Fix terminal scroll anFix terminal scroll and selection synchronization

eterm:
    - derive scroll and history notifications from adopted snapshots instead
      of delayed worker events
    - prevent PTY parsing from publishing its temporary live-buffer viewport
    - restore scrollback correctly when new output wraps the history ring
    - keep selections attached to their text during output and absolute scrolling
    - preserve terminal focus and selection while interacting with the scrollbar
    - keep the scrollbar available while a selection is active
    - suppress application mouse reports when Shift overrides mouse capture
    - preserve scrollback when Kitty reports standalone modifier keys
    - retain scroll-to-bottom behavior for regular and modified input keys
    - remove obsolete worker scroll and history event tracking
    - add regression coverage for viewport, selection, focus, keyboard, and
      history behaviord selection synchronization

src/modules/eterm/include/eterm/terminal/terminaldisplay.hpp

@@ -371,6 +371,7 @@ class TerminalDisplay {
 	bool mAlreadyClickedMButton{ false };
 	bool mKeepAlive{ true };
 	bool mDraggingSel{ false };
+	bool mSelectionOverridesMouseCapture{ false };
 	int mMode{ MODE_VISIBLE | MODE_FOCUSED };
 	TerminalCursorMode mCursorMode{ SteadyUnderline };
 	Clock mClock;

src/modules/eterm/include/eterm/terminal/terminalemulator.hpp

@@ -326,6 +326,8 @@ class TerminalEmulator final {
 
 	bool mDirty{ true };
 	bool mAllDirty{ true };
+	bool mProcessingPtyInput{ false };
+	int mPtyHistoryLinesPushed{ 0 };
 	Clock mPresentationClock;
 	Time mPresentationInterval{ Microseconds( 1000000.0 / 60.0 ) };
 	Clock mSynchronizedUpdateClock;
@@ -394,6 +396,7 @@ class TerminalEmulator final {
 	void csihandle();
 	bool handleKittyKeyboardProtocol();
 	KittyKeyboardState& activeKeyboardState();
+	void ttywriteInternal( const char* s, size_t n, int may_echo, bool scrollToBottom );
 	void resetKittyKeyboardProtocol();
 	void csiparse();
 	void csireset();

src/modules/eterm/include/eterm/terminal/terminalsession.hpp

@@ -93,19 +93,18 @@ class TerminalSession final : public std::enable_shared_from_this<TerminalSessio
 	using ProcPtr = std::unique_ptr<IProcess>;
 
 	enum class EventType : Uint8 {
-		Title,
-		IconTitle,
-		HistoryLength,
-		ScrollPosition,
-		Bell,
-		Clipboard,
-		ProcessExit,
-		RestartFailure,
-		SnapshotReady,
-		Data,
-		PromptState,
-		Color,
-		Error
+		Title = 0,
+		IconTitle = 1,
+		// Values 2 and 3 were retired; keep later values stable for ABI compatibility.
+		Bell = 4,
+		Clipboard = 5,
+		ProcessExit = 6,
+		RestartFailure = 7,
+		SnapshotReady = 8,
+		Data = 9,
+		PromptState = 10,
+		Color = 11,
+		Error = 12
 	};
 
 	struct Event {

src/modules/eterm/include/eterm/ui/uiterminal.hpp

@@ -170,8 +170,10 @@ class UITerminal : public UITouchDraggableWidget {
 	virtual Uint32 onFocus( NodeFocusReason reason );
 
 	virtual Uint32 onFocusLoss();
+	virtual Uint32 onMessage( const NodeMessage* msg );
 
 	virtual void updateScroll();
+	void syncScrollOffset();
 
 	virtual void onContentSizeChange();
 

src/modules/eterm/src/eterm/terminal/terminaldisplay.cpp

@@ -770,6 +770,7 @@ bool TerminalDisplay::update( bool isMouseOverMe ) {
 		if ( !( mWindow->getInput()->getPressTrigger() & EE_BUTTON_LMASK ) ) {
 			mWindow->getInput()->captureMouse( false );
 			mDraggingSel = false;
+			mSelectionOverridesMouseCapture = false;
 		} else if ( !isMouseOverMe ) {
 			onMouseMove( mWindow->getInput()->getMousePos(),
 						 mWindow->getInput()->getPressTrigger() );
@@ -809,6 +810,8 @@ void TerminalDisplay::consumeSnapshot() {
 		return;
 
 	const Vector2i previousCursor = mCursor;
+	const int previousHistoryLength = mSnapshot ? mSnapshot->historyLength : 0;
+	const int previousScrollPosition = mSnapshot ? mSnapshot->scrollPosition : 0;
 	const bool dimensionsChanged = snapshot->columns != static_cast<int>( mColumns ) ||
 								   snapshot->rows != static_cast<int>( mRows );
 	if ( dimensionsChanged ) {
@@ -857,6 +860,13 @@ void TerminalDisplay::consumeSnapshot() {
 		mMode |= MODE_BLINK;
 		mClock.restart();
 	}
+	// Scrollbar state must be announced only after the immutable state it describes has been
+	// adopted. Worker events can otherwise race publication and make the UI feed an older absolute
+	// position back into the session.
+	if ( previousScrollPosition != mSnapshot->scrollPosition )
+		sendEvent( { EventType::SCROLL_HISTORY } );
+	if ( previousHistoryLength != mSnapshot->historyLength )
+		sendEvent( { EventType::HISTORY_LENGTH_CHANGE } );
 	mDirty = true;
 }
 
@@ -871,9 +881,6 @@ void TerminalDisplay::drainSessionEvents() {
 			case TerminalSession::EventType::IconTitle:
 				sendEvent( { EventType::ICON_TITLE, std::move( event.data ) } );
 				break;
-			case TerminalSession::EventType::ScrollPosition:
-				sendEvent( { EventType::SCROLL_HISTORY } );
-				break;
 			case TerminalSession::EventType::Bell:
 				sendEvent( { EventType::BELL } );
 				break;
@@ -906,9 +913,6 @@ void TerminalDisplay::drainSessionEvents() {
 				Log::error( "Terminal worker error: %s", event.data.c_str() );
 				sendEvent( { EventType::WORKER_ERROR, std::move( event.data ) } );
 				break;
-			case TerminalSession::EventType::HistoryLength:
-				sendEvent( { EventType::HISTORY_LENGTH_CHANGE } );
-				break;
 			case TerminalSession::EventType::SnapshotReady:
 				break;
 		}
@@ -1139,9 +1143,13 @@ void TerminalDisplay::onMouseDoubleClick( const Vector2i& pos, const Uint32& fla
 }
 
 void TerminalDisplay::onMouseMove( const Vector2i& pos, const Uint32& flags ) {
-	bool shiftPressed = ( mWindow->getInput()->getModState() & KEYMOD_SHIFT ) != 0;
+	const Uint32 modifiers = mWindow->getInput()->getModState();
+	const bool shiftPressed = ( modifiers & KEYMOD_SHIFT ) != 0;
 	auto mousePos = mWindow->getInput()->getRelativeMousePos();
-	bool isCapturingMouse = isAppCapturingMouse() && !shiftPressed;
+	const bool appCapturingMouse = isAppCapturingMouse();
+	const bool selectionOverride =
+		mSelectionOverridesMouseCapture || ( appCapturingMouse && shiftPressed );
+	const bool isCapturingMouse = appCapturingMouse && !selectionOverride;
 
 	if ( !isAltScr() && !isCapturingMouse && ( flags & EE_BUTTON_LMASK ) &&
 		 mAlreadyClickedLButton ) {
@@ -1163,17 +1171,22 @@ void TerminalDisplay::onMouseMove( const Vector2i& pos, const Uint32& flags ) {
 		 ( mDraggingSel || getSelectionMode() == SEL_EMPTY || getSelectionMode() == SEL_READY ) ) {
 		auto gridPos{ positionToGrid( pos ) };
 		mSession->selectionExtend(
-			gridPos.x, gridPos.y,
-			mWindow->getInput()->getModState() & KEYMOD_SHIFT ? SEL_RECTANGULAR : SEL_REGULAR,
-			false );
+			gridPos.x, gridPos.y, modifiers & KEYMOD_SHIFT ? SEL_RECTANGULAR : SEL_REGULAR, false );
+	}
+	// Shift overrides application mouse capture so the user can select terminal text. Sending the
+	// same event to the application would make the override ineffective.
+	if ( !selectionOverride ) {
+		mSession->mouseReport( TerminalMouseEventType::MouseMotion, positionToGrid( pos ),
+							   positionToPixel( pos ), flags, modifiers );
 	}
-	mSession->mouseReport( TerminalMouseEventType::MouseMotion, positionToGrid( pos ),
-						   positionToPixel( pos ), flags, mWindow->getInput()->getModState() );
 }
 
 void TerminalDisplay::onMouseDown( const Vector2i& pos, const Uint32& flags ) {
-	bool shiftPressed = ( mWindow->getInput()->getModState() & KEYMOD_SHIFT ) != 0;
-	bool isCapturingMouse = isAppCapturingMouse() && !shiftPressed;
+	const Uint32 modifiers = mWindow->getInput()->getModState();
+	const bool shiftPressed = ( modifiers & KEYMOD_SHIFT ) != 0;
+	const bool appCapturingMouse = isAppCapturingMouse();
+	const bool selectionOverride = appCapturingMouse && shiftPressed;
+	const bool isCapturingMouse = appCapturingMouse && !selectionOverride;
 
 	if ( ( flags & EE_BUTTON_LMASK ) && mDraggingSel )
 		return;
@@ -1187,6 +1200,7 @@ void TerminalDisplay::onMouseDown( const Vector2i& pos, const Uint32& flags ) {
 		if ( !mDraggingSel ) {
 			mSession->selectionStart( gridPos.x, gridPos.y, 0 );
 			mDraggingSel = true;
+			mSelectionOverridesMouseCapture = selectionOverride;
 			invalidateLines();
 			mWindow->getInput()->captureMouse( true );
 		}
@@ -1208,11 +1222,18 @@ void TerminalDisplay::onMouseDown( const Vector2i& pos, const Uint32& flags ) {
 		}
 	}
 
-	mSession->mouseReport( TerminalMouseEventType::MouseButtonDown, positionToGrid( pos ),
-						   positionToPixel( pos ), flags, mWindow->getInput()->getModState() );
+	if ( !selectionOverride ) {
+		mSession->mouseReport( TerminalMouseEventType::MouseButtonDown, positionToGrid( pos ),
+							   positionToPixel( pos ), flags, modifiers );
+	}
 }
 
 void TerminalDisplay::onMouseUp( const Vector2i& pos, const Uint32& flags ) {
+	const Uint32 modifiers = mWindow->getInput()->getModState();
+	const bool shiftPressed = ( modifiers & KEYMOD_SHIFT ) != 0;
+	const bool appCapturingMouse = isAppCapturingMouse();
+	const bool selectionOverride =
+		mSelectionOverridesMouseCapture || ( appCapturingMouse && shiftPressed );
 	if ( ( flags & EE_BUTTON_LMASK ) && mDraggingSel ) {
 		mDraggingSel = false;
 	}
@@ -1221,11 +1242,12 @@ void TerminalDisplay::onMouseUp( const Vector2i& pos, const Uint32& flags ) {
 		mWindow->getClipboard()->setPrimarySelectionText( getSelection() );
 	}
 
-	Uint32 smod = sanitizeMod( mWindow->getInput()->getModState() );
+	Uint32 smod = sanitizeMod( modifiers );
 
 	if ( flags & EE_BUTTON_LMASK ) {
 		mAlreadyClickedLButton = false;
 		mWindow->getInput()->captureMouse( false );
+		mSelectionOverridesMouseCapture = false;
 	}
 
 	if ( flags & EE_BUTTON_MMASK )
@@ -1255,8 +1277,10 @@ void TerminalDisplay::onMouseUp( const Vector2i& pos, const Uint32& flags ) {
 		}
 	}
 
-	mSession->mouseReport( TerminalMouseEventType::MouseButtonRelease, positionToGrid( pos ),
-						   positionToPixel( pos ), flags, mWindow->getInput()->getModState() );
+	if ( !selectionOverride ) {
+		mSession->mouseReport( TerminalMouseEventType::MouseButtonRelease, positionToGrid( pos ),
+							   positionToPixel( pos ), flags, modifiers );
+	}
 }
 
 static inline Color termColor( unsigned int terminalColor, const std::vector<Color>& colors ) {

src/modules/eterm/src/eterm/terminal/terminalemulator.cpp

@@ -947,28 +947,33 @@ size_t TerminalEmulator::ttyread( void ) {
 				mDataCb( mBuf + mBuflen, ret );
 
 			int old_scr = mTerm.scr;
-			int old_histi = mTerm.histi;
+			// Selection coordinates share the viewport's coordinate space. Translate them before
+			// the temporary live-screen switch so parser writes cannot mistake historical text for
+			// a live cell and clear the selection.
+			if ( old_scr > 0 )
+				selmove( -old_scr );
 			mTerm.scr = 0;
 
 			mBuflen += ret;
+			// Parsing must update the live screen at scr == 0, but that temporary viewport is not
+			// presentation state. In particular, DECRST 2026 can call draw() from inside twrite().
+			// Publishing there lets the asynchronous UI mistake the live-screen override for a user
+			// scroll and feed it back through the scrollbar before the viewport is restored below.
+			mPtyHistoryLinesPushed = 0;
+			mProcessingPtyInput = true;
 			written = twrite( mBuf, mBuflen, 0 );
+			mProcessingPtyInput = false;
 			mBuflen -= written;
 			/* keep any incomplete UTF-8 byte sequence for the next call */
 			if ( mBuflen > 0 )
 				memmove( mBuf, mBuf + written, mBuflen );
 
 			if ( old_scr > 0 ) {
-				int lines_pushed = 0;
-				if ( mTerm.histsize > 0 ) {
-					lines_pushed = ( mTerm.histi - old_histi + mTerm.histsize ) % mTerm.histsize;
-				}
+				const int lines_pushed = mPtyHistoryLinesPushed;
 				mTerm.scr = eemin( mTerm.histlen, old_scr + lines_pushed );
-				if ( lines_pushed > 0 ) {
-					mSel.ob.y += lines_pushed;
-					mSel.oe.y += lines_pushed;
-
+				selmove( mTerm.scr );
+				if ( mTerm.scr != old_scr )
 					onScrollPositionChange();
-				}
 			}
 
 			return ret;
@@ -1025,7 +1030,9 @@ void TerminalEmulator::kscrollto( const TerminalArg* a ) {
 	int n = a->i;
 
 	if ( 0 <= n && n <= mTerm.histlen ) {
+		int delta = n - mTerm.scr;
 		mTerm.scr = n;
+		selmove( delta );
 		tfulldirt();
 		onScrollPositionChange();
 	}
@@ -1117,10 +1124,17 @@ bool TerminalEmulator::isScrolling() const {
 }
 
 void TerminalEmulator::ttywrite( const char* s, size_t n, int may_echo ) {
+	ttywriteInternal( s, n, may_echo, true );
+}
+
+void TerminalEmulator::ttywriteInternal( const char* s, size_t n, int may_echo,
+										 bool scrollToBottom ) {
 	const char* next;
 
-	TerminalArg arg = { (int)mTerm.scr };
-	kscrolldown( &arg );
+	if ( scrollToBottom ) {
+		TerminalArg arg = { (int)mTerm.scr };
+		kscrolldown( &arg );
+	}
 
 	if ( may_echo && IS_SET( MODE_ECHO ) )
 		twrite( s, (int)n, 1 );
@@ -1149,6 +1163,22 @@ static Uint32 keyboardSanitizeMod( Uint32 mod ) {
 	return mod & KEYMOD_CTRL_SHIFT_ALT_META;
 }
 
+static bool isModifierKey( Keycode keycode ) {
+	switch ( keycode ) {
+		case KEY_LCTRL:
+		case KEY_LSHIFT:
+		case KEY_LALT:
+		case KEY_LGUI:
+		case KEY_RCTRL:
+		case KEY_RSHIFT:
+		case KEY_RALT:
+		case KEY_RGUI:
+			return true;
+		default:
+			return false;
+	}
+}
+
 static char legacyControlCharacter( Scancode scancode ) {
 	if ( scancode >= SCANCODE_A && scancode <= SCANCODE_Z )
 		return static_cast<char>( scancode - SCANCODE_A + 1 );
@@ -1181,7 +1211,8 @@ void TerminalEmulator::keyEvent( const KittyKeyEvent& event ) {
 	}
 	const auto enhanced = KittyKeyboardEncoder::encode( event, flags );
 	if ( enhanced.handled ) {
-		ttywrite( enhanced.bytes.data(), enhanced.bytes.size(), 1 );
+		ttywriteInternal( enhanced.bytes.data(), enhanced.bytes.size(), 1,
+						  !isModifierKey( event.keycode ) );
 		mExpectedTextInput = enhanced.expectedText;
 		return;
 	}
@@ -1470,6 +1501,8 @@ void TerminalEmulator::tscrollup( int top, int n, int copyhist ) {
 
 		for ( i = 0; i < n; i++ )
 			historyStealPush( &mTerm.line[top + i], mTerm.col );
+		if ( mProcessingPtyInput )
+			mPtyHistoryLinesPushed += n;
 
 		if ( attop )
 			mTerm.scr = mTerm.histlen;
@@ -3874,8 +3907,9 @@ void TerminalEmulator::drawregion( ITerminalDisplay& dpy, int x1, int y1, int x2
 
 void TerminalEmulator::draw() {
 	// DEC private mode 2026 makes the bytes between DECSET and DECRST one presentation unit.
-	// Parsing continues normally, but no partially cleared/rebuilt frame may reach the UI.
-	if ( mTerm.is_syncing )
+	// PTY parsing can also temporarily force scr to zero while updating the live screen. Neither
+	// state is a stable presentation boundary, so no partial frame or viewport may reach the UI.
+	if ( mTerm.is_syncing || mProcessingPtyInput )
 		return;
 
 	int cx = mTerm.c.x /*, ocx = term.ocx, ocy = term.ocy*/;

src/modules/eterm/src/eterm/terminal/terminalsession.cpp

@@ -135,12 +135,6 @@ class TerminalSession::WorkerDisplay final : public ITerminalDisplay {
 			if ( auto* process = mEmulator->getProcess() )
 				snapshot->processId = process->pid();
 		}
-		if ( snapshot->historyLength != mLastHistoryLength ) {
-			mLastHistoryLength = snapshot->historyLength;
-			Event event{ EventType::HistoryLength };
-			event.value = mLastHistoryLength;
-			mSession.enqueueEvent( std::move( event ), true );
-		}
 		mSession.publishSnapshot( std::move( snapshot ) );
 	}
 
@@ -239,8 +233,6 @@ class TerminalSession::WorkerDisplay final : public ITerminalDisplay {
 		mSession.enqueueEvent( std::move( event ), false );
 	}
 
-	void onScrollPositionChange() { mSession.enqueueEvent( { EventType::ScrollPosition }, true ); }
-
 	void setPalette( TerminalColorPalette palette ) {
 		mInitialPalette = palette;
 		mPalette = std::move( palette );
@@ -284,7 +276,6 @@ class TerminalSession::WorkerDisplay final : public ITerminalDisplay {
 	TerminalGlyph mCursorGlyph;
 	int mColumns{ 0 };
 	int mRows{ 0 };
-	int mLastHistoryLength{ -1 };
 	Uint32 mPresentationRate{ 60 };
 	bool mCursorVisible{ false };
 };
@@ -498,10 +489,9 @@ void TerminalSession::enqueueEvent( Event event, bool coalescable ) {
 	std::lock_guard<std::mutex> lock( mEventMutex );
 	if ( coalescable ) {
 		for ( auto it = mEvents.rbegin(); it != mEvents.rend(); ++it ) {
-			const bool replaceable =
-				it->type == EventType::Title || it->type == EventType::IconTitle ||
-				it->type == EventType::HistoryLength || it->type == EventType::ScrollPosition ||
-				it->type == EventType::SnapshotReady;
+			const bool replaceable = it->type == EventType::Title ||
+									 it->type == EventType::IconTitle ||
+									 it->type == EventType::SnapshotReady;
 			if ( !replaceable )
 				break;
 			if ( it->type == event.type ) {

src/modules/eterm/src/eterm/ui/uiterminal.cpp

@@ -93,7 +93,11 @@ UITerminal::UITerminal( const std::shared_ptr<TerminalDisplay>& terminalDisplay
 	syncFontRenderingConfig();
 	registerNewTerminal();
 	mVScroll->setParent( this );
-	mVScroll->on( Event::OnValueChange, [this]( const Event* ) { updateScroll(); } );
+	mVScroll->on( Event::OnValueChange, [this]( const Event* ) {
+		updateScroll();
+		if ( !mApplyingScrollController )
+			stopScrollController();
+	} );
 
 	setCommand( "terminal-scroll-up-screen",
 				[this] { mTerm->action( TerminalShortcutAction::SCROLLUP_SCREEN ); } );
@@ -162,7 +166,9 @@ void UITerminal::onContentSizeChange() {
 	mPendingContentSizeChange = false;
 	updateScrollPosition();
 	mVScroll->setPageStep( contentSize > 0 ? ( visibleArea / (Float)contentSize ) : 1.f );
-	updateScroll();
+	// This is a worker-to-UI state synchronization, not a user scroll. Feeding it back through
+	// onScrollChange() queues a stale absolute position if the worker advances in the meantime.
+	syncScrollOffset();
 }
 
 const ScrollBarMode& UITerminal::getVerticalScrollMode() const {
@@ -225,15 +231,19 @@ int UITerminal::getScrollableArea() const {
 }
 
 void UITerminal::updateScroll() {
-	int totalScroll = getScrollableArea();
 	int initScroll( mScrollOffset );
+	syncScrollOffset();
+
+	if ( initScroll != mScrollOffset )
+		onScrollChange();
+}
+
+void UITerminal::syncScrollOffset() {
+	int totalScroll = getScrollableArea();
 	mScrollOffset = 0;
 
 	if ( mVScroll->isVisible() && totalScroll > 0 )
 		mScrollOffset = totalScroll * mVScroll->getValue();
-
-	if ( initScroll != mScrollOffset )
-		onScrollChange();
 }
 
 void UITerminal::onScrollChange() {
@@ -531,8 +541,7 @@ Uint32 UITerminal::onKeyUp( const KeyEvent& event ) {
 Uint32 UITerminal::onMouseMove( const Vector2i& position, const Uint32& flags ) {
 	if ( mViewType == ScrollViewType::Overlay && ScrollBarMode::Auto == mVScrollMode ) {
 		mMouseClock.restart();
-		bool visible =
-			!mTerm->isAltScr() && getContentSize() > getVisibleArea() && !mTerm->hasSelection();
+		bool visible = !mTerm->isAltScr() && getContentSize() > getVisibleArea();
 		mVScroll->setVisible( visible )->setEnabled( visible );
 	}
 
@@ -647,12 +656,26 @@ Uint32 UITerminal::onFocus( NodeFocusReason reason ) {
 
 Uint32 UITerminal::onFocusLoss() {
 	getUISceneNode()->getWindow()->stopTextInput();
-	mTerm->clearSuppressedKeys();
-	mTerm->setFocus( false );
+	Node* focusNode = getEventDispatcher()->getFocusNode();
+	const bool scrollBarFocus = focusNode == mVScroll || mVScroll->isParentOf( focusNode );
+	if ( !scrollBarFocus ) {
+		mTerm->clearSuppressedKeys();
+		mTerm->setFocus( false );
+	}
 	invalidateDraw();
 	return UIWidget::onFocusLoss();
 }
 
+Uint32 UITerminal::onMessage( const NodeMessage* msg ) {
+	if ( msg->getMsg() == NodeMessage::Focus &&
+		 ( msg->getSender() == mVScroll || mVScroll->isParentOf( msg->getSender() ) ) ) {
+		// The scrollbar is part of the terminal. Keep keyboard/PTY focus on the terminal instead
+		// of reporting a transient focus-out/focus-in pair to the application.
+		setFocus();
+	}
+	return UITouchDraggableWidget::onMessage( msg );
+}
+
 void UITerminal::createDefaultContextMenuOptions( UIPopUpMenu* menu ) {
 	if ( !mCreateDefaultContextMenuOptions )
 		return;

src/tests/unit_tests/eterm_tests.cpp

@@ -293,6 +293,28 @@ UTEST( eterm_session, focus_reporting_is_ordered_on_worker ) {
 	EXPECT_STDSTREQ( "\033[I", ptyPtr->mWrites.substr( ptyPtr->mWrites.size() - 3 ) );
 }
 
+UTEST( eterm_session, focus_commands_do_not_clear_selection ) {
+	auto pty = std::make_unique<MockPty>();
+	pty->mBuffer = "persistent selection";
+	auto process = std::make_unique<MockProcess>();
+	auto session = TerminalSession::create( std::move( pty ), std::move( process ), 100 );
+	ASSERT_TRUE( waitForSnapshot( session, []( const TerminalSnapshot& snapshot ) {
+					 return !snapshot.cells.empty() && snapshot.cells[0].u == 'p';
+				 } ) != nullptr );
+
+	session->selectionStart( 0, 0, 0 );
+	session->selectionExtend( 9, 0, SEL_REGULAR, false );
+	auto selected = session->requestSelection();
+	ASSERT_TRUE( selected.has_value() );
+	ASSERT_STDSTREQ( "persistent", *selected );
+
+	session->setFocus( false );
+	session->setFocus( true );
+	auto afterFocusChange = session->requestSelection();
+	ASSERT_TRUE( afterFocusChange.has_value() );
+	EXPECT_STDSTREQ( "persistent", *afterFocusChange );
+}
+
 UTEST( eterm_session, replaceable_events_coalesce_without_losing_ordered_events ) {
 	auto pty = std::make_unique<MockPty>();
 	auto process = std::make_unique<MockProcess>();
@@ -421,6 +443,7 @@ class MockDisplay : public ITerminalDisplay {
   public:
 	int mDrawLines{ 0 };
 	int mDrawEnds{ 0 };
+	std::vector<int> mPublishedScrollPositions;
 	uint32_t mFirstMode{ 0 };
 	uint32_t mSecondMode{ 0 };
 	TerminalGlyph mFirstGlyph;
@@ -440,7 +463,11 @@ class MockDisplay : public ITerminalDisplay {
 		}
 	}
 	void drawCursor( int, int, TerminalGlyph, int, int, TerminalGlyph ) override {}
-	void drawEnd() override { ++mDrawEnds; }
+	void drawEnd() override {
+		++mDrawEnds;
+		if ( mEmulator )
+			mPublishedScrollPositions.emplace_back( mEmulator->scrollPos() );
+	}
 	void resetColors() override { ++mResetColorsCount; }
 	void drawGraphics( std::shared_ptr<TerminalGraphicsPresentation> presentation,
 					   std::vector<TerminalGraphicsUpdate> ) override {
@@ -1048,6 +1075,34 @@ UTEST( eterm, kitty_keyboard_protocol_encodes_worker_key_without_duplicate_text
 	EXPECT_STDSTREQ( "\033[97;1u\033[13;5u", ptyPtr->mWrites );
 }
 
+UTEST( eterm, kitty_modifier_key_does_not_scroll_to_bottom ) {
+	auto pty = std::make_unique<MockPty>();
+	pty->mBuffer = "\033[>8u";
+	MockPty* ptyPtr = pty.get();
+	auto process = std::make_unique<MockProcess>();
+	auto display = std::make_shared<MockDisplay>();
+	auto term = TerminalEmulator::create( std::move( pty ), std::move( process ), display, 100 );
+	term->update();
+
+	for ( int i = 0; i < 40; ++i ) {
+		std::string line = "Line " + std::to_string( i ) + "\r\n";
+		term->write( line.c_str(), line.size() );
+		term->update();
+	}
+	ptyPtr->mLoopWrites = false;
+
+	TerminalArg scroll( 5 );
+	term->kscrollup( &scroll );
+	ptyPtr->mWrites.clear();
+
+	term->keyEvent( { KEY_LCTRL, SCANCODE_LCTRL, 0, KEYMOD_LCTRL, KittyKeyEventType::Press } );
+	EXPECT_FALSE( ptyPtr->mWrites.empty() );
+	EXPECT_EQ( 5, term->scrollPos() );
+
+	term->keyEvent( { KEY_A, SCANCODE_A, 0, KEYMOD_LCTRL, KittyKeyEventType::Press } );
+	EXPECT_EQ( 0, term->scrollPos() );
+}
+
 UTEST( eterm, kitty_keyboard_protocol_preserves_altgr_text ) {
 	auto pty = std::make_unique<MockPty>();
 	pty->mBuffer = "\033[>15u";
@@ -1464,6 +1519,33 @@ UTEST( eterm, synchronized_updates_publish_only_complete_frames ) {
 	EXPECT_STDSTREQ( "complete", term->getSelection() );
 }
 
+UTEST( eterm, pty_parsing_does_not_publish_temporary_bottom_viewport ) {
+	auto pty = std::make_unique<MockPty>();
+	auto process = std::make_unique<MockProcess>();
+	auto display = std::make_shared<MockDisplay>();
+	auto term = TerminalEmulator::create( std::move( pty ), std::move( process ), display, 100 );
+
+	for ( int line = 0; line < 40; ++line ) {
+		const std::string output = "history " + std::to_string( line ) + "\r\n";
+		term->write( output.data(), output.size() );
+		term->update();
+	}
+
+	TerminalArg scroll( 5 );
+	term->kscrollup( &scroll );
+	ASSERT_EQ( 5, term->scrollPos() );
+	display->mPublishedScrollPositions.clear();
+
+	const char synchronizedOutput[] = "\033[?2026hnew output\r\n\033[?2026l";
+	term->write( synchronizedOutput, sizeof( synchronizedOutput ) - 1 );
+	term->update();
+
+	ASSERT_FALSE( display->mPublishedScrollPositions.empty() );
+	for ( int scrollPosition : display->mPublishedScrollPositions )
+		EXPECT_TRUE( scrollPosition > 0 );
+	EXPECT_EQ( 6, display->mPublishedScrollPositions.back() );
+}
+
 UTEST( eterm, sgr_colon_subparameters_preserve_groups_and_optional_color_space ) {
 	auto pty = std::make_unique<MockPty>();
 	auto process = std::make_unique<MockProcess>();
@@ -2272,6 +2354,88 @@ UTEST( eterm, scroll_position_after_ttyread ) {
 	EXPECT_STDSTREQ( "New output", term->getSelection() );
 }
 
+UTEST( eterm, ttyread_keeps_scrolled_selection_attached_to_text ) {
+	auto pty = std::make_unique<MockPty>();
+	auto process = std::make_unique<MockProcess>();
+	auto display = std::make_shared<MockDisplay>();
+	auto term = TerminalEmulator::create( std::move( pty ), std::move( process ), display, 100 );
+
+	for ( int i = 0; i < 40; ++i ) {
+		std::string line = "Line " + std::to_string( i ) + "\r\n";
+		term->write( line.c_str(), line.size() );
+		term->update();
+	}
+
+	TerminalArg scroll( 5 );
+	term->kscrollup( &scroll );
+	term->selstart( 0, 23, 0 );
+	term->selextend( 6, 23, SEL_REGULAR, false );
+	ASSERT_STDSTREQ( "Line 35", term->getSelection() );
+
+	term->write( "New output\r\n", 12 );
+	term->update();
+
+	EXPECT_EQ( 6, term->scrollPos() );
+	EXPECT_STDSTREQ( "Line 35", term->getSelection() );
+}
+
+UTEST( eterm, ttyread_restores_viewport_after_history_ring_wrap ) {
+	auto pty = std::make_unique<MockPty>();
+	auto process = std::make_unique<MockProcess>();
+	auto display = std::make_shared<MockDisplay>();
+	auto term = TerminalEmulator::create( std::move( pty ), std::move( process ), display, 4 );
+
+	for ( int i = 0; i < 28; ++i ) {
+		std::string line = "Line " + std::to_string( i ) + "\r\n";
+		term->write( line.c_str(), line.size() );
+		term->update();
+	}
+
+	TerminalArg scroll( 2 );
+	term->kscrollup( &scroll );
+	ASSERT_EQ( 2, term->scrollPos() );
+
+	// One PTY read pushes exactly histsize rows, wrapping histi back to its original index.
+	// The viewport must still account for all four pushed rows and clamp to the oldest history.
+	const char burst[] = "Burst 0\r\nBurst 1\r\nBurst 2\r\nBurst 3\r\n";
+	term->write( burst, sizeof( burst ) - 1 );
+	term->update();
+	EXPECT_EQ( 4, term->scrollPos() );
+
+	TerminalArg bottom( INT_MAX );
+	term->kscrolldown( &bottom );
+	term->selstart( 0, 22, 0 );
+	term->selextend( 6, 22, SEL_REGULAR, false );
+	EXPECT_STDSTREQ( "Burst 3", term->getSelection() );
+}
+
+UTEST( eterm, absolute_scrolling_keeps_selection_attached_to_text ) {
+	auto pty = std::make_unique<MockPty>();
+	auto process = std::make_unique<MockProcess>();
+	auto display = std::make_shared<MockDisplay>();
+	auto term = TerminalEmulator::create( std::move( pty ), std::move( process ), display, 100 );
+
+	for ( int i = 0; i < 40; ++i ) {
+		std::string line = "Line " + std::to_string( i ) + "\r\n";
+		term->write( line.c_str(), line.size() );
+		term->update();
+	}
+
+	TerminalArg scroll( 5 );
+	term->kscrollto( &scroll );
+	term->selstart( 0, 23, 0 );
+	term->selextend( 6, 23, SEL_REGULAR, false );
+	ASSERT_STDSTREQ( "Line 35", term->getSelection() );
+
+	scroll.i = 10;
+	term->kscrollto( &scroll );
+	EXPECT_STDSTREQ( "Line 35", term->getSelection() );
+
+	scroll.i = 2;
+	term->kscrollto( &scroll );
+	EXPECT_STDSTREQ( "Line 35", term->getSelection() );
+}
+
 UTEST( eterm, history_corruption_on_resize ) {
 	auto pty = std::make_unique<MockPty>();
 	auto process = std::make_unique<MockProcess>();