thinner borders

KeyEncoder mapped TAB to a plain tab regardless of Shift, so Shift+Tab sent the
same byte as Tab. Apps that use backtab for reverse navigation (fish completion
menu, helix theme picker) never saw it. Emit CSI Z when Shift is held.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
(cherry picked from commit 93d53fcef6)

.classpath

@@ -1,18 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<classpath>
-	<classpathentry kind="src" output="bin/main" path="src/main/java">
-		<attributes>
-			<attribute name="gradle_scope" value="main"/>
-			<attribute name="gradle_used_by_scope" value="main,test"/>
-		</attributes>
-	</classpathentry>
-	<classpathentry kind="src" output="bin/main" path="src/main/resources">
-		<attributes>
-			<attribute name="gradle_scope" value="main"/>
-			<attribute name="gradle_used_by_scope" value="main,test"/>
-		</attributes>
-	</classpathentry>
-	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-21/"/>
-	<classpathentry kind="con" path="org.eclipse.buildship.core.gradleclasspathcontainer"/>
-	<classpathentry kind="output" path="bin/default"/>
-</classpath>

.codexsession

@@ -1 +0,0 @@
-019e6999-b7c8-7591-a8aa-ea51b89a7f7e

.gitattributes

@@ -0,0 +1 @@
+*.mp4 filter=lfs diff=lfs merge=lfs -text

.gitignore

@@ -11,7 +11,10 @@ devenv.local.yaml
 # pre-commit
 .pre-commit-config.yaml
 build
-build
 .gradle
 bin
+.settings
+.project
 .worktrees
+.classpath
+.codexsession

.ignore

@@ -1,3 +1,4 @@
 .gradle
-result
 bin
+result
+.worktrees

.project

@@ -1,34 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<projectDescription>
-	<name>jprototerm</name>
-	<comment>Project jprototerm created by Buildship.</comment>
-	<projects>
-	</projects>
-	<buildSpec>
-		<buildCommand>
-			<name>org.eclipse.jdt.core.javabuilder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-		<buildCommand>
-			<name>org.eclipse.buildship.core.gradleprojectbuilder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-	</buildSpec>
-	<natures>
-		<nature>org.eclipse.jdt.core.javanature</nature>
-		<nature>org.eclipse.buildship.core.gradleprojectnature</nature>
-	</natures>
-	<filteredResources>
-		<filter>
-			<id>1779917652126</id>
-			<name></name>
-			<type>30</type>
-			<matcher>
-				<id>org.eclipse.core.resources.regexFilterMatcher</id>
-				<arguments>node_modules|\.git|__CREATED_BY_JAVA_LANGUAGE_SERVER__</arguments>
-			</matcher>
-		</filter>
-	</filteredResources>
-</projectDescription>

.settings/org.eclipse.buildship.core.prefs

@@ -1,13 +0,0 @@
-arguments=--init-script /home/anon/Src/eclipse.jdt.ls/org.eclipse.jdt.ls.product/target/repository/configuration/org.eclipse.osgi/58/0/.cp/gradle/init/init.gradle
-auto.sync=false
-build.scans.enabled=false
-connection.gradle.distribution=GRADLE_DISTRIBUTION(LOCAL_INSTALLATION(/home/anon/.sdkman/candidates/gradle/current))
-connection.project.dir=
-eclipse.preferences.version=1
-gradle.user.home=
-java.home=/nix/store/c3pl7bqrx3d2rc3dh98z6yaj0mv1p52g-openjdk-21.0.10+7/lib/openjdk
-jvm.arguments=
-offline.mode=false
-override.workspace.settings=true
-show.console.view=true
-show.executions.view=true

README.md

@@ -12,6 +12,8 @@ floating panes and tabs.
 > setups, or Mesa/AMD/Intel GPUs. I'm happy to accept pull requests that broaden host
 > support.
 
+<video src="https://gitea.gregorlohaus.com/gregor/jprototerm/media/branch/main/demo.mp4" controls></video>
+
 ## Build
 
 ```sh
@@ -60,6 +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:
@@ -96,6 +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 = ""
 
@@ -106,12 +167,17 @@ navigate_up = "ALT+K"
 navigate_right = "ALT+L"
 toggle_floating = "ALT+F"
 new_pane = "ALT+N"
+next_floating = "ALT+F12"
 close_pane = "ALT+X"
 new_tab = "ALT+A"
 previous_tab = "ALT+SHIFT+H"
 next_tab = "ALT+SHIFT+L"
 open_font_selector = "ALT+T"
 open_scrollback = "ALT+S"
+create_worktree = "ALT+W"
+pane_sync_toggle = "ALT+Y"
+pane_sync_select = "SPACE"
+paste = "CTRL+SHIFT+V"
 ```
 
 ## Defaults
@@ -120,12 +186,25 @@ open_scrollback = "ALT+S"
 - `Alt+n`: new pane — a floating pane when floating panes are shown, otherwise a new tiled
   pane (tiled panes are split equally across the width)
 - `Alt+f`: show or hide all floating panes
+- `Alt+F12`: cycle floating panes
 - `Alt+x`: close the active pane; closing a tab's last pane closes the tab, and closing the
   last pane of the last tab quits
 - `Alt+a`: new tab
 - `Alt+Shift+h` / `Alt+Shift+l`: previous / next tab
 - `Alt+t`: open the font selector
 - `Alt+s`: open the active pane scrollback in `$EDITOR`
+- `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 = ""
 
@@ -26,6 +37,15 @@ navigate_up = "ALT+K"
 navigate_right = "ALT+L"
 toggle_floating = "ALT+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"

devenv.lock

@@ -1,65 +0,0 @@
-{
-  "nodes": {
-    "devenv": {
-      "locked": {
-        "dir": "src/modules",
-        "lastModified": 1779749056,
-        "narHash": "sha256-AtocdrunzuxTvSDn+82RntEhrs6TicM6Z4/zNQS9KKg=",
-        "owner": "cachix",
-        "repo": "devenv",
-        "rev": "099ac65fcef79e88127bdc06adbd1ea94255274a",
-        "type": "github"
-      },
-      "original": {
-        "dir": "src/modules",
-        "owner": "cachix",
-        "repo": "devenv",
-        "type": "github"
-      }
-    },
-    "nixpkgs": {
-      "inputs": {
-        "nixpkgs-src": "nixpkgs-src"
-      },
-      "locked": {
-        "lastModified": 1778507786,
-        "narHash": "sha256-HzSQCKMsMr8r55LwM1JuzIOB+8bzk0FEv6sItKvsfoY=",
-        "owner": "cachix",
-        "repo": "devenv-nixpkgs",
-        "rev": "8f24a228a782e24576b155d1e39f0d914b380691",
-        "type": "github"
-      },
-      "original": {
-        "owner": "cachix",
-        "ref": "rolling",
-        "repo": "devenv-nixpkgs",
-        "type": "github"
-      }
-    },
-    "nixpkgs-src": {
-      "flake": false,
-      "locked": {
-        "lastModified": 1778274207,
-        "narHash": "sha256-I4puXmX1iovcCHZlRmztO3vW0mAbbRvq4F8wgIMQ1MM=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "b3da656039dc7a6240f27b2ef8cc6a3ef3bccae7",
-        "type": "github"
-      },
-      "original": {
-        "owner": "NixOS",
-        "ref": "nixpkgs-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
-    "root": {
-      "inputs": {
-        "devenv": "devenv",
-        "nixpkgs": "nixpkgs"
-      }
-    }
-  },
-  "root": "root",
-  "version": 7
-}

devenv.nix

@@ -1,66 +0,0 @@
-{ pkgs, lib, config, inputs, ... }:
-
-let
-  system = pkgs.stdenv.hostPlatform.system;
-
-  jlibghostty = builtins.getFlake
-    "git+https://gitea.gregorlohaus.com/gregor/jlibghostty.git";
-
-  jlib = jlibghostty.packages.${system}.jlibghostty;
-  hostNvidiaLibs = ".devenv/host-nvidia-libs";
-in
-{
-  packages = [
-    pkgs.git
-    pkgs.gradle_9
-    pkgs.jdk25
-    pkgs.jdt-language-server
-    pkgs.openjfx
-
-    pkgs.glib
-    pkgs.xorg.libXxf86vm
-    pkgs.xorg.libXrender
-    pkgs.xorg.libXtst
-    pkgs.xorg.libXi
-    pkgs.xorg.libXrandr
-
-    pkgs.libGL
-    pkgs.gtk3
-    pkgs.alsa-lib
-    pkgs.mesa-demos
-  ];
-
-  env.LD_LIBRARY_PATH = "${hostNvidiaLibs}:" + lib.makeLibraryPath [
-    pkgs.openjfx
-
-    pkgs.glib
-    pkgs.xorg.libXxf86vm
-    pkgs.xorg.libXrender
-    pkgs.xorg.libXtst
-    pkgs.xorg.libXi
-    pkgs.xorg.libXrandr
-
-    pkgs.libGL
-    pkgs.gtk3
-    pkgs.alsa-lib
-  ] + ":/usr/lib/x86_64-linux-gnu/nvidia/current";
-  env.__GLX_VENDOR_LIBRARY_NAME = "nvidia";
-  env.__EGL_VENDOR_LIBRARY_FILENAMES = "/usr/share/glvnd/egl_vendor.d/10_nvidia.json";
-  env.JLIBGHOSTTY_MAVEN_REPO = "${jlib}/maven";
-
-  enterShell = ''
-    mkdir -p ${hostNvidiaLibs}
-    for lib in \
-      /usr/lib/x86_64-linux-gnu/libnvidia*.so* \
-      /usr/lib/x86_64-linux-gnu/libGLX_nvidia.so* \
-      /usr/lib/x86_64-linux-gnu/libEGL_nvidia.so* \
-      /usr/lib/x86_64-linux-gnu/nvidia/current/libnvidia*.so* \
-      /usr/lib/x86_64-linux-gnu/nvidia/current/libGLX_nvidia.so* \
-      /usr/lib/x86_64-linux-gnu/nvidia/current/libEGL_nvidia.so*
-    do
-      if [ -e "$lib" ]; then
-        ln -sfn "$lib" ${hostNvidiaLibs}/"$(basename "$lib")"
-      fi
-    done
-  '';
-}

devenv.yaml

@@ -1,18 +0,0 @@
-# yaml-language-server: $schema=https://devenv.sh/devenv.schema.json
-inputs:
-  nixpkgs:
-    url: github:cachix/devenv-nixpkgs/rolling
-
-# If you're using non-OSS software, you can set allowUnfree to true.
-# allowUnfree: true
-
-# If you're not willing to allow unsupported packages:
-# allowUnsupportedSystem: false
-
-# If you're willing to use a package that's vulnerable
-# permittedInsecurePackages:
-#  - "openssl-1.1.1w"
-
-# If you have more than one devenv you can merge them
-#imports:
-# - ./backend

flake.lock

@@ -70,11 +70,11 @@
         "nixpkgs": "nixpkgs"
       },
       "locked": {
-        "lastModified": 1780258814,
-        "narHash": "sha256-8rxL7xaZ/loYg3zdt0w5+hfNyHFVknDZN360NzrtCsQ=",
+        "lastModified": 1780363584,
+        "narHash": "sha256-BN6kwSBnlavuySut6vvLsfwkfKBjrPvFgJeeMMTXNtg=",
         "ref": "refs/heads/main",
-        "rev": "6a3d5aa0b0b1f738c958e2a2f0249574c07d9c4d",
-        "revCount": 23,
+        "rev": "1cd908e5d0070fdc1c86fc6b300cf1d6dbb5d184",
+        "revCount": 25,
         "type": "git",
         "url": "https://gitea.gregorlohaus.com/gregor/jlibghostty.git"
       },

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

@@ -5,6 +5,7 @@ import io.github.wasabithumb.jtoml.document.TomlDocument;
 import io.github.wasabithumb.jtoml.except.TomlException;
 import io.github.wasabithumb.jtoml.key.TomlKey;
 import io.github.wasabithumb.jtoml.value.TomlValue;
+import io.github.wasabithumb.jtoml.value.array.TomlArray;
 import io.github.wasabithumb.jtoml.value.primitive.TomlPrimitive;
 import io.github.wasabithumb.jtoml.value.table.TomlTable;
 
@@ -12,6 +13,7 @@ import java.nio.file.Files;
 import java.io.IOException;
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
+import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -20,13 +22,19 @@ public record AppConfig(
         int columns,
         int rows,
         long maxScrollback,
-        String shell,
+        List<String> shell,
         String fontFamily,
         double fontSize,
         double windowWidth,
         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
 ) {
@@ -37,19 +45,25 @@ public record AppConfig(
             "navigate_right",
             "toggle_floating",
             "new_pane",
+            "next_floating",
+            "promote_floating",
             "close_pane",
             "new_tab",
             "previous_tab",
             "next_tab",
             "open_font_selector",
-            "open_scrollback"
+            "open_scrollback",
+            "create_worktree",
+            "pane_sync_toggle",
+            "pane_sync_select",
+            "paste"
     );
 
     public static AppConfig load() {
         AppConfig defaults = defaults();
         Path path = configPath();
         if (!Files.isRegularFile(path)) {
-            writeDefaultConfig(path, defaults);
+            save(path, defaults);
             return defaults;
         }
 
@@ -59,13 +73,19 @@ public record AppConfig(
                     intValue(document, "terminal.columns", defaults.columns),
                     intValue(document, "terminal.rows", defaults.rows),
                     longValue(document, "terminal.max_scrollback", defaults.maxScrollback),
-                    stringValue(document, "terminal.shell", defaults.shell),
+                    stringListValue(document, "terminal.shell", defaults.shell),
                     stringValue(document, "terminal.font_family", defaults.fontFamily),
                     doubleValue(document, "terminal.font_size", defaults.fontSize),
                     doubleValue(document, "window.width", defaults.windowWidth),
                     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)
             );
@@ -87,6 +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")),
@@ -95,12 +121,18 @@ public record AppConfig(
                         Map.entry("navigate_right", KeyBinding.parse("ALT+L")),
                         Map.entry("toggle_floating", KeyBinding.parse("ALT+F")),
                         Map.entry("new_pane", KeyBinding.parse("ALT+N")),
+                        Map.entry("next_floating", KeyBinding.parse("ALT+F12")),
+                        Map.entry("promote_floating", KeyBinding.parse("ALT+P")),
                         Map.entry("close_pane", KeyBinding.parse("ALT+X")),
                         Map.entry("new_tab", KeyBinding.parse("ALT+A")),
                         Map.entry("previous_tab", KeyBinding.parse("ALT+SHIFT+H")),
                         Map.entry("next_tab", KeyBinding.parse("ALT+SHIFT+L")),
                         Map.entry("open_font_selector", KeyBinding.parse("ALT+T")),
-                        Map.entry("open_scrollback", KeyBinding.parse("ALT+S"))
+                        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"))
                 )
         );
     }
@@ -117,11 +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);
     }
@@ -134,8 +182,10 @@ public record AppConfig(
         return Path.of(System.getProperty("user.home"), ".config", "jprototerm", "config.toml");
     }
 
-    private static String defaultShell() {
-        return "/bin/bash";
+    private static List<String> defaultShell() {
+        // The executable plus its arguments, spawned verbatim. -i makes bash interactive; a
+        // different shell can use whatever flags it needs (or none) by editing this list.
+        return List.of("/bin/bash", "-i");
     }
 
     private static String defaultScrollbackEditorCommand() {
@@ -146,6 +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) {
@@ -154,10 +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();
@@ -182,7 +245,8 @@ public record AppConfig(
         builder.append("columns = ").append(columns).append('\n');
         builder.append("rows = ").append(rows).append('\n');
         builder.append("max_scrollback = ").append(maxScrollback).append('\n');
-        builder.append("shell = ").append(quoted(shell)).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");
@@ -192,6 +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');
@@ -207,6 +277,17 @@ public record AppConfig(
         return builder.toString();
     }
 
+    private static String quotedList(List<String> values) {
+        StringBuilder builder = new StringBuilder("[");
+        for (int i = 0; i < values.size(); i++) {
+            if (i > 0) {
+                builder.append(", ");
+            }
+            builder.append(quoted(values.get(i)));
+        }
+        return builder.append("]").toString();
+    }
+
     private static String quoted(String value) {
         return "\"" + value
                 .replace("\\", "\\\\")
@@ -266,16 +347,28 @@ public record AppConfig(
         return primitive == null ? fallback : primitive.asString();
     }
 
+    /** Reads a TOML array of strings (e.g. {@code shell = ["/bin/bash", "-i"]}), or the fallback. */
+    private static List<String> stringListValue(TomlTable table, String key, List<String> fallback) {
+        TomlValue value = table.get(key);
+        if (value == null || !value.isArray()) {
+            return fallback;
+        }
+        List<String> result = new ArrayList<>();
+        for (TomlValue element : value.asArray()) {
+            if (element.isPrimitive()) {
+                try {
+                    result.add(element.asPrimitive().asString());
+                } catch (RuntimeException ignored) {
+                    // Skip non-string entries; a shell command line is a list of strings.
+                }
+            }
+        }
+        // An empty or all-invalid array would mean "no program to run"; keep the default instead.
+        return result.isEmpty() ? fallback : List.copyOf(result);
+    }
+
     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

@@ -4,79 +4,125 @@ import dev.jlibghostty.KeyModifiers;
 import dev.jlibghostty.MouseButton;
 import dev.jlibghostty.MouseEncoderSize;
 import dev.jlibghostty.MouseInput;
-import javafx.geometry.Pos;
-import javafx.scene.Parent;
-import javafx.scene.control.Label;
+import javafx.geometry.VPos;
+import javafx.scene.Node;
+import javafx.scene.canvas.Canvas;
+import javafx.scene.canvas.GraphicsContext;
 import javafx.scene.input.InputEvent;
 import javafx.scene.input.MouseEvent;
 import javafx.scene.input.ScrollEvent;
 import javafx.scene.input.ScrollEvent.VerticalTextScrollUnits;
-import javafx.scene.layout.Background;
-import javafx.scene.layout.BackgroundFill;
-import javafx.scene.layout.CornerRadii;
-import javafx.scene.layout.HBox;
-import javafx.scene.layout.Pane;
 import javafx.scene.paint.Color;
+import javafx.scene.text.Font;
+import javafx.scene.text.FontSmoothingType;
+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 exposes the terminal surface as a JavaFX scene graph. Each
- * terminal pane is mounted as its own node, so JavaFX child order handles stacking and clipping
- * between panes. The pane model still owns terminals, ptys, cell geometry, and snapshots; this
- * class handles tab/pane lifecycle, layout, focus, mouse routing, and frame scheduling.
+ * Owns the window's tabs and drives rendering and input. It composites only the current tab:
+ * each frame it lays that tab out, paints the panes bottom-to-top (so the active floating pane
+ * lands on top) and lets each pane paint its own content, clipped to the region the layout gave
+ * it. The cross-pane concerns live here — the dirty-frame bookkeeping, the tab strip, routing
+ * mouse/scroll to the pane under the pointer, and the tab/pane lifecycle that {@link Main}'s key
+ * bindings invoke.
  */
 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 TAB_INACTIVE_TEXT = Color.rgb(128, 136, 148);
-    private static final Color TAB_ACTIVE_BACKGROUND = Color.rgb(45, 55, 72);
-    private static final Color TAB_INACTIVE_BACKGROUND = Color.rgb(22, 24, 28);
+    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);
+    // Keep this narrower than the terminal renderer's active border so focus remains visible.
+    private static final double PANE_SYNC_BORDER_WIDTH = 1.0;
+    // Thin tab strip shown at the top when more than one tab is open.
     private static final double TAB_BAR_HEIGHT = 22.0;
 
-    private final Pane root = new Pane();
-    private final Pane paneLayer = new Pane();
-    private final HBox tabBar = new HBox(1.0);
+    private final Canvas canvas = new Canvas();
+    // Kitty images are drawn as retained nodes layered over the canvas, not composited onto it.
+    private final KittyImageOverlay imageOverlay = new KittyImageOverlay();
     private final AppConfig config;
     private final TerminalMetrics metrics;
     private final List<Tab> tabs = new ArrayList<>();
-    private final Map<TerminalPane, TerminalPaneNode> nodes = new HashMap<>();
     private int currentTabIndex;
-    private boolean sceneDirty = true;
+    // Bumped on any structural change (tab switch, pane add/close/focus/move) so render()
+    // knows to recomposite. Terminal *content* changes are tracked separately through each
+    // tab's content version.
+    private long layoutVersion;
+    // 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;
+    private String lastFontFamily;
+    private double lastFontSize = -1.0;
+    private long lastLayoutVersion = Long.MIN_VALUE;
     private long lastContentVersion = Long.MIN_VALUE;
     private boolean mouseButtonPressed;
     private MouseButton pressedButton = MouseButton.UNKNOWN;
+    // Run when the last pane closes (so the window can quit). No-op until Main sets it.
+    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));
-
-        root.setFocusTraversable(true);
-        root.setBackground(new Background(new BackgroundFill(GAP_BACKGROUND, CornerRadii.EMPTY, null)));
-        root.getChildren().setAll(paneLayer, tabBar);
-        root.setOnMousePressed(event -> root.requestFocus());
+        tabs.add(new Tab(config, metrics, workingDirectory, this::closePane));
+        canvas.setFocusTraversable(true);
+        canvas.setOnMousePressed(this::handleMousePressed);
+        canvas.setOnMouseReleased(this::handleMouseReleased);
+        canvas.setOnMouseDragged(this::handleMouseDragged);
+        canvas.setOnMouseMoved(this::handleMouseMoved);
+        canvas.setOnScroll(this::handleScroll);
     }
 
-    public Parent node() {
-        return root;
+    public Canvas canvas() {
+        return canvas;
     }
 
-    public void requestFocus() {
-        root.requestFocus();
+    /** Sets the callback run when the last pane closes (e.g. to quit the application). */
+    public void setOnEmpty(Runnable onEmpty) {
+        this.onEmpty = onEmpty;
+    }
+
+    /** The kitty-image overlay, to be stacked directly above {@link #canvas()} in the window. */
+    public Node imageOverlay() {
+        return imageOverlay.node();
     }
 
     public void setFont(String family, double size) {
         metrics.setFont(family, size);
-        nodes.values().forEach(TerminalPaneNode::discard);
-        markSceneDirty();
+        paneContentVersion.clear();
+        layoutVersion++; // recomposite with the new metrics on the next frame
     }
 
     // ---- Tabs and panes -------------------------------------------------------------
@@ -85,63 +131,193 @@ 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) {
         if (!isEmpty() && currentTab().navigate(direction)) {
-            markSceneDirty();
+            layoutVersion++;
         }
     }
 
+    public boolean isPaneSyncSelecting() {
+        return paneSyncSelectMode;
+    }
+
+    public void togglePaneSync() {
+        if (paneSyncSelectMode) {
+            paneSyncPanes.clear();
+            paneSyncPanes.addAll(paneSyncSelection);
+            paneSyncSelectMode = false;
+            paneSyncSelection.clear();
+            prunePaneSyncState();
+            layoutVersion++;
+            return;
+        }
+        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() {
-        if (isEmpty()) {
-            return;
-        }
-        currentTab().toggleFloating();
-        markSceneDirty();
+        mutateCurrentTab(() -> currentTab().toggleFloating());
     }
 
     public void createPane() {
+        mutateCurrentTab(() -> currentTab().createPane());
+    }
+
+    public TerminalPane createTiledPane(String workingDirectory) {
+        if (isEmpty()) {
+            return null;
+        }
+        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;
+    }
+
+    /**
+     * Opens a floating pane running {@code command} directly (auto-closing when it exits), makes it
+     * active, and returns it (null when no tab exists).
+     */
+    public TerminalPane openFloatingPane(String command) {
+        if (isEmpty()) {
+            return null;
+        }
+        TerminalPane pane = currentTab().createFloatingPane(command);
+        layoutVersion++;
+        return pane;
+    }
+
+    public void nextFloatingPane() {
+        mutateCurrentTab(() -> currentTab().nextFloatingPane());
+    }
+
+    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().createPane();
-        markSceneDirty();
+        change.run();
+        layoutVersion++;
     }
 
     public void closeActivePane() {
-        if (isEmpty()) {
-            return;
+        TerminalPane active = activePane();
+        if (active != null) {
+            closePane(active);
         }
-        currentTab().closeActivePane();
-        if (currentTab().isEmpty()) {
-            tabs.remove(currentTabIndex);
-            if (currentTabIndex >= tabs.size()) {
-                currentTabIndex = Math.max(0, tabs.size() - 1);
+    }
+
+    /**
+     * Closes a specific pane, wherever it lives. Driven both by the key-bound close (via
+     * {@link #closeActivePane()}) and by a pane whose process exited on its own. Drops the owning
+     * tab if it becomes empty, and fires {@link #setOnEmpty} when the last pane is gone. Must run on
+     * the FX thread.
+     */
+    public void closePane(TerminalPane pane) {
+        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).
+                    tabs.remove(i);
+                    if (i < currentTabIndex) {
+                        currentTabIndex--;
+                    } else if (currentTabIndex >= tabs.size()) {
+                        currentTabIndex = Math.max(0, tabs.size() - 1);
+                    }
+                }
+                layoutVersion++;
+                if (isEmpty()) {
+                    onEmpty.run();
+                }
+                return;
             }
         }
-        markSceneDirty();
     }
 
     public void newTab() {
-        tabs.add(new Tab(config, metrics));
+        // 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.
+        TerminalPane active = activePane();
+        String workingDirectory = active != null ? active.currentWorkingDirectory() : null;
+        tabs.add(new Tab(config, metrics, workingDirectory, this::closePane));
         currentTabIndex = tabs.size() - 1;
-        markSceneDirty();
+        layoutVersion++;
     }
 
     public void nextTab() {
         if (tabs.size() > 1) {
             currentTabIndex = (currentTabIndex + 1) % tabs.size();
-            markSceneDirty();
+            layoutVersion++;
         }
     }
 
     public void previousTab() {
         if (tabs.size() > 1) {
             currentTabIndex = (currentTabIndex - 1 + tabs.size()) % tabs.size();
-            markSceneDirty();
+            layoutVersion++;
         }
     }
 
@@ -150,8 +326,21 @@ public final class Compositor {
             tab.close();
         }
         tabs.clear();
-        nodes.clear();
-        paneLayer.getChildren().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() {
@@ -162,140 +351,245 @@ public final class Compositor {
         return tabs.isEmpty() ? List.of() : currentTab().panes();
     }
 
-    private List<TerminalPane> allOpenPanes() {
-        List<TerminalPane> panes = new ArrayList<>();
-        for (Tab tab : tabs) {
-            panes.addAll(tab.allPanes());
-        }
-        return panes;
-    }
-
     private boolean isActive(TerminalPane pane) {
         return !tabs.isEmpty() && currentTab().isActive(pane);
     }
 
     private void focus(TerminalPane pane) {
         if (!tabs.isEmpty() && currentTab().focus(pane)) {
-            markSceneDirty();
+            layoutVersion++;
         }
     }
 
     // ---- Rendering ------------------------------------------------------------------
 
     public void render() {
-        double width = root.getWidth();
-        double height = root.getHeight();
-        long contentVersion = tabs.isEmpty() ? 0 : currentTab().contentVersion();
-        boolean geometryChanged = width != lastWidth || height != lastHeight;
-        boolean contentChanged = contentVersion != lastContentVersion;
-        boolean syncScene = sceneDirty || geometryChanged;
+        sweepHiddenPanes();
+        switch (nextFrameType()) {
+            case IDLE -> { }
+            case LAYOUT -> renderLayoutFrame();
+            case CONTENT -> renderContentFrame();
+        }
+    }
 
-        if (!syncScene && !contentChanged) {
+    // 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
+    // changed and the frame is idle.
+    private FrameType nextFrameType() {
+        double width = canvas.getWidth();
+        double height = canvas.getHeight();
+        long contentVersion = tabs.isEmpty() ? 0 : currentTab().contentVersion();
+
+        boolean layoutChanged = width != lastWidth || height != lastHeight
+                || metrics.fontSize() != lastFontSize || !Objects.equals(metrics.fontFamily(), lastFontFamily)
+                || layoutVersion != lastLayoutVersion;
+        boolean contentChanged = contentVersion != lastContentVersion;
 
         lastWidth = width;
         lastHeight = height;
+        lastFontFamily = metrics.fontFamily();
+        lastFontSize = metrics.fontSize();
+        lastLayoutVersion = layoutVersion;
         lastContentVersion = contentVersion;
-        sceneDirty = false;
-        if (syncScene) {
-            syncSceneGraph(width, height);
+
+        if (layoutChanged) {
+            return FrameType.LAYOUT;
         }
-        renderVisiblePanes();
+        if (contentChanged) {
+            return FrameType.CONTENT;
+        }
+        return FrameType.IDLE;
     }
 
-    private void markSceneDirty() {
-        sceneDirty = true;
-    }
-
-    private void syncSceneGraph(double width, double height) {
+    // Full recomposite onto the retained canvas: lay the tab out, clear to the gap colour,
+    // draw the tab strip, then paint every pane bottom-to-top (panes() puts the active
+    // floating pane last == on top).
+    private void renderLayoutFrame() {
         double topInset = tabs.size() > 1 ? TAB_BAR_HEIGHT : 0.0;
-
-        paneLayer.resizeRelocate(0.0, 0.0, width, height);
-        updateTabBar(width, topInset);
-
         if (!tabs.isEmpty()) {
-            currentTab().layout(width, height, topInset);
+            currentTab().layout(canvas.getWidth(), canvas.getHeight(), topInset);
         }
-
         List<TerminalPane> panes = currentPanes();
-        retainNodes(allOpenPanes());
-        List<TerminalPaneNode> orderedNodes = new ArrayList<>(panes.size());
+        // Sync each pane's ghostty grid to its (possibly new) bounds; a no-op when unchanged.
         for (TerminalPane pane : panes) {
             pane.fitToBounds();
-            TerminalPaneNode node = nodeFor(pane);
-            node.resizeRelocate(Math.round(pane.x()), Math.round(pane.y()), pane.width(), pane.height());
-            orderedNodes.add(node);
         }
-        paneLayer.getChildren().setAll(orderedNodes);
+
+        GraphicsContext gc = beginFrame();
+        paneContentVersion.keySet().retainAll(panes);
+        gc.setFill(GAP_BACKGROUND);
+        gc.fillRect(0, 0, canvas.getWidth(), canvas.getHeight());
+        if (topInset > 0.0) {
+            drawTabBar(gc, canvas.getWidth(), topInset);
+        }
+        for (TerminalPane pane : panes) {
+            paneContentVersion.put(pane, pane.paintFull(gc, isActive(pane)));
+        }
+        drawPaneSyncOverlay(gc, panes);
+        imageOverlay.sync(panes);
     }
 
-    private void renderVisiblePanes() {
-        for (TerminalPane pane : currentPanes()) {
-            TerminalPaneNode node = nodes.get(pane);
-            if (node != null) {
-                node.renderIncremental(isActive(pane));
+    // Repaint just the panes whose content changed, directly on the retained canvas. Each pane
+    // clips itself to its rect minus the panes above it, so a lower pane's repaint can't bleed
+    // over one stacked on top — no restore pass needed. Bounds and grids can't have changed
+    // without a layout frame, so a content frame reuses the existing layout untouched.
+    private void renderContentFrame() {
+        List<TerminalPane> panes = currentPanes();
+        GraphicsContext gc = beginFrame();
+
+        for (TerminalPane pane : panes) {
+            Long drawn = paneContentVersion.get(pane);
+            if (drawn != null && drawn == pane.contentVersion()) {
+                continue;
             }
+            paneContentVersion.put(pane, pane.paintIncremental(gc, isActive(pane)));
+            imageOverlay.updatePane(pane);
         }
+        drawPaneSyncOverlay(gc, panes);
     }
 
-    private TerminalPaneNode nodeFor(TerminalPane pane) {
-        return nodes.computeIfAbsent(pane, this::createNode);
+    private GraphicsContext beginFrame() {
+        GraphicsContext gc = canvas.getGraphicsContext2D();
+        gc.setFontSmoothingType(FontSmoothingType.LCD); // the per-cell renderer relies on LCD
+        return gc;
     }
 
-    private TerminalPaneNode createNode(TerminalPane pane) {
-        TerminalPaneNode node = new TerminalPaneNode(pane, metrics);
-        node.setOnMousePressed(event -> handleMousePressed(pane, event));
-        node.setOnMouseReleased(event -> handleMouseReleased(pane, event));
-        node.setOnMouseDragged(event -> handleMouseDragged(pane, event));
-        node.setOnMouseMoved(event -> handleMouseMoved(pane, event));
-        node.setOnScroll(event -> handleScroll(pane, event));
-        return node;
+    // Thin tab strip: one equal-width segment per tab, the current one highlighted, with a
+    // small 1-based number centred in each segment.
+    private void drawTabBar(GraphicsContext gc, double width, double barHeight) {
+        int count = tabs.size();
+        Font barFont = Font.font(metrics.fontFamily(), Math.max(9.0, Math.min(13.0, barHeight * 0.62)));
+        gc.setFont(barFont);
+        gc.setFontSmoothingType(FontSmoothingType.GRAY);
+        gc.setTextAlign(TextAlignment.CENTER);
+        gc.setTextBaseline(VPos.CENTER);
+
+        double gap = 1.0;
+        double segmentWidth = width / count;
+        for (int i = 0; i < count; i++) {
+            double x = i * segmentWidth;
+            boolean current = i == currentTabIndex;
+            gc.setFill(current ? Color.rgb(45, 55, 72) : Color.rgb(22, 24, 28));
+            gc.fillRect(x, 0.0, segmentWidth - gap, barHeight);
+            gc.setFill(current ? TAB_TEXT : Color.rgb(128, 136, 148));
+            gc.fillText(Integer.toString(i + 1), x + (segmentWidth - gap) / 2.0, barHeight / 2.0);
+        }
+
+        // Restore the defaults the cell renderer relies on (left-aligned, baseline, LCD).
+        gc.setTextAlign(TextAlignment.LEFT);
+        gc.setTextBaseline(VPos.BASELINE);
+        gc.setFontSmoothingType(FontSmoothingType.LCD);
     }
 
-    private void retainNodes(List<TerminalPane> openPanes) {
-        Set<TerminalPane> open = new HashSet<>(openPanes);
-        nodes.keySet().removeIf(pane -> !open.contains(pane));
-    }
-
-    private void updateTabBar(double width, double barHeight) {
-        tabBar.setVisible(barHeight > 0.0);
-        tabBar.setManaged(false);
-        tabBar.resizeRelocate(0.0, 0.0, width, barHeight);
-        tabBar.getChildren().clear();
-        if (barHeight <= 0.0) {
+    private void drawPaneSyncOverlay(GraphicsContext gc, List<TerminalPane> panes) {
+        Set<TerminalPane> highlighted = paneSyncSelectMode ? paneSyncSelection : paneSyncPanes;
+        if (highlighted.isEmpty()) {
             return;
         }
 
-        double segmentWidth = width / tabs.size();
-        for (int i = 0; i < tabs.size(); i++) {
-            Label label = new Label(Integer.toString(i + 1));
-            boolean current = i == currentTabIndex;
-            label.setAlignment(Pos.CENTER);
-            label.setTextFill(current ? TAB_TEXT : TAB_INACTIVE_TEXT);
-            label.setBackground(new Background(new BackgroundFill(
-                    current ? TAB_ACTIVE_BACKGROUND : TAB_INACTIVE_BACKGROUND,
-                    CornerRadii.EMPTY,
-                    null)));
-            label.setFont(javafx.scene.text.Font.font(metrics.fontFamily(), Math.max(9.0, Math.min(13.0, barHeight * 0.62))));
-            label.setMinSize(0.0, barHeight);
-            label.setPrefSize(Math.max(0.0, segmentWidth - 1.0), barHeight);
-            label.setMaxSize(Double.MAX_VALUE, barHeight);
-            final int index = i;
-            label.setOnMousePressed(event -> {
-                currentTabIndex = index;
-                markSceneDirty();
-                root.requestFocus();
-                event.consume();
-            });
-            tabBar.getChildren().add(label);
+        gc.save();
+        try {
+            gc.setLineWidth(PANE_SYNC_BORDER_WIDTH);
+            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()) + 2.0;
+                double y = Math.round(pane.y()) + 2.0;
+                double width = Math.max(0.0, pane.width() - 4.0);
+                double height = Math.max(0.0, pane.height() - 4.0);
+                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(TerminalPane pane, MouseEvent event) {
-        root.requestFocus();
+    private void handleMousePressed(MouseEvent event) {
+        canvas.requestFocus();
+        TerminalPane pane = paneAt(event.getX(), event.getY());
+        if (pane == null) {
+            return;
+        }
+
         focus(pane);
         pressedButton = mouseButton(event);
         mouseButtonPressed = true;
@@ -303,38 +597,61 @@ public final class Compositor {
         if (target == null) {
             return;
         }
-        send(pane, target, MouseInput.press(pressedButton, localX(event.getX(), target), localY(event.getY(), target), modifiers(event)), true, event);
+        send(pane, target, MouseInput.press(pressedButton, localX(event.getX(), pane, target), localY(event.getY(), pane, target), modifiers(event)), true, event);
     }
 
-    private void handleMouseReleased(TerminalPane pane, MouseEvent event) {
+    private void handleMouseReleased(MouseEvent event) {
+        TerminalPane pane = paneAt(event.getX(), event.getY());
+        if (pane == null) {
+            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(), target), localY(event.getY(), target), modifiers(event)), false, event);
+            send(pane, target, MouseInput.release(button, localX(event.getX(), pane, target), localY(event.getY(), pane, target), modifiers(event)), false, event);
         }
         mouseButtonPressed = false;
         pressedButton = MouseButton.UNKNOWN;
     }
 
-    private void handleMouseDragged(TerminalPane pane, MouseEvent event) {
+    private void handleMouseDragged(MouseEvent event) {
+        TerminalPane pane = paneAt(event.getX(), event.getY());
+        if (pane == null) {
+            pane = activePane(); // dragged outside every pane: route to the active one
+        }
+        if (pane == null) {
+            return;
+        }
+
         MouseButton button = pressedButton == MouseButton.UNKNOWN ? mouseButton(event) : pressedButton;
         MouseTarget target = mouseTarget(pane);
         if (target == null) {
             return;
         }
-        send(pane, target, MouseInput.drag(button, localX(event.getX(), target), localY(event.getY(), target), modifiers(event)), true, event);
+        send(pane, target, MouseInput.drag(button, localX(event.getX(), pane, target), localY(event.getY(), pane, target), modifiers(event)), true, event);
     }
 
-    private void handleMouseMoved(TerminalPane pane, MouseEvent event) {
+    private void handleMouseMoved(MouseEvent event) {
+        TerminalPane pane = paneAt(event.getX(), event.getY());
+        if (pane == null) {
+            return;
+        }
+
         MouseTarget target = mouseTarget(pane);
         if (target == null) {
             return;
         }
-        send(pane, target, MouseInput.motion(localX(event.getX(), target), localY(event.getY(), target), modifiers(event)), mouseButtonPressed, event);
+        send(pane, target, MouseInput.motion(localX(event.getX(), pane, target), localY(event.getY(), pane, target), modifiers(event)), mouseButtonPressed, event);
     }
 
-    private void handleScroll(TerminalPane pane, ScrollEvent event) {
-        root.requestFocus();
+    private void handleScroll(ScrollEvent event) {
+        TerminalPane pane = paneAt(event.getX(), event.getY());
+        if (pane == null) {
+            return;
+        }
+
+        canvas.requestFocus();
         focus(pane);
         int direction = scrollDirection(event);
         if (direction == 0) {
@@ -346,8 +663,9 @@ public final class Compositor {
         MouseTarget target = mouseTarget(pane);
         boolean sent = false;
         if (target != null) {
-            double ex = localX(event.getX(), target);
-            double ey = localY(event.getY(), target);
+            // The wheel sends one button press per scrolled row; resolve the position once.
+            double ex = localX(event.getX(), pane, target);
+            double ey = localY(event.getY(), pane, target);
             KeyModifiers modifiers = modifiers(event);
             for (int i = 0; i < rows; i++) {
                 if (!send(pane, target, MouseInput.press(wheelButton, ex, ey, modifiers), mouseButtonPressed, event)) {
@@ -357,11 +675,14 @@ public final class Compositor {
             }
         }
         if (!sent) {
+            // Not consumed by the app (e.g. mouse reporting off): scroll the local viewport.
             pane.scrollViewport(direction > 0 ? -rows : rows);
             event.consume();
         }
     }
 
+    // Forward an already-positioned mouse event to the pane, consuming it if the pane (i.e.
+    // the app running in it) acted on it. Returns whether it was sent.
     private boolean send(TerminalPane pane, MouseTarget target, MouseInput input, boolean anyButtonPressed, InputEvent event) {
         boolean sent = pane.sendMouse(input, target.size(), anyButtonPressed);
         if (sent) {
@@ -370,6 +691,17 @@ public final class Compositor {
         return sent;
     }
 
+    private TerminalPane paneAt(double x, double y) {
+        List<TerminalPane> panes = currentPanes();
+        for (int i = panes.size() - 1; i >= 0; i--) {
+            TerminalPane pane = panes.get(i);
+            if (x >= pane.x() && x < pane.x() + pane.width() && y >= pane.y() && y < pane.y() + pane.height()) {
+                return pane;
+            }
+        }
+        return null;
+    }
+
     private MouseTarget mouseTarget(TerminalPane pane) {
         if (pane.width() <= 2 * TerminalMetrics.PADDING || pane.height() <= 2 * TerminalMetrics.PADDING) {
             return null;
@@ -384,12 +716,14 @@ public final class Compositor {
         return new MouseTarget(MouseEncoderSize.of(screenWidth, screenHeight, cellWidth, cellHeight), screenWidth, screenHeight);
     }
 
-    private static double localX(double nodeX, MouseTarget target) {
-        return clamp(nodeX - TerminalMetrics.PADDING, 0.0, target.screenWidth() - 1.0);
+    // Resolve a canvas-space pointer position to a pane-local pixel coordinate, clamped to
+    // the pane's reported screen size (what ghostty's mouse encoder expects).
+    private static double localX(double canvasX, TerminalPane pane, MouseTarget target) {
+        return clamp(canvasX - pane.x() - TerminalMetrics.PADDING, 0.0, target.screenWidth() - 1.0);
     }
 
-    private static double localY(double nodeY, MouseTarget target) {
-        return clamp(nodeY - TerminalMetrics.PADDING, 0.0, target.screenHeight() - 1.0);
+    private static double localY(double canvasY, TerminalPane pane, MouseTarget target) {
+        return clamp(canvasY - pane.y() - TerminalMetrics.PADDING, 0.0, target.screenHeight() - 1.0);
     }
 
     private static double clamp(double value, double min, double max) {
@@ -437,6 +771,13 @@ public final class Compositor {
         };
     }
 
+    // What one render() pass should do, decided from the change trackers in nextFrame().
+    private enum FrameType {
+        IDLE,     // nothing changed since the last frame
+        LAYOUT,   // geometry/font/tab/pane set changed: clear and repaint everything
+        CONTENT   // only terminal content changed: repaint the panes that changed
+    }
+
     private record MouseTarget(MouseEncoderSize size, long screenWidth, long screenHeight) {
     }
 }

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/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/KeyEncoder.java

@@ -26,7 +26,7 @@ final class KeyEncoder {
         return switch (code) {
             case ENTER -> "\r";
             case BACK_SPACE -> "\u007f";
-            case TAB -> "\t";
+            case TAB -> event.isShiftDown() ? "\u001b[Z" : "\t";
             case ESCAPE -> "\u001b";
             case UP -> "\u001b[A";
             case DOWN -> "\u001b[B";

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

@@ -0,0 +1,32 @@
+package com.gregor.jprototerm;
+
+import javafx.scene.image.Image;
+
+/**
+ * A single kitty image to display, produced by the renderer and consumed by {@link
+ * KittyImageOverlay}. Images are not painted onto the canvas; each becomes a retained
+ * {@code ImageView} node positioned over the pane. The {@code source*} fields are the region of
+ * {@link #image()} to show (in image pixels); the {@code x/y/width/height} are where to put it,
+ * in scene coordinates (the same space the pane's clip {@code Shape} lives in).
+ *
+ * <p>{@code imageId}+{@code placementId} identify the placement so the overlay can reuse the
+ * same node across frames instead of recreating it.
+ */
+record KittyImageNode(
+        long imageId,
+        long placementId,
+        Image image,
+        double sourceX,
+        double sourceY,
+        double sourceWidth,
+        double sourceHeight,
+        double x,
+        double y,
+        double width,
+        double height
+) {
+    /** Stable per-pane key for node reuse. Packs the two u32 ids without collision. */
+    long key() {
+        return (imageId << 32) | (placementId & 0xffffffffL);
+    }
+}

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

@@ -0,0 +1,151 @@
+package com.gregor.jprototerm;
+
+import javafx.geometry.Rectangle2D;
+import javafx.scene.Group;
+import javafx.scene.Node;
+import javafx.scene.image.ImageView;
+import javafx.scene.layout.Pane;
+import javafx.scene.shape.Rectangle;
+import javafx.scene.shape.Shape;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Renders kitty graphics images as retained scene-graph nodes layered over the {@link Compositor}
+ * canvas, instead of compositing them onto the canvas. Each pane gets a {@link Group} clipped to
+ * that pane's region (the same clip {@code Shape} the canvas renderer uses), and each visible
+ * image placement is an {@link ImageView} inside it, reused across frames so an unchanged image
+ * costs nothing to redraw.
+ *
+ * <p>The overlay {@link #node()} is mouse-transparent and sits above the canvas in the window's
+ * {@code StackPane}; its children use scene coordinates, which line up with the canvas because
+ * both fill the same root.
+ */
+final class KittyImageOverlay {
+    private final Pane root = new Pane();
+    private final Map<TerminalPane, PaneOverlay> overlays = new HashMap<>();
+
+    KittyImageOverlay() {
+        // Input belongs to the canvas underneath; the overlay only shows pixels.
+        root.setMouseTransparent(true);
+        root.setManaged(false);
+    }
+
+    Node node() {
+        return root;
+    }
+
+    /**
+     * Full reconcile to {@code panes} (bottom-to-top): drop overlays for panes that went away,
+     * refresh each surviving/added pane's images and clip, and order the per-pane groups to match
+     * the pane z-order. Called on layout frames, after the panes have painted.
+     */
+    void sync(List<TerminalPane> panes) {
+        Iterator<Map.Entry<TerminalPane, PaneOverlay>> it = overlays.entrySet().iterator();
+        while (it.hasNext()) {
+            Map.Entry<TerminalPane, PaneOverlay> entry = it.next();
+            if (!panes.contains(entry.getKey())) {
+                root.getChildren().remove(entry.getValue().group);
+                it.remove();
+            }
+        }
+        for (TerminalPane pane : panes) {
+            updatePane(pane);
+        }
+        // Only panes that actually have images get a group; order those to match pane z-order.
+        List<Node> ordered = new ArrayList<>(panes.size());
+        for (TerminalPane pane : panes) {
+            PaneOverlay overlay = overlays.get(pane);
+            if (overlay != null) {
+                ordered.add(overlay.group);
+            }
+        }
+        if (!root.getChildren().equals(ordered)) {
+            root.getChildren().setAll(ordered);
+        }
+    }
+
+    /**
+     * Refresh one pane's images and clip (called on content frames for each repainted pane).
+     * Creates the pane's group if this is the first time it has shown an image.
+     */
+    void updatePane(TerminalPane pane) {
+        List<KittyImageNode> images = pane.kittyImages();
+        PaneOverlay overlay = overlays.get(pane);
+        if (overlay == null) {
+            if (images.isEmpty()) {
+                return;
+            }
+            overlay = new PaneOverlay();
+            overlays.put(pane, overlay);
+            root.getChildren().add(overlay.group);
+        }
+        overlay.group.setClip(clipFor(pane));
+        reconcile(overlay, images);
+    }
+
+    private static void reconcile(PaneOverlay overlay, List<KittyImageNode> images) {
+        Set<Long> seen = new HashSet<>();
+        for (KittyImageNode node : images) {
+            long key = node.key();
+            seen.add(key);
+            ImageView view = overlay.views.get(key);
+            if (view == null) {
+                view = new ImageView();
+                view.setManaged(false);
+                view.setSmooth(true);
+                view.setPreserveRatio(false);
+                overlay.views.put(key, view);
+                overlay.group.getChildren().add(view);
+            }
+            apply(view, node);
+        }
+        if (overlay.views.size() == seen.size()) {
+            return;
+        }
+        Iterator<Map.Entry<Long, ImageView>> it = overlay.views.entrySet().iterator();
+        while (it.hasNext()) {
+            Map.Entry<Long, ImageView> entry = it.next();
+            if (!seen.contains(entry.getKey())) {
+                overlay.group.getChildren().remove(entry.getValue());
+                it.remove();
+            }
+        }
+    }
+
+    private static void apply(ImageView view, KittyImageNode node) {
+        if (view.getImage() != node.image()) {
+            view.setImage(node.image());
+        }
+        view.setViewport(new Rectangle2D(node.sourceX(), node.sourceY(), node.sourceWidth(), node.sourceHeight()));
+        view.setFitWidth(node.width());
+        view.setFitHeight(node.height());
+        view.setLayoutX(node.x());
+        view.setLayoutY(node.y());
+    }
+
+    // The pane's occlusion clip when one is set (rect minus covering panes), else the pane's
+    // plain bounds so an image can't spill outside its pane. Matches Tab's pixel snapping.
+    private static Shape clipFor(TerminalPane pane) {
+        Shape clip = pane.clip();
+        if (clip != null) {
+            return clip;
+        }
+        return new Rectangle(Math.round(pane.x()), Math.round(pane.y()), pane.width(), pane.height());
+    }
+
+    private static final class PaneOverlay {
+        private final Group group = new Group();
+        private final Map<Long, ImageView> views = new HashMap<>();
+
+        private PaneOverlay() {
+            group.setManaged(false);
+        }
+    }
+}

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

@@ -9,9 +9,14 @@ import java.lang.foreign.MemorySegment;
 import java.lang.foreign.SymbolLookup;
 import java.lang.foreign.ValueLayout;
 import java.lang.invoke.MethodHandle;
+import java.io.IOException;
+import java.nio.file.Files;
+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.
@@ -30,6 +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");
@@ -60,7 +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; }
@@ -74,6 +87,7 @@ public final class LinuxPty implements AutoCloseable {
     private static final long SPAWN_ACTIONS_SIZE = 256;
     private static final long SPAWN_ATTR_SIZE = 512;
 
+    private static final MethodHandle TCGETPGRP = handle("tcgetpgrp", FD_INT_INT);
     private static final MethodHandle POSIX_OPENPT = handle("posix_openpt", FD_INT_INT);
     private static final MethodHandle GRANTPT = handle("grantpt", FD_INT_INT);
     private static final MethodHandle UNLOCKPT = handle("unlockpt", FD_INT_INT);
@@ -97,14 +111,40 @@ public final class LinuxPty implements AutoCloseable {
 
     private final Arena arena = Arena.ofShared();
     private final MemorySegment readBuffer = arena.allocate(65536);
+    private final MemorySegment writeBuffer = arena.allocate(65536);
     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;
+        };
     }
 
     /**
@@ -113,8 +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");
@@ -153,7 +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);
@@ -186,21 +228,43 @@ public final class LinuxPty implements AutoCloseable {
             return;
         }
         synchronized (writeLock) {
-            try (Arena a = Arena.ofConfined()) {
-                MemorySegment buf = a.allocate(data.length);
-                MemorySegment.copy(data, 0, buf, ValueLayout.JAVA_BYTE, 0, data.length);
-                long offset = 0;
-                while (offset < data.length) {
-                    long n = callLong(WRITE, masterFd, buf.asSlice(offset), data.length - offset);
-                    if (n < 0) {
+            int offset = 0;
+            while (offset < data.length) {
+                int chunk = (int) Math.min(writeBuffer.byteSize(), data.length - offset);
+                MemorySegment.copy(data, offset, writeBuffer, ValueLayout.JAVA_BYTE, 0, chunk);
+
+                long written = 0;
+                while (written < chunk) {
+                    long n = callLong(WRITE, masterFd, writeBuffer.asSlice(written), chunk - written);
+                    if (n <= 0) {
                         throw new IllegalStateException("write to pty failed");
                     }
-                    offset += n;
+                    written += n;
                 }
+                offset += chunk;
             }
         }
     }
 
+    /**
+     * Best-effort current working directory of the terminal's foreground process group, read from
+     * {@code /proc}. This tracks the directory the user is actually in (a {@code cd} in the shell,
+     * or a child program that changed dir), so a newly opened pane can start there. Falls back to
+     * the shell's own pid, and returns {@code null} if it cannot be determined.
+     */
+    public String currentWorkingDirectory() {
+        if (closed) {
+            return null;
+        }
+        int pgid = callInt(TCGETPGRP, masterFd);
+        int target = pgid > 0 ? pgid : pid;
+        try {
+            return Files.readSymbolicLink(Path.of("/proc", Integer.toString(target), "cwd")).toString();
+        } catch (IOException | RuntimeException ex) {
+            return null;
+        }
+    }
+
     /** Resizes the terminal window. */
     public void setWinSize(int columns, int rows) {
         if (closed) {
@@ -218,14 +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

@@ -1,192 +1,36 @@
 package com.gregor.jprototerm;
 
-import javafx.animation.AnimationTimer;
-import javafx.application.Application;
-import javafx.application.Platform;
-import javafx.scene.Scene;
-import javafx.scene.control.ButtonType;
-import javafx.scene.control.ComboBox;
-import javafx.scene.control.Dialog;
-import javafx.scene.control.Label;
-import javafx.scene.control.Spinner;
-import javafx.scene.control.SpinnerValueFactory;
-import javafx.scene.input.KeyEvent;
-import javafx.scene.layout.GridPane;
-import javafx.scene.text.Font;
-import javafx.stage.Stage;
-
-import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.Path;
-
-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);
-
-        Scene scene = new Scene(compositor.node(), 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();
-        });
-        stage.show();
-        compositor.requestFocus();
-    }
-
-    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("close_pane").matches(event)) {
-            compositor.closeActivePane();
-            event.consume();
-            if (compositor.isEmpty()) {
-                // Closing the last pane quits the app.
-                compositor.close();
-                Platform.exit();
-            }
-        } 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 {
-            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 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.requestFocus();
-                });
-    }
-
-    private void openScrollbackInEditor() {
-        try {
-            Path file = Files.createTempFile("jprototerm-scrollback-", ".txt");
-            Files.writeString(file, compositor.activePane().scrollbackText());
-            file.toFile().deleteOnExit();
-
-            compositor.activePane().send(scrollbackEditorCommand(file) + "\r");
-        } 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/RenderProfiler.java

@@ -1,79 +0,0 @@
-package com.gregor.jprototerm;
-
-/**
- * Lightweight render profiler, disabled unless {@code -Djprototerm.profile=true} (or the
- * {@code JPROTOTERM_PROFILE=1} environment variable) is set. It accumulates wall-clock nanos
- * into a handful of buckets and prints aggregate per-frame stats to stderr every
- * {@code jprototerm.profile.frames} render invocations (default 120).
- *
- * <p>All render work runs on the JavaFX application thread, so the accumulators are plain
- * fields with no synchronization.
- *
- * <p>Caveat: JavaFX canvas drawing is deferred to the QuantumRenderer thread, so the
- * {@link #DRAW} bucket measures only the cost of <em>recording</em> draw commands, not the
- * GPU paint. Pair this with {@code -Djavafx.pulseLogger=true} to see the render-thread side.
- */
-final class RenderProfiler {
-    static final int SNAPSHOT = 0;
-    static final int FINGERPRINT = 1;
-    static final int DRAW = 2;
-    static final int FRAME = 3;
-    static final int UPDATE = 4;
-    static final int MARSHAL = 5;
-    private static final int BUCKETS = 6;
-    private static final String[] NAMES =
-            {"snapshot", "fingerprint", "draw", "frame-total", "update", "marshal"};
-
-    private static final boolean ENABLED =
-            Boolean.getBoolean("jprototerm.profile") || "1".equals(System.getenv("JPROTOTERM_PROFILE"));
-    private static final int DUMP_FRAMES = Integer.getInteger("jprototerm.profile.frames", 120);
-
-    private static final long[] totalNanos = new long[BUCKETS];
-    private static final long[] counts = new long[BUCKETS];
-    private static int frames;
-
-    private RenderProfiler() {
-    }
-
-    static boolean enabled() {
-        return ENABLED;
-    }
-
-    /** Returns a start timestamp, or 0 when profiling is disabled. */
-    static long start() {
-        return ENABLED ? System.nanoTime() : 0L;
-    }
-
-    /** Records the time elapsed since {@code startNanos} into {@code bucket}. */
-    static void stop(int bucket, long startNanos) {
-        if (!ENABLED) {
-            return;
-        }
-        totalNanos[bucket] += System.nanoTime() - startNanos;
-        counts[bucket]++;
-    }
-
-    /** Marks the end of one render invocation; dumps and resets every {@code DUMP_FRAMES}. */
-    static void frame() {
-        if (!ENABLED) {
-            return;
-        }
-        if (++frames < DUMP_FRAMES) {
-            return;
-        }
-        dump();
-    }
-
-    private static void dump() {
-        StringBuilder sb = new StringBuilder(192);
-        sb.append("[render-profile] ").append(frames).append(" renders");
-        for (int i = 0; i < BUCKETS; i++) {
-            double totalMs = totalNanos[i] / 1_000_000.0;
-            sb.append(String.format(" | %s %.3fms/f (n=%d)", NAMES[i], totalMs / frames, counts[i]));
-            totalNanos[i] = 0;
-            counts[i] = 0;
-        }
-        System.err.println(sb);
-        frames = 0;
-    }
-}

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

@@ -0,0 +1,45 @@
+package com.gregor.jprototerm;
+
+import dev.jlibghostty.KittyGraphics;
+import dev.jlibghostty.RenderStateSnapshot;
+import javafx.scene.shape.Shape;
+
+import java.util.Optional;
+
+/**
+ * The read-only view of a pane that a {@link TerminalRenderer} draws: its on-screen rect, its
+ * current render snapshot, and its kitty-graphics state. Decoupling the renderer from
+ * {@link TerminalPane} through this interface lets the renderer be swapped (e.g. a debug
+ * renderer that just outlines bounds and clip bands) and unit-tested against a synthetic
+ * target without a real terminal.
+ */
+interface RenderTarget {
+    double x();
+
+    double y();
+
+    double width();
+
+    double height();
+
+    /** Whether kitty graphics should be drawn for this target at all. */
+    boolean kittyEnabled();
+
+    Optional<KittyGraphics> kittyGraphics();
+
+    /**
+     * Incremental snapshot: only rows that changed since the last frame are populated. May be
+     * {@code null} before the first snapshot exists.
+     */
+    RenderStateSnapshot snapshot();
+
+    /** Full snapshot with every row populated, regardless of dirty state. */
+    RenderStateSnapshot snapshotFull();
+
+    /**
+     * The region this target may draw into, or {@code null} to clip to its plain rect. Set at
+     * layout time (a tiled pane gets its rect minus the floating panes that cover it), so the
+     * renderer can clip its own output and never paint over a pane on top.
+     */
+    Shape clip();
+}

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

@@ -2,6 +2,7 @@ package com.gregor.jprototerm;
 
 import java.nio.charset.StandardCharsets;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -20,27 +21,59 @@ public final class ShellSession implements AutoCloseable {
         });
     }
 
-    public static ShellSession start(String shell, Map<String, String> envOverride, TerminalPane pane, int columns, int rows) {
+    /**
+     * Starts the configured shell. {@code shellCommand} is the executable plus its arguments (e.g.
+     * {@code ["/bin/bash", "-i"]}), spawned verbatim — any interactive flag is the user's choice in
+     * config, not assumed here.
+     */
+    public static ShellSession start(List<String> shellCommand, Map<String, String> envOverride, TerminalPane pane,
+            int columns, int rows, String workingDirectory, int closeSignal) {
         try {
-            Map<String, String> environment = new HashMap<>(System.getenv());
-            environment.put("TERM", "xterm-kitty");
-            environment.put("COLORTERM", "truecolor");
-            sanitizeWrapperEnvironment(environment);
-            environment.putAll(envOverride);
-
-            LinuxPty pty = LinuxPty.spawn(
-                    new String[] {shell, "-i"},
-                    environment,
-                    System.getProperty("user.home"));
-            ShellSession session = new ShellSession(pty);
-            session.resize(columns, rows);
-            return session;
+            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 " + shell, ex);
+            throw new IllegalStateException("Could not start shell " + String.join(" ", shellCommand), ex);
         }
     }
 
+    /**
+     * Starts a session whose first and only process is {@code /bin/sh -c command}, so the program
+     * runs deterministically from the start rather than being typed into an interactive shell —
+     * there is no startup/rc race to lose or mangle the input. When the process exits the pty
+     * closes and the pane auto-closes. {@code /bin/sh -c} is used (not the user's configured shell)
+     * because it is the portable way to run a command line and does not depend on shell-specific
+     * 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 closeSignal) {
+        try {
+            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);
+        }
+    }
+
+    private static ShellSession spawn(String[] argv, Map<String, String> envOverride,
+            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");
+        sanitizeWrapperEnvironment(environment);
+        environment.putAll(envOverride);
+
+        LinuxPty pty = LinuxPty.spawn(
+                argv,
+                environment,
+                workingDirectory != null ? workingDirectory : System.getProperty("user.home"),
+                closeSignal);
+        ShellSession session = new ShellSession(pty);
+        session.resize(columns, rows);
+        return session;
+    }
+
     /**
      * Strips the variables injected by the Nix launcher wrapper from the shell's
      * environment so they do not leak into terminal subprocesses.
@@ -63,12 +96,37 @@ 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) {
         reader.submit(() -> readOutput(pane));
     }
 
+    /** Best-effort current working directory of the running shell, or {@code null} if unknown. */
+    public String currentWorkingDirectory() {
+        return closed ? null : pty.currentWorkingDirectory();
+    }
+
     public void resize(int columns, int rows) {
         if (closed) {
             return;
@@ -113,12 +171,36 @@ public final class ShellSession implements AutoCloseable {
                 pane.write("\r\nshell output stopped: " + ex.getMessage() + "\r\n");
             }
         }
+        // The stream ended without us closing the session, so the process exited on its own (the
+        // user typed `exit`, or a one-shot command pane finished). Let the pane tear itself down.
+        if (!closed) {
+            pane.handleSessionExit();
+        }
     }
 
     @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

@@ -1,8 +1,13 @@
 package com.gregor.jprototerm;
 
+import javafx.scene.shape.Rectangle;
+import javafx.scene.shape.Shape;
+
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.Consumer;
 import java.util.stream.Stream;
 
 /**
@@ -13,15 +18,29 @@ 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
+    // compositor can close that pane and reap the tab/app if it was the last one.
+    private final Consumer<TerminalPane> onPaneExit;
     private final List<TerminalPane> tiled = new ArrayList<>();
     private final List<TerminalPane> floating = new ArrayList<>();
     private boolean floatingVisible;
     private TerminalPane active;
+    private final String initialWorkingDirectory;
     // The floating pane to re-focus when the group is shown again, and to prefer when promoting
     // after the last tiled pane closes.
     private TerminalPane lastFocusedFloating;
+    // The tiled pane to re-focus when the floating group is hidden.
+    private TerminalPane lastFocusedTiled;
     // Last laid-out size, so a newly opened pane can be created at roughly its eventual rect
     // (and thus grid). Seeded from the configured window size for the first pane, which is
     // opened before any layout pass runs.
@@ -30,13 +49,24 @@ final class Tab implements AutoCloseable {
     private double lastTopInset;
     // Bumped whenever one of this tab's panes changes content; the compositor reads the current
     // tab's value each frame as an O(1) "anything to repaint?" check.
-    private long contentVersion;
+    private final AtomicLong contentVersion = new AtomicLong();
 
-    Tab(AppConfig config, TerminalMetrics metrics) {
+    Tab(AppConfig config, TerminalMetrics metrics, Consumer<TerminalPane> onPaneExit) {
+        this(config, metrics, null, onPaneExit);
+    }
+
+    /**
+     * Creates a tab whose first pane starts in {@code initialWorkingDirectory} (e.g. the cwd of the
+     * pane that was active when this tab was opened), or the user's home when {@code null}.
+     */
+    Tab(AppConfig config, TerminalMetrics metrics, String initialWorkingDirectory,
+            Consumer<TerminalPane> onPaneExit) {
         this.config = config;
         this.metrics = metrics;
+        this.onPaneExit = onPaneExit;
         this.lastWidth = config.windowWidth();
         this.lastHeight = config.windowHeight();
+        this.initialWorkingDirectory = initialWorkingDirectory;
         TerminalPane first = openPane(false);
         tiled.add(first);
         active = first;
@@ -51,7 +81,7 @@ final class Tab implements AutoCloseable {
     }
 
     long contentVersion() {
-        return contentVersion;
+        return contentVersion.get();
     }
 
     /**
@@ -64,28 +94,43 @@ final class Tab implements AutoCloseable {
         }
         List<TerminalPane> ordered = new ArrayList<>(tiled.size() + floating.size());
         ordered.addAll(tiled);
-        for (TerminalPane pane : floating) {
-            if (pane != active) {
-                ordered.add(pane);
-            }
-        }
-        if (floating.contains(active)) {
-            ordered.add(active); // active floating pane on top
-        }
+        ordered.addAll(floatingOrder());
         return List.copyOf(ordered);
     }
 
-    List<TerminalPane> allPanes() {
-        List<TerminalPane> all = new ArrayList<>(tiled.size() + floating.size());
-        all.addAll(tiled);
-        all.addAll(floating);
-        return List.copyOf(all);
+    // 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) {
+                order.add(pane);
+            }
+        }
+        if (floating.contains(active)) {
+            order.add(active);
+        }
+        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;
@@ -105,16 +150,54 @@ 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);
         }
+
+        assignClips();
+    }
+
+    // Give each pane its clip region for the next paints, so repainting a pane on a content
+    // frame can never bleed over one stacked on top of it. Each pane is clipped to its rect
+    // minus the union of the panes above it: floating panes are clipped by the floating panes
+    // higher in the stack, and tiled panes by the whole floating group. When nothing floats,
+    // every pane clips to its plain bounds.
+    private void assignClips() {
+        if (!floatingVisible || floating.isEmpty()) {
+            allPanes().forEach(pane -> pane.setClip(null));
+            return;
+        }
+
+        // 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--) {
+            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);
+        }
+
+        // `above` is now the union of every floating pane; tiled panes sit under all of them.
+        for (TerminalPane pane : tiled) {
+            pane.setClip(Shape.subtract(rectOf(pane), above));
+        }
+    }
+
+    // Match the renderer's pixel snapping (round the origin, keep width/height) so the clip
+    // lines up exactly with where the floating panes are drawn.
+    private static Rectangle rectOf(TerminalPane pane) {
+        return new Rectangle(Math.round(pane.x()), Math.round(pane.y()), pane.width(), pane.height());
     }
 
     boolean navigate(Direction direction) {
@@ -141,7 +224,7 @@ final class Tab implements AutoCloseable {
         if (floatingVisible) {
             floatingVisible = false;
             if (floating.contains(active)) {
-                setActive(tiled.get(0));
+                setActive(tiled.contains(lastFocusedTiled) ? lastFocusedTiled : tiled.get(0));
             }
         } else {
             floatingVisible = true;
@@ -154,26 +237,71 @@ final class Tab implements AutoCloseable {
         if (floatingVisible) {
             createFloatingPane();
         } else {
-            TerminalPane pane = openPane(false);
-            tiled.add(pane);
-            setActive(pane);
+            createTiledPane(paneWorkingDirectory());
         }
     }
 
-    void closeActivePane() {
-        TerminalPane closing = active;
-        boolean wasFloating = floating.remove(closing);
-        if (!wasFloating) {
-            tiled.remove(closing);
+    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();
+            return;
         }
+        floatingVisible = true;
+        int current = floating.indexOf(active); // -1 when the active pane is tiled
+        setActive(floating.get((current + 1 + floating.size()) % floating.size()));
+    }
+
+    /** Promotes the active floating pane to a tiled pane, joining the tiled row. No-op otherwise. */
+    void toggleActiveFloating() {
+        TerminalPane toggled = active;
+        if (floating.remove(toggled)) {
+            lastFocusedFloating = floating.isEmpty() ? null : floating.get(floating.size() - 1);
+            tiled.add(toggled);
+            floatingVisible = false;
+            setActive(toggled);
+        } else if (tiled.remove(toggled)) {
+            lastFocusedTiled = tiled.isEmpty() ? null : tiled.get(tiled.size() -1);
+            floating.add(toggled);
+            floatingVisible = true;
+            setActive(toggled);
+        }
+    }
+
+    /**
+     * Closes {@code closing} (the active pane on a key-bound close, or any pane whose process just
+     * exited) and re-selects the active pane only when the one that closed was active. Returns
+     * false when the pane is not in this tab. Leaves the tab empty ({@code active == null}) when its
+     * last pane closes, so the compositor can drop it.
+     */
+    boolean closePane(TerminalPane closing) {
+        boolean wasFloating = floating.remove(closing);
+        boolean wasTiled = !wasFloating && tiled.remove(closing);
+        if (!wasFloating && !wasTiled) {
+            return false; // not one of this tab's panes (already gone)
+        }
+        boolean wasActive = closing == active;
         if (closing == lastFocusedFloating) {
             lastFocusedFloating = null;
         }
+        if (closing == lastFocusedTiled) {
+            lastFocusedTiled = null;
+        }
         closing.close();
 
         if (tiled.isEmpty() && floating.isEmpty()) {
             active = null; // tab is now empty; the compositor drops it
-            return;
+            return true;
         }
 
         // Always keep a tiled base: if the last tiled pane just closed, promote a floating one
@@ -185,31 +313,54 @@ final class Tab implements AutoCloseable {
             floating.remove(promote);
             tiled.add(promote);
             if (promote == lastFocusedFloating) {
-                lastFocusedFloating = null;
-                if (!floating.isEmpty()) {
-                    lastFocusedFloating = floating.isEmpty() ? null : floating.get(nextFocussed);
-                }
+                lastFocusedFloating = floating.isEmpty() ? null : floating.get(nextFocussed);
             }
         }
         if (floating.isEmpty()) {
             floatingVisible = false;
         }
 
-        setActive(wasFloating && floatingVisible ? floating.get(floating.size() - 1) : tiled.get(0));
+        // Only the active pane closing forces a re-selection; closing a background pane (e.g. one
+        // whose process exited while another is focused) leaves focus where it is.
+        if (wasActive) {
+            setActive(wasFloating && floatingVisible
+                    ? floating.get(floating.size() - 1)
+                    : tiled.contains(lastFocusedTiled) ? lastFocusedTiled : tiled.get(0));
+        }
+        return true;
     }
 
     private void setActive(TerminalPane pane) {
         active = pane;
         if (floating.contains(pane)) {
             lastFocusedFloating = pane;
+        } else if (tiled.contains(pane)) {
+            lastFocusedTiled = pane;
+            // A tiled pane gaining focus hides the floating group: leaving it shown while a tiled
+            // pane is active strands focus behind the overlay and disables navigation.
+            floatingVisible = false;
         }
     }
 
     private void createFloatingPane() {
-        TerminalPane pane = openPane(true);
+        addFloating(openPane(true, paneWorkingDirectory()));
+    }
+
+    /**
+     * Opens a floating pane whose process runs {@code command} directly (auto-closing when it
+     * exits), rather than an interactive shell. Used for one-shot panes like the scrollback editor.
+     */
+    TerminalPane createFloatingPane(String command) {
+        double[] size = paneSize(true);
+        return addFloating(register(TerminalPane.createWithCommand(
+                config, metrics, this::markContentChanged, size[0], size[1], paneWorkingDirectory(), command)));
+    }
+
+    private TerminalPane addFloating(TerminalPane pane) {
         floating.add(pane);
         floatingVisible = true;
         setActive(pane);
+        return pane;
     }
 
     private boolean navigateFloatingStack(Direction direction) {
@@ -240,22 +391,41 @@ final class Tab implements AutoCloseable {
     }
 
     private void markContentChanged() {
-        contentVersion++;
+        contentVersion.incrementAndGet();
     }
 
     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], workingDirectory));
+    }
+
+    private double[] paneSize(boolean asFloating) {
         double availHeight = lastHeight - lastTopInset;
-        double widthPx;
-        double heightPx;
         if (asFloating) {
-            widthPx = Math.max(420, lastWidth * 0.58);
-            heightPx = Math.max(260, availHeight * 0.58);
-        } else {
-            // A new tiled pane joins the row, so each gets 1/(n+1) of the width.
-            widthPx = lastWidth / (tiled.size() + 1);
-            heightPx = availHeight;
+            return new double[] {
+                    Math.max(FLOATING_MIN_WIDTH, lastWidth * FLOATING_SIZE_FRACTION),
+                    Math.max(FLOATING_MIN_HEIGHT, availHeight * FLOATING_SIZE_FRACTION)};
         }
-        return TerminalPane.create(config, metrics, this::markContentChanged, widthPx, heightPx);
+        // A new tiled pane joins the row, so each gets 1/(n+1) of the width.
+        return new double[] {lastWidth / (tiled.size() + 1), availHeight};
+    }
+
+    // Open a new pane in the active pane's working directory, so a split/new pane lands where the
+    // user currently is. With no active pane yet (the tab's first pane), fall back to the directory
+    // this tab was opened in. null (cwd unknown) falls back to home downstream.
+    private String paneWorkingDirectory() {
+        return active != null ? active.currentWorkingDirectory() : initialWorkingDirectory;
+    }
+
+    // Wire the pane's self-exit (process ended) back to the compositor so it gets reaped.
+    private TerminalPane register(TerminalPane pane) {
+        pane.setOnExit(() -> onPaneExit.accept(pane));
+        return pane;
     }
 
     private static boolean directionFilter(Direction direction, TerminalPane current, TerminalPane candidate) {
@@ -285,4 +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

@@ -12,28 +12,44 @@ import dev.jlibghostty.RenderStateSnapshot;
 import dev.jlibghostty.ScrollViewport;
 import dev.jlibghostty.Terminal;
 import dev.jlibghostty.TerminalOptions;
+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,
- * and its on-screen geometry and grid. It does not draw itself; {@link TerminalPaneNode}
- * reads snapshots from it and represents the visible rows and kitty graphics as JavaFX nodes.
+ * and its on-screen geometry and grid. It does not draw itself — it is a {@link RenderTarget}
+ * that a {@link TerminalRenderer} paints. {@link #paintFull}/{@link #paintIncremental} are the
+ * only rendering API exposed to the {@link Compositor}, and they just delegate to that
+ * renderer; the compositor decides z-order and which rect each pane occupies.
  */
-public final class TerminalPane implements AutoCloseable {
+public final class TerminalPane implements AutoCloseable, RenderTarget {
     private final Terminal terminal;
     private final TerminalMetrics metrics;
     private final boolean kittyEnabled;
     // Run on every content change so the owning tab can bump its content version — the
     // compositor's O(1) "did the current tab change?" gate.
     private final Runnable onContentChange;
+    private final TerminalRenderer renderer;
     private final MouseEncoder mouseEncoder = new MouseEncoder();
     // A persistent render state (reused across frames) is what makes ghostty's per-row dirty
     // tracking meaningful: update() accumulates dirty since the last resetDirty().
     private final RenderState renderState = new RenderState();
     private RenderStateSnapshot cachedSnapshot;
-    private ShellSession session;
+    private 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 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().
+    private Shape clip;
     private double x;
     private double y;
     private double width;
@@ -43,14 +59,15 @@ public final class TerminalPane implements AutoCloseable {
     private int pixelWidth;
     private int pixelHeight;
     private final AtomicLong contentVersion = new AtomicLong();
-    private volatile long snapshotVersion = -1;
+    private long snapshotVersion = -1;
 
     private TerminalPane(Terminal terminal, TerminalMetrics metrics, boolean kittyEnabled,
-            Runnable onContentChange, int columns, int rows) {
+            Runnable onContentChange, TerminalRenderer renderer, int columns, int rows) {
         this.terminal = terminal;
         this.metrics = metrics;
         this.kittyEnabled = kittyEnabled;
         this.onContentChange = onContentChange;
+        this.renderer = renderer;
         this.columns = columns;
         this.rows = rows;
     }
@@ -60,19 +77,84 @@ public final class TerminalPane implements AutoCloseable {
      * columns and rows fit, and that grid is handed to ghostty and the shell at start-up. A
      * non-positive size falls back to the configured default grid (used before the first
      * layout, when no rect is known yet). The pane owns the shell session it starts and runs
-     * {@code onContentChange} on every content change.
+     * {@code onContentChange} on every content change. The shell starts in {@code workingDirectory}
+     * (e.g. the active pane's cwd), or the user's home when {@code null}.
      */
-    public static TerminalPane create(AppConfig config, TerminalMetrics metrics, Runnable onContentChange, double widthPx, double heightPx) {
+    public static TerminalPane create(AppConfig config, TerminalMetrics metrics, Runnable onContentChange,
+            double widthPx, double heightPx, String workingDirectory) {
+        TerminalPane pane = newPane(config, metrics, onContentChange, widthPx, heightPx);
+        attachOrShowError(pane, () -> ShellSession.start(config.shell(), config.envOverride(), pane,
+                pane.columns, pane.rows, workingDirectory, config.closeSignalNumber()));
+        return pane;
+    }
+
+    /**
+     * Opens a pane whose process runs {@code command} directly (via {@code /bin/sh -c}) instead of
+     * an interactive shell. The pane auto-closes when the command exits. See
+     * {@link ShellSession#startCommand}.
+     */
+    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);
+        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();
         int rows = heightPx > 0 ? metrics.rowsFor(heightPx) : config.rows();
         Terminal terminal = Ghostty.open(new TerminalOptions(columns, rows, config.maxScrollback()));
         terminal.setDeviceAttributesProvider(DeviceAttributes::xtermCompatible);
-        TerminalPane pane = new TerminalPane(terminal, metrics, config.kittyGraphics(), onContentChange, columns, rows);
+        TerminalPane pane = new TerminalPane(terminal, metrics, config.kittyGraphics(), onContentChange,
+                new GhosttyTerminalRenderer(metrics), columns, rows);
         pane.refresh();
-        pane.attach(ShellSession.start(config.shell(), config.envOverride(), pane, columns, rows));
         return pane;
     }
 
+    /** Sets the callback run when this pane's process exits on its own (see {@link #handleSessionExit}). */
+    public void setOnExit(Runnable 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 the exit handlers once, so tab/compositor
+     * mutation happens on the thread that owns the layout.
+     */
+    void handleSessionExit() {
+        Platform.runLater(() -> {
+            if (exited) {
+                return;
+            }
+            exited = true;
+            for (Runnable handler : List.copyOf(onExitHandlers)) {
+                handler.run();
+            }
+        });
+    }
+
     private void attach(ShellSession session) {
         this.session = session;
         terminal.setPtyWriter(bytes -> {
@@ -105,6 +187,19 @@ public final class TerminalPane implements AutoCloseable {
         }
     }
 
+    /**
+     * Paste text to the shell: ghostty sanitises it (stripping anything that could smuggle in
+     * control sequences) and wraps it in the bracketed-paste markers, then it goes to the pty
+     * like typed input. We always request bracketed mode — every modern shell and editor enables
+     * DECSET 2004, and the jlibghostty API does not expose querying the terminal's live mode.
+     */
+    public void paste(String text) {
+        if (text == null || text.isEmpty()) {
+            return;
+        }
+        send(Ghostty.encodePaste(text, true));
+    }
+
     public boolean sendMouse(MouseInput input, MouseEncoderSize size, boolean anyButtonPressed) {
         synchronized (terminal) {
             mouseEncoder.syncFromTerminal(terminal);
@@ -144,6 +239,7 @@ public final class TerminalPane implements AutoCloseable {
      * Snapshotting is deferred here rather than done in refresh(), so a burst of writes
      * between two frames collapses into a single snapshot.
      */
+    @Override
     public RenderStateSnapshot snapshot() {
         return takeSnapshot(false);
     }
@@ -152,6 +248,7 @@ public final class TerminalPane implements AutoCloseable {
      * Full snapshot with every row's cells populated. Used where the whole pane is redrawn
      * regardless of dirty state (the kitty-graphics path).
      */
+    @Override
     public RenderStateSnapshot snapshotFull() {
         return takeSnapshot(true);
     }
@@ -160,21 +257,13 @@ public final class TerminalPane implements AutoCloseable {
         synchronized (terminal) {
             long version = contentVersion.get();
             if (full) {
-                long updateStart = RenderProfiler.start();
                 renderState.update(terminal);
-                RenderProfiler.stop(RenderProfiler.UPDATE, updateStart);
-                long marshalStart = RenderProfiler.start();
                 cachedSnapshot = renderState.snapshot();
-                RenderProfiler.stop(RenderProfiler.MARSHAL, marshalStart);
                 renderState.resetDirty();
                 snapshotVersion = version;
             } else if (snapshotVersion != version) {
-                long updateStart = RenderProfiler.start();
                 renderState.update(terminal);
-                RenderProfiler.stop(RenderProfiler.UPDATE, updateStart);
-                long marshalStart = RenderProfiler.start();
                 cachedSnapshot = renderState.snapshotIncremental();
-                RenderProfiler.stop(RenderProfiler.MARSHAL, marshalStart);
                 renderState.resetDirty();
                 snapshotVersion = version;
             }
@@ -188,37 +277,45 @@ public final class TerminalPane implements AutoCloseable {
         }
     }
 
+    /** Best-effort current working directory of this pane's shell, or {@code null} if unknown. */
+    public String currentWorkingDirectory() {
+        ShellSession current = session;
+        return current != null ? current.currentWorkingDirectory() : null;
+    }
+
     /** This pane's own content revision, bumped on every change (see {@link #refresh()}). */
     public long contentVersion() {
         return contentVersion.get();
     }
 
-    long snapshotVersion() {
-        return snapshotVersion;
-    }
-
+    @Override
     public boolean kittyEnabled() {
         return kittyEnabled;
     }
 
+    @Override
     public Optional<KittyGraphics> kittyGraphics() {
         synchronized (terminal) {
             return terminal.kittyGraphics();
         }
     }
 
+    @Override
     public double x() {
         return x;
     }
 
+    @Override
     public double y() {
         return y;
     }
 
+    @Override
     public double width() {
         return width;
     }
 
+    @Override
     public double height() {
         return height;
     }
@@ -230,6 +327,16 @@ public final class TerminalPane implements AutoCloseable {
         this.height = height;
     }
 
+    /** Set the clip region applied on the next paints (see {@link RenderTarget#clip()}). */
+    public void setClip(Shape clip) {
+        this.clip = clip;
+    }
+
+    @Override
+    public Shape clip() {
+        return clip;
+    }
+
     /** Recompute the ghostty grid from the current bounds and the shared cell metrics. */
     public void fitToBounds() {
         int columns = metrics.columnsFor(width);
@@ -266,14 +373,57 @@ public final class TerminalPane implements AutoCloseable {
         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);
+        return snapshotVersion;
+    }
+
+    /** Repaint what changed; see {@link TerminalRenderer#paintIncremental}. */
+    public long paintIncremental(GraphicsContext gc, boolean active) {
+        renderer.paintIncremental(gc, this, active);
+        return snapshotVersion;
+    }
+
+    /**
+     * Kitty image placements from the most recent paint, in scene coordinates. The compositor
+     * renders these as overlay nodes clipped to this pane (see {@link KittyImageOverlay}).
+     */
+    public java.util.List<KittyImageNode> kittyImages() {
+        return renderer.kittyImages();
+    }
+
     @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

@@ -0,0 +1,70 @@
+package com.gregor.jprototerm;
+
+import javafx.scene.canvas.GraphicsContext;
+import javafx.scene.shape.ClosePath;
+import javafx.scene.shape.LineTo;
+import javafx.scene.shape.MoveTo;
+import javafx.scene.shape.Path;
+import javafx.scene.shape.PathElement;
+import javafx.scene.shape.Shape;
+
+/**
+ * Draws a {@link RenderTarget} onto a JavaFX canvas. The {@link Compositor} owns positioning
+ * and z-order; a renderer only fills the target's rect, clipped to the target's {@link
+ * RenderTarget#clip() clip region} so a repaint can never bleed over a pane on top.
+ * Implementations can change the look entirely — {@link GhosttyTerminalRenderer} is the real
+ * terminal renderer; a debug renderer could outline pane bounds instead.
+ *
+ * <p>A renderer may hold per-target state (e.g. a decoded-image cache), so an instance belongs
+ * to a single {@link TerminalPane}.
+ */
+abstract class TerminalRenderer {
+    /** Paint the whole target into its rect, clipped to its clip region. */
+    abstract void paintFull(GraphicsContext gc, RenderTarget target, boolean active);
+
+    /** Repaint only what changed since the last frame, clipped to the target's clip region. */
+    abstract void paintIncremental(GraphicsContext gc, RenderTarget target, boolean active);
+
+    /**
+     * The kitty image placements produced by the most recent paint, for the compositor to render
+     * as overlay nodes above the canvas. Empty unless the last paint found visible images.
+     */
+    java.util.List<KittyImageNode> kittyImages() {
+        return java.util.List.of();
+    }
+
+    /**
+     * 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() {
+    }
+
+    /**
+     * Clip to {@code region} if given (the pane's rect minus the panes covering it, computed by
+     * {@code Shape.subtract} at layout), otherwise to the plain rect. The region is a rectilinear
+     * 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) {
+        gc.beginPath();
+        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();
+        }
+    }
+}

src/main/java/com/gregor/jprototerm/X11Pointer.java

@@ -0,0 +1,66 @@
+package com.gregor.jprototerm;
+
+import java.lang.foreign.Arena;
+import java.lang.foreign.FunctionDescriptor;
+import java.lang.foreign.Linker;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.SymbolLookup;
+import java.lang.invoke.MethodHandle;
+
+import static java.lang.foreign.ValueLayout.ADDRESS;
+import static java.lang.foreign.ValueLayout.JAVA_INT;
+import static java.lang.foreign.ValueLayout.JAVA_LONG;
+
+/**
+ * Reads the X11 pointer location directly via libX11 ({@code XQueryPointer}). Unlike AWT's
+ * {@code MouseInfo}, this never calls {@code XSetErrorHandler}, so it doesn't trip GDK's
+ * "XSetErrorHandler called with a GDK error trap pushed" warning when JavaFX's GTK backend is
+ * already up. Returns {@code null} when not on X11 or libX11 can't be loaded.
+ */
+final class X11Pointer {
+    private X11Pointer() {
+    }
+
+    /** {@code {x, y}} of the pointer in X root-window (virtual screen) space, or {@code null}. */
+    static int[] query() {
+        try (Arena arena = Arena.ofConfined()) {
+            Linker linker = Linker.nativeLinker();
+            SymbolLookup x11 = SymbolLookup.libraryLookup("libX11.so.6", arena);
+            MethodHandle openDisplay = linker.downcallHandle(x11.find("XOpenDisplay").orElseThrow(),
+                    FunctionDescriptor.of(ADDRESS, ADDRESS));
+            MethodHandle defaultRootWindow = linker.downcallHandle(x11.find("XDefaultRootWindow").orElseThrow(),
+                    FunctionDescriptor.of(JAVA_LONG, ADDRESS));
+            MethodHandle queryPointer = linker.downcallHandle(x11.find("XQueryPointer").orElseThrow(),
+                    FunctionDescriptor.of(JAVA_INT, ADDRESS, JAVA_LONG,
+                            ADDRESS, ADDRESS, ADDRESS, ADDRESS, ADDRESS, ADDRESS, ADDRESS));
+            MethodHandle closeDisplay = linker.downcallHandle(x11.find("XCloseDisplay").orElseThrow(),
+                    FunctionDescriptor.of(JAVA_INT, ADDRESS));
+
+            MemorySegment display = (MemorySegment) openDisplay.invoke(MemorySegment.NULL);
+            if (display.address() == 0) {
+                return null;
+            }
+            try {
+                long root = (long) defaultRootWindow.invoke(display);
+                MemorySegment rootReturn = arena.allocate(JAVA_LONG);
+                MemorySegment childReturn = arena.allocate(JAVA_LONG);
+                MemorySegment rootX = arena.allocate(JAVA_INT);
+                MemorySegment rootY = arena.allocate(JAVA_INT);
+                MemorySegment winX = arena.allocate(JAVA_INT);
+                MemorySegment winY = arena.allocate(JAVA_INT);
+                MemorySegment mask = arena.allocate(JAVA_INT);
+                int onSameScreen = (int) queryPointer.invoke(display, root,
+                        rootReturn, childReturn, rootX, rootY, winX, winY, mask);
+                if (onSameScreen == 0) {
+                    return null;
+                }
+                return new int[] { rootX.get(JAVA_INT, 0), rootY.get(JAVA_INT, 0) };
+            } finally {
+                closeDisplay.invoke(display);
+            }
+        } catch (Throwable ignored) {
+            // Not X11, libX11 missing, or the call failed — caller falls back to the primary screen.
+            return null;
+        }
+    }
+}