Temporary delays occur at regular intervals for all inputs on Linux.

[MIYUKINNGU]

Type

Other

Bug description

While osu!lazer is running, all input occasionally becomes delayed for a brief moment. This affects both keyboard and mouse input simultaneously.

The issue occurs approximately once every few seconds and appears to happen at a very regular interval. It occurs consistently regardless of where in osu!lazer I am, including menus and gameplay, and is not limited to any specific game mode, beatmap, or screen.

The issue started around the end of August 2026 after an update.

My current environment is CachyOS with KDE Plasma on Wayland. I have only confirmed the issue in this environment.

Screenshots or videos

2026-09-21.19-22-45.mp4

Version

2026.921.0-lazer

Logs

compressed-logs.zip

[ThePyrotechnic]

I can reproduce this on my system, and I have bisected this to ppy/osu-framework@2a44111
... which is ultimately a diff in the SDL3-CS bindings. I bisected that to ppy/SDL3-CS@dfd7d86.
This commit updated the object files, so I'm fairly certain that rules out any ppy code.
Running strings native/linux-x64/libSDL3.so | rg '^SDL-.+$' in the revisions returns the underlying SDL3 versions:
Bad: SDL-3.5.0-0bb5393
Good: SDL-3.5.0-f31ca02
... which covers over 200 commits in SDL3. I will try to bisect these as well, in a couple hours :)
@smoogipoo - pinging you for visibility only because the object file update was yours

[ThePyrotechnic]

Following the above info: libsdl-org/SDL@18fc4d9 is the offending commit
This can be confirmed by building the bad commit and the prior commit (libsdl-org/SDL@36f6218). Override the SDL library loaded by Osu and the bug will appear/disappear (drop the built .so into osu/osu.Desktop/bin/Debug/net10.0/runtimes/linux-x64/native/, use LD_LIBRARY_PATH, etc.)

[ThePyrotechnic]

A final update - the offending commit in the SDL USB handling code slightly alters the checks performed when a device is connected.

What this means for us: in order for the "bad" SDL code to run, a device must be getting plugged in. In my case, I checked dmesg --follow and discovered that my motherboard's bluetooth hardware was constantly crashing and re-initializing, thus triggering the code. Once i disabled the bluetooth module the hitching stopped in Osu.

I'd still consider this a regression in SDL since there's probably a blocking check in that new code which shouldn't be there, but the bad behavior requires a faulty system (unless there exists some legitimate USB device which constantly re-initializes itself).

@MIYUKINNGU, check dmesg --follow to see if you have any USB devices failing in a loop. If you can't find anything, try unplugging everything except the input device(s) you use for Osu.

[MIYUKINNGU]

Thank you. My Bluetooth hardware was also constantly crashing and reinitializing in a similar way. The issue was resolved after I disabled the device.

[ThePyrotechnic]

After some A/B testing on the libsdl code, I've opened an issue there: libsdl-org/SDL#16383