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Add periodic buffer persistence to protect against unexpected termination #19805

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4e7207d
Add periodic buffer persistence to protect against unexpected termina…
sebastiangeraldes Jan 28, 2026
d619be9
Add BSOD to spell checker exceptions
sebastiangeraldes Jan 28, 2026
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1 change: 1 addition & 0 deletions .github/actions/spelling/expect/expect.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -131,6 +131,7 @@ branchconfig
brandings
Browsable
Bspace
BSOD
BTNFACE
bufferout
buffersize
Expand Down
148 changes: 89 additions & 59 deletions src/cascadia/WindowsTerminal/WindowEmperor.cpp
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Expand Up @@ -1058,6 +1058,11 @@ void WindowEmperor::_setupSessionPersistence(bool enabled)
_persistStateTimer.Interval(std::chrono::minutes(5));
_persistStateTimer.Tick([&](auto&&, auto&&) {
_persistState(ApplicationState::SharedInstance());
// GH#19804: Also persist buffer content periodically to protect against
// unexpected termination (BSOD, power failure, etc.). Previously, buffer
// content was only saved on graceful exit, causing complete buffer loss
// after crashes even though tab layout was preserved.
_persistBuffers();
});
_persistStateTimer.Start();
}
Expand All @@ -1083,6 +1088,86 @@ void WindowEmperor::_persistState(const ApplicationState& state) const
state.Flush();
}

// GH#19804: Persist all terminal buffers to disk. This function is called both
// periodically (via the 5-minute timer) and on graceful shutdown. Periodic saves
// protect against unexpected termination (BSOD, power failure, Task Manager kill).
// Returns the set of buffer filenames that were written, for cleanup purposes.
std::unordered_set<std::wstring, til::transparent_hstring_hash, til::transparent_hstring_equal_to> WindowEmperor::_persistBuffers() const
{
using namespace std::string_view_literals;

std::unordered_set<std::wstring, til::transparent_hstring_hash, til::transparent_hstring_equal_to> bufferFilenames;

const auto firstWindowPreference = _app.Logic().Settings().GlobalSettings().FirstWindowPreference();
const auto persistBuffers = firstWindowPreference == FirstWindowPreference::PersistedLayoutAndContent;

if (!persistBuffers)
{
return bufferFilenames;
}

const std::filesystem::path settingsDirectory{ std::wstring_view{ CascadiaSettings::SettingsDirectory() } };
const auto admin = _app.Logic().IsRunningElevated();
const auto filenamePrefix = admin ? L"elevated_"sv : L"buffer_"sv;

// If the app is running elevated, we create files with a mandatory
// integrity label (ML) of "High" (HI) for reading and writing (NR, NW).
wil::unique_hlocal_security_descriptor sd;
SECURITY_ATTRIBUTES sa{};
if (admin)
{
unsigned long cb;
THROW_IF_WIN32_BOOL_FALSE(ConvertStringSecurityDescriptorToSecurityDescriptorW(L"S:(ML;;NRNW;;;HI)", SDDL_REVISION_1, wil::out_param_ptr<PSECURITY_DESCRIPTOR*>(sd), &cb));
sa.nLength = sizeof(SECURITY_ATTRIBUTES);
sa.lpSecurityDescriptor = sd.get();
}

// Persist all terminal buffers to "buffer_{guid}.txt" files.
// We remember the filenames so that we can clean up old ones later.
for (const auto& w : _windows)
{
const auto panes = w->Logic().Panes();
for (const auto pane : panes)
{
try
{
const auto term = pane.try_as<winrt::TerminalApp::ITerminalPaneContent>();
if (!term)
{
continue;
}
const auto control = term.GetTermControl();
if (!control)
{
continue;
}
const auto connection = control.Connection();
if (!connection)
{
continue;
}
const auto sessionId = connection.SessionId();
if (sessionId == winrt::guid{})
{
continue;
}

auto filename = fmt::format(FMT_COMPILE(L"{}{}.txt"), filenamePrefix, sessionId);
const auto path = settingsDirectory / filename;

if (wil::unique_hfile file{ CreateFileW(path.c_str(), GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_DELETE, &sa, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, nullptr) })
{
control.PersistTo(reinterpret_cast<int64_t>(file.get()));
bufferFilenames.emplace(std::move(filename));
}
}
CATCH_LOG();
}
}

return bufferFilenames;
}

void WindowEmperor::_finalizeSessionPersistence() const
{
using namespace std::string_view_literals;
Expand Down Expand Up @@ -1110,66 +1195,11 @@ void WindowEmperor::_finalizeSessionPersistence() const
const std::filesystem::path settingsDirectory{ std::wstring_view{ CascadiaSettings::SettingsDirectory() } };
const auto admin = _app.Logic().IsRunningElevated();
const auto filenamePrefix = admin ? L"elevated_"sv : L"buffer_"sv;
const auto persistBuffers = firstWindowPreference == FirstWindowPreference::PersistedLayoutAndContent;
std::unordered_set<std::wstring, til::transparent_hstring_hash, til::transparent_hstring_equal_to> bufferFilenames;

if (persistBuffers)
{
// If the app is running elevated, we create files with a mandatory
// integrity label (ML) of "High" (HI) for reading and writing (NR, NW).
wil::unique_hlocal_security_descriptor sd;
SECURITY_ATTRIBUTES sa{};
if (admin)
{
unsigned long cb;
THROW_IF_WIN32_BOOL_FALSE(ConvertStringSecurityDescriptorToSecurityDescriptorW(L"S:(ML;;NRNW;;;HI)", SDDL_REVISION_1, wil::out_param_ptr<PSECURITY_DESCRIPTOR*>(sd), &cb));
sa.nLength = sizeof(SECURITY_ATTRIBUTES);
sa.lpSecurityDescriptor = sd.get();
}

// Persist all terminal buffers to "buffer_{guid}.txt" files.
// We remember the filenames so that we can clean up old ones later.
for (const auto& w : _windows)
{
const auto panes = w->Logic().Panes();
for (const auto pane : panes)
{
try
{
const auto term = pane.try_as<winrt::TerminalApp::ITerminalPaneContent>();
if (!term)
{
continue;
}
const auto control = term.GetTermControl();
if (!control)
{
continue;
}
const auto connection = control.Connection();
if (!connection)
{
continue;
}
const auto sessionId = connection.SessionId();
if (sessionId == winrt::guid{})
{
continue;
}

auto filename = fmt::format(FMT_COMPILE(L"{}{}.txt"), filenamePrefix, sessionId);
const auto path = settingsDirectory / filename;

if (wil::unique_hfile file{ CreateFileW(path.c_str(), GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_DELETE, &sa, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, nullptr) })
{
control.PersistTo(reinterpret_cast<int64_t>(file.get()));
bufferFilenames.emplace(std::move(filename));
}
}
CATCH_LOG();
}
}
}
// GH#19804: Use the shared _persistBuffers() function instead of duplicating
// the buffer saving logic. This ensures consistency between periodic saves
// and shutdown saves.
const auto bufferFilenames = _persistBuffers();

// Now remove the "buffer_{guid}.txt" files that shouldn't be there.
if (_needsPersistenceCleanup)
Expand Down
1 change: 1 addition & 0 deletions src/cascadia/WindowsTerminal/WindowEmperor.h
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Expand Up @@ -66,6 +66,7 @@ class WindowEmperor
void _setupGlobalHotkeys();
void _setupSessionPersistence(bool enabled);
void _persistState(const winrt::Microsoft::Terminal::Settings::Model::ApplicationState& state) const;
std::unordered_set<std::wstring, til::transparent_hstring_hash, til::transparent_hstring_equal_to> _persistBuffers() const;
void _finalizeSessionPersistence() const;
void _checkWindowsForNotificationIcon();

Expand Down