Quick update after additional retesting: this finding is confirmed.
xpad is loaded and an extra Microsoft X-Box 360 pad input device appears.valvecontrollermanager.cpp (3059): We didn't think 4 was a connected controller?KeyValues ... controller_mappings ... missing {CSteamEngine::BMainLoop appears to have stalled > 15 seconds and fatal stalled cross-thread pipe.xpad (sudo modprobe -r xpad), Diablo IV launches correctly with Steam Controller (retested again just now).xpad also removes detection of my Xbox-compatible fightpad/arcade stick, so this is only a workaround.xpad loaded by default.This points to a Steam controller/device-enumeration conflict when xpad-backed devices are present, rather than a Diablo IV-specific issue.
I'm having this same issue with steam crashing when trying to launch games. for me it isn't just a set of games - it's all games. no games work when i have the steam controller (or puck) plugged in. It's pretty frustrating. I've tried the beta client and the non-beta client.
I've attached a report of what I hope are the most useful files. I have installed the hidapi libraries and the udev rules. These only made it possible to update the firmware on the devices. They crashed in game before and after those were installed.
Any help on this would be greatly appreciated.
For me it was also on more than one game, but at that time I was testing mostly with d4.
I did find a fix on my system removing the xpad entry. Although I am not totally convinced that was it. I will do more testing later.
This can also manifest with an out of memory error, seems like - I got them multiple times (not as often as stalls).
Adding some output lines, if only to aid others also having this issue:
***** OUT OF MEMORY! attempted allocation size: 65 ****
src/tier0/threadtools.cpp (3098) : Failed to set thread local value
src/tier0/threadtools.cpp (3098) : Failed to set thread local value
cannot allocate memory for thread-local data: ABORT
(did not produce crash id)
src/clientdll/steamengine.cpp (2843) : Assertion Failed: CSteamEngine::BMainLoop appears to have stalled > 15 seconds without event signalled
assert_20260823171948_130.dmp[360494]: response: CrashID=bp-730198e4-f7cb-4bf4-b339-267e52260823
[xcb] Unknown sequence number while processing queue
[xcb] You called XInitThreads, this is not your fault
[xcb] Aborting, sorry about that.
steam: xcb_io.c:287: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.
crash_20260823174152_49.dmp[410386]: response: CrashID=bp-c0ae7fcf-18d3-4df3-9761-68c922260823
Happening on NixOS unstable (updated Aug 18, rev 0ae2bc1419c3f345984c2629e72e7a631820fa4d), default kernel, on Hyprland (Wayland). My system setup is public, although convoluted/unreadable.
Happened on Steins;Gate, proton experimental
I had similar issues previously where some games (notably Persona 5 Golden) would crash (or steam would crash in background after launch), if steam saw my Wooting One keyboard connected, as it also exposes an Xinput controller.
proton experimentalx1 2026-08
Your system information
• Steam client version (build number or date): 1778281814 (build date: May 8 2026 22:40:45, SteamClient023)
• Distribution (e.g. Ubuntu): NixOS 25.11 (Xantusia), build 25.11.20260511.5cb5ee2, kernel 7.0.3-zen1
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes
• Steam Logs: /home/tim/steam-bugreport-controller-crash-20260511-222018.tar.gz
• GPU: AMD (Radeon RX 7900 XTX, RADV NAVI31 / Mesa RADV 25.2.6)
Please describe your issue in as much detail as possible:
Expected behavior: Steam should stay running and launch games normally when a controller is enabled.
Actual behavior: Steam segfaults/crashes immediately on game launch when controller is enabled.
This is reproducible with Diablo IV (AppID 2344520) and also occurs with other games (not Diablo IV-only).
If controller is off/disconnected, Diablo IV launches and runs normally.
I already did a full local Steam reset and forced a full client redownload/rebuild; crash still persists with controller-enabled launch.
Observed crash evidence includes:
• Segmentation fault (core dumped) from Steam launch script
• coredump signal 11/SEGV
• CrashID: bp-7e50b428-6f84-4a1d-902c-4a5e22260511
Steps for reproducing this issue:
Control case:
Additional information (missing from template but relevant)
• Desktop/session stack at repro time:
◦ XDG_CURRENT_DESKTOP=Hyprland
◦ XDG_SESSION_DESKTOP=Hyprland
◦ XDG_SESSION_TYPE=wayland
◦ WAYLAND_DISPLAY=wayland-1
◦ DISPLAY=:0
◦ Xwayland active
◦ login/display service: ly
• CPU: AMD Ryzen 9 9950X 16-Core Processor
• Controller seen in logs: Steam Controller (wireless), serial FXA9954701C8C
• Crash evidence:
◦ Segmentation fault (core dumped) from Steam launch script
◦ journal/coredump shows signal 11/SEGV
◦ backtrace references steamclient.so and steamui.so
◦ CrashID: bp-7e50b428-6f84-4a1d-902c-4a5e22260511
• Already tested/ruled out local corruption:
◦ Performed full local Steam reset (config/userdata/controller_base/appcache/package/logs/steamui)
◦ Steam then forced full client redownload/rebuild (~487664 KB)
◦ Crash still reproduces immediately with controller-enabled launch
Can supply full packaged evidence.