diff --git a/apps/api/tests/lib/requireAdmin.test.ts b/apps/api/tests/lib/requireAdmin.test.ts
new file mode 100644
index 0000000..b231de8
--- /dev/null
+++ b/apps/api/tests/lib/requireAdmin.test.ts
@@ -0,0 +1,131 @@
+/**
+ * requireAdmin middleware tests (Plan 10-02, Task 1)
+ *
+ * Behavior-pinned contracts:
+ *   1. non-admin DB row → 403 { error: 'Forbidden' }, next() NOT called
+ *   2. admin DB row → next() called, request proceeds
+ *   3. no resolved user on context (c.get('user') undefined) → 403
+ *   4. role is read from the DB (users.is_admin), NOT from context user object —
+ *      a context user claiming isAdmin=true but with is_admin=false in DB is still 403
+ *      (bypass only skips OIDC, not the DB check — T-10-04, T-10-05)
+ *
+ * Uses mocked db to test the middleware in isolation (no live DB required).
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { Hono } from 'hono';
+
+// Mock the db singleton so tests do not need a live MariaDB connection.
+vi.mock('../../src/db/client.js', () => ({
+  db: {
+    select: vi.fn(),
+  },
+}));
+
+// Bring in the ContextVariableMap augmentation (sets up c.get('user') typing)
+vi.mock('../../src/auth/devBypass.js', () => ({
+  DEV_USER: { id: 1, oidcIss: 'dev', oidcSub: 'dev-user', displayName: 'Dev User', color: '#4A90D9' },
+  devAuthBypass: () => async (_c: unknown, next: () => Promise<void>) => next(),
+  COLOR_PALETTE: ['#4A90D9'],
+}));
+
+import { db } from '../../src/db/client.js';
+import { requireAdmin } from '../../src/lib/requireAdmin.js';
+
+const mockDb = db as { select: ReturnType<typeof vi.fn> };
+
+// ── DB query chain builder ────────────────────────────────────────────────────
+
+function makeSelectChain(resolvedValue: unknown[]) {
+  const chain = {
+    from: vi.fn(),
+    where: vi.fn(),
+    limit: vi.fn().mockResolvedValue(resolvedValue),
+  };
+  chain.from.mockReturnValue(chain);
+  chain.where.mockReturnValue(chain);
+  return chain;
+}
+
+// ── Test app factory ──────────────────────────────────────────────────────────
+
+/**
+ * Creates a minimal Hono app that mounts requireAdmin and a downstream handler
+ * that sets a header so we can assert whether next() was called.
+ */
+function makeTestApp(userOnContext: { id: number; isAdmin?: boolean } | undefined) {
+  const app = new Hono();
+
+  // Inject user into context (simulates devAuthBypass or OIDC middleware output)
+  app.use('*', async (c, next) => {
+    if (userOnContext !== undefined) {
+      // Cast: the ContextVariableMap expects the full DEV_USER shape; we only need id
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      c.set('user', userOnContext as any);
+    }
+    await next();
+  });
+
+  app.use('*', requireAdmin);
+
+  app.get('/test', (c) => c.json({ ok: true }));
+
+  return app;
+}
+
+// ── Tests ─────────────────────────────────────────────────────────────────────
+
+describe('requireAdmin middleware', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('returns 403 for an authenticated non-admin user (is_admin=false in DB)', async () => {
+    // DB returns row with isAdmin=false
+    mockDb.select.mockReturnValue(makeSelectChain([{ isAdmin: false }]));
+
+    const app = makeTestApp({ id: 42 });
+    const res = await app.request('/test');
+
+    expect(res.status).toBe(403);
+    const body = (await res.json()) as { error: string };
+    expect(body.error).toBe('Forbidden');
+  });
+
+  it('calls next() for an authenticated admin user (is_admin=true in DB)', async () => {
+    // DB returns row with isAdmin=true
+    mockDb.select.mockReturnValue(makeSelectChain([{ isAdmin: true }]));
+
+    const app = makeTestApp({ id: 1 });
+    const res = await app.request('/test');
+
+    expect(res.status).toBe(200);
+    const body = (await res.json()) as { ok: boolean };
+    expect(body.ok).toBe(true);
+  });
+
+  it('returns 403 when no user is resolved on context (c.get("user") is undefined)', async () => {
+    // No DB call expected — userId is missing, short-circuit to 403
+    const app = makeTestApp(undefined);
+    const res = await app.request('/test');
+
+    expect(res.status).toBe(403);
+    const body = (await res.json()) as { error: string };
+    expect(body.error).toBe('Forbidden');
+    // DB must NOT be queried when user is absent
+    expect(mockDb.select).not.toHaveBeenCalled();
+  });
+
+  it('returns 403 when context user claims isAdmin=true but DB row has is_admin=false (T-10-04)', async () => {
+    // Context carries a spoofed isAdmin claim — DB should be the authority
+    mockDb.select.mockReturnValue(makeSelectChain([{ isAdmin: false }]));
+
+    // User on context has isAdmin=true (as if a client tried to inject it)
+    const app = makeTestApp({ id: 99, isAdmin: true });
+    const res = await app.request('/test');
+
+    expect(res.status).toBe(403);
+    const body = (await res.json()) as { error: string };
+    expect(body.error).toBe('Forbidden');
+  });
+});