diff --git a/src/api/client.ts b/src/api/client.ts
new file mode 100644
index 0000000..bd83d86
--- /dev/null
+++ b/src/api/client.ts
@@ -0,0 +1,41 @@
+import type { ApiErrorCode, ApiResponse } from "@/api/contracts/common";
+
+export type MockClientOptions = {
+  latencyMs?: number;
+  errorRate?: number;
+};
+
+const defaultOptions: Required<MockClientOptions> = {
+  latencyMs: 45,
+  errorRate: 0,
+};
+
+let options = defaultOptions;
+
+export function configureMockClient(next: MockClientOptions) {
+  options = { ...options, ...next };
+}
+
+export async function mockResponse<T>(
+  data: T,
+  overrides?: { errorCode?: ApiErrorCode; message?: string; latencyMs?: number },
+): Promise<ApiResponse<T>> {
+  const latencyMs = overrides?.latencyMs ?? options.latencyMs;
+  await new Promise((resolve) => setTimeout(resolve, latencyMs));
+  const requestId = `req_${Math.random().toString(16).slice(2, 10)}`;
+  if (overrides?.errorCode || Math.random() < options.errorRate) {
+    return {
+      data: null,
+      meta: { requestId, latencyMs },
+      error: {
+        code: overrides?.errorCode ?? "NETWORK_ERROR",
+        message: overrides?.message ?? "The mock service could not complete the request.",
+      },
+    };
+  }
+  return {
+    data,
+    meta: { requestId, latencyMs },
+    error: null,
+  };
+}