diff --git a/components/dashboard/PRInsights/PRInsightsClient.massive-scaling.test.tsx b/components/dashboard/PRInsights/PRInsightsClient.massive-scaling.test.tsx
new file mode 100644
index 000000000..e7b732414
--- /dev/null
+++ b/components/dashboard/PRInsights/PRInsightsClient.massive-scaling.test.tsx
@@ -0,0 +1,152 @@
+import React from 'react';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import PRInsightsClient from './PRInsightsClient';
+import type { PRInsightData } from '@/services/github/pr-insights';
+
+vi.mock('framer-motion', () => ({
+  motion: new Proxy(
+    {},
+    {
+      get:
+        (_target, tag: string) =>
+        ({ children, ...props }: React.HTMLAttributes<HTMLElement>) =>
+          React.createElement(tag, props, children),
+    }
+  ),
+}));
+
+class ResizeObserverMock {
+  observe() {}
+  unobserve() {}
+  disconnect() {}
+}
+
+function buildMassiveInsights(overrides: Partial<PRInsightData> = {}): PRInsightData {
+  return {
+    totalPRs: 999999,
+    openPRs: 333333,
+    mergedPRs: 499999,
+    closedPRs: 166667,
+    mergeRate: 49.9999,
+    avgReviewTime: 9999.99,
+    avgTimeToFirstReview: 8888.88,
+    avgCycleTime: 7777.77,
+    weeklyActivity: Array.from({ length: 1000 }, (_, i) => ({
+      name: `Week-${i}`,
+      prs: i * 100,
+    })),
+    monthlyActivity: Array.from({ length: 500 }, (_, i) => ({
+      name: `Month-${i}`,
+      prs: i * 1000,
+    })),
+    reviewsGiven: 999999,
+    reviewsReceived: 888888,
+    avgReviewResponseTime: 9999.0,
+    fastestReview: 0.001,
+    slowestReview: 99999.99,
+    repoPerformance: Array.from({ length: 500 }, (_, i) => ({
+      name: `org/repo-${i}`,
+      totalPRs: i * 1000,
+      mergeRate: (i % 100) + 0.5,
+      reviewCount: i * 500,
+      avgReviewTime: i * 2.5,
+    })),
+    highlights: {
+      fastestMerged: {
+        title: 'A'.repeat(500),
+        url: 'https://github.com/org/repo/pull/1',
+        time: 0.001,
+      },
+      mostDiscussed: {
+        title: 'B'.repeat(500),
+        url: 'https://github.com/org/repo/pull/2',
+        comments: 999999,
+      },
+      largest: {
+        title: 'C'.repeat(500),
+        url: 'https://github.com/org/repo/pull/3',
+        additions: 999999,
+        deletions: 888888,
+      },
+    },
+    ...overrides,
+  };
+}
+
+function mockFetchWith(data: PRInsightData) {
+  vi.stubGlobal(
+    'fetch',
+    vi.fn().mockResolvedValue({
+      ok: true,
+      json: async () => data,
+    })
+  );
+}
+
+describe('PRInsightsClient Massive Data Sets and Extreme High Bounds Scaling', () => {
+  beforeEach(() => {
+    vi.stubGlobal('ResizeObserver', ResizeObserverMock);
+  });
+
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it('renders all section headings without layout breakage under massive data load', async () => {
+    mockFetchWith(buildMassiveInsights());
+    render(<PRInsightsClient username="massiveuser" />);
+
+    await screen.findByRole('heading', { name: 'Activity Trends' });
+
+    expect(screen.getByRole('heading', { name: 'Activity Trends' })).toBeInTheDocument();
+    expect(screen.getByRole('heading', { name: 'Status Distribution' })).toBeInTheDocument();
+    expect(screen.getByRole('heading', { name: 'Repository Performance' })).toBeInTheDocument();
+  });
+
+  it('displays loading state before data resolves with massive dataset', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn().mockResolvedValue({
+        ok: true,
+        json: async () => buildMassiveInsights(),
+      })
+    );
+    render(<PRInsightsClient username="massiveuser" />);
+
+    expect(screen.getByText(/Crunching your pull requests/i)).toBeInTheDocument();
+
+    await screen.findByRole('heading', { name: 'Activity Trends' });
+  });
+
+  it('renders zero-PR empty state without crashing when totalPRs is 0', async () => {
+    mockFetchWith(buildMassiveInsights({ totalPRs: 0, openPRs: 0, mergedPRs: 0, closedPRs: 0 }));
+    render(<PRInsightsClient username="emptyuser" />);
+
+    await screen.findByText(/No pull request activity found/i);
+    expect(screen.getByText(/Start contributing to see your insights here/i)).toBeInTheDocument();
+  });
+
+  it('renders error state cleanly when fetch fails under high load simulation', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn().mockResolvedValue({
+        ok: false,
+        json: async () => ({}),
+      })
+    );
+    render(<PRInsightsClient username="erroruser" />);
+
+    await screen.findByText(/Error loading insights/i);
+  });
+
+  it('grid items render without breaking layout with 500 repo performance entries', async () => {
+    mockFetchWith(buildMassiveInsights());
+    render(<PRInsightsClient username="massiveuser" />);
+
+    await screen.findByRole('heading', { name: 'Repository Performance' });
+
+    const table = screen.getByRole('table');
+    expect(table).toBeInTheDocument();
+  });
+});