[0.60.5] Preserve SSH username case in remote sessions

rust/src/agent_sessions/remote.rs

@@ -15,13 +15,13 @@ impl RemoteSessionFetcher {
         let valid = Self::sanitized_hosts(hosts);
         let valid_keys = valid
             .iter()
-            .map(|host| host.to_ascii_lowercase())
+            .map(|host| Self::host_dedup_key(host))
             .collect::<HashSet<_>>();
         let mut invalid = hosts
             .iter()
             .filter(|host| {
                 Self::validate_host(host).is_err()
-                    && !valid_keys.contains(&host.trim().to_ascii_lowercase())
+                    && !valid_keys.contains(&Self::host_dedup_key(host.trim()))
             })
             .map(|_| {
                 AgentSessionHostResult::failed(
@@ -175,7 +175,7 @@ impl RemoteSessionFetcher {
                 continue;
             };
 
-            let key = host.to_ascii_lowercase();
+            let key = Self::host_dedup_key(&host);
             if seen.insert(key) {
                 sanitized.push(host);
             }
@@ -188,6 +188,19 @@ impl RemoteSessionFetcher {
         Self::sanitized_hosts(&manual.iter().chain(automatic).cloned().collect::<Vec<_>>())
     }
 
+    /// Deduplicate host names case-insensitively while preserving SSH username
+    /// case. SSH may treat `Alice@host` and `alice@host` as different users,
+    /// whereas the host component remains case-insensitive for this input.
+    fn host_dedup_key(host: &str) -> String {
+        let host = host.trim();
+        if let Some(separator) = host.rfind('@') {
+            let (prefix, hostname) = host.split_at(separator + 1);
+            format!("{prefix}{}", hostname.to_ascii_lowercase())
+        } else {
+            host.to_ascii_lowercase()
+        }
+    }
+
     pub fn validate_host(host: &str) -> Result<String, String> {
         let host = host.trim();
         if host.is_empty() {

rust/src/agent_sessions/tests.rs

@@ -105,6 +105,34 @@ bad line
         assert_eq!(hosts, vec!["good".to_string()]);
     }
 
+    #[test]
+    fn ssh_username_case_is_preserved_while_host_case_dedupes() {
+        let hosts = RemoteSessionFetcher::sanitized_hosts(&[
+            "Alice@HOST".to_string(),
+            "Alice@host".to_string(),
+            "alice@host".to_string(),
+            "alice@HOST".to_string(),
+            "HOST".to_string(),
+            "host".to_string(),
+        ]);
+
+        assert_eq!(
+            hosts,
+            vec![
+                "Alice@HOST".to_string(),
+                "alice@host".to_string(),
+                "HOST".to_string()
+            ]
+        );
+        assert_eq!(
+        RemoteSessionFetcher::merge_hosts(
+            &["Alice@HOST".to_string()],
+            &["alice@host".to_string()]
+        ),
+        vec!["Alice@HOST".to_string(), "alice@host".to_string()]
+    );
+}
+
     #[test]
     fn tailscale_parser_returns_online_peer_dns_names() {
         let json = r#"{