fix(invitations): surface the accept conflict message and refresh workspace caches post-accept

The accept route now carries the human-readable message alongside the
machine-readable error kind (the client prefers it for server-error), and
a successful accept invalidates workspace queries so the swept workspaces
appear immediately instead of after the stale window.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: icecrasher321

apps/sim/app/api/invitations/[id]/accept/route.ts

@@ -45,7 +45,13 @@ export const POST = withRouteHandler(
       }
       const status = statusMap[result.kind] ?? 500
       logger.warn('Invitation accept rejected', { invitationId: id, reason: result.kind })
-      return NextResponse.json({ error: result.kind }, { status })
+      /**
+       * `error` stays the machine-readable kind (the client maps it to UX
+       * states); `message` carries the human copy when the failure provides
+       * one — e.g. the retryable concurrent-workspace-change conflict.
+       */
+      const message = result.kind === 'server-error' ? result.message : undefined
+      return NextResponse.json({ error: result.kind, ...(message ? { message } : {}) }, { status })
     }
 
     const inv = result.invitation

apps/sim/app/invite/[id]/invite.test.tsx

@@ -281,6 +281,6 @@ describe('Invite', () => {
       cache: 'session',
       error: 'Session refresh denied',
     })
-    expect(mockLogger.warn).toHaveBeenCalledTimes(3)
+    expect(mockLogger.warn).toHaveBeenCalledTimes(4)
   })
 })

apps/sim/app/invite/[id]/invite.tsx

@@ -18,6 +18,7 @@ import { useInvitationDetails } from '@/hooks/queries/invitations'
 import { organizationKeys } from '@/hooks/queries/organization'
 import { refreshSessionQuery } from '@/hooks/queries/session'
 import { subscriptionKeys } from '@/hooks/queries/subscription'
+import { workspaceKeys } from '@/hooks/queries/workspace'
 
 const logger = createLogger('InviteById')
 
@@ -274,13 +275,32 @@ export default function Invite() {
       runBestEffortCacheRefresh('organization', () =>
         queryClient.invalidateQueries({ queryKey: organizationKeys.all })
       )
+      /**
+       * Acceptance can attach the invitee's owned workspaces into the org —
+       * the workspace list must not keep serving the stale personal set.
+       */
+      runBestEffortCacheRefresh('workspaces', () =>
+        queryClient.invalidateQueries({ queryKey: workspaceKeys.all })
+      )
     } catch (acceptError) {
       logger.error('Error accepting invitation:', acceptError)
       const code =
         acceptError instanceof ApiClientError
           ? codeFromApiClientError(acceptError)
           : 'network-error'
-      setActionError(getInviteError(code))
+      const serverMessage =
+        acceptError instanceof ApiClientError &&
+        acceptError.body &&
+        typeof acceptError.body === 'object' &&
+        typeof (acceptError.body as { message?: unknown }).message === 'string'
+          ? ((acceptError.body as { message: string }).message as string)
+          : null
+      const baseError = getInviteError(code)
+      setActionError(
+        code === 'server-error' && serverMessage
+          ? { ...baseError, message: serverMessage }
+          : baseError
+      )
       setIsAccepting(false)
     }
   }