Command line arguments inherited by BrowserSubprocess in CefSharp 143.0.90

[mteneglio]

Is there an existing issue for this?

• I have searched both open/closed issues, no issue already exists.

CefSharp Version

143.0.90

Operating System

Windows 11

Architecture

x86

.Net Version

.NET 4.8

Implementation

WinForms

Reproduction Steps

Description

The command line arguments from the main application process are being inherited by the CefSharp.BrowserSubprocess.exe subprocess, causing it to fail with "Invalid command-line arguments" error.

Steps to Reproduce

1. Launch the application with command line arguments (e.g., -p "C:\path\to\file.json")
2. Initialize CefSharp with Cef.Initialize()
3. The subprocess CefSharp.BrowserSubprocess.exe receives the main process arguments and fails

Code Example

var settings = new CefSettings
{
    BrowserSubprocessPath = @"C:\path\to\CefSharp.BrowserSubprocess.exe",
    CachePath = @"%localappdata%\MyApp\Cache",
    LogSeverity = LogSeverity.Info
};

settings.CefCommandLineArgs.Add("no-proxy-server", "1");

bool result = Cef.Initialize(settings, performDependencyCheck: true, browserProcessHandler: null);

Command Line Arguments Passed to Subprocess

When the main application is launched with: MyApp.exe -p "C:\path\to\Host.Json"

The subprocess receives:

--browser-subprocess-path=C:\path\to\CefSharp.BrowserSubprocess.exe
--no-sandbox
--lang=en-US
--log-file=C:\path\to\debug.log
--log-severity=info
--disable-features=EnableHangWatcher,GlicActorUi,LensOverlay
--disable-chrome-login-prompt
--hide-crash-restore-bubble
--disable-back-forward-cache
--no-proxy-server=1
--flag-switches-begin
--flag-switches-end
--do-not-de-elevate
-p
c:\path\to\Host.Json

The -p and file path arguments should NOT be passed to the subprocess.

Workaround Attempted

• Setting BrowserSubprocessPath to an absolute path
• Ensuring all CEF runtime files are present
• Verifying CefSettings configuration

Additional Information

• All CEF runtime files are present in the output directory
• The log file is empty (no CEF initialization errors logged)
• Cef.IsInitialized returns null before initialization and should become true after successful initialization
• This appears to be a regression or bug introduced in version 143.0.90

Related Issues

• Similar initialization issues: Invalid file descriptor to ICU data received. #4163, OffScreen - Browser fails to complete loading when CEF is initialized shortly before the browser is created #3850
• Command line arguments discussion: Example code/documentation for CefCommandLineArgs usage is misleading #2858

Expected behavior

Expected Behavior

The browser subprocess should only receive CEF-specific command line arguments, not the main application's command line arguments.

Actual behavior

Actual Behavior

The subprocess receives all command line arguments from the main process, including application-specific arguments like -p "Host.Json", which causes the subprocess to fail with:

Invalid command-line arguments: '-p --browser-subprocess-path=... --no-sandbox ... c:\path\to\Host.Json'

Root Cause

The issue occurs in BrowserSubprocessExecutable.h (line 64) where the subprocess calls Environment::GetCommandLineArgs(), which retrieves ALL command line arguments from the main process, not just CEF-specific ones. The CommandLineArgsDisabled property only prevents configuration via CEF settings, but doesn't prevent the subprocess from reading the main process arguments.

Note: This line (Environment::GetCommandLineArgs()) existed in version 107.1.40 but didn't cause issues because:

• The subprocess used WcfBrowserSubprocessExecutable with Program.Main(string[] args) which received arguments explicitly
• The subprocess was launched as a separate process with explicit arguments, not inheriting from the parent
• In version 143.0.90, the subprocess now uses BrowserSubprocessExecutable and appears to inherit command-line arguments from the parent process, causing this regression

Workaround Attempted

• Setting BrowserSubprocessPath to an absolute path
• Setting CommandLineArgsDisabled = true in CefSettings (doesn't solve the issue)
• Ensuring all CEF runtime files are present
• Verifying CefSettings configuration

Additional Information

• All CEF runtime files are present in the output directory
• The log file is empty (no CEF initialization errors logged)
• Cef.IsInitialized returns null before initialization and should become true after successful initialization
• This appears to be a regression introduced in version 143.0.90. The same code (Environment::GetCommandLineArgs()) existed in version 107.1.40 but didn't cause issues due to different subprocess launch mechanism (WCF vs non-WCF, explicit arguments vs inherited arguments)
• The subprocess should filter command line arguments and only accept CEF-specific ones
• Source code location: packages/CefSharp.Common.143.0.90/src/CefSharp.BrowserSubprocess.Core/BrowserSubprocessExecutable.h line 64 uses Environment::GetCommandLineArgs() which retrieves all arguments from the main process

Regression?

No response

Known Workarounds

No response

Does this problem also occur in the CEF Sample Application

Yes using WPF/OffScreen command line args

Other information

No response

[amaitland]

When the main application is launched with: MyApp.exe -p "C:\path\to\Host.Json"

If you use --p does it behave differently? From a Chromium point of view it's expecting -- not - for command line arguments.

The browser subprocess should only receive CEF-specific command line arguments, not the main application's command line arguments.

This may not be the Chromium expected behavior.

The issue occurs in BrowserSubprocessExecutable.h (line 64) where the subprocess calls Environment::GetCommandLineArgs(), which retrieves ALL command line arguments from the main process, not just CEF-specific ones. The CommandLineArgsDisabled property only prevents configuration via CEF settings, but doesn't prevent the subprocess from reading the main process arguments.

I don't believe the analysis here is correct. The browser subprocess is an entirely separate process, it's whatever command line arguments were passed to it.

Chromium launches the sub processes, it's not something that CefSharp has direct control over. This is likely a change in upstream behavior and not something that can be changed in CefSharp.

• Setting CommandLineArgsDisabled = true in CefSettings (doesn't solve the issue)

Likely an upstream bug. Again not something that can be fixed in CefSharp.

• Source code location: packages/CefSharp.Common.143.0.90/src/CefSharp.BrowserSubprocess.Core/BrowserSubprocessExecutable.h line 64 uses Environment::GetCommandLineArgs() which retrieves all arguments from the main process

Nope. It only gets the arguments for the current process.

https://learn.microsoft.com/en-us/dotnet/api/system.environment.getcommandlineargs?view=net-10.0

Did you use an AI to perform this analysis? Have you validated the analysis?

Does this problem also occur in the CEF Sample Application

Yes using WPF/OffScreen command line args

Did you test with the CEF Sample Application (cefclient)? Details are in the bug report template.

Have you tried with Chrome at a similar version?

On the surface this looks more like an upstream change in behavior.

CEF has it's own issue tracker and support forum.
https://www.magpcss.org/ceforum/index.php
https://github.com/chromiumembedded/cef/issues