Suddenly getting 'subscribe' can only be called a single time per channel instance` when deployed on Vercel

[Davedave2004]

Bug report

• I confirm this is a bug with Supabase, not with my own application.
• I confirm I have searched the Docs, GitHub Discussions, and Discord.

Describe the bug

Suddenly getting Tried to subscribe multiple times. 'subscribe' can only be called a single time per channel instance when deployed on Vercel. Works fine on local.

To Reproduce

Steps to reproduce the behavior, please provide code snippets or a repository:

1. Vercel deployment.
2. Use subscribe on useEffect
   Code Sample:

    useEffect(() => {
      refetch()


        const channel = supabase
          .channel('realtime:notification-channel')
          .on(
            'postgres_changes',
            { event: 'INSERT', schema: 'public', table: 'notifications' },
            (payload) => {
              if (user && user.id === payload.new.userId) {
                setUnseen(unseen + 1)
                refetch()
              }
            },
          )
          .subscribe()

        return () => {
          supabase.removeChannel(channel)
        }

    }, [])

Expected behavior

Doesn't crash the app.

System information

• Vercel deployment
• Version of supabase-js: [latest]
• Next.js version: 15.3.3

Additional context

• This wasn't throwing errors a few days before. I added a try catch block around it for now.
• I noticed removeChannel() returns a promise but subscribe() does not so it might be a race condition like subscribing before being removed. So I moved channel setup to an async function as well.
• Just want to confirm if the behavior recently changed (here or supabase realtime)

[markledwich2]

I also have started to see this.

UPDATE: i pulled up a hook that was subscribing to the same channel/filter from multiple components and that fixed it for me. I thought it was meant to handle that, but maybe there is a race condition.

[scoover]

I started seeing the same issue (works locally, fails on Vercel) around the same time. I wonder if it is a Vercel issue.

I had a build that was working great on June 5. I pushed a number of changes on June 8 and started seeing that error for the first time. I can't get anything after June 8 to run without the error and the Vercel build on June 5 runs great when I (re)promote it. I have tried rolling back all the changes little by little to match the June 5 build and I keep encountering the error. I wonder if the issue is that something changed in the way that Vercel is building.

It's frustrating as I'm not able to able to maintain or update my application until I get this sorted.

Will look again for duplicated listeners... but it is strange to see an error like this materialize with the same package versions.

[lineville]

I'm running into the same issue after upgrading from 2.48.1 to 2.50.0 so I had to revert. We're you able to find a workaround? It's possible this is an issue with the way this works within a react useEffect hook. For what it's worth I'm calling unsubscribe in the useEffect return rather than removeChannel, did that make a difference for you?

[Balamathias]

I am seeing a similar problem in my react native implementation, I am currently using 2.50.0:

useEffect(() => {
    if (!user) return

    const walletChannel = supabase.channel('wallet-update-channel')
      .on(
        'postgres_changes',
        { event: 'UPDATE', schema: 'public', table: 'wallet', filter: `user=eq.${user?.id}` },
        (payload) => {
          if (payload.new) {
            const response = payload?.new as Tables<'wallet'>
            setLocalWalletBalance(response.balance ?? 0)
            
            if (response.balance! > wallet?.balance!) {
              Toast.show({
                type: 'info',
                text1: 'Wallet funded successfully.'
              })
              Haptics.notificationAsync(Haptics.NotificationFeedbackType.Success)
            }

            queryClient.invalidateQueries({ queryKey: [QUERY_KEYS.getLatestTransactions] })
            queryClient.invalidateQueries({ queryKey: [QUERY_KEYS.getTransactions] })
            queryClient.invalidateQueries({ queryKey: [QUERY_KEYS.getWalletBalance] })
          }
        }
      )

    walletChannel.subscribe()

    // supabase.removeChannel(walletChannel)

    return () => { 
      supabase.removeChannel(walletChannel)
    }
  }, [user?.id, wallet?.balance])

[grdsdev]

Hi, we had a few changes on https://github.com/supabase/realtime-js/releases/tag/v2.11.8 that could impact this behavior, we'll be taking a look to check if there are any issues on our side.

Thanks.

[eyupk3]

Same problem.

"expo": "~53.0.10",
"@supabase/supabase-js": "^2.50.0",
"@tanstack/react-query": "^5.80.6",

[mayocream]

Same issue here.

    "@supabase/supabase-js": "^2.50.0",

[grdsdev]

Hi all, could you try out the v2.50.1-next.6 version and let me know if that fixes your issue?

Thanks.

[eyupk3]

Hi all, could you try out the v2.50.1-next.6 version and let me know if that fixes your issue?

Thanks.

Issue not resolved.

Warning: tried to subscribe multiple times. 'subscribe' can only be called a single time per channel instance

"expo": "53.0.12",
"@supabase/supabase-js": "^2.50.1-next.6",
"@tanstack/react-query": "^5.80.7",

My code

export const supabase = createClient(supabaseUrl, supabaseAnonKey, {
auth: {
storage: new LargeSecureStore(),
autoRefreshToken: true,
persistSession: true,
detectSessionInUrl: false,
},
});

useEffect(() => {
if (!userId) return;

const channelName = `test-channel`;

const subscription = supabase
  .channel(channelName)
  .on(
    "postgres_changes",
    {
      event: "UPDATE",
      schema: "public",
      table: "test",
      filter: `eq.user_id.${userId}`,
    },
    (payload) => {
      console.log("payload", payload);

      queryClient.invalidateQueries({
        queryKey: [queryKeys.test.all],
      });
    }
  )
  .subscribe();

return () => {
  supabase.removeChannel(subscription);
};

}, [userId]);

[grdsdev]

Hi this has been fixed on latest version of the library, please let me know if you're still facing this after update.