Send ESC DEL for Alt+Backspace and BS for Ctrl+Backspace

src/XTerm.NET.Tests/KeyboardInputTests.cs

@@ -200,6 +200,27 @@ public void ControlKeys_GenerateCorrectSequences()
         Assert.Equal(" ", terminal.GenerateKeyInput(Key.Space));
     }
 
+    [Fact]
+    public void Backspace_WithAlt_PrefixesEscape()
+    {
+        // Arrange
+        var terminal = CreateTerminal();
+
+        // Act & Assert
+        Assert.Equal("\x1B\x7F", terminal.GenerateKeyInput(Key.Backspace, KeyModifiers.Alt));
+    }
+
+    [Fact]
+    public void Backspace_WithControl_GeneratesBS()
+    {
+        // Arrange
+        var terminal = CreateTerminal();
+
+        // Act & Assert
+        Assert.Equal("\b", terminal.GenerateKeyInput(Key.Backspace, KeyModifiers.Control));
+        Assert.Equal("\x1B\b", terminal.GenerateKeyInput(Key.Backspace, KeyModifiers.Control | KeyModifiers.Alt));
+    }
+
     [Fact]
     public void Tab_WithShift_GeneratesBackTab()
     {

src/XTerm.NET/Input/KeyboardInputGenerator.cs

@@ -33,7 +33,7 @@ public string GenerateKeySequence(Key key, KeyModifiers modifiers = KeyModifiers
             // Control keys
             Key.Enter => "\r",
             Key.Tab => (modifiers & KeyModifiers.Shift) != 0 ? "\u001b[Z" : "\t",
-            Key.Backspace => "\u007f", // DEL (127)
+            Key.Backspace => GetBackspace(modifiers),
             // Escape sends ESC whatever the modifiers. CSI 27 ; mod ~ is not a sequence xterm
             // emits -- it belongs to the modifyOtherKeys and Kitty protocols, which an application
             // opts into. Sending it unasked meant a program that reads a bare ESC (vim leaving
@@ -161,6 +161,14 @@ public string GenerateCharSequence(char c, KeyModifiers modifiers = KeyModifiers
         };
     }
 
+    // xterm.js sends BS for Ctrl+Backspace and DEL otherwise, with an ESC prefix when Alt is
+    // held, which is how Alt+Backspace reaches a shell as backward-kill-word.
+    private static string GetBackspace(KeyModifiers modifiers)
+    {
+        var key = (modifiers & KeyModifiers.Control) != 0 ? "\b" : "\u007f";
+        return (modifiers & KeyModifiers.Alt) != 0 ? "\u001b" + key : key;
+    }
+
     private string GetArrowKey(char direction, KeyModifiers modifiers)
     {
         // Arrow keys respect ApplicationCursorKeys mode