thinner borders

README.md

@@ -62,6 +62,57 @@ gradle run
 
 The Gradle project is the source of truth for the JavaFX build.
 
+## Daemon (optional, faster launches)
+
+Cold start pays for JVM + JavaFX + GL/X11 init every time. The optional daemon keeps one JVM
+(one toolkit) running and hosts every window in it, so a `jprototerm` launch just asks the
+daemon to open a window — it appears without paying that startup cost again.
+
+Run it once in the background:
+
+```sh
+jprototerm --daemon &
+```
+
+After that, a bare `jprototerm` connects to the daemon and opens a window in the current
+directory. If no daemon is running, `jprototerm` falls back to a standalone in-process window
+(today's behavior), so it always works.
+
+For development testing, use `jprototerm --standalone` to skip the daemon even when one is
+running.
+
+To start the daemon automatically with your graphical session, enable the bundled **user**
+service (it's a user service, not a system one, because X11 needs a display — which only
+exists after you log in):
+
+```sh
+mkdir -p ~/.config/systemd/user
+ln -sf "$(dirname "$(readlink -f "$(command -v jprototerm)")")/../share/systemd/user/jprototerm.service" \
+  ~/.config/systemd/user/jprototerm.service
+systemctl --user enable --now jprototerm.service
+```
+After upgrading via nix profile upgrade: 
+```sh
+systemctl --user disable jprototerm
+ln -sf "$(dirname "$(readlink -f "$(command -v jprototerm)")")/../share/systemd/user/jprototerm.service" \
+  ~/.config/systemd/user/jprototerm.service
+systemctl --user enable --now jprototerm.service
+systemctl --user restart jprototerm.service
+```
+
+If the daemon can't reach your display (e.g. `systemctl --user status jprototerm` shows it
+failing to open a window), import the session variables once and restart it:
+
+```sh
+systemctl --user import-environment DISPLAY XAUTHORITY
+systemctl --user restart jprototerm.service
+```
+
+Closing a window (the WM close button, or the close-pane key on the last pane) tears that
+window down — its shell processes are signalled with the configured `close_signal` — without
+affecting other windows or the daemon. Stop the daemon (and all its windows) with
+`systemctl --user stop jprototerm.service`, or `pkill -f 'jprototerm --daemon'`.
+
 ## Config
 
 Configuration is read from:
@@ -98,6 +149,14 @@ enabled = true
 [scrollback]
 editor_command = "vi {file}"
 
+[worktree]
+relative_worktree_path = "./.worktrees"
+split_regex = ","
+# One of: "none", "cd", "create_panes", "create_panes_floating".
+post_create_action = "none"
+commands = []
+sync_panes = false
+
 [env.override]
 ZELLIJ_SESSION_NAME = ""
 
@@ -115,6 +174,10 @@ previous_tab = "ALT+SHIFT+H"
 next_tab = "ALT+SHIFT+L"
 open_font_selector = "ALT+T"
 open_scrollback = "ALT+S"
+create_worktree = "ALT+W"
+pane_sync_toggle = "ALT+Y"
+pane_sync_select = "SPACE"
+paste = "CTRL+SHIFT+V"
 ```
 
 ## Defaults
@@ -130,6 +193,18 @@ open_scrollback = "ALT+S"
 - `Alt+Shift+h` / `Alt+Shift+l`: previous / next tab
 - `Alt+t`: open the font selector
 - `Alt+s`: open the active pane scrollback in `$EDITOR`
+- `Alt+w`: edit one or more worktree names, split by `worktree.split_regex`, then run
+  `git worktree add <relative_worktree_path>/<name>` for each name from the previously focused
+  pane's working directory. `worktree.post_create_action` can then do nothing with `none`, `cd` the
+  previously active pane to the last created worktree, create one tiled pane per worktree with
+  `create_panes`, or create one floating pane per worktree with `create_panes_floating`.
+  `worktree.commands`, for example `["npm install", "git status"]`, can run commands in created
+  panes; commands are assigned in order and repeat when fewer commands than panes are created.
+  `worktree.sync_panes = true` syncs those created panes after the configured commands are sent.
+- `Alt+y`: enter pane-sync selection mode, commit the selection, or stop an active pane sync
+- `Space`: toggle the focused pane in the sync set while pane-sync selection mode is active
+- Once committed, input typed or pasted into any synced pane is mirrored to the other synced panes
+- `Ctrl+Shift+v`: paste
 - Font default: `JetBrainsMono Nerd Font`
 - Kitty graphics protocol parsing is enabled by default
 

config.example.toml

@@ -3,6 +3,9 @@ columns = 100
 rows = 30
 max_scrollback = 100000
 shell = "/bin/bash"
+# Signal sent to a pane's shell process when the pane is closed (e.g. ALT+X).
+# Use SIGKILL to force-kill instead of asking the shell to terminate.
+close_signal = "SIGTERM"
 font_family = "JetBrainsMono Nerd Font"
 font_size = 15
 
@@ -16,6 +19,14 @@ enabled = true
 [scrollback]
 editor_command = "vi {file}"
 
+[worktree]
+relative_worktree_path = "./.worktrees"
+split_regex = ","
+# One of: "none", "cd", "create_panes", "create_panes_floating".
+post_create_action = "none"
+commands = []
+sync_panes = false
+
 [env.override]
 ZELLIJ_SESSION_NAME = ""
 
@@ -25,9 +36,16 @@ 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"
+promote_floating = "ALT+P"
 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"
+create_worktree = "ALT+W"
+pane_sync_toggle = "ALT+Y"
+pane_sync_select = "SPACE"
 paste = "CTRL+SHIFT+V"

flake.nix

@@ -107,8 +107,35 @@
                 classpath="$classpath''${classpath:+:}$jar"
               done
 
+              # The CDS archive records launch-time module/classpath properties, including
+              # Nix store paths. Key it by this build's launch shape so stale archives from a
+              # previous package path cannot be reused, and pass the flags on java's command
+              # line so terminal child processes do not inherit them through JAVA_TOOL_OPTIONS.
+              cdsArchive="app-$(printf '%s\n' \
+                "${pkgs.jdk25}" \
+                "$out" \
+                "$classpath" \
+                "$out/share/jprototerm/javafx" \
+                "--enable-native-access=ALL-UNNAMED,javafx.graphics" \
+                "--add-modules=javafx.controls,javafx.fxml" \
+                "com.gregor.jprototerm.Main" \
+                | sha256sum | cut -c1-16).jsa"
+
+              # Prism frees GPU textures (and the X11 pixmaps behind them) only from phantom-ref
+              # Disposers that run during a GC. This daemon is one long-lived JVM whose ~140MB heap
+              # never nears the multi-GB default ceiling, so G1 almost never collects, the Disposers
+              # never run, and orphaned render resources (closed panes/windows, resized backbuffers)
+              # pile up until the X server's VRAM is exhausted and the whole session freezes. -Xmx
+              # makes output churn drive GC; G1PeriodicGCInterval runs a concurrent (low-pause) GC on
+              # an idle timer so an idle daemon still reclaims. The live heap is tiny, so GC is cheap.
               makeWrapper "${pkgs.jdk25}/bin/java" "$out/bin/jprototerm" \
+                --run 'if [ "$#" -eq 0 ]; then if [ -n "''${XDG_RUNTIME_DIR:-}" ]; then jprototermSock="$XDG_RUNTIME_DIR/jprototerm/daemon.sock"; else jprototermSock="/tmp/jprototerm-''${USER:-user}/daemon.sock"; fi; if [ -S "$jprototermSock" ] && printf "%s\n" "$(pwd)" | ${pkgs.socat}/bin/socat - UNIX-CONNECT:"$jprototermSock" >/dev/null 2>&1; then exit 0; fi; fi' \
                 --run 'export JPROTOTERM_HOST_LD_LIBRARY_PATH="''${LD_LIBRARY_PATH:-}"' \
+                --run 'cdsDir="''${XDG_CACHE_HOME:-$HOME/.cache}/jprototerm"; mkdir -p "$cdsDir"' \
+                --add-flags "-XX:+AutoCreateSharedArchive" \
+                --add-flags "-XX:SharedArchiveFile=\$cdsDir/$cdsArchive" \
+                --add-flags "-Xmx512m" \
+                --add-flags "-XX:G1PeriodicGCInterval=5000" \
                 --add-flags "--enable-native-access=ALL-UNNAMED,javafx.graphics" \
                 --add-flags "--module-path $out/share/jprototerm/javafx" \
                 --add-flags "--add-modules javafx.controls,javafx.fxml" \
@@ -119,6 +146,25 @@
                 --set JLIBGHOSTTY_LIBRARY "${ghosttyVt}/lib/libghostty-vt.so" \
                 --set GDK_BACKEND x11
 
+              # Optional background daemon: one JVM hosts every window, so client launches skip
+              # cold JVM/JavaFX/GL startup. A *user* service tied to graphical-session.target (X11
+              # needs a display, which only exists after login). Enable instructions are in README.
+              mkdir -p "$out/share/systemd/user"
+              cat > "$out/share/systemd/user/jprototerm.service" <<EOF
+              [Unit]
+              Description=jprototerm terminal daemon
+              PartOf=graphical-session.target
+              After=graphical-session.target
+
+              [Service]
+              Type=simple
+              ExecStart=$out/bin/jprototerm --daemon
+              Restart=on-failure
+
+              [Install]
+              WantedBy=graphical-session.target
+              EOF
+
               runHook postInstall
             '';
           });

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

@@ -29,6 +29,12 @@ public record AppConfig(
         double windowHeight,
         boolean kittyGraphics,
         String scrollbackEditorCommand,
+        String worktreeRelativePath,
+        String worktreeSplitRegex,
+        String worktreePostCreateAction,
+        List<String> worktreeCommands,
+        boolean worktreeSyncPanes,
+        String closeSignal,
         Map<String, String> envOverride,
         Map<String, KeyBinding> keybindings
 ) {
@@ -47,6 +53,9 @@ public record AppConfig(
             "next_tab",
             "open_font_selector",
             "open_scrollback",
+            "create_worktree",
+            "pane_sync_toggle",
+            "pane_sync_select",
             "paste"
     );
 
@@ -54,7 +63,7 @@ public record AppConfig(
         AppConfig defaults = defaults();
         Path path = configPath();
         if (!Files.isRegularFile(path)) {
-            writeDefaultConfig(path, defaults);
+            save(path, defaults);
             return defaults;
         }
 
@@ -71,6 +80,12 @@ public record AppConfig(
                     doubleValue(document, "window.height", defaults.windowHeight),
                     booleanValue(document, "kitty_graphics.enabled", defaults.kittyGraphics),
                     stringValue(document, "scrollback.editor_command", defaults.scrollbackEditorCommand),
+                    stringValue(document, "worktree.relative_worktree_path", defaults.worktreeRelativePath),
+                    stringValue(document, "worktree.split_regex", defaults.worktreeSplitRegex),
+                    stringValue(document, "worktree.post_create_action", defaults.worktreePostCreateAction),
+                    stringListValue(document, "worktree.commands", defaults.worktreeCommands),
+                    booleanValue(document, "worktree.sync_panes", defaults.worktreeSyncPanes),
+                    closeSignalValue(document, defaults.closeSignal),
                     envOverride(document, defaults.envOverride),
                     keybindings(document, defaults)
             );
@@ -92,6 +107,12 @@ public record AppConfig(
                 760.0,
                 true,
                 defaultScrollbackEditorCommand(),
+                "./.worktrees",
+                ",",
+                "none",
+                List.of(),
+                false,
+                "SIGTERM",
                 Map.of(),
                 Map.ofEntries(
                         Map.entry("navigate_left", KeyBinding.parse("ALT+H")),
@@ -108,6 +129,9 @@ public record AppConfig(
                         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")),
+                        Map.entry("create_worktree", KeyBinding.parse("ALT+W")),
+                        Map.entry("pane_sync_toggle", KeyBinding.parse("ALT+Y")),
+                        Map.entry("pane_sync_select", KeyBinding.parse("SPACE")),
                         Map.entry("paste", KeyBinding.parse("CTRL+SHIFT+V"))
                 )
         );
@@ -125,11 +149,27 @@ public record AppConfig(
                 windowHeight,
                 kittyGraphics,
                 scrollbackEditorCommand,
+                worktreeRelativePath,
+                worktreeSplitRegex,
+                worktreePostCreateAction,
+                worktreeCommands,
+                worktreeSyncPanes,
+                closeSignal,
                 envOverride,
                 keybindings
         );
     }
 
+    /**
+     * The {@link #closeSignal} as a Linux signal number, sent to a pane's shell process when the
+     * pane is closed (e.g. via the close-pane key). Falls back to SIGTERM (15) if the configured
+     * name is somehow unresolvable.
+     */
+    public int closeSignalNumber() {
+        int number = LinuxPty.signalNumber(closeSignal);
+        return number < 0 ? 15 : number;
+    }
+
     public void save() {
         save(configPath(), this);
     }
@@ -156,6 +196,23 @@ public record AppConfig(
         return editor.trim() + " {file}";
     }
 
+    /**
+     * Reads {@code terminal.close_signal}, normalising it to a canonical {@code SIG*} name. An
+     * unknown or unset value keeps {@code fallback} so a typo can't leave a pane unkillable.
+     */
+    private static String closeSignalValue(TomlTable table, String fallback) {
+        String value = stringValue(table, "terminal.close_signal", null);
+        if (value == null) {
+            return fallback;
+        }
+        if (LinuxPty.signalNumber(value) < 0) {
+            System.err.println("Unknown terminal.close_signal '" + value + "', using " + fallback);
+            return fallback;
+        }
+        String normalized = value.trim().toUpperCase(java.util.Locale.ROOT);
+        return normalized.startsWith("SIG") ? normalized : "SIG" + normalized;
+    }
+
     private static Map<String, KeyBinding> keybindings(TomlTable table, AppConfig defaults) {
         Map<String, KeyBinding> parsed = new LinkedHashMap<>();
         for (String key : KEYBINDING_KEYS) {
@@ -164,10 +221,6 @@ public record AppConfig(
         return Map.copyOf(parsed);
     }
 
-    private static void writeDefaultConfig(Path path, AppConfig defaults) {
-        save(path, defaults);
-    }
-
     private static void save(Path path, AppConfig config) {
         try {
             Path parent = path.getParent();
@@ -193,6 +246,7 @@ public record AppConfig(
         builder.append("rows = ").append(rows).append('\n');
         builder.append("max_scrollback = ").append(maxScrollback).append('\n');
         builder.append("shell = ").append(quotedList(shell)).append('\n');
+        builder.append("close_signal = ").append(quoted(closeSignal)).append('\n');
         builder.append("font_family = ").append(quoted(fontFamily)).append('\n');
         builder.append("font_size = ").append(trimDouble(fontSize)).append("\n\n");
         builder.append("[window]\n");
@@ -202,6 +256,12 @@ public record AppConfig(
         builder.append("enabled = ").append(kittyGraphics).append("\n\n");
         builder.append("[scrollback]\n");
         builder.append("editor_command = ").append(quoted(scrollbackEditorCommand)).append("\n\n");
+        builder.append("[worktree]\n");
+        builder.append("relative_worktree_path = ").append(quoted(worktreeRelativePath)).append('\n');
+        builder.append("split_regex = ").append(quoted(worktreeSplitRegex)).append('\n');
+        builder.append("post_create_action = ").append(quoted(worktreePostCreateAction)).append('\n');
+        builder.append("commands = ").append(quotedList(worktreeCommands)).append('\n');
+        builder.append("sync_panes = ").append(worktreeSyncPanes).append("\n\n");
         builder.append("[env.override]\n");
         for (Map.Entry<String, String> entry : envOverride.entrySet()) {
             builder.append(entry.getKey()).append(" = ").append(quoted(entry.getValue())).append('\n');
@@ -308,15 +368,7 @@ public record AppConfig(
     }
 
     private static int intValue(TomlTable table, String key, int fallback) {
-        TomlPrimitive primitive = primitive(table, key);
-        if (primitive == null) {
-            return fallback;
-        }
-        try {
-            return primitive.asInteger();
-        } catch (RuntimeException ex) {
-            return fallback;
-        }
+        return (int) longValue(table, key, fallback);
     }
 
     private static long longValue(TomlTable table, String key, long fallback) {

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

@@ -19,9 +19,12 @@ import javafx.scene.text.TextAlignment;
 
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
 
 /**
  * Owns the window's tabs and drives rendering and input. It composites only the current tab:
@@ -35,6 +38,8 @@ public final class Compositor {
     // Canvas background shown wherever no pane covers (gaps). Painted on a full recomposite.
     private static final Color GAP_BACKGROUND = Color.rgb(16, 16, 18);
     private static final Color TAB_TEXT = Color.rgb(225, 229, 235);
+    private static final Color PANE_SYNC_SELECT_BORDER = Color.rgb(255, 183, 77);
+    private static final Color PANE_SYNC_COMMITTED_BORDER = Color.rgb(105, 214, 128);
     // Thin tab strip shown at the top when more than one tab is open.
     private static final double TAB_BAR_HEIGHT = 22.0;
 
@@ -52,6 +57,19 @@ public final class Compositor {
     // 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<>();
+    // Off-screen panes (background tabs, hidden floating groups) keep their full-resolution pixel
+    // backbuffer + GPU image until released. We free them after a short grace period rather than the
+    // instant they're hidden, so rapidly flipping through tabs never thrashes the realloc/upload.
+    private static final long RELEASE_DELAY_NANOS = 750_000_000L;
+    // Hidden pane -> nanoTime it became hidden (the release timer); removed once released or shown.
+    private final Map<TerminalPane, Long> hiddenSince = new HashMap<>();
+    // Panes whose backbuffer is currently released, so we don't release again every frame.
+    private final Set<TerminalPane> released = new HashSet<>();
+    private final Set<TerminalPane> paneSyncSelection = new LinkedHashSet<>();
+    private final Set<TerminalPane> paneSyncPanes = new LinkedHashSet<>();
+    private boolean paneSyncSelectMode;
+    // layoutVersion at the last sweep: lets an idle, all-released steady state skip the scan.
+    private long lastSweepLayoutVersion = Long.MIN_VALUE;
     // Cheap per-frame dirty signal: skip the whole render when none of these changed.
     private double lastWidth = -1.0;
     private double lastHeight = -1.0;
@@ -65,9 +83,18 @@ public final class Compositor {
     private Runnable onEmpty = () -> {};
 
     public Compositor(AppConfig config, TerminalMetrics metrics) {
+        this(config, metrics, null);
+    }
+
+    /**
+     * Creates a compositor whose first tab's first pane starts in {@code workingDirectory} (e.g. the
+     * cwd a client passed when asking the daemon to open this window), or the user's home when
+     * {@code null}.
+     */
+    public Compositor(AppConfig config, TerminalMetrics metrics, String workingDirectory) {
         this.config = config;
         this.metrics = metrics;
-        tabs.add(new Tab(config, metrics, this::closePane));
+        tabs.add(new Tab(config, metrics, workingDirectory, this::closePane));
         canvas.setFocusTraversable(true);
         canvas.setOnMousePressed(this::handleMousePressed);
         canvas.setOnMouseReleased(this::handleMouseReleased);
@@ -93,7 +120,7 @@ public final class Compositor {
     public void setFont(String family, double size) {
         metrics.setFont(family, size);
         paneContentVersion.clear();
-        lastWidth = -1.0; // force a redraw on the next frame
+        layoutVersion++; // recomposite with the new metrics on the next frame
     }
 
     // ---- Tabs and panes -------------------------------------------------------------
@@ -102,8 +129,9 @@ public final class Compositor {
         return tabs.isEmpty();
     }
 
+    /** The active pane of the current tab, or {@code null} when no tab is left. */
     public TerminalPane activePane() {
-        return currentTab().activePane();
+        return isEmpty() ? null : currentTab().activePane();
     }
 
     public void navigate(Direction direction) {
@@ -112,28 +140,89 @@ public final class Compositor {
         }
     }
 
-    public void toggleFloating() {
-        if (isEmpty()) {
+    public boolean isPaneSyncSelecting() {
+        return paneSyncSelectMode;
+    }
+
+    public void togglePaneSync() {
+        if (paneSyncSelectMode) {
+            paneSyncPanes.clear();
+            paneSyncPanes.addAll(paneSyncSelection);
+            paneSyncSelectMode = false;
+            paneSyncSelection.clear();
+            prunePaneSyncState();
+            layoutVersion++;
             return;
         }
-        currentTab().toggleFloating();
+        if (!paneSyncPanes.isEmpty()) {
+            paneSyncPanes.clear();
+            layoutVersion++;
+            return;
+        }
+        if (activePane() == null) {
+            return;
+        }
+        paneSyncSelectMode = true;
+        paneSyncSelection.clear();
         layoutVersion++;
     }
 
+    public void togglePaneSyncSelection() {
+        TerminalPane active = activePane();
+        if (active == null || !paneSyncSelectMode) {
+            return;
+        }
+        if (!paneSyncSelection.add(active)) {
+            paneSyncSelection.remove(active);
+        }
+        layoutVersion++;
+    }
+
+    public List<TerminalPane> paneSyncPeers(TerminalPane source) {
+        prunePaneSyncState();
+        if (source == null || !paneSyncPanes.contains(source)) {
+            return List.of();
+        }
+        return paneSyncPanes.stream()
+                .filter(pane -> pane != source)
+                .toList();
+    }
+
+    public void syncPanes(List<TerminalPane> panes) {
+        paneSyncSelectMode = false;
+        paneSyncSelection.clear();
+        paneSyncPanes.clear();
+        for (TerminalPane pane : panes) {
+            if (pane != null) {
+                paneSyncPanes.add(pane);
+            }
+        }
+        prunePaneSyncState();
+        layoutVersion++;
+    }
+
+    public void toggleFloating() {
+        mutateCurrentTab(() -> currentTab().toggleFloating());
+    }
+
     public void createPane() {
-        if (isEmpty()) {
-            return;
-        }
-        currentTab().createPane();
-        layoutVersion++;
+        mutateCurrentTab(() -> currentTab().createPane());
     }
 
-    /** Opens a new floating pane, makes it active, and returns it (null when no tab exists). */
-    public TerminalPane openFloatingPane() {
+    public TerminalPane createTiledPane(String workingDirectory) {
         if (isEmpty()) {
             return null;
         }
-        TerminalPane pane = currentTab().createFloatingPane();
+        TerminalPane pane = currentTab().createTiledPane(workingDirectory);
+        layoutVersion++;
+        return pane;
+    }
+
+    public TerminalPane createFloatingPaneInDirectory(String workingDirectory) {
+        if (isEmpty()) {
+            return null;
+        }
+        TerminalPane pane = currentTab().createFloatingPaneInDirectory(workingDirectory);
         layoutVersion++;
         return pane;
     }
@@ -152,26 +241,25 @@ public final class Compositor {
     }
 
     public void nextFloatingPane() {
-        if (isEmpty()) {
-            return;
-        }
-        currentTab().nextFloatingPane();
-        layoutVersion++;
+        mutateCurrentTab(() -> currentTab().nextFloatingPane());
     }
 
-    public void promoteActiveFloating() {
+    public void toggleActiveFloating() {
+        mutateCurrentTab(() -> currentTab().toggleActiveFloating());
+    }
+
+    // Run a structural change on the current tab and bump the layout version so the next frame
+    // recomposites. No-op when no tab is left.
+    private void mutateCurrentTab(Runnable change) {
         if (isEmpty()) {
             return;
         }
-        currentTab().promoteActiveFloating();
+        change.run();
         layoutVersion++;
     }
 
     public void closeActivePane() {
-        if (isEmpty()) {
-            return;
-        }
-        TerminalPane active = currentTab().activePane();
+        TerminalPane active = activePane();
         if (active != null) {
             closePane(active);
         }
@@ -187,6 +275,7 @@ public final class Compositor {
         for (int i = 0; i < tabs.size(); i++) {
             Tab tab = tabs.get(i);
             if (tab.closePane(pane)) {
+                removePaneFromSyncState(pane);
                 if (tab.isEmpty()) {
                     // Closing a tab's last pane closes the tab. Keep currentTabIndex pointing at the
                     // same tab (or clamp it when the current/last tab went away).
@@ -209,7 +298,8 @@ public final class Compositor {
     public void newTab() {
         // Open the new tab in the currently active pane's working directory, so it lands where the
         // user currently is rather than always in home.
-        String workingDirectory = isEmpty() ? null : currentTab().activePane().currentWorkingDirectory();
+        TerminalPane active = activePane();
+        String workingDirectory = active != null ? active.currentWorkingDirectory() : null;
         tabs.add(new Tab(config, metrics, workingDirectory, this::closePane));
         currentTabIndex = tabs.size() - 1;
         layoutVersion++;
@@ -234,6 +324,21 @@ public final class Compositor {
             tab.close();
         }
         tabs.clear();
+        paneSyncSelectMode = false;
+        paneSyncSelection.clear();
+        paneSyncPanes.clear();
+    }
+
+    /**
+     * Signals and reaps every pane's shell process across all tabs, without tearing down render
+     * state. Intended for a JVM shutdown hook (SIGTERM/SIGINT/SIGHUP), so child shells get the
+     * configured close signal instead of being orphaned when jprototerm itself is killed. Safe to
+     * call off the FX thread and idempotent; see {@link TerminalPane#terminateSession()}.
+     */
+    public void terminateSessions() {
+        for (Tab tab : List.copyOf(tabs)) {
+            tab.terminateSessions();
+        }
     }
 
     private Tab currentTab() {
@@ -257,6 +362,7 @@ public final class Compositor {
     // ---- Rendering ------------------------------------------------------------------
 
     public void render() {
+        sweepHiddenPanes();
         switch (nextFrameType()) {
             case IDLE -> { }
             case LAYOUT -> renderLayoutFrame();
@@ -264,6 +370,48 @@ public final class Compositor {
         }
     }
 
+    // Free the backbuffer of any pane that has been off-screen past the grace period, and re-arm the
+    // timer for newly hidden panes. The next layout frame rebuilds a released pane (paintFull goes
+    // through ensure()), so showing a tab again is the only cost. Skips entirely once everything that
+    // can be hidden is already released and the layout hasn't changed, so an idle multi-tab window
+    // does no per-frame work here.
+    private void sweepHiddenPanes() {
+        if (layoutVersion == lastSweepLayoutVersion && hiddenSince.isEmpty()) {
+            return;
+        }
+        lastSweepLayoutVersion = layoutVersion;
+
+        // Fast path: a single tab compositing all of its panes has nothing off-screen.
+        if (tabs.size() <= 1 && (tabs.isEmpty() || !currentTab().hasHiddenPanes())) {
+            hiddenSince.clear();
+            released.clear();
+            return;
+        }
+
+        Set<TerminalPane> visible = new HashSet<>(currentPanes());
+        Set<TerminalPane> live = new HashSet<>();
+        long now = System.nanoTime();
+        for (Tab tab : tabs) {
+            for (TerminalPane pane : tab.allPanes()) {
+                live.add(pane);
+                if (visible.contains(pane)) {
+                    hiddenSince.remove(pane);
+                    released.remove(pane);
+                } else if (!released.contains(pane)) {
+                    Long since = hiddenSince.putIfAbsent(pane, now);
+                    if (since != null && now - since >= RELEASE_DELAY_NANOS) {
+                        pane.releaseRenderResources();
+                        released.add(pane);
+                        hiddenSince.remove(pane);
+                    }
+                }
+            }
+        }
+        // Forget panes that have since closed.
+        hiddenSince.keySet().retainAll(live);
+        released.retainAll(live);
+    }
+
     // Classify this frame and commit the change trackers. A layout change (size, font,
     // tab/pane set, z-order, active pane) needs a full recomposite; otherwise a change to the
     // current tab's content version repaints only the panes that changed; otherwise nothing
@@ -318,6 +466,7 @@ public final class Compositor {
         for (TerminalPane pane : panes) {
             paneContentVersion.put(pane, pane.paintFull(gc, isActive(pane)));
         }
+        drawPaneSyncOverlay(gc, panes);
         imageOverlay.sync(panes);
     }
 
@@ -337,6 +486,7 @@ public final class Compositor {
             paneContentVersion.put(pane, pane.paintIncremental(gc, isActive(pane)));
             imageOverlay.updatePane(pane);
         }
+        drawPaneSyncOverlay(gc, panes);
     }
 
     private GraphicsContext beginFrame() {
@@ -372,6 +522,68 @@ public final class Compositor {
         gc.setFontSmoothingType(FontSmoothingType.LCD);
     }
 
+    private void drawPaneSyncOverlay(GraphicsContext gc, List<TerminalPane> panes) {
+        Set<TerminalPane> highlighted = paneSyncSelectMode ? paneSyncSelection : paneSyncPanes;
+        if (highlighted.isEmpty()) {
+            return;
+        }
+
+        gc.save();
+        try {
+            // Draw a thin sync border inset just inside the pane's own edge border, so the
+            // renderer's active (blue) / inactive border stays visible and you can still tell
+            // which synced pane is focused.
+            double lineWidth = 2.0;
+            double inset = 2.0 + lineWidth / 2.0; // clear the renderer's 2px active border
+            gc.setLineWidth(lineWidth);
+            gc.setStroke(paneSyncSelectMode ? PANE_SYNC_SELECT_BORDER : PANE_SYNC_COMMITTED_BORDER);
+            for (TerminalPane pane : panes) {
+                if (!highlighted.contains(pane)) {
+                    continue;
+                }
+                gc.save();
+                double x = Math.round(pane.x()) + inset;
+                double y = Math.round(pane.y()) + inset;
+                double width = Math.max(0.0, pane.width() - 2.0 * inset);
+                double height = Math.max(0.0, pane.height() - 2.0 * inset);
+                TerminalRenderer.clip(gc, Math.round(pane.x()), Math.round(pane.y()), pane.width(), pane.height(), pane.clip());
+                gc.strokeRect(x, y, width, height);
+                gc.restore();
+            }
+        } finally {
+            gc.restore();
+        }
+    }
+
+    private void removePaneFromSyncState(TerminalPane pane) {
+        boolean changed = paneSyncSelection.remove(pane);
+        changed |= paneSyncPanes.remove(pane);
+        if (paneSyncPanes.size() < 2) {
+            changed |= !paneSyncPanes.isEmpty();
+            paneSyncPanes.clear();
+        }
+        if (changed) {
+            layoutVersion++;
+        }
+    }
+
+    private void prunePaneSyncState() {
+        Set<TerminalPane> live = livePanes();
+        paneSyncSelection.retainAll(live);
+        paneSyncPanes.retainAll(live);
+        if (paneSyncPanes.size() < 2) {
+            paneSyncPanes.clear();
+        }
+    }
+
+    private Set<TerminalPane> livePanes() {
+        Set<TerminalPane> live = new HashSet<>();
+        for (Tab tab : tabs) {
+            live.addAll(tab.allPanes());
+        }
+        return live;
+    }
+
     // ---- Input ----------------------------------------------------------------------
 
     private void handleMousePressed(MouseEvent event) {
@@ -394,11 +606,11 @@ public final class Compositor {
     private void handleMouseReleased(MouseEvent event) {
         TerminalPane pane = paneAt(event.getX(), event.getY());
         if (pane == null) {
-            pane = activePane();
+            pane = activePane(); // released outside every pane (e.g. mid-drag): route to the active one
         }
 
         MouseButton button = pressedButton == MouseButton.UNKNOWN ? mouseButton(event) : pressedButton;
-        MouseTarget target = mouseTarget(pane);
+        MouseTarget target = pane == null ? null : mouseTarget(pane);
         if (target != null) {
             send(pane, target, MouseInput.release(button, localX(event.getX(), pane, target), localY(event.getY(), pane, target), modifiers(event)), false, event);
         }
@@ -409,7 +621,10 @@ public final class Compositor {
     private void handleMouseDragged(MouseEvent event) {
         TerminalPane pane = paneAt(event.getX(), event.getY());
         if (pane == null) {
-            pane = activePane();
+            pane = activePane(); // dragged outside every pane: route to the active one
+        }
+        if (pane == null) {
+            return;
         }
 
         MouseButton button = pressedButton == MouseButton.UNKNOWN ? mouseButton(event) : pressedButton;

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

@@ -0,0 +1,183 @@
+package com.gregor.jprototerm;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.net.StandardProtocolFamily;
+import java.net.UnixDomainSocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.ServerSocketChannel;
+import java.nio.channels.SocketChannel;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.attribute.PosixFilePermissions;
+
+/**
+ * Single-instance server and its thin client, over a per-user Unix domain socket. The server hosts
+ * every window in one JVM (see {@link WindowManager}); a client invocation just asks it to open a
+ * window in the client's working directory and exits, so the window appears without paying cold
+ * JVM/JavaFX/GL startup.
+ *
+ * <p>Protocol is deliberately trivial: the client writes one UTF-8 line — the absolute working
+ * directory — and the server replies {@code OK\n}. The socket lives under {@code XDG_RUNTIME_DIR}
+ * (mode 0700), so only the owning user can connect.
+ */
+public final class Daemon {
+    // One request is a single line holding a filesystem path; anything bigger is bogus.
+    private static final int MAX_REQUEST_BYTES = 4096;
+    // The accept loop is single-threaded, so a client that stalls must not wedge the daemon.
+    private static final long READ_TIMEOUT_NANOS = 5_000_000_000L;
+
+    private Daemon() {
+    }
+
+    /** Runs the server: brings up the toolkit, binds the socket, and serves window-open requests. */
+    public static void run() {
+        Path socket = socketPath();
+        try {
+            Files.createDirectories(socket.getParent());
+            secureDir(socket.getParent());
+        } catch (IOException ex) {
+            System.err.println("jprototerm: cannot secure socket dir " + socket.getParent() + ": " + ex.getMessage());
+            return;
+        }
+
+        WindowManager manager = WindowManager.start(WindowManager.Mode.DAEMON);
+
+        try (ServerSocketChannel server = bind(socket)) {
+            while (true) {
+                try {
+                    handle(server.accept(), manager);
+                } catch (IOException ex) {
+                    System.err.println("jprototerm: connection error: " + ex.getMessage());
+                }
+            }
+        } catch (IOException ex) {
+            System.err.println("jprototerm: daemon socket error: " + ex.getMessage());
+        }
+    }
+
+    /**
+     * Client side: connect to a running daemon and ask it to open a window in {@code workingDirectory}.
+     * Returns {@code true} if the daemon handled it, {@code false} if none is reachable (the caller
+     * then falls back to a standalone in-process window).
+     */
+    public static boolean tryClient(String workingDirectory) {
+        Path socket = socketPath();
+        if (!Files.exists(socket)) {
+            return false;
+        }
+        try (SocketChannel channel = SocketChannel.open(UnixDomainSocketAddress.of(socket))) {
+            channel.write(ByteBuffer.wrap((workingDirectory + "\n").getBytes(StandardCharsets.UTF_8)));
+            // Best-effort wait for the ack so we don't race ahead of the window opening.
+            channel.read(ByteBuffer.allocate(16));
+            return true;
+        } catch (IOException ex) {
+            return false; // no daemon, or a stale socket file — fall back to standalone
+        }
+    }
+
+    private static ServerSocketChannel bind(Path socket) throws IOException {
+        UnixDomainSocketAddress address = UnixDomainSocketAddress.of(socket);
+        ServerSocketChannel channel = ServerSocketChannel.open(StandardProtocolFamily.UNIX);
+        try {
+            channel.bind(address);
+            return channel;
+        } catch (IOException firstTry) {
+            // The path is taken. If a live daemon answers, this invocation lost the race; otherwise
+            // it's a stale socket from a crashed daemon, so remove it and rebind.
+            if (tryClient0(socket)) {
+                channel.close();
+                System.err.println("jprototerm: a daemon is already running");
+                System.exit(0);
+            }
+            Files.deleteIfExists(socket);
+            channel.bind(address);
+            return channel;
+        }
+    }
+
+    /** A bare connect probe used by {@link #bind} to tell a live daemon from a stale socket file. */
+    private static boolean tryClient0(Path socket) {
+        try (SocketChannel channel = SocketChannel.open(UnixDomainSocketAddress.of(socket))) {
+            return true;
+        } catch (IOException ex) {
+            return false;
+        }
+    }
+
+    private static void handle(SocketChannel connection, WindowManager manager) throws IOException {
+        try (connection) {
+            String workingDirectory = readLine(connection);
+            manager.openWindow(workingDirectory == null || workingDirectory.isBlank()
+                    ? null
+                    : workingDirectory.trim());
+            connection.configureBlocking(true);
+            connection.write(ByteBuffer.wrap("OK\n".getBytes(StandardCharsets.UTF_8)));
+        }
+    }
+
+    // Reads the request line non-blocking with a deadline and a size cap: the accept loop is
+    // single-threaded, so a client that stalls or never sends a newline must fail the connection
+    // (an IOException logged by run()) rather than wedge the daemon or grow the buffer unbounded.
+    private static String readLine(SocketChannel channel) throws IOException {
+        channel.configureBlocking(false);
+        long deadline = System.nanoTime() + READ_TIMEOUT_NANOS;
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        ByteBuffer buffer = ByteBuffer.allocate(4096);
+        while (true) {
+            int n = channel.read(buffer);
+            if (n > 0) {
+                buffer.flip();
+                while (buffer.hasRemaining()) {
+                    byte b = buffer.get();
+                    if (b == '\n') {
+                        return out.toString(StandardCharsets.UTF_8);
+                    }
+                    out.write(b);
+                    if (out.size() > MAX_REQUEST_BYTES) {
+                        throw new IOException("request line too long");
+                    }
+                }
+                buffer.clear();
+            } else if (n == -1) {
+                return out.size() == 0 ? null : out.toString(StandardCharsets.UTF_8);
+            } else {
+                if (System.nanoTime() >= deadline) {
+                    throw new IOException("request timed out");
+                }
+                try {
+                    Thread.sleep(5);
+                } catch (InterruptedException ex) {
+                    Thread.currentThread().interrupt();
+                    throw new IOException("interrupted while reading request");
+                }
+            }
+        }
+    }
+
+    private static Path socketPath() {
+        String runtimeDir = System.getenv("XDG_RUNTIME_DIR");
+        Path dir = runtimeDir != null && !runtimeDir.isBlank()
+                ? Path.of(runtimeDir, "jprototerm")
+                : Path.of("/tmp", "jprototerm-" + System.getProperty("user.name", "user"));
+        return dir.resolve("daemon.sock");
+    }
+
+    // Make the socket dir private, and refuse to use it if it is not ours. The /tmp fallback
+    // path is predictable, so another user could have pre-created it (the classic /tmp race);
+    // binding a socket inside a directory someone else owns would hand them control of it.
+    private static void secureDir(Path dir) throws IOException {
+        try {
+            Files.setPosixFilePermissions(dir, PosixFilePermissions.fromString("rwx------"));
+        } catch (UnsupportedOperationException ignored) {
+            return; // not a POSIX filesystem: nothing more we can check
+        }
+        String owner = Files.getOwner(dir, LinkOption.NOFOLLOW_LINKS).getName();
+        String user = System.getProperty("user.name");
+        if (!owner.equals(user)) {
+            throw new IOException(dir + " is owned by '" + owner + "', not '" + user + "'");
+        }
+    }
+}

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

@@ -13,17 +13,11 @@ import dev.jlibghostty.RenderCursorStyle;
 import dev.jlibghostty.RenderRow;
 import dev.jlibghostty.RenderStateSnapshot;
 import javafx.geometry.Rectangle2D;
-import javafx.scene.SnapshotParameters;
-import javafx.scene.canvas.Canvas;
 import javafx.scene.canvas.GraphicsContext;
 import javafx.scene.image.Image;
 import javafx.scene.image.PixelFormat;
 import javafx.scene.image.PixelBuffer;
-import javafx.scene.image.PixelReader;
 import javafx.scene.image.WritableImage;
-import javafx.scene.paint.Color;
-import javafx.scene.text.FontSmoothingType;
-import javafx.scene.text.Text;
 
 import java.io.ByteArrayInputStream;
 import java.nio.IntBuffer;
@@ -45,19 +39,17 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
     private static final int DIRTY_PARTIAL = 1;
     private static final int DIRTY_FULL = 2;
 
-    private static final Color DEFAULT_FOREGROUND = Color.rgb(225, 229, 235);
-    private static final Color SELECTED_BACKGROUND = Color.rgb(52, 92, 140);
+    // All colors are packed ARGB ints (alpha always 0xff): the software backbuffer never needs
+    // a javafx Color, so cells go straight from RenderColor to the pixel format.
+    private static final int DEFAULT_FOREGROUND = 0xffe1e5eb; // rgb(225, 229, 235)
+    private static final int SELECTED_BACKGROUND = 0xff345c8c; // 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);
-    private static final Color ACTIVE_BORDER = Color.rgb(87, 166, 255);
-    private static final Color INACTIVE_BORDER = Color.rgb(52, 57, 65);
-    private static final Color CURSOR_FILL = Color.rgb(225, 229, 235, 0.28);
-
-    // 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 final int PANE_BACKGROUND = 0xff090a0c; // rgb(9, 10, 12)
+    private static final int ACTIVE_BORDER = 0xff57a6ff; // rgb(87, 166, 255)
+    private static final int INACTIVE_BORDER = 0xff343941; // rgb(52, 57, 65)
+    // Block cursor: DEFAULT_FOREGROUND blended at 28% alpha by fillRectAlpha.
+    private static final int CURSOR_FILL_ALPHA = 71;
 
     private final TerminalMetrics metrics;
     // Decoded kitty images for this renderer's pane (kitty graphics state is per-terminal).
@@ -109,8 +101,16 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             software.paintFullOrShifted(gc, target.snapshotFull(), px, py, width, height, active);
         } else if (dirty == DIRTY_PARTIAL) {
             software.paintDirty(gc, target, snapshot, px, py, width, height, active);
+        } else if (software.cursorChanged(snapshot)) {
+            // dirty == FALSE means no cell content changed, but the cursor can still have moved,
+            // changed style, or toggled visibility on its own (e.g. plain cursor-left/right, or the
+            // hide/redraw/show dance fish does around a line edit). No row was marshalled, and we
+            // must not force a full snapshot here — that would re-marshal every cell on every
+            // cursor move. Instead restore the pixels saved beneath the old cursor (erasing it)
+            // and redraw the cursor at its new spot, touching only those two cell rects.
+            software.paintCursorOnly(gc, snapshot, px, py, width, height);
         }
-        // dirty == FALSE: nothing visible changed.
+        // dirty == FALSE with an unchanged cursor: nothing visible changed.
         gc.restore();
         kittyImageNodes = List.of();
     }
@@ -120,18 +120,20 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         return kittyImageNodes;
     }
 
-    // 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;
+    @Override
+    void release() {
+        software.release();
+        kittyImageNodes = List.of();
     }
 
-    private static Color rowEdgeBackground(RenderRow row, boolean firstCell) {
+    // 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 int cellBackgroundColor(RenderCell cell) {
+        int override = cellBackgroundOverride(cell);
+        return override != 0 ? override : PANE_BACKGROUND;
+    }
+
+    private static int rowEdgeBackground(RenderRow row, boolean firstCell) {
         List<RenderCell> cells = row.cells();
         if (cells.isEmpty()) {
             return PANE_BACKGROUND;
@@ -139,41 +141,28 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         return cellBackgroundColor(firstCell ? cells.get(0) : cells.get(cells.size() - 1));
     }
 
-    // Background override for a cell: null means the pane default background already covers it.
-    private static Color cellBackgroundOverride(RenderCell cell) {
+    // Background override for a cell: 0 means the pane default background already covers it
+    // (real colors always carry 0xff alpha, so 0 is never a valid color).
+    private static int cellBackgroundOverride(RenderCell cell) {
         if (cell.inverse()) {
             var fg = cell.foreground();
-            return fg.isPresent() ? toFxColor(fg.get()) : DEFAULT_FOREGROUND;
+            return fg.isPresent() ? packArgb(fg.get()) : DEFAULT_FOREGROUND;
         }
-        var bgOpt = cell.background();
-        Color bg = bgOpt.isPresent() ? toFxColor(bgOpt.get()) : null;
-        return bg;
+        var bg = cell.background();
+        return bg.isPresent() ? packArgb(bg.get()) : 0;
     }
 
-    private static Color cellForegroundColor(RenderCell cell) {
-        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;
-
+    private static int cellForegroundColor(RenderCell cell) {
         if (cell.inverse()) {
-            return (bg != null) ? bg : PANE_BACKGROUND;
+            var bg = cell.background();
+            return bg.isPresent() ? packArgb(bg.get()) : PANE_BACKGROUND;
         }
-        return fg;
+        var fg = cell.foreground();
+        return fg.isPresent() ? packArgb(fg.get()) : DEFAULT_FOREGROUND;
     }
 
-    private static Color toFxColor(RenderColor color) {
-        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 int packArgb(RenderColor color) {
+        return 0xff000000 | (color.red() << 16) | (color.green() << 8) | color.blue();
     }
 
     // ---- Kitty graphics --------------------------------------------------------------
@@ -416,7 +405,15 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         private WritableImage image;
         private long[] rowHashes = new long[0];
         private CursorState lastCursor = CursorState.none();
-        private GlyphCache glyphs;
+        // Pixels captured from beneath the cursor just before it was drawn, plus the clamped rect
+        // they came from. A cursor-only frame restores these to erase the old cursor without
+        // repainting the row's cells (which would need a full, freshly-marshalled snapshot).
+        private int[] cursorUnder = new int[0];
+        private int cursorUnderX;
+        private int cursorUnderY;
+        private int cursorUnderW;
+        private int cursorUnderH;
+        private boolean cursorSaved;
         // Half-open [min, max) vertical span of buffer rows written since the last present, so
         // present() can upload only that band to the GPU instead of the whole pane texture.
         private int dirtyMinY = Integer.MAX_VALUE;
@@ -425,6 +422,7 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         private void invalidate() {
             rowHashes = new long[0];
             lastCursor = CursorState.none();
+            cursorSaved = false;
         }
 
         // Record that buffer rows [y0, y1) changed; clamped to the buffer in dirtyRegion().
@@ -456,7 +454,7 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         private void paintFull(GraphicsContext gc, RenderStateSnapshot snapshot,
                 double px, double py, double paneWidth, double paneHeight, boolean active) {
             ensure(paneWidth, paneHeight);
-            fillRect(0, 0, width, height, argbPre(PANE_BACKGROUND));
+            fillRect(0, 0, width, height, PANE_BACKGROUND);
             if (snapshot != null) {
                 paintSnapshot(snapshot);
                 drawCursor(snapshot);
@@ -503,6 +501,23 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             present(gc, px, py);
         }
 
+        // Repaint nothing but the cursor: restore the pixels beneath the old cursor to erase it,
+        // then draw the cursor at its new position (which re-saves the pixels under it). Used when
+        // the global dirty flag is FALSE but the cursor alone moved, styled or toggled visibility.
+        // Touches at most the two cursor cell rects, so it never marshals or hashes a full snapshot.
+        private void paintCursorOnly(GraphicsContext gc, RenderStateSnapshot snapshot,
+                double px, double py, double paneWidth, double paneHeight) {
+            ensure(paneWidth, paneHeight);
+            eraseCursorUnder();
+            if (snapshot != null) {
+                drawCursor(snapshot);
+                lastCursor = CursorState.from(snapshot);
+            } else {
+                lastCursor = CursorState.none();
+            }
+            present(gc, px, py);
+        }
+
         private void paintDirty(GraphicsContext gc, RenderTarget target, RenderStateSnapshot snapshot,
                 double px, double py, double paneWidth, double paneHeight, boolean active) {
             ensure(paneWidth, paneHeight);
@@ -539,11 +554,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
                     return;
                 }
             }
-            if (repaintedRowHasCursor(newCursorRow, repainted)
-                    && !repaintCursorRow(snapshot, newCursorRow, repainted)) {
-                paintFullOrShifted(gc, target.snapshotFull(), px, py, paneWidth, paneHeight, active);
-                return;
-            }
             lastCursor = cursor;
             if (needsCursorDraw) {
                 drawCursor(snapshot);
@@ -566,10 +576,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             return true;
         }
 
-        private boolean repaintedRowHasCursor(int rowIndex, boolean[] repainted) {
-            return rowIndex >= 0 && rowIndex < repainted.length && repainted[rowIndex];
-        }
-
         private RenderRow rowByIndex(RenderStateSnapshot snapshot, int rowIndex) {
             for (RenderRow row : snapshot.renderRows()) {
                 if (row.row() == rowIndex) {
@@ -583,7 +589,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             int nextWidth = Math.max(1, (int) Math.round(paneWidth));
             int nextHeight = Math.max(1, (int) Math.round(paneHeight));
             if (nextWidth == width && nextHeight == height && image != null) {
-                ensureGlyphs();
                 return;
             }
 
@@ -593,17 +598,19 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             pixelBuffer = new PixelBuffer<>(width, height, IntBuffer.wrap(pixels), PixelFormat.getIntArgbPreInstance());
             image = new WritableImage(pixelBuffer);
             invalidate();
-            ensureGlyphs();
         }
 
-        private void ensureGlyphs() {
-            int cellWidth = cellWidth();
-            int lineHeight = lineHeight();
-            double baseline = metrics.baselineOffset();
-            if (glyphs == null || glyphs.font != metrics.font()
-                    || glyphs.cellWidth != cellWidth || glyphs.lineHeight != lineHeight || glyphs.baseline != baseline) {
-                glyphs = new GlyphCache(metrics.font(), cellWidth, lineHeight, baseline);
-            }
+        // Drop the full-resolution pixel buffer and its GPU-backed image. The next ensure() rebuilds
+        // them (and a layout frame's paintFull repaints from scratch), so this is safe to call when
+        // the pane goes off-screen; only the shared glyph atlas (in TerminalMetrics) survives.
+        private void release() {
+            pixels = new int[0];
+            pixelBuffer = null;
+            image = null;
+            width = 0;
+            height = 0;
+            invalidate();
+            resetDirty();
         }
 
         private void present(GraphicsContext gc, double px, double py) {
@@ -615,6 +622,12 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             gc.drawImage(image, px, py);
         }
 
+        // Whether the cursor differs from what we last drew (position, style or visibility). Used to
+        // catch cursor-only updates that arrive with a FALSE global dirty flag.
+        private boolean cursorChanged(RenderStateSnapshot snapshot) {
+            return !CursorState.from(snapshot).equals(lastCursor);
+        }
+
         private boolean canDiff(RenderStateSnapshot snapshot) {
             return rowHashes.length == snapshot.rows() && snapshot.renderRows().size() == snapshot.rows();
         }
@@ -695,7 +708,7 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             // per-strip fillRect calls don't touch, so mark the full content band for upload.
             markDirtyRows(top, top + contentHeight);
             if (dy == 0 || Math.abs(dy) >= contentHeight) {
-                fillRect(0, top, width, contentHeight, argbPre(PANE_BACKGROUND));
+                fillRect(0, top, width, contentHeight, PANE_BACKGROUND);
                 return;
             }
 
@@ -706,7 +719,7 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
                 for (int y = 0; y < copyHeight; y++) {
                     System.arraycopy(pixels, (srcY + y) * width, pixels, (dstY + y) * width, width);
                 }
-                fillRect(0, top + copyHeight, width, -dy, argbPre(PANE_BACKGROUND));
+                fillRect(0, top + copyHeight, width, -dy, PANE_BACKGROUND);
             } else {
                 int srcY = top;
                 int dstY = top + dy;
@@ -714,7 +727,7 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
                 for (int y = copyHeight - 1; y >= 0; y--) {
                     System.arraycopy(pixels, (srcY + y) * width, pixels, (dstY + y) * width, width);
                 }
-                fillRect(0, top, width, dy, argbPre(PANE_BACKGROUND));
+                fillRect(0, top, width, dy, PANE_BACKGROUND);
             }
         }
 
@@ -725,8 +738,8 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             }
             int top = contentTop();
             int contentBottom = top + snapshot.rows() * lineHeight();
-            fillRect(0, 0, width, top, argbPre(rowEdgeBackground(rows.get(0), true)));
-            fillRect(0, contentBottom, width, height - contentBottom, argbPre(rowEdgeBackground(rows.get(rows.size() - 1), true)));
+            fillRect(0, 0, width, top, rowEdgeBackground(rows.get(0), true));
+            fillRect(0, contentBottom, width, height - contentBottom, rowEdgeBackground(rows.get(rows.size() - 1), true));
             for (RenderRow row : rows) {
                 paintRow(row);
             }
@@ -735,13 +748,13 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         private void paintRow(RenderRow row) {
             int rowTop = contentTop() + (row.row() * lineHeight());
             int rowHeight = lineHeight();
-            fillRect(0, rowTop, width, rowHeight, argbPre(PANE_BACKGROUND));
+            fillRect(0, rowTop, width, rowHeight, PANE_BACKGROUND);
             if (row.row() == 0) {
-                fillRect(0, 0, width, contentTop(), argbPre(rowEdgeBackground(row, true)));
+                fillRect(0, 0, width, contentTop(), rowEdgeBackground(row, true));
             }
             if (row.row() == rowHashes.length - 1) {
                 int bottom = contentTop() + (rowHashes.length * lineHeight());
-                fillRect(0, bottom, width, height - bottom, argbPre(rowEdgeBackground(row, true)));
+                fillRect(0, bottom, width, height - bottom, rowEdgeBackground(row, true));
             }
             paintRowSidePadding(row, rowTop, rowHeight);
             paintRowBackgrounds(row, rowTop, rowHeight);
@@ -755,31 +768,30 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             }
             int left = contentLeft();
             int contentRight = left + (cells.size() * cellWidth());
-            fillRect(0, rowTop, left, rowHeight, argbPre(rowEdgeBackground(row, true)));
-            fillRect(contentRight, rowTop, width - contentRight, rowHeight, argbPre(rowEdgeBackground(row, false)));
+            fillRect(0, rowTop, left, rowHeight, rowEdgeBackground(row, true));
+            fillRect(contentRight, rowTop, width - contentRight, rowHeight, rowEdgeBackground(row, false));
         }
 
         private void paintRowBackgrounds(RenderRow row, int rowTop, int rowHeight) {
-            int cellWidth = cellWidth();
-            Color runBackground = null;
+            int runBackground = 0;
             int runStartColumn = 0;
             int previousColumn = -1;
             for (RenderCell cell : row.cells()) {
                 if (cell.kittyPlaceholder().isPresent()) {
                     flushBackground(runBackground, runStartColumn, previousColumn, rowTop, rowHeight);
-                    runBackground = null;
+                    runBackground = 0;
                     previousColumn = -1;
                     continue;
                 }
 
-                Color bg = cell.selected() ? SELECTED_BACKGROUND : cellBackgroundOverride(cell);
-                if (bg == null) {
+                int bg = cell.selected() ? SELECTED_BACKGROUND : cellBackgroundOverride(cell);
+                if (bg == 0) {
                     flushBackground(runBackground, runStartColumn, previousColumn, rowTop, rowHeight);
-                    runBackground = null;
+                    runBackground = 0;
                     previousColumn = -1;
                     continue;
                 }
-                if (runBackground == null || bg != runBackground || cell.column() != previousColumn + 1) {
+                if (bg != runBackground || cell.column() != previousColumn + 1) {
                     flushBackground(runBackground, runStartColumn, previousColumn, rowTop, rowHeight);
                     runBackground = bg;
                     runStartColumn = cell.column();
@@ -789,12 +801,12 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             flushBackground(runBackground, runStartColumn, previousColumn, rowTop, rowHeight);
         }
 
-        private void flushBackground(Color background, int startColumn, int endColumn, int rowTop, int rowHeight) {
-            if (background == null || endColumn < startColumn) {
+        private void flushBackground(int background, int startColumn, int endColumn, int rowTop, int rowHeight) {
+            if (background == 0 || endColumn < startColumn) {
                 return;
             }
             fillRect(contentLeft() + (startColumn * cellWidth()), rowTop,
-                    (endColumn - startColumn + 1) * cellWidth(), rowHeight, argbPre(background));
+                    (endColumn - startColumn + 1) * cellWidth(), rowHeight, background);
         }
 
         private void paintRowText(RenderRow row, int rowTop) {
@@ -804,30 +816,31 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
                 if (cell.kittyPlaceholder().isPresent() || cell.codepoints().length == 0) {
                     continue;
                 }
-                Glyph glyph = glyphs.glyph(cell.text());
-                int color = rgb(cellForegroundColor(cell));
-                blitGlyph(glyph, x0 + (cell.column() * cellWidth), rowTop, color);
+                GlyphCache.Glyph glyph = metrics.glyphCache().glyph(cell.text());
+                blitGlyph(glyph, x0 + (cell.column() * cellWidth), rowTop, cellForegroundColor(cell));
             }
         }
 
-        private void blitGlyph(Glyph glyph, int x, int y, int rgb) {
+        private void blitGlyph(GlyphCache.Glyph glyph, int x, int y, int rgb) {
             int red = (rgb >> 16) & 0xff;
             int green = (rgb >> 8) & 0xff;
             int blue = rgb & 0xff;
             // Clamp the glyph rectangle to the buffer once, so the inner loops carry no
             // per-pixel bounds check (this is the hottest pixel loop on a text repaint).
+            int glyphWidth = glyph.width();
+            byte[] glyphAlpha = glyph.alpha();
             int gyStart = Math.max(0, -y);
-            int gyEnd = Math.min(glyph.height, height - y);
+            int gyEnd = Math.min(glyph.height(), height - y);
             int gxStart = Math.max(0, -x);
-            int gxEnd = Math.min(glyph.width, width - x);
+            int gxEnd = Math.min(glyphWidth, width - x);
             if (gyStart >= gyEnd || gxStart >= gxEnd) {
                 return;
             }
             for (int gy = gyStart; gy < gyEnd; gy++) {
                 int rowOffset = (y + gy) * width;
-                int glyphOffset = gy * glyph.width;
+                int glyphOffset = gy * glyphWidth;
                 for (int gx = gxStart; gx < gxEnd; gx++) {
-                    int alpha = glyph.alpha[glyphOffset + gx] & 0xff;
+                    int alpha = glyphAlpha[glyphOffset + gx] & 0xff;
                     if (alpha == 0) {
                         continue;
                     }
@@ -857,20 +870,63 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             int y = contentTop() + ((int) snapshot.cursorViewportY() * lineHeight());
             int cw = cellWidth();
             int lh = lineHeight();
+            // Capture the cell box under the cursor before drawing, so a later cursor-only frame
+            // can restore it without repainting the row. The box is a superset of every style's
+            // footprint below, so the restore erases whichever style was actually drawn.
+            saveCursorUnder(x, y, cw, lh);
             RenderCursorStyle style = snapshot.cursorStyle();
             if (style == RenderCursorStyle.BAR) {
-                fillRect(x, y + 2, 1, Math.max(1, lh - 4), argbPre(DEFAULT_FOREGROUND));
+                fillRect(x, y + 2, 1, Math.max(1, lh - 4), DEFAULT_FOREGROUND);
             } else if (style == RenderCursorStyle.UNDERLINE) {
-                fillRect(x + 1, y + lh - 2, Math.max(1, cw - 2), 1, argbPre(DEFAULT_FOREGROUND));
+                fillRect(x + 1, y + lh - 2, Math.max(1, cw - 2), 1, DEFAULT_FOREGROUND);
             } else if (style == RenderCursorStyle.BLOCK) {
-                fillRectAlpha(x, y + 1, Math.max(1, cw - 1), Math.max(1, lh - 2), CURSOR_FILL);
+                fillRectAlpha(x, y + 1, Math.max(1, cw - 1), Math.max(1, lh - 2), DEFAULT_FOREGROUND, CURSOR_FILL_ALPHA);
             } else {
-                strokeRect(x, y + 1, Math.max(1, cw - 1), Math.max(1, lh - 2), argbPre(DEFAULT_FOREGROUND), 1);
+                strokeRect(x, y + 1, Math.max(1, cw - 1), Math.max(1, lh - 2), DEFAULT_FOREGROUND, 1);
             }
         }
 
+        // Copy the clamped cell box under the cursor into the save-under buffer. Marks no dirty
+        // band — saving reads pixels, it doesn't change them.
+        private void saveCursorUnder(int x, int y, int w, int h) {
+            int x0 = Math.max(0, x);
+            int y0 = Math.max(0, y);
+            int x1 = Math.min(width, x + w);
+            int y1 = Math.min(height, y + h);
+            if (x0 >= x1 || y0 >= y1) {
+                cursorSaved = false;
+                return;
+            }
+            int rw = x1 - x0;
+            int rh = y1 - y0;
+            if (cursorUnder.length < rw * rh) {
+                cursorUnder = new int[rw * rh];
+            }
+            for (int row = 0; row < rh; row++) {
+                System.arraycopy(pixels, ((y0 + row) * width) + x0, cursorUnder, row * rw, rw);
+            }
+            cursorUnderX = x0;
+            cursorUnderY = y0;
+            cursorUnderW = rw;
+            cursorUnderH = rh;
+            cursorSaved = true;
+        }
+
+        // Restore the saved cell box, erasing the cursor that was drawn over it. No-op if nothing
+        // is currently saved (cursor hidden, or buffer reset since the last draw).
+        private void eraseCursorUnder() {
+            if (!cursorSaved) {
+                return;
+            }
+            for (int row = 0; row < cursorUnderH; row++) {
+                System.arraycopy(cursorUnder, row * cursorUnderW, pixels, ((cursorUnderY + row) * width) + cursorUnderX, cursorUnderW);
+            }
+            markDirtyRows(cursorUnderY, cursorUnderY + cursorUnderH);
+            cursorSaved = false;
+        }
+
         private void drawBorder(boolean active) {
-            strokeRect(0, 0, width, height, argbPre(active ? ACTIVE_BORDER : INACTIVE_BORDER), active ? 2 : 1);
+            strokeRect(0, 0, width, height, active ? ACTIVE_BORDER : INACTIVE_BORDER, active ? 2 : 1);
         }
 
         private void strokeRect(int x, int y, int w, int h, int color, int lineWidth) {
@@ -887,9 +943,7 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             }
         }
 
-        private void fillRectAlpha(int x, int y, int w, int h, Color color) {
-            int alpha = (int) Math.round(color.getOpacity() * 255.0);
-            int rgb = rgb(color);
+        private void fillRectAlpha(int x, int y, int w, int h, int rgb, int alpha) {
             int red = (rgb >> 16) & 0xff;
             int green = (rgb >> 8) & 0xff;
             int blue = rgb & 0xff;
@@ -947,53 +1001,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         }
     }
 
-    private final class GlyphCache {
-        private final javafx.scene.text.Font font;
-        private final int cellWidth;
-        private final int lineHeight;
-        private final double baseline;
-        private final Map<String, Glyph> glyphs = new HashMap<>();
-
-        private GlyphCache(javafx.scene.text.Font font, int cellWidth, int lineHeight, double baseline) {
-            this.font = font;
-            this.cellWidth = cellWidth;
-            this.lineHeight = lineHeight;
-            this.baseline = baseline;
-        }
-
-        private Glyph glyph(String text) {
-            return glyphs.computeIfAbsent(text, this::renderGlyph);
-        }
-
-        private Glyph renderGlyph(String value) {
-            Text measured = new Text(value);
-            measured.setFont(font);
-            int glyphWidth = Math.max(cellWidth, (int) Math.ceil(measured.getLayoutBounds().getWidth()) + 2);
-            Canvas canvas = new Canvas(glyphWidth, lineHeight);
-            GraphicsContext gc = canvas.getGraphicsContext2D();
-            gc.setFontSmoothingType(FontSmoothingType.GRAY);
-            gc.setFont(font);
-            gc.setFill(Color.WHITE);
-            gc.fillText(value, 0.0, baseline);
-
-            SnapshotParameters parameters = new SnapshotParameters();
-            parameters.setFill(Color.TRANSPARENT);
-            WritableImage snapshot = canvas.snapshot(parameters, null);
-            PixelReader reader = snapshot.getPixelReader();
-            byte[] alpha = new byte[glyphWidth * lineHeight];
-            for (int y = 0; y < lineHeight; y++) {
-                int offset = y * glyphWidth;
-                for (int x = 0; x < glyphWidth; x++) {
-                    alpha[offset + x] = (byte) ((reader.getArgb(x, y) >>> 24) & 0xff);
-                }
-            }
-            return new Glyph(glyphWidth, lineHeight, alpha);
-        }
-    }
-
-    private record Glyph(int width, int height, byte[] alpha) {
-    }
-
     private record CursorState(boolean visible, boolean hasViewport, int column, int row, RenderCursorStyle style) {
         private static CursorState none() {
             return new CursorState(false, false, -1, -1, null);
@@ -1042,21 +1049,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         return hash * 0x100000001b3L;
     }
 
-    private static int rgb(Color color) {
-        int red = (int) Math.round(color.getRed() * 255.0);
-        int green = (int) Math.round(color.getGreen() * 255.0);
-        int blue = (int) Math.round(color.getBlue() * 255.0);
-        return (red << 16) | (green << 8) | blue;
-    }
-
-    private static int argbPre(Color color) {
-        int alpha = (int) Math.round(color.getOpacity() * 255.0);
-        int red = (int) Math.round(color.getRed() * alpha);
-        int green = (int) Math.round(color.getGreen() * alpha);
-        int blue = (int) Math.round(color.getBlue() * alpha);
-        return (alpha << 24) | (red << 16) | (green << 8) | blue;
-    }
-
     // 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

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

@@ -0,0 +1,104 @@
+package com.gregor.jprototerm;
+
+import javafx.scene.SnapshotParameters;
+import javafx.scene.canvas.Canvas;
+import javafx.scene.canvas.GraphicsContext;
+import javafx.scene.image.PixelReader;
+import javafx.scene.image.WritableImage;
+import javafx.scene.paint.Color;
+import javafx.scene.text.Font;
+import javafx.scene.text.FontSmoothingType;
+import javafx.scene.text.Text;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Rasterized glyph alpha masks for one window's font, shared by every pane's renderer. The atlas is
+ * a pure function of the window's {@link TerminalMetrics} (font family/size, snapped cell geometry,
+ * baseline), and all panes in a window observe the same metrics, so a single shared cache lets N
+ * panes reuse one copy of each glyph instead of each rasterizing and retaining its own. It also
+ * means a pane whose backbuffer was released (see {@link GhosttyTerminalRenderer}) does not have to
+ * re-rasterize glyphs when it is shown again.
+ *
+ * <p>Rasterizing goes through JavaFX ({@link Canvas#snapshot}), so {@link #glyph} must be called on
+ * the FX thread — which is where all rendering happens. The cache self-invalidates when the metrics
+ * change (e.g. a font switch): the next lookup notices and clears.
+ */
+final class GlyphCache {
+    record Glyph(int width, int height, byte[] alpha) {
+    }
+
+    // Bounds the atlas so pathological glyph diversity (e.g. a dump of distinct CJK/emoji cells)
+    // can't grow it without limit; on overflow it clears and rebuilds on demand, like any
+    // metrics change.
+    private static final int MAX_GLYPHS = 4096;
+
+    private final TerminalMetrics metrics;
+    private final Map<String, Glyph> glyphs = new HashMap<>();
+    // The metrics snapshot the cached glyphs were rasterized for; a mismatch clears the cache.
+    private Font font;
+    private int cellWidth;
+    private int lineHeight;
+    private double baseline;
+
+    GlyphCache(TerminalMetrics metrics) {
+        this.metrics = metrics;
+    }
+
+    Glyph glyph(String text) {
+        ensureCurrent();
+        Glyph cached = glyphs.get(text);
+        if (cached != null) {
+            return cached;
+        }
+        if (glyphs.size() >= MAX_GLYPHS) {
+            glyphs.clear();
+        }
+        Glyph rendered = renderGlyph(text);
+        glyphs.put(text, rendered);
+        return rendered;
+    }
+
+    // Drop the rasterized masks if the font/cell geometry changed since they were built. Cheap to
+    // call per lookup: a no-op unless the window's metrics actually changed under us.
+    private void ensureCurrent() {
+        Font currentFont = metrics.font();
+        int currentCellWidth = Math.max(1, (int) Math.round(metrics.cellWidth()));
+        int currentLineHeight = Math.max(1, (int) Math.round(metrics.lineHeight()));
+        double currentBaseline = metrics.baselineOffset();
+        if (currentFont != font || currentCellWidth != cellWidth
+                || currentLineHeight != lineHeight || currentBaseline != baseline) {
+            font = currentFont;
+            cellWidth = currentCellWidth;
+            lineHeight = currentLineHeight;
+            baseline = currentBaseline;
+            glyphs.clear();
+        }
+    }
+
+    private Glyph renderGlyph(String value) {
+        Text measured = new Text(value);
+        measured.setFont(font);
+        int glyphWidth = Math.max(cellWidth, (int) Math.ceil(measured.getLayoutBounds().getWidth()) + 2);
+        Canvas canvas = new Canvas(glyphWidth, lineHeight);
+        GraphicsContext gc = canvas.getGraphicsContext2D();
+        gc.setFontSmoothingType(FontSmoothingType.GRAY);
+        gc.setFont(font);
+        gc.setFill(Color.WHITE);
+        gc.fillText(value, 0.0, baseline);
+
+        SnapshotParameters parameters = new SnapshotParameters();
+        parameters.setFill(Color.TRANSPARENT);
+        WritableImage snapshot = canvas.snapshot(parameters, null);
+        PixelReader reader = snapshot.getPixelReader();
+        byte[] alpha = new byte[glyphWidth * lineHeight];
+        for (int y = 0; y < lineHeight; y++) {
+            int offset = y * glyphWidth;
+            for (int x = 0; x < glyphWidth; x++) {
+                alpha[offset + x] = (byte) ((reader.getArgb(x, y) >>> 24) & 0xff);
+            }
+        }
+        return new Glyph(glyphWidth, lineHeight, alpha);
+    }
+}

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

@@ -5,17 +5,19 @@ import javafx.scene.input.KeyEvent;
 
 import java.util.Locale;
 
-public record KeyBinding(boolean alt, boolean control, boolean shift, KeyCode code) {
+public record KeyBinding(boolean alt, boolean control, boolean shift, boolean meta, KeyCode code) {
     public static KeyBinding parse(String value) {
         boolean alt = false;
         boolean control = false;
         boolean shift = false;
+        boolean meta = false;
         KeyCode code = null;
 
         for (String part : value.split("\\+")) {
             String token = part.trim().toUpperCase(Locale.ROOT);
             switch (token) {
-                case "ALT", "META" -> alt = true;
+                case "ALT" -> alt = true;
+                case "META", "SUPER" -> meta = true;
                 case "CTRL", "CONTROL" -> control = true;
                 case "SHIFT" -> shift = true;
                 default -> code = keyCode(token);
@@ -25,13 +27,14 @@ public record KeyBinding(boolean alt, boolean control, boolean shift, KeyCode co
         if (code == null) {
             throw new IllegalArgumentException("Key binding has no key code: " + value);
         }
-        return new KeyBinding(alt, control, shift, code);
+        return new KeyBinding(alt, control, shift, meta, code);
     }
 
     public boolean matches(KeyEvent event) {
         return event.isAltDown() == alt
                 && event.isControlDown() == control
                 && event.isShiftDown() == shift
+                && event.isMetaDown() == meta
                 && event.getCode() == code;
     }
 
@@ -44,6 +47,9 @@ public record KeyBinding(boolean alt, boolean control, boolean shift, KeyCode co
         if (alt) {
             builder.append("ALT+");
         }
+        if (meta) {
+            builder.append("META+");
+        }
         if (shift) {
             builder.append("SHIFT+");
         }

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

@@ -15,6 +15,8 @@ import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 /**
  * A Linux PTY backed by libc via the Foreign Function & Memory API.
@@ -33,6 +35,11 @@ import java.util.Map;
 public final class LinuxPty implements AutoCloseable {
     static final Linker LINKER = Linker.nativeLinker();
     private static final SymbolLookup LIBC = LINKER.defaultLookup();
+    private static final ExecutorService REAPER = Executors.newCachedThreadPool(runnable -> {
+        Thread thread = new Thread(runnable, "pty-reaper");
+        thread.setDaemon(true);
+        return thread;
+    });
 
     static final AddressLayout C_POINTER = (AddressLayout) LINKER.canonicalLayouts().get("void*");
     static final ValueLayout.OfShort C_SHORT = (ValueLayout.OfShort) LINKER.canonicalLayouts().get("short");
@@ -63,7 +70,10 @@ public final class LinuxPty implements AutoCloseable {
     private static final long TIOCSWINSZ = 0x5414L;
     private static final short POSIX_SPAWN_SETSID = 0x80;
     private static final int SIGHUP = 1;
+    private static final int SIGINT = 2;
+    private static final int SIGQUIT = 3;
     private static final int SIGKILL = 9;
+    private static final int SIGTERM = 15;
     private static final int WNOHANG = 1;
 
     // struct winsize { unsigned short ws_row, ws_col, ws_xpixel, ws_ypixel; }
@@ -105,11 +115,36 @@ public final class LinuxPty implements AutoCloseable {
     private final Object writeLock = new Object();
     private final int masterFd;
     private final int pid;
+    private final int closeSignal;
     private volatile boolean closed;
 
-    private LinuxPty(int masterFd, int pid) {
+    private LinuxPty(int masterFd, int pid, int closeSignal) {
         this.masterFd = masterFd;
         this.pid = pid;
+        this.closeSignal = closeSignal;
+    }
+
+    /**
+     * Resolves a signal name (e.g. {@code "SIGTERM"}, {@code "TERM"}, {@code "SIGKILL"}) to its
+     * Linux signal number, or {@code -1} if the name is not one we recognise. Case-insensitive and
+     * tolerant of a missing {@code SIG} prefix.
+     */
+    public static int signalNumber(String name) {
+        if (name == null) {
+            return -1;
+        }
+        String normalized = name.trim().toUpperCase(java.util.Locale.ROOT);
+        if (normalized.startsWith("SIG")) {
+            normalized = normalized.substring(3);
+        }
+        return switch (normalized) {
+            case "HUP" -> SIGHUP;
+            case "INT" -> SIGINT;
+            case "QUIT" -> SIGQUIT;
+            case "KILL" -> SIGKILL;
+            case "TERM" -> SIGTERM;
+            default -> -1;
+        };
     }
 
     /**
@@ -118,8 +153,10 @@ public final class LinuxPty implements AutoCloseable {
      * @param argv command and arguments (e.g. {@code {"/bin/zsh", "-i"}})
      * @param environment environment for the child, as KEY=VALUE pairs
      * @param workingDirectory directory the child starts in, or {@code null} to inherit
+     * @param closeSignal signal number sent to the child on {@link #close()} (e.g. SIGTERM)
      */
-    public static LinuxPty spawn(String[] argv, Map<String, String> environment, String workingDirectory) {
+    public static LinuxPty spawn(String[] argv, Map<String, String> environment, String workingDirectory,
+            int closeSignal) {
         Arena setup = Arena.ofConfined();
         try {
             int master = check(callInt(POSIX_OPENPT, O_RDWR | O_NOCTTY), "posix_openpt");
@@ -158,7 +195,7 @@ public final class LinuxPty implements AutoCloseable {
                     if (rc != 0) {
                         throw new IllegalStateException("posix_spawnp failed for " + argv[0] + " (rc=" + rc + ")");
                     }
-                    return new LinuxPty(master, pidOut.get(C_INT, 0));
+                    return new LinuxPty(master, pidOut.get(C_INT, 0), closeSignal);
                 } finally {
                     callInt(ATTR_DESTROY, attr);
                     callInt(FA_DESTROY, actions);
@@ -245,14 +282,47 @@ public final class LinuxPty implements AutoCloseable {
 
     @Override
     public void close() {
-        if (closed) {
+        if (!markClosed()) {
             return;
         }
+        closeMaster();
+        try {
+            reap();
+        } finally {
+            arena.close();
+        }
+    }
+
+    /** Send the configured close signal and close the master fd now; reap off the caller thread. */
+    public void closeDetached() {
+        if (!markClosed()) {
+            return;
+        }
+        closeMaster();
+        REAPER.submit(() -> {
+            try {
+                reap();
+            } finally {
+                arena.close();
+            }
+        });
+    }
+
+    private synchronized boolean markClosed() {
+        if (closed) {
+            return false;
+        }
         closed = true;
-        callKill(pid, SIGHUP);
+        return true;
+    }
+
+    private void closeMaster() {
+        // Note: closing the master fd does NOT wake a reader thread blocked in read() on it —
+        // the reader unblocks via EOF when the child exits and the slave end closes. The signal
+        // here usually does that; if the child ignores it, the SIGKILL escalation in reap()
+        // guarantees it shortly after.
+        callKill(pid, closeSignal);
         callInt(CLOSE, masterFd);
-        reap();
-        arena.close();
     }
 
     private void reap() {

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

@@ -1,251 +1,36 @@
 package com.gregor.jprototerm;
 
-import javafx.animation.AnimationTimer;
-import javafx.application.Application;
-import javafx.application.Platform;
-import javafx.geometry.Rectangle2D;
-import javafx.scene.Scene;
-import javafx.scene.control.ButtonType;
-import javafx.scene.control.ComboBox;
-import javafx.scene.control.Dialog;
-import javafx.scene.control.Label;
-import javafx.scene.control.Spinner;
-import javafx.scene.control.SpinnerValueFactory;
-import javafx.scene.input.Clipboard;
-import javafx.scene.input.KeyEvent;
-import javafx.scene.layout.GridPane;
-import javafx.scene.layout.StackPane;
-import javafx.scene.text.Font;
-import javafx.stage.Screen;
-import javafx.stage.Stage;
-
-import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.util.List;
-
-public final class Main extends Application {
-    private Compositor compositor;
-    private TerminalMetrics metrics;
-    private AppConfig config;
-
-    @Override
-    public void start(Stage stage) {
-        config = AppConfig.load();
-
-        metrics = new TerminalMetrics(config.fontFamily(), config.fontSize());
-        compositor = new Compositor(config, metrics);
-        // When the last pane closes — whether via the close-pane key or because a pane's process
-        // exited on its own — tear down and quit.
-        compositor.setOnEmpty(() -> {
-            compositor.close();
-            Platform.exit();
-        });
-
-        StackPane root = new StackPane(compositor.canvas(), compositor.imageOverlay());
-        compositor.canvas().widthProperty().bind(root.widthProperty());
-        compositor.canvas().heightProperty().bind(root.heightProperty());
-
-        Scene scene = new Scene(root, config.windowWidth(), config.windowHeight());
-        scene.addEventFilter(KeyEvent.KEY_PRESSED, this::handlePressed);
-        scene.addEventFilter(KeyEvent.KEY_TYPED, event -> handleTyped(event));
-
-        new AnimationTimer() {
-            @Override
-            public void handle(long now) {
-                compositor.render();
-            }
-        }.start();
-
-        stage.setTitle("jprototerm");
-        stage.setScene(scene);
-        stage.setOnCloseRequest(event -> {
-            compositor.close();
-        });
-        // JavaFX centres a new stage on the primary screen; on X11 there's no "focused monitor"
-        // to honour, so place it on the screen under the mouse pointer instead.
-        centreOnActiveScreen(stage, config.windowWidth(), config.windowHeight());
-        stage.show();
-        // Ask the window manager to raise and focus the new window so the user can type right
-        // away; the canvas requestFocus() below only routes events within the scene.
-        stage.toFront();
-        stage.requestFocus();
-        compositor.canvas().requestFocus();
-    }
-
-    // Centre the stage within the screen the mouse pointer is on (the best proxy for the
-    // "active" monitor on X11, which exposes no focused-monitor concept to JavaFX).
-    private static void centreOnActiveScreen(Stage stage, double width, double height) {
-        Rectangle2D bounds = activeScreen().getVisualBounds();
-        stage.setX(bounds.getMinX() + ((bounds.getWidth() - width) / 2.0));
-        stage.setY(bounds.getMinY() + ((bounds.getHeight() - height) / 2.0));
-    }
-
-    private static Screen activeScreen() {
-        int[] at = X11Pointer.query();
-        if (at != null) {
-            // libX11 and JavaFX share a coordinate space on the X11 virtual screen.
-            List<Screen> screens = Screen.getScreensForRectangle(at[0], at[1], 1.0, 1.0);
-            if (!screens.isEmpty()) {
-                return screens.get(0);
-            }
-        }
-        return Screen.getPrimary();
-    }
-
-    private void handlePressed(KeyEvent event) {
-        if (config.keybindings().get("navigate_left").matches(event)) {
-            compositor.navigate(Direction.LEFT);
-            event.consume();
-        } else if (config.keybindings().get("navigate_down").matches(event)) {
-            compositor.navigate(Direction.DOWN);
-            event.consume();
-        } else if (config.keybindings().get("navigate_up").matches(event)) {
-            compositor.navigate(Direction.UP);
-            event.consume();
-        } else if (config.keybindings().get("navigate_right").matches(event)) {
-            compositor.navigate(Direction.RIGHT);
-            event.consume();
-        } else if (config.keybindings().get("toggle_floating").matches(event)) {
-            compositor.toggleFloating();
-            event.consume();
-        } else if (config.keybindings().get("new_pane").matches(event)) {
-            compositor.createPane();
-            event.consume();
-        } else if (config.keybindings().get("next_floating").matches(event)) {
-            compositor.nextFloatingPane();
-            event.consume();
-        } else if (config.keybindings().get("promote_floating").matches(event)) {
-            compositor.promoteActiveFloating();
-            event.consume();
-        } else if (config.keybindings().get("close_pane").matches(event)) {
-            // Closing the last pane quits the app, via the compositor's onEmpty hook.
-            compositor.closeActivePane();
-            event.consume();
-        } else if (config.keybindings().get("new_tab").matches(event)) {
-            compositor.newTab();
-            event.consume();
-        } else if (config.keybindings().get("previous_tab").matches(event)) {
-            compositor.previousTab();
-            event.consume();
-        } else if (config.keybindings().get("next_tab").matches(event)) {
-            compositor.nextTab();
-            event.consume();
-        } else if (config.keybindings().get("open_font_selector").matches(event)) {
-            openFontSelector();
-            event.consume();
-        } else if (config.keybindings().get("open_scrollback").matches(event)) {
-            openScrollbackInEditor();
-            event.consume();
-        } else if (config.keybindings().get("paste").matches(event)) {
-            pasteFromClipboard();
-            event.consume();
-        } else {
-            String encoded = KeyEncoder.encode(event);
-            if (encoded != null) {
-                compositor.activePane().send(encoded);
-                event.consume();
-            }
-        }
-    }
-
-    private void handleTyped(KeyEvent event) {
-        if (event.isAltDown() || event.isControlDown() || event.isMetaDown()) {
-            return;
-        }
-
-        String text = event.getCharacter();
-        if (text != null && !text.isEmpty() && text.charAt(0) >= 0x20 && text.charAt(0) != 0x7f) {
-            compositor.activePane().send(text);
-            event.consume();
-        }
-    }
-
-    private void pasteFromClipboard() {
-        Clipboard clipboard = Clipboard.getSystemClipboard();
-        if (clipboard.hasString()) {
-            compositor.activePane().paste(clipboard.getString());
-        }
-    }
-
-    private void openFontSelector() {
-        Dialog<ButtonType> dialog = new Dialog<>();
-        dialog.setTitle("Font");
-        dialog.getDialogPane().getButtonTypes().addAll(ButtonType.OK, ButtonType.CANCEL);
-
-        ComboBox<String> family = new ComboBox<>();
-        family.getItems().setAll(Font.getFamilies());
-        family.setEditable(true);
-        family.setMaxWidth(Double.MAX_VALUE);
-        family.setValue(config.fontFamily());
-
-        Spinner<Double> size = new Spinner<>();
-        size.setEditable(true);
-        size.setValueFactory(new SpinnerValueFactory.DoubleSpinnerValueFactory(6.0, 48.0, config.fontSize(), 0.5));
-
-        GridPane content = new GridPane();
-        content.setHgap(10.0);
-        content.setVgap(10.0);
-        content.add(new Label("Family"), 0, 0);
-        content.add(family, 1, 0);
-        content.add(new Label("Size"), 0, 1);
-        content.add(size, 1, 1);
-        dialog.getDialogPane().setContent(content);
-
-        dialog.showAndWait()
-                .filter(button -> button == ButtonType.OK)
-                .ifPresent(ignored -> {
-                    String selectedFamily = family.getEditor().getText();
-                    if (selectedFamily == null || selectedFamily.isBlank()) {
-                        selectedFamily = family.getValue();
-                    }
-                    if (selectedFamily == null || selectedFamily.isBlank()) {
-                        return;
-                    }
-
-                    double selectedSize = size.getValue();
-                    config = config.withFont(selectedFamily.trim(), selectedSize);
-                    config.save();
-                    compositor.setFont(config.fontFamily(), config.fontSize());
-                    compositor.canvas().requestFocus();
-                });
-    }
-
-    private void openScrollbackInEditor() {
-        try {
-            // Capture the active pane's scrollback before opening the floating pane, since that
-            // makes the new pane active.
-            Path file = Files.createTempFile("jprototerm-scrollback-", ".txt");
-            Files.writeString(file, compositor.activePane().scrollbackText());
-            file.toFile().deleteOnExit();
-
-            // Run the editor as the floating pane's process (via /bin/sh -c) rather than typing the
-            // command into an interactive shell. The command runs deterministically from the start
-            // — no shell startup/rc race — and the pane auto-closes when the editor exits.
-            compositor.openFloatingPane(scrollbackEditorCommand(file));
-        } catch (IOException ex) {
-            System.err.println("Could not open scrollback in editor: " + ex.getMessage());
-        }
-    }
-
-    private String scrollbackEditorCommand(Path file) {
-        String quotedFile = shellQuote(file.toString());
-        String command = config.scrollbackEditorCommand();
-        if (command == null || command.isBlank()) {
-            command = "vi {file}";
-        }
-        if (command.contains("{file}")) {
-            return command.replace("{file}", quotedFile);
-        }
-        return command + " " + quotedFile;
-    }
-
-    private static String shellQuote(String value) {
-        return "'" + value.replace("'", "'\"'\"'") + "'";
+/**
+ * Entry point and mode dispatch. A bare invocation is a thin client: it hands the request to a
+ * running {@link Daemon}, or, if none is reachable, opens a single standalone window in this process
+ * (today's behavior). {@code --daemon} runs the long-lived server that hosts every window in one
+ * JVM, so client launches skip cold JVM/JavaFX/GL startup. {@code --standalone} skips daemon client
+ * mode and always opens an in-process window, which is useful while testing development builds.
+ */
+public final class Main {
+    private Main() {
     }
 
     public static void main(String[] args) {
+        // Match the renderer order the app was tuned for; honor an explicit override if present.
         System.setProperty("prism.order", System.getProperty("prism.order", "es2,sw"));
-        launch(Main.class, args);
+
+        boolean standalone = false;
+        for (String arg : args) {
+            if (arg.equals("--daemon")) {
+                Daemon.run();
+                return;
+            }
+            if (arg.equals("--standalone")) {
+                standalone = true;
+            }
+        }
+
+        String workingDirectory = System.getProperty("user.dir");
+        if (!standalone && Daemon.tryClient(workingDirectory)) {
+            return; // a running daemon opened the window
+        }
+        // No daemon reachable: fall back to a standalone window; the JVM exits when it closes.
+        WindowManager.start(WindowManager.Mode.STANDALONE).openWindow(workingDirectory);
     }
 }

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

@@ -27,9 +27,10 @@ public final class ShellSession implements AutoCloseable {
      * config, not assumed here.
      */
     public static ShellSession start(List<String> shellCommand, Map<String, String> envOverride, TerminalPane pane,
-            int columns, int rows, String workingDirectory) {
+            int columns, int rows, String workingDirectory, int closeSignal) {
         try {
-            return spawn(shellCommand.toArray(new String[0]), envOverride, columns, rows, workingDirectory);
+            return spawn(shellCommand.toArray(new String[0]), envOverride, columns, rows, workingDirectory,
+                    closeSignal);
         } catch (RuntimeException ex) {
             pane.write("failed to start shell: " + ex.getMessage() + "\r\n");
             throw new IllegalStateException("Could not start shell " + String.join(" ", shellCommand), ex);
@@ -45,9 +46,10 @@ public final class ShellSession implements AutoCloseable {
      * flags. {@code command} must not be null.
      */
     public static ShellSession startCommand(Map<String, String> envOverride, TerminalPane pane,
-            int columns, int rows, String workingDirectory, String command) {
+            int columns, int rows, String workingDirectory, String command, int closeSignal) {
         try {
-            return spawn(new String[] {"/bin/sh", "-c", command}, envOverride, columns, rows, workingDirectory);
+            return spawn(new String[] {"/bin/sh", "-c", command}, envOverride, columns, rows, workingDirectory,
+                    closeSignal);
         } catch (RuntimeException ex) {
             pane.write("failed to run command: " + ex.getMessage() + "\r\n");
             throw new IllegalStateException("Could not run command: " + command, ex);
@@ -55,7 +57,7 @@ public final class ShellSession implements AutoCloseable {
     }
 
     private static ShellSession spawn(String[] argv, Map<String, String> envOverride,
-            int columns, int rows, String workingDirectory) {
+            int columns, int rows, String workingDirectory, int closeSignal) {
         Map<String, String> environment = new HashMap<>(System.getenv());
         environment.put("TERM", "xterm-kitty");
         environment.put("COLORTERM", "truecolor");
@@ -65,7 +67,8 @@ public final class ShellSession implements AutoCloseable {
         LinuxPty pty = LinuxPty.spawn(
                 argv,
                 environment,
-                workingDirectory != null ? workingDirectory : System.getProperty("user.home"));
+                workingDirectory != null ? workingDirectory : System.getProperty("user.home"),
+                closeSignal);
         ShellSession session = new ShellSession(pty);
         session.resize(columns, rows);
         return session;
@@ -93,6 +96,26 @@ public final class ShellSession implements AutoCloseable {
         // These are jprototerm's own runtime settings, not the user's shell environment.
         environment.remove("GDK_BACKEND");
         environment.remove("JLIBGHOSTTY_LIBRARY");
+        sanitizeJavaToolOptions(environment);
+    }
+
+    private static void sanitizeJavaToolOptions(Map<String, String> environment) {
+        String javaToolOptions = environment.get("JAVA_TOOL_OPTIONS");
+        if (javaToolOptions == null
+                || !javaToolOptions.contains("-XX:SharedArchiveFile=")
+                || !javaToolOptions.contains("/jprototerm/app")) {
+            return;
+        }
+
+        String sanitized = javaToolOptions
+                .replaceAll("(^|\\s)-XX:\\+AutoCreateSharedArchive(?=\\s|$)", " ")
+                .replaceAll("(^|\\s)-XX:SharedArchiveFile=\\S*/jprototerm/app\\S*(?=\\s|$)", " ")
+                .trim();
+        if (sanitized.isEmpty()) {
+            environment.remove("JAVA_TOOL_OPTIONS");
+        } else {
+            environment.put("JAVA_TOOL_OPTIONS", sanitized);
+        }
     }
 
     public void startReading(TerminalPane pane) {
@@ -157,8 +180,27 @@ public final class ShellSession implements AutoCloseable {
 
     @Override
     public void close() {
-        closed = true;
+        if (!markClosed()) {
+            return;
+        }
         reader.shutdownNow();
         pty.close();
     }
+
+    /** Signal and disconnect the pty immediately, but leave child reaping to a background thread. */
+    public void closeDetached() {
+        if (!markClosed()) {
+            return;
+        }
+        reader.shutdownNow();
+        pty.closeDetached();
+    }
+
+    private synchronized boolean markClosed() {
+        if (closed) {
+            return false;
+        }
+        closed = true;
+        return true;
+    }
 }

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

@@ -0,0 +1,51 @@
+package com.gregor.jprototerm;
+
+import java.lang.management.ManagementFactory;
+
+/**
+ * Opt-in startup phase timing, enabled with {@code -Djprototerm.timing=true} (e.g. via
+ * {@code JAVA_TOOL_OPTIONS}); otherwise every method is a cheap no-op and prints nothing.
+ *
+ * <p>Each {@link #mark(String)} prints one line to stderr with the time since the previous mark and
+ * the total since JVM start, so a cold launch breaks down into its phases — toolkit/GL init vs
+ * config load vs font loading vs first frame. The anchor is the JVM's own start time (the closest
+ * proxy we have to "process start"), so the first mark includes JVM bootstrap and JavaFX toolkit
+ * init, which is usually the dominant cost.
+ */
+final class StartupTiming {
+    private static final boolean ENABLED = Boolean.getBoolean("jprototerm.timing");
+    // Epoch millis; getStartTime() is the JVM's start, the earliest timestamp we can anchor to.
+    private static final long JVM_START_MILLIS = ManagementFactory.getRuntimeMXBean().getStartTime();
+    private static long lastMillis = -1;
+    private static boolean firstFrameSeen;
+
+    private StartupTiming() {
+    }
+
+    /**
+     * Records a phase boundary, printing the delta since the previous mark and since JVM start.
+     * Synchronized because marks come from both the launcher thread and the FX thread.
+     */
+    static synchronized void mark(String phase) {
+        if (!ENABLED) {
+            return;
+        }
+        long now = System.currentTimeMillis();
+        long sinceStart = now - JVM_START_MILLIS;
+        long sinceLast = lastMillis < 0 ? sinceStart : now - lastMillis;
+        lastMillis = now;
+        System.err.printf("[timing] %-22s +%5d ms   (%5d ms since JVM start)%n", phase, sinceLast, sinceStart);
+    }
+
+    /**
+     * Records the first rendered frame exactly once, then becomes a no-op. Safe and cheap to call
+     * from the render loop every frame (it only ever touches FX-thread state).
+     */
+    static synchronized void firstFrame() {
+        if (!ENABLED || firstFrameSeen) {
+            return;
+        }
+        firstFrameSeen = true;
+        mark("first frame");
+    }
+}

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

@@ -18,6 +18,14 @@ import java.util.stream.Stream;
  * return whether they actually changed anything so it can bump its layout version.
  */
 final class Tab implements AutoCloseable {
+    // Floating-pane sizing policy: a fraction of the tab's size with a floor so panes stay
+    // usable in small windows, cascaded diagonally per pane, kept off the window edge.
+    private static final double FLOATING_SIZE_FRACTION = 0.58;
+    private static final double FLOATING_MIN_WIDTH = 420.0;
+    private static final double FLOATING_MIN_HEIGHT = 260.0;
+    private static final double FLOATING_CASCADE_OFFSET = 28.0;
+    private static final double FLOATING_EDGE_MARGIN = 12.0;
+
     private final AppConfig config;
     private final TerminalMetrics metrics;
     // Notified (on the FX thread) when one of this tab's panes' process exits on its own, so the
@@ -86,21 +94,43 @@ final class Tab implements AutoCloseable {
         }
         List<TerminalPane> ordered = new ArrayList<>(tiled.size() + floating.size());
         ordered.addAll(tiled);
+        ordered.addAll(floatingOrder());
+        return List.copyOf(ordered);
+    }
+
+    // Floating panes bottom-to-top: insertion order, with the active pane moved to the top.
+    // Single source of the stacking order, so the clips assigned in assignClips() always match
+    // the compositing order in panes().
+    private List<TerminalPane> floatingOrder() {
+        List<TerminalPane> order = new ArrayList<>(floating.size());
         for (TerminalPane pane : floating) {
             if (pane != active) {
-                ordered.add(pane);
+                order.add(pane);
             }
         }
         if (floating.contains(active)) {
-            ordered.add(active); // active floating pane on top
+            order.add(active);
         }
-        return List.copyOf(ordered);
+        return order;
     }
 
     boolean isActive(TerminalPane pane) {
         return pane != null && pane == active;
     }
 
+    /** Every pane this tab owns, composited or not (tiled then floating). */
+    List<TerminalPane> allPanes() {
+        List<TerminalPane> all = new ArrayList<>(tiled.size() + floating.size());
+        all.addAll(tiled);
+        all.addAll(floating);
+        return all;
+    }
+
+    /** Whether this tab owns panes that {@link #panes()} does not currently composite. */
+    boolean hasHiddenPanes() {
+        return !floatingVisible && !floating.isEmpty();
+    }
+
     boolean focus(TerminalPane pane) {
         if (pane == active || !isFocusable(pane)) {
             return false;
@@ -120,13 +150,15 @@ final class Tab implements AutoCloseable {
             tiled.get(i).bounds(i * tileWidth, topInset, tileWidth, availHeight);
         }
 
-        double floatingWidth = Math.max(420, width * 0.58);
-        double floatingHeight = Math.max(260, availHeight * 0.58);
+        double floatingWidth = Math.max(FLOATING_MIN_WIDTH, width * FLOATING_SIZE_FRACTION);
+        double floatingHeight = Math.max(FLOATING_MIN_HEIGHT, availHeight * FLOATING_SIZE_FRACTION);
         for (int i = 0; i < floating.size(); i++) {
-            double offset = i * 28.0;
+            double offset = i * FLOATING_CASCADE_OFFSET;
             floating.get(i).bounds(
-                    Math.min(width - floatingWidth - 12.0, ((width - floatingWidth) / 2.0) + offset),
-                    Math.min(height - floatingHeight - 12.0, topInset + ((availHeight - floatingHeight) / 2.0) + offset),
+                    Math.min(width - floatingWidth - FLOATING_EDGE_MARGIN,
+                            ((width - floatingWidth) / 2.0) + offset),
+                    Math.min(height - floatingHeight - FLOATING_EDGE_MARGIN,
+                            topInset + ((availHeight - floatingHeight) / 2.0) + offset),
                     floatingWidth,
                     floatingHeight);
         }
@@ -141,27 +173,18 @@ final class Tab implements AutoCloseable {
     // every pane clips to its plain bounds.
     private void assignClips() {
         if (!floatingVisible || floating.isEmpty()) {
-            tiled.forEach(pane -> pane.setClip(null));
-            floating.forEach(pane -> pane.setClip(null));
+            allPanes().forEach(pane -> pane.setClip(null));
             return;
         }
 
-        // Floating panes bottom-to-top, matching panes(): insertion order, active pane on top.
-        List<TerminalPane> order = new ArrayList<>(floating.size());
-        for (TerminalPane pane : floating) {
-            if (pane != active) {
-                order.add(pane);
-            }
-        }
-        if (floating.contains(active)) {
-            order.add(active);
-        }
-
-        // Walk top-to-bottom, accumulating the union of the panes above each one.
+        // Walk the floating stack top-to-bottom, accumulating the union of the panes above
+        // each one. The topmost pane has nothing above it and keeps an unclipped bounds.
+        List<TerminalPane> order = floatingOrder();
         Shape above = null;
         for (int i = order.size() - 1; i >= 0; i--) {
-            Rectangle rect = rectOf(order.get(i));
-            order.get(i).setClip(above == null ? null : Shape.subtract(rect, above));
+            TerminalPane pane = order.get(i);
+            Rectangle rect = rectOf(pane);
+            pane.setClip(above == null ? null : Shape.subtract(rect, above));
             above = (above == null) ? rect : Shape.union(above, rect);
         }
 
@@ -214,12 +237,21 @@ final class Tab implements AutoCloseable {
         if (floatingVisible) {
             createFloatingPane();
         } else {
-            TerminalPane pane = openPane(false);
-            tiled.add(pane);
-            setActive(pane);
+            createTiledPane(paneWorkingDirectory());
         }
     }
 
+    TerminalPane createTiledPane(String workingDirectory) {
+        TerminalPane pane = openPane(false, workingDirectory);
+        tiled.add(pane);
+        setActive(pane);
+        return pane;
+    }
+
+    TerminalPane createFloatingPaneInDirectory(String workingDirectory) {
+        return addFloating(openPane(true, workingDirectory));
+    }
+
     void nextFloatingPane() {
         if (floating.isEmpty()) {
             createFloatingPane();
@@ -231,24 +263,18 @@ final class Tab implements AutoCloseable {
     }
 
     /** Promotes the active floating pane to a tiled pane, joining the tiled row. No-op otherwise. */
-    void promoteActiveFloating() {
-        TerminalPane promote = active;
-        if (!floating.remove(promote)) {
-            return; // active pane is tiled (or there is none); nothing to promote
-        }
-        if (promote == lastFocusedFloating) {
+    void toggleActiveFloating() {
+        TerminalPane toggled = active;
+        if (floating.remove(toggled)) {
             lastFocusedFloating = floating.isEmpty() ? null : floating.get(floating.size() - 1);
-        }
-        tiled.add(promote);
-        if (floating.isEmpty()) {
+            tiled.add(toggled);
             floatingVisible = false;
-        }
-        setActive(promote);
-    }
-
-    void closeActivePane() {
-        if (active != null) {
-            closePane(active);
+            setActive(toggled);
+        } else if (tiled.remove(toggled)) {
+            lastFocusedTiled = tiled.isEmpty() ? null : tiled.get(tiled.size() -1);
+            floating.add(toggled);
+            floatingVisible = true;
+            setActive(toggled);
         }
     }
 
@@ -316,8 +342,8 @@ final class Tab implements AutoCloseable {
         }
     }
 
-    TerminalPane createFloatingPane() {
-        return addFloating(openPane(true));
+    private void createFloatingPane() {
+        addFloating(openPane(true, paneWorkingDirectory()));
     }
 
     /**
@@ -369,15 +395,21 @@ final class Tab implements AutoCloseable {
     }
 
     private TerminalPane openPane(boolean asFloating) {
+        return openPane(asFloating, paneWorkingDirectory());
+    }
+
+    private TerminalPane openPane(boolean asFloating, String workingDirectory) {
         double[] size = paneSize(asFloating);
         return register(TerminalPane.create(
-                config, metrics, this::markContentChanged, size[0], size[1], paneWorkingDirectory()));
+                config, metrics, this::markContentChanged, size[0], size[1], workingDirectory));
     }
 
     private double[] paneSize(boolean asFloating) {
         double availHeight = lastHeight - lastTopInset;
         if (asFloating) {
-            return new double[] {Math.max(420, lastWidth * 0.58), Math.max(260, availHeight * 0.58)};
+            return new double[] {
+                    Math.max(FLOATING_MIN_WIDTH, lastWidth * FLOATING_SIZE_FRACTION),
+                    Math.max(FLOATING_MIN_HEIGHT, availHeight * FLOATING_SIZE_FRACTION)};
         }
         // A new tiled pane joins the row, so each gets 1/(n+1) of the width.
         return new double[] {lastWidth / (tiled.size() + 1), availHeight};
@@ -423,4 +455,14 @@ final class Tab implements AutoCloseable {
         tiled.clear();
         floating.clear();
     }
+
+    /**
+     * Signals and reaps every pane's shell process without tearing down render state. Safe to call
+     * off the FX thread (see {@link TerminalPane#terminateSession()}); iterates snapshots so a
+     * concurrent close on the FX thread can't trigger a {@link java.util.ConcurrentModificationException}.
+     */
+    public void terminateSessions() {
+        List.copyOf(tiled).forEach(TerminalPane::terminateSession);
+        List.copyOf(floating).forEach(TerminalPane::terminateSession);
+    }
 }

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

@@ -23,6 +23,9 @@ public final class TerminalMetrics {
     private double cellWidth;
     private double lineHeight;
     private double baselineOffset;
+    // One rasterized-glyph atlas per window, shared by every pane's renderer (the masks are a pure
+    // function of the font geometry below). It self-invalidates when these metrics change.
+    private final GlyphCache glyphCache = new GlyphCache(this);
 
     public TerminalMetrics(String fontFamily, double fontSize) {
         setFont(fontFamily, fontSize);
@@ -59,6 +62,11 @@ public final class TerminalMetrics {
         return baselineOffset;
     }
 
+    /** The window's shared glyph atlas (see {@link GlyphCache}). */
+    public GlyphCache glyphCache() {
+        return glyphCache;
+    }
+
     /** Columns that fit in a pane of the given pixel width (after subtracting the padding). */
     public int columnsFor(double widthPx) {
         return Math.max(1, (int) ((widthPx - 2 * PADDING) / cellWidth));

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

@@ -16,8 +16,11 @@ import javafx.application.Platform;
 import javafx.scene.canvas.GraphicsContext;
 import javafx.scene.shape.Shape;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Optional;
 import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.Supplier;
 
 /**
  * One terminal: owns its ghostty {@link Terminal}, the {@link ShellSession}/pty driving it,
@@ -39,10 +42,10 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
     // tracking meaningful: update() accumulates dirty since the last resetDirty().
     private final RenderState renderState = new RenderState();
     private RenderStateSnapshot cachedSnapshot;
-    private ShellSession session;
+    private volatile ShellSession session;
     // Run once (on the FX thread) when this pane's process exits on its own, so the owning tab can
-    // remove it. Set by the Tab that creates the pane; null until then.
-    private Runnable onExit;
+    // remove it and command panes can run follow-up actions.
+    private final List<Runnable> onExitHandlers = new ArrayList<>();
     private boolean exited;
     // Clip region for rendering (rect minus the panes covering this one), set at layout time;
     // null means clip to the plain bounds. See RenderTarget#clip().
@@ -80,8 +83,8 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
     public static TerminalPane create(AppConfig config, TerminalMetrics metrics, Runnable onContentChange,
             double widthPx, double heightPx, String workingDirectory) {
         TerminalPane pane = newPane(config, metrics, onContentChange, widthPx, heightPx);
-        pane.attach(ShellSession.start(config.shell(), config.envOverride(), pane, pane.columns, pane.rows,
-                workingDirectory));
+        attachOrShowError(pane, () -> ShellSession.start(config.shell(), config.envOverride(), pane,
+                pane.columns, pane.rows, workingDirectory, config.closeSignalNumber()));
         return pane;
     }
 
@@ -93,11 +96,23 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
     public static TerminalPane createWithCommand(AppConfig config, TerminalMetrics metrics, Runnable onContentChange,
             double widthPx, double heightPx, String workingDirectory, String command) {
         TerminalPane pane = newPane(config, metrics, onContentChange, widthPx, heightPx);
-        pane.attach(ShellSession.startCommand(config.envOverride(), pane, pane.columns, pane.rows,
-                workingDirectory, command));
+        attachOrShowError(pane, () -> ShellSession.startCommand(config.envOverride(), pane,
+                pane.columns, pane.rows, workingDirectory, command, config.closeSignalNumber()));
         return pane;
     }
 
+    // Start the pane's process, but never let a spawn failure (e.g. a bad `shell` in config)
+    // propagate and crash window/pane creation. ShellSession has already written the error into
+    // the pane, so the pane opens showing it; with no session attached it is inert (sends are
+    // dropped) and the user closes it with the close-pane key.
+    private static void attachOrShowError(TerminalPane pane, Supplier<ShellSession> start) {
+        try {
+            pane.attach(start.get());
+        } catch (RuntimeException ex) {
+            System.err.println("jprototerm: " + ex.getMessage());
+        }
+    }
+
     private static TerminalPane newPane(AppConfig config, TerminalMetrics metrics, Runnable onContentChange,
             double widthPx, double heightPx) {
         int columns = widthPx > 0 ? metrics.columnsFor(widthPx) : config.columns();
@@ -112,12 +127,20 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
 
     /** Sets the callback run when this pane's process exits on its own (see {@link #handleSessionExit}). */
     public void setOnExit(Runnable onExit) {
-        this.onExit = onExit;
+        onExitHandlers.clear();
+        addOnExit(onExit);
+    }
+
+    /** Adds a callback run when this pane's process exits on its own (see {@link #handleSessionExit}). */
+    public void addOnExit(Runnable onExit) {
+        if (onExit != null) {
+            onExitHandlers.add(onExit);
+        }
     }
 
     /**
      * Called from the shell reader thread when the pty stream ends without us closing it (the
-     * process exited). Hops to the FX thread and fires {@link #onExit} once, so tab/compositor
+     * process exited). Hops to the FX thread and fires the exit handlers once, so tab/compositor
      * mutation happens on the thread that owns the layout.
      */
     void handleSessionExit() {
@@ -126,8 +149,8 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
                 return;
             }
             exited = true;
-            if (onExit != null) {
-                onExit.run();
+            for (Runnable handler : List.copyOf(onExitHandlers)) {
+                handler.run();
             }
         });
     }
@@ -350,6 +373,16 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
         onContentChange.run();
     }
 
+    /**
+     * Drop this pane's large, rebuildable render buffers because it is no longer being composited
+     * (e.g. it sits in a background tab or a hidden floating group). The pixel backbuffer and its GPU
+     * image are freed; the shell, ghostty terminal and shared glyph atlas are untouched, and the next
+     * {@link #paintFull} rebuilds the buffer. Safe to call repeatedly. See {@link TerminalRenderer#release}.
+     */
+    public void releaseRenderResources() {
+        renderer.release();
+    }
+
     /** Paint the whole pane; see {@link TerminalRenderer#paintFull}. */
     public long paintFull(GraphicsContext gc, boolean active) {
         renderer.paintFull(gc, this, active);
@@ -373,11 +406,24 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
     @Override
     public void close() {
         if (session != null) {
-            session.close();
+            session.closeDetached();
             session = null;
         }
         mouseEncoder.close();
         renderState.close();
         terminal.close();
     }
+
+    /**
+     * Signals and reaps just the shell process, leaving the render/native state untouched. Unlike
+     * {@link #close()} this is safe to call off the FX thread — notably from a JVM shutdown hook,
+     * which runs concurrently with the live render loop — because it only touches the pty (a child
+     * process and fd), not ghostty's terminal handles. Idempotent; the OS reclaims the rest on exit.
+     */
+    public void terminateSession() {
+        ShellSession current = session;
+        if (current != null) {
+            current.close();
+        }
+    }
 }

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

@@ -33,10 +33,12 @@ abstract class TerminalRenderer {
         return java.util.List.of();
     }
 
-    protected static void clipRect(GraphicsContext gc, double x, double y, double width, double height) {
-        gc.beginPath();
-        gc.rect(x, y, width, height);
-        gc.clip();
+    /**
+     * Release any large, rebuildable render buffers (e.g. a pane's pixel backbuffer) because the
+     * target is no longer being composited. A no-op by default; the next paint must rebuild whatever
+     * was dropped. Called off the paint path, so it must not assume a frame is in progress.
+     */
+    void release() {
     }
 
     /**
@@ -45,22 +47,22 @@ abstract class TerminalRenderer {
      * path, so it replays onto the canvas as move/line/close segments.
      */
     protected static void clip(GraphicsContext gc, double x, double y, double width, double height, Shape region) {
-        if (region == null) {
-            clipRect(gc, x, y, width, height);
-            return;
-        }
-        var elements = ((Path) region).getElements();
         gc.beginPath();
-        if (elements.isEmpty()) {
-            gc.rect(x, y, 0.0, 0.0); // fully covered: clip to nothing
-        }
-        for (PathElement element : elements) {
-            if (element instanceof MoveTo moveTo) {
-                gc.moveTo(moveTo.getX(), moveTo.getY());
-            } else if (element instanceof LineTo lineTo) {
-                gc.lineTo(lineTo.getX(), lineTo.getY());
-            } else if (element instanceof ClosePath) {
-                gc.closePath();
+        if (region == null) {
+            gc.rect(x, y, width, height);
+        } else {
+            var elements = ((Path) region).getElements();
+            if (elements.isEmpty()) {
+                gc.rect(x, y, 0.0, 0.0); // fully covered: clip to nothing
+            }
+            for (PathElement element : elements) {
+                if (element instanceof MoveTo moveTo) {
+                    gc.moveTo(moveTo.getX(), moveTo.getY());
+                } else if (element instanceof LineTo lineTo) {
+                    gc.lineTo(lineTo.getX(), lineTo.getY());
+                } else if (element instanceof ClosePath) {
+                    gc.closePath();
+                }
             }
         }
         gc.clip();

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

@@ -0,0 +1,447 @@
+package com.gregor.jprototerm;
+
+import javafx.animation.AnimationTimer;
+import javafx.geometry.Rectangle2D;
+import javafx.scene.Scene;
+import javafx.scene.control.ButtonType;
+import javafx.scene.control.ComboBox;
+import javafx.scene.control.Dialog;
+import javafx.scene.control.Label;
+import javafx.scene.control.Spinner;
+import javafx.scene.control.SpinnerValueFactory;
+import javafx.scene.input.Clipboard;
+import javafx.scene.input.KeyEvent;
+import javafx.scene.layout.GridPane;
+import javafx.scene.layout.StackPane;
+import javafx.scene.text.Font;
+import javafx.stage.Screen;
+import javafx.stage.Stage;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+
+/**
+ * One top-level terminal window: its own {@link Stage}, {@link Compositor}, config/metrics, render
+ * loop and input handling. Many of these live in a single JVM under a {@link WindowManager}; closing
+ * one tears down only that window (its shells, its Stage) and leaves the rest — and, in daemon mode,
+ * the JVM — running. Built on the FX thread.
+ */
+final class TerminalWindow {
+    private final WindowManager manager;
+    private final TerminalMetrics metrics;
+    private final Compositor compositor;
+    private final Stage stage;
+    private final AnimationTimer renderLoop;
+    // Key-bound actions by their config keybinding name, checked in this order on each key press
+    // (the keys must match AppConfig's keybinding keys).
+    private final Map<String, Runnable> keyActions = new LinkedHashMap<>();
+    private AppConfig config;
+    private boolean closed;
+
+    TerminalWindow(WindowManager manager, String workingDirectory) {
+        this.manager = manager;
+        // Each window loads config independently, so edits (and per-window font changes) apply to
+        // newly opened windows without disturbing existing ones.
+        config = AppConfig.load();
+        StartupTiming.mark("config loaded");
+        metrics = new TerminalMetrics(config.fontFamily(), config.fontSize());
+        StartupTiming.mark("fonts loaded");
+        compositor = new Compositor(config, metrics, workingDirectory);
+        StartupTiming.mark("compositor ready");
+
+        // The last pane closing closes this window (not the JVM); see teardown().
+        compositor.setOnEmpty(this::teardown);
+
+        keyActions.put("navigate_left", () -> compositor.navigate(Direction.LEFT));
+        keyActions.put("navigate_down", () -> compositor.navigate(Direction.DOWN));
+        keyActions.put("navigate_up", () -> compositor.navigate(Direction.UP));
+        keyActions.put("navigate_right", () -> compositor.navigate(Direction.RIGHT));
+        keyActions.put("toggle_floating", compositor::toggleFloating);
+        keyActions.put("new_pane", compositor::createPane);
+        keyActions.put("next_floating", compositor::nextFloatingPane);
+        keyActions.put("promote_floating", compositor::toggleActiveFloating);
+        // Closing the last pane closes this window, via the compositor's onEmpty hook.
+        keyActions.put("close_pane", compositor::closeActivePane);
+        keyActions.put("new_tab", compositor::newTab);
+        keyActions.put("previous_tab", compositor::previousTab);
+        keyActions.put("next_tab", compositor::nextTab);
+        keyActions.put("open_font_selector", this::openFontSelector);
+        keyActions.put("open_scrollback", this::openScrollbackInEditor);
+        keyActions.put("create_worktree", this::createWorktreeInEditor);
+        keyActions.put("pane_sync_toggle", compositor::togglePaneSync);
+        keyActions.put("pane_sync_select", compositor::togglePaneSyncSelection);
+        keyActions.put("paste", this::pasteFromClipboard);
+
+        StackPane root = new StackPane(compositor.canvas(), compositor.imageOverlay());
+        compositor.canvas().widthProperty().bind(root.widthProperty());
+        compositor.canvas().heightProperty().bind(root.heightProperty());
+
+        Scene scene = new Scene(root, config.windowWidth(), config.windowHeight());
+        scene.addEventFilter(KeyEvent.KEY_PRESSED, this::handlePressed);
+        scene.addEventFilter(KeyEvent.KEY_TYPED, this::handleTyped);
+
+        renderLoop = new AnimationTimer() {
+            @Override
+            public void handle(long now) {
+                compositor.render();
+                StartupTiming.firstFrame();
+            }
+        };
+        renderLoop.start();
+
+        stage = new Stage();
+        stage.setTitle("jprototerm");
+        stage.setScene(scene);
+        // The X11 WM close button: tear this window down explicitly. With implicit exit disabled
+        // (see WindowManager) nothing else would reap the shells or drop the window otherwise.
+        stage.setOnCloseRequest(event -> teardown());
+        centreOnActiveScreen(stage, config.windowWidth(), config.windowHeight());
+        stage.show();
+        StartupTiming.mark("stage shown");
+        // Ask the window manager to raise and focus the new window so the user can type right
+        // away; the canvas requestFocus() below only routes events within the scene.
+        stage.toFront();
+        stage.requestFocus();
+        compositor.canvas().requestFocus();
+    }
+
+    /**
+     * Fully tears this window down (FX thread, idempotent): stops rendering, closes the compositor —
+     * which signals pane shells via the configured {@code close_signal} — disposes the Stage, and
+     * notifies the manager so it can drop the window (and, in standalone mode, exit the JVM). Both
+     * the WM close button and the last-pane-closed hook route through here.
+     */
+    void teardown() {
+        if (closed) {
+            return;
+        }
+        closed = true;
+        renderLoop.stop();
+        compositor.close();
+        stage.close();
+        manager.onWindowClosed(this);
+    }
+
+    /** Signals and reaps this window's shell processes without touching render state (off-FX safe). */
+    void terminateSessions() {
+        compositor.terminateSessions();
+    }
+
+    private void handlePressed(KeyEvent event) {
+        for (Map.Entry<String, Runnable> action : keyActions.entrySet()) {
+            String actionName = action.getKey();
+            if (config.keybindings().get(actionName).matches(event)) {
+                if (actionName.equals("pane_sync_select") && !compositor.isPaneSyncSelecting()) {
+                    continue;
+                }
+                if (compositor.isPaneSyncSelecting() && !allowedDuringPaneSyncSelection(actionName)) {
+                    event.consume();
+                    return;
+                }
+                action.getValue().run();
+                event.consume();
+                return;
+            }
+        }
+        if (compositor.isPaneSyncSelecting()) {
+            event.consume();
+            return;
+        }
+        String encoded = KeyEncoder.encode(event);
+        if (encoded != null) {
+            sendToActivePane(encoded, event);
+        }
+    }
+
+    private static boolean allowedDuringPaneSyncSelection(String action) {
+        return switch (action) {
+            case "navigate_left",
+                    "navigate_down",
+                    "navigate_up",
+                    "navigate_right",
+                    "toggle_floating",
+                    "next_floating",
+                    "previous_tab",
+                    "next_tab",
+                    "pane_sync_toggle",
+                    "pane_sync_select" -> true;
+            default -> false;
+        };
+    }
+
+    private void handleTyped(KeyEvent event) {
+        if (compositor.isPaneSyncSelecting()) {
+            event.consume();
+            return;
+        }
+        if (event.isAltDown() || event.isControlDown() || event.isMetaDown()) {
+            return;
+        }
+
+        String text = event.getCharacter();
+        if (text != null && !text.isEmpty() && text.charAt(0) >= 0x20 && text.charAt(0) != 0x7f) {
+            sendToActivePane(text, event);
+        }
+    }
+
+    // Key handlers run on every keystroke, including any that race the window's teardown, so
+    // tolerate the no-pane-left state instead of assuming one exists.
+    private void sendToActivePane(String text, KeyEvent event) {
+        TerminalPane active = compositor.activePane();
+        if (active != null) {
+            active.send(text);
+            for (TerminalPane peer : compositor.paneSyncPeers(active)) {
+                peer.send(text);
+            }
+            event.consume();
+        }
+    }
+
+    private void pasteFromClipboard() {
+        TerminalPane active = compositor.activePane();
+        Clipboard clipboard = Clipboard.getSystemClipboard();
+        if (active != null && clipboard.hasString()) {
+            String text = clipboard.getString();
+            active.paste(text);
+            for (TerminalPane peer : compositor.paneSyncPeers(active)) {
+                peer.paste(text);
+            }
+        }
+    }
+
+    private void openFontSelector() {
+        Dialog<ButtonType> dialog = new Dialog<>();
+        dialog.setTitle("Font");
+        dialog.getDialogPane().getButtonTypes().addAll(ButtonType.OK, ButtonType.CANCEL);
+
+        ComboBox<String> family = new ComboBox<>();
+        family.getItems().setAll(Font.getFamilies());
+        family.setEditable(true);
+        family.setMaxWidth(Double.MAX_VALUE);
+        family.setValue(config.fontFamily());
+
+        Spinner<Double> size = new Spinner<>();
+        size.setEditable(true);
+        size.setValueFactory(new SpinnerValueFactory.DoubleSpinnerValueFactory(6.0, 48.0, config.fontSize(), 0.5));
+
+        GridPane content = new GridPane();
+        content.setHgap(10.0);
+        content.setVgap(10.0);
+        content.add(new Label("Family"), 0, 0);
+        content.add(family, 1, 0);
+        content.add(new Label("Size"), 0, 1);
+        content.add(size, 1, 1);
+        dialog.getDialogPane().setContent(content);
+
+        dialog.showAndWait()
+                .filter(button -> button == ButtonType.OK)
+                .ifPresent(ignored -> {
+                    String selectedFamily = family.getEditor().getText();
+                    if (selectedFamily == null || selectedFamily.isBlank()) {
+                        selectedFamily = family.getValue();
+                    }
+                    if (selectedFamily == null || selectedFamily.isBlank()) {
+                        return;
+                    }
+
+                    double selectedSize = size.getValue();
+                    config = config.withFont(selectedFamily.trim(), selectedSize);
+                    config.save();
+                    compositor.setFont(config.fontFamily(), config.fontSize());
+                    compositor.canvas().requestFocus();
+                });
+    }
+
+    private void openScrollbackInEditor() {
+        // Capture the active pane's scrollback before opening the floating pane, since that
+        // makes the new pane active.
+        TerminalPane active = compositor.activePane();
+        if (active == null) {
+            return;
+        }
+        try {
+            Path file = Files.createTempFile("jprototerm-scrollback-", ".txt");
+            Files.writeString(file, active.scrollbackText());
+
+            // Run the editor as the floating pane's process (via /bin/sh -c) rather than typing the
+            // command into an interactive shell. The command runs deterministically from the start
+            // — no shell startup/rc race — and the pane auto-closes when the editor exits. The
+            // trailing rm removes the file (which holds terminal contents) when the editor exits;
+            // deleteOnExit would leak files for the JVM's whole lifetime in daemon mode.
+            compositor.openFloatingPane(editorCommand(file) + "; rm -f " + shellQuote(file.toString()));
+        } catch (IOException ex) {
+            System.err.println("Could not open scrollback in editor: " + ex.getMessage());
+        }
+    }
+
+    private void createWorktreeInEditor() {
+        // The floating pane command inherits the active pane's cwd at creation time, so the git
+        // worktree command runs from the pane that was focused before this shortcut opened.
+        TerminalPane active = compositor.activePane();
+        if (active == null) {
+            return;
+        }
+        try {
+            Path file = Files.createTempFile("jprototerm-worktree-", ".txt");
+            Path createdFile = Files.createTempFile("jprototerm-worktree-created-", ".txt");
+            Files.writeString(file, "");
+
+            TerminalPane commandPane = compositor.openFloatingPane(worktreeEditorCommand(file, createdFile));
+            if (commandPane != null) {
+                commandPane.addOnExit(() -> runPostWorktreeAction(active, createdFile));
+            } else {
+                Files.deleteIfExists(createdFile);
+            }
+        } catch (IOException ex) {
+            System.err.println("Could not create worktree from editor input: " + ex.getMessage());
+        }
+    }
+
+    private String editorCommand(Path file) {
+        String quotedFile = shellQuote(file.toString());
+        String command = config.scrollbackEditorCommand();
+        if (command == null || command.isBlank()) {
+            command = "vi {file}";
+        }
+        if (command.contains("{file}")) {
+            return command.replace("{file}", quotedFile);
+        }
+        return command + " " + quotedFile;
+    }
+
+    private String worktreeEditorCommand(Path file, Path createdFile) {
+        String quotedFile = shellQuote(file.toString());
+        String quotedCreatedFile = shellQuote(createdFile.toString());
+        String relativePath = config.worktreeRelativePath();
+        if (relativePath == null || relativePath.isBlank()) {
+            relativePath = "./.worktrees";
+        }
+        String splitRegex = config.worktreeSplitRegex();
+        if (splitRegex == null || splitRegex.isBlank()) {
+            splitRegex = ",";
+        }
+
+        return editorCommand(file)
+                + "; editor_status=$?"
+                + "; git_status=$editor_status"
+                + "; if [ \"$editor_status\" -eq 0 ]; then"
+                + " if names_file=$(mktemp); then"
+                + " if awk -v re=" + shellQuote(splitRegex)
+                + " '{ text = text $0 \"\\n\" }"
+                + " END { n = split(text, names, re); for (i = 1; i <= n; i++)"
+                + " { name = names[i]; sub(/^[[:space:]]+/, \"\", name);"
+                + " sub(/[[:space:]]+$/, \"\", name); if (name != \"\") print name; } }'"
+                + " " + quotedFile + " > \"$names_file\"; then"
+                + " git_status=0"
+                + "; while IFS= read -r name; do"
+                + " worktree_path=" + shellQuote(relativePath) + "/\"$name\""
+                + "; git worktree add \"$worktree_path\""
+                + " || { git_status=$?; break; }"
+                + "; created_path=$(cd \"$worktree_path\" && pwd -P)"
+                + " || { git_status=$?; break; }"
+                + "; printf '%s\\n' \"$created_path\" >> " + quotedCreatedFile
+                + " || { git_status=$?; break; }"
+                + "; done < \"$names_file\""
+                + "; else git_status=$?"
+                + "; fi"
+                + "; rm -f \"$names_file\""
+                + "; else git_status=$?"
+                + "; fi"
+                + "; fi"
+                + "; rm -f " + quotedFile
+                + "; exit \"$git_status\"";
+    }
+
+    private void runPostWorktreeAction(TerminalPane lastActivePane, Path createdFile) {
+        List<String> worktreePaths = readCreatedWorktreePaths(createdFile);
+        try {
+            Files.deleteIfExists(createdFile);
+        } catch (IOException ex) {
+            System.err.println("Could not remove worktree result file " + createdFile + ": " + ex.getMessage());
+        }
+        if (worktreePaths.isEmpty()) {
+            return;
+        }
+
+        String action = config.worktreePostCreateAction();
+        if (action == null || action.isBlank()) {
+            return;
+        }
+
+        switch (action.trim().toLowerCase(Locale.ROOT)) {
+            case "none" -> { }
+            case "cd" -> lastActivePane.send("cd " + shellQuote(worktreePaths.get(worktreePaths.size() - 1)) + "\r");
+            case "create_panes" -> createWorktreePanes(worktreePaths, false);
+            case "create_panes_floating" -> createWorktreePanes(worktreePaths, true);
+            default -> System.err.println("Unknown worktree.post_create_action '" + action + "'");
+        }
+    }
+
+    private void createWorktreePanes(List<String> worktreePaths, boolean floating) {
+        List<String> commands = config.worktreeCommands();
+        List<TerminalPane> createdPanes = new ArrayList<>();
+        for (int i = 0; i < worktreePaths.size(); i++) {
+            TerminalPane pane = floating
+                    ? compositor.createFloatingPaneInDirectory(worktreePaths.get(i))
+                    : compositor.createTiledPane(worktreePaths.get(i));
+            if (pane != null) {
+                createdPanes.add(pane);
+            }
+            if (pane != null && !commands.isEmpty()) {
+                String command = commands.get(i % commands.size());
+                if (command != null && !command.isBlank()) {
+                    pane.send(command + "\r");
+                }
+            }
+        }
+        if (config.worktreeSyncPanes() && !createdPanes.isEmpty()) {
+            compositor.syncPanes(createdPanes);
+        }
+    }
+
+    private List<String> readCreatedWorktreePaths(Path createdFile) {
+        try {
+            List<String> paths = new ArrayList<>();
+            for (String line : Files.readAllLines(createdFile)) {
+                String path = line.trim();
+                if (!path.isEmpty()) {
+                    paths.add(path);
+                }
+            }
+            return paths;
+        } catch (IOException ex) {
+            System.err.println("Could not read created worktree paths from " + createdFile + ": " + ex.getMessage());
+            return List.of();
+        }
+    }
+
+    private static String shellQuote(String value) {
+        return "'" + value.replace("'", "'\"'\"'") + "'";
+    }
+
+    // Centre the stage within the screen the mouse pointer is on (the best proxy for the
+    // "active" monitor on X11, which exposes no focused-monitor concept to JavaFX).
+    private static void centreOnActiveScreen(Stage stage, double width, double height) {
+        Rectangle2D bounds = activeScreen().getVisualBounds();
+        stage.setX(bounds.getMinX() + ((bounds.getWidth() - width) / 2.0));
+        stage.setY(bounds.getMinY() + ((bounds.getHeight() - height) / 2.0));
+    }
+
+    private static Screen activeScreen() {
+        int[] at = X11Pointer.query();
+        if (at != null) {
+            // libX11 and JavaFX share a coordinate space on the X11 virtual screen.
+            List<Screen> screens = Screen.getScreensForRectangle(at[0], at[1], 1.0, 1.0);
+            if (!screens.isEmpty()) {
+                return screens.get(0);
+            }
+        }
+        return Screen.getPrimary();
+    }
+}

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

@@ -0,0 +1,69 @@
+package com.gregor.jprototerm;
+
+import javafx.application.Platform;
+
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+/**
+ * Owns the JavaFX toolkit lifecycle and the set of live {@link TerminalWindow}s for one JVM. A
+ * single JVM hosts every window, so the expensive toolkit/GL init is paid once; opening another
+ * window is then just a new {@link javafx.stage.Stage}.
+ *
+ * <p>Two modes differ only in the empty policy: in {@link Mode#STANDALONE} (today's behavior, used
+ * as the fallback when no daemon is reachable) the JVM exits once the last window closes; in
+ * {@link Mode#DAEMON} the toolkit stays alive with zero windows, waiting for the next client
+ * request. {@link Platform#setImplicitExit(boolean) implicit exit} is disabled in both so the
+ * toolkit never tears itself down behind our back — every exit is an explicit decision here.
+ */
+public final class WindowManager {
+    public enum Mode {
+        STANDALONE,
+        DAEMON
+    }
+
+    private final Mode mode;
+    // Mutated on the FX thread (register/deregister), iterated from the shutdown-hook thread.
+    private final Set<TerminalWindow> windows = new CopyOnWriteArraySet<>();
+
+    private WindowManager(Mode mode) {
+        this.mode = mode;
+    }
+
+    /**
+     * Brings up the JavaFX toolkit (once per JVM) and returns a manager in {@code mode}. Registers a
+     * shutdown hook that reaps every window's shell processes, so child shells are terminated rather
+     * than orphaned if the JVM is killed (SIGTERM/SIGINT/SIGHUP) — see
+     * {@link Compositor#terminateSessions()}.
+     */
+    public static WindowManager start(Mode mode) {
+        WindowManager manager = new WindowManager(mode);
+        Platform.setImplicitExit(false);
+        Platform.startup(() -> StartupTiming.mark("toolkit ready"));
+        Runtime.getRuntime().addShutdownHook(new Thread(manager::terminateAllSessions, "shell-cleanup"));
+        return manager;
+    }
+
+    /** Opens a new window (on the FX thread) whose first pane starts in {@code workingDirectory}. */
+    public void openWindow(String workingDirectory) {
+        Platform.runLater(() -> windows.add(new TerminalWindow(this, workingDirectory)));
+    }
+
+    /**
+     * Called by a window when it has finished tearing down (FX thread). Drops it from the registry
+     * and, in standalone mode, exits the JVM once none remain.
+     */
+    void onWindowClosed(TerminalWindow window) {
+        windows.remove(window);
+        if (mode == Mode.STANDALONE && windows.isEmpty()) {
+            Platform.exit();
+        }
+    }
+
+    /** Signals and reaps every live window's shell processes. Safe to call off the FX thread. */
+    void terminateAllSessions() {
+        for (TerminalWindow window : windows) {
+            window.terminateSessions();
+        }
+    }
+}