UI sluggish on Ubuntu/Wayland

Start by reproducing the idle chat and Settings cases while observing WebKitWebProcess CPU usage and thread-level sampling. Inspect the AppImage startup hook and its GDK_BACKEND handling, then compare the resulting environment with the tested WebKit variables. Done means idle views no longer saturate a CPU core and Settings remains responsive on Ubuntu 24.04 Wayland.

On Ubuntu 24.04, the Copilot Desktop UI is consistently sluggish and becomes extremely sluggish when opening Settings. Other desktop applications on the same system—including Brave, IntelliJ IDEA, Teams, and Slack—remain responsive.

Environment

• Copilot Desktop 1.0.84-5 AppImage

• Ubuntu 24.04, GNOME 46, Wayland

• Kernel 6.17.0-35-generic

• Hybrid Intel Arrow Lake-P graphics and NVIDIA GeForce RTX 5070 Laptop GPU

• NVIDIA driver 595.71.05

• UI text scaling: 1.75

• 32 GB RAM with no meaningful swap pressure

Reproduction

1. Start Copilot Desktop and open any chat.

2. Leave the window untouched.

3. Observe WebKitWebProcess CPU usage.

4. Open Settings and leave it untouched.

Observed behavior

• In an untouched chat, WebKitWebProcess uses approximately 59–93% of one logical CPU core.

• Opening Settings raises usage to a sustained 98–106% of one logical core, without further interaction.

• Thread-level sampling shows that almost all CPU usage occurs on the main WebKitWebProcess thread.

• The process also produces roughly 60,000–85,000 minor page faults per second, with RSS fluctuating by tens of megabytes.

• Scrolling makes the UI visibly sluggish.

Additional findings

• The AppImage startup hook unconditionally sets GDK_BACKEND=x11, so the application runs through XWayland despite the Wayland desktop session.

• Supplying GDK_BACKEND=wayland externally does not override this because the bundled hook replaces it.

• Testing DRI_PRIME=0, WEBKIT_DISABLE_DMABUF_RENDERER=1, and WEBKIT_DISABLE_COMPOSITING_MODE=1 did not resolve the issue. Some of these environment variables appeared to be absent from the resulting WebKit process.

• No GPU crashes, system memory pressure, or significant swap activity were observed.

Expected behavior

An idle chat or Settings page should not continuously saturate a CPU core, and opening Settings should remain responsive.