This is a bug report for the Steam Link app for Android regarding using a mouse specifically.

TL;DR version:

• The rendered mouse lags horribly on the Android client device, despite me being able to see it continue to move smoothly on the host PC
  
• Streaming to the Android app is perfectly fine, aside from the mouse behavior
  
• Happens with both a Bluetooth mouse paired to the Android client and with a mouse connected into the host PC.
  
• Happens even in the Big Picture menus, not just in games.
  
• Reproduced on multiple different Android devices.
  
• Does not happen when streaming to Steam Link/Remote Play running on a non-Android device, such as the old Steam Link hardware, an iPad, or a laptop.
  
• While the mouse is lagging, everything else (display, keyboard, controller) continues to perform perfectly smooth, which tends to suggest it is not a question of the network-related throughput/latency issues that people have with game streaming.

When I use the Android to play games that use a mouse (mouse connected to host PC, not to the client device running the Steam Link app), the streamed mouse cursor is horrifically laggy, despite working smoothly as usual on the host PC.

This has been reproduced on multiple Android devices running the Steam Link Android app (a TV (running Android TV as its main OS) via ethernet, an Nvidia Shield (Android TV) via ethernet, a Samsung Galaxy S21 phone), and all experience the same issue. Streaming to other non-Android devices (such as a laptop on wifi) do not have this mouse issue.

In Doom Eternal, even over wifi, I'm getting 15 ms of display latency according to the debug graph overlay, at full 60 FPS. Not a network issue. Not an input latency issue, keyboard and controller inputs are perfectly fine. Seems to be specifically about how the Steam Link app on Android renders the remote mouse cursor.