diff --git a/src/web/public/tile-grid.js b/src/web/public/tile-grid.js
index e78193f0..d95c6b27 100644
--- a/src/web/public/tile-grid.js
+++ b/src/web/public/tile-grid.js
@@ -2980,7 +2980,10 @@ Object.assign(CodemanApp.prototype, {
     place(sessionId);
     if (!grid.has(sessionId)) return false;
     (this._tileDockedAt ||= new Map()).set(sessionId, Date.now());
-    if (poppedOut) this._postWindowMessage?.({ type: 'close-request', id: sessionId });
+    // Asked unconditionally: a pop-out this window never heard of (opened from
+    // another dashboard) closes too. Dashboards ignore it; only that id's
+    // pop-out reacts.
+    this._postWindowMessage?.({ type: 'close-request', id: sessionId });
     this._postWindowMessage?.({ type: 'tile-adopted', id: sessionId, by: this._wsTabNonce });
     return true;
   },
diff --git a/test/tile-grid-detach.test.ts b/test/tile-grid-detach.test.ts
index d3b983c9..40c2265a 100644
--- a/test/tile-grid-detach.test.ts
+++ b/test/tile-grid-detach.test.ts
@@ -387,6 +387,14 @@ describe('a tile from another window dropped here', () => {
     expect(app._tileGrid.ids).toContain('s-other');
   });
 
+  it("asks the session's pop-out to close even when this window did not know of one", () => {
+    // Popped out from another dashboard: this window's detachedSessions never had it.
+    const app = openGrid(THREE);
+    tileEl('s-c').dispatch('drop', foreign('s-other'));
+    expect(app._tileGrid.ids).toContain('s-other');
+    expect(app._postWindowMessage).toHaveBeenCalledWith({ type: 'close-request', id: 's-other' });
+  });
+
   it('an id this page does not know docks nowhere', () => {
     const app = openGrid(THREE);
     tileEl('s-b').dispatch('drop', foreign('s-gone'));