Celeste Launcher 3.18.0 crashes on Verify - missing System.Configuration.ConfigurationManager.dll

JohnnyVCC83

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Jun 16, 2026
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Hi everyone,

I’m on Windows 11 Pro and I have a clean install of Project Celeste / AoEO. I already tried reinstalling everything twice, after installing the required prerequisites (.NET Framework 3.5, Visual C++ 2015-2022 x86/x64, WebView2 Runtime, DirectX June 2010). The launcher still crashes when I click “Verify” on the registration page.

What happens:
- I enter my email
- click Verify
- the button becomes greyed out
- after a few seconds the launcher closes by itself

Event Viewer shows:
- Application: Celeste Launcher.exe
- Exception: System.IO.FileNotFoundException
- Missing assembly: System.Configuration.ConfigurationManager, Version=4.0.0.0
- Stack trace points to:
Celeste_Public_Api.Logging.LogHelper.GetLogFilePath()
Celeste_Launcher_Gui.Pages.RegisterPage.OnVerifyEmail()

I also checked the launcher folder under:
C:\Users\Giovanni\AppData\Roaming\ProjectCeleste

and confirmed that System.Configuration.ConfigurationManager.dll is not present anywhere in the launcher directory.

Logs also show:
- Attempting to connect to wss://prod.projectceleste.com:4513/
- Server Offline!
- but the actual crash seems to be the missing assembly above, not the websocket timeout.

Questions:
1) Is this a known issue with launcher 3.18.0?
2) Is there a supported workaround, such as manually adding the missing DLL?
3) Should that DLL be included in the launcher package, or am I missing a required file?

If needed I can attach the full launcher log and the Event Viewer stack trace.
 
Update:

I manually copied System.Configuration.ConfigurationManager.dll from the latest NuGet package.

The error changed from:

FileNotFoundException

to:

FileLoadException
"The located assembly's manifest definition does not match the assembly reference" (0x80131040)

This suggests the launcher is missing the DLL but expects a specific older version.