diff --git a/src/components/Sidebar.tsx b/src/components/Sidebar.tsx
index 865ed160..926c5546 100644
--- a/src/components/Sidebar.tsx
+++ b/src/components/Sidebar.tsx
@@ -2983,6 +2983,33 @@ function ProjectFolderView({
                 <Plus size={12} />
               </button>
             </Tooltip>
+            {inSourceRoot && isDefaultProjectFolder(folder) ? (
+              <Tooltip
+                label={sidebarText(
+                  t,
+                  "sidebar.aria.newIsolatedSessionInProjectFolder",
+                )}
+                shortcut={formatHotkey(shortcuts.newIsolatedSession)}
+                side="bottom"
+              >
+                <button
+                  type="button"
+                  aria-label={sidebarText(
+                    t,
+                    "sidebar.aria.newIsolatedSessionInProjectFolder",
+                  )}
+                  onPointerDown={(e) => e.stopPropagation()}
+                  onClick={(e) => {
+                    e.stopPropagation();
+                    onAddSession(true, "regular", "terminal");
+                  }}
+                  onKeyDown={(e) => e.stopPropagation()}
+                  className="flex size-5 items-center justify-center rounded text-fg-muted transition hover:bg-bg-elevated hover:text-fg"
+                >
+                  <GitBranch size={12} />
+                </button>
+              </Tooltip>
+            ) : null}
             <Tooltip
               label={sidebarText(
                 t,
diff --git a/src/locales/en.json b/src/locales/en.json
index d44e677f..55f3253a 100644
--- a/src/locales/en.json
+++ b/src/locales/en.json
@@ -1297,6 +1297,7 @@
       "newAutonomousGoalSession": "New Loop session",
       "newGraphSession": "New Graph session",
       "newIsolatedSessionInProject": "New worktree session in this project",
+      "newIsolatedSessionInProjectFolder": "New worktree session in this workspace",
       "newChatSessionInProject": "New chat session in this project",
       "newControlSessionInProject": "New control session in this project",
       "goalSession": "Loop session",
diff --git a/src/locales/ja.json b/src/locales/ja.json
index 9f4c5986..f2db20c0 100644
--- a/src/locales/ja.json
+++ b/src/locales/ja.json
@@ -1297,6 +1297,7 @@
       "newAutonomousGoalSession": "新しい Loop セッション",
       "newGraphSession": "新しい Graph セッション",
       "newIsolatedSessionInProject": "このプロジェクトの新しいワークツリー セッション",
+      "newIsolatedSessionInProjectFolder": "このワークスペースの新しいワークツリー セッション",
       "newChatSessionInProject": "このプロジェクトの新しいチャット セッション",
       "newControlSessionInProject": "このプロジェクトの新しいコントロール セッション",
       "goalSession": "Loop セッション",
diff --git a/src/locales/ko.json b/src/locales/ko.json
index e254fe36..af506231 100644
--- a/src/locales/ko.json
+++ b/src/locales/ko.json
@@ -1297,6 +1297,7 @@
       "newAutonomousGoalSession": "새 Loop 세션",
       "newGraphSession": "새 Graph 세션",
       "newIsolatedSessionInProject": "이 프로젝트에 새 워크트리 세션 만들기",
+      "newIsolatedSessionInProjectFolder": "이 작업공간에 새 워크트리 세션 만들기",
       "newChatSessionInProject": "이 프로젝트에 새 채팅 세션 만들기",
       "newControlSessionInProject": "이 프로젝트에 새 컨트롤 세션 만들기",
       "goalSession": "Loop 세션",
diff --git a/src/locales/zh-CN.json b/src/locales/zh-CN.json
index ed2b15f2..c278f378 100644
--- a/src/locales/zh-CN.json
+++ b/src/locales/zh-CN.json
@@ -1297,6 +1297,7 @@
       "newAutonomousGoalSession": "新建 Loop 会话",
       "newGraphSession": "新建 Graph 会话",
       "newIsolatedSessionInProject": "此项目中的新工作树会话",
+      "newIsolatedSessionInProjectFolder": "此工作区中的新工作树会话",
       "newChatSessionInProject": "此项目中的新聊天会话",
       "newControlSessionInProject": "此项目中的新控制会话",
       "goalSession": "Loop 会话",
diff --git a/tests/e2e/sidebar.spec.ts b/tests/e2e/sidebar.spec.ts
index 5a25fa19..8f2de57f 100644
--- a/tests/e2e/sidebar.spec.ts
+++ b/tests/e2e/sidebar.spec.ts
@@ -4459,6 +4459,91 @@ test.describe("sidebar: project lifecycle", () => {
     ).toContainText("demo-api");
   });
 
+  test("a source folder header creates a worktree session in that source repository", async ({
+    page,
+    tauri,
+  }) => {
+    await tauri.respond("list_projects", [
+      {
+        repo_path: "/tmp/demo",
+        name: "demo",
+        created_at: "2026-01-01T00:00:00Z",
+        position: 0,
+        source_paths: ["/tmp/acorn"],
+      },
+    ]);
+    await tauri.handle("list_sessions", () => {
+      const w = window as unknown as {
+        __sessions?: Array<Record<string, unknown>>;
+      };
+      return w.__sessions ?? [];
+    });
+    await tauri.handle("create_session", (args) => {
+      const input = args as {
+        name: string;
+        repoPath: string;
+        isolated: boolean;
+        kind: string;
+      };
+      const w = window as unknown as {
+        __createCalls?: unknown[];
+        __sessions?: Array<Record<string, unknown>>;
+      };
+      w.__createCalls = [...(w.__createCalls ?? []), args];
+      const created = {
+        id: "created-worktree-session",
+        name: input.name,
+        repo_path: input.repoPath,
+        worktree_path: `${input.repoPath}/.acorn/worktrees/${input.name}`,
+        branch: "worktree",
+        isolated: input.isolated,
+        project_scoped: true,
+        status: "ready",
+        created_at: "2026-01-01T00:00:00Z",
+        updated_at: "2026-01-01T00:00:00Z",
+        last_message: null,
+        title_source: "default",
+        kind: input.kind,
+        owner: { kind: "user" },
+        position: 0,
+        in_worktree: true,
+      };
+      w.__sessions = [...(w.__sessions ?? []), created];
+      return created;
+    });
+
+    await page.goto("/");
+
+    const sourceFolderHeader = page.locator(
+      'aside [data-sidebar-workspace-id="/tmp/acorn"]',
+    );
+    await sourceFolderHeader.hover();
+    const createWorktreeSessionButton = sourceFolderHeader.getByRole("button", {
+      name: "New worktree session in this workspace",
+    });
+    await expect(createWorktreeSessionButton).toBeVisible();
+    await createWorktreeSessionButton.click();
+
+    await expect
+      .poll(async () =>
+        page.evaluate(
+          () =>
+            (
+              window as unknown as {
+                __createCalls?: Array<Record<string, unknown>>;
+              }
+            ).__createCalls ?? [],
+        ),
+      )
+      .toEqual([
+        expect.objectContaining({
+          repoPath: "/tmp/acorn",
+          isolated: true,
+          kind: "regular",
+        }),
+      ]);
+  });
+
   test("each root's row holds the sessions started in that root", async ({
     page,
     tauri,