diff --git a/apps/viewer/src/features/chat/api/legacy/sendMessageV1.ts b/apps/viewer/src/features/chat/api/legacy/sendMessageV1.ts
index 5da5b169a..d97418796 100644
--- a/apps/viewer/src/features/chat/api/legacy/sendMessageV1.ts
+++ b/apps/viewer/src/features/chat/api/legacy/sendMessageV1.ts
@@ -90,7 +90,7 @@ export const sendMessageV1 = publicProcedure
                       ? undefined
                       : startParams.typebot,
                   message,
-                  userId: parseUserId(user?.id),
+                  userId: user?.id,
                 }
               : {
                   type: 'live',
@@ -172,13 +172,3 @@ export const sendMessageV1 = publicProcedure
       }
     }
   )
-
-const parseUserId = (userId?: string): string => {
-  if (!userId)
-    throw new TRPCError({
-      code: 'UNAUTHORIZED',
-      message: 'You need to be authenticated to perform this action',
-    })
-
-  return userId
-}
diff --git a/apps/viewer/src/features/chat/api/legacy/sendMessageV2.ts b/apps/viewer/src/features/chat/api/legacy/sendMessageV2.ts
index 6d18c69b0..f39bf948c 100644
--- a/apps/viewer/src/features/chat/api/legacy/sendMessageV2.ts
+++ b/apps/viewer/src/features/chat/api/legacy/sendMessageV2.ts
@@ -90,7 +90,7 @@ export const sendMessageV2 = publicProcedure
                       ? undefined
                       : startParams.typebot,
                   message,
-                  userId: parseUserId(user?.id),
+                  userId: user?.id,
                 }
               : {
                   type: 'live',
@@ -172,13 +172,3 @@ export const sendMessageV2 = publicProcedure
       }
     }
   )
-
-const parseUserId = (userId?: string): string => {
-  if (!userId)
-    throw new TRPCError({
-      code: 'UNAUTHORIZED',
-      message: 'You need to be authenticated to perform this action',
-    })
-
-  return userId
-}
diff --git a/apps/viewer/src/features/chat/api/startChatPreview.ts b/apps/viewer/src/features/chat/api/startChatPreview.ts
index 43be02c7b..30ad7536f 100644
--- a/apps/viewer/src/features/chat/api/startChatPreview.ts
+++ b/apps/viewer/src/features/chat/api/startChatPreview.ts
@@ -1,4 +1,3 @@
-import { authenticatedProcedure } from '@/helpers/server/trpc'
 import {
   startPreviewChatInputSchema,
   startPreviewChatResponseSchema,
@@ -6,8 +5,9 @@ import {
 import { startSession } from '@typebot.io/bot-engine/startSession'
 import { saveStateToDatabase } from '@typebot.io/bot-engine/saveStateToDatabase'
 import { restartSession } from '@typebot.io/bot-engine/queries/restartSession'
+import { publicProcedure } from '@/helpers/server/trpc'
 
-export const startChatPreview = authenticatedProcedure
+export const startChatPreview = publicProcedure
   .meta({
     openapi: {
       method: 'POST',
@@ -47,7 +47,7 @@ export const startChatPreview = authenticatedProcedure
           startFrom,
           typebotId,
           typebot: startTypebot,
-          userId: user.id,
+          userId: user?.id,
         },
         message,
       })
diff --git a/apps/viewer/src/features/chat/api/updateTypebotInSession.ts b/apps/viewer/src/features/chat/api/updateTypebotInSession.ts
index 47901d7d5..a262950d1 100644
--- a/apps/viewer/src/features/chat/api/updateTypebotInSession.ts
+++ b/apps/viewer/src/features/chat/api/updateTypebotInSession.ts
@@ -1,3 +1,4 @@
+import { publicProcedure } from '@/helpers/server/trpc'
 import { TRPCError } from '@trpc/server'
 import { z } from 'zod'
 import { getSession } from '@typebot.io/bot-engine/queries/getSession'
@@ -8,9 +9,8 @@ import {
   Variable,
 } from '@typebot.io/schemas'
 import prisma from '@typebot.io/lib/prisma'
-import { authenticatedProcedure } from '@/helpers/server/trpc'
 
-export const updateTypebotInSession = authenticatedProcedure
+export const updateTypebotInSession = publicProcedure
   .meta({
     openapi: {
       method: 'POST',
@@ -28,6 +28,8 @@ export const updateTypebotInSession = authenticatedProcedure
   )
   .output(z.object({ message: z.literal('success') }))
   .mutation(async ({ input: { sessionId }, ctx: { user } }) => {
+    if (!user)
+      throw new TRPCError({ code: 'UNAUTHORIZED', message: 'Unauthorized' })
     const session = await getSession(sessionId)
     if (!session)
       throw new TRPCError({ code: 'NOT_FOUND', message: 'Session not found' })
diff --git a/apps/viewer/src/helpers/server/trpc.ts b/apps/viewer/src/helpers/server/trpc.ts
index 8f61174c2..0dfe8c66f 100644
--- a/apps/viewer/src/helpers/server/trpc.ts
+++ b/apps/viewer/src/helpers/server/trpc.ts
@@ -1,4 +1,4 @@
-import { TRPCError, initTRPC } from '@trpc/server'
+import { initTRPC } from '@trpc/server'
 import { OpenApiMeta } from 'trpc-openapi'
 import superjson from 'superjson'
 import { Context } from './context'
@@ -8,23 +8,13 @@ const t = initTRPC.context<Context>().meta<OpenApiMeta>().create({
   transformer: superjson,
 })
 
-export const router = t.router
-
 const sentryMiddleware = t.middleware(
   Sentry.Handlers.trpcMiddleware({
     attachRpcInput: true,
   })
 )
 
-export const publicProcedure = t.procedure.use(sentryMiddleware)
-
-const isAuthed = t.middleware(({ next, ctx }) => {
-  if (!ctx.user?.id) {
-    throw new TRPCError({
-      code: 'UNAUTHORIZED',
-      message: 'You need to be authenticated to perform this action',
-    })
-  }
+const injectUser = t.middleware(({ next, ctx }) => {
   return next({
     ctx: {
       user: ctx.user,
@@ -32,6 +22,10 @@ const isAuthed = t.middleware(({ next, ctx }) => {
   })
 })
 
-export const authenticatedProcedure = t.procedure.use(
-  sentryMiddleware.unstable_pipe(isAuthed)
-)
+const finalMiddleware = sentryMiddleware.unstable_pipe(injectUser)
+
+export const middleware = t.middleware
+
+export const router = t.router
+
+export const publicProcedure = t.procedure.use(finalMiddleware)
diff --git a/packages/bot-engine/startSession.ts b/packages/bot-engine/startSession.ts
index 2e72aa674..b19bc5f4d 100644
--- a/packages/bot-engine/startSession.ts
+++ b/packages/bot-engine/startSession.ts
@@ -39,7 +39,7 @@ import { VisitedEdge } from '@typebot.io/prisma'
 type StartParams =
   | ({
       type: 'preview'
-      userId: string
+      userId?: string
     } & StartPreviewChatInput)
   | ({
       type: 'live'
@@ -272,6 +272,13 @@ export const startSession = async ({
 const getTypebot = async (startParams: StartParams): Promise<StartTypebot> => {
   if (startParams.type === 'preview' && startParams.typebot)
     return startParams.typebot
+
+  if (startParams.type === 'preview' && !startParams.userId)
+    throw new TRPCError({
+      code: 'UNAUTHORIZED',
+      message: 'You need to be authenticated to perform this action',
+    })
+
   const typebotQuery =
     startParams.type === 'preview'
       ? await findTypebot({