Warn on client server version mismatch

src/bin/dosh-client.rs

@@ -925,6 +925,13 @@ async fn run_doctor_for_host(
                     &check.server_version
                 }
             );
+            if server_version_mismatch(&check.server_version) {
+                println!(
+                    "[warn] version mismatch: client={} server={}",
+                    env!("CARGO_PKG_VERSION"),
+                    check.server_version
+                );
+            }
             println!("[ok] known host: trusted");
             println!("[ok] native auth: authorized as {}", check.requested_user);
             println!(
@@ -942,6 +949,10 @@ async fn run_doctor_for_host(
     }
 }
 
+fn server_version_mismatch(server_version: &str) -> bool {
+    !server_version.is_empty() && server_version != env!("CARGO_PKG_VERSION")
+}
+
 fn ensure_tui_safe_status_overlay(bytes: &[u8]) -> Result<()> {
     anyhow::ensure!(
         bytes.starts_with(b"\x1b7"),
@@ -5101,9 +5112,9 @@ mod tests {
         parse_escape_key, parse_local_forward, parse_remote_forward, parse_ssh_config,
         queue_pending_user_input, raw_contains_host_table, recv_response_until,
         render_status_clear, render_status_overlay, requested_env, resolved_startup_command,
-        rewrite_forward_command, selected_predict_mode, selected_udp_host, ssh_destination_host,
-        ssh_username, ssh_with_user, startup_command, status_ssh_target, toml_bare_key_or_quoted,
-        update_check_requested, valid_forward_host,
+        rewrite_forward_command, selected_predict_mode, selected_udp_host, server_version_mismatch,
+        ssh_destination_host, ssh_username, ssh_with_user, startup_command, status_ssh_target,
+        toml_bare_key_or_quoted, update_check_requested, valid_forward_host,
     };
     use dosh::config::{ClientConfig, CommandExtension, HostConfig};
     use dosh::native::EnvVar;
@@ -5792,6 +5803,13 @@ mod tests {
         assert!(RESTART_STATUS_SCRIPT.contains("dosh-server"));
     }
 
+    #[test]
+    fn doctor_detects_server_version_mismatch() {
+        assert!(!server_version_mismatch(""));
+        assert!(!server_version_mismatch(env!("CARGO_PKG_VERSION")));
+        assert!(server_version_mismatch("0.0.0-old"));
+    }
+
     #[test]
     fn release_download_url_uses_latest_release_asset() {
         assert_eq!(