diff --git a/app/api/pr-insights/route.theme-contrast.test.ts b/app/api/pr-insights/route.theme-contrast.test.ts
new file mode 100644
index 000000000..bb3277d6c
--- /dev/null
+++ b/app/api/pr-insights/route.theme-contrast.test.ts
@@ -0,0 +1,119 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { GET } from './route';
+
+vi.mock('@/services/github/pr-insights', () => ({
+  fetchPRInsights: vi.fn(),
+}));
+
+import { fetchPRInsights } from '@/services/github/pr-insights';
+import type { PRInsightData } from '@/services/github/pr-insights';
+
+const mockInsights: PRInsightData = {
+  totalPRs: 20,
+  openPRs: 5,
+  mergedPRs: 12,
+  closedPRs: 3,
+  mergeRate: 60,
+  avgReviewTime: 5,
+  avgTimeToFirstReview: 2,
+  avgCycleTime: 24,
+  weeklyActivity: [{ name: '2024-W01', prs: 3 }],
+  monthlyActivity: [{ name: '2024-01', prs: 8 }],
+  reviewsGiven: 7,
+  reviewsReceived: 9,
+  avgReviewResponseTime: 5,
+  fastestReview: 1,
+  slowestReview: 48,
+  repoPerformance: [
+    { name: 'org/repo', totalPRs: 10, mergeRate: 70, reviewCount: 4, avgReviewTime: 6 },
+  ],
+  highlights: {
+    mostDiscussed: { title: 'Big PR', url: 'https://github.com/org/repo/pull/1', comments: 12 },
+    fastestMerged: { title: 'Quick fix', url: 'https://github.com/org/repo/pull/2', time: 0.5 },
+    largest: {
+      title: 'Refactor',
+      url: 'https://github.com/org/repo/pull/3',
+      additions: 500,
+      deletions: 100,
+    },
+  },
+};
+
+function makeRequest(params: Record<string, string> = {}): Request {
+  const url = new URL('http://localhost/api/pr-insights');
+  for (const [key, value] of Object.entries(params)) {
+    url.searchParams.set(key, value);
+  }
+  return new Request(url.toString());
+}
+
+describe('GET /api/pr-insights', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    vi.mocked(fetchPRInsights).mockResolvedValue(mockInsights);
+  });
+
+  it('returns 400 when the username parameter is missing', async () => {
+    const response = await GET(makeRequest());
+
+    expect(response.status).toBe(400);
+    const body = await response.json();
+    expect(body.error).toBe('Username is required');
+    expect(fetchPRInsights).not.toHaveBeenCalled();
+  });
+
+  it('returns 400 when the username exceeds the 39 character GitHub limit', async () => {
+    const longUsername = 'a'.repeat(40);
+    const response = await GET(makeRequest({ username: longUsername }));
+
+    expect(response.status).toBe(400);
+    const body = await response.json();
+    expect(body.error).toBe('Invalid GitHub username');
+    expect(fetchPRInsights).not.toHaveBeenCalled();
+  });
+
+  it('returns 400 for a username containing invalid characters', async () => {
+    const response = await GET(makeRequest({ username: 'invalid_user!' }));
+
+    expect(response.status).toBe(400);
+    const body = await response.json();
+    expect(body.error).toBe('Invalid GitHub username');
+    expect(fetchPRInsights).not.toHaveBeenCalled();
+  });
+
+  it('trims whitespace from the username before validation and fetching', async () => {
+    const response = await GET(makeRequest({ username: '  octocat  ' }));
+
+    expect(response.status).toBe(200);
+    expect(fetchPRInsights).toHaveBeenCalledWith('octocat');
+  });
+
+  it('returns the full PR insights payload on a successful fetch', async () => {
+    const response = await GET(makeRequest({ username: 'octocat' }));
+
+    expect(response.status).toBe(200);
+    const body = await response.json();
+    expect(body).toEqual(mockInsights);
+    expect(fetchPRInsights).toHaveBeenCalledWith('octocat');
+  });
+
+  it('returns 500 with the error message when fetchPRInsights throws an Error', async () => {
+    vi.mocked(fetchPRInsights).mockRejectedValue(new Error('GitHub API error'));
+
+    const response = await GET(makeRequest({ username: 'octocat' }));
+
+    expect(response.status).toBe(500);
+    const body = await response.json();
+    expect(body.error).toBe('GitHub API error');
+  });
+
+  it('returns 500 with a generic message when fetchPRInsights throws a non-Error value', async () => {
+    vi.mocked(fetchPRInsights).mockRejectedValue('unexpected failure');
+
+    const response = await GET(makeRequest({ username: 'octocat' }));
+
+    expect(response.status).toBe(500);
+    const body = await response.json();
+    expect(body.error).toBe('Failed to fetch PR insights');
+  });
+});