diff --git a/app/pages/deep-research/index.vue b/app/pages/deep-research/index.vue
index 7a10cb82..8319c455 100644
--- a/app/pages/deep-research/index.vue
+++ b/app/pages/deep-research/index.vue
@@ -57,11 +57,19 @@ function fitBelowHeader() {
 function watchPaneForHeader(el: HTMLElement, root: ShadowRoot) {
   const cls = document.documentElement.classList
   const large = (n: HTMLElement) => n.clientHeight >= el.clientHeight / 2
+  // The scroller whose scroll hid the header.
+  let hider: HTMLElement | null = null
   const onScroll = (e: Event) => {
     const pane = e.target
     if (!(pane instanceof HTMLElement) || !large(pane)) return
-    if (pane.scrollTop > 8) cls.add('rg-header-hidden')
-    else if (pane.scrollTop <= 0) cls.remove('rg-header-hidden')
+    if (pane.scrollTop > 8) {
+      hider = pane
+      cls.add('rg-header-hidden')
+    }
+    else if (pane.scrollTop <= 0) {
+      hider = null
+      cls.remove('rg-header-hidden')
+    }
   }
   // Scroll events don't bubble, but they do pass the gallery's shadow root in the capture phase.
   root.addEventListener('scroll', onScroll, { capture: true, passive: true })
@@ -84,10 +92,29 @@ function watchPaneForHeader(el: HTMLElement, root: ShadowRoot) {
   }
   el.addEventListener('touchmove', discover, { passive: true })
   el.addEventListener('wheel', discover, { passive: true })
+  // Switching tabs hides the old tab's pane (or removes its map) without any scroll event. If
+  // that takes away the scroller that hid the header, the header comes back: a map-only tab has
+  // nothing to scroll back to the top, so it could never bring the header back itself.
+  let pending = false
+  const recheck = () => {
+    pending = false
+    if (!cls.contains('rg-header-hidden')) return
+    if (hider && hider.isConnected && hider.getClientRects().length > 0 && hider.scrollTop > 0) return
+    hider = null
+    cls.remove('rg-header-hidden')
+  }
+  const tabSwitch = new MutationObserver(() => {
+    if (!pending) {
+      pending = true
+      requestAnimationFrame(recheck)
+    }
+  })
+  tabSwitch.observe(root, { subtree: true, childList: true, attributes: true, attributeFilter: ['hidden'] })
   unwatchPane = () => {
     root.removeEventListener('scroll', onScroll, true)
     el.removeEventListener('touchmove', discover)
     el.removeEventListener('wheel', discover)
+    tabSwitch.disconnect()
   }
 }