fix(mothership): restore saved Plan chat history

Author: Sg312

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

@@ -477,6 +477,66 @@ async function waitFor(predicate: () => boolean, budgetMs = 2000): Promise<void>
 }
 
 describe('useChat remount send recovery', () => {
+  it('hydrates a saved Plan conversation on a cold mount without posting', async () => {
+    const messages = [
+      {
+        id: 'user-plan',
+        role: 'user',
+        content: 'Investigate incidents',
+        requestMode: 'plan',
+        timestamp: '2026-09-23T00:19:00Z',
+      },
+      {
+        id: 'assistant-plan',
+        role: 'assistant',
+        content: 'Saved investigation',
+        requestMode: 'plan',
+        timestamp: '2026-09-23T00:36:00Z',
+      },
+    ]
+    mockRequestJson.mockResolvedValue({
+      success: true,
+      chat: {
+        id: 'chat-plan',
+        mode: 'plan',
+        title: 'Incident triage',
+        messages,
+        activeStreamId: null,
+        resources: [],
+      },
+    })
+    const { getResult } = renderUseChatInChat('chat-plan')
+    await waitFor(() => !getResult().isChatHistoryPending)
+    expect(getResult().messages.map(({ id, content }) => ({ id, content }))).toEqual(
+      messages.map(({ id, content }) => ({ id, content }))
+    )
+    expect(getResult().error).toBeNull()
+    expect(state.postBodies).toHaveLength(0)
+  })
+
+  it('exposes a history load failure and clears it after a successful retry', async () => {
+    mockRequestJson.mockRejectedValue(new Error('History request failed'))
+    const { getResult } = renderUseChatInChat('chat-unavailable')
+    await waitFor(() => !getResult().isChatHistoryPending)
+    expect(getResult().error).toBe('Failed to load chat history. Refresh to try again.')
+    mockRequestJson.mockResolvedValue({
+      success: true,
+      chat: {
+        id: 'chat-unavailable',
+        mode: 'plan',
+        title: null,
+        messages: [],
+        activeStreamId: null,
+        resources: [],
+      },
+    })
+    await act(async () => {
+      await queryClient.refetchQueries({ queryKey: mothershipChatKeys.detail('chat-unavailable') })
+    })
+    await waitFor(() => getResult().error === null)
+    expect(state.postBodies).toHaveLength(0)
+  })
+
   it.each([
     ['agent', 'assistant'],
     ['assistant', 'agent'],

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

@@ -1238,8 +1238,11 @@ export function useChat(
     [flushPendingResources, queryClient, workspaceId, organizationId, scopeKey]
   )
 
-  const { data: chatHistory, isPending: isChatHistoryPending } =
-    useMothershipChatHistory(resolvedChatId)
+  const {
+    data: chatHistory,
+    isPending: isChatHistoryPending,
+    error: chatHistoryError,
+  } = useMothershipChatHistory(resolvedChatId)
   const requestModeRef = useRef<ChatRequestMode>(
     options?.requestMode ?? (organizationId ? 'assistant' : 'agent')
   )
@@ -4912,7 +4915,8 @@ export function useChat(
     isChatHistoryPending,
     isSending,
     isReconnecting,
-    error,
+    error:
+      error ?? (chatHistoryError ? 'Failed to load chat history. Refresh to try again.' : null),
     resolvedChatId,
     desktopScopeId,
     sendMessage,

apps/sim/hooks/queries/mothership-chats.test.ts

@@ -4,6 +4,7 @@
 
 import { sleep } from '@sim/utils/helpers'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { getMothershipChatResponseSchema } from '@/lib/api/contracts/mothership-chats'
 import type { MothershipResource } from '@/lib/mothership/resources/types'
 
 const { queryClient, suspendBrowserScope, suspendTerminalScope, clearChat } = vi.hoisted(() => ({
@@ -165,6 +166,77 @@ describe('tasks query boundary parsing', () => {
     })
   })
 
+  describe.each(['primary', 'fallback'] as const)('%s history endpoint', (endpoint) => {
+    it.each(getMothershipChatResponseSchema.shape.chat.shape.mode.options)(
+      'reopens a saved %s transcript without sending a new message',
+      async (mode) => {
+        const messages = [
+          {
+            id: 'user-1',
+            role: 'user',
+            content: 'Investigate incidents',
+            timestamp: '2026-09-23T00:19:00Z',
+            requestMode: mode,
+          },
+          {
+            id: 'assistant-1',
+            role: 'assistant',
+            content: 'Saved investigation',
+            timestamp: '2026-09-23T00:36:00Z',
+            requestMode: mode,
+          },
+        ]
+        if (endpoint === 'fallback') {
+          vi.mocked(fetch).mockResolvedValueOnce(new Response('Not found', { status: 404 }))
+        }
+        vi.mocked(fetch).mockResolvedValueOnce(
+          jsonResponse({
+            success: true,
+            chat: {
+              id: 'chat-plan',
+              mode,
+              title: 'Incident triage',
+              messages,
+              activeStreamId: null,
+              resources: [],
+            },
+          })
+        )
+
+        const history = await fetchMothershipChatHistory('chat-plan')
+
+        expect(history.mode).toBe(mode)
+        expect(history.messages).toEqual(
+          messages.map((message) => expect.objectContaining(message))
+        )
+        expect(fetch).toHaveBeenCalledTimes(endpoint === 'fallback' ? 2 : 1)
+        expect(
+          vi.mocked(fetch).mock.calls.every(([, init]) => !init?.method || init.method === 'GET')
+        ).toBe(true)
+      }
+    )
+
+    it('rejects an unknown conversation mode', async () => {
+      if (endpoint === 'fallback') {
+        vi.mocked(fetch).mockResolvedValueOnce(new Response('Not found', { status: 404 }))
+      }
+      vi.mocked(fetch).mockResolvedValueOnce(
+        jsonResponse({
+          success: true,
+          chat: {
+            id: 'chat-invalid',
+            mode: 'unknown',
+            title: null,
+            messages: [],
+            activeStreamId: null,
+            resources: [],
+          },
+        })
+      )
+      await expect(fetchMothershipChatHistory('chat-invalid')).rejects.toThrow()
+    })
+  })
+
   it('retains saved table views, file paths and execution identities when reading chat resources', async () => {
     const resources: MothershipResource[] = [
       { type: 'table', id: 'table-1', title: 'Invoices', viewId: 'overdue' },

apps/sim/hooks/queries/mothership-chats.ts

@@ -14,6 +14,7 @@ import {
   deleteMothershipChatContract,
   forkMothershipChatContract,
   getMothershipChatContract,
+  getMothershipChatResponseSchema,
   listMothershipChatsContract,
   type MothershipChat,
   type MothershipChatScope,
@@ -181,14 +182,11 @@ function parseChatHistory(value: unknown): MothershipChatHistory {
     `${chatContext}.activeStreamId must be a string or null`
   )
 
-  assertValid(
-    chat.mode === 'agent' || chat.mode === 'assistant',
-    `${chatContext}.mode must be agent or assistant`
-  )
+  const mode = getMothershipChatResponseSchema.shape.chat.shape.mode.parse(chat.mode)
 
   return {
     id: chat.id,
-    mode: chat.mode,
+    mode,
     title: chat.title,
     messages: normalizeMessages(chat.messages),
     activeStreamId: chat.activeStreamId,