diff --git a/.env.example b/.env.example
index 3f7142b..ec187ae 100644
--- a/.env.example
+++ b/.env.example
@@ -9,5 +9,9 @@ CALDAV_CALENDAR_PATH=/calendars/your-username/personal/
 # Optional: Task/Todo collection path
 CALDAV_TASKS_PATH=/calendars/your-username/tasks/
 
+# Backend API Configuration
+# Set this to point to your backend API server
+BACKEND_API_URL=http://localhost:3000/api
+
 # Development settings
 RUST_LOG=info
\ No newline at end of file
diff --git a/Trunk.toml b/Trunk.toml
index fe27fce..ca0054e 100644
--- a/Trunk.toml
+++ b/Trunk.toml
@@ -2,6 +2,9 @@
 target = "index.html"
 dist = "dist"
 
+[env]
+BACKEND_API_URL = "http://localhost:3000/api"
+
 [watch]
 watch = ["src", "Cargo.toml"]
 ignore = ["backend/"]
diff --git a/src/auth.rs b/src/auth.rs
index 45a9207..bc39aa7 100644
--- a/src/auth.rs
+++ b/src/auth.rs
@@ -50,10 +50,12 @@ pub struct AuthService {
 
 impl AuthService {
     pub fn new() -> Self {
-        // Default to localhost backend - could be configurable via env var in the future
-        Self {
-            base_url: "http://localhost:3000/api".to_string(),
-        }
+        // Get backend URL from environment variable at compile time, fallback to localhost
+        let base_url = option_env!("BACKEND_API_URL")
+            .unwrap_or("http://localhost:3000/api")
+            .to_string();
+        
+        Self { base_url }
     }
 
     pub async fn register(&self, request: RegisterRequest) -> Result<AuthResponse, String> {