diff --git a/Package.swift b/Package.swift
index 0c2324c1..6105e5a6 100644
--- a/Package.swift
+++ b/Package.swift
@@ -137,6 +137,7 @@ let package = Package(
       name: "Supabase",
       dependencies: [
         .product(name: "ConcurrencyExtras", package: "swift-concurrency-extras"),
+        .product(name: "IssueReporting", package: "xctest-dynamic-overlay"),
         "Auth",
         "Functions",
         "PostgREST",
diff --git a/Sources/Supabase/SupabaseClient.swift b/Sources/Supabase/SupabaseClient.swift
index 632d63db..65218754 100644
--- a/Sources/Supabase/SupabaseClient.swift
+++ b/Sources/Supabase/SupabaseClient.swift
@@ -3,6 +3,7 @@ import ConcurrencyExtras
 import Foundation
 @_exported import Functions
 import Helpers
+import IssueReporting
 @_exported import PostgREST
 @_exported import Realtime
 @_exported import Storage
@@ -26,9 +27,18 @@ public final class SupabaseClient: Sendable {
   let databaseURL: URL
   let functionsURL: URL
 
-  /// Supabase Auth allows you to create and manage user sessions for access to data that is secured
-  /// by access policies.
-  public let auth: AuthClient
+  private let _auth: AuthClient
+
+  /// Supabase Auth allows you to create and manage user sessions for access to data that is secured by access policies.
+  public var auth: AuthClient {
+    if options.auth.accessToken != nil {
+      reportIssue("""
+      Supabase Client is configured with the auth.accessToken option,
+      accessing supabase.auth is not possible.
+      """)
+    }
+    return _auth
+  }
 
   var rest: PostgrestClient {
     mutableState.withValue {
@@ -105,7 +115,7 @@ public final class SupabaseClient: Sendable {
     var changedAccessToken: String?
   }
 
-  private let mutableState = LockIsolated(MutableState())
+  let mutableState = LockIsolated(MutableState())
 
   private var session: URLSession {
     options.global.session
@@ -153,7 +163,7 @@ public final class SupabaseClient: Sendable {
     // default storage key uses the supabase project ref as a namespace
     let defaultStorageKey = "sb-\(supabaseURL.host!.split(separator: ".")[0])-auth-token"
 
-    auth = AuthClient(
+    _auth = AuthClient(
       url: supabaseURL.appendingPathComponent("/auth/v1"),
       headers: _headers.dictionary,
       flowType: options.auth.flowType,
@@ -190,7 +200,9 @@ public final class SupabaseClient: Sendable {
       options: realtimeOptions
     )
 
-    listenForAuthEvents()
+    if options.auth.accessToken == nil {
+      listenForAuthEvents()
+    }
   }
 
   /// Performs a query on a table or a view.
@@ -240,9 +252,7 @@ public final class SupabaseClient: Sendable {
 
   /// Returns all Realtime channels.
   public var channels: [RealtimeChannelV2] {
-    get async {
-      await Array(realtimeV2.subscriptions.values)
-    }
+    Array(realtimeV2.subscriptions.values)
   }
 
   /// Creates a Realtime channel with Broadcast, Presence, and Postgres Changes.
@@ -252,8 +262,8 @@ public final class SupabaseClient: Sendable {
   public func channel(
     _ name: String,
     options: @Sendable (inout RealtimeChannelConfig) -> Void = { _ in }
-  ) async -> RealtimeChannelV2 {
-    await realtimeV2.channel(name, options: options)
+  ) -> RealtimeChannelV2 {
+    realtimeV2.channel(name, options: options)
   }
 
   /// Unsubscribes and removes Realtime channel from Realtime client.
@@ -340,9 +350,15 @@ public final class SupabaseClient: Sendable {
   }
 
   private func adapt(request: URLRequest) async -> URLRequest {
+    let token: String? = if let accessToken = options.auth.accessToken {
+      try? await accessToken()
+    } else {
+      try? await auth.session.accessToken
+    }
+
     var request = request
-    if let accessToken = try? await auth.session.accessToken {
-      request.setValue("Bearer \(accessToken)", forHTTPHeaderField: "Authorization")
+    if let token {
+      request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
     }
     return request
   }
diff --git a/Sources/Supabase/Types.swift b/Sources/Supabase/Types.swift
index 7c354d77..754515ca 100644
--- a/Sources/Supabase/Types.swift
+++ b/Sources/Supabase/Types.swift
@@ -60,6 +60,12 @@ public struct SupabaseClientOptions: Sendable {
     /// Set to `true` if you want to automatically refresh the token before expiring.
     public let autoRefreshToken: Bool
 
+    /// Optional function for using a third-party authentication system with Supabase. The function should return an access token or ID token (JWT) by obtaining it from the third-party auth client library.
+    /// Note that this function may be called concurrently and many times. Use memoization and locking techniques if this is not supported by the client libraries.
+    /// When set, the `auth` namespace of the Supabase client cannot be used.
+    /// Create another client if you wish to use Supabase Auth and third-party authentications concurrently in the same application.
+    public let accessToken: (@Sendable () async throws -> String)?
+
     public init(
       storage: any AuthLocalStorage,
       redirectToURL: URL? = nil,
@@ -67,7 +73,8 @@ public struct SupabaseClientOptions: Sendable {
       flowType: AuthFlowType = AuthClient.Configuration.defaultFlowType,
       encoder: JSONEncoder = AuthClient.Configuration.jsonEncoder,
       decoder: JSONDecoder = AuthClient.Configuration.jsonDecoder,
-      autoRefreshToken: Bool = AuthClient.Configuration.defaultAutoRefreshToken
+      autoRefreshToken: Bool = AuthClient.Configuration.defaultAutoRefreshToken,
+      accessToken: (@Sendable () async throws -> String)? = nil
     ) {
       self.storage = storage
       self.redirectToURL = redirectToURL
@@ -76,6 +83,7 @@ public struct SupabaseClientOptions: Sendable {
       self.encoder = encoder
       self.decoder = decoder
       self.autoRefreshToken = autoRefreshToken
+      self.accessToken = accessToken
     }
   }
 
@@ -154,7 +162,8 @@ extension SupabaseClientOptions.AuthOptions {
       flowType: AuthFlowType = AuthClient.Configuration.defaultFlowType,
       encoder: JSONEncoder = AuthClient.Configuration.jsonEncoder,
       decoder: JSONDecoder = AuthClient.Configuration.jsonDecoder,
-      autoRefreshToken: Bool = AuthClient.Configuration.defaultAutoRefreshToken
+      autoRefreshToken: Bool = AuthClient.Configuration.defaultAutoRefreshToken,
+      accessToken: (@Sendable () async throws -> String)? = nil
     ) {
       self.init(
         storage: AuthClient.Configuration.defaultLocalStorage,
@@ -163,7 +172,8 @@ extension SupabaseClientOptions.AuthOptions {
         flowType: flowType,
         encoder: encoder,
         decoder: decoder,
-        autoRefreshToken: autoRefreshToken
+        autoRefreshToken: autoRefreshToken,
+        accessToken: accessToken
       )
     }
   #endif
diff --git a/Supabase.xcworkspace/xcshareddata/swiftpm/Package.resolved b/Supabase.xcworkspace/xcshareddata/swiftpm/Package.resolved
index a3bc22bb..a0a59d70 100644
--- a/Supabase.xcworkspace/xcshareddata/swiftpm/Package.resolved
+++ b/Supabase.xcworkspace/xcshareddata/swiftpm/Package.resolved
@@ -1,5 +1,4 @@
 {
-  "originHash" : "7cc8037abb258fd1406effe711922c8d309c2e7a93147bfe68753fd05392a24a",
   "pins" : [
     {
       "identity" : "appauth-ios",
@@ -64,6 +63,24 @@
         "version" : "1.1.2"
       }
     },
+    {
+      "identity" : "swift-concurrency-extras",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/pointfreeco/swift-concurrency-extras",
+      "state" : {
+        "revision" : "bb5059bde9022d69ac516803f4f227d8ac967f71",
+        "version" : "1.1.0"
+      }
+    },
+    {
+      "identity" : "swift-crypto",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-crypto.git",
+      "state" : {
+        "revision" : "46072478ca365fe48370993833cb22de9b41567f",
+        "version" : "3.5.2"
+      }
+    },
     {
       "identity" : "swift-custom-dump",
       "kind" : "remoteSourceControl",
@@ -82,6 +99,15 @@
         "version" : "1.1.0"
       }
     },
+    {
+      "identity" : "swift-snapshot-testing",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/pointfreeco/swift-snapshot-testing",
+      "state" : {
+        "revision" : "c097f955b4e724690f0fc8ffb7a6d4b881c9c4e3",
+        "version" : "1.17.2"
+      }
+    },
     {
       "identity" : "swift-syntax",
       "kind" : "remoteSourceControl",
@@ -110,5 +136,5 @@
       }
     }
   ],
-  "version" : 3
+  "version" : 2
 }
diff --git a/Tests/SupabaseTests/SupabaseClientTests.swift b/Tests/SupabaseTests/SupabaseClientTests.swift
index 5864c0e6..d11a3e31 100644
--- a/Tests/SupabaseTests/SupabaseClientTests.swift
+++ b/Tests/SupabaseTests/SupabaseClientTests.swift
@@ -1,6 +1,7 @@
 @testable import Auth
 import CustomDump
 @testable import Functions
+import IssueReporting
 @testable import Realtime
 @testable import Supabase
 import XCTest
@@ -83,6 +84,11 @@ final class SupabaseClientTests: XCTestCase {
 
     XCTAssertFalse(client.auth.configuration.autoRefreshToken)
     XCTAssertEqual(client.auth.configuration.storageKey, "sb-project-ref-auth-token")
+
+    XCTAssertNotNil(
+      client.mutableState.listenForAuthEventsTask,
+      "should listen for internal auth events"
+    )
   }
 
   #if !os(Linux)
@@ -93,4 +99,31 @@ final class SupabaseClientTests: XCTestCase {
       )
     }
   #endif
+
+  func testClientInitWithCustomAccessToken() async {
+    let localStorage = AuthLocalStorageMock()
+
+    let client = SupabaseClient(
+      supabaseURL: URL(string: "https://project-ref.supabase.co")!,
+      supabaseKey: "ANON_KEY",
+      options: .init(
+        auth: .init(
+          storage: localStorage,
+          accessToken: { "jwt" }
+        )
+      )
+    )
+
+    XCTAssertNil(
+      client.mutableState.listenForAuthEventsTask,
+      "should not listen for internal auth events when using 3p authentication"
+    )
+
+    #if canImport(Darwin)
+      // withExpectedIssue is unavailable on non-Darwin platform.
+      withExpectedIssue {
+        _ = client.auth
+      }
+    #endif
+  }
 }