diff --git a/crates/app/cli/src/engine.rs b/crates/app/cli/src/engine.rs
new file mode 100644
index 0000000..cc4ce8e
--- /dev/null
+++ b/crates/app/cli/src/engine.rs
@@ -0,0 +1,39 @@
+use crate::messages::Message;
+use tokio::sync::mpsc;
+
+/// The main background task that handles logic, API calls, and state updates.
+pub async fn run_engine_loop(mut rx: mpsc::Receiver<Message>) {
+    while let Some(msg) = rx.recv().await {
+        match msg {
+            Message::UserAction(action) => {
+                println!("Engine received action: {:?}", action);
+                // TODO: Process action
+            }
+            _ => {}
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::messages::{Message, UserAction};
+
+    #[tokio::test]
+    async fn test_engine_loop_structure() {
+        let (tx, rx) = mpsc::channel(1);
+        
+        // Spawn the engine loop
+        let handle = tokio::spawn(async move {
+            run_engine_loop(rx).await;
+        });
+
+        // Send a message
+        let msg = Message::UserAction(UserAction::Input("ping".to_string()));
+        assert!(tx.send(msg).await.is_ok());
+
+        // Cleanup: dropping tx should close rx and terminate the loop
+        drop(tx);
+        assert!(handle.await.is_ok());
+    }
+}
diff --git a/crates/app/cli/src/main.rs b/crates/app/cli/src/main.rs
index 1ae67d9..c59c591 100644
--- a/crates/app/cli/src/main.rs
+++ b/crates/app/cli/src/main.rs
@@ -1,5 +1,6 @@
 mod commands;
 mod messages;
+mod engine;
 
 use clap::{Parser, ValueEnum};
 use color_eyre::eyre::{Result, eyre};
@@ -333,6 +334,15 @@ async fn main() -> Result<()> {
     let session_id = generate_session_id();
     let output_format = args.output_format;
 
+    // Initialize async engine infrastructure
+    let (tx, rx) = tokio::sync::mpsc::channel::<messages::Message>(100);
+    // Spawn the Engine Loop
+    tokio::spawn(async move {
+        engine::run_engine_loop(rx).await;
+    });
+    // Keep tx for future use (will be passed to UI/REPL)
+    let _tx = tx;
+
     if let Some(cmd) = args.cmd {
         match cmd {
             Cmd::Read { path } => {