feat: per-project default Claude arguments

Sources/Session/SessionState.swift

@@ -36,6 +36,7 @@ struct ProjectState: Codable {
     var name: String
     var selectedTabIndex: Int
     var tabs: [ProjectTabState]
+    var defaultArgs: String?
 }
 
 struct ProjectTabState: Codable {

Sources/Window/DeckardWindowController.swift

@@ -69,6 +69,7 @@ class ProjectItem {
     var name: String  // basename of path
     var tabs: [TabItem] = []
     var selectedTabIndex: Int = 0
+    var defaultArgs: String?
 
     init(path: String) {
         self.id = UUID()
@@ -660,7 +661,7 @@ class DeckardWindowController: NSWindowController, NSSplitViewDelegate {
 
         let initialInput: String?
         if isClaude {
-            let resolvedArgs = extraArgs ?? UserDefaults.standard.string(forKey: "claudeExtraArgs") ?? ""
+            let resolvedArgs = extraArgs ?? project.defaultArgs ?? UserDefaults.standard.string(forKey: "claudeExtraArgs") ?? ""
             let extraArgsSuffix = resolvedArgs.isEmpty ? "" : " \(resolvedArgs)"
             var claudeArgs = extraArgsSuffix
             if let sessionIdToResume {
@@ -714,7 +715,7 @@ class DeckardWindowController: NSWindowController, NSSplitViewDelegate {
         let project = projects[selectedProjectIndex]
 
         if isClaude && UserDefaults.standard.bool(forKey: "promptForSessionArgs") {
-            promptForClaudeArgs { [weak self] args in
+            promptForClaudeArgs(for: project) { [weak self] args in
                 guard let self else { return }
                 guard let args else {
                     // User cancelled
@@ -746,15 +747,15 @@ class DeckardWindowController: NSWindowController, NSSplitViewDelegate {
         }
     }
 
-    private func promptForClaudeArgs(completion: @escaping (String?) -> Void) {
+    private func promptForClaudeArgs(for project: ProjectItem, 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 = ClaudeArgsField(frame: NSRect(x: 0, y: 0, width: 400, height: 60))
-        field.stringValue = UserDefaults.standard.string(forKey: "claudeExtraArgs") ?? ""
+        field.stringValue = project.defaultArgs ?? UserDefaults.standard.string(forKey: "claudeExtraArgs") ?? ""
         alert.accessoryView = field
 
         guard let window else {
@@ -1228,7 +1229,8 @@ class DeckardWindowController: NSWindowController, NSSplitViewDelegate {
                         sessionId: tab.sessionId,
                         tmuxSessionName: tab.surface.tmuxSessionName
                     )
-                }
+                },
+                defaultArgs: project.defaultArgs
             )
         }
 
@@ -1289,6 +1291,7 @@ class DeckardWindowController: NSWindowController, NSSplitViewDelegate {
         for (i, ps) in projectStates.enumerated() {
             let project = ProjectItem(path: ps.path)
             project.name = ps.name
+            project.defaultArgs = ps.defaultArgs
 
             let selTab = min(max(ps.selectedTabIndex, 0), max(ps.tabs.count - 1, 0))
 

Sources/Window/SettingsWindow.swift

@@ -116,13 +116,13 @@ class SettingsWindowController: NSWindowController, NSToolbarDelegate, NSTextFie
         let grid = NSGridView(numberOfColumns: 2, rows: 0)
         grid.translatesAutoresizingMaskIntoConstraints = false
         grid.column(at: 0).xPlacement = .trailing
-        grid.column(at: 0).width = 120
+        grid.column(at: 0).width = 175
         grid.column(at: 1).xPlacement = .fill
         grid.rowSpacing = 6
         grid.columnSpacing = 8
 
         // Extra arguments
-        let extraArgsLabel = NSTextField(labelWithString: "Extra arguments:")
+        let extraArgsLabel = NSTextField(labelWithString: "Default Claude arguments:")
         extraArgsLabel.alignment = .right
 
         let extraArgsField = ClaudeArgsField(frame: NSRect(x: 0, y: 0, width: 400, height: 60))
@@ -135,7 +135,7 @@ class SettingsWindowController: NSWindowController, NSToolbarDelegate, NSTextFie
 
         grid.addRow(with: [extraArgsLabel, extraArgsField])
 
-        let extraArgsHelp = NSTextField(labelWithString: "Arguments passed to every new Claude Code session.")
+        let extraArgsHelp = NSTextField(labelWithString: "Arguments passed to every new Claude Code session. Can be overridden per project.")
         extraArgsHelp.font = .systemFont(ofSize: 11)
         extraArgsHelp.textColor = .secondaryLabelColor
         grid.addRow(with: [NSGridCell.emptyContentView, extraArgsHelp])

Sources/Window/SidebarController.swift

@@ -584,6 +584,11 @@ extension DeckardWindowController {
         exploreItem.representedObject = project
         menu.addItem(exploreItem)
 
+        let defaultArgsItem = NSMenuItem(title: "Default Claude Arguments\u{2026}", action: #selector(defaultArgsMenuAction(_:)), keyEquivalent: "")
+        defaultArgsItem.target = self
+        defaultArgsItem.representedObject = project
+        menu.addItem(defaultArgsItem)
+
         menu.addItem(.separator())
 
         // Folder options
@@ -693,6 +698,28 @@ extension DeckardWindowController {
         objc_setAssociatedObject(explorer.window!, "explorerController", explorer, .OBJC_ASSOCIATION_RETAIN)
     }
 
+    @objc func defaultArgsMenuAction(_ sender: NSMenuItem) {
+        guard let project = sender.representedObject as? ProjectItem,
+              let window else { return }
+
+        let alert = NSAlert()
+        alert.messageText = "Default Arguments for \(project.name)"
+        alert.informativeText = "These arguments will be used for new Claude tabs in this project, overriding global defaults. Leave empty to clear."
+        alert.addButton(withTitle: "Save")
+        alert.addButton(withTitle: "Cancel")
+
+        let field = ClaudeArgsField(frame: NSRect(x: 0, y: 0, width: 400, height: 60))
+        field.stringValue = project.defaultArgs ?? ""
+        alert.accessoryView = field
+
+        alert.beginSheetModal(for: window) { [weak self] response in
+            guard response == .alertFirstButtonReturn else { return }
+            let value = field.stringValue.trimmingCharacters(in: .whitespaces)
+            project.defaultArgs = value.isEmpty ? nil : value
+            self?.saveState()
+        }
+    }
+
     // MARK: - Sidebar Selection
 
     func updateSidebarSelection() {

docs/superpowers/plans/2026-04-07-project-default-args.md

@@ -0,0 +1,261 @@
+# Project-Level Default Arguments Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Add per-project default arguments for Claude Code sessions with a three-tier resolution hierarchy (per-session dialog > project defaults > global defaults).
+
+**Architecture:** Add `defaultArgs: String?` to the runtime `ProjectItem` class and the persistence `ProjectState` struct, insert a project tier into the argument resolution chain, and expose a "Default Arguments..." context menu item on sidebar projects that opens a sheet with `ClaudeArgsField`.
+
+**Tech Stack:** Swift, AppKit (NSMenu, NSAlert, ClaudeArgsField)
+
+---
+
+### Task 1: Add `defaultArgs` to Data Models
+
+**Files:**
+- Modify: `Sources/Window/DeckardWindowController.swift:66-78` (ProjectItem class)
+- Modify: `Sources/Session/SessionState.swift:33-39` (ProjectState struct)
+
+- [ ] **Step 1: Add `defaultArgs` property to `ProjectItem`**
+
+In `Sources/Window/DeckardWindowController.swift`, add the property to the `ProjectItem` class:
+
+```swift
+class ProjectItem {
+    let id: UUID
+    var path: String
+    var name: String  // basename of path
+    var tabs: [TabItem] = []
+    var selectedTabIndex: Int = 0
+    var defaultArgs: String?
+
+    init(path: String) {
+        self.id = UUID()
+        self.path = (path as NSString).resolvingSymlinksInPath
+        self.name = (self.path as NSString).lastPathComponent
+    }
+}
+```
+
+- [ ] **Step 2: Add `defaultArgs` field to `ProjectState`**
+
+In `Sources/Session/SessionState.swift`, add the field to the `ProjectState` struct:
+
+```swift
+struct ProjectState: Codable {
+    var id: String
+    var path: String
+    var name: String
+    var selectedTabIndex: Int
+    var tabs: [ProjectTabState]
+    var defaultArgs: String?
+}
+```
+
+Since the field is `Optional` and `Codable`, existing `state.json` files without it will decode with `nil` automatically. No migration needed.
+
+- [ ] **Step 3: Build to verify compilation**
+
+Run: `xcodebuild -project Deckard.xcodeproj -scheme Deckard -configuration Debug build 2>&1 | tail -5`
+Expected: `** BUILD SUCCEEDED **`
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add Sources/Window/DeckardWindowController.swift Sources/Session/SessionState.swift
+git commit -m "feat: add defaultArgs property to ProjectItem and ProjectState"
+```
+
+---
+
+### Task 2: Update Persistence (capture + restore)
+
+**Files:**
+- Modify: `Sources/Window/DeckardWindowController.swift:1217-1233` (captureState)
+- Modify: `Sources/Window/DeckardWindowController.swift:1289-1308` (restoreOrCreateInitial)
+
+- [ ] **Step 1: Update `captureState()` to persist `defaultArgs`**
+
+In `Sources/Window/DeckardWindowController.swift`, in the `captureState()` method, add `defaultArgs` to the `ProjectState` initializer (around line 1218):
+
+```swift
+state.projects = projects.map { project in
+    ProjectState(
+        id: project.id.uuidString,
+        path: project.path,
+        name: project.name,
+        selectedTabIndex: project.selectedTabIndex,
+        tabs: project.tabs.map { tab in
+            ProjectTabState(
+                id: tab.id.uuidString,
+                name: tab.name,
+                isClaude: tab.isClaude,
+                sessionId: tab.sessionId,
+                tmuxSessionName: tab.surface.tmuxSessionName
+            )
+        },
+        defaultArgs: project.defaultArgs
+    )
+}
+```
+
+- [ ] **Step 2: Update `restoreOrCreateInitial()` to restore `defaultArgs`**
+
+In `Sources/Window/DeckardWindowController.swift`, in the restore loop (around line 1290), set `defaultArgs` after creating the `ProjectItem`:
+
+```swift
+let project = ProjectItem(path: ps.path)
+project.name = ps.name
+project.defaultArgs = ps.defaultArgs
+```
+
+- [ ] **Step 3: Build to verify compilation**
+
+Run: `xcodebuild -project Deckard.xcodeproj -scheme Deckard -configuration Debug build 2>&1 | tail -5`
+Expected: `** BUILD SUCCEEDED **`
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add Sources/Window/DeckardWindowController.swift
+git commit -m "feat: persist and restore project defaultArgs in state.json"
+```
+
+---
+
+### Task 3: Update Argument Resolution and Dialog Pre-Fill
+
+**Files:**
+- Modify: `Sources/Window/DeckardWindowController.swift:663` (resolution in createTabInProject)
+- Modify: `Sources/Window/DeckardWindowController.swift:716-734` (addTabToCurrentProject — pass project to dialog)
+- Modify: `Sources/Window/DeckardWindowController.swift:749-772` (promptForClaudeArgs — accept project defaults)
+
+- [ ] **Step 1: Update argument resolution in `createTabInProject()`**
+
+In `Sources/Window/DeckardWindowController.swift`, change line 663 from:
+
+```swift
+let resolvedArgs = extraArgs ?? UserDefaults.standard.string(forKey: "claudeExtraArgs") ?? ""
+```
+
+to:
+
+```swift
+let resolvedArgs = extraArgs ?? project.defaultArgs ?? UserDefaults.standard.string(forKey: "claudeExtraArgs") ?? ""
+```
+
+- [ ] **Step 2: Update `promptForClaudeArgs()` to accept a project parameter for pre-fill**
+
+Change the method signature and pre-fill logic:
+
+```swift
+private func promptForClaudeArgs(for project: ProjectItem, 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 = ClaudeArgsField(frame: NSRect(x: 0, y: 0, width: 400, height: 60))
+    field.stringValue = project.defaultArgs ?? UserDefaults.standard.string(forKey: "claudeExtraArgs") ?? ""
+    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)
+        }
+    }
+}
+```
+
+- [ ] **Step 3: Update the call site in `addTabToCurrentProject()` to pass the project**
+
+Change line 717 from:
+
+```swift
+promptForClaudeArgs { [weak self] args in
+```
+
+to:
+
+```swift
+promptForClaudeArgs(for: project) { [weak self] args in
+```
+
+- [ ] **Step 4: Build to verify compilation**
+
+Run: `xcodebuild -project Deckard.xcodeproj -scheme Deckard -configuration Debug build 2>&1 | tail -5`
+Expected: `** BUILD SUCCEEDED **`
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add Sources/Window/DeckardWindowController.swift
+git commit -m "feat: three-tier argument resolution with project-level defaults"
+```
+
+---
+
+### Task 4: Add Context Menu Item and Sheet
+
+**Files:**
+- Modify: `Sources/Window/SidebarController.swift:578-627` (buildProjectContextMenu)
+- Modify: `Sources/Window/SidebarController.swift` (new action method)
+
+- [ ] **Step 1: Add "Default Arguments..." menu item to `buildProjectContextMenu()`**
+
+In `Sources/Window/SidebarController.swift`, insert the new item after the "Explore Sessions" item (after line 585, before the separator on line 587):
+
+```swift
+let defaultArgsItem = NSMenuItem(title: "Default Arguments\u{2026}", action: #selector(defaultArgsMenuAction(_:)), keyEquivalent: "")
+defaultArgsItem.target = self
+defaultArgsItem.representedObject = project
+menu.addItem(defaultArgsItem)
+```
+
+- [ ] **Step 2: Add the action method that presents the sheet**
+
+Add below the `exploreSessionsMenuAction` method (after line 665 area):
+
+```swift
+@objc func defaultArgsMenuAction(_ sender: NSMenuItem) {
+    guard let project = sender.representedObject as? ProjectItem,
+          let window else { return }
+
+    let alert = NSAlert()
+    alert.messageText = "Default Arguments for \(project.name)"
+    alert.informativeText = "These arguments will be used for new Claude tabs in this project, overriding global defaults. Leave empty to clear."
+    alert.addButton(withTitle: "Save")
+    alert.addButton(withTitle: "Cancel")
+
+    let field = ClaudeArgsField(frame: NSRect(x: 0, y: 0, width: 400, height: 60))
+    field.stringValue = project.defaultArgs ?? ""
+    alert.accessoryView = field
+
+    alert.beginSheetModal(for: window) { [weak self] response in
+        guard response == .alertFirstButtonReturn else { return }
+        let value = field.stringValue.trimmingCharacters(in: .whitespaces)
+        project.defaultArgs = value.isEmpty ? nil : value
+        self?.saveState()
+    }
+}
+```
+
+- [ ] **Step 3: Build to verify compilation**
+
+Run: `xcodebuild -project Deckard.xcodeproj -scheme Deckard -configuration Debug build 2>&1 | tail -5`
+Expected: `** BUILD SUCCEEDED **`
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add Sources/Window/SidebarController.swift
+git commit -m "feat: add 'Default Arguments' context menu for projects"
+```