Steam Beta Branch: Stable Client
Steam Version: 1773099986
Steam Client Build Date: Mon, Mar 9, 2026 16:19 UTC -08:00
Steam Web Build Date: Mon, Mar 9, 2026 16:36 UTC -08:00
Steam API Version: SteamClient023

Distribution: Slackware x86_64-current (any linux has this issue)

Have you checked for system updates?: Yes

Please describe your issue in as much detail as possible:

When you choose a TARGET and "START IN" for launcher properties the paths do not take into account normal characters like space and parenthesis.
You can browse down directory paths normally choose your files and they will populate in the appropriate input text area.

However, a large number of these paths will include spaces and/or parenthesis, due to windows installation paths. So attempting to use what the browser drops into the textarea without modification will always fail.

Example:
/home/user/.local/share/Steam/steamapps/compatdata/3411257090/pfx/drive_c/Program Files (x86)/Battle.net/Battle.net Launcher.exe

Results in a log entry:
[2026-03-10 10:26:20] /bin/sh: -c: line 1: `/home/user/.local/share/Steam/ubuntu12_32/steam-launch-wrapper -- /home/user/.local/share/Steam/ubuntu12_32/reaper SteamLaunch AppId=3411257090 -- '/home/user/.local/share/Steam/steamapps/common/SteamLinuxRuntime_sniper'/_v2-entry-point --verb=waitforexitandrun -- '/home/user/.local/share/Steam/steamapps/common/Proton - Experimental'/proton waitforexitandrun /home/user/.local/share/Steam/steamapps/compatdata/3411257090/pfx/drive_c/Program Files (x86)/Battle.net/Battle.net Launcher.exe'

With the apparent result of the launched application not loading with no errors other than the logs.

All nix users know paths like this require quoting to deal with non a-z0-9 characters, it's generally assumed by users if you use a file browser to pick an object it will know how to navigate back to it properly once selected.
Either the file browser (browse button) should automatically add " " to everything (safest option), parse the string to see if it contains: space"{}'%$!`~ and then add quotes (problematic if parser is not done right), or leave the text as-is and add quotes to the execution side (path for cd and launch) (will need to check for quotes prior to doing this)

While most of us know to use the quotes when something like this pops up, new users switching to linux will not be able to find the logs, figure out what went wrong, or understand what the problem is.

I'd be willing to write the patch/update for you if you limited down the search area for it (there is a lot of code in the repo).

Steps for reproducing this issue:

1. Open the launcher
2. Add non-steam game
3. Click "browse" for the target
4. Select a "normal" path for an executable that includes space or parenthesis.Ex: home/user/.local/share/Steam/steamapps/compatdata/3411257090/pfx/drive_c/Program Files (x86)/Battle.net/Battle.net Launcher.exe
5. Attempt to launch the newly created object from the main launcher