diff --git a/src/routes/api/tenants/[id]/agents/absences/+server.ts b/src/routes/api/tenants/[id]/agents/absences/+server.ts
index b40f4c8..c7d5cc9 100644
--- a/src/routes/api/tenants/[id]/agents/absences/+server.ts
+++ b/src/routes/api/tenants/[id]/agents/absences/+server.ts
@@ -123,7 +123,8 @@ export const GET: RequestHandler = async ({ params, locals, url }) => {
     });
 
     const agentService = await AgentService.forTenant(tenantId);
-    const absences = await agentService.getAbsences(startDate || undefined, endDate || undefined);
+    const absences =
+      (await agentService.getAbsences(startDate || undefined, endDate || undefined)) || [];
 
     log.debug("All Agents absences retrieved successfully", {
       tenantId,
diff --git a/src/routes/api/tenants/[id]/agents/absences/__tests__/absence-overview-api.test.ts b/src/routes/api/tenants/[id]/agents/absences/__tests__/absence-overview-api.test.ts
new file mode 100644
index 0000000..716d06c
--- /dev/null
+++ b/src/routes/api/tenants/[id]/agents/absences/__tests__/absence-overview-api.test.ts
@@ -0,0 +1,200 @@
+/* eslint-disable @typescript-eslint/no-explicit-any */
+import type { RequestEvent } from "@sveltejs/kit";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { GET } from "../+server";
+
+// Mock dependencies
+vi.mock("$lib/server/services/agent-service", () => ({
+  AgentService: {
+    forTenant: vi.fn(),
+  },
+}));
+
+vi.mock("$lib/logger", () => ({
+  default: {
+    setContext: vi.fn(() => ({
+      debug: vi.fn(),
+      error: vi.fn(),
+    })),
+  },
+}));
+
+import { AgentService } from "$lib/server/services/agent-service";
+import { NotFoundError } from "$lib/server/utils/errors";
+// import { NotFoundError } from "$lib/server/utils/errors";
+
+describe("Agent Absence Detail API Routes", () => {
+  const mockTenantId = "123e4567-e89b-12d3-a456-426614174000";
+  const mockAbsenceId = "absence-456";
+  const mockAgentService = {
+    getAbsences: vi.fn(),
+  };
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    (AgentService.forTenant as any).mockResolvedValue(mockAgentService);
+  });
+
+  function createMockRequestEvent(overrides: Partial<RequestEvent> = {}): RequestEvent {
+    return {
+      params: { id: mockTenantId },
+      searchParams: new URLSearchParams(),
+      locals: {
+        user: {
+          userId: "user123",
+          role: "TENANT_ADMIN",
+          tenantId: mockTenantId,
+        },
+      },
+      request: {
+        json: vi.fn().mockResolvedValue({
+          startDate: "2024-01-15T00:00:00.000Z",
+          endDate: "2024-01-17T23:59:59.999Z",
+          absenceType: "Urlaub",
+          description: "Jahresurlaub",
+          isFullDay: true,
+        }),
+      } as any,
+      url: new URL("http://localhost:3000/api/tenants/123/agents/absences"),
+      ...overrides,
+    } as RequestEvent;
+  }
+
+  describe("GET /api/tenants/[id]/agents/absences", () => {
+    it("should return absences for authenticated tenant admin", async () => {
+      const mockAbsences = [
+        {
+          id: mockAbsenceId,
+          startDate: "2024-01-15T00:00:00.000Z",
+          endDate: "2024-01-17T23:59:59.999Z",
+          absenceType: "Urlaub",
+          description: "Jahresurlaub",
+          isFullDay: true,
+        },
+      ];
+
+      mockAgentService.getAbsences.mockResolvedValue(mockAbsences);
+
+      const event = createMockRequestEvent();
+      const response = await GET(event);
+      const data = await response.json();
+
+      expect(response.status).toBe(200);
+      expect(data.absences).toEqual(mockAbsences);
+      expect(mockAgentService.getAbsences).toHaveBeenCalled();
+    });
+  });
+
+  it("should allow staff to view absence details", async () => {
+    const mockAbsences = [
+      {
+        id: mockAbsenceId,
+        startDate: "2024-01-15T00:00:00.000Z",
+        endDate: "2024-01-17T23:59:59.999Z",
+        absenceType: "Urlaub",
+        description: "Jahresurlaub",
+        isFullDay: true,
+      },
+    ];
+
+    mockAgentService.getAbsences.mockResolvedValue(mockAbsences);
+
+    const event = createMockRequestEvent({
+      locals: {
+        user: {
+          userId: "user123",
+          role: "STAFF",
+          tenantId: mockTenantId,
+        } as any,
+      },
+    });
+    const response = await GET(event);
+    const data = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(data.absences).toEqual(mockAbsences);
+  });
+
+  it("should allow global admin to view absence details for any tenant", async () => {
+    const mockAbsences = [
+      {
+        id: mockAbsenceId,
+        startDate: "2024-01-15T00:00:00.000Z",
+        endDate: "2024-01-17T23:59:59.999Z",
+        absenceType: "Urlaub",
+        description: "Jahresurlaub",
+        isFullDay: true,
+      },
+    ];
+
+    mockAgentService.getAbsences.mockResolvedValue(mockAbsences);
+
+    const event = createMockRequestEvent({
+      locals: {
+        user: {
+          userId: "user123",
+          role: "GLOBAL_ADMIN",
+          tenantId: "different-tenant",
+        } as any,
+      },
+    });
+
+    const response = await GET(event);
+    const data = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(data.absences).toEqual(mockAbsences);
+  });
+
+  it("should return empty list when no absences found", async () => {
+    mockAgentService.getAbsences.mockResolvedValue(null);
+
+    const event = createMockRequestEvent();
+    const response = await GET(event);
+    const data = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(data.absences).toEqual([]);
+  });
+
+  it("should reject unauthenticated requests", async () => {
+    const event = createMockRequestEvent({
+      locals: { user: null } as any,
+    });
+
+    const response = await GET(event);
+    const data = await response.json();
+
+    expect(response.status).toBe(401);
+    expect(data.error).toBe("Authentication required");
+  });
+
+  it("should reject insufficient permissions", async () => {
+    const event = createMockRequestEvent({
+      locals: {
+        user: {
+          userId: "user123",
+          role: "STAFF",
+          tenantId: "different-tenant",
+        } as any,
+      },
+    });
+
+    const response = await GET(event);
+    const data = await response.json();
+
+    expect(response.status).toBe(403);
+    expect(data.error).toBe("Insufficient permissions");
+  });
+
+  it("should handle service errors", async () => {
+    mockAgentService.getAbsences.mockRejectedValue(new NotFoundError("Absences not found"));
+
+    const event = createMockRequestEvent();
+    const response = await GET(event);
+    const data = await response.json();
+
+    expect(response.status).toBe(404);
+    expect(data.error).toBe("Absences not found");
+  });
+});