diff --git a/tests/free-window-restored-id.spec.ts b/tests/free-window-restored-id.spec.ts
new file mode 100644
index 0000000..904ab82
--- /dev/null
+++ b/tests/free-window-restored-id.spec.ts
@@ -0,0 +1,51 @@
+// @vitest-environment jsdom
+import { beforeEach, describe, expect, it } from 'vitest'
+import { createSidebarStore, floatTab } from '../src/client/state.ts'
+
+beforeEach(() => {
+  localStorage.clear()
+})
+
+describe('restored free-window ids', () => {
+  it('seeds the shared uid counter past persisted float ids before minting another window', () => {
+    localStorage.setItem('dsh-sidebar:v1:s1', JSON.stringify({
+      panelOpen: true,
+      width: 400,
+      activePane: 'pane:1',
+      nextTerminal: 1,
+      nextBrowser: 1,
+      expanded: [],
+      splits: {
+        kind: 'leaf',
+        id: 'pane:1',
+        active: 'tab:2',
+        tabs: [{ id: 'tab:2', type: 'browser', title: 'Docked' }],
+      },
+      bottomOpen: false,
+      bottomHeight: 220,
+      bottomOpenedOnce: false,
+      bottomSplits: {
+        kind: 'leaf',
+        id: 'pane:3',
+        active: null,
+        tabs: [],
+      },
+      floats: [{
+        id: 'float:5',
+        tab: { id: 'tab:4', type: 'browser', title: 'Existing float' },
+        x: 0,
+        y: 0,
+        w: 390,
+        h: 500,
+      }],
+    }))
+
+    const store = createSidebarStore()
+    store.setSession('s1')
+    store.reduce(state => floatTab(state, 'tab:2', 400, 300))
+
+    const ids = store.getSnapshot().state!.floats.map(float => float.id)
+    expect(ids).toEqual(['float:5', 'float:6'])
+    expect(new Set(ids).size).toBe(ids.length)
+  })
+})