steam://run/<id>//<args>/ breaks on long arguments

[Zetym]

Your system information

• Steam client version: Built May 15 2020 at 18:18:24
• Distribution: Ubuntu 20.04 LTS
• Opted into Steam client beta?: Yes
• Have you checked for system updates?: Yes

Please describe your issue in as much detail as possible:

Trying to start Arma 3 through the steam steam://run in order to start it with proton and still supply mods through launch parameters, I got it working with the two mods I used for testing. Sending the command opened a dialog from Steam asking if I wanted to run with the extra parameters. I could also see activity relating to the extra parameters in steam -console in preparation for the dialog.
Adding more mods after that stopped everything from working. I didn't get the dialog asking if I acknowledged the extra parameters, and steam -console didn't show any response to the command. In the terminal sending the command the output looked the same as it did when it worked.
Reverting back to the two mods I had tested with earlier netted the same result now as with the larger mod list, prompting no reaction from Steam and no activity in steam -console. Restarting Steam enables the shorter mod list to work again.

Steps for reproducing this issue:

1. Run steam steam://run/107410//%22-mod%3dZ%3a%2fmedia%2fdata%2fSteamLibrary%2fsteamapps%2fcommon%2fArma%203%2f%5c%21a3sync%2f%40ace%3b%22%20%22-mod%3dZ%3a%2fmedia%2fdata%2fSteamLibrary%2fsteamapps%2fcommon%2fArma%203%2f%5c%21a3sync%2f%40CBA_A3%3b%22/
2. See activity in steam -console as well as notice the dialog asking if you want to run with the extra parameters. Regardless of the answer, the command has the same result executing it again.
3. Run steam steam://run/107410//%22-mod%3dZ%3a%2fmedia%2fdata%2fSteamLibrary%2fsteamapps%2fcommon%2fArma%203%2f%5c%21a3sync%2f%40ace%3b%22%20%22-mod%3dZ%3a%2fmedia%2fdata%2fSteamLibrary%2fsteamapps%2fcommon%2fArma%203%2f%5c%21a3sync%2f%40CBA_A3%3b%22%20%22-mod%3dZ%3a%2fmedia%2fdata%2fSteamLibrary%2fsteamapps%2fcommon%2f%20rma%203%2f%5c%21a3sync%2f%40acex%3b%22%20%22-mod%3dZ%3a%2fmedia%2fdata%2fSteamLibrary%2fsteamapps%2fcommon%2fArma%203%2f%5c%21a3sync%2f%40AdvancedRappelling%3b%22%20%22-mod%3dZ%3a%2fmedia%2fdata%2fSteamLibrary%2fsteamapps%2fcommon%2fArma%203%2f%5c%21a3sync%2f%40AdvancedSlingLoading%3b%22%20%22-mod%3dZ%3a%2fmedia%2fdata%2fSteamLibrary%2fsteamapps%2fcommon%2fArma%203%2f%5c%21a3sync%2f%40AdvancedTowing%3b%22%20%22-mod%3dZ%3a%2fmedia%2fdata%2fSteamLibrary%2fsteamapps%2fcommon%2fArma%203%2f%5c%21a3sync%2f%40AdvancedUrbanRappelling%3b%22%20%22-mod%3dZ%3a%2fmedia%2fdata%2fSteamLibrary%2fsteamapps%2fcommon%2fArma%203%2f%5c%21a3sync%2f%40C2%20-%20Command%20And%20Control%3b%22/
4. Notice that there's no activity in steam -console, and the dialog doesn't show.
5. Run the command in 1. again and notice there's no activity in steam -console and the dialog doesn't show.
6. Restarting Steam allows the command in 1. to work again, but not the command in 3.

[kisak-valve]

Hello @Zetym, revisiting this issue report, and it's already being tracked at #5753. Closing in favor of the older issue report.