sync_pipe_end_of_config()

Faulting task: iomfb_mailbox

Client: AppleDCP-1041.81.2~2-t602xdcp.RELEASE

Backtrace references typically include:

iomfb_mailbox
RTBuddy
IOSlaveProcessor
IOMobileGraphicsFamily-DCP
AppleDCP

This appears to be a firmware-level assertion inside the Apple Display Co-Processor (DCP).

Equipment

MacBook Pro (Apple Silicon, M2 Max)
macOS 26.3 (25D125)
External 5120×2160 ultrawide display at 120 Hz over USB4 / Thunderbolt
No hardware or cabling changes at the time of upgrade

Crashes occur during active use and are not limited to sleep/wake or hotplug events.

Root Cause?

The panic consistently originates from:

dual_pipe.c → sync_pipe_end_of_config()

This suggests a failure during dual display pipeline synchronization inside AppleDCP firmware.

Given:

Immediate onset after upgrading to 26.3
Stable behaviour on 26.2
Identical hardware configuration
Deterministic firmware assertion

This strongly indicates a regression introduced in macOS 26.3 within the display stack (AppleDCP / IOMobileGraphicsFamily-DCP / RTKit mailbox synchronization).

Because this is a firmware-level assert inside Apple’s display subsystem, it does not appear to be application- or configuration-related.

This seems to require a fix in the macOS display subsystem to prevent system crashes, regardless of external display configuration.

MacBook Pro 14″

Posted on Feb 19, 2026 12:48 AM

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Answer 1

Owl-53

Level 10

104,065 points

Feb 19, 2026 1:25 AM in response to c-edv

As a Test

Try using the computer without the External Display

Does the issue persist

Also, try Running with the External Display @ 5120×2160 @ 60 Hz or 3840×2160 @ 120 Hz

Do things get any better

If not

Start now and open an Apple Support Ticket as they are Apple Employees who deal will these types of issues.

See it you can have this escalated to Software Engineering Levels

Product Feedback - and make it known to Apple regarding this ongoing issue

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Answer 2

Barney-15E

Level 10

122,768 points

Feb 19, 2026 6:53 AM in response to c-edv

Can you post the full panic log in the Additional Text area in a reply?

Or, just look in the loaded kexts for last loaded and any third-party kexts.

Does it panic in Safe Mode.

https://support.apple.com/en-us/116946

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Answer 3

Feb 19, 2026 9:08 AM in response to c-edv

macOS Tahoe has been making changes where high quality cables less than 1 meter in length are required when connecting external displays. The cables which ship with external devices generally are subpar quality and do not tend to work with macOS 26.x Tahoe.

It is unfortunate you did not include the complete Kernel Panic log since there are several variations of these DCP Kernel Panics. I've seen people report a bunch of them a couple of years ago as well.....some types of them were confirmed to be due to faulty Logic Boards.

It is generally a good idea to post several of the Kernel Panics to see if they are all identical on the fault types keeping in mind they may all be DCP Kernel Panics, but contain some slightly different reasons & information.

Of course you can open a support case with Apple directly. You will be required to go through their low level troubleshooting where you will be asked to perform a clean install of macOS & test whether the Kernel Panics occur with a clean install prior to logging into your AppleID/iCloud, installing third party software, and restoring from a backup. Then once you exhaust the low level troubleshooting you can have them escalate the issue to their engineers who can actually read & interpret Kernel Panic logs. It will be a long grueling process, but is the only way that Apple can resolve the issue assuming it is an issue Apple created & cares to fix.

Keep in mind that your Mac or even the external display (or cable) may always have had a latent issue here, but it only was revealed with the most recent patch....or it just happens to be coincidence (coincidence does happen).

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