[Problem/Bug]: WebView2 Runtime 142: Significant rendering performance degradation for canvas elements at 4K resolution and above

What happened?

After updating to WebView2 Runtime 142, our application using stacked canvas layers (WebGL → 2D → 2D) experiences severe rendering performance degradation. The issue occurs only at canvas widths ≥ 3840px (e.g., 3840×2160, 3840×1440), where FPS drops from ~160 (Runtime 141) to ~50. DOM rendering also becomes noticeably stuttering. The problem persists across OS reinstall, driver reinstall, and code rollback. Downgrading to Runtime 141 resolves it immediately; upgrading back to 142 reproduces the issue.

Due to project constraints, browser testing isn't feasible.

Importance

Important. My app's user experience is significantly compromised.

Runtime Channel

Stable release (WebView2 Runtime)

Runtime Version

142.0.3595.65

SDK Version

No response

Framework

Other

Operating System

Windows 11

OS Version

10.0.26100

Repro steps

1. Use a desktop app with three stacked canvases of the same size: WebGL layer → 2D layer → 2D layer (e.g., 3840×2160).
2. Run on Windows 11 (24H2/25H2) with WebView2 Runtime 142.
3. Test at different resolutions:
   • 3840×2160 → FPS drops to ~55
   • 3840×1440 → FPS drops to ~55
   • 3200×1800 → FPS remains stable (~160)
4. Downgrade to WebView2 Runtime 141 → performance returns to normal.

Repros in Edge Browser

No, issue does not reproduce in the corresponding Edge version

Regression

Regression in newer Runtime

Last working version (if regression)

Runtime 141