diff --git a/packages/dashboard/app/components/PlanningModeModal.tsx b/packages/dashboard/app/components/PlanningModeModal.tsx
index 590ba9c29..1f9b53395 100644
--- a/packages/dashboard/app/components/PlanningModeModal.tsx
+++ b/packages/dashboard/app/components/PlanningModeModal.tsx
@@ -1519,7 +1519,6 @@ export function PlanningModeModal({ isOpen, onClose, onTaskCreated, onTasksCreat
 
   const activeLockInfo = lockSessionId ? activeTabMap.get(lockSessionId) : null;
   const activeRemoteTab = activeLockInfo && activeLockInfo.tabId !== sessionTabId;
-  const activeInAnotherTab = Boolean(activeRemoteTab && !activeLockInfo.stale);
   const allowTakeover = isLockedByOther && (!activeRemoteTab || activeLockInfo.stale);
 
   if (!isOpen) return null;
@@ -1585,11 +1584,6 @@ export function PlanningModeModal({ isOpen, onClose, onTaskCreated, onTasksCreat
           <div className="planning-detail">
           {error && <div className="form-error planning-error">{error}</div>}
           {isReconnecting && <div className="form-hint text-muted">Reconnecting…</div>}
-          {activeInAnotherTab && (
-            <div className="form-hint text-muted" data-testid="session-active-another-tab-banner">
-              Session is active in another tab.
-            </div>
-          )}
 
           {view.type === "initial" && (
             <div className="planning-initial">
diff --git a/packages/dashboard/app/components/__tests__/PlanningModeModal.planning-flow.test.tsx b/packages/dashboard/app/components/__tests__/PlanningModeModal.planning-flow.test.tsx
index 7493f870e..a7ded719e 100644
--- a/packages/dashboard/app/components/__tests__/PlanningModeModal.planning-flow.test.tsx
+++ b/packages/dashboard/app/components/__tests__/PlanningModeModal.planning-flow.test.tsx
@@ -6,6 +6,8 @@ import { TaskDetailModal } from "../TaskDetailModal";
 import { useSessionLock } from "../../hooks/useSessionLock";
 import { getSessionTabId } from "../../utils/getSessionTabId";
 import type { MergeResult } from "@fusion/core";
+const mockUseAiSessionSync = vi.fn();
+
 import {
   mockStartPlanning,
   mockStartPlanningStreaming,
@@ -99,6 +101,10 @@ vi.mock("../../hooks/useMobileKeyboard", () => ({
   useMobileKeyboard: (...args: any[]) => mockUseMobileKeyboard(...args),
 }));
 
+vi.mock("../../hooks/useAiSessionSync", () => ({
+  useAiSessionSync: (...args: any[]) => mockUseAiSessionSync(...args),
+}));
+
 describe("PlanningModeModal", () => {
   const mockOnClose = vi.fn();
   const mockOnTaskCreated = vi.fn();
@@ -147,6 +153,14 @@ describe("PlanningModeModal", () => {
     mockCancelPlanning.mockResolvedValue(undefined);
     mockUpdatePlanningSessionDraft.mockResolvedValue({ ok: true });
     mockStopPlanningGeneration.mockResolvedValue({ success: true });
+    mockUseAiSessionSync.mockReturnValue({
+      activeTabMap: new Map(),
+      broadcastUpdate: vi.fn(),
+      broadcastCompleted: vi.fn(),
+      broadcastLock: vi.fn(),
+      broadcastUnlock: vi.fn(),
+      broadcastHeartbeat: vi.fn(),
+    });
 
     // Default: simulate receiving a question after a brief delay
     mockConnectPlanningStream.mockImplementation((_sessionId: string, _projectId: string | undefined, handlers: any) => {
@@ -228,6 +242,50 @@ describe("PlanningModeModal", () => {
       });
     });
 
+    it("does not render duplicate inline lock text while takeover overlay handles lock state", async () => {
+      window.sessionStorage.setItem("fusion-tab-id", "tab-self");
+      mockAcquireSessionLock.mockResolvedValueOnce({ acquired: false, currentHolder: "tab-other" });
+      mockUseAiSessionSync.mockReturnValueOnce({
+        activeTabMap: new Map([
+          [
+            "session-123",
+            {
+              tabId: "tab-other",
+              stale: false,
+            },
+          ],
+        ]),
+        broadcastUpdate: vi.fn(),
+        broadcastCompleted: vi.fn(),
+        broadcastLock: vi.fn(),
+        broadcastUnlock: vi.fn(),
+        broadcastHeartbeat: vi.fn(),
+      });
+
+      render(
+        <PlanningModeModal
+          isOpen={true}
+          onClose={mockOnClose}
+          onTaskCreated={mockOnTaskCreated}
+          onTasksCreated={vi.fn()}
+          tasks={mockTasks}
+        />,
+      );
+
+      fireEvent.change(screen.getByPlaceholderText(/e.g., Build a user authentication/), {
+        target: { value: "Build auth system" },
+      });
+      fireEvent.click(screen.getByText("Start Planning"));
+
+      await waitFor(() => {
+        expect(screen.getByTestId("session-lock-overlay")).toBeDefined();
+      });
+
+      expect(screen.getByText("This session is active in another tab")).toBeDefined();
+      expect(screen.queryByText("Session is active in another tab.")).toBeNull();
+      expect(screen.getByRole("button", { name: "Take Control" })).toBeDefined();
+    });
+
     it("allows normal question interaction when lock is acquired", async () => {
       window.sessionStorage.setItem("fusion-tab-id", "tab-self");
 
diff --git a/packages/engine/src/merger.ts b/packages/engine/src/merger.ts
index a6f17ec7b..5a953ce72 100644
--- a/packages/engine/src/merger.ts
+++ b/packages/engine/src/merger.ts
@@ -2582,6 +2582,13 @@ export async function aiMergeTask(
 ): Promise<MergeResult> {
   throwIfAborted(options.signal, taskId);
 
+  // 1. Validate task state
+  const task = await store.getTask(taskId);
+  const mergeBlocker = getTaskMergeBlocker(task);
+  if (mergeBlocker) {
+    throw new Error(`Cannot merge ${taskId}: ${mergeBlocker}`);
+  }
+
   // Pre-merge guard against the common single-checkout setup where rootDir
   // is the developer's working tree. The merge flow below issues several
   // `git reset --hard/--merge` calls and forced checkouts that would
@@ -2591,13 +2598,6 @@ export async function aiMergeTask(
   const autostashRef = await stashUnrelatedRootDirChanges(rootDir, taskId);
   try {
 
-  // 1. Validate task state
-  const task = await store.getTask(taskId);
-  const mergeBlocker = getTaskMergeBlocker(task);
-  if (mergeBlocker) {
-    throw new Error(`Cannot merge ${taskId}: ${mergeBlocker}`);
-  }
-
   const branch = task.branch || `fusion/${taskId.toLowerCase()}`;
   const sourceIssueRef = buildSourceIssueRef(task.sourceIssue);
   const worktreePath = task.worktree;