simstudioai · waleedlatif1 · Jul 13, 2026 · Jul 13, 2026
diff --git a/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/chat/chat.tsx b/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/chat/chat.tsx
@@ -401,9 +401,7 @@ export function Chat() {
 
   const workflowMessages = useMemo(() => {
     if (!activeWorkflowId) return []
-    return messages
-      .filter((msg) => msg.workflowId === activeWorkflowId)
-      .sort((a, b) => new Date(a.timestamp).getTime() - new Date(b.timestamp).getTime())
+    return messages.filter((msg) => msg.workflowId === activeWorkflowId)
   }, [messages, activeWorkflowId])
 
   const isStreaming = useMemo(() => {

diff --git a/apps/sim/stores/chat/store.test.ts b/apps/sim/stores/chat/store.test.ts
@@ -0,0 +1,68 @@
+/**
+ * @vitest-environment jsdom
+ */
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+vi.hoisted(() => {
+  const legacyNewestFirst = {
+    state: {
+      messages: [
+        {
+          id: 'msg-2',
+          content: 'response',
+          workflowId: 'wf-1',
+          type: 'workflow',
+          timestamp: '2026-07-13T00:00:00.000Z',
+        },
+        {
+          id: 'msg-1',
+          content: 'hi',
+          workflowId: 'wf-1',
+          type: 'user',
+          timestamp: '2026-07-13T00:00:00.000Z',
+        },
+      ],
+    },
+    version: 0,
+  }
+  window.localStorage.setItem('chat-store', JSON.stringify(legacyNewestFirst))
+})
+
+import { useChatStore } from '@/stores/chat/store'
+
+describe('chat store message ordering', () => {
+  it('migrates v0 persisted messages from newest-first to insertion order', () => {
+    const messages = useChatStore.getState().messages
+    expect(messages.map((m) => m.id)).toEqual(['msg-1', 'msg-2'])
+  })
+
+  describe('addMessage', () => {
+    beforeEach(() => {
+      useChatStore.setState({ messages: [] })
+    })
+
+    it('appends messages so insertion order is conversation order, even with identical timestamps', () => {
+      const { addMessage } = useChatStore.getState()
+      const timestamp = new Date().toISOString()
+
+      addMessage({ content: 'hi', workflowId: 'wf-1', type: 'user', timestamp } as any)
+      addMessage({ content: '', workflowId: 'wf-1', type: 'workflow', timestamp } as any)
+
+      const types = useChatStore.getState().messages.map((m) => m.type)
+      expect(types).toEqual(['user', 'workflow'])
+    })
+
+    it('keeps only the most recent messages when trimming to the cap', () => {
+      const { addMessage } = useChatStore.getState()
+
+      for (let i = 0; i < 55; i++) {
+        addMessage({ content: `m${i}`, workflowId: 'wf-1', type: 'user' })
+      }
+
+      const messages = useChatStore.getState().messages
+      expect(messages).toHaveLength(50)
+      expect(messages[0].content).toBe('m5')
+      expect(messages[messages.length - 1].content).toBe('m54')
+    })
+  })
+})
diff --git a/apps/sim/stores/chat/store.ts b/apps/sim/stores/chat/store.ts
@@ -63,7 +63,7 @@ export const useChatStore = create<ChatState>()(
               timestamp: (message as any).timestamp ?? new Date().toISOString(),
             }
 
-            const newMessages = [newMessage, ...state.messages].slice(0, MAX_MESSAGES)
+            const newMessages = [...state.messages, newMessage].slice(-MAX_MESSAGES)
 
             return { messages: newMessages }
           })
@@ -126,14 +126,9 @@ export const useChatStore = create<ChatState>()(
 
           const headers = ['timestamp', 'type', 'content']
 
-          const sortedMessages = [...messages].sort(
-            (a: ChatMessage, b: ChatMessage) =>
-              new Date(a.timestamp).getTime() - new Date(b.timestamp).getTime()
-          )
-
           const csvRows = [
             headers.join(','),
-            ...sortedMessages.map((message: ChatMessage) =>
+            ...messages.map((message: ChatMessage) =>
               [
                 formatCSVValue(message.timestamp),
                 formatCSVValue(message.type),
@@ -253,6 +248,21 @@ export const useChatStore = create<ChatState>()(
       }),
       {
         name: 'chat-store',
+        version: 1,
+        /**
+         * v0 stored messages newest-first; v1 stores them in insertion
+         * (chronological) order, which consumers render without sorting.
+         */
+        migrate: (persistedState, version) => {
+          if ((version ?? 0) < 1) {
+            const state = persistedState as { messages?: ChatMessage[] } | null
+            return {
+              ...state,
+              messages: [...(state?.messages ?? [])].reverse(),
+            }
+          }
+          return persistedState
+        },
         /**
          * Persist only the durable chat state — message history (with transient
          * blob `previewUrl`s stripped since they are not valid across reloads),