diff --git a/src/__tests__/ClaimsPage.test.tsx b/src/__tests__/ClaimsPage.test.tsx
new file mode 100644
index 0000000..81d9c1b
--- /dev/null
+++ b/src/__tests__/ClaimsPage.test.tsx
@@ -0,0 +1,56 @@
+import { fireEvent, render, screen } from '@testing-library/react';
+import ClaimsPage from '../app/claims/page';
+
+const { useWallet, useClaims } = vi.hoisted(() => ({
+  useWallet: vi.fn(),
+  useClaims: vi.fn(),
+}));
+
+vi.mock('@/hooks/useWallet', () => ({ useWallet }));
+vi.mock('@/hooks/useClaims', () => ({ useClaims }));
+vi.mock('@/components/ClaimHistoryTable', () => ({ ClaimHistoryTable: () => null }));
+vi.mock('@/components/Breadcrumb', () => ({ Breadcrumb: () => null }));
+vi.mock('@/components/ConnectWalletPrompt', () => ({ ConnectWalletPrompt: () => null }));
+vi.mock('@/lib/claimsExport', () => ({ downloadClaimsCSV: vi.fn(), downloadClaimsJSON: vi.fn() }));
+
+describe('ClaimsPage export dropdown (#546)', () => {
+  beforeEach(() => {
+    useWallet.mockReturnValue({ address: 'GWALLET', connected: true });
+    useClaims.mockReturnValue({
+      claims: [{ id: 'c1' }],
+      loading: false,
+      error: null,
+      pollingError: null,
+      refetch: vi.fn(),
+      paused: false,
+      togglePause: vi.fn(),
+      secondsUntilRefresh: null,
+      secondsSinceRefresh: null,
+    });
+  });
+
+  it('opens a viewport-constrained menu anchored left on mobile', () => {
+    render(<ClaimsPage />);
+    const trigger = screen.getByRole('button', { name: /Export/ });
+    expect(trigger.getAttribute('aria-expanded')).toBe('false');
+
+    fireEvent.click(trigger);
+
+    expect(trigger.getAttribute('aria-expanded')).toBe('true');
+    const menu = screen.getByRole('menu');
+    expect(menu.className).toContain('max-w-[calc(100vw-3rem)]');
+    expect(menu.className).toContain('left-0');
+    expect(menu.className).toContain('sm:right-0');
+    expect(screen.getAllByRole('menuitem')).toHaveLength(2);
+  });
+
+  it('closes the menu on Escape', () => {
+    render(<ClaimsPage />);
+    fireEvent.click(screen.getByRole('button', { name: /Export/ }));
+    expect(screen.queryByRole('menu')).not.toBeNull();
+
+    fireEvent.keyDown(document, { key: 'Escape' });
+
+    expect(screen.queryByRole('menu')).toBeNull();
+  });
+});
diff --git a/src/app/claims/page.tsx b/src/app/claims/page.tsx
index 7758376..cc261d3 100644
--- a/src/app/claims/page.tsx
+++ b/src/app/claims/page.tsx
@@ -1,6 +1,6 @@
 'use client';
 
-import { useState, useCallback } from 'react';
+import { useState, useCallback, useEffect } from 'react';
 import { useWallet } from '@/hooks/useWallet';
 import { useClaims } from '@/hooks/useClaims';
 import { ConnectWalletPrompt } from '@/components/ConnectWalletPrompt';
@@ -26,6 +26,15 @@ export default function ClaimsPage() {
   const [refreshing, setRefreshing] = useState(false);
   const [exportOpen, setExportOpen] = useState(false);
 
+  useEffect(() => {
+    if (!exportOpen) return;
+    const onKeyDown = (e: KeyboardEvent) => {
+      if (e.key === 'Escape') setExportOpen(false);
+    };
+    document.addEventListener('keydown', onKeyDown);
+    return () => document.removeEventListener('keydown', onKeyDown);
+  }, [exportOpen]);
+
   const handleRefresh = useCallback(async () => {
     setRefreshing(true);
     await refetch();
@@ -48,20 +57,22 @@ export default function ClaimsPage() {
   return (
     <main className="mx-auto max-w-7xl px-6 py-12">
       <Breadcrumb items={breadcrumbItems} />
-      <div className="flex items-start justify-between gap-4">
+      <div className="flex flex-col gap-4 sm:flex-row sm:items-start sm:justify-between">
         <div>
           <h1 className="text-2xl font-bold">Claim History</h1>
           <p className="mt-1 text-sm text-gray-400">
             All claims submitted from your connected wallet
           </p>
         </div>
-        <div className="flex flex-col items-end gap-1">
-          <div className="flex items-center gap-2">
+        <div className="flex flex-col items-start gap-1 sm:items-end">
+          <div className="flex flex-wrap items-center gap-2">
             {claims.length > 0 && (
               <div className="relative">
                 <button
                   onClick={() => setExportOpen((o) => !o)}
                   disabled={loading}
+                  aria-haspopup="menu"
+                  aria-expanded={exportOpen}
                   className="flex items-center gap-2 rounded-lg border border-white/10 px-4 py-2 text-xs text-gray-300 hover:border-white/20 hover:text-white disabled:opacity-60 transition-colors"
                 >
                   ↓ Export
@@ -69,14 +80,20 @@ export default function ClaimsPage() {
                 {exportOpen && (
                   <>
                     <div className="fixed inset-0 z-10" onClick={() => setExportOpen(false)} />
-                    <div className="absolute right-0 z-20 mt-1 w-40 rounded-xl border border-white/10 bg-gray-900 py-1 shadow-xl">
+                    {/* Left-anchored on mobile (the controls are left-aligned there) and
+                        capped to the viewport so it never overflows the screen edge (#546). */}
+                    <div className="absolute left-0 z-30 mt-1 w-40 max-w-[calc(100vw-3rem)] rounded-xl border border-white/10 bg-gray-900 py-1 shadow-xl sm:left-auto sm:right-0"
+                      role="menu"
+                    >
                       <button
+                        role="menuitem"
                         onClick={() => { downloadClaimsCSV(claims); setExportOpen(false); }}
                         className="w-full px-4 py-2 text-left text-xs text-gray-300 hover:bg-white/[0.05] hover:text-white transition-colors"
                       >
                         Download CSV
                       </button>
                       <button
+                        role="menuitem"
                         onClick={() => { downloadClaimsJSON(claims); setExportOpen(false); }}
                         className="w-full px-4 py-2 text-left text-xs text-gray-300 hover:bg-white/[0.05] hover:text-white transition-colors"
                       >