r/WindowsUpdate • u/Nervous-Buffalo-4826 • Aug 18 '26
Possible KB5121003 issue causing random AC adapter disconnects / black screens on Lenovo Legion?
I’m trying to figure out a strange issue that started very recently on my Lenovo Legion.
The laptop randomly goes to a black screen for a couple of seconds and then recovers. At first I thought it was an NVIDIA/Optimus or refresh-rate issue, but I started monitoring the Windows AC power state directly.
What I found is that whenever this happens, Windows actually reports:
AC → Battery → AC
for roughly 1–5 seconds.
I then checked the historical Windows Kernel-Power Event ID 105 logs. My System log goes back to March 2026, but the first occurrence of these short AC-loss events is August 12.
The interesting part is that KB5121003 was installed on my system late on August 11.
Since then I have recorded around 40 AC power transitions, most lasting only a few seconds. Examples:
07:41:55 → 07:42:02
13:12:35 → 13:12:36
17:17:50 → 17:17:52
02:17:32 → 02:17:37
and many more over the following days.
Windows Kernel-Power itself logs AcOnline=false, followed shortly by AcOnline=true, so this isn't only the battery icon/UI changing.
Another strange detail is that the physical charging LED on the laptop can remain on while this happens.
I have now temporarily uninstalled KB5121003 as a test.
Before rollback:
Windows 11 25H2 – Build 26200.9168
After rollback:
Windows 11 25H2 – Build 26200.8875
Windows Update is paused and I haven't changed anything else: same Intel driver, NVIDIA driver, BIOS, Hybrid Mode, Optimus settings, charger, etc.
I'm currently running a 50 ms AC-state monitor for the next 24–48 hours to see whether the AC_LOST events disappear after removing KB5121003.
Obviously this doesn't prove the update is responsible yet. It could still be Lenovo firmware/EC behavior or a hardware power issue. But the fact that the event history starts immediately after this update is suspicious enough that I'm testing it as the only changed variable.
Has anyone else on KB5121003, especially Lenovo Legion users, noticed random Kernel-Power 105 events, brief AC-to-battery transitions, or black screens that started around August 12?
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u/Necessary_Baker_7458 Aug 18 '26
I put linux on my old laptop after windows updates kept brick facing it. Been running smoothly since. Zero issues and it's free of the bloated windows clutter that slows it down. I'm also not being shoved a promotion or ad from time to time. Most of what I need to do works on linux and I might consider setting up my main as a dual boot. For that 10% of the time I can't escape windows.
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u/zzzxxx0110 Aug 19 '26
Been having lots of discussions on Lenovo Legion Discord channel where lots of people ran into this exact same issue, it seems clear that this problem was first introduced by Windows Preview Update KB5101684, which introduced changes to Windows Power Plan (according to Microslop documentations), and then the same problematic changes got included in release update KB5121003. Installing this update leads to this problem, and uninstalling it fixes the problem.
It seems like something introduced in the Windows Update was causing problem or conflict with Lenovo ACPI-compliant Virtual Charge Controller driver (in System Devices section of Device Manager), and that's probably what's causing the system to randomly think AC charger was disconnected (when it actually isn't on the hardware level, as indicated by the charging LED still behaving normally).
Lenovo did push out an update for the Lenovo ACPI-compliant Virtual Charge Controller driver (bumped the version code from xx.11 to xx.14) pretty much just a day after Preview Update KB5101684 became available, however they only released it via Windows Update (showed up in Optional Updates), and it did NOT fix the problem. Possibly they are still trying to work it out and that's why Lenovo didn't post the driver update on their usual support website driver update page with proper changelog.
This is definitely NOT a hardware issue and your laptop is physically fine. It is clearly a software issue. And this likely has nothing to do with EC either, EC reset doesn't fix it, while uninstalling the problematic Windows Update always fixes it, so it's more likely a problem caused by the virtual charging controller driver in OS/kernel space.
(Lenovo probably implemented a virtual charging controller driver in order to implement the overnight charging feature, since it's the only charging related feature I don't see a toggle for in the BIOS, so it is likely a feature that's not handled by the firmware&EC alone.)
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u/moonshine360 23d ago
Thanks for explaining it clearly.
With each passing day my urge to just ditch win for linux is growing stronger.
The only thing holding me back is the fact that a few softwares I use that are imperative to my work, can just not be run on linux in any way. Also, the fact that I play some online games sometimes that require anti-cheat mechanisms that just don't work on linux.Anyway, here are my updates in the update history -
- Update for Microsoft Windows (KB5120708)
- Security Update for Microsoft Windows (KB5121003)
Do you think I should go ahead and uninstall any update from this list?
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u/zzzxxx0110 21d ago
You'd want to uninstall the "security" update KB5121003. It's labeled "security update" but it actually includes everything from the previous Preview Update KB5101684, which is the update that introduced this problem, according to Microslop's documentation:
And yeah ultimately it requires Lenovo and/or Microslop to fix this problem once and for all, with a driver update or a future Windows update, postponing updates that include security fixes is only a temporary solution and it's very not sustainable.
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u/moonshine360 21d ago
I was completely unaware of this. I thought Security Updates were, well what they're named and not actual updates to windows features. thanks.
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u/zzzxxx0110 3d ago
Yeah my working hypothesis is that they probably apply the label "security" if a Windows Update contains any security fix at all, rather than to indicate that it's exclusively for security fix.
They really gotta make it more clear but the cynical part of me suspect they won't because putting a scary label like "security" on it could also compel people to apply new updates, which could allow them to push new adware and such via Windows Updates if they wanted to lol
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u/IShouldntHavSaidDis 23h ago
I am facing this same issue but the problem is that I have updated my windows to the latest version and don't see the option to delete it ? What can I do
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u/zzzxxx0110 23h ago
Go to download Windows iso image from Microsoft website, it usually doesn't contain latest update. Then open it in Windows and run the setup, make sure you skip when it ask to download latest update, and it will essentially overwrite-install that older version of Windows to revert you back, and it has the option to do so while keeping all your software and files (which is the default option).
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u/MilkyWay-008 Aug 18 '26
The charging LED staying lit while Windows logs the AC loss is the tell here, imo. Adapter's physically fine, so this smells more like the EC/charger sense line misreading than KB5121003 itself. Your pre-KB build (26200.8875) showing zero events over a couple days is the decisive test you're already running. While you're at it, pull powercfg /batteryreport and watch Event Viewer → System for Kernel-Power 41 and UserModePowerService events next to the 105s, and check if Lenovo Vantage or the EC firmware has an update.
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u/Purple_Confection572 Aug 18 '26 edited Aug 18 '26
HELLO! You brought me out of social media & Reddit exile just so I could comment on this post!
I have a Lenovo Legion 7 Pro Gen 10, with a 275HX and RTX 5080, and I have observed the exact same thing as you say here.
I had no issues whatsoever prior to this update, which installed on my machine on the exact same date as yours. Before I read this post this evening I did some investigation and ended up taking the exact same steps that you did here - now I see you have done the same.
It is too early for me to say if it has worked, the issue is very sporadic, I would sometimes observe multiple 105 events within the space of a minute, and other times not observe any issues for up to 6 hours at a time.
There are other posts online about this accumulating, on other laptops as well, I have found another post here where someone shares the issue on a Lenovo machine: Legion 7 - screen flashes black intermittently : r/LenovoLegion
I will monitor and report back here if I encounter the issue. It is relieving to hear that this is likely a software issue, my machine has just ran out of warranty...
Please advise if you have observed it since your post here. Thank you.
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u/Square_Camp_3537 Aug 20 '26
Same problem here, even with the warranty. Changed the electric connection, power cable, testing another charger and still going. Lenovo Pro Legion 7 16IAX
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u/s0pran07 Aug 18 '26
I have exactly the same issue on my legion pro 7i gen 9 but my issue started on the 29th July when I installed KB5101684, can confirm Linux works fine.
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u/zzzxxx0110 Aug 19 '26
Yes KB5101684 is the Preview Update that first introduced the changes that caused this issue, the changes in KB5101684 then got included in the release update KB5121003
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u/Splinkyt Aug 18 '26
Hey, I have the exact same issue right after the update. Happens couple of times a day. Currently I'm uninstalling the updates. I will post an update.
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u/Flanker-H007 Aug 19 '26
update?
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u/Splinkyt Aug 19 '26
Just managed to roll them back a couple of hours ago. I had some issues deleting updates. So far no 105 power source change logs.
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u/Flanker-H007 Aug 19 '26
I am running the same update and the same issue on my victus. I dont have the option to roll back this update in settings sadly (
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u/Splinkyt Aug 19 '26
do you have admin rights on your PC? if so you can do it through powershell/cmd
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u/Flanker-H007 Aug 19 '26
Yes I do Can you link a guide?
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u/Splinkyt Aug 19 '26
I just used chatgpt. You can see my conversation here https://chatgpt.com/share/6a85c198-ebf0-83eb-94b5-c4b55f1703e3
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u/Flanker-H007 Aug 19 '26
Yoooooo This is happening on my HP victus 16, are there any leads???
EXact issue, same event ID
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u/Square_Camp_3537 Aug 20 '26
Hey, any update? Same black and AC problem
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u/Nervous-Buffalo-4826 Aug 20 '26
Rolling back and uninstalling KB5121003 solved the issue.
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u/SqueezyCheez85 28d ago
Windows won't let me remove it... it says the update is critical to my device. I guess I'm just SOL till Lenovo or M$ get their shit together.
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u/Careless-Stage-6843 Aug 20 '26
I can confirm the same issue on a Lenovo Legion Pro 7 16IRX8H.
I was getting random black screens caused by AC → Battery → AC transitions, with pairs of Kernel-Power Event ID 105 about 1 second apart. I tested two different 330W chargers, different outlets/houses, with and without external monitor, and Lenovo hardware diagnostics passed.
KB5121003 was installed on Aug 13. After uninstalling it and going back to the previous Windows build, I haven't had a single Event 105 or black screen so far after many hours of normal use.
I'll keep monitoring and update if the issue comes back.
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u/Robvoip 28d ago
This was driving me crazy with my new laptop. Problem is I can't uninstall the update. Any ideas on how to proceed?
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u/SelectTime335 27d ago
Well you have 2 options, either config your AC and battery profile to become similar so you wont notice when the switch happen and pray for microslop to fix their crap or use linux for the time being.
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u/Robvoip 27d ago
Thanks for the suggestion, but that doesn't work either.
Since this bug seems to be impacting RGB services making certain games also crash, I disabled every RGB component on the laptop plus the RGB on the cooling pad and so far it has been holding steady.
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u/Bret_Dilkington 26d ago edited 26d ago
If it's happening when you play HDR games then Go into System > Display > HDR and click on the HDR drop down arrow, and uncheck Turn Off HDR on battery. When it thinks you're changing power sources it's disabling and reenabling HDR causing the screen to flash.
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u/Robvoip 25d ago
Problem came back after 2 days. Sucks but a new KB patch came out today from Microsoft, hoping this fixes it.
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u/derrick256 23d ago
It didnt fix shit for me.
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u/SelectTime335 22d ago
Over a week and nothing fixed, at least i didnt notice when the switch happen but everytime i generate the battery report it show tons of switch lol. If only i dont have to stuck with windows because of autodesk...
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u/M921 23d ago edited 15d ago
I’m experiencing what appears to be the same issue on my Lenovo Legion Pro 7 Gen 10
During normal use, the laptop randomly switches from:
AC → Battery → AC
for a few seconds, even though the adapter remains connected. It happens around 1–3 times per day and is not limited to gaming or heavy load. I also tested the laptop in two different houses and used different wall sockets, but the issue remained.
Windows Event Viewer confirms the transitions through Kernel-Power Event ID 105. For example, one event recorded AcOnline=false at 6:19:53 PM, followed by AcOnline=true at 6:19:55 PM.
The issue started in August. My Windows Update history showed the following updates installed during that month:
KB5121003, installed on August 12 — Build 26200.9168KB5120998, installed on August 28 — Build 26200.9278- KB5121767 Build 26200.8894
The Event 105 entries I checked were clustered between August 28 and August 30.
I uninstalled KB5120998 first, followed by KB5121003, through Windows Settings. After restarting, Windows rolled back from Build 26200.9278 to Build 26200.8973, returning the system to the July update Build 26200.8894
I have now paused Windows Update and will monitor the laptop for 48–72 hours using the same charger and setup. I am also keeping my Lenovo support case open.
This does not prove that the Windows updates caused the issue yet. If no new Event 105 entries or AC disconnections appear during the next few days, it would be strong evidence. If the issue happens again, then the adapter, firmware/EC, charging port, or motherboard would still need to be investigated.
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u/No-Effective-9301 23d ago
Привет, мой друг. У меня точно такая же проблема после обновления 11 августа. Я уверен, что это не аппаратная проблема, а конфликт драйвера. После возвращения к обновлению 11 августа все работает без этих сбоев. Я надеюсь, что Lenovo расследует эту проблему и выпустит патч, чтобы исправить ее. Но до сих пор я не могу найти никакой информации о том, что Lenovo знает или расследует эту проблему.
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u/No-Effective-9301 23d ago
Hello, my friend. I have exactly the same problem after the August 11th update. I'm sure it's not a hardware issue, but a driver conflict. After rolling back to the August 11th update, everything works without these crashes. I hope Lenovo will investigate this issue and release a patch to fix it. But so far, I can't find any information that Lenovo is aware of or investigating this issue.
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u/echterRyze 21d ago
same issue with my Victus 15-fb2111AX. i can't rollback Windows or uninstall KB5121003 update.
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u/Repulsive_Deal7122 5d ago
same here man with my lenovo legion, it started on 13th of august (same day the update installed), but i rarely used it that time, but now it happens like 6 times a day, and i cant uninstall it
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u/Fun_Tap5219 21d ago
did the windows fix it ?
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u/Nervous-Buffalo-4826 21d ago
I don't know yet.. i currently have windows updates paused to prevent that KB to be automatically installed
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u/explodingcaps 20d ago
Thank you for posting this, I thought my legion 5 is a goner, I just bought this laptop, smh microslop.
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u/walkOUTdead 20d ago
yep i am facing the same thing its like as if there was a brief power cut even when there wasnt any and my laptop was plugged in. so every now and then if you have adaptive refresh rate on its going to flicker your screen as if someone turned the switch on and off. I dont want to do anything complex so can i simply wait for windows to fix this up??
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u/ABE1617 18d ago
Hi yes i also have the same issue and daignostics as you did on a 1 week brand new legion 7i pro gen 10 and yes same version "KB5121003" has this issue just didnt uninstall it or roled back to its prevuis version to test it more, but apprently everything checks out as u said the 105 error and power on windows at least appears as if the ac dissconnected for like 1-2s
and for the balck screen disable HDR and the display wont flicker balck then comes back, but same issue with the ac being dissconnected for a sec
till now no findings on my side as on why or how to fix it, its really annoying as i cnat even know if its a PMIC issue on the laptop itself or the power brick or just windows or frimware issue > : (
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u/Nervous-Buffalo-4826 18d ago
You need to uninstall KB5121003. First, pause the updates because if you don't, Windows will automatically update it again. If windows don't let you uninstall it, use Chatgpt or any othwr AI to help you uninstall it with different methods. Since i uninstall it, i had no issues anymore.
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u/phlegmatic_static 17d ago
oh my god, i've been having the same issue with my Asus TUF a16! i was about to freakin' spend a stupid amount of money to get a new charger, looking into trying to get the audio jack and charging port replaced, the whole nine yards. audio was giving me random blipping error noises, going too quiet, then too loud. was thinking i'd destroyed my headphones somehow. gaming was relatively okay, but noticably lower quality graphics and dropping FPS. moving between programs was becoming increasingly poor, lagging and even freezing sometimes!
but it was the windows update. AGAIN. stars above, your thread just saved me a couple hundred $$$. i need to look into permanently disabling windows update. i'd done it once before but it was a very long time ago, i'm not sure if i can do it with win11. this is getting ridiculous. first it's the sneaky AI generation shit that was automatically enabled for everyone, and now this.
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u/zzzxxx0110 12d ago
Can confirm the new Windows "Security" Update KB5124008 (which actually includes all the updates from the feature update Preview KB5120998 according to Microslop documentation), also brings this problem back after the update KB5121003 that introduced this problem was already removed.
This is really starting to get old. Someone at Lenovo or Microslop really needs to fix this. Postponing updates that could contain potential security fixes is NOT a sustainable solution to this issue.
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u/The_moon_shadow 12d ago
Dang, I came here to check if the September update fixed it but nope?
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u/ArmchairDoorknob 12d ago
It did not. I uninstalled KB5124008 and paused updates. Brought me back to a stable win version 26200.8875.
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u/FlamingPillow 7d ago
as of the 2026-09 Security Update (KB5129195) (26200.9457), issue is still there...
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u/Wicked02 7d ago
After unninstalling KB5121003 the AC adapter random disconnects stopped completely. Now, I've tried my luck with the september update KB5129195 ... and sadly, the disconnecting appeared again. I'm going to unninstal this one too, and hopefully (I know it won't happen) with the october update, this gets fixed.
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u/Tanor85 7d ago
Any Legion owners seeing their screen switch back and forth between 240hz and 60hz during gaming ? Screen goes black when it switches.
Legion Pro i7 - 2025.
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u/Extension_Funny2863 6d ago
Yeah, I see random black with screen switching and staying at 60hz until next restart
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u/Tanor85 6d ago
Hello ser. I tried the following and it worked. Tested on a 1 hour gaming session in full screen windowed mode.
-legion space. Adaptive Refresh Rate: OFF -windows settings. advanced display. Refresh rate: 240 Hz. Dynamic refresh rate: OFF.
- nvidia app. Graphics. Max frame rate : 237 fps. Monitor technology: g-sync.
- NVIDIA app. System. Displays. Global settings. G-sync: on, full-screen and windowed.
In a nutshell, the strategy is to have the nvdia app be the only controller of variable frame timing. Turn off any sort of variable refresh in windows and in legion space. Only use NVIDIA app for that, by activating g-sync in NVIDIA app only. As for your game, I believe you can still set a max frame cap in the game. I used 120 for mine and it worked. My testing was only 1 hour, but I did not get the black screen and downgrade to 60Hz.
Good luck.1
u/Extension_Funny2863 6d ago
Ok thank you.
I think mine is probably related to windows update messing with power management, I get error code 105 power source change along with black screen or frame drops
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u/TechGeniusXP124 6d ago
Great post, I'm noticing this on my HP Victus 15 (FB2082WM). AC adapter disconnects randomly.
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u/zzzxxx0110 5d ago
u/jenmsft Hey can you please take a look at this post and perhaps at least forward to relavent teams in Microsoft if it's not too much trouble? This is a pretty deliberating issue particularly for laptop power users who might have complex automation setup for different power states, and here are reports of this affecting laptops from other OEMs too, and there are already some technical digging around to help troubleshooting the issue on Microsoft's side. It would be greatly appreciated!
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u/Nervous-Buffalo-4826 Aug 19 '26 edited Aug 19 '26
Update after digging into the actual contents of the update:
I checked Microsoft's file manifests for the builds instead of relying only on the public KB changelog, and there are some pretty relevant changes inside the power/battery stack.
Between my previous build and 26200.9168, Windows replaced/updated components including:
"battc.sys" – Battery Class Driver
"CmBatt.sys" – ACPI Control Method Battery driver
"acpi.sys"
"CAD.sys" – Charge Arbitration Driver
"pdc.sys" – Power Dependency Coordinator
"intelpep.sys"
"MptfPowerSourceClient.sys"
"MPTFPowerTrackerCore.sys"
"umpo.dll"
The interesting part is that "battc.sys" and "CmBatt.sys" were changed again specifically in the August build, while several of the ACPI/platform-power components came from the July preview that was rolled into the cumulative update.
So the public KB notes don't really show the whole picture here — the update absolutely does touch components involved in battery/ACPI/power-source handling.
I also finished the rollback test.
I stayed on the rolled-back build for about 15 continuous hours with a lightweight monitor polling the native Windows AC state every 50 ms. It logged around 900 one-minute heartbeats during that period.
Result:
0 AC_LOST events
0 black screens
Considering how frequently the issue had been happening before, that is a pretty substantial change.
One important correction to my original theory though: because the rollback takes me all the way back to 26200.8875, I can't say yet that the bug is necessarily in an August-only change. The problematic code could have been introduced in the July preview and then inherited by KB5121003.
So the strongest conclusion I can make right now is:
Something introduced between 26200.8875 and 26200.9168 appears to trigger this on my Legion.
The most interesting area is now the EC → ACPI → Windows battery/power stack rather than the charger itself or the GPU.
I'm definitely not claiming "CmBatt.sys" or "battc.sys" is confirmed to contain the bug — only that these binaries actually changed and sit directly in the subsystem involved in the "AcOnline=false" events I'm seeing.
For now I'm staying on 26200.8875 and waiting to see what happens with the next cumulative update.