readme update

README.md

@@ -2,7 +2,15 @@
 
 JavaFX canvas terminal prototype using `jlibghostty` for terminal emulation and Nix for
 the build environment. It builds a plain JavaFX application (JDK 25, JavaFX 25 via Gradle)
-packaged as a Nix derivation — no GraalVM/GluonFX native image.
+packaged as a Nix derivation — no GraalVM/GluonFX native image. It supports tiled and
+floating panes and tabs.
+
+> [!CAUTION]
+> `nix profile add` has only been tested on **Debian with the proprietary NVIDIA driver**.
+> The runtime GL shim hardcodes Debian's `/lib/x86_64-linux-gnu` driver paths and selects
+> the NVIDIA GLX/EGL vendor, so it likely won't work yet on other distros, Wayland-only
+> setups, or Mesa/AMD/Intel GPUs. I'm happy to accept pull requests that broaden host
+> support.
 
 ## Build
 
@@ -11,7 +19,7 @@ nix build
 ./result/bin/jprototerm
 ```
 
-Install it into a profile (works on NixOS and on a plain Debian box with Nix installed):
+Install it into a profile (see the caution above on host support):
 
 ```sh
 nix profile add .
@@ -97,9 +105,12 @@ navigate_down = "ALT+J"
 navigate_up = "ALT+K"
 navigate_right = "ALT+L"
 toggle_floating = "ALT+F"
-new_floating = "ALT+SHIFT+F"
+new_pane = "ALT+N"
 next_floating = "ALT+F12"
 close_pane = "ALT+X"
+new_tab = "ALT+A"
+previous_tab = "ALT+SHIFT+H"
+next_tab = "ALT+SHIFT+L"
 open_font_selector = "ALT+T"
 open_scrollback = "ALT+S"
 ```
@@ -107,11 +118,19 @@ open_scrollback = "ALT+S"
 ## Defaults
 
 - `Alt+h/j/k/l`: navigate panes
+- `Alt+n`: new pane — a floating pane when floating panes are shown, otherwise a new tiled
+  pane (tiled panes are split equally across the width)
 - `Alt+f`: show or hide all floating panes
-- `Alt+Shift+f`: create a new floating pane
 - `Alt+F12`: cycle floating panes
-- `Alt+x`: close the active floating pane
+- `Alt+x`: close the active pane; closing a tab's last pane closes the tab, and closing the
+  last pane of the last tab quits
+- `Alt+a`: new tab
+- `Alt+Shift+h` / `Alt+Shift+l`: previous / next tab
 - `Alt+t`: open the font selector
 - `Alt+s`: open the active pane scrollback in `$EDITOR`
 - Font default: `JetBrainsMono Nerd Font`
 - Kitty graphics protocol parsing is enabled by default
+
+Each tab has its own stack of tiled and floating panes; only the active tab is rendered. A
+thin tab bar appears at the top when more than one tab is open. Closing the last tiled pane
+while floating panes exist promotes the most recently active floating pane to a tiled pane.

flake.lock

@@ -70,11 +70,11 @@
         "nixpkgs": "nixpkgs"
       },
       "locked": {
-        "lastModified": 1780050576,
-        "narHash": "sha256-u06xuO3QnLDpajIOZwDdhwI0HGzMuXG7x1pR+4Zb+RA=",
+        "lastModified": 1780079529,
+        "narHash": "sha256-AxlGTL8c5xSLcQHvWlm994IdOqxsN8iKrA02Cpv7vso=",
         "ref": "refs/heads/main",
-        "rev": "d558d554b360a76d03c2fc09d327e3ec4aade878",
-        "revCount": 17,
+        "rev": "68121d50b52fb56038871c97c97e7a12ffe987c2",
+        "revCount": 20,
         "type": "git",
         "url": "https://gitea.gregorlohaus.com/gregor/jlibghostty.git"
       },

src/main/java/com/gregor/jprototerm/AppConfig.java

@@ -36,9 +36,12 @@ public record AppConfig(
             "navigate_up",
             "navigate_right",
             "toggle_floating",
-            "new_floating",
+            "new_pane",
             "next_floating",
             "close_pane",
+            "new_tab",
+            "previous_tab",
+            "next_tab",
             "open_font_selector",
             "open_scrollback"
     );
@@ -86,17 +89,20 @@ public record AppConfig(
                 true,
                 defaultScrollbackEditorCommand(),
                 Map.of(),
-                Map.of(
-                        "navigate_left", KeyBinding.parse("ALT+H"),
-                        "navigate_down", KeyBinding.parse("ALT+J"),
-                        "navigate_up", KeyBinding.parse("ALT+K"),
-                        "navigate_right", KeyBinding.parse("ALT+L"),
-                        "toggle_floating", KeyBinding.parse("ALT+F"),
-                        "new_floating", KeyBinding.parse("ALT+SHIFT+F"),
-                        "next_floating", KeyBinding.parse("ALT+F12"),
-                        "close_pane", KeyBinding.parse("ALT+X"),
-                        "open_font_selector", KeyBinding.parse("ALT+T"),
-                        "open_scrollback", KeyBinding.parse("ALT+S")
+                Map.ofEntries(
+                        Map.entry("navigate_left", KeyBinding.parse("ALT+H")),
+                        Map.entry("navigate_down", KeyBinding.parse("ALT+J")),
+                        Map.entry("navigate_up", KeyBinding.parse("ALT+K")),
+                        Map.entry("navigate_right", KeyBinding.parse("ALT+L")),
+                        Map.entry("toggle_floating", KeyBinding.parse("ALT+F")),
+                        Map.entry("new_pane", KeyBinding.parse("ALT+N")),
+                        Map.entry("next_floating", KeyBinding.parse("ALT+F12")),
+                        Map.entry("close_pane", KeyBinding.parse("ALT+X")),
+                        Map.entry("new_tab", KeyBinding.parse("ALT+A")),
+                        Map.entry("previous_tab", KeyBinding.parse("ALT+SHIFT+H")),
+                        Map.entry("next_tab", KeyBinding.parse("ALT+SHIFT+L")),
+                        Map.entry("open_font_selector", KeyBinding.parse("ALT+T")),
+                        Map.entry("open_scrollback", KeyBinding.parse("ALT+S"))
                 )
         );
     }

src/main/java/com/gregor/jprototerm/Main.java

@@ -2,6 +2,7 @@ package com.gregor.jprototerm;
 
 import javafx.animation.AnimationTimer;
 import javafx.application.Application;
+import javafx.application.Platform;
 import javafx.scene.Scene;
 import javafx.scene.control.ButtonType;
 import javafx.scene.control.ComboBox;
@@ -71,8 +72,8 @@ public final class Main extends Application {
         } else if (config.keybindings().get("toggle_floating").matches(event)) {
             workspace.toggleFloating();
             event.consume();
-        } else if (config.keybindings().get("new_floating").matches(event)) {
-            workspace.createFloatingPane();
+        } else if (config.keybindings().get("new_pane").matches(event)) {
+            workspace.createPane();
             event.consume();
         } else if (config.keybindings().get("next_floating").matches(event)) {
             workspace.nextFloatingPane();
@@ -80,6 +81,20 @@ public final class Main extends Application {
         } else if (config.keybindings().get("close_pane").matches(event)) {
             workspace.closeActivePane();
             event.consume();
+            if (workspace.isEmpty()) {
+                // Closing the last pane quits the app.
+                workspace.close();
+                Platform.exit();
+            }
+        } else if (config.keybindings().get("new_tab").matches(event)) {
+            workspace.newTab();
+            event.consume();
+        } else if (config.keybindings().get("previous_tab").matches(event)) {
+            workspace.previousTab();
+            event.consume();
+        } else if (config.keybindings().get("next_tab").matches(event)) {
+            workspace.nextTab();
+            event.consume();
         } else if (config.keybindings().get("open_font_selector").matches(event)) {
             openFontSelector();
             event.consume();

src/main/java/com/gregor/jprototerm/Tab.java

@@ -0,0 +1,345 @@
+package com.gregor.jprototerm;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ * One tab: an isolated stack of panes (tiled + floating) with its own active pane and
+ * stashed-floating state. {@link TerminalWorkspace} owns the list of tabs and renders only
+ * the current one. Mutating methods return whether they actually changed anything so the
+ * workspace can bump its render version conditionally.
+ */
+final class Tab implements AutoCloseable {
+    private final AppConfig config;
+    private final List<TerminalPane> panes = new ArrayList<>();
+    private int activeIndex;
+    private int hiddenFloatingFocusIndex = -1;
+    private TerminalPane lastFocusedFloating;
+
+    Tab(AppConfig config) {
+        this.config = config;
+        panes.add(openPane(false));
+    }
+
+    TerminalPane activePane() {
+        return panes.get(activeIndex);
+    }
+
+    boolean isEmpty() {
+        return panes.isEmpty();
+    }
+
+    List<TerminalPane> panes() {
+        if (panes.isEmpty()) {
+            return List.of();
+        }
+        List<TerminalPane> visible = panes.stream().filter(TerminalPane::visible).toList();
+        TerminalPane active = activePane();
+        if (!active.visible() || !active.floating()) {
+            return visible;
+        }
+
+        List<TerminalPane> ordered = new ArrayList<>(visible.size());
+        visible.stream()
+                .filter(pane -> pane != active)
+                .forEach(ordered::add);
+        ordered.add(active);
+        return List.copyOf(ordered);
+    }
+
+    boolean isActive(TerminalPane pane) {
+        return !panes.isEmpty() && activePane() == pane;
+    }
+
+    boolean focus(TerminalPane pane) {
+        int index = panes.indexOf(pane);
+        if (index >= 0 && pane.visible() && activeIndex != index) {
+            setActive(index);
+            return true;
+        }
+        return false;
+    }
+
+    void layout(double width, double height, double topInset) {
+        double availHeight = height - topInset;
+        List<TerminalPane> tiled = panes.stream()
+                .filter(TerminalPane::visible)
+                .filter(pane -> !pane.floating())
+                .toList();
+        int tileCount = Math.max(1, tiled.size());
+        double tileWidth = width / tileCount;
+        for (int i = 0; i < tiled.size(); i++) {
+            tiled.get(i).bounds(i * tileWidth, topInset, tileWidth, availHeight);
+        }
+
+        List<TerminalPane> floating = panes.stream()
+                .filter(TerminalPane::visible)
+                .filter(TerminalPane::floating)
+                .toList();
+        for (int i = 0; i < floating.size(); i++) {
+            TerminalPane pane = floating.get(i);
+            double floatingWidth = Math.max(420, width * 0.58);
+            double floatingHeight = Math.max(260, availHeight * 0.58);
+            double offset = i * 28.0;
+            pane.bounds(
+                    Math.min(width - floatingWidth - 12.0, ((width - floatingWidth) / 2.0) + offset),
+                    Math.min(height - floatingHeight - 12.0, topInset + ((availHeight - floatingHeight) / 2.0) + offset),
+                    floatingWidth,
+                    floatingHeight
+            );
+        }
+    }
+
+    boolean navigate(Direction direction) {
+        TerminalPane current = activePane();
+        if (current.floating() && navigateFloatingStack(direction)) {
+            return true;
+        }
+
+        TerminalPane target = panes.stream()
+                .filter(TerminalPane::visible)
+                .filter(pane -> pane != current)
+                .filter(pane -> directionFilter(direction, current, pane))
+                .min(Comparator.comparingDouble(pane -> distance(current, pane)))
+                .orElse(null);
+        if (target != null) {
+            setActive(panes.indexOf(target));
+            return true;
+        }
+        return false;
+    }
+
+    void toggleFloating() {
+        List<TerminalPane> floating = panes.stream()
+                .filter(TerminalPane::floating)
+                .toList();
+        if (floating.isEmpty()) {
+            createFloatingPane();
+            return;
+        }
+
+        boolean anyVisible = floating.stream().anyMatch(TerminalPane::visible);
+        if (anyVisible) {
+            TerminalPane active = activePane();
+            hiddenFloatingFocusIndex = active.floating() ? activeIndex : firstVisibleFloatingIndex();
+            floating.forEach(pane -> pane.setVisible(false));
+            setActive(firstVisibleNonFloatingIndex());
+        } else {
+            floating.forEach(pane -> pane.setVisible(true));
+            setActive(visibleIndexOrFallback(hiddenFloatingFocusIndex, panes.indexOf(floating.get(floating.size() - 1))));
+            hiddenFloatingFocusIndex = -1;
+        }
+    }
+
+    /**
+     * "New pane": adds a floating pane while floating panes are shown, otherwise adds a
+     * tiled pane (the tiled row is redistributed equally by the layout).
+     */
+    void createPane() {
+        if (anyFloatingVisible()) {
+            createFloatingPane();
+        } else {
+            TerminalPane pane = openPane(false);
+            panes.add(pane);
+            setActive(panes.size() - 1);
+        }
+    }
+
+    void nextFloatingPane() {
+        TerminalPane next = nextFloatingAfter(activeIndex);
+        next.setVisible(true);
+        setActive(panes.indexOf(next));
+    }
+
+    void closeActivePane() {
+        TerminalPane active = activePane();
+        int removed = activeIndex;
+        int previous = previousVisibleIndex(removed);
+        panes.remove(removed);
+        if (active == lastFocusedFloating) {
+            lastFocusedFloating = null;
+        }
+        active.close();
+        if (panes.isEmpty()) {
+            activeIndex = 0;
+            return;
+        }
+        activeIndex = adjustIndexAfterRemoval(previous, removed);
+        hiddenFloatingFocusIndex = adjustHiddenFocusAfterRemoval(hiddenFloatingFocusIndex, removed);
+
+        // If the last tiled (main) pane was closed, promote a floating pane to be the new
+        // main pane so the layout has a base and rendering continues normally. Prefer the
+        // most recently focused floating pane.
+        if (panes.stream().noneMatch(pane -> !pane.floating())) {
+            TerminalPane promote = (lastFocusedFloating != null && panes.contains(lastFocusedFloating))
+                    ? lastFocusedFloating
+                    : panes.get(activeIndex);
+            promote.setFloating(false);
+            promote.setVisible(true);
+            activeIndex = panes.indexOf(promote);
+            lastFocusedFloating = null;
+        }
+
+        // If only hidden panes remained, reveal the one we're focusing so the screen isn't
+        // blank.
+        if (!panes.get(activeIndex).visible()) {
+            panes.get(activeIndex).setVisible(true);
+        }
+    }
+
+    private void setActive(int index) {
+        activeIndex = index;
+        if (index >= 0 && index < panes.size() && panes.get(index).floating()) {
+            lastFocusedFloating = panes.get(index);
+        }
+    }
+
+    private void createFloatingPane() {
+        TerminalPane pane = openPane(true);
+        panes.add(pane);
+        setActive(panes.size() - 1);
+    }
+
+    private boolean anyFloatingVisible() {
+        return panes.stream().anyMatch(pane -> pane.floating() && pane.visible());
+    }
+
+    private TerminalPane nextFloatingAfter(int index) {
+        for (int i = index + 1; i < panes.size(); i++) {
+            TerminalPane pane = panes.get(i);
+            if (pane.floating()) {
+                return pane;
+            }
+        }
+        for (int i = 0; i <= index && i < panes.size(); i++) {
+            TerminalPane pane = panes.get(i);
+            if (pane.floating()) {
+                return pane;
+            }
+        }
+        return createAndReturnFloatingPane();
+    }
+
+    private TerminalPane createAndReturnFloatingPane() {
+        TerminalPane pane = openPane(true);
+        panes.add(pane);
+        return pane;
+    }
+
+    private boolean navigateFloatingStack(Direction direction) {
+        List<TerminalPane> floating = panes.stream()
+                .filter(TerminalPane::visible)
+                .filter(TerminalPane::floating)
+                .toList();
+        if (floating.size() < 2) {
+            return false;
+        }
+
+        int current = floating.indexOf(activePane());
+        if (current < 0) {
+            return false;
+        }
+
+        int next = switch (direction) {
+            case LEFT, UP -> current - 1;
+            case DOWN, RIGHT -> current + 1;
+        };
+        if (next < 0 || next >= floating.size()) {
+            return false;
+        }
+
+        setActive(panes.indexOf(floating.get(next)));
+        return true;
+    }
+
+    private int firstVisibleFloatingIndex() {
+        for (int i = 0; i < panes.size(); i++) {
+            TerminalPane pane = panes.get(i);
+            if (pane.visible() && pane.floating()) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    private int firstVisibleNonFloatingIndex() {
+        for (int i = 0; i < panes.size(); i++) {
+            TerminalPane pane = panes.get(i);
+            if (pane.visible() && !pane.floating()) {
+                return i;
+            }
+        }
+        return 0;
+    }
+
+    private int previousVisibleIndex(int index) {
+        for (int i = index - 1; i >= 0; i--) {
+            if (panes.get(i).visible()) {
+                return i;
+            }
+        }
+        for (int i = index + 1; i < panes.size(); i++) {
+            if (panes.get(i).visible()) {
+                return i;
+            }
+        }
+        return firstVisibleNonFloatingIndex();
+    }
+
+    private int visibleIndexOrFallback(int index, int fallback) {
+        if (index >= 0 && index < panes.size() && panes.get(index).visible()) {
+            return index;
+        }
+        return fallback;
+    }
+
+    private static int adjustIndexAfterRemoval(int index, int removedIndex) {
+        if (index < 0) {
+            return 0;
+        }
+        return index > removedIndex ? index - 1 : index;
+    }
+
+    private static int adjustHiddenFocusAfterRemoval(int index, int removedIndex) {
+        if (index < 0 || index == removedIndex) {
+            return -1;
+        }
+        return index > removedIndex ? index - 1 : index;
+    }
+
+    private TerminalPane openPane(boolean floating) {
+        TerminalPane pane = TerminalPane.create(config.columns(), config.rows(), config.maxScrollback());
+        pane.setFloating(floating);
+        pane.attach(ShellSession.start(config.shell(), config.envOverride(), pane, config.columns(), config.rows()));
+        return pane;
+    }
+
+    private static boolean directionFilter(Direction direction, TerminalPane current, TerminalPane candidate) {
+        double currentCenterX = current.x() + current.width() / 2.0;
+        double currentCenterY = current.y() + current.height() / 2.0;
+        double candidateCenterX = candidate.x() + candidate.width() / 2.0;
+        double candidateCenterY = candidate.y() + candidate.height() / 2.0;
+
+        return switch (direction) {
+            case LEFT -> candidateCenterX < currentCenterX;
+            case DOWN -> candidateCenterY > currentCenterY;
+            case UP -> candidateCenterY < currentCenterY;
+            case RIGHT -> candidateCenterX > currentCenterX;
+        };
+    }
+
+    private static double distance(TerminalPane current, TerminalPane candidate) {
+        double dx = (current.x() + current.width() / 2.0) - (candidate.x() + candidate.width() / 2.0);
+        double dy = (current.y() + current.height() / 2.0) - (candidate.y() + candidate.height() / 2.0);
+        return Math.sqrt(dx * dx + dy * dy);
+    }
+
+    @Override
+    public void close() {
+        for (TerminalPane pane : panes) {
+            pane.close();
+        }
+        panes.clear();
+    }
+}

src/main/java/com/gregor/jprototerm/TerminalCanvasView.java

@@ -16,6 +16,7 @@ import dev.jlibghostty.RenderColor;
 import dev.jlibghostty.RenderCursorStyle;
 import dev.jlibghostty.RenderRow;
 import dev.jlibghostty.RenderStateSnapshot;
+import javafx.geometry.VPos;
 import javafx.scene.canvas.Canvas;
 import javafx.scene.canvas.GraphicsContext;
 import javafx.scene.image.Image;
@@ -29,6 +30,7 @@ import javafx.scene.paint.Color;
 import javafx.scene.text.Font;
 import javafx.scene.text.FontSmoothingType;
 import javafx.scene.text.Text;
+import javafx.scene.text.TextAlignment;
 
 import java.io.ByteArrayInputStream;
 import java.util.HashMap;
@@ -38,19 +40,33 @@ import java.util.Map;
 public final class TerminalCanvasView {
     private static final Color DEFAULT_FOREGROUND = Color.rgb(225, 229, 235);
     private static final Color SELECTED_BACKGROUND = Color.rgb(52, 92, 140);
+    // The default cell background (used for cells with no explicit bg, and as the foreground
+    // for reverse-video cells whose background is the terminal default).
+    private static final Color PANE_BACKGROUND = Color.rgb(9, 10, 12);
+    // Canvas background shown wherever no pane covers (gaps, behind nothing once tiled panes
+    // fill the canvas). Painted on a full recomposite.
+    private static final Color GAP_BACKGROUND = Color.rgb(16, 16, 18);
 
     private final Canvas canvas = new Canvas();
     private final TerminalWorkspace workspace;
     private final AppConfig config;
     private final Map<KittyImageKey, Image> kittyImageCache = new HashMap<>();
-    private final Map<TerminalPane, PaneRenderCache> paneRenderCache = new HashMap<>();
+    // Last content version drawn to the canvas per pane, so a content frame repaints only
+    // the panes that actually changed.
+    private final Map<TerminalPane, Long> paneContentVersion = new HashMap<>();
     private String fontFamily;
     private double fontSize;
     private Font cachedFont;
     private FontMetrics cachedMetrics;
     private String cachedFontFamily;
     private double cachedFontSize;
-    private String lastRenderKey;
+    // Cheap per-frame dirty signal: skip the whole render when none of these changed.
+    private double lastWidth = -1.0;
+    private double lastHeight = -1.0;
+    private String lastFontFamily;
+    private double lastFontSize = -1.0;
+    private long lastWorkspaceVersion = Long.MIN_VALUE;
+    private long lastRenderTick = Long.MIN_VALUE;
     private boolean mouseButtonPressed;
     private MouseButton pressedButton = MouseButton.UNKNOWN;
 
@@ -76,144 +92,391 @@ public final class TerminalCanvasView {
         this.fontSize = size;
         cachedFont = null;
         cachedMetrics = null;
-        paneRenderCache.clear();
-        lastRenderKey = null;
+        paneContentVersion.clear();
+        lastWidth = -1.0; // force a redraw on the next frame
     }
 
+    // GhosttyRenderStateDirty values (stable C ABI; see ghostty/vt/render.h).
+    private static final int DIRTY_PARTIAL = 1;
+    private static final int DIRTY_FULL = 2;
+
+    // Thin tab strip shown at the top when more than one tab is open.
+    private static final double TAB_BAR_HEIGHT = 22.0;
+
     public void render() {
         double width = canvas.getWidth();
         double height = canvas.getHeight();
-        workspace.layout(width, height);
+        long workspaceVersion = workspace.version();
+        long renderTick = TerminalPane.renderTick();
+
+        // Two kinds of change: a layout change (size, font, active pane, pane set / z-order)
+        // forces a full recomposite; a content change (renderTick) only repaints the panes
+        // whose terminal content changed. Idle frames — neither — bail out immediately.
+        boolean layoutChanged = width != lastWidth || height != lastHeight
+                || fontSize != lastFontSize || !java.util.Objects.equals(fontFamily, lastFontFamily)
+                || workspaceVersion != lastWorkspaceVersion;
+        boolean contentChanged = renderTick != lastRenderTick;
+        if (!layoutChanged && !contentChanged) {
+            return;
+        }
+        lastWidth = width;
+        lastHeight = height;
+        lastFontFamily = fontFamily;
+        lastFontSize = fontSize;
+        lastWorkspaceVersion = workspaceVersion;
+        lastRenderTick = renderTick;
+
+        double topInset = workspace.tabCount() > 1 ? TAB_BAR_HEIGHT : 0.0;
+        workspace.layout(width, height, topInset);
         Font font = currentFont();
         FontMetrics metrics = currentFontMetrics();
         List<TerminalPane> panes = workspace.panes();
 
-        String renderKey = renderKey(width, height, metrics, panes);
-        if (renderKey.equals(lastRenderKey)) {
-            return;
+        // Apply terminal resizes up front so snapshots reflect current geometry (a no-op
+        // when the grid is unchanged).
+        for (TerminalPane pane : panes) {
+            applyResize(pane, metrics);
         }
-        lastRenderKey = renderKey;
 
         GraphicsContext gc = canvas.getGraphicsContext2D();
-        gc.setFill(Color.rgb(16, 16, 18));
-        gc.fillRect(0, 0, width, height);
         gc.setFontSmoothingType(FontSmoothingType.LCD);
 
-        paneRenderCache.keySet().removeIf(pane -> !panes.contains(pane));
+        if (layoutChanged) {
+            // Recomposite everything onto the retained canvas: clear, then paint panes
+            // bottom-to-top (workspace.panes() puts the active floating pane last == on top).
+            paneContentVersion.keySet().retainAll(panes);
+            gc.setFill(GAP_BACKGROUND);
+            gc.fillRect(0, 0, width, height);
+            if (topInset > 0.0) {
+                drawTabBar(gc, width, topInset);
+            }
             for (TerminalPane pane : panes) {
-            drawPane(gc, pane, font, metrics);
+                paintPane(gc, pane, font, metrics, pane.renderSnapshotFull());
+                paneContentVersion.put(pane, pane.renderVersion());
             }
-    }
-
-    private void drawPane(GraphicsContext gc, TerminalPane pane, Font font, FontMetrics metrics) {
-        if (config.kittyGraphics() && paneHasKittyGraphics(pane)) {
-            paneRenderCache.remove(pane);
-            gc.save();
-            gc.beginPath();
-            gc.rect(pane.x(), pane.y(), pane.width(), pane.height());
-            gc.clip();
-            drawPaneContent(gc, pane, font, metrics, pane.x(), pane.y(), pane.width(), pane.height(), false);
-            gc.restore();
             return;
         }
 
-        PaneRenderCache cache = paneRenderCache.computeIfAbsent(pane, ignored -> new PaneRenderCache());
-        String cacheKey = paneCacheKey(pane, metrics);
-        int imageWidth = Math.max(1, (int) Math.ceil(pane.width()));
-        int imageHeight = Math.max(1, (int) Math.ceil(pane.height()));
-
-        // Allocate the offscreen buffers only when the pane size changes. Reallocating a
-        // full-pane Canvas + WritableImage on every content change churns ~20 MB per frame,
-        // which the native image's serial GC turns into Full-GC frame drops.
-        if (cache.canvas == null || cache.image == null || cache.imageWidth != imageWidth || cache.imageHeight != imageHeight) {
-            cache.canvas = new Canvas(imageWidth, imageHeight);
-            cache.image = new WritableImage(imageWidth, imageHeight);
-            cache.imageWidth = imageWidth;
-            cache.imageHeight = imageHeight;
-            cache.key = null;
+        // Content-only frame: repaint just the panes whose content changed, directly on the
+        // retained canvas, then restore any panes stacked above where they overlap.
+        for (int i = 0; i < panes.size(); i++) {
+            TerminalPane pane = panes.get(i);
+            Long drawn = paneContentVersion.get(pane);
+            if (drawn != null && drawn == pane.renderVersion()) {
+                continue;
+            }
+            repaintPaneContent(gc, panes, i, font, metrics);
+            paneContentVersion.put(pane, pane.renderVersion());
+        }
     }
 
-        // Redraw and re-snapshot into the existing buffers only when content changed.
-        if (!cacheKey.equals(cache.key)) {
-            GraphicsContext cacheGc = cache.canvas.getGraphicsContext2D();
-            cacheGc.clearRect(0, 0, imageWidth, imageHeight);
-            drawPaneContent(cacheGc, pane, font, metrics, 0.0, 0.0, imageWidth, imageHeight, true);
-            cache.canvas.snapshot(null, cache.image);
-            cache.key = cacheKey;
+    private void applyResize(TerminalPane pane, FontMetrics metrics) {
+        int columns = Math.max(1, (int) ((pane.width() - 24.0) / metrics.cellWidth));
+        int rows = Math.max(1, (int) ((pane.height() - 24.0) / metrics.lineHeight));
+        pane.resize(columns, rows, (int) Math.round(metrics.cellWidth), (int) Math.round(metrics.lineHeight));
     }
 
-        gc.drawImage(cache.image, pane.x(), pane.y());
+    // Paint a pane's whole body, clipped to its rect. Used for full recomposites.
+    private void paintPane(GraphicsContext gc, TerminalPane pane, Font font, FontMetrics metrics, RenderStateSnapshot snapshot) {
+        double px = Math.round(pane.x());
+        double py = Math.round(pane.y());
+        gc.save();
+        clipRect(gc, px, py, pane.width(), pane.height());
+        drawPaneContent(gc, pane, font, metrics, snapshot, px, py, pane.width(), pane.height(),
+                config.kittyGraphics() && paneHasKittyGraphics(pane));
+        gc.restore();
     }
 
+    // Repaint one pane whose content changed, then restore the (opaque) panes stacked above
+    // it wherever they overlap the repainted region, so the z-order stays correct.
+    private void repaintPaneContent(GraphicsContext gc, List<TerminalPane> panes, int index, Font font, FontMetrics metrics) {
+        TerminalPane pane = panes.get(index);
+        double px = Math.round(pane.x());
+        double py = Math.round(pane.y());
+        double pw = pane.width();
+        double ph = pane.height();
+        boolean kitty = config.kittyGraphics() && paneHasKittyGraphics(pane);
+
+        double regionY0;
+        double regionY1;
+        gc.save();
+        clipRect(gc, px, py, pw, ph);
+        if (kitty) {
+            drawPaneContent(gc, pane, font, metrics, pane.renderSnapshotFull(), px, py, pw, ph, true);
+            regionY0 = py;
+            regionY1 = py + ph;
+        } else {
+            RenderStateSnapshot snapshot = pane.renderSnapshot();
+            int dirty = snapshot == null ? DIRTY_FULL : snapshot.dirty();
+            if (dirty == DIRTY_FULL) {
+                drawPaneContent(gc, pane, font, metrics, snapshot, px, py, pw, ph, false);
+                regionY0 = py;
+                regionY1 = py + ph;
+            } else if (dirty == DIRTY_PARTIAL) {
+                double[] band = drawDirtyRows(gc, pane, font, metrics, snapshot, px, py, pw, ph);
+                gc.restore();
+                if (band == null) {
+                    return;
+                }
+                restoreStackedAbove(gc, panes, index, font, metrics, px, band[0], pw, band[1] - band[0]);
+                return;
+            } else {
+                gc.restore();
+                return; // dirty == FALSE: nothing visible changed.
+            }
+        }
+        gc.restore();
+        restoreStackedAbove(gc, panes, index, font, metrics, px, regionY0, pw, regionY1 - regionY0);
+    }
+
+    // Redraw any panes above `index` in z-order that intersect the given screen rect, so a
+    // lower pane's repaint doesn't leak through a pane stacked on top of it.
+    private void restoreStackedAbove(GraphicsContext gc, List<TerminalPane> panes, int index,
+            Font font, FontMetrics metrics, double rx, double ry, double rw, double rh) {
+        for (int j = index + 1; j < panes.size(); j++) {
+            TerminalPane above = panes.get(j);
+            double ax = Math.round(above.x());
+            double ay = Math.round(above.y());
+            double ox0 = Math.max(rx, ax);
+            double oy0 = Math.max(ry, ay);
+            double ox1 = Math.min(rx + rw, ax + above.width());
+            double oy1 = Math.min(ry + rh, ay + above.height());
+            if (ox1 <= ox0 || oy1 <= oy0) {
+                continue;
+            }
+            gc.save();
+            clipRect(gc, ox0, oy0, ox1 - ox0, oy1 - oy0);
+            drawPaneContent(gc, above, font, metrics, above.renderSnapshotFull(), ax, ay, above.width(), above.height(),
+                    config.kittyGraphics() && paneHasKittyGraphics(above));
+            gc.restore();
+        }
+    }
+
+    private static void clipRect(GraphicsContext gc, double x, double y, double width, double height) {
+        gc.beginPath();
+        gc.rect(x, y, width, height);
+        gc.clip();
+    }
+
+    // Thin tab strip: one equal-width segment per tab, the current one highlighted, with a
+    // small 1-based number centred in each segment.
+    private void drawTabBar(GraphicsContext gc, double width, double barHeight) {
+        int count = workspace.tabCount();
+        int currentIndex = workspace.currentTabIndex();
+        Font barFont = Font.font(fontFamily, Math.max(9.0, Math.min(13.0, barHeight * 0.62)));
+        gc.setFont(barFont);
+        gc.setFontSmoothingType(FontSmoothingType.GRAY);
+        gc.setTextAlign(TextAlignment.CENTER);
+        gc.setTextBaseline(VPos.CENTER);
+
+        double gap = 1.0;
+        double segmentWidth = width / count;
+        for (int i = 0; i < count; i++) {
+            double x = i * segmentWidth;
+            boolean current = i == currentIndex;
+            gc.setFill(current ? Color.rgb(45, 55, 72) : Color.rgb(22, 24, 28));
+            gc.fillRect(x, 0.0, segmentWidth - gap, barHeight);
+            gc.setFill(current ? DEFAULT_FOREGROUND : Color.rgb(128, 136, 148));
+            gc.fillText(Integer.toString(i + 1), x + (segmentWidth - gap) / 2.0, barHeight / 2.0);
+        }
+
+        // Restore the defaults the cell renderer relies on (left-aligned, baseline, LCD).
+        gc.setTextAlign(TextAlignment.LEFT);
+        gc.setTextBaseline(VPos.BASELINE);
+        gc.setFontSmoothingType(FontSmoothingType.LCD);
+    }
+
+    // Full content render: background, border, all rows, cursor, and (when enabled) kitty
+    // graphics. Used by the kitty direct path and by full offscreen redraws.
     private void drawPaneContent(
             GraphicsContext gc,
             TerminalPane pane,
             Font font,
             FontMetrics metrics,
+            RenderStateSnapshot snapshot,
             double x,
             double y,
             double width,
             double height,
-            boolean clear
+            boolean withKitty
     ) {
-        if (clear) {
-            gc.clearRect(x, y, width, height);
-        }
         gc.setFontSmoothingType(FontSmoothingType.LCD);
-        if (pane.floating()) {
-            gc.setGlobalAlpha(0.96);
-        }
-        gc.setFill(Color.rgb(9, 10, 12));
+        gc.setFill(PANE_BACKGROUND);
         gc.fillRect(x, y, width, height);
-        gc.setGlobalAlpha(1.0);
-
-        gc.setStroke(workspace.isActive(pane) ? Color.rgb(87, 166, 255) : Color.rgb(52, 57, 65));
-        gc.setLineWidth(workspace.isActive(pane) ? 2.0 : 1.0);
-        gc.strokeRect(x + 0.5, y + 0.5, width - 1.0, height - 1.0);
-
         gc.setFont(font);
 
-        int columns = Math.max(1, (int) ((width - 24.0) / metrics.cellWidth));
-        int rows = Math.max(1, (int) ((height - 24.0) / metrics.lineHeight));
-        pane.resize(columns, rows, (int) Math.round(metrics.cellWidth), (int) Math.round(metrics.lineHeight));
-
         double left = x + 12.0;
         double top = y + 12.0;
         double baseline = top + metrics.baselineOffset;
 
-        RenderStateSnapshot snapshot = pane.renderSnapshot();
-        Map<KittyPlaceholderKey, KittyPlaceholderBounds> placeholderBounds = config.kittyGraphics()
+        Map<KittyPlaceholderKey, KittyPlaceholderBounds> placeholderBounds = withKitty
                 ? kittyPlaceholderBounds(snapshot)
                 : Map.of();
 
-        if (config.kittyGraphics()) {
+        if (withKitty) {
             drawKittyGraphics(gc, pane, KittyPlacementLayer.BELOW_TEXT, placeholderBounds, left, top, metrics.cellWidth, metrics.lineHeight);
         }
 
         if (snapshot != null) {
+            double contentBottom = top + snapshot.rows() * metrics.lineHeight;
+            fillVerticalPadding(gc, snapshot, x, y, width, height, top, contentBottom);
             for (RenderRow row : snapshot.renderRows()) {
+                double y0 = Math.floor(top + (row.row() * metrics.lineHeight));
+                double y1 = Math.ceil(top + ((row.row() + 1) * metrics.lineHeight));
+                paintSidePadding(gc, row, x, width, left, metrics.cellWidth, y0, y1 - y0);
                 drawRow(gc, row, left, top, baseline, metrics.cellWidth, metrics.lineHeight);
             }
-        }
-
-        if (snapshot != null) {
             drawCursor(gc, snapshot, left, top, metrics.cellWidth, metrics.lineHeight);
         }
 
-        if (config.kittyGraphics()) {
+        if (withKitty) {
             drawKittyGraphics(gc, pane, KittyPlacementLayer.ABOVE_TEXT, placeholderBounds, left, top, metrics.cellWidth, metrics.lineHeight);
         }
+
+        drawBorder(gc, pane, x, y, width, height);
+    }
+
+    // Effective background colour of a cell as it is drawn (reverse video swaps fg/bg, an
+    // unset colour falls back to the defaults).
+    private static Color cellBackgroundColor(RenderCell cell) {
+        if (cell.inverse()) {
+            var fg = cell.foreground();
+            return fg.isPresent() ? toFxColor(fg.get()) : DEFAULT_FOREGROUND;
+        }
+        var bg = cell.background();
+        return bg.isPresent() ? toFxColor(bg.get()) : PANE_BACKGROUND;
+    }
+
+    private static Color rowEdgeBackground(RenderRow row, boolean firstCell) {
+        List<RenderCell> cells = row.cells();
+        if (cells.isEmpty()) {
+            return PANE_BACKGROUND;
+        }
+        return cellBackgroundColor(firstCell ? cells.get(0) : cells.get(cells.size() - 1));
+    }
+
+    // Extend the row's edge-cell backgrounds into the left/right padding (the 12px margin and
+    // the right-edge rounding sliver), so the unused space matches the rendered content.
+    private void paintSidePadding(GraphicsContext gc, RenderRow row, double paneX, double paneWidth,
+            double contentLeft, double cellWidth, double yTop, double bandHeight) {
+        int columns = row.cells().size();
+        if (columns == 0) {
+            return;
+        }
+        double contentRight = contentLeft + (columns * cellWidth);
+        gc.setFill(rowEdgeBackground(row, true));
+        gc.fillRect(paneX, yTop, contentLeft - paneX, bandHeight);
+        gc.setFill(rowEdgeBackground(row, false));
+        gc.fillRect(contentRight, yTop, paneX + paneWidth - contentRight, bandHeight);
+    }
+
+    // Fill the top/bottom padding strips with the top/bottom row's edge colour.
+    private void fillVerticalPadding(GraphicsContext gc, RenderStateSnapshot snapshot,
+            double paneX, double paneY, double paneWidth, double paneHeight, double contentTop, double contentBottom) {
+        List<RenderRow> rows = snapshot.renderRows();
+        if (rows.isEmpty()) {
+            return;
+        }
+        gc.setFill(rowEdgeBackground(rows.get(0), true));
+        gc.fillRect(paneX, paneY, paneWidth, contentTop - paneY);
+        gc.setFill(rowEdgeBackground(rows.get(rows.size() - 1), true));
+        gc.fillRect(paneX, contentBottom, paneWidth, paneY + paneHeight - contentBottom);
+    }
+
+    // Incremental render: repaint only the rows ghostty flagged dirty, at the pane's screen
+    // origin, then restore the cursor and border. Returns the screen-space [minY, maxY] band
+    // that was repainted (for restoring panes stacked above), or null if nothing was dirty.
+    private double[] drawDirtyRows(
+            GraphicsContext gc,
+            TerminalPane pane,
+            Font font,
+            FontMetrics metrics,
+            RenderStateSnapshot snapshot,
+            double px,
+            double py,
+            double pw,
+            double ph
+    ) {
+        gc.setFontSmoothingType(FontSmoothingType.LCD);
+        gc.setFont(font);
+        double left = px + 12.0;
+        double top = py + 12.0;
+        double baseline = top + metrics.baselineOffset;
+
+        double contentBottom = top + snapshot.rows() * metrics.lineHeight;
+        int lastRow = snapshot.rows() - 1;
+        boolean cursorRowDirty = false;
+        double bandMin = Double.POSITIVE_INFINITY;
+        double bandMax = Double.NEGATIVE_INFINITY;
+        for (RenderRow row : snapshot.renderRows()) {
+            if (!row.dirty()) {
+                continue;
+            }
+            // Snap the row band to integer pixels and paint opaque: a fractional-height fill
+            // would leave sub-pixel seams between rows.
+            double y0 = Math.floor(top + (row.row() * metrics.lineHeight));
+            double y1 = Math.ceil(top + ((row.row() + 1) * metrics.lineHeight));
+            gc.setFill(PANE_BACKGROUND);
+            gc.fillRect(px, y0, pw, y1 - y0);
+            paintSidePadding(gc, row, px, pw, left, metrics.cellWidth, y0, y1 - y0);
+            drawRow(gc, row, left, top, baseline, metrics.cellWidth, metrics.lineHeight);
+            bandMin = Math.min(bandMin, y0);
+            bandMax = Math.max(bandMax, y1);
+            // Edge rows also own the top/bottom padding strip; repaint it and extend the
+            // band so panes stacked above get restored over it too.
+            if (row.row() == 0) {
+                gc.setFill(rowEdgeBackground(row, true));
+                gc.fillRect(px, py, pw, top - py);
+                bandMin = Math.min(bandMin, py);
+            }
+            if (row.row() == lastRow) {
+                gc.setFill(rowEdgeBackground(row, true));
+                gc.fillRect(px, contentBottom, pw, py + ph - contentBottom);
+                bandMax = Math.max(bandMax, py + ph);
+            }
+            if (snapshot.cursorViewportHasValue() && row.row() == snapshot.cursorViewportY()) {
+                cursorRowDirty = true;
+            }
+        }
+        if (bandMin > bandMax) {
+            return null;
+        }
+
+        // The cursor overlays its cell; redraw it only when its row was repainted, so we
+        // neither leave a stale cursor nor stack the translucent overlay on itself.
+        if (cursorRowDirty) {
+            drawCursor(gc, snapshot, left, top, metrics.cellWidth, metrics.lineHeight);
+        }
+        // Repainting rows clears the side borders within the band; restore just those
+        // segments. Clipping to the band is important: the full border rectangle extends
+        // outside the repainted region, and only the band gets restored over panes stacked
+        // above — an unclipped stroke would leave this pane's outline on top of them.
+        gc.save();
+        clipRect(gc, px, bandMin, pw, bandMax - bandMin);
+        drawBorder(gc, pane, px, py, pw, ph);
+        gc.restore();
+        return new double[] {bandMin, bandMax};
+    }
+
+    private void drawBorder(GraphicsContext gc, TerminalPane pane, double x, double y, double width, double height) {
+        gc.setStroke(workspace.isActive(pane) ? Color.rgb(87, 166, 255) : Color.rgb(52, 57, 65));
+        gc.setLineWidth(workspace.isActive(pane) ? 2.0 : 1.0);
+        gc.strokeRect(x + 0.5, y + 0.5, width - 1.0, height - 1.0);
     }
 
     private static FontMetrics measureFontMetrics(Font font) {
         Text text = new Text("┃MgÅjy");
         text.setFont(font);
-        double lineHeight = Math.max(1.0, text.getLayoutBounds().getHeight());
+        // Snap the cell size to whole pixels so cells tile on integer boundaries. Fractional
+        // cell metrics put every cell edge on a sub-pixel position, leaving anti-aliased
+        // seams that show up as a faint grid behind the themed cell backgrounds. Rounding
+        // leaves a few pixels of unused space at the right/bottom edge, which is fine.
+        double lineHeight = Math.max(1.0, Math.round(text.getLayoutBounds().getHeight()));
         double baselineOffset = -text.getLayoutBounds().getMinY();
 
         Text cell = new Text("M");
         cell.setFont(font);
-        double cellWidth = Math.max(1.0, cell.getLayoutBounds().getWidth());
+        double cellWidth = Math.max(1.0, Math.round(cell.getLayoutBounds().getWidth()));
         return new FontMetrics(cellWidth, lineHeight, baselineOffset);
     }
 
@@ -234,40 +497,9 @@ public final class TerminalCanvasView {
         return cachedMetrics;
     }
 
-    private String renderKey(double width, double height, FontMetrics metrics, List<TerminalPane> panes) {
-        StringBuilder builder = new StringBuilder();
-        builder.append(width).append(':')
-                .append(height).append(':')
-                .append(workspace.version()).append(':')
-                .append(fontFamily).append(':')
-                .append(fontSize).append(':')
-                .append(metrics.cellWidth).append(':')
-                .append(metrics.lineHeight);
-        for (TerminalPane pane : panes) {
-            builder.append('|')
-                    .append(System.identityHashCode(pane)).append(',')
-                    .append(pane.renderVersion()).append(',')
-                    .append(workspace.isActive(pane)).append(',')
-                    .append(pane.x()).append(',')
-                    .append(pane.y()).append(',')
-                    .append(pane.width()).append(',')
-                    .append(pane.height());
-        }
-        return builder.toString();
-    }
-
-    private String paneCacheKey(TerminalPane pane, FontMetrics metrics) {
-        return pane.renderVersion()
-                + ":" + workspace.isActive(pane)
-                + ":" + pane.width()
-                + ":" + pane.height()
-                + ":" + fontFamily
-                + ":" + fontSize
-                + ":" + metrics.cellWidth
-                + ":" + metrics.lineHeight
-                + ":" + config.kittyGraphics();
-    }
-
+    // Layout identity of a pane: everything that forces a redraw EXCEPT terminal content
+    // (which is tracked separately by renderVersion). Deliberately omits renderVersion so
+    // content changes go through the incremental dirty-row path instead of a full redraw.
     private static Map<KittyPlaceholderKey, KittyPlaceholderBounds> kittyPlaceholderBounds(RenderStateSnapshot snapshot) {
         if (snapshot == null) {
             return Map.of();
@@ -475,10 +707,26 @@ public final class TerminalCanvasView {
 
             double x = left + (cell.column() * cellWidth);
             double cellTop = top + (row.row() * lineHeight);
-            cell.background().ifPresent(background -> {
-                gc.setFill(toFxColor(background));
+
+            // Resolve fg/bg (null bg = terminal default, painted by the pane background).
+            // Avoid Optional.map's allocation on this hot path.
+            var fgOpt = cell.foreground();
+            var bgOpt = cell.background();
+            Color fg = fgOpt.isPresent() ? toFxColor(fgOpt.get()) : DEFAULT_FOREGROUND;
+            Color bg = bgOpt.isPresent() ? toFxColor(bgOpt.get()) : null;
+
+            // Reverse video: ghostty does not bake inverse into the resolved colours, so we
+            // swap them here, falling back to the terminal defaults for whichever is unset.
+            if (cell.inverse()) {
+                Color swappedBg = fg;
+                fg = (bg != null) ? bg : PANE_BACKGROUND;
+                bg = swappedBg;
+            }
+
+            if (bg != null) {
+                gc.setFill(bg);
                 gc.fillRect(x, cellTop, cellWidth, lineHeight);
-            });
+            }
             if (cell.selected()) {
                 gc.setFill(SELECTED_BACKGROUND);
                 gc.fillRect(x, cellTop, cellWidth, lineHeight);
@@ -488,14 +736,28 @@ public final class TerminalCanvasView {
             }
 
             double y = baseline + (row.row() * lineHeight);
-            Color foreground = cell.foreground().map(TerminalCanvasView::toFxColor).orElse(DEFAULT_FOREGROUND);
-            gc.setFill(foreground);
+            gc.setFill(fg);
             gc.fillText(cell.text(), x, y);
         }
     }
 
+    // A full-screen redraw asks for one Color per cell; most cells share a handful of
+    // colors, so cache them by packed RGB instead of allocating a Color each time. Bounded
+    // so a truecolor gradient can't grow it without limit.
+    private static final Map<Integer, Color> COLOR_CACHE = new HashMap<>();
+
     private static Color toFxColor(RenderColor color) {
-        return Color.rgb(color.red(), color.green(), color.blue());
+        int key = (color.red() << 16) | (color.green() << 8) | color.blue();
+        Color cached = COLOR_CACHE.get(key);
+        if (cached != null) {
+            return cached;
+        }
+        if (COLOR_CACHE.size() >= 4096) {
+            COLOR_CACHE.clear();
+        }
+        Color created = Color.rgb(color.red(), color.green(), color.blue());
+        COLOR_CACHE.put(key, created);
+        return created;
     }
 
     private static void drawCursor(GraphicsContext gc, RenderStateSnapshot snapshot, double left, double top, double cellWidth, double lineHeight) {
@@ -718,7 +980,12 @@ public final class TerminalCanvasView {
     private record MouseTarget(MouseEncoderSize size, long screenWidth, long screenHeight) {
     }
 
-    private record KittyImageKey(long id, long number, long width, long height, KittyImageFormat format, int dataLength, long fingerprint) {
+    // A kitty image is immutable for a given (id, number); re-transmitting under the same
+    // id changes the number (and the snapshot below evicts stale entries by id anyway). So
+    // the identity + dimensions + payload length are enough to key the decoded-image cache,
+    // and we avoid fingerprinting the whole payload — which previously ran once per frame
+    // per placement (O(image size)) just to look the image up.
+    private record KittyImageKey(long id, long number, long width, long height, KittyImageFormat format, int dataLength) {
         private static KittyImageKey of(KittyImageSnapshot snapshot, byte[] data) {
             return new KittyImageKey(
                     snapshot.id(),
@@ -726,19 +993,9 @@ public final class TerminalCanvasView {
                     snapshot.width(),
                     snapshot.height(),
                     snapshot.format(),
-                    data.length,
-                    fingerprint(data)
+                    data.length
             );
         }
-
-        private static long fingerprint(byte[] data) {
-            long hash = 0xcbf29ce484222325L;
-            for (byte value : data) {
-                hash ^= Byte.toUnsignedInt(value);
-                hash *= 0x100000001b3L;
-            }
-            return hash;
-        }
     }
 
     private record KittyPlaceholderKey(long imageId, long placementId) {
@@ -788,12 +1045,4 @@ public final class TerminalCanvasView {
             return maxSourceColumn - minSourceColumn + 1;
         }
     }
-
-    private static final class PaneRenderCache {
-        private Canvas canvas;
-        private WritableImage image;
-        private int imageWidth;
-        private int imageHeight;
-        private String key;
-    }
 }

src/main/java/com/gregor/jprototerm/TerminalPane.java

@@ -6,6 +6,7 @@ import dev.jlibghostty.MouseAction;
 import dev.jlibghostty.MouseEncoder;
 import dev.jlibghostty.MouseEncoderSize;
 import dev.jlibghostty.MouseInput;
+import dev.jlibghostty.RenderState;
 import dev.jlibghostty.RenderStateSnapshot;
 import dev.jlibghostty.ScrollViewport;
 import dev.jlibghostty.Terminal;
@@ -13,12 +14,23 @@ import dev.jlibghostty.TerminalOptions;
 import dev.jlibghostty.DeviceAttributes;
 
 import java.util.Optional;
-import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.atomic.AtomicLong;
 
 public final class TerminalPane implements AutoCloseable {
+    // Monotonic across all panes, bumped on every content change. Lets the renderer detect
+    // "nothing changed" in O(1) without scanning panes or building a render key.
+    private static final AtomicLong RENDER_TICK = new AtomicLong();
+
+    public static long renderTick() {
+        return RENDER_TICK.get();
+    }
+
     private final Terminal terminal;
     private final MouseEncoder mouseEncoder = new MouseEncoder();
-    private final AtomicReference<RenderStateSnapshot> renderSnapshot = new AtomicReference<>();
+    // A persistent render state (reused across frames) is what makes ghostty's per-row
+    // dirty tracking meaningful: update() accumulates dirty since the last resetDirty().
+    private final RenderState renderState = new RenderState();
+    private RenderStateSnapshot cachedSnapshot;
     private ShellSession session;
     private boolean floating;
     private boolean visible = true;
@@ -31,6 +43,7 @@ public final class TerminalPane implements AutoCloseable {
     private int pixelWidth;
     private int pixelHeight;
     private long renderVersion;
+    private long snapshotVersion = -1;
 
     private TerminalPane(Terminal terminal, int columns, int rows) {
         this.terminal = terminal;
@@ -111,8 +124,39 @@ public final class TerminalPane implements AutoCloseable {
         }
     }
 
+    /**
+     * Incremental snapshot: cells are marshalled only for rows that changed since the last
+     * frame (global dirty == PARTIAL), reused across calls for the same content version.
+     * Snapshotting is deferred here rather than done in refresh(), so a burst of writes
+     * between two frames collapses into a single snapshot.
+     */
     public RenderStateSnapshot renderSnapshot() {
-        return renderSnapshot.get();
+        return snapshot(false);
+    }
+
+    /**
+     * Full snapshot with every row's cells populated. Used where the whole pane is redrawn
+     * regardless of dirty state (the kitty-graphics path).
+     */
+    public RenderStateSnapshot renderSnapshotFull() {
+        return snapshot(true);
+    }
+
+    private RenderStateSnapshot snapshot(boolean full) {
+        synchronized (terminal) {
+            if (full) {
+                renderState.update(terminal);
+                cachedSnapshot = renderState.snapshot();
+                renderState.resetDirty();
+                snapshotVersion = renderVersion;
+            } else if (snapshotVersion != renderVersion) {
+                renderState.update(terminal);
+                cachedSnapshot = renderState.snapshotIncremental();
+                renderState.resetDirty();
+                snapshotVersion = renderVersion;
+            }
+            return cachedSnapshot;
+        }
     }
 
     public String scrollbackText() {
@@ -192,8 +236,10 @@ public final class TerminalPane implements AutoCloseable {
     }
 
     private void refresh() {
-        renderSnapshot.set(terminal.renderSnapshot());
+        // Only mark the pane dirty; the snapshot itself is computed lazily in
+        // renderSnapshot() so a burst of writes collapses into a single snapshot per frame.
         renderVersion++;
+        RENDER_TICK.incrementAndGet();
     }
 
     @Override
@@ -203,6 +249,7 @@ public final class TerminalPane implements AutoCloseable {
             session = null;
         }
         mouseEncoder.close();
+        renderState.close();
         terminal.close();
     }
 }

src/main/java/com/gregor/jprototerm/TerminalWorkspace.java

@@ -1,293 +1,139 @@
 package com.gregor.jprototerm;
 
 import java.util.ArrayList;
-import java.util.Comparator;
 import java.util.List;
 
+/**
+ * Holds the tabs and renders only the current one. Pane operations delegate to the current
+ * tab; tab operations switch which tab is current. A single render version bumps on any
+ * change (intra-tab or tab switch) so the renderer recomposites when needed.
+ */
 public final class TerminalWorkspace implements AutoCloseable {
     private final AppConfig config;
-    private final List<TerminalPane> panes = new ArrayList<>();
-    private int activeIndex;
-    private int hiddenFloatingFocusIndex = -1;
+    private final List<Tab> tabs = new ArrayList<>();
+    private int currentTab;
     private long version;
 
     public TerminalWorkspace(AppConfig config) {
         this.config = config;
-        panes.add(openPane(false));
+        tabs.add(new Tab(config));
     }
 
-    public TerminalPane activePane() {
-        return panes.get(activeIndex);
-    }
-
-    public List<TerminalPane> panes() {
-        List<TerminalPane> visible = panes.stream().filter(TerminalPane::visible).toList();
-        TerminalPane active = activePane();
-        if (!active.visible() || !active.floating()) {
-            return visible;
-        }
-
-        List<TerminalPane> ordered = new ArrayList<>(visible.size());
-        visible.stream()
-                .filter(pane -> pane != active)
-                .forEach(ordered::add);
-        ordered.add(active);
-        return List.copyOf(ordered);
-    }
-
-    public boolean isActive(TerminalPane pane) {
-        return activePane() == pane;
+    private Tab current() {
+        return tabs.get(currentTab);
     }
 
     public long version() {
         return version;
     }
 
+    public boolean isEmpty() {
+        return tabs.isEmpty();
+    }
+
+    public TerminalPane activePane() {
+        return current().activePane();
+    }
+
+    public List<TerminalPane> panes() {
+        return tabs.isEmpty() ? List.of() : current().panes();
+    }
+
+    public boolean isActive(TerminalPane pane) {
+        return !tabs.isEmpty() && current().isActive(pane);
+    }
+
+    public void layout(double width, double height, double topInset) {
+        if (!tabs.isEmpty()) {
+            current().layout(width, height, topInset);
+        }
+    }
+
+    public int tabCount() {
+        return tabs.size();
+    }
+
+    public int currentTabIndex() {
+        return currentTab;
+    }
+
     public void focus(TerminalPane pane) {
-        int index = panes.indexOf(pane);
-        if (index >= 0 && pane.visible() && activeIndex != index) {
-            activeIndex = index;
+        if (!tabs.isEmpty() && current().focus(pane)) {
             version++;
         }
     }
 
-    public void layout(double width, double height) {
-        List<TerminalPane> tiled = panes.stream()
-                .filter(TerminalPane::visible)
-                .filter(pane -> !pane.floating())
-                .toList();
-        int tileCount = Math.max(1, tiled.size());
-        double tileWidth = width / tileCount;
-        for (int i = 0; i < tiled.size(); i++) {
-            tiled.get(i).bounds(i * tileWidth, 0, tileWidth, height);
-        }
-
-        List<TerminalPane> floating = panes.stream()
-                .filter(TerminalPane::visible)
-                .filter(TerminalPane::floating)
-                .toList();
-        for (int i = 0; i < floating.size(); i++) {
-            TerminalPane pane = floating.get(i);
-            if (pane.visible() && pane.floating()) {
-                double floatingWidth = Math.max(420, width * 0.58);
-                double floatingHeight = Math.max(260, height * 0.58);
-                double offset = i * 28.0;
-                pane.bounds(
-                        Math.min(width - floatingWidth - 12.0, ((width - floatingWidth) / 2.0) + offset),
-                        Math.min(height - floatingHeight - 12.0, ((height - floatingHeight) / 2.0) + offset),
-                        floatingWidth,
-                        floatingHeight
-                );
-            }
-        }
-    }
-
     public void navigate(Direction direction) {
-        TerminalPane current = activePane();
-        if (current.floating() && navigateFloatingStack(direction)) {
+        if (!tabs.isEmpty() && current().navigate(direction)) {
             version++;
-            return;
         }
-
-        panes.stream()
-                .filter(TerminalPane::visible)
-                .filter(pane -> pane != current)
-                .filter(pane -> directionFilter(direction, current, pane))
-                .min(Comparator.comparingDouble(pane -> distance(current, pane)))
-                .ifPresent(pane -> {
-                    activeIndex = panes.indexOf(pane);
-                    version++;
-                });
     }
 
     public void toggleFloating() {
-        List<TerminalPane> floating = panes.stream()
-                .filter(TerminalPane::floating)
-                .toList();
-        if (floating.isEmpty()) {
-            createFloatingPane();
+        if (tabs.isEmpty()) {
             return;
         }
-
-        boolean anyVisible = floating.stream().anyMatch(TerminalPane::visible);
-        if (anyVisible) {
-            TerminalPane active = activePane();
-            hiddenFloatingFocusIndex = active.floating() ? activeIndex : firstVisibleFloatingIndex();
-            floating.forEach(pane -> pane.setVisible(false));
-            activeIndex = firstVisibleNonFloatingIndex();
-            version++;
-        } else {
-            floating.forEach(pane -> pane.setVisible(true));
-            activeIndex = visibleIndexOrFallback(hiddenFloatingFocusIndex, panes.indexOf(floating.get(floating.size() - 1)));
-            hiddenFloatingFocusIndex = -1;
+        current().toggleFloating();
         version++;
     }
-    }
 
-    public void createFloatingPane() {
-        TerminalPane pane = openPane(true);
-        panes.add(pane);
-        activeIndex = panes.size() - 1;
+    public void createPane() {
+        if (tabs.isEmpty()) {
+            return;
+        }
+        current().createPane();
         version++;
     }
 
     public void nextFloatingPane() {
-        TerminalPane next = nextFloatingAfter(activeIndex);
-        next.setVisible(true);
-        activeIndex = panes.indexOf(next);
+        if (tabs.isEmpty()) {
+            return;
+        }
+        current().nextFloatingPane();
         version++;
     }
 
     public void closeActivePane() {
-        TerminalPane active = activePane();
-        if (!active.floating() || panes.stream().filter(pane -> !pane.floating()).count() == 0) {
+        if (tabs.isEmpty()) {
             return;
         }
-
-        int removed = activeIndex;
-        int previous = previousVisibleIndex(removed);
-        panes.remove(removed);
-        active.close();
-        activeIndex = adjustIndexAfterRemoval(previous, removed);
-        hiddenFloatingFocusIndex = adjustHiddenFocusAfterRemoval(hiddenFloatingFocusIndex, removed);
+        current().closeActivePane();
+        if (current().isEmpty()) {
+            // Closing a tab's last pane closes the tab. When no tabs remain the workspace
+            // is empty and Main quits.
+            tabs.remove(currentTab);
+            if (currentTab >= tabs.size()) {
+                currentTab = Math.max(0, tabs.size() - 1);
+            }
+        }
         version++;
     }
 
-    private TerminalPane nextFloatingAfter(int index) {
-        for (int i = index + 1; i < panes.size(); i++) {
-            TerminalPane pane = panes.get(i);
-            if (pane.floating()) {
-                return pane;
-            }
-        }
-        for (int i = 0; i <= index && i < panes.size(); i++) {
-            TerminalPane pane = panes.get(i);
-            if (pane.floating()) {
-                return pane;
-            }
-        }
-        return createAndReturnFloatingPane();
+    public void newTab() {
+        tabs.add(new Tab(config));
+        currentTab = tabs.size() - 1;
+        version++;
     }
 
-    private TerminalPane createAndReturnFloatingPane() {
-        TerminalPane pane = openPane(true);
-        panes.add(pane);
-        return pane;
+    public void nextTab() {
+        if (tabs.size() > 1) {
+            currentTab = (currentTab + 1) % tabs.size();
+            version++;
+        }
     }
 
-    private boolean navigateFloatingStack(Direction direction) {
-        List<TerminalPane> floating = panes.stream()
-                .filter(TerminalPane::visible)
-                .filter(TerminalPane::floating)
-                .toList();
-        if (floating.size() < 2) {
-            return false;
+    public void previousTab() {
+        if (tabs.size() > 1) {
+            currentTab = (currentTab - 1 + tabs.size()) % tabs.size();
+            version++;
         }
-
-        int current = floating.indexOf(activePane());
-        if (current < 0) {
-            return false;
-        }
-
-        int next = switch (direction) {
-            case LEFT, UP -> current - 1;
-            case DOWN, RIGHT -> current + 1;
-        };
-        if (next < 0 || next >= floating.size()) {
-            return false;
-        }
-
-        activeIndex = panes.indexOf(floating.get(next));
-        return true;
-    }
-
-    private int firstVisibleFloatingIndex() {
-        for (int i = 0; i < panes.size(); i++) {
-            TerminalPane pane = panes.get(i);
-            if (pane.visible() && pane.floating()) {
-                return i;
-            }
-        }
-        return -1;
-    }
-
-    private int firstVisibleNonFloatingIndex() {
-        for (int i = 0; i < panes.size(); i++) {
-            TerminalPane pane = panes.get(i);
-            if (pane.visible() && !pane.floating()) {
-                return i;
-            }
-        }
-        return 0;
-    }
-
-    private int previousVisibleIndex(int index) {
-        for (int i = index - 1; i >= 0; i--) {
-            if (panes.get(i).visible()) {
-                return i;
-            }
-        }
-        for (int i = index + 1; i < panes.size(); i++) {
-            if (panes.get(i).visible()) {
-                return i;
-            }
-        }
-        return firstVisibleNonFloatingIndex();
-    }
-
-    private int visibleIndexOrFallback(int index, int fallback) {
-        if (index >= 0 && index < panes.size() && panes.get(index).visible()) {
-            return index;
-        }
-        return fallback;
-    }
-
-    private static int adjustIndexAfterRemoval(int index, int removedIndex) {
-        if (index < 0) {
-            return 0;
-        }
-        return index > removedIndex ? index - 1 : index;
-    }
-
-    private static int adjustHiddenFocusAfterRemoval(int index, int removedIndex) {
-        if (index < 0 || index == removedIndex) {
-            return -1;
-        }
-        return index > removedIndex ? index - 1 : index;
-    }
-
-    private TerminalPane openPane(boolean floating) {
-        TerminalPane pane = TerminalPane.create(config.columns(), config.rows(), config.maxScrollback());
-        pane.setFloating(floating);
-        pane.attach(ShellSession.start(config.shell(), config.envOverride(), pane, config.columns(), config.rows()));
-        return pane;
-    }
-
-    private static boolean directionFilter(Direction direction, TerminalPane current, TerminalPane candidate) {
-        double currentCenterX = current.x() + current.width() / 2.0;
-        double currentCenterY = current.y() + current.height() / 2.0;
-        double candidateCenterX = candidate.x() + candidate.width() / 2.0;
-        double candidateCenterY = candidate.y() + candidate.height() / 2.0;
-
-        return switch (direction) {
-            case LEFT -> candidateCenterX < currentCenterX;
-            case DOWN -> candidateCenterY > currentCenterY;
-            case UP -> candidateCenterY < currentCenterY;
-            case RIGHT -> candidateCenterX > currentCenterX;
-        };
-    }
-
-    private static double distance(TerminalPane current, TerminalPane candidate) {
-        double dx = (current.x() + current.width() / 2.0) - (candidate.x() + candidate.width() / 2.0);
-        double dy = (current.y() + current.height() / 2.0) - (candidate.y() + candidate.height() / 2.0);
-        return Math.sqrt(dx * dx + dy * dy);
     }
 
     @Override
     public void close() {
-        for (TerminalPane pane : panes) {
-            pane.close();
+        for (Tab tab : tabs) {
+            tab.close();
         }
-        panes.clear();
+        tabs.clear();
     }
 }