feat: add per-session Claude Code argument customization

wonderchook · claude · gi11es · commit 40702e781bb5 · 2026-03-30T10:25:45.000+02:00
Allow users to customize CLI arguments per Claude session via a dialog
prompt. Adds a "Customize arguments per session" toggle in Settings that,
when enabled, shows an NSAlert before creating each Claude tab. The dialog
pre-fills with the global extra args and lets users override them for that
specific session.

Includes extracted finalizeTabCreation helper to deduplicate post-creation
code and a stale-project guard in the async completion path.

Co-Authored-By: Claude Opus 4.6 (1M context) &lt;noreply@anthropic.com&gt;
diff --git a/Sources/Window/DeckardWindowController.swift b/Sources/Window/DeckardWindowController.swift
@@ -585,7 +585,7 @@ class DeckardWindowController: NSWindowController, NSSplitViewDelegate {
 
     // MARK: - Tab Management (within a project)
 
-    func createTabInProject(_ project: ProjectItem, isClaude: Bool, name: String? = nil, sessionIdToResume: String? = nil, tmuxSessionToResume: String? = nil) {
+    func createTabInProject(_ project: ProjectItem, isClaude: Bool, name: String? = nil, sessionIdToResume: String? = nil, tmuxSessionToResume: String? = nil, extraArgs: String? = nil) {
         let surface = TerminalSurface()
         let tabName: String
         if let name = name {
@@ -614,8 +614,8 @@ class DeckardWindowController: NSWindowController, NSSplitViewDelegate {
 
         let initialInput: String?
         if isClaude {
-            let extraArgs = UserDefaults.standard.string(forKey: "claudeExtraArgs") ?? ""
-            let extraArgsSuffix = extraArgs.isEmpty ? "" : " \(extraArgs)"
+            let resolvedArgs = extraArgs ?? UserDefaults.standard.string(forKey: "claudeExtraArgs") ?? ""
+            let extraArgsSuffix = resolvedArgs.isEmpty ? "" : " \(resolvedArgs)"
             var claudeArgs = extraArgsSuffix
             if let sessionIdToResume {
                 let encoded = project.path.claudeProjectDirName
@@ -665,7 +665,29 @@ class DeckardWindowController: NSWindowController, NSSplitViewDelegate {
             return
         }
         let project = projects[selectedProjectIndex]
-        createTabInProject(project, isClaude: isClaude)
+
+        if isClaude && UserDefaults.standard.bool(forKey: "promptForSessionArgs") {
+            promptForClaudeArgs { [weak self] args in
+                guard let self else { return }
+                guard let args else {
+                    // User cancelled
+                    self.isCreatingTab = false
+                    return
+                }
+                guard self.projects.contains(where: { $0 === project }) else {
+                    self.isCreatingTab = false
+                    return
+                }
+                self.createTabInProject(project, isClaude: true, extraArgs: args)
+                self.finalizeTabCreation(in: project)
+            }
+        } else {
+            createTabInProject(project, isClaude: isClaude)
+            finalizeTabCreation(in: project)
+        }
+    }
+
+    private func finalizeTabCreation(in project: ProjectItem) {
         project.selectedTabIndex = project.tabs.count - 1
         rebuildTabBar()
         rebuildSidebar()
@@ -677,6 +699,33 @@ class DeckardWindowController: NSWindowController, NSSplitViewDelegate {
         }
     }
 
+    private func promptForClaudeArgs(completion: @escaping (String?) -> Void) {
+        let alert = NSAlert()
+        alert.messageText = "Claude Code Arguments"
+        alert.informativeText = "Arguments passed to this session:"
+        alert.addButton(withTitle: "Start")
+        alert.addButton(withTitle: "Cancel")
+
+        let field = NSTextField(frame: NSRect(x: 0, y: 0, width: 300, height: 24))
+        field.font = .monospacedSystemFont(ofSize: 12, weight: .regular)
+        field.stringValue = UserDefaults.standard.string(forKey: "claudeExtraArgs") ?? ""
+        field.placeholderString = "--permission-mode auto"
+        alert.accessoryView = field
+
+        guard let window else {
+            completion(nil)
+            return
+        }
+
+        alert.beginSheetModal(for: window) { response in
+            if response == .alertFirstButtonReturn {
+                completion(field.stringValue)
+            } else {
+                completion(nil)
+            }
+        }
+    }
+
     func closeCurrentTab() {
         guard let project = currentProject else { return }
         let idx = project.selectedTabIndex
diff --git a/Sources/Window/SettingsWindow.swift b/Sources/Window/SettingsWindow.swift
@@ -140,6 +140,16 @@ class SettingsWindowController: NSWindowController, NSToolbarDelegate, NSTextFie
         extraArgsHelp.textColor = .secondaryLabelColor
         grid.addRow(with: [NSGridCell.emptyContentView, extraArgsHelp])
 
+        // Per-session args checkbox
+        let perSessionCheck = NSButton(checkboxWithTitle: "Customize arguments per session", target: self, action: #selector(perSessionArgsToggled(_:)))
+        perSessionCheck.state = UserDefaults.standard.bool(forKey: "promptForSessionArgs") ? .on : .off
+        grid.addRow(with: [NSGridCell.emptyContentView, perSessionCheck])
+
+        let perSessionHelp = NSTextField(labelWithString: "Show a dialog to set arguments when creating a new Claude tab.")
+        perSessionHelp.font = .systemFont(ofSize: 11)
+        perSessionHelp.textColor = .secondaryLabelColor
+        grid.addRow(with: [NSGridCell.emptyContentView, perSessionHelp])
+
         // Spacer
         let spacer = NSView()
         spacer.translatesAutoresizingMaskIntoConstraints = false
@@ -180,6 +190,10 @@ class SettingsWindowController: NSWindowController, NSToolbarDelegate, NSTextFie
         return pane
     }
 
+    @objc private func perSessionArgsToggled(_ sender: NSButton) {
+        UserDefaults.standard.set(sender.state == .on, forKey: "promptForSessionArgs")
+    }
+
     @objc private func vibrancyToggled(_ sender: NSButton) {
         let enabled = sender.state == .on
         UserDefaults.standard.set(enabled, forKey: "sidebarVibrancy")
