diff --git a/crates/dbx-core/src/agent_connection.rs b/crates/dbx-core/src/agent_connection.rs
index 1afc1f24e4..40078c49c3 100644
--- a/crates/dbx-core/src/agent_connection.rs
+++ b/crates/dbx-core/src/agent_connection.rs
@@ -929,6 +929,26 @@ mod tests {
         assert_eq!(params["connection_string"], "jdbc:vastbase://vastbase.example.com:5432/postgres");
     }
 
+    #[test]
+    fn kingbase_agent_params_keep_legacy_postgres_default_when_database_is_empty() {
+        let cfg = config(DatabaseType::Kingbase, None);
+
+        let params = agent_connect_params(&cfg, "kingbase.example.com", 54321, "").unwrap();
+
+        assert_eq!(params["database"], "postgres");
+        assert_eq!(params["connection_string"], "jdbc:kingbase8://kingbase.example.com:54321/postgres");
+    }
+
+    #[test]
+    fn kingbase_agent_params_preserve_explicit_database() {
+        let cfg = config(DatabaseType::Kingbase, Some("application"));
+
+        let params = agent_connect_params(&cfg, "kingbase.example.com", 54321, "application").unwrap();
+
+        assert_eq!(params["database"], "application");
+        assert_eq!(params["connection_string"], "jdbc:kingbase8://kingbase.example.com:54321/application");
+    }
+
     #[test]
     fn uxdb_agent_params_use_vendor_jdbc_url() {
         let cfg = config(DatabaseType::Uxdb, Some("uxdb"));
diff --git a/crates/dbx-core/src/models/connection.rs b/crates/dbx-core/src/models/connection.rs
index c47ee49267..31c43eafb8 100644
--- a/crates/dbx-core/src/models/connection.rs
+++ b/crates/dbx-core/src/models/connection.rs
@@ -857,7 +857,10 @@ impl ConnectionConfig {
             DatabaseType::Rqlite | DatabaseType::Turso | DatabaseType::CloudflareD1 => Some("main"),
             DatabaseType::Gaussdb | DatabaseType::OpenGauss => Some("postgres"),
             DatabaseType::Kwdb => Some("defaultdb"),
-            DatabaseType::Vastbase => Some("postgres"),
+            // Keep saved Kingbase connections from before the database field became
+            // required working after upgrade. New and edited desktop connections
+            // still require an explicit existing database in the connection form.
+            DatabaseType::Kingbase | DatabaseType::Vastbase => Some("postgres"),
             DatabaseType::Highgo => Some("highgo"),
             DatabaseType::Uxdb => Some("uxdb"),
             DatabaseType::Yashandb => Some("yasdb"),
@@ -3444,13 +3447,17 @@ mod tests {
     }
 
     #[test]
-    fn kingbase_empty_database_has_no_default() {
+    fn kingbase_empty_database_uses_legacy_postgres_default() {
         let mut config = mysql_config("SYSTEM", "secret", None);
         config.db_type = DatabaseType::Kingbase;
         config.port = 54321;
 
-        assert_eq!(config.effective_database(), None);
-        assert_eq!(config.connection_url(), "kingbase://SYSTEM:secret@10.1.2.3:54321");
+        assert_eq!(config.effective_database(), Some("postgres"));
+        assert_eq!(config.connection_url(), "kingbase://SYSTEM:secret@10.1.2.3:54321/postgres");
+
+        config.database = Some("application".to_string());
+        assert_eq!(config.effective_database(), Some("application"));
+        assert_eq!(config.connection_url(), "kingbase://SYSTEM:secret@10.1.2.3:54321/application");
     }
 
     #[test]