diff --git a/src/services/helper.ts b/src/services/helper.ts
new file mode 100644
index 0000000..8963b87
--- /dev/null
+++ b/src/services/helper.ts
@@ -0,0 +1,14 @@
+/**
+ * Shared helper utilities for domain services.
+ */
+
+import { getRequestContext } from "../context.ts";
+import type { OpenProjectClient } from "../client/api-client.ts";
+
+/**
+ * Resolves an OpenProjectClient instance.
+ * Prefers an explicitly passed client; falls back to the ambient RequestContext.
+ */
+export function resolveClient(client?: OpenProjectClient): OpenProjectClient {
+  return client ?? getRequestContext().client;
+}
diff --git a/tests/services.test.ts b/tests/services.test.ts
new file mode 100644
index 0000000..c51e73a
--- /dev/null
+++ b/tests/services.test.ts
@@ -0,0 +1,35 @@
+import { describe, expect, test } from "bun:test";
+import { resolveClient } from "../src/services/helper.ts";
+import { OpenProjectClient } from "../src/client/api-client.ts";
+import { runWithContext, type RequestContext } from "../src/context.ts";
+
+describe("Domain Services Helper", () => {
+  test("resolveClient returns explicit client if provided", () => {
+    const customClient = new OpenProjectClient({
+      baseUrl: "http://example.com",
+      apiKey: "custom-key",
+    });
+    const result = resolveClient(customClient);
+    expect(result).toBe(customClient);
+  });
+
+  test("resolveClient falls back to getRequestContext().client when omitted", () => {
+    const ambientClient = new OpenProjectClient({
+      baseUrl: "http://example.com",
+      apiKey: "ambient-key",
+    });
+    const context: RequestContext = {
+      client: ambientClient,
+      isReadOnly: false,
+    };
+
+    runWithContext(context, () => {
+      const result = resolveClient();
+      expect(result).toBe(ambientClient);
+    });
+  });
+
+  test("resolveClient throws error when called without client and outside context", () => {
+    expect(() => resolveClient()).toThrow("No active RequestContext found");
+  });
+});