Surface Pro 9 lagging after sleep but only until power supply is conected

100% agree!

Microsoft, what are you doing about this? Your last update reduced the performance of my Pro 9 and I'm having to use a work around to get the device to work right. Please fix this!

Just adding on that my Surface Pro 9 (12th Gen Intel i7, wi-fi only) also began having this problem after the update a few weeks ago.

For me, restarting the device fixes it until it goes to sleep again. The previously mentioned key combo (ctrl + shift + windows key + B) also fixes it. Like the OP, there's nothing resource-intensive running on my device. I've checked the Task Manager and I don't see any high usage on anything when this is occurring. From my perspective it seems to just be a display issue.

My device didn't have the Intel Graphics Command Center installed, so I haven't tried that suggestion yet. I will next time it happens, but it does still seem that there was something wrong with the update that should probably be addressed.

I am not sure what is the 'correct' fix, BUT I suspect you will have success as I have with the following:

Solution 1:

Settings > System > Display > Advanced Display > Choose a refresh rate > Dynamic (60 Hz or 120 Hz)

The emboldened section was previously "60 Hz" for me. This resolved the issue when running on battery.

Solution 2:

IF it does not resolve the issue, then another suggestion was "Windows+Ctrl+Shift+B" every time your computer awakes from sleep, which is quite tedious, but it is available.

Solution 3:

The third option, also not a viable option for me, is to keep it plugged into the power.

Hope this helps. #1 worked for me after #3 proved to be too tedious, so I know your frustration.

I'm aware of all that. I read the whole thread. My point of commenting is to show that it isn't an isolated incident, and that the Windows update clearly introduced an issue that should still be acknowledged and addressed officially.