diff --git a/client/lib/identifier-resolver.spec.ts b/client/lib/identifier-resolver.spec.ts
new file mode 100644
index 00000000..49cbf4de
--- /dev/null
+++ b/client/lib/identifier-resolver.spec.ts
@@ -0,0 +1,403 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import {
+  isUUID,
+  resolveIdentifierToCreator,
+  resolveIdentifierToUserId,
+  resolveIdentifierToUsername,
+} from "./identifier-resolver";
+
+describe("identifier-resolver", () => {
+  describe("isUUID", () => {
+    it("should return true for valid UUIDs", () => {
+      expect(isUUID("550e8400-e29b-41d4-a716-446655440000")).toBe(true);
+      expect(isUUID("6ba7b810-9dad-11d1-80b4-00c04fd430c8")).toBe(true);
+      expect(isUUID("f47ac10b-58cc-4372-a567-0e02b2c3d479")).toBe(true);
+      expect(isUUID("123e4567-e89b-12d3-a456-426614174000")).toBe(true);
+    });
+
+    it("should return true for UUIDs in different cases", () => {
+      expect(isUUID("550E8400-E29B-41D4-A716-446655440000")).toBe(true);
+      expect(isUUID("550e8400-E29B-41d4-A716-446655440000")).toBe(true);
+    });
+
+    it("should return false for invalid UUIDs", () => {
+      expect(isUUID("not-a-uuid")).toBe(false);
+      expect(isUUID("550e8400-e29b-41d4-a716")).toBe(false); // too short
+      expect(isUUID("550e8400-e29b-41d4-a716-446655440000-extra")).toBe(false); // too long
+      expect(isUUID("550e8400e29b41d4a716446655440000")).toBe(false); // missing dashes
+      expect(isUUID("550e8400-e29b-41d4-a716-44665544000g")).toBe(false); // invalid character 'g'
+    });
+
+    it("should return false for empty and invalid inputs", () => {
+      expect(isUUID("")).toBe(false);
+      expect(isUUID("   ")).toBe(false);
+    });
+
+    it("should return false for non-string-like UUIDs", () => {
+      expect(isUUID("12345678-1234-1234-1234-12345678901")).toBe(false); // one char short
+      expect(isUUID("12345678-1234-1234-1234-1234567890123")).toBe(false); // one char long
+    });
+  });
+
+  describe("resolveIdentifierToCreator", () => {
+    let fetchSpy: any;
+
+    beforeEach(() => {
+      // Mock the global fetch function
+      fetchSpy = vi.fn();
+      global.fetch = fetchSpy;
+    });
+
+    afterEach(() => {
+      vi.restoreAllMocks();
+    });
+
+    it("should return null for empty identifier", async () => {
+      const result = await resolveIdentifierToCreator("");
+      expect(result).toBeNull();
+      expect(fetchSpy).not.toHaveBeenCalled();
+    });
+
+    it("should resolve username successfully", async () => {
+      const mockCreator = {
+        id: "550e8400-e29b-41d4-a716-446655440000",
+        username: "testuser",
+        email: "test@example.com",
+      };
+
+      fetchSpy.mockResolvedValueOnce({
+        ok: true,
+        json: async () => mockCreator,
+      });
+
+      const result = await resolveIdentifierToCreator("testuser");
+
+      expect(result).toEqual(mockCreator);
+      expect(fetchSpy).toHaveBeenCalledTimes(1);
+      expect(fetchSpy).toHaveBeenCalledWith("/api/creators/testuser");
+    });
+
+    it("should try UUID lookup when username fails and identifier is UUID", async () => {
+      const uuid = "550e8400-e29b-41d4-a716-446655440000";
+      const mockCreator = {
+        id: uuid,
+        username: "testuser",
+        email: "test@example.com",
+      };
+
+      // First call (username) fails
+      fetchSpy.mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+      });
+
+      // Second call (UUID) succeeds
+      fetchSpy.mockResolvedValueOnce({
+        ok: true,
+        json: async () => mockCreator,
+      });
+
+      const result = await resolveIdentifierToCreator(uuid);
+
+      expect(result).toEqual(mockCreator);
+      expect(fetchSpy).toHaveBeenCalledTimes(2);
+      expect(fetchSpy).toHaveBeenNthCalledWith(1, `/api/creators/${uuid}`);
+      expect(fetchSpy).toHaveBeenNthCalledWith(2, `/api/creators/user/${uuid}`);
+    });
+
+    it("should return null when username lookup fails and identifier is not a UUID", async () => {
+      fetchSpy.mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+      });
+
+      const result = await resolveIdentifierToCreator("notauser");
+
+      expect(result).toBeNull();
+      expect(fetchSpy).toHaveBeenCalledTimes(1);
+      expect(fetchSpy).toHaveBeenCalledWith("/api/creators/notauser");
+    });
+
+    it("should return null when both username and UUID lookups fail", async () => {
+      const uuid = "550e8400-e29b-41d4-a716-446655440000";
+
+      fetchSpy.mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+      });
+
+      fetchSpy.mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+      });
+
+      const result = await resolveIdentifierToCreator(uuid);
+
+      expect(result).toBeNull();
+      expect(fetchSpy).toHaveBeenCalledTimes(2);
+    });
+
+    it("should handle fetch errors gracefully", async () => {
+      const consoleErrorSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+
+      fetchSpy.mockRejectedValueOnce(new Error("Network error"));
+
+      const result = await resolveIdentifierToCreator("testuser");
+
+      expect(result).toBeNull();
+      expect(consoleErrorSpy).toHaveBeenCalledWith(
+        "[Identifier Resolver] Error resolving identifier:",
+        expect.any(Error)
+      );
+
+      consoleErrorSpy.mockRestore();
+    });
+
+    it("should handle malformed JSON responses", async () => {
+      const consoleErrorSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+
+      fetchSpy.mockResolvedValueOnce({
+        ok: true,
+        json: async () => {
+          throw new Error("Invalid JSON");
+        },
+      });
+
+      const result = await resolveIdentifierToCreator("testuser");
+
+      expect(result).toBeNull();
+      expect(consoleErrorSpy).toHaveBeenCalled();
+
+      consoleErrorSpy.mockRestore();
+    });
+  });
+
+  describe("resolveIdentifierToUserId", () => {
+    let fetchSpy: any;
+
+    beforeEach(() => {
+      fetchSpy = vi.fn();
+      global.fetch = fetchSpy;
+    });
+
+    afterEach(() => {
+      vi.restoreAllMocks();
+    });
+
+    it("should return null for empty identifier", async () => {
+      const result = await resolveIdentifierToUserId("");
+      expect(result).toBeNull();
+      expect(fetchSpy).not.toHaveBeenCalled();
+    });
+
+    it("should return the UUID directly if identifier is already a UUID", async () => {
+      const uuid = "550e8400-e29b-41d4-a716-446655440000";
+      const result = await resolveIdentifierToUserId(uuid);
+
+      expect(result).toBe(uuid);
+      expect(fetchSpy).not.toHaveBeenCalled();
+    });
+
+    it("should resolve username to user ID", async () => {
+      const mockCreator = {
+        id: "550e8400-e29b-41d4-a716-446655440000",
+        username: "testuser",
+      };
+
+      fetchSpy.mockResolvedValueOnce({
+        ok: true,
+        json: async () => mockCreator,
+      });
+
+      const result = await resolveIdentifierToUserId("testuser");
+
+      expect(result).toBe(mockCreator.id);
+      expect(fetchSpy).toHaveBeenCalledWith("/api/creators/testuser");
+    });
+
+    it("should return null when username resolution fails", async () => {
+      fetchSpy.mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+      });
+
+      const result = await resolveIdentifierToUserId("nonexistent");
+
+      expect(result).toBeNull();
+    });
+
+    it("should return null when API returns creator without ID", async () => {
+      fetchSpy.mockResolvedValueOnce({
+        ok: true,
+        json: async () => ({ username: "testuser" }), // no id field
+      });
+
+      const result = await resolveIdentifierToUserId("testuser");
+
+      expect(result).toBeNull();
+    });
+
+    it("should handle errors gracefully", async () => {
+      fetchSpy.mockRejectedValueOnce(new Error("Network error"));
+
+      const result = await resolveIdentifierToUserId("testuser");
+
+      expect(result).toBeNull();
+    });
+  });
+
+  describe("resolveIdentifierToUsername", () => {
+    let fetchSpy: any;
+
+    beforeEach(() => {
+      fetchSpy = vi.fn();
+      global.fetch = fetchSpy;
+    });
+
+    afterEach(() => {
+      vi.restoreAllMocks();
+    });
+
+    it("should return null for empty identifier", async () => {
+      const result = await resolveIdentifierToUsername("");
+      expect(result).toBeNull();
+      expect(fetchSpy).not.toHaveBeenCalled();
+    });
+
+    it("should return the username directly if identifier is not a UUID", async () => {
+      const result = await resolveIdentifierToUsername("testuser");
+
+      expect(result).toBe("testuser");
+      expect(fetchSpy).not.toHaveBeenCalled();
+    });
+
+    it("should resolve UUID to username", async () => {
+      const uuid = "550e8400-e29b-41d4-a716-446655440000";
+      const mockCreator = {
+        id: uuid,
+        username: "testuser",
+      };
+
+      // First call (username endpoint with UUID) will fail
+      fetchSpy.mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+      });
+
+      // Second call (UUID endpoint) will succeed
+      fetchSpy.mockResolvedValueOnce({
+        ok: true,
+        json: async () => mockCreator,
+      });
+
+      const result = await resolveIdentifierToUsername(uuid);
+
+      expect(result).toBe(mockCreator.username);
+      expect(fetchSpy).toHaveBeenCalledTimes(2);
+    });
+
+    it("should return null when UUID resolution fails", async () => {
+      const uuid = "550e8400-e29b-41d4-a716-446655440000";
+
+      fetchSpy.mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+      });
+
+      fetchSpy.mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+      });
+
+      const result = await resolveIdentifierToUsername(uuid);
+
+      expect(result).toBeNull();
+    });
+
+    it("should return null when API returns creator without username", async () => {
+      const uuid = "550e8400-e29b-41d4-a716-446655440000";
+
+      fetchSpy.mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+      });
+
+      fetchSpy.mockResolvedValueOnce({
+        ok: true,
+        json: async () => ({ id: uuid }), // no username field
+      });
+
+      const result = await resolveIdentifierToUsername(uuid);
+
+      expect(result).toBeNull();
+    });
+
+    it("should handle errors gracefully", async () => {
+      const uuid = "550e8400-e29b-41d4-a716-446655440000";
+      fetchSpy.mockRejectedValueOnce(new Error("Network error"));
+
+      const result = await resolveIdentifierToUsername(uuid);
+
+      expect(result).toBeNull();
+    });
+  });
+
+  describe("integration scenarios", () => {
+    let fetchSpy: any;
+
+    beforeEach(() => {
+      fetchSpy = vi.fn();
+      global.fetch = fetchSpy;
+    });
+
+    afterEach(() => {
+      vi.restoreAllMocks();
+    });
+
+    it("should handle full workflow: username -> userId -> username", async () => {
+      const mockCreator = {
+        id: "550e8400-e29b-41d4-a716-446655440000",
+        username: "testuser",
+      };
+
+      // First call: resolve username to creator
+      fetchSpy.mockResolvedValueOnce({
+        ok: true,
+        json: async () => mockCreator,
+      });
+
+      const userId = await resolveIdentifierToUserId("testuser");
+      expect(userId).toBe(mockCreator.id);
+
+      // Second call: resolve userId (UUID) back to username
+      // This will make API calls since userId is a UUID
+      fetchSpy.mockResolvedValueOnce({
+        ok: false, // username endpoint will fail
+        status: 404,
+      });
+
+      fetchSpy.mockResolvedValueOnce({
+        ok: true,
+        json: async () => mockCreator,
+      });
+
+      const username = await resolveIdentifierToUsername(userId);
+      expect(username).toBe(mockCreator.username);
+    });
+
+    it("should handle mixed case UUIDs consistently", async () => {
+      const lowerUUID = "550e8400-e29b-41d4-a716-446655440000";
+      const upperUUID = "550E8400-E29B-41D4-A716-446655440000";
+      const mixedUUID = "550e8400-E29B-41d4-A716-446655440000";
+
+      expect(isUUID(lowerUUID)).toBe(true);
+      expect(isUUID(upperUUID)).toBe(true);
+      expect(isUUID(mixedUUID)).toBe(true);
+
+      // All should be recognized as UUIDs and returned directly
+      expect(await resolveIdentifierToUserId(lowerUUID)).toBe(lowerUUID);
+      expect(await resolveIdentifierToUserId(upperUUID)).toBe(upperUUID);
+      expect(await resolveIdentifierToUserId(mixedUUID)).toBe(mixedUUID);
+    });
+  });
+});