diff --git a/chat/server.js b/chat/server.js
index 1e12232..5f42b87 100644
--- a/chat/server.js
+++ b/chat/server.js
@@ -17390,7 +17390,33 @@ async function handleUndoMessage(req, res, sessionId, messageId, userId) {
     sendJson(res, 200, { ok: true, message: 'Undo command sent successfully' });
   } catch (error) {
     log('Undo command failed', { sessionId, messageId, error: String(error) });
-    sendJson(res, 500, { error: `Undo failed: ${error.message}` });
+    
+    // Reset opencode session since it's likely corrupted
+    log('Resetting opencode session due to undo failure', { 
+      sessionId, 
+      messageId, 
+      previousSessionId: session.opencodeSessionId 
+    });
+    session.opencodeSessionId = null;
+    session.initialOpencodeSessionId = null;
+    
+    // Still try to remove the message and clear todos even if opencode undo failed
+    try {
+      if (message.todos) {
+        message.todos = [];
+      }
+      const messageIndex = session.messages.findIndex(m => m.id === messageId);
+      if (messageIndex !== -1) {
+        session.messages.splice(messageIndex, 1);
+      }
+      await persistState();
+      log('Message removed despite undo command failure', { sessionId, messageId });
+    } catch (cleanupErr) {
+      log('Failed to cleanup message after undo failure', { sessionId, messageId, error: String(cleanupErr) });
+    }
+    
+    // Return success since the message is removed from history
+    sendJson(res, 200, { ok: true, message: 'Undo completed (session reset)' });
   }
 }