[BUG] Claude Desktop (Windows MSIX): cursor stutter/lag when moving mouse over app window on multi-GPU systems

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

This is a Claude Desktop (Windows) report, not a CLI bug. Filing here as it is the only public Anthropic tracker; please route to the Desktop team.

On Claude Desktop for Windows (Microsoft Store/MSIX, v1.12603.1), moving the mouse cursor over the Claude window causes a brief stutter/lag that resolves, then recurs as the cursor keeps moving. The claude.ai web app in Chrome on the same machine is completely unaffected (verified: 1,449 pointermove events, zero long tasks).

Hardware: Windows 11, AMD Ryzen with integrated Radeon + NVIDIA RTX 4070 (display on the dGPU), 3840x1600 @ 144 Hz.

This matches the known Electron GPU-compositing + DWM interaction on dual-GPU Windows systems. Prior reports #45127 and #56805 described the same symptom/hardware but were closed as invalid (filed as Claude Code issues).

Confirmed fix on this machine: adding "isHardwareAccelerationDisabled": true to %APPDATA%\Claude\claude_desktop_config.json and restarting. After restart the GPU process runs with --use-angle=d3d11-warp-webgl (software rendering) and the stutter is fully gone, with modest CPU cost (~17% of one core under a synthetic 1200 Hz cursor sweep).

What Should Happen?

Smooth cursor movement over the window with hardware acceleration enabled.

Suggested fixes (the app already ships the mechanism):

1. Auto-detect multi-GPU configurations and fall back to software compositing, or
2. Surface the existing hidden "Disable Hardware Acceleration" menu toggle in Settings so affected users can find it.

Error Messages/Logs

Steps to Reproduce

1. Windows 11 desktop with hybrid GPUs (integrated AMD Radeon + discrete NVIDIA RTX 4070, display on the dGPU).
2. Install Claude Desktop from the Microsoft Store (v1.12603.1).
3. Open the app and move the mouse cursor around inside the window.
4. Observe brief stutter/lag that resolves and recurs while the cursor keeps moving.
5. Add "isHardwareAccelerationDisabled": true to %APPDATA%\Claude\claude_desktop_config.json, restart the app -> stutter is gone.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude Desktop 1.12603.1 (Microsoft Store) - desktop app, not CLI

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

Diagnostics performed before the fix: app processes and DWM showed no CPU/GPU saturation under synthetic cursor sweeps; the GPU process ran on the correct adapter (RTX 4070, luid 0xe845); main-process UI thread answered WM_NULL probes in <10 ms. The stutter mechanism is in the compositing path, consistent with #56805's analysis (--disable-gpu-compositing also reportedly resolves it).

Related closed issues: #45127, #56805.

Investigated and filed with Claude Code on behalf of the user.