Why does my laptop sleep anyway despite my screen and sleep settings being set to never?

Your screenshot confirms Windows 11 Pro 25H2, build 26200.9168, but it doesn’t show which sleep mode the laptop uses. The strongest clue is still that the problem happens exactly at your screen-off timeout.

Try these two checks first:

1. Temporarily set the screen timeout to Never as well. Leave the lid open and wait longer than five minutes. If the problem stops, it’s linked to the display turning off rather than a separate sleep timer. A black screen or a sign-in screen on return doesn’t, by itself, prove the laptop slept.
2. Check the supported sleep mode. Open Terminal and run:

   powercfg /a

   If it lists Standby (S0 Low Power Idle) as available, the laptop uses Modern Standby. If it lists Standby (S3) instead, it uses traditional sleep. That distinction matters before changing any further settings.

If it uses S3, check Control Panel > Power Options > Change plan settings > Change advanced power settings > Sleep. Verify both Sleep after and Hibernate after for battery and plugged-in operation.

If it uses Modern Standby, run this in Command Prompt as administrator after reproducing the problem:

powercfg /sleepstudy /output "%PUBLIC%\sleepstudy.html"

Open the generated report to check whether the matching period was screen-off time or actual sleep. If it really is sleeping despite your settings, check Lenovo’s model-specific power-management drivers and BIOS release notes for relevant fixes.

There’s no reason to reinstall Windows or force a different sleep mode through registry edits based on this screenshot. First establish what happens at that three- or five-minute mark.