diff --git a/app/api/github/route.theme-contrast.test.ts b/app/api/github/route.theme-contrast.test.ts
new file mode 100644
index 000000000..98a2b45d4
--- /dev/null
+++ b/app/api/github/route.theme-contrast.test.ts
@@ -0,0 +1,97 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { GET } from './route';
+
+vi.mock('../../../lib/github', () => ({
+  getFullDashboardData: vi.fn(),
+}));
+
+vi.mock('next/server', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('next/server')>();
+  return {
+    ...actual,
+    after: (fn: () => unknown) => {
+      void fn();
+    },
+  };
+});
+
+import { getFullDashboardData } from '../../../lib/github';
+import { quotaMonitor } from '@/services/github/quota-monitor';
+import { refreshPolicy } from '@/services/github/refresh-policy';
+import { refreshRateLimiter } from '@/services/github/refresh-rate-limiter';
+import { backgroundRefresh } from '@/services/github/background-refresh';
+
+function makeRequest(
+  params: Record<string, string> = {},
+  headers: Record<string, string> = {}
+): Request {
+  const url = new URL('http://localhost/api/github');
+
+  for (const [key, value] of Object.entries(params)) {
+    url.searchParams.set(key, value);
+  }
+
+  return new Request(url.toString(), {
+    headers: new Headers(headers),
+  });
+}
+
+describe('GET /api/github Theme Contrast', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+
+    vi.mocked(getFullDashboardData).mockResolvedValue({
+      profile: { lastSyncedAt: new Date().toISOString() },
+      calendar: {},
+      lastSyncedAt: new Date().toISOString(),
+    } as unknown as Awaited<ReturnType<typeof getFullDashboardData>>);
+
+    quotaMonitor.reset();
+    refreshPolicy.reset();
+    refreshRateLimiter.reset();
+    backgroundRefresh.reset();
+  });
+
+  it('returns Cached status for normal requests', async () => {
+    const response = await GET(makeRequest({ username: 'torvalds' }));
+
+    expect(response.status).toBe(200);
+    expect(response.headers.get('X-Refresh-Status')).toBe('Cached');
+    expect(response.headers.get('X-Cache-Status')).toBe('HIT');
+  });
+
+  it('returns Fresh status for refresh requests', async () => {
+    const response = await GET(makeRequest({ username: 'torvalds', refresh: 'true' }));
+
+    expect(response.status).toBe(200);
+    expect(response.headers.get('X-Refresh-Status')).toBe('Fresh');
+    expect(response.headers.get('X-Cache-Status')).toBe('MISS');
+  });
+
+  it('returns cooldown cached status for repeated refresh requests', async () => {
+    await GET(makeRequest({ username: 'torvalds', refresh: 'true' }));
+
+    const response = await GET(makeRequest({ username: 'torvalds', refresh: 'true' }));
+
+    expect(response.status).toBe(200);
+    expect(response.headers.get('X-Refresh-Status')).toBe('Cooldown-Served-Cached');
+  });
+
+  it('returns 429 when quota is low during refresh', async () => {
+    quotaMonitor.setQuota(5000, 400, Date.now() + 60000);
+
+    const response = await GET(makeRequest({ username: 'torvalds', refresh: 'true' }));
+
+    expect(response.status).toBe(429);
+  });
+
+  it('returns cache-control headers appropriate to request mode', async () => {
+    const cachedResponse = await GET(makeRequest({ username: 'torvalds' }));
+
+    expect(cachedResponse.headers.get('Cache-Control')).toContain('stale-while-revalidate');
+
+    const freshResponse = await GET(makeRequest({ username: 'octocat', refresh: 'true' }));
+
+    expect(freshResponse.headers.get('Cache-Control')).toContain('no-cache');
+  });
+});