macos: add new tab command

macos/Ghostty.sdef

@@ -16,6 +16,9 @@
       <responds-to command="new window">
         <cocoa method="handleNewWindowScriptCommand:"/>
       </responds-to>
+      <responds-to command="new tab">
+        <cocoa method="handleNewTabScriptCommand:"/>
+      </responds-to>
       <responds-to command="new surface configuration">
         <cocoa method="handleNewSurfaceConfigurationScriptCommand:"/>
       </responds-to>
@@ -141,6 +144,16 @@
       <result type="window" description="The newly created window."/>
     </command>
 
+    <command name="new tab" code="GhstNTab" description="Create a new Ghostty tab.">
+      <parameter name="in" code="GNtW" type="window" optional="yes" description="Target window for the new tab.">
+        <cocoa key="window"/>
+      </parameter>
+      <parameter name="with configuration" code="GNtS" type="surface configuration" optional="yes" description="Base surface configuration for the initial terminal.">
+        <cocoa key="configuration"/>
+      </parameter>
+      <result type="tab" description="The newly created tab."/>
+    </command>
+
     <command name="split" code="GhstSplt" description="Split a terminal in the given direction.">
       <cocoa class="GhosttyScriptSplitCommand"/>
       <parameter name="terminal" code="GSpT" type="terminal" description="The terminal to split.">

macos/Sources/Features/AppleScript/AppDelegate+AppleScript.swift

@@ -182,6 +182,80 @@ extension NSApplication {
         // has not refreshed yet in the current run loop.
         return ScriptWindow(primaryController: controller)
     }
+
+    /// Handler for the `new tab` AppleScript command.
+    ///
+    /// Required selector name from the command in `sdef`:
+    /// `handleNewTabScriptCommand:`.
+    ///
+    /// Accepts an optional target window and optional surface configuration.
+    /// If no window is provided, this mirrors App Intents and uses the
+    /// preferred parent window.
+    ///
+    /// Returns the newly created scripting tab object.
+    @objc(handleNewTabScriptCommand:)
+    func handleNewTabScriptCommand(_ command: NSScriptCommand) -> Any? {
+        guard let appDelegate = delegate as? AppDelegate else {
+            command.scriptErrorNumber = errAEEventFailed
+            command.scriptErrorString = "Ghostty app delegate is unavailable."
+            return nil
+        }
+
+        let baseConfig: Ghostty.SurfaceConfiguration
+        do {
+            if let scriptRecord = command.evaluatedArguments?["configuration"] as? NSDictionary {
+                baseConfig = try Ghostty.SurfaceConfiguration(scriptRecord: scriptRecord)
+            } else {
+                baseConfig = Ghostty.SurfaceConfiguration()
+            }
+        } catch {
+            command.scriptErrorNumber = errAECoercionFail
+            command.scriptErrorString = error.localizedDescription
+            return nil
+        }
+
+        let targetWindow = command.evaluatedArguments?["window"] as? ScriptWindow
+        let parentWindow: NSWindow?
+        if let targetWindow {
+            guard let resolvedWindow = targetWindow.preferredParentWindow else {
+                command.scriptErrorNumber = errAEEventFailed
+                command.scriptErrorString = "Target window is no longer available."
+                return nil
+            }
+
+            parentWindow = resolvedWindow
+        } else {
+            parentWindow = TerminalController.preferredParent?.window
+        }
+
+        guard let createdController = TerminalController.newTab(
+            appDelegate.ghostty,
+            from: parentWindow,
+            withBaseConfig: baseConfig
+        ) else {
+            command.scriptErrorNumber = errAEEventFailed
+            command.scriptErrorString = "Failed to create tab."
+            return nil
+        }
+
+        let createdTabID = ScriptTab.stableID(controller: createdController)
+
+        if let targetWindow,
+           let scriptTab = targetWindow.valueInTabs(uniqueID: createdTabID) {
+            return scriptTab
+        }
+
+        for scriptWindow in scriptWindows {
+            if let scriptTab = scriptWindow.valueInTabs(uniqueID: createdTabID) {
+                return scriptTab
+            }
+        }
+
+        // Fall back to wrapping the created controller if AppKit tab-group
+        // bookkeeping has not fully refreshed in the current run loop.
+        let fallbackWindow = ScriptWindow(primaryController: createdController)
+        return ScriptTab(window: fallbackWindow, controller: createdController)
+    }
 }
 
 // MARK: - Private Helpers

macos/Sources/Features/AppleScript/ScriptSurfaceConfiguration.swift

@@ -9,6 +9,10 @@ extension Ghostty.SurfaceConfiguration: ScriptRecord {
     init(scriptRecord source: NSDictionary?) throws {
         self.init()
 
+        guard let source else {
+            return
+        }
+
         guard let raw = source as? [String: Any] else {
             throw RecordParseError.invalidType(parameter: "configuration", expected: "a surface configuration record")
         }

macos/Sources/Features/AppleScript/ScriptWindow.swift

@@ -111,6 +111,11 @@ final class ScriptWindow: NSObject {
         selectedController === controller
     }
 
+    /// Best-effort native window to use as a tab parent for AppleScript commands.
+    var preferredParentWindow: NSWindow? {
+        selectedController?.window ?? controllers.first?.window
+    }
+
     /// Resolves a previously generated tab ID back to a live controller.
     private func controller(tabID: String) -> BaseTerminalController? {
         controllers.first(where: { ScriptTab.stableID(controller: $0) == tabID })