diff --git a/packages/stage-ui/src/stores/chat.ts b/packages/stage-ui/src/stores/chat.ts
index 20d8ef73d..358ae6263 100644
--- a/packages/stage-ui/src/stores/chat.ts
+++ b/packages/stage-ui/src/stores/chat.ts
@@ -136,6 +136,7 @@ export const useChatStore = defineStore('chat', () => {
       const newMessages = messages.value.slice(0, messages.value.length - 1).map((msg) => {
         if (msg.role === 'assistant') {
           const { slices: _, ...rest } = msg // exclude slices
+          rest.tool_results = toRaw(rest.tool_results)
           return toRaw(rest)
         }
         return toRaw(msg)