diff --git a/apps/calendar/apps/web/src/lib/api/client.ts b/apps/calendar/apps/web/src/lib/api/client.ts
index 5ca7b5a7b..5b12c0f6a 100644
--- a/apps/calendar/apps/web/src/lib/api/client.ts
+++ b/apps/calendar/apps/web/src/lib/api/client.ts
@@ -6,24 +6,40 @@
  * refreshes expired tokens before making requests.
  */
 
+import { browser } from '$app/environment';
 import { env } from '$env/dynamic/public';
-import { createApiClient, type ApiResult } from '@manacore/shared-api-client';
+import { createApiClient, type ApiResult, type ApiClient } from '@manacore/shared-api-client';
 import { authStore } from '$lib/stores/auth.svelte';
 
-const API_BASE = env.PUBLIC_BACKEND_URL || 'http://localhost:3014';
+// Use client URL in browser (injected by hooks.server.ts), SSR URL on server
+function getApiBase(): string {
+	if (browser && typeof window !== 'undefined') {
+		const injectedUrl = (window as unknown as { __PUBLIC_BACKEND_URL__?: string })
+			.__PUBLIC_BACKEND_URL__;
+		if (injectedUrl) return injectedUrl;
+	}
+	return env.PUBLIC_BACKEND_URL || 'http://localhost:3014';
+}
 
 /**
- * Calendar API client instance
+ * Calendar API client instance (lazy initialized)
  * - Auto token handling via authStore.getValidToken()
  * - Consistent ApiResult<T> response format
  */
-const api = createApiClient({
-	baseUrl: API_BASE,
-	apiPrefix: '/api/v1',
-	getAuthToken: () => authStore.getValidToken(),
-	timeout: 30000,
-	debug: import.meta.env.DEV,
-});
+let _api: ApiClient | null = null;
+
+function getApi(): ApiClient {
+	if (!_api) {
+		_api = createApiClient({
+			baseUrl: getApiBase(),
+			apiPrefix: '/api/v1',
+			getAuthToken: () => authStore.getValidToken(),
+			timeout: 30000,
+			debug: import.meta.env.DEV,
+		});
+	}
+	return _api;
+}
 
 /**
  * Legacy fetchApi interface for backwards compatibility
@@ -45,6 +61,7 @@ export async function fetchApi<T>(
 	options: FetchOptions = {}
 ): Promise<ApiResult<T>> {
 	const { method = 'GET', body, isFormData = false } = options;
+	const api = getApi();
 
 	if (isFormData && body instanceof FormData) {
 		return api.upload<T>(endpoint, body);