Surface Laptop 5 not recognizing eGPU after Windows 11 25H update

Hi @Jack,

Welcome to Microsoft Q&A forum. 

I understand that after following the recent Windows 11 update, your Surface Laptop 5 is recognizing your external GPU only as a PCI-to-PCI bridge rather than fully detecting the graphics hardware. 

This behavior typically happened when the hardware cache or "handshake" between the Thunderbolt controller and the external device needs to be reconfigured at the firmware level. It is possible that the update refreshed certain security policies, causing the connection to pause at the bridge level.

First, in order to address your questions directly regarding why this behavior is occurring: 

• Why the eGPU is not recognized: The recent update likely refreshed the system's security policies or Kernel DMA protection settings. When this occurs, the "handshake" between the Surface and external PCIe devices sometimes needs to be manually re-initialized to function correctly. 
• Regarding Thunderbolt 4 functionality: The presence of the "PCI-to-PCI bridge" actually confirms the Thunderbolt controller is working. However, the system is currently defaulting to a compatibility mode (USB Root Hub) because it has not yet completed the resource assignment required for the GPU. 

To help resolve this, kindly try to force shutdown and restart (also known as a hardware reset). This process will clear the hardware cache more effectively than a normal restart. 

Please follow these steps below to force a shutdown and restart:

1. Firstly, disconnect your eGPU and all other peripherals from the Surface. 
2. Make sure your Surface is unplugged from its power adapter. 
3. Press and hold the Power button for 20 seconds.  The screen may turn off or the Windows logo may flash; please continue holding for the full 20 seconds to ensure the hardware cycle is complete. 
4. Then release the button, wait a few seconds, and then press the Power button again to turn your Surface back on. 
5. Once logged in, reconnect your eGPU and check Device Manager. 

For your reference, you can view the official steps for this procedure here: Force a shutdown and restart your Surface - Microsoft Support 

Please try this step and let me know the outcome. If the eGPU remains undetected, I will be happy to guide you through further isolation steps to ensure your setup is recognized correctly. 

Thank you for your patience and your understanding. If you have any questions, please feel free to reach out. I'm looking forward to your reply.

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Dear Ian-Ng,

Thank you for your previous instructions. I followed all the steps exactly, including the forced shutdown and restart procedure (holding the power button for 20 seconds while disconnected from power and peripherals). Unfortunately, the issue persists. Below is a detailed summary of the problem and the actions already taken.

1. Problem continues: eGPU still detected only as PCI-to-PCI Bridge

After rebooting and reconnecting the eGPU:

The system still does not detect the GPU hardware.

The eGPU enclosure is recognized only as:

PCI-to-PCI Bridge

USB Docking / USB functions

The graphics card does not appear under Display adapters.

The GPU driver cannot be installed because the GPU is not enumerated.

This indicates that PCIe tunneling over Thunderbolt/USB4 is not being initialized.

2. Thunderbolt Controller does not appear

In Device Manager:

I can see:

USB4 Host Router

USB4 Root Router

Thunderbolt Peer-to-Peer

But I cannot see:

Thunderbolt Controller

Thunderbolt NHI

Thunderbolt PCIe Tunneling Driver

This suggests that the Thunderbolt stack is stuck in USB4 fallback mode after the Windows 11 update.

3. Steps already attempted

A. Forced shutdown (20 seconds) → No effect

Performed exactly as instructed.

B. Reinstalled Surface Laptop 5 Drivers and Firmware (latest package)

Completed successfully

Rebooted

Issue remains unchanged

C. Uninstalled USB4 Host Router and USB4 Root Router, rebooted

Windows reinstalled them

Still no Thunderbolt Controller appears

eGPU still stops at “PCI-to-PCI Bridge”

D. Verified Kernel DMA Protection / Core Isolation settings

No improvement in device enumeration

4. Additional symptoms

The eGPU enclosure does supply power and USB functions (= basic USB4 works).

The GPU inside the enclosure is not detectable at all.

Before the recent Windows Update, the same hardware worked normally.

This strongly suggests a driver/firmware handshake regression introduced by the recent Windows 11 update (25H2) on Surface Laptop 5.

5. Requested next steps

Could you please advise on one of the following:

How to manually force reinitialization of the Thunderbolt controller / NHI driver?

Whether a rollback of the Thunderbolt firmware or USB4 stack is possible?

If this is a known compatibility issue in Windows 11 25H2 for Thunderbolt PCIe tunneling?

Whether escalation to the Surface engineering team is needed?

I would appreciate further guidance.

Thank you very much.

Regards,

Jack