MacBook Air M4 severe battery drain, performance issues

Need advice regarding severe battery drain and performance issues on a relatively new MacBook Air M4.

Device:

MacBook Air 15 inch M4

16 GB RAM

macOS Tahoe 26.4.1

Battery health: 98%

AppleCare+ active

Previously I used to get around 14 to 15 hours battery life even with heavy usage including Safari tabs, VS Code, YouTube, Office apps, music/video playback, and MATLAB.

Now battery drains extremely fast even under very light use. Around 1% drop every few minutes. Current usage is usually just a few Safari tabs and one YouTube video.

Other symptoms:

• Frequent beachball freezes

• Dark screen/delay during login

• UI lag and occasional unresponsiveness

• Battery percentage behaving inconsistently after restart once

• Battery estimate showing only around 3.5 hours remaining at 72% charge

Diagnostics/checks already done:

• Battery health still 98%

• No physical damage

• Around 200 GB free storage remaining

• Memory pressure normal

• Swap usage 0 bytes

• Background apps/processes disabled

• Spotlight indexing normal

pmset logs show repeated wake/assertion activity and sleep prevention behavior.

Has anyone experienced similar issues after recent macOS Tahoe updates on Apple Silicon Macs, especially M4 Air models?

Trying to understand whether this looks more like:

• macOS/power management bug

• firmware issue

• wake/sleep loop

• battery controller problem

• or actual hardware defect

Any suggestions before escalating fully through AppleCare+ would help.