diff --git a/LilAgents/DockVisibility.swift b/LilAgents/DockVisibility.swift
index 05de766..291ca36 100644
--- a/LilAgents/DockVisibility.swift
+++ b/LilAgents/DockVisibility.swift
@@ -1,6 +1,27 @@
+import AppKit
 import CoreGraphics
+import Foundation
+
+enum AppPreferences {
+    static let showOnAllDesktopsKey = "showOnAllDesktops"
+
+    static var showOnAllDesktops: Bool {
+        get {
+            UserDefaults.standard.bool(forKey: showOnAllDesktopsKey)
+        }
+        set {
+            UserDefaults.standard.set(newValue, forKey: showOnAllDesktopsKey)
+        }
+    }
+}
 
 enum DockVisibility {
+    static func collectionBehavior(showOnAllDesktops: Bool = AppPreferences.showOnAllDesktops) -> NSWindow.CollectionBehavior {
+        showOnAllDesktops
+            ? [.canJoinAllSpaces, .fullScreenAuxiliary, .stationary]
+            : [.moveToActiveSpace, .stationary]
+    }
+
     static func screenHasVisibleDockReservedArea(
         screenFrame: CGRect,
         visibleFrame: CGRect
diff --git a/LilAgents/LilAgentsApp.swift b/LilAgents/LilAgentsApp.swift
index 42f2dbd..a813422 100644
--- a/LilAgents/LilAgentsApp.swift
+++ b/LilAgents/LilAgentsApp.swift
@@ -96,11 +96,14 @@ class AppDelegate: NSObject, NSApplicationDelegate {
         let displayItem = NSMenuItem(title: "Display", action: nil, keyEquivalent: "")
         let displayMenu = NSMenu()
         displayMenu.delegate = self
+        let allDesktopsItem = NSMenuItem(title: "Show on All Desktops", action: #selector(toggleShowOnAllDesktops(_:)), keyEquivalent: "")
+        allDesktopsItem.state = AppPreferences.showOnAllDesktops ? .on : .off
+        displayMenu.addItem(allDesktopsItem)
+        displayMenu.addItem(NSMenuItem.separator())
         let autoItem = NSMenuItem(title: "Auto (Main Display)", action: #selector(switchDisplay(_:)), keyEquivalent: "")
         autoItem.tag = -1
         autoItem.state = .on
         displayMenu.addItem(autoItem)
-        displayMenu.addItem(NSMenuItem.separator())
         for (i, screen) in NSScreen.screens.enumerated() {
             let name = screen.localizedName
             let item = NSMenuItem(title: name, action: #selector(switchDisplay(_:)), keyEquivalent: "")
@@ -210,6 +213,13 @@ class AppDelegate: NSObject, NSApplicationDelegate {
         }
     }
 
+    @objc func toggleShowOnAllDesktops(_ sender: NSMenuItem) {
+        let enabled = !AppPreferences.showOnAllDesktops
+        AppPreferences.showOnAllDesktops = enabled
+        sender.state = enabled ? .on : .off
+        syncWindowCollectionBehaviors()
+    }
+
     @objc func toggleChar1(_ sender: NSMenuItem) {
         guard let chars = controller?.characters, chars.count > 0 else { return }
         let char = chars[0]
@@ -242,6 +252,16 @@ class AppDelegate: NSObject, NSApplicationDelegate {
     @objc func quitApp() {
         NSApp.terminate(nil)
     }
+
+    private func syncWindowCollectionBehaviors() {
+        let behavior = DockVisibility.collectionBehavior()
+
+        controller?.characters.forEach { character in
+            character.window.collectionBehavior = behavior
+            character.popoverWindow?.collectionBehavior = behavior
+            character.thinkingBubbleWindow?.collectionBehavior = behavior
+        }
+    }
 }
 
 extension AppDelegate: NSMenuDelegate {}
diff --git a/LilAgents/LilAgentsController.swift b/LilAgents/LilAgentsController.swift
index ec6fce9..03a263e 100644
--- a/LilAgents/LilAgentsController.swift
+++ b/LilAgents/LilAgentsController.swift
@@ -184,6 +184,10 @@ class LilAgentsController {
     }
 
     private func shouldShowCharacters(on screen: NSScreen) -> Bool {
+        if AppPreferences.showOnAllDesktops {
+            return true
+        }
+
         // User explicitly pinned to this screen — always show
         if pinnedScreenIndex >= 0, pinnedScreenIndex < NSScreen.screens.count {
             return true
diff --git a/LilAgents/WalkerCharacter.swift b/LilAgents/WalkerCharacter.swift
index fa30824..357712c 100644
--- a/LilAgents/WalkerCharacter.swift
+++ b/LilAgents/WalkerCharacter.swift
@@ -160,7 +160,7 @@ class WalkerCharacter {
         window.hasShadow = false
         window.level = .statusBar
         window.ignoresMouseEvents = false
-        window.collectionBehavior = [.moveToActiveSpace, .stationary]
+        window.collectionBehavior = windowCollectionBehavior
 
         let hostView = CharacterContentView(frame: CGRect(x: 0, y: 0, width: displayWidth, height: displayHeight))
         hostView.character = self
@@ -405,6 +405,10 @@ class WalkerCharacter {
         (themeOverride ?? PopoverTheme.current).withCharacterColor(characterColor).withCustomFont()
     }
 
+    private var windowCollectionBehavior: NSWindow.CollectionBehavior {
+        DockVisibility.collectionBehavior()
+    }
+
     func createPopoverWindow() {
         let t = resolvedTheme
         let popoverWidth: CGFloat = 420
@@ -420,7 +424,7 @@ class WalkerCharacter {
         win.backgroundColor = .clear
         win.hasShadow = true
         win.level = NSWindow.Level(rawValue: NSWindow.Level.statusBar.rawValue + 10)
-        win.collectionBehavior = [.moveToActiveSpace, .stationary]
+        win.collectionBehavior = windowCollectionBehavior
         let brightness = t.popoverBg.redComponent * 0.299 + t.popoverBg.greenComponent * 0.587 + t.popoverBg.blueComponent * 0.114
         win.appearance = NSAppearance(named: brightness < 0.5 ? .darkAqua : .aqua)
 
@@ -792,7 +796,7 @@ class WalkerCharacter {
         win.hasShadow = true
         win.level = NSWindow.Level(rawValue: NSWindow.Level.statusBar.rawValue + 5)
         win.ignoresMouseEvents = true
-        win.collectionBehavior = [.moveToActiveSpace, .stationary]
+        win.collectionBehavior = windowCollectionBehavior
 
         let container = NSView(frame: NSRect(x: 0, y: 0, width: w, height: h))
         container.wantsLayer = true
diff --git a/Tests/AppPreferencesTests.swift b/Tests/AppPreferencesTests.swift
new file mode 100644
index 0000000..c7e1cc3
--- /dev/null
+++ b/Tests/AppPreferencesTests.swift
@@ -0,0 +1,22 @@
+import Foundation
+
+func runAppPreferencesTests() {
+    let defaults = UserDefaults.standard
+    let key = AppPreferences.showOnAllDesktopsKey
+    let originalValue = defaults.object(forKey: key)
+
+    defer {
+        defaults.removeObject(forKey: key)
+        if let originalValue {
+            defaults.set(originalValue, forKey: key)
+        }
+    }
+
+    defaults.removeObject(forKey: key)
+    expect(AppPreferences.showOnAllDesktops == false, "show on all desktops defaults to off")
+
+    AppPreferences.showOnAllDesktops = true
+    expect(defaults.bool(forKey: key) == true, "show on all desktops persists on")
+
+    print("AppPreferences tests passed")
+}
diff --git a/Tests/DockVisibilityTests.swift b/Tests/DockVisibilityTests.swift
index 52a22ea..612fe82 100644
--- a/Tests/DockVisibilityTests.swift
+++ b/Tests/DockVisibilityTests.swift
@@ -1,16 +1,8 @@
 import Foundation
 import CoreGraphics
+import AppKit
 
 func runDockVisibilityTests() {
-    func expect(
-        _ condition: @autoclosure () -> Bool,
-        _ message: String
-    ) {
-        if !condition() {
-            fputs("FAIL: \(message)\n", stderr)
-            exit(1)
-        }
-    }
 
     let screenFrame = CGRect(x: 0, y: 0, width: 1440, height: 900)
 
@@ -74,5 +66,15 @@ func runDockVisibilityTests() {
         "keeps characters hidden on non-main screens when only the menu bar is visible"
     )
 
+    expect(
+        DockVisibility.collectionBehavior(showOnAllDesktops: false) == [.moveToActiveSpace, .stationary],
+        "uses active-space behavior when show on all desktops is off"
+    )
+
+    expect(
+        DockVisibility.collectionBehavior(showOnAllDesktops: true) == [.canJoinAllSpaces, .fullScreenAuxiliary, .stationary],
+        "uses all-spaces behavior when show on all desktops is on"
+    )
+
     print("DockVisibility tests passed")
 }
diff --git a/Tests/main.swift b/Tests/main.swift
index 5a0c1d4..fbcdc88 100644
--- a/Tests/main.swift
+++ b/Tests/main.swift
@@ -1 +1,11 @@
+import Foundation
+
+func expect(_ condition: @autoclosure () -> Bool, _ message: String) {
+    if !condition() {
+        fputs("FAIL: \(message)\n", stderr)
+        exit(1)
+    }
+}
+
 runDockVisibilityTests()
+runAppPreferencesTests()