diff --git a/shell/components/nav/WindowManager/composables/__tests__/useDragHandler.test.ts b/shell/components/nav/WindowManager/composables/__tests__/useDragHandler.test.ts
new file mode 100644
index 00000000000..dbd2106cea1
--- /dev/null
+++ b/shell/components/nav/WindowManager/composables/__tests__/useDragHandler.test.ts
@@ -0,0 +1,282 @@
+import useDragHandler from '../useDragHandler';
+import type { Position, Tab } from '@shell/types/window-manager';
+
+const CENTER: Position = 'center';
+const LEFT: Position = 'left';
+const RIGHT: Position = 'right';
+const BOTTOM: Position = 'bottom';
+
+const mockCommit = jest.fn();
+const mockState: { wm: { lockedPositions: Position[]; userPin: Position } } = {
+  wm: {
+    lockedPositions: [],
+    userPin:         CENTER,
+  },
+};
+const mockStore = {
+  state:  mockState,
+  commit: mockCommit,
+};
+
+jest.mock('vuex', () => ({ useStore: () => mockStore }));
+
+function makeDragEvent(jsonData?: string): DragEvent {
+  return {
+    dataTransfer: {
+      setData: jest.fn(),
+      getData: jest.fn().mockReturnValue(jsonData ?? ''),
+    },
+    preventDefault: jest.fn(),
+  } as unknown as DragEvent;
+}
+
+function makeTab(id: string, position: Position): Tab {
+  return {
+    id,
+    icon:            '',
+    label:           '',
+    position,
+    layouts:         [],
+    showHeader:      false,
+    containerHeight: null,
+    containerWidth:  null,
+  };
+}
+
+describe('useDragHandler', () => {
+  let composable: ReturnType<typeof useDragHandler>;
+
+  beforeEach(() => {
+    mockCommit.mockClear();
+    mockState.wm.lockedPositions = [];
+    mockState.wm.userPin = CENTER;
+    composable = useDragHandler();
+    // Reset shared module-level refs between tests
+    composable.dragOverPositionsActive.value = false;
+    composable.pinArea.value = CENTER;
+  });
+
+  describe('initial state', () => {
+    it('dragOverPositionsActive starts as false', () => {
+      expect(composable.dragOverPositionsActive.value).toBe(false);
+    });
+
+    it('dragOverTabBarActive starts as false', () => {
+      expect(composable.dragOverTabBarActive.value).toBe(false);
+    });
+
+    it('pinArea starts as CENTER', () => {
+      expect(composable.pinArea.value).toBe(CENTER);
+    });
+  });
+
+  describe('lockedPositions', () => {
+    it('returns empty array when store has no locked positions', () => {
+      mockState.wm.lockedPositions = [];
+      const c = useDragHandler();
+
+      expect(c.lockedPositions.value).toStrictEqual([]);
+    });
+
+    it('returns locked positions from store state', () => {
+      mockState.wm.lockedPositions = [LEFT, BOTTOM];
+      const c = useDragHandler();
+
+      expect(c.lockedPositions.value).toStrictEqual([LEFT, BOTTOM]);
+    });
+  });
+
+  describe('lockedPosition', () => {
+    it('returns false when no position prop provided', () => {
+      const c = useDragHandler();
+
+      expect(c.lockedPosition.value).toBe(false);
+    });
+
+    it('returns false when position prop is not in lockedPositions', () => {
+      mockState.wm.lockedPositions = [LEFT];
+      const c = useDragHandler({ position: RIGHT });
+
+      expect(c.lockedPosition.value).toBe(false);
+    });
+
+    it('returns true when position prop is in lockedPositions', () => {
+      mockState.wm.lockedPositions = [LEFT, BOTTOM];
+      const c = useDragHandler({ position: BOTTOM });
+
+      expect(c.lockedPosition.value).toBe(true);
+    });
+  });
+
+  describe('pin computed', () => {
+    it('getter returns current store wm.userPin', () => {
+      mockState.wm.userPin = RIGHT;
+      const c = useDragHandler();
+
+      expect(c.pin.value).toBe(RIGHT);
+    });
+
+    it('setter commits wm/setUserPin when new pin is not CENTER', () => {
+      composable.pin.value = LEFT;
+      expect(mockCommit).toHaveBeenCalledWith('wm/setUserPin', LEFT);
+    });
+
+    it('setter does not commit when new pin is CENTER', () => {
+      composable.pin.value = CENTER;
+      expect(mockCommit).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('onDragPositionStart', () => {
+    it('writes tab position and id to dataTransfer as JSON', () => {
+      const event = makeDragEvent();
+      const tab = makeTab('tab-1', LEFT);
+
+      composable.onDragPositionStart({ event, tab });
+
+      expect(event.dataTransfer!.setData).toHaveBeenCalledWith(
+        'application/json',
+        JSON.stringify({ position: LEFT, tabId: 'tab-1' })
+      );
+    });
+
+    it('sets dragOverPositionsActive to true', () => {
+      composable.onDragPositionStart({ event: makeDragEvent(), tab: makeTab('t', LEFT) });
+      expect(composable.dragOverPositionsActive.value).toBe(true);
+    });
+
+    it('sets dragOverTabBarActive to true', () => {
+      composable.onDragPositionStart({ event: makeDragEvent(), tab: makeTab('t', LEFT) });
+      expect(composable.dragOverTabBarActive.value).toBe(true);
+    });
+  });
+
+  describe('onDragPositionOver', () => {
+    it('updates pinArea to the hovered position', () => {
+      composable.onDragPositionOver(makeDragEvent(), RIGHT);
+      expect(composable.pinArea.value).toBe(RIGHT);
+    });
+
+    it('calls event.preventDefault for non-CENTER positions', () => {
+      const event = makeDragEvent();
+
+      composable.onDragPositionOver(event, BOTTOM);
+      expect(event.preventDefault).toHaveBeenCalled();
+    });
+
+    it('does not call event.preventDefault for CENTER position', () => {
+      const event = makeDragEvent();
+
+      composable.onDragPositionOver(event, CENTER);
+      expect(event.preventDefault).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('onDragPositionEnd', () => {
+    it('commits wm/setUserPin with pinArea when pinArea is not CENTER', () => {
+      composable.pinArea.value = RIGHT;
+      composable.onDragPositionEnd({ event: makeDragEvent(), tab: makeTab('t', LEFT) });
+      expect(mockCommit).toHaveBeenCalledWith('wm/setUserPin', RIGHT);
+    });
+
+    it('commits wm/switchTab with tabId and pinArea when pinArea is not CENTER', () => {
+      composable.pinArea.value = BOTTOM;
+      composable.onDragPositionEnd({ event: makeDragEvent(), tab: makeTab('tab-2', LEFT) });
+      expect(mockCommit).toHaveBeenCalledWith('wm/switchTab', { tabId: 'tab-2', targetPosition: BOTTOM });
+    });
+
+    it('does not commit wm/switchTab when pinArea is CENTER', () => {
+      composable.pinArea.value = CENTER;
+      composable.onDragPositionEnd({ event: makeDragEvent(), tab: makeTab('t', LEFT) });
+      expect(mockCommit).not.toHaveBeenCalledWith('wm/switchTab', expect.anything());
+    });
+
+    it('resets dragOverPositionsActive to false', () => {
+      composable.dragOverPositionsActive.value = true;
+      composable.onDragPositionEnd({ event: makeDragEvent(), tab: makeTab('t', LEFT) });
+      expect(composable.dragOverPositionsActive.value).toBe(false);
+    });
+
+    it('resets pinArea to CENTER', () => {
+      composable.pinArea.value = LEFT;
+      composable.onDragPositionEnd({ event: makeDragEvent(), tab: makeTab('t', LEFT) });
+      expect(composable.pinArea.value).toBe(CENTER);
+    });
+  });
+
+  describe('onTabBarDragOver', () => {
+    it('sets dragOverTabBarActive to true', () => {
+      const event = makeDragEvent();
+
+      composable.onTabBarDragOver(event);
+      expect(composable.dragOverTabBarActive.value).toBe(true);
+    });
+
+    it('calls event.preventDefault', () => {
+      const event = makeDragEvent();
+
+      composable.onTabBarDragOver(event);
+      expect(event.preventDefault).toHaveBeenCalled();
+    });
+  });
+
+  describe('onTabBarDragLeave', () => {
+    it('sets dragOverTabBarActive to false', () => {
+      composable.dragOverTabBarActive.value = true;
+      composable.onTabBarDragLeave();
+      expect(composable.dragOverTabBarActive.value).toBe(false);
+    });
+  });
+
+  describe('onTabBarDrop', () => {
+    it('resets dragOverTabBarActive to false on drop', () => {
+      const c = useDragHandler({ position: RIGHT });
+
+      c.dragOverTabBarActive.value = true;
+      c.onTabBarDrop(makeDragEvent(JSON.stringify({ tabId: 'tab-x' })));
+      expect(c.dragOverTabBarActive.value).toBe(false);
+    });
+
+    it('commits wm/switchTab with tabId and the component position', () => {
+      const c = useDragHandler({ position: RIGHT });
+      const data = JSON.stringify({ tabId: 'tab-7', position: LEFT });
+
+      c.onTabBarDrop(makeDragEvent(data));
+      expect(mockCommit).toHaveBeenCalledWith('wm/switchTab', {
+        tabId:          'tab-7',
+        targetPosition: RIGHT,
+      });
+    });
+
+    it('warns when dataTransfer carries no data', () => {
+      const warnSpy = jest.spyOn(console, 'warn').mockImplementation(() => {});
+
+      composable.onTabBarDrop(makeDragEvent(''));
+      expect(warnSpy).toHaveBeenCalledWith('No data found in drag event');
+      warnSpy.mockRestore();
+    });
+
+    it('does not commit wm/switchTab when dataTransfer carries no data', () => {
+      composable.onTabBarDrop(makeDragEvent(''));
+      expect(mockCommit).not.toHaveBeenCalledWith('wm/switchTab', expect.anything());
+    });
+  });
+
+  describe('shared module-level state', () => {
+    it('dragOverPositionsActive is the same ref across composable instances', () => {
+      const c1 = useDragHandler();
+      const c2 = useDragHandler();
+
+      c1.dragOverPositionsActive.value = true;
+      expect(c2.dragOverPositionsActive.value).toBe(true);
+    });
+
+    it('pinArea is the same ref across composable instances', () => {
+      const c1 = useDragHandler();
+      const c2 = useDragHandler();
+
+      c1.pinArea.value = BOTTOM;
+      expect(c2.pinArea.value).toBe(BOTTOM);
+    });
+  });
+});