When dealing with multiple stale PuTTY sessions after system resume, the modal "Fatal Error" dialog becomes a significant workflow blocker. Each disconnected session requires manual dismissal:

[Window Title]
PuTTY Fatal Error

[Content]
Network error: Software caused connection abort

[OK]

The native solution involves modifying PuTTY's configuration settings. Create or modify a session with these parameters:

# In your saved session settings (or Default Settings)
HostName example.com
Protocol ssh
CloseOnExit 1
WarnOnClose 0
SuppressErrorDialogs yes

For versions without GUI options, directly modify Windows Registry:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\Sessions\Default%20Settings]
"SuppressErrorDialogs"=dword:00000001
"WarnOnClose"=dword:00000001

Use PowerShell to programmatically close stale sessions:

Get-Process putty | Where-Object {
    $_.MainWindowTitle -match "Inactive"
} | ForEach-Object {
    # Send Alt+F4 to each window
    Add-Type -AssemblyName System.Windows.Forms
    [System.Windows.Forms.SendKeys]::SendWait("%{F4}")
}

For permanent solutions, consider modifying PuTTY's source (windows.c):

/* Original code showing dialog */
if (flags & MB_ICONERROR) {
    MessageBox(hwnd, msg, "PuTTY Fatal Error", flags);
}

/* Modified silent version */
if ((flags & MB_ICONERROR) && !cfg->suppress_err_dialogs) {
    MessageBox(hwnd, msg, "PuTTY Fatal Error", flags);
}

• Use persistent connections with tmux or screen
• Configure SSH keepalives (Add ServerAliveInterval 60 to ~/.ssh/config)
• Consider alternative clients like KiTTY with native session management

When working with multiple remote servers via PuTTY, it's common to accumulate inactive sessions after system sleep/resume cycles. While Windows allows bulk-closing applications from the taskbar, PuTTY's fatal error dialog ("Network error: Software caused connection abort") creates a modal barrier that forces manual handling of each session.

PuTTY doesn't expose this setting in its GUI, but we can modify the Windows Registry to suppress fatal errors:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\SimonTatham\PuTTY]
"SuppressErrorPopups"=dword:00000001

For scripted launches, use these PuTTY command-line options:

putty.exe -ssh user@host -no-antispoof -pw password

The -no-antispoof parameter prevents some (but not all) error dialogs from appearing.

Create a PowerShell script to clean up inactive PuTTY processes:

$puttyProcesses = Get-Process | Where-Object { 
    $_.MainWindowTitle -match "PuTTY.*$Inactive$" 
}
$puttyProcesses | ForEach-Object { $_.CloseMainWindow() }

If you want to maintain the close confirmation while suppressing fatal errors, modify PuTTY's configuration file:

; ~/.putty/sessions/Default%20Settings
WarnOnClose=1
SuppressErrors=1

For heavy terminal users, consider clients with better session management:

• KiTTY (PuTTY fork with enhanced features)
• Windows Terminal with OpenSSH
• MobaXTerm (tabbed interface with session persistence)