From 202a699747474233d2b0280e2d6d94884a1f1bc7 Mon Sep 17 00:00:00 2001
From: Lawrence Chen <lawrencecchen@users.noreply.github.com>
Date: Mon, 23 Mar 2026 19:10:33 -0700
Subject: [PATCH 1/3] Add regression test for workspace insertion

---
 cmuxTests/WorkspaceUnitTests.swift | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/cmuxTests/WorkspaceUnitTests.swift b/cmuxTests/WorkspaceUnitTests.swift
index 32cd30b2..2cfedc94 100644
--- a/cmuxTests/WorkspaceUnitTests.swift
+++ b/cmuxTests/WorkspaceUnitTests.swift
@@ -334,6 +334,21 @@ final class WorkspaceCreationPlacementTests: XCTestCase {
         XCTAssertEqual(insertedIndex, baselineCount)
     }
 
+    func testAddWorkspaceAfterCurrentOverrideAppendsAfterLastSelectedWorkspace() {
+        let manager = TabManager()
+        _ = manager.tabs[0]
+        _ = manager.addWorkspace()
+        _ = manager.addWorkspace()
+        let fourth = manager.addWorkspace()
+        let baselineOrder = manager.tabs.map(\.id)
+
+        manager.selectWorkspace(fourth)
+        let inserted = manager.addWorkspace(placementOverride: .afterCurrent)
+
+        XCTAssertEqual(manager.tabs.map(\.id).filter { $0 != inserted.id }, baselineOrder)
+        XCTAssertEqual(manager.tabs.last?.id, inserted.id)
+    }
+
     private func makeManagerWithThreeWorkspaces() -> TabManager {
         let manager = TabManager()
         _ = manager.addWorkspace()

From 1c45915a867f9a6a01bc7a6ab8d5fc99572ec326 Mon Sep 17 00:00:00 2001
From: Lawrence Chen <lawrencecchen@users.noreply.github.com>
Date: Mon, 23 Mar 2026 19:10:33 -0700
Subject: [PATCH 2/3] Avoid crash in workspace insert index

---
 Sources/TabManager.swift | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/Sources/TabManager.swift b/Sources/TabManager.swift
index 96fc3349..273cc43a 100644
--- a/Sources/TabManager.swift
+++ b/Sources/TabManager.swift
@@ -2003,17 +2003,28 @@ class TabManager: ObservableObject {
         placementOverride: NewWorkspacePlacement? = nil
     ) -> Int {
         let placement = placementOverride ?? WorkspacePlacementSettings.current()
-        let pinnedCount = snapshot.tabs.filter { $0.isPinned }.count
-        let selectedIndex = snapshot.selectedTabId.flatMap { tabId in
-            snapshot.tabs.firstIndex(where: { $0.id == tabId })
+        let tabs = snapshot.tabs
+        var pinnedCount = 0
+        var selectedIndex: Int?
+        var selectedIsPinned = false
+        let selectedTabId = snapshot.selectedTabId
+
+        for (index, tab) in tabs.enumerated() {
+            if tab.isPinned {
+                pinnedCount += 1
+            }
+            if selectedIndex == nil, tab.id == selectedTabId {
+                selectedIndex = index
+                selectedIsPinned = tab.isPinned
+            }
         }
-        let selectedIsPinned = selectedIndex.map { snapshot.tabs[$0].isPinned } ?? false
+
         return WorkspacePlacementSettings.insertionIndex(
             placement: placement,
             selectedIndex: selectedIndex,
             selectedIsPinned: selectedIsPinned,
             pinnedCount: pinnedCount,
-            totalCount: snapshot.tabs.count
+            totalCount: tabs.count
         )
     }
 

From 4f5a3174e615694b081781602d5e89f0daaa145f Mon Sep 17 00:00:00 2001
From: Lawrence Chen <lawrencecchen@users.noreply.github.com>
Date: Mon, 23 Mar 2026 19:16:39 -0700
Subject: [PATCH 3/3] Clarify workspace insertion regression test

---
 cmuxTests/WorkspaceUnitTests.swift | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/cmuxTests/WorkspaceUnitTests.swift b/cmuxTests/WorkspaceUnitTests.swift
index 2cfedc94..efe4f768 100644
--- a/cmuxTests/WorkspaceUnitTests.swift
+++ b/cmuxTests/WorkspaceUnitTests.swift
@@ -336,7 +336,10 @@ final class WorkspaceCreationPlacementTests: XCTestCase {
 
     func testAddWorkspaceAfterCurrentOverrideAppendsAfterLastSelectedWorkspace() {
         let manager = TabManager()
-        _ = manager.tabs[0]
+        guard !manager.tabs.isEmpty else {
+            XCTFail("Expected TabManager to initialise with at least one workspace")
+            return
+        }
         _ = manager.addWorkspace()
         _ = manager.addWorkspace()
         let fourth = manager.addWorkspace()