diff --git a/TunnelKit/Sources/AppExtension/TunnelKitProvider+Interaction.swift b/TunnelKit/Sources/AppExtension/TunnelKitProvider+Interaction.swift
index 1dd539f..e035a35 100644
--- a/TunnelKit/Sources/AppExtension/TunnelKitProvider+Interaction.swift
+++ b/TunnelKit/Sources/AppExtension/TunnelKitProvider+Interaction.swift
@@ -99,10 +99,22 @@ extension TunnelKitProvider {
         /// Socket failed to reach active state.
         case socketActivity
         
+        /// Credentials authentication failed.
+        case authenticationFailed
+
+        /// TLS handshake failed.
+        case tlsFailed
+        
+        /// Tunnel timed out.
+        case timeout
+        
         /// An error occurred at the link level.
         case linkError
         
         /// The current network changed (e.g. switched from WiFi to data connection).
         case networkChanged
+        
+        /// The server replied in an unexpected way.
+        case unexpectedReply
     }
 }
diff --git a/TunnelKit/Sources/Core/SessionError.swift b/TunnelKit/Sources/Core/SessionError.swift
index 90e8656..4f37b6d 100644
--- a/TunnelKit/Sources/Core/SessionError.swift
+++ b/TunnelKit/Sources/Core/SessionError.swift
@@ -38,7 +38,7 @@
 import Foundation
 
 /// The possible errors raised/thrown during `SessionProxy` operation.
-public enum SessionError: Error {
+public enum SessionError: String, Error {
     
     /// The negotiation timed out.
     case negotiationTimeout