Steam client version: 1781041600
Distribution: Ubuntu 25.10
Opted into Steam client beta?: Yes (also reproduces on stable)
Have you checked for system updates?: Yes
Steam Logs: steam-logs.tar.gz
GPU: AMD RX 7800xt
Compositor/DE: Niri (Wayland)

Expected: steamwebhelper should idle at a reasonable CPU usage when the Store front page is open and no interaction is occurring.

Actual: The steamwebhelper zygote process (--type=zygote) consumes ~90-95% of one CPU core continuously while the Store front page is open, specifically when the "Explore Your Discovery Queue" banner (rotating game-art carousel) is visible or near-visible in the viewport.

strace on the zygote process shows it repeatedly writing \x01\x00\x00\x00\x00\x00\x00\x00 to an eventfd in a tight loop, consistent with a CEF/Chromium task being continuously reposted in the message loop (busy-wait), rather than the event loop idling normally.

Additional observations:

• Running with -disable-gpu reduces CPU usage from ~94% to ~36%, but does not eliminate it - the eventfd loop continues at a lower rate.
• Reproduces on both the native Steam package and the Flatpak (com.valvesoftware.Steam) build.
• Reproduces on both stable and beta client channels.
• Scrolling/resizing so the Discovery Queue banner is out of the viewport, or navigating away from the Store front page entirely, returns CPU usage to normal immediately.

Steps for reproducing this issue:

1. Open Steam and navigate to the Store front page.
2. Observe steamwebhelper CPU usage in htop/top (~90-95% on one core, even when idle).
3. Scroll the page so the "Explore Your Discovery Queue" banner is no longer in or near the viewport - CPU usage drops to normal.
4. Scroll back so the banner is visible again - CPU usage spikes back to ~90-95%.