I think this is the rest of the cleanup needed for PR

src/cascadia/TerminalCore/TerminalDispatch.cpp

@@ -246,10 +246,11 @@ bool TerminalDispatch::SetCursorKeysMode(const bool applicationMode) noexcept
     return true;
 }
 
-// Method Description
-// - TODO
+// Method Description:
+// - win32-input-mode: Enable sending full input records encoded as a string of
+//   characters to the client application.
 // Arguments:
-// - applicationMode - set to true to enable Application Mode Input, false for Numeric Mode Input.
+// - win32InputMode - set to true to enable win32-input-mode, false to disable.
 // Return Value:
 // - True if handled successfully. False otherwise.
 bool TerminalDispatch::EnableWin32InputMode(const bool win32Mode) noexcept

src/renderer/vt/VtSequences.cpp

@@ -438,7 +438,10 @@ using namespace Microsoft::Console::Render;
 }
 
 // Method Description:
-// - TODO
+// - Send a sequence to the connected terminal to request win32-input-mode from
+//   them. This will enable the connected terminal to send us full INPUT_RECORDs
+//   as input. If the terminal doesn't understand this sequence, it'll just
+//   ignore it.
 // Arguments:
 // - <none>
 // Return Value:

src/renderer/vt/state.cpp

@@ -511,7 +511,10 @@ void VtEngine::SetResizeQuirk(const bool resizeQuirk)
 }
 
 // Method Description:
-// - TODO
+// - Send a sequence to the connected terminal to request win32-input-mode from
+//   them. This will enable the connected terminal to send us full INPUT_RECORDs
+//   as input. If the terminal doesn't understand this sequence, it'll just
+//   ignore it.
 // Arguments:
 // - <none>
 // Return Value:

src/terminal/adapter/InteractDispatch.cpp

@@ -37,11 +37,12 @@ bool InteractDispatch::WriteInput(std::deque<std::unique_ptr<IInputEvent>>& inpu
 }
 
 // Method Description:
-// - Writes a Ctrl-C event to the host. The host will then decide what to do
-//   with it, including potentially sending an interrupt to a client
-//   application.
+// - Writes a key event to the host in a fashion that will enable the host to
+//   process special keys such as Ctrl-C or Ctrl+Break. The host will then
+//   decide what to do with it, including potentially sending an interrupt to a
+//   client application.
 // Arguments:
-// TODO
+// - event: The key to send to the host.
 // Return Value:
 // True if handled successfully. False otherwise.
 bool InteractDispatch::WriteCtrlKey(const KeyEvent& event)

src/terminal/parser/InputStateMachineEngine.cpp

@@ -350,7 +350,16 @@ bool InputStateMachineEngine::ActionCsiDispatch(const wchar_t wch,
                                                 const std::basic_string_view<size_t> parameters)
 {
     const auto actionCode = static_cast<CsiActionCodes>(wch);
-    if (_pDispatch->IsVtInputEnabled() && _pfnFlushToInputQueue && actionCode != CsiActionCodes::Win32KeyboardInput)
+
+    // GH#4999 - If the client was in VT input mode, but we received a
+    // win32-input-mode sequence, then _don't_ passthrough the sequence to the
+    // client. It's impossibly unlikely that the client actually wanted
+    // win32-input-mode, and if they did, then we'll just translate the
+    // INPUT_RECORD back to the same sequence we say here later on, when the
+    // client reads it.
+    if (_pDispatch->IsVtInputEnabled() &&
+        _pfnFlushToInputQueue &&
+        actionCode != CsiActionCodes::Win32KeyboardInput)
     {
         return _pfnFlushToInputQueue();
     }