fix(chat): find a running turn's saved answer past its steering rows

A refetch mid-turn can return the saved answer after a steering row. Only the row
right after the owner was checked, so the live answer was added beside it and the
turn showed two answers until it ended. It now walks past steering rows with
findAssistantAfterOwner, as the reconcile path does.

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/home/hooks/message-reconcile.ts

@@ -248,7 +248,10 @@ export function findStreamOwnerIndex(messages: PersistedMessage[], streamId: str
 }
 
 /** The turn's response after its owner, past any steering the user sent into that turn. */
-export function findAssistantAfterOwner(messages: PersistedMessage[], ownerIndex: number): number {
+export function findAssistantAfterOwner(
+  messages: ReadonlyArray<Pick<PersistedMessage, 'role' | 'steering'>>,
+  ownerIndex: number
+): number {
   for (let index = ownerIndex + 1; index < messages.length; index++) {
     const message = messages[index]
     if (message.role === 'user' && !message.steering) return -1

apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.dom.test.tsx

@@ -4560,6 +4560,44 @@ describe('useChat remount send recovery', () => {
       }
     }, 30_000)
 
+    /** The server saved the turn's answer, after the steering row, before this surface saw it end. */
+    it('shows one answer when a refetch saves it after a steering row mid-turn', async () => {
+      const { view, turn } = await startTurn()
+      const at = '2026-11-05T00:00:00.000Z'
+      const saved: MothershipChatHistory = {
+        ...history,
+        messages: [
+          { id: turn.firstStreamId(), role: 'user', content: 'Count to fifty', timestamp: at },
+          {
+            id: 'steering-row',
+            role: 'user',
+            content: 'Stop at two',
+            timestamp: at,
+            steering: { streamId: turn.firstStreamId() },
+          },
+          {
+            id: 'saved-answer',
+            streamId: turn.firstStreamId(),
+            role: 'assistant',
+            content: '1 2.',
+            timestamp: at,
+          },
+        ],
+      }
+      await act(async () => {
+        queryClient.setQueryData(mothershipChatKeys.detail(chatId), saved)
+        await settle()
+      })
+
+      expect(view.getResult().isSending).toBe(true)
+      expect(
+        view
+          .getResult()
+          .messages.filter((message) => message.role === 'assistant')
+          .map((message) => message.id)
+      ).toEqual(['saved-answer'])
+    })
+
     const SUMMARY_SCOPE = { startDate: '2026-11-01T00:00:00.000Z' }
 
     it('holds a message with a search scope for its own turn, keeping the scope', async () => {

apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.ts

@@ -196,6 +196,7 @@ import type {
 import {
   buildAssistantSnapshotMessage,
   buildChatHistoryHydrationKey,
+  findAssistantAfterOwner,
   getReplayCompletedWorkflowToolCallIds,
   hasTerminalPersistedAssistantForStream,
   markMessageStopped,
@@ -1438,15 +1439,16 @@ export function useChat(
         ownerIndex = assistantIndex < 0 ? source.length : assistantIndex
         source.splice(ownerIndex, 0, pendingTurn.optimisticUserMessage)
       }
-      const assistant = source[ownerIndex + 1]
+      const assistantIndex = findAssistantAfterOwner(source, ownerIndex)
+      const assistant = assistantIndex < 0 ? undefined : source[assistantIndex]
       const liveAssistant = {
         ...pendingTurn.optimisticAssistantMessage,
         content: liveContent,
         contentBlocks: liveBlocks,
       }
       if (assistant?.id === pendingTurn.assistantMessageId) {
-        source[ownerIndex + 1] = { ...assistant, ...liveAssistant }
-      } else if (assistant?.role !== 'assistant') {
+        source[assistantIndex] = { ...assistant, ...liveAssistant }
+      } else if (!assistant) {
         source.splice(ownerIndex + 1, 0, liveAssistant)
       }
     }