Fix parsing of chunked win32-input-mode sequences

src/terminal/parser/InputStateMachineEngine.cpp

@@ -102,6 +102,11 @@ InputStateMachineEngine::InputStateMachineEngine(std::unique_ptr<IInteractDispat
     THROW_HR_IF_NULL(E_INVALIDARG, _pDispatch.get());
 }
 
+bool InputStateMachineEngine::EncounteredWin32InputModeSequence() const noexcept
+{
+    return _encounteredWin32InputModeSequence;
+}
+
 void InputStateMachineEngine::SetLookingForDSR(const bool looking) noexcept
 {
     _lookingForDSR = looking;
@@ -448,6 +453,7 @@ bool InputStateMachineEngine::ActionCsiDispatch(const VTID id, const VTParameter
         // Ctrl+C, Ctrl+Break are handled correctly.
         const auto key = _GenerateWin32Key(parameters);
         success = _pDispatch->WriteCtrlKey(key);
+        _encounteredWin32InputModeSequence = true;
         break;
     }
     default:

src/terminal/parser/InputStateMachineEngine.hpp

@@ -132,6 +132,7 @@ namespace Microsoft::Console::VirtualTerminal
         InputStateMachineEngine(std::unique_ptr<IInteractDispatch> pDispatch,
                                 const bool lookingForDSR);
 
+        bool EncounteredWin32InputModeSequence() const noexcept;
         void SetLookingForDSR(const bool looking) noexcept;
 
         bool ActionExecute(const wchar_t wch) override;
@@ -167,6 +168,7 @@ namespace Microsoft::Console::VirtualTerminal
         const std::unique_ptr<IInteractDispatch> _pDispatch;
         std::function<bool()> _pfnFlushToInputQueue;
         bool _lookingForDSR;
+        bool _encounteredWin32InputModeSequence = false;
         DWORD _mouseButtonState = 0;
         std::chrono::milliseconds _doubleClickTime;
         std::optional<til::point> _lastMouseClickPos{};

src/terminal/parser/stateMachine.cpp

@@ -6,6 +6,7 @@
 #include "stateMachine.hpp"
 
 #include "ascii.hpp"
+#include "InputStateMachineEngine.hpp"
 
 using namespace Microsoft::Console::VirtualTerminal;
 
@@ -2144,9 +2145,16 @@ void StateMachine::ProcessString(const std::wstring_view string)
         // which breaks up many of our longer sequences, like our Win32InputMode ones.
         //
         // As a heuristic, this code specifically checks for a trailing Esc or Alt+key.
+        // If we encountered a win32-input-mode sequence before, we know that our\x1b[?9001h
+        // request to enable them was successful. While a client may still send \x1b{some char}
+        // intentionally, it's far more likely now that we're looking at a broken up sequence.
+        // The most common win32-input-mode is ConPTY itself after all, and we never emit
+        // \x1b{some char} once it's enabled.
         if (_isEngineForInput)
         {
-            if (run.size() <= 2 && run.front() == L'\x1b')
+            const auto engine = static_cast<InputStateMachineEngine*>(_engine.get());
+            const auto win32 = engine->EncounteredWin32InputModeSequence();
+            if (!win32 && run.size() <= 2 && run.front() == L'\x1b')
             {
                 _EnterGround();
                 if (run.size() == 1)