diff --git a/src/cortex-cli/src/debug_cmd/handlers/wait.rs b/src/cortex-cli/src/debug_cmd/handlers/wait.rs
index 799e2d755..6950e99c7 100644
--- a/src/cortex-cli/src/debug_cmd/handlers/wait.rs
+++ b/src/cortex-cli/src/debug_cmd/handlers/wait.rs
@@ -54,10 +54,8 @@ pub async fn run_wait(args: WaitArgs) -> Result<()> {
 
         while start.elapsed() < timeout {
             match client.get(&args.server_url).send().await {
-                Ok(response)
-                    if response.status().is_success() || response.status().is_client_error() =>
-                {
-                    // Server is responding (even 4xx means it's up)
+                Ok(response) if is_server_ready_status(response.status()) => {
+                    // The readiness endpoint must respond successfully.
                     success = true;
                     break;
                 }
@@ -150,3 +148,7 @@ pub async fn run_wait(args: WaitArgs) -> Result<()> {
 
     Ok(())
 }
+
+fn is_server_ready_status(status: reqwest::StatusCode) -> bool {
+    status.is_success()
+}
diff --git a/src/cortex-cli/tests/debug_wait.rs b/src/cortex-cli/tests/debug_wait.rs
new file mode 100644
index 000000000..6f5fa7c39
--- /dev/null
+++ b/src/cortex-cli/tests/debug_wait.rs
@@ -0,0 +1,58 @@
+use std::io::{Read, Write};
+use std::net::TcpListener;
+use std::process::Command;
+use std::thread;
+
+fn serve_once(status_line: &'static str) -> String {
+    let listener = TcpListener::bind("127.0.0.1:0").expect("bind test server");
+    let addr = listener.local_addr().expect("read local addr");
+
+    thread::spawn(move || {
+        if let Ok((mut stream, _)) = listener.accept() {
+            let mut request = [0; 1024];
+            let _ = stream.read(&mut request);
+            let body = b"test";
+            let response = format!(
+                "{status_line}\r\nContent-Length: {}\r\nConnection: close\r\n\r\n",
+                body.len()
+            );
+            let _ = stream.write_all(response.as_bytes());
+            let _ = stream.write_all(body);
+        }
+    });
+
+    format!("http://{addr}")
+}
+
+#[test]
+fn debug_wait_server_ready_rejects_404() {
+    let server_url = serve_once("HTTP/1.1 404 Not Found");
+
+    let output = Command::new(env!("CARGO_BIN_EXE_Cortex"))
+        .args([
+            "debug",
+            "wait",
+            "--server-ready",
+            "--server-url",
+            &server_url,
+            "--timeout",
+            "1",
+            "--interval",
+            "100",
+            "--json",
+        ])
+        .output()
+        .expect("run Cortex debug wait");
+
+    assert!(
+        !output.status.success(),
+        "404 readiness response should fail; stdout={}, stderr={}",
+        String::from_utf8_lossy(&output.stdout),
+        String::from_utf8_lossy(&output.stderr)
+    );
+    assert!(
+        String::from_utf8_lossy(&output.stdout).contains("\"success\": false"),
+        "stdout should report failure JSON: {}",
+        String::from_utf8_lossy(&output.stdout)
+    );
+}