Proton games may freeze during startup if the system file descriptor limit is too low (e.g. 4096), without a clear user-facing error.
The issue became apparent after upgrading from kernel 6.12 to newer kernels (6.18+ / 7.x).
On kernel 6.12, the same games appeared to work with the default file descriptor limit (4096), while on newer kernels they consistently froze.
Newer kernels and/or Proton versions may use more file descriptors during startup, making the low limit more likely to trigger this issue
Details
On a system with:
File descriptor limit: 4096 (ulimit -n)
Proton Experimental
Modern kernel (6.18+ / 7.x)
Affected games (examples):
Avatar: Frontiers of Pandora
The Sims 2 Legacy Collection
Symptoms
Game freezes during startup
No crash dialog
No clear error message
Looks like a kernel / ntsync / Proton issue
Logs
Proton logs include:
WARNING: Low file descriptor limit: 4096
However, this warning can be easy to miss and does not indicate severity.
Resolution
Increasing the file descriptor limit resolves the issue completely:
ulimit -n 1048576
After doing this:
Games launch normally
No freezing occurs
Suggestion
I think it would be good to show a visual warning that could signal the user of that problem and some documentation, this would help users avoid misdiagnosing the problem as a Proton or kernel bug.
Summary
Proton games may freeze during startup if the system file descriptor limit is too low (e.g. 4096), without a clear user-facing error.
The issue became apparent after upgrading from kernel 6.12 to newer kernels (6.18+ / 7.x).
On kernel 6.12, the same games appeared to work with the default file descriptor limit (4096), while on newer kernels they consistently froze.
Newer kernels and/or Proton versions may use more file descriptors during startup, making the low limit more likely to trigger this issue
Details
On a system with:
ulimit -n)Affected games (examples):
Symptoms
Logs
Proton logs include:
WARNING: Low file descriptor limit: 4096
However, this warning can be easy to miss and does not indicate severity.
Resolution
Increasing the file descriptor limit resolves the issue completely:
ulimit -n 1048576
After doing this:
Suggestion
I think it would be good to show a visual warning that could signal the user of that problem and some documentation, this would help users avoid misdiagnosing the problem as a Proton or kernel bug.