diff --git a/packages/core/supabase-js/src/SupabaseClient.ts b/packages/core/supabase-js/src/SupabaseClient.ts
index 3c2125ce5..71c8b30d3 100644
--- a/packages/core/supabase-js/src/SupabaseClient.ts
+++ b/packages/core/supabase-js/src/SupabaseClient.ts
@@ -156,6 +156,14 @@ export default class SupabaseClient<
       accessToken: this._getAccessToken.bind(this),
       ...settings.realtime,
     })
+    if (this.accessToken) {
+      setTimeout(() => {
+        this.accessToken?.()
+          ?.then((token) => this.realtime.setAuth(token))
+          .catch((e) => console.warn('Failed to set initial Realtime auth token:', e))
+      }, 0)
+    }
+
     this.rest = new PostgrestClient(new URL('rest/v1', baseUrl).href, {
       headers: this.headers,
       schema: settings.db.schema,
diff --git a/packages/core/supabase-js/test/integration.test.ts b/packages/core/supabase-js/test/integration.test.ts
index d9553405b..387849d74 100644
--- a/packages/core/supabase-js/test/integration.test.ts
+++ b/packages/core/supabase-js/test/integration.test.ts
@@ -1,12 +1,13 @@
+import { assert } from 'console'
 import { createClient, RealtimeChannel, SupabaseClient } from '../src/index'
-
+import { sign } from 'jsonwebtoken'
 // These tests assume that a local Supabase server is already running
 // Start a local Supabase instance with 'supabase start' before running these tests
 // Default local dev credentials from Supabase CLI
 const SUPABASE_URL = 'http://127.0.0.1:54321'
 const ANON_KEY =
   'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJzdXBhYmFzZS1kZW1vIiwicm9sZSI6ImFub24iLCJleHAiOjE5ODM4MTI5OTZ9.CRXP1A7WOeoJeXxjNni43kdQwgnWNReilDMblYTn_I0'
-
+const JWT_SECRET = 'super-secret-jwt-token-with-at-least-32-characters-long'
 // For Node.js < 22, we need to provide a WebSocket implementation
 // Node.js 22+ has native WebSocket support
 let wsTransport: any = undefined
@@ -292,7 +293,7 @@ describe('Supabase Integration Tests', () => {
 
       channel
         .on('broadcast', { event: '*' }, (payload) => (receivedMessage = payload))
-        .subscribe((status) => {
+        .subscribe((status, err) => {
           if (status == 'SUBSCRIBED') subscribed = true
         })
 
@@ -358,3 +359,31 @@ describe('Storage API', () => {
     expect(deleteError).toBeNull()
   })
 })
+
+describe('Custom JWT', () => {
+  describe('Realtime', () => {
+    test('will connect with a properly signed jwt token', async () => {
+      const jwtToken = sign({ sub: '1234567890' }, JWT_SECRET, { expiresIn: '1h' })
+      const supabaseWithCustomJwt = createClient(SUPABASE_URL, ANON_KEY, {
+        accessToken: () => Promise.resolve(jwtToken),
+      })
+      await new Promise((resolve) => setTimeout(resolve, 100))
+      expect(supabaseWithCustomJwt.realtime.accessTokenValue).toBe(jwtToken)
+      let subscribed = false
+      let attempts = 0
+      supabaseWithCustomJwt.channel('test-channel').subscribe((status) => {
+        if (status == 'SUBSCRIBED') subscribed = true
+      })
+
+      // Wait for subscription
+      while (!subscribed) {
+        if (attempts > 50) throw new Error('Timeout waiting for subscription')
+        await new Promise((resolve) => setTimeout(resolve, 100))
+        attempts++
+      }
+
+      expect(subscribed).toBe(true)
+      //
+    }, 10000)
+  })
+})
diff --git a/packages/core/supabase-js/test/unit/SupabaseClient.test.ts b/packages/core/supabase-js/test/unit/SupabaseClient.test.ts
index 6f7304114..edaf33c88 100644
--- a/packages/core/supabase-js/test/unit/SupabaseClient.test.ts
+++ b/packages/core/supabase-js/test/unit/SupabaseClient.test.ts
@@ -259,6 +259,61 @@ describe('SupabaseClient', () => {
     })
 
     describe('Realtime Authentication', () => {
+      test('should automatically call setAuth() when accessToken option is provided', async () => {
+        const customToken = 'custom-jwt-token'
+        const customAccessTokenFn = jest.fn().mockResolvedValue(customToken)
+        const client = createClient(URL, KEY, { accessToken: customAccessTokenFn })
+
+        await new Promise((resolve) => setTimeout(resolve, 0))
+
+        expect((client.realtime as any).accessTokenValue).toBe(customToken)
+        expect(customAccessTokenFn).toHaveBeenCalled()
+      })
+
+      test('should automatically populate token in channels when using custom JWT', async () => {
+        const customToken = 'custom-channel-token'
+        const customAccessTokenFn = jest.fn().mockResolvedValue(customToken)
+        const client = createClient(URL, KEY, { accessToken: customAccessTokenFn })
+
+        await new Promise((resolve) => setTimeout(resolve, 0))
+
+        const channel = client.channel('test-channel')
+        channel.subscribe()
+
+        expect((channel as any).joinPush.payload.access_token).toBe(customToken)
+        expect((client.realtime as any).accessTokenValue).toBe(customToken)
+      })
+
+      test('should handle errors gracefully when accessToken callback fails', async () => {
+        const consoleWarnSpy = jest.spyOn(console, 'warn').mockImplementation(() => {})
+        const error = new Error('Token fetch failed')
+        const failingAccessTokenFn = jest.fn().mockRejectedValue(error)
+
+        const client = createClient(URL, KEY, { accessToken: failingAccessTokenFn })
+
+        await new Promise((resolve) => setTimeout(resolve, 0))
+
+        expect(consoleWarnSpy).toHaveBeenCalledWith(
+          'Failed to set initial Realtime auth token:',
+          error
+        )
+        expect(client).toBeDefined()
+        expect(client.realtime).toBeDefined()
+
+        consoleWarnSpy.mockRestore()
+      })
+
+      test('should not call setAuth() automatically in normal mode', async () => {
+        const client = createClient(URL, KEY)
+        const setAuthSpy = jest.spyOn(client.realtime, 'setAuth')
+
+        await new Promise((resolve) => setTimeout(resolve, 10))
+
+        expect(setAuthSpy).not.toHaveBeenCalled()
+
+        setAuthSpy.mockRestore()
+      })
+
       test('should provide access token to realtime client', async () => {
         const expectedToken = 'test-jwt-token'
         const client = createClient(URL, KEY)
diff --git a/supabase/.branches/_current_branch b/supabase/.branches/_current_branch
new file mode 100644
index 000000000..88d050b19
--- /dev/null
+++ b/supabase/.branches/_current_branch
@@ -0,0 +1 @@
+main
\ No newline at end of file
diff --git a/supabase/.temp/cli-latest b/supabase/.temp/cli-latest
new file mode 100644
index 000000000..11335d2f8
--- /dev/null
+++ b/supabase/.temp/cli-latest
@@ -0,0 +1 @@
+v2.54.11
\ No newline at end of file