diff --git a/components/search/__tests__/filter-panel-host.test.tsx b/components/search/__tests__/filter-panel-host.test.tsx
index 4ccc6ad1c..375ce474d 100644
--- a/components/search/__tests__/filter-panel-host.test.tsx
+++ b/components/search/__tests__/filter-panel-host.test.tsx
@@ -1,6 +1,6 @@
 import { render, screen } from '@testing-library/react';
 import { describe, it, expect } from 'vitest';
-import { FilterPanelHost } from '../filter-panel-host';
+import { FilterPanelHost, filterPanelBox } from '../filter-panel-host';
 
 // Mountain View moves the filter button into the global top bar. The panel
 // follows it there, given an anchor; without one it stays in the flow of the
@@ -36,6 +36,17 @@ describe('FilterPanelHost', () => {
     anchor.remove();
   });
 
+  it('stays wide enough for its fields when the search field is narrow', () => {
+    // The field is 286px wide at 1024: a panel that size cut the date fields to "dd".
+    expect(filterPanelBox({ left: 165, right: 451, bottom: 56, width: 286 }, 1024, false)).toEqual({ top: 60, left: 165, width: 480 });
+  });
+
+  it('grows towards the trailing side in RTL and stays on screen', () => {
+    expect(filterPanelBox({ left: 573, right: 859, bottom: 56, width: 286 }, 1024, true)).toEqual({ top: 60, left: 379, width: 480 });
+    expect(filterPanelBox({ left: 700, right: 986, bottom: 56, width: 286 }, 1024, false).left).toBe(536);
+    expect(filterPanelBox({ left: 20, right: 300, bottom: 56, width: 280 }, 400, false)).toEqual({ top: 60, left: 8, width: 384 });
+  });
+
   it('draws it at the end of <body>, above the sidebar column and not inside the top bar', () => {
     const anchor = document.createElement('div');
     document.body.appendChild(anchor);
diff --git a/components/search/filter-panel-host.tsx b/components/search/filter-panel-host.tsx
index 10dbb137e..e4feeb2fd 100644
--- a/components/search/filter-panel-host.tsx
+++ b/components/search/filter-panel-host.tsx
@@ -52,6 +52,26 @@ export function FilterPanelHost({
   );
 }
 
+/** Below this the form's labelled rows leave its date and size fields a few characters wide. */
+const MIN_PANEL_WIDTH = 480;
+const VIEWPORT_MARGIN = 8;
+
+/**
+ * Where the panel goes for a given search field: under it, sharing its leading
+ * edge and width. The field shrinks with the window, so a narrow one gets a
+ * panel wider than itself, growing towards the trailing side and kept on screen.
+ */
+export function filterPanelBox(
+  rect: { left: number; right: number; bottom: number; width: number },
+  viewportWidth: number,
+  rtl: boolean,
+): CSSProperties {
+  const width = Math.max(rect.width, Math.min(MIN_PANEL_WIDTH, viewportWidth - VIEWPORT_MARGIN * 2));
+  const preferred = rtl ? rect.right - width : rect.left;
+  const left = Math.max(VIEWPORT_MARGIN, Math.min(preferred, viewportWidth - width - VIEWPORT_MARGIN));
+  return { top: rect.bottom + 4, left, width };
+}
+
 /** The anchor's leading edge, width and bottom, kept current as the bar resizes. */
 function useAnchorBox(anchor: HTMLElement | null): CSSProperties | null {
   const [box, setBox] = useState<CSSProperties | null>(null);
@@ -62,8 +82,7 @@ function useAnchorBox(anchor: HTMLElement | null): CSSProperties | null {
       return;
     }
     const measure = () => {
-      const rect = anchor.getBoundingClientRect();
-      setBox({ top: rect.bottom + 4, left: rect.left, width: rect.width });
+      setBox(filterPanelBox(anchor.getBoundingClientRect(), window.innerWidth, getComputedStyle(anchor).direction === "rtl"));
     };
     measure();