diff --git a/frontend/src/__tests__/components/AdvancedFilterModal.test.tsx b/frontend/src/__tests__/components/AdvancedFilterModal.test.tsx
new file mode 100644
index 0000000..f85f92f
--- /dev/null
+++ b/frontend/src/__tests__/components/AdvancedFilterModal.test.tsx
@@ -0,0 +1,56 @@
+import React from 'react';
+import { cleanup, fireEvent, render, screen } from '@testing-library/react';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import AdvancedFilterModal, { MAX_RENDERED_OPTIONS } from '@/components/AdvancedFilterModal';
+
+vi.mock('@/lib/motion', () => ({
+  motion: {
+    div: ({ children, ...props }: React.ComponentProps<'div'> & Record<string, unknown>) => {
+      const rest = { ...props };
+      for (const key of ['initial', 'animate', 'exit', 'transition']) delete rest[key];
+      return <div {...(rest as React.ComponentProps<'div'>)}>{children}</div>;
+    },
+  },
+  AnimatePresence: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+}));
+
+const names = Array.from({ length: 1000 }, (_, i) => `VESSEL ${String(i).padStart(4, '0')}`);
+
+function renderModal() {
+  return render(
+    <AdvancedFilterModal
+      title="MARITIME VESSELS"
+      icon={null}
+      accentColor="#3B82F6"
+      accentColorName="blue"
+      fields={[{ key: 'ship_name', label: 'VESSEL NAME', options: names }]}
+      activeFilters={{}}
+      onApply={vi.fn()}
+      onClose={vi.fn()}
+    />,
+  );
+}
+
+describe('AdvancedFilterModal large option lists', () => {
+  afterEach(() => cleanup());
+
+  it('mounts only the head of a long list and says how much is hidden', () => {
+    renderModal();
+    const rows = screen.getAllByRole('button').filter((b) => b.textContent?.startsWith('VESSEL '));
+    expect(rows).toHaveLength(MAX_RENDERED_OPTIONS);
+    expect(screen.getByText('1000 AVAILABLE')).toBeTruthy();
+    expect(screen.getByText(/SHOWING 300 OF 1,000/)).toBeTruthy();
+  });
+
+  it('renders the whole list once the search narrows it', () => {
+    renderModal();
+    fireEvent.change(screen.getByPlaceholderText(/Search vessel name/i), {
+      target: { value: 'VESSEL 09' },
+    });
+    const rows = screen.getAllByRole('button').filter((b) => b.textContent?.startsWith('VESSEL '));
+    expect(rows).toHaveLength(100);
+    expect(screen.queryByText(/SHOWING/)).toBeNull();
+    expect(screen.getByText('100 AVAILABLE')).toBeTruthy();
+  });
+});
diff --git a/frontend/src/components/AdvancedFilterModal.tsx b/frontend/src/components/AdvancedFilterModal.tsx
index ab20265..39f99df 100644
--- a/frontend/src/components/AdvancedFilterModal.tsx
+++ b/frontend/src/components/AdvancedFilterModal.tsx
@@ -1,6 +1,6 @@
 'use client';
 
-import { useState, useMemo, useRef, useCallback, useEffect } from 'react';
+import { useState, useMemo, useRef, useCallback, useEffect, useLayoutEffect } from 'react';
 import { motion } from '@/lib/motion';
 import { Search, X, Check, GripHorizontal } from 'lucide-react';
 
@@ -11,6 +11,11 @@ interface FilterField {
   optionLabels?: Record<string, string>;
 }
 
+// Option lists come straight from live data (vessel names run to tens of
+// thousands); rendering every row as a button makes the dialog take seconds
+// to open, so only the head of the list is mounted until the search narrows it.
+export const MAX_RENDERED_OPTIONS = 300;
+
 interface AdvancedFilterModalProps {
   title: string;
   icon: React.ReactNode;
@@ -55,8 +60,8 @@ export default function AdvancedFilterModal({
   const dragStartRef = useRef({ x: 0, y: 0, posX: 0, posY: 0 });
   const modalRef = useRef<HTMLDivElement>(null);
 
-  // Center on mount, clamped so it doesn't overlap the bottom status bar (~48px)
-  useEffect(() => {
+  // Center before first paint, clamped so it doesn't overlap the bottom status bar (~48px)
+  useLayoutEffect(() => {
     if (modalRef.current) {
       const rect = modalRef.current.getBoundingClientRect();
       const pad = 52; // status bar + small gap
@@ -154,6 +159,12 @@ export default function AdvancedFilterModal({
     });
   }, [activeField, activeTab, searchTerms]);
 
+  const visibleOptions = useMemo(
+    () => filteredOptions.slice(0, MAX_RENDERED_OPTIONS),
+    [filteredOptions],
+  );
+  const hiddenCount = filteredOptions.length - visibleOptions.length;
+
   // Tailwind color map for dynamic classes
   const colorMap: Record<
     string,
@@ -355,7 +366,7 @@ export default function AdvancedFilterModal({
               </div>
             ) : (
               <div className="flex flex-col gap-px">
-                {filteredOptions.map((option) => {
+                {visibleOptions.map((option) => {
                   const isChecked = draft[activeTab]?.has(option);
                   return (
                     <button
@@ -383,6 +394,12 @@ export default function AdvancedFilterModal({
                     </button>
                   );
                 })}
+                {hiddenCount > 0 && (
+                  <div className="text-center py-3 text-[var(--text-muted)] text-[10px] tracking-widest">
+                    SHOWING {visibleOptions.length.toLocaleString()} OF{' '}
+                    {filteredOptions.length.toLocaleString()} — SEARCH TO NARROW
+                  </div>
+                )}
               </div>
             )}
           </div>