diff --git a/GliaWidgets/Public/Glia/Glia+StartEngagement.swift b/GliaWidgets/Public/Glia/Glia+StartEngagement.swift
index 616d4581c..ead149757 100644
--- a/GliaWidgets/Public/Glia/Glia+StartEngagement.swift
+++ b/GliaWidgets/Public/Glia/Glia+StartEngagement.swift
@@ -18,7 +18,7 @@ extension Glia {
     ///   - `GliaError.engagementExists
     ///   - `GliaError.sdkIsNotConfigured`
     ///
-    /// - Important: Note, that `configure(with:queueID:visitorContext:)` must be called initially prior to this method,
+    /// - Important: Note, that `configure(with:uiConfig:assetsBuilder:completion:)` must be called initially prior to this method,
     /// because `GliaError.sdkIsNotConfigured` will occur otherwise.
     ///
     public func startEngagement(
@@ -28,7 +28,10 @@ extension Glia {
         features: Features = .all,
         sceneProvider: SceneProvider? = nil
     ) throws {
-        guard !queueIds.isEmpty else { throw GliaError.startingEngagementWithNoQueueIdsIsNotAllowed }
+        let trimmedQueueIds = queueIds
+            .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
+            .filter { !$0.isEmpty }
+        guard !trimmedQueueIds.isEmpty else { throw GliaError.startingEngagementWithNoQueueIdsIsNotAllowed }
         guard engagement == .none else { throw GliaError.engagementExists }
         guard let configuration = self.configuration else { throw GliaError.sdkIsNotConfigured }
         if let engagement = environment.coreSdk.getCurrentEngagement(),
@@ -39,7 +42,7 @@ extension Glia {
         // Creates interactor instance
         let createdInteractor = setupInteractor(
             configuration: configuration,
-            queueIds: queueIds
+            queueIds: trimmedQueueIds
         )
 
         theme.chat.connect.queue.firstText = companyName(
diff --git a/GliaWidgets/Public/Glia/Glia.Deprecated.swift b/GliaWidgets/Public/Glia/Glia.Deprecated.swift
index 5675af6f5..dda59f821 100644
--- a/GliaWidgets/Public/Glia/Glia.Deprecated.swift
+++ b/GliaWidgets/Public/Glia/Glia.Deprecated.swift
@@ -2,7 +2,7 @@ import GliaCoreSDK
 
 extension Glia {
     /// Deprecated.
-    @available(*, unavailable, message: "Use configure(with:queueId:uiConfig:assetsBuilder:completion:) instead.")
+    @available(*, unavailable, message: "Use configure(with:uiConfig:assetsBuilder:completion:) instead.")
     public func configure(
         with configuration: Configuration,
         queueId: String,
@@ -184,6 +184,27 @@ extension Glia {
             sceneProvider: sceneProvider
         )
     }
+
+    /// Deprecated, use the `configure` method that provides a `Result` in its completion instead.
+    @available(*, deprecated, message: "Use the `configure` method that provides a `Result` in its completion instead.")
+    public func configure(
+        with configuration: Configuration,
+        uiConfig: RemoteConfiguration? = nil,
+        assetsBuilder: RemoteConfiguration.AssetsBuilder = .standard,
+        completion: (() -> Void)? = nil
+    ) throws {
+        try configure(
+            with: configuration,
+            uiConfig: uiConfig,
+            assetsBuilder: assetsBuilder
+        ) { result in
+            defer {
+                completion?()
+            }
+            guard case let .failure(error) = result else { return }
+            debugPrint("💥 Core SDK configuration is not valid. Unexpected error='\(error)'.")
+        }
+    }
 }
 
 extension Glia.Authentication {
diff --git a/GliaWidgets/Public/Glia/Glia.RemoteConfiguration.swift b/GliaWidgets/Public/Glia/Glia.RemoteConfiguration.swift
index 9341f171c..d4d42fb32 100644
--- a/GliaWidgets/Public/Glia/Glia.RemoteConfiguration.swift
+++ b/GliaWidgets/Public/Glia/Glia.RemoteConfiguration.swift
@@ -18,7 +18,7 @@ extension Glia {
     ///   - `GliaError.engagementExists
     ///   - `GliaError.sdkIsNotConfigured`
     ///
-    /// - Important: Note, that `configure(with:queueID:visitorContext:)` must be called initially prior to this method,
+    /// - Important: Note, that `configure(with:uiConfig:assetsBuilder:completion:)` must be called initially prior to this method,
     /// because `GliaError.sdkIsNotConfigured` will occur otherwise.
     ///
     public func startEngagementWithConfig(
diff --git a/GliaWidgets/Public/Glia/Glia.swift b/GliaWidgets/Public/Glia/Glia.swift
index 31ce3b2f6..f0ec3cbe8 100644
--- a/GliaWidgets/Public/Glia/Glia.swift
+++ b/GliaWidgets/Public/Glia/Glia.swift
@@ -104,23 +104,25 @@ public class Glia {
     /// Setup SDK using specific engagement configuration without starting the engagement.
     /// - Parameters:
     ///   - configuration: Engagement configuration.
-    ///   - visitorContext: Visitor context.
     ///   - uiConfig: Remote UI configuration.
     ///   - assetsBuilder: Provides assets for remote configuration.
-    ///   - completion: Optional completion handler that will be fired once configuration is complete.
-    ///   Passing  `nil` will defer configuration. Passing closure will start configuration immediately.
+    ///   - completion: Completion handler that will be fired once configuration is complete.
     public func configure(
         with configuration: Configuration,
         uiConfig: RemoteConfiguration? = nil,
         assetsBuilder: RemoteConfiguration.AssetsBuilder = .standard,
-        completion: (() -> Void)? = nil
+        completion: @escaping (Result<Void, Error>) -> Void
     ) throws {
         guard environment.coreSdk.getCurrentEngagement() == nil else {
             throw GliaError.configuringDuringEngagementIsNotAllowed
         }
         self.uiConfig = uiConfig
         self.assetsBuilder = assetsBuilder
-        self.configuration = configuration
+        // `configuration` should be erased to avoid cases when integrators
+        // call `configure` and `startEngagement` asynchronously, and
+        // second-time configuration has not been complete, but `startEngagement`
+        // is fired and SDK has previous `configuration`.
+        self.configuration = nil
 
         self.callVisualizer.delegate = { action in
             switch action {
@@ -129,10 +131,15 @@ public class Glia {
             }
         }
 
-        // TODO: - Non-optional completion will be added in MOB-2784
-        do {
-            try environment.coreSDKConfigurator.configureWithConfiguration(configuration) { [weak self] in
-                guard let self else { return }
+        try environment.coreSDKConfigurator.configureWithConfiguration(configuration) { [weak self] result in
+            guard let self else { return }
+            switch result {
+            case .success:
+                // Storing `configuration` needs to be done once configuring SDK is complete
+                // Otherwise integrator can call `configure` and `startEngagement`
+                // asynchronously, without waiting configuration completion.
+                self.configuration = configuration
+
                 let getRemoteString = self.environment.coreSdk.localeProvider.getRemoteString
                 self.stringProviding = .init(getRemoteString: getRemoteString)
 
@@ -141,11 +148,11 @@ public class Glia {
                     self.setupInteractor(configuration: configuration)
                 }
 
-                completion?()
+                completion(.success(()))
+            case let .failure(error):
+                debugPrint("💥 Core SDK configuration is not valid. Unexpected error='\(error)'.")
+                completion(.failure(error))
             }
-        } catch {
-            self.configuration = nil
-            debugPrint("💥 Core SDK configuration is not valid. Unexpected error='\(error)'.")
         }
     }
 
@@ -208,11 +215,11 @@ public class Glia {
     /// - `GliaCoreSDK.ConfigurationError.invalidEnvironment`
     /// - `GliaError.sdkIsNotConfigured`
     ///
-    /// - Important: Note, that in case of engagement has not been started yet, `configure(with:queueID:visitorContext:)` must be called initially prior to this method,
+    /// - Important: Note, that in case of engagement has not been started yet, `configure(with:uiConfig:assetsBuilder:completion:)` must be called initially prior to this method,
     /// because `GliaError.sdkIsNotConfigured` will occur otherwise.
     ///
     public func fetchVisitorInfo(completion: @escaping (Result<GliaCore.VisitorInfo, Error>) -> Void) {
-        guard interactor != nil else {
+        guard configuration != nil else {
             completion(.failure(GliaError.sdkIsNotConfigured))
             return
         }
@@ -242,14 +249,14 @@ public class Glia {
     /// - `GliaCoreSDK.ConfigurationError.invalidEnvironment`
     /// - `GliaError.sdkIsNotConfigured`
     ///
-    /// - Important: Note, that in case of engagement has not been started yet, `configure(with:queueID:visitorContext:)` must be called initially prior to this method,
+    /// - Important: Note, that in case of engagement has not been started yet, `configure(with:uiConfig:assetsBuilder:completion:)` must be called initially prior to this method,
     /// because `GliaError.sdkIsNotConfigured` will occur otherwise.
     ///
     public func updateVisitorInfo(
         _ info: VisitorInfoUpdate,
         completion: @escaping (Result<Bool, Error>) -> Void
     ) {
-        guard interactor != nil else {
+        guard configuration != nil else {
             completion(.failure(GliaError.sdkIsNotConfigured))
             return
         }
@@ -263,7 +270,7 @@ public class Glia {
             rootCoordinator = nil
         }
 
-        guard interactor != nil else {
+        guard configuration != nil else {
             completion(.failure(GliaError.sdkIsNotConfigured))
             return
         }
@@ -278,10 +285,10 @@ public class Glia {
     /// It is also possible to monitor Queues changes with [subscribeForUpdates](x-source-tag://subscribeForUpdates) method.
     /// If the request is unsuccessful for any reason then the completion will have an Error.
     /// - Parameters:
-    ///   - completion: A callback that will return the Result struct with `Queue` list or `GliaCoreError`
+    ///   - completion: A callback that will return the Result struct with `Queue` list or `GliaCoreError`.
     ///
     public func listQueues(_ completion: @escaping (Result<[Queue], Error>) -> Void) {
-        guard interactor != nil else {
+        guard configuration != nil else {
             completion(.failure(GliaError.sdkIsNotConfigured))
             return
         }
diff --git a/GliaWidgets/Sources/CoreSDKClient/CoreSDKClient.Interface.swift b/GliaWidgets/Sources/CoreSDKClient/CoreSDKClient.Interface.swift
index cb14acb1c..d734c0285 100644
--- a/GliaWidgets/Sources/CoreSDKClient/CoreSDKClient.Interface.swift
+++ b/GliaWidgets/Sources/CoreSDKClient/CoreSDKClient.Interface.swift
@@ -19,7 +19,7 @@ struct CoreSdkClient {
 
     typealias ConfigureWithConfiguration = (
         _ sdkConfiguration: Self.Salemove.Configuration,
-        _ completion: (() -> Void)?
+        _ completion: @escaping Self.ConfigureCompletion
     ) -> Void
     var configureWithConfiguration: ConfigureWithConfiguration
 
@@ -249,4 +249,5 @@ extension CoreSdkClient {
     typealias Cancellable = GliaCore.Cancellable
     typealias ReactiveSwift = GliaCoreDependency.ReactiveSwift
     typealias SendMessagePayload = GliaCoreSDK.SendMessagePayload
+    typealias ConfigureCompletion = GliaCoreSDK.GliaCore.ConfigureCompletion
 }
diff --git a/GliaWidgets/Sources/CoreSDKConfigurator/CoreSDKConfigurator.Interface.swift b/GliaWidgets/Sources/CoreSDKConfigurator/CoreSDKConfigurator.Interface.swift
index 80f5fed8d..3fa83ef96 100644
--- a/GliaWidgets/Sources/CoreSDKConfigurator/CoreSDKConfigurator.Interface.swift
+++ b/GliaWidgets/Sources/CoreSDKConfigurator/CoreSDKConfigurator.Interface.swift
@@ -2,7 +2,7 @@ import Foundation
 
 struct CoreSDKConfigurator {
     var configureWithInteractor: CoreSdkClient.ConfigureWithInteractor
-    var configureWithConfiguration: (Configuration, (() -> Void)?) throws -> Void
+    var configureWithConfiguration: (Configuration, @escaping (Result<Void, Error>) -> Void) throws -> Void
 }
 
 extension CoreSDKConfigurator {
@@ -16,9 +16,7 @@ extension CoreSDKConfigurator {
                     authorizingMethod: configuration.authorizationMethod.coreAuthorizationMethod,
                     pushNotifications: configuration.pushNotifications.coreSdk
                 )
-                coreSdk.configureWithConfiguration(sdkConfiguration) {
-                    completion?()
-                }
+                coreSdk.configureWithConfiguration(sdkConfiguration, completion)
             }
         )
     }
diff --git a/GliaWidgets/Sources/ViewController/Call/CallViewController.Mock.swift b/GliaWidgets/Sources/ViewController/Call/CallViewController.Mock.swift
index 3a0983729..c4f6cdf3f 100644
--- a/GliaWidgets/Sources/ViewController/Call/CallViewController.Mock.swift
+++ b/GliaWidgets/Sources/ViewController/Call/CallViewController.Mock.swift
@@ -86,7 +86,7 @@ extension CallViewController {
         let queueId = UUID.mock.uuidString
         var interactorEnv = Interactor.Environment.mock
         interactorEnv.coreSdk.configureWithConfiguration = { _, callback in
-            callback?()
+            callback(.success(()))
         }
         let interactor = Interactor.mock(
             queueId: queueId,
diff --git a/GliaWidgets/Sources/ViewController/Chat/ChatViewController.Mock.swift b/GliaWidgets/Sources/ViewController/Chat/ChatViewController.Mock.swift
index a4fb31855..d6ef76044 100644
--- a/GliaWidgets/Sources/ViewController/Chat/ChatViewController.Mock.swift
+++ b/GliaWidgets/Sources/ViewController/Chat/ChatViewController.Mock.swift
@@ -199,7 +199,7 @@ extension ChatViewController {
         chatViewModelEnv.fetchChatHistory = { $0(.success([])) }
         var interEnv = Interactor.Environment.mock
         interEnv.coreSdk.configureWithConfiguration = { _, callback in
-            callback?()
+            callback(.success(()))
         }
         let interactor = Interactor.mock(environment: interEnv)
         let generateUUID = UUID.incrementing
@@ -540,7 +540,7 @@ extension ChatViewController {
         chatViewModelEnv.fetchChatHistory = { $0(.success(messages)) }
         var interEnv = Interactor.Environment.mock
         interEnv.coreSdk.configureWithConfiguration = { _, callback in
-            callback?()
+            callback(.success(()))
         }
         let interactor = Interactor.mock(environment: interEnv)
         let chatViewModel = ChatViewModel.mock(interactor: interactor, environment: chatViewModelEnv)
diff --git a/GliaWidgetsTests/Sources/ChatViewModel/ChatViewModelTests.swift b/GliaWidgetsTests/Sources/ChatViewModel/ChatViewModelTests.swift
index fd7479211..6b289fa2a 100644
--- a/GliaWidgetsTests/Sources/ChatViewModel/ChatViewModelTests.swift
+++ b/GliaWidgetsTests/Sources/ChatViewModel/ChatViewModelTests.swift
@@ -367,7 +367,7 @@ class ChatViewModelTests: XCTestCase {
         // we use the mocked one, which doesn't execute the completion,
         // `sendMessageWithAttachment` will not be executed.
         environment.coreSdk.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
 
         let viewModel: ChatViewModel = .mock(
@@ -595,7 +595,7 @@ class ChatViewModelTests: XCTestCase {
         let interactor = Interactor.failing
         interactor.environment.gcd.mainQueue.asyncIfNeeded = { $0() }
         interactor.environment.coreSdk.configureWithInteractor = { _ in }
-        interactor.environment.coreSdk.configureWithConfiguration = { _, callback in callback?() }
+        interactor.environment.coreSdk.configureWithConfiguration = { _, callback in callback(.success(())) }
         interactor.environment.coreSdk.sendMessagePreview = { _, _ in }
         interactor.environment.coreSdk.sendMessageWithMessagePayload = { _, completion in
             completion(.success(.mock(id: expectedMessageId)))
@@ -645,7 +645,7 @@ class ChatViewModelTests: XCTestCase {
         let interactor = Interactor.failing
         interactor.environment.gcd.mainQueue.asyncIfNeeded = { $0() }
         interactor.environment.coreSdk.configureWithInteractor = { _ in }
-        interactor.environment.coreSdk.configureWithConfiguration = { _, callback in callback?() }
+        interactor.environment.coreSdk.configureWithConfiguration = { _, callback in callback(.success(())) }
         interactor.environment.coreSdk.sendMessagePreview = { _, _ in }
         interactor.environment.coreSdk.sendMessageWithMessagePayload = { [weak viewModel] _, completion in
             // Deliver message via socket before REST API response.
diff --git a/GliaWidgetsTests/Sources/Glia/GliaTests+StartEngagement.swift b/GliaWidgetsTests/Sources/Glia/GliaTests+StartEngagement.swift
index cd49506ad..babd2907d 100644
--- a/GliaWidgetsTests/Sources/Glia/GliaTests+StartEngagement.swift
+++ b/GliaWidgetsTests/Sources/Glia/GliaTests+StartEngagement.swift
@@ -11,7 +11,7 @@ extension GliaTests {
     func testStartEngagementThrowsErrorWhenEngagementAlreadyExists() throws {
         var sdkEnv = Glia.Environment.failing
         sdkEnv.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         let sdk = Glia(environment: sdkEnv)
         sdk.rootCoordinator = .mock(engagementKind: .chat, screenShareHandler: .mock)
@@ -30,9 +30,9 @@ extension GliaTests {
     func testStartEngagementThrowsErrorDuringActiveCallVisualizerEngagement() throws {
         let sdk = Glia(environment: .failing)
         sdk.environment.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
-        try sdk.configure(with: .mock())
+        try sdk.configure(with: .mock()) {}
         sdk.environment.coreSdk.getCurrentEngagement = { .mock(source: .callVisualizer) }
 
         XCTAssertThrowsError(
@@ -67,7 +67,7 @@ extension GliaTests {
         }
         environment.coreSDKConfigurator.configureWithConfiguration = { _, completion in
             calls.append(.configureWithConfiguration)
-            completion?()
+            completion(.success(()))
         }
         environment.coreSdk.localeProvider.getRemoteString = { _ in nil }
         environment.createRootCoordinator = { _, _, _, _, _, _, _ in
@@ -99,7 +99,7 @@ extension GliaTests {
             )
         }
         environment.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         environment.coreSDKConfigurator.configureWithInteractor = { _ in }
         environment.coreSdk.localeProvider.getRemoteString = { _ in nil }
@@ -110,8 +110,13 @@ extension GliaTests {
         theme.call.connect.queue.firstText = "Glia 1"
         theme.chat.connect.queue.firstText = "Glia 2"
 
-        try sdk.configure(with: .mock())
-        try sdk.startEngagement(engagementKind: .chat, in: ["queueId"], theme: theme)
+        try sdk.configure(with: .mock()) {
+            do {
+                try sdk.startEngagement(engagementKind: .chat, in: ["queueId"], theme: theme)
+            } catch {
+                XCTFail("startEngagement unexpectedly failed with error \(error), but should succeed instead.")
+            }
+        }
 
         let configuredSdkTheme = resultingViewFactory?.theme
         XCTAssertEqual(configuredSdkTheme?.call.connect.queue.firstText, "Glia 1")
@@ -138,7 +143,7 @@ extension GliaTests {
 
         environment.coreSdk.localeProvider.getRemoteString = { _ in "Glia" }
         environment.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         environment.coreSDKConfigurator.configureWithInteractor = { _ in }
         environment.coreSdk.getCurrentEngagement = { nil }
@@ -150,8 +155,13 @@ extension GliaTests {
         theme.call.connect.queue.firstText = "Glia 1"
         theme.chat.connect.queue.firstText = "Glia 2"
 
-        try sdk.configure(with: .mock()) { }
-        try sdk.startEngagement(engagementKind: .chat, in: ["queueId"], theme: theme)
+        try sdk.configure(with: .mock()) {
+            do {
+                try sdk.startEngagement(engagementKind: .chat, in: ["queueId"], theme: theme)
+            } catch {
+                XCTFail("startEngagement unexpectedly failed with error \(error), but should succeed instead.")
+            }
+        }
 
         let configuredSdkTheme = resultingViewFactory?.theme
         XCTAssertEqual(configuredSdkTheme?.call.connect.queue.firstText, "Glia")
@@ -176,15 +186,20 @@ extension GliaTests {
             )
         }
         environment.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         environment.coreSDKConfigurator.configureWithInteractor = { _ in }
         environment.coreSdk.localeProvider.getRemoteString = { _ in nil }
 
         let sdk = Glia(environment: environment)
 
-        try sdk.configure(with: .mock(companyName: "Glia"))
-        try sdk.startEngagement(engagementKind: .chat, in: ["queueId"])
+        try sdk.configure(with: .mock(companyName: "Glia")) {
+            do {
+                try sdk.startEngagement(engagementKind: .chat, in: ["queueId"])
+            } catch {
+                XCTFail("startEngagement unexpectedly failed with error \(error), but should succeed instead.")
+            }
+        }
 
         let configuredSdkTheme = resultingViewFactory?.theme
         XCTAssertEqual(configuredSdkTheme?.call.connect.queue.firstText, "Glia")
@@ -209,15 +224,20 @@ extension GliaTests {
             )
         }
         environment.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         environment.coreSDKConfigurator.configureWithInteractor = { _ in }
         environment.coreSdk.localeProvider.getRemoteString = { _ in nil }
 
         let sdk = Glia(environment: environment)
 
-        try sdk.configure(with: .mock())
-        try sdk.startEngagement(engagementKind: .chat, in: ["queueId"])
+        try sdk.configure(with: .mock()) {
+            do {
+                try sdk.startEngagement(engagementKind: .chat, in: ["queueId"])
+            } catch {
+                XCTFail("startEngagement unexpectedly failed with error \(error), but should succeed instead.")
+            }
+        }
 
         let configuredSdkTheme = resultingViewFactory?.theme
         XCTAssertEqual(configuredSdkTheme?.call.connect.queue.firstText, "Company Name")
@@ -244,7 +264,7 @@ extension GliaTests {
 
         environment.coreSdk.localeProvider.getRemoteString = { _ in "" }
         environment.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         environment.coreSDKConfigurator.configureWithInteractor = { _ in }
         environment.coreSdk.getCurrentEngagement = { nil }
@@ -255,8 +275,13 @@ extension GliaTests {
         theme.call.connect.queue.firstText = "Glia 1"
         theme.chat.connect.queue.firstText = "Glia 2"
 
-        try sdk.configure(with: .mock())
-        try sdk.startEngagement(engagementKind: .chat, in: ["queueId"], theme: theme)
+        try sdk.configure(with: .mock()) {
+            do {
+                try sdk.startEngagement(engagementKind: .chat, in: ["queueId"], theme: theme)
+            } catch {
+                XCTFail("startEngagement unexpectedly failed with error \(error), but should succeed instead.")
+            }
+        }
 
         let configuredSdkTheme = resultingViewFactory?.theme
         XCTAssertEqual(configuredSdkTheme?.call.connect.queue.firstText, "Glia 1")
@@ -288,14 +313,14 @@ extension GliaTests {
             Glia.sharedInstance.stringProviding = StringProviding(
                 getRemoteString: environment.coreSdk.localeProvider.getRemoteString
             )
-            completion?()
+            completion(.success(()))
         }
         environment.coreSdk.getCurrentEngagement = { nil }
 
         let sdk = Glia(environment: environment)
         try sdk.configure(with: .mock(), completion: {})
         try sdk.startEngagement(engagementKind: .chat, in: ["queueId"])
-        
+
         let configuredSdkTheme = resultingViewFactory?.theme
         let localFallbackCompanyName = "Company Name"
         XCTAssertEqual(configuredSdkTheme?.call.connect.queue.firstText, localFallbackCompanyName)
diff --git a/GliaWidgetsTests/Sources/Glia/GliaTests.swift b/GliaWidgetsTests/Sources/Glia/GliaTests.swift
index e4e3e83ef..25b7a9ebe 100644
--- a/GliaWidgetsTests/Sources/Glia/GliaTests.swift
+++ b/GliaWidgetsTests/Sources/Glia/GliaTests.swift
@@ -52,12 +52,11 @@ final class GliaTests: XCTestCase {
         gliaEnv.createFileUploadListModel = { _ in .mock() }
         gliaEnv.coreSdk.localeProvider.getRemoteString = { _ in nil }
         gliaEnv.coreSdk.authentication = { _ in .mock }
-        gliaEnv.coreSdk.configureWithConfiguration = { _, callback in callback?() }
         gliaEnv.coreSdk.queueForEngagement = { _, callback in
             callback(.success(.mock))
         }
         gliaEnv.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         gliaEnv.coreSDKConfigurator.configureWithInteractor = { _ in }
 
@@ -130,7 +129,7 @@ final class GliaTests: XCTestCase {
         var gliaEnv = Glia.Environment.failing
         gliaEnv.gcd.mainQueue.asyncIfNeeded = { callback in callback() }
         gliaEnv.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         gliaEnv.coreSDKConfigurator.configureWithInteractor = { _ in }
 
@@ -138,7 +137,7 @@ final class GliaTests: XCTestCase {
         sdk.onEvent = {
             calls.append(.onEvent($0))
         }
-        try sdk.configure(with: .mock())
+        try sdk.configure(with: .mock()) {}
         sdk.callVisualizer.delegate?(.visitorCodeIsRequested)
         sdk.environment.coreSdk.getCurrentEngagement = { .mock(source: .callVisualizer) }
 
@@ -158,7 +157,7 @@ final class GliaTests: XCTestCase {
         gliaEnv.coreSdk.configureWithConfiguration = { _, _ in }
         gliaEnv.gcd.mainQueue.asyncIfNeeded = { callback in callback() }
         gliaEnv.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         gliaEnv.coreSDKConfigurator.configureWithInteractor = { _ in }
 
@@ -166,7 +165,7 @@ final class GliaTests: XCTestCase {
         sdk.onEvent = {
             calls.append(.onEvent($0))
         }
-        try sdk.configure(with: .mock())
+        try sdk.configure(with: .mock()) {}
         sdk.callVisualizer.delegate?(.visitorCodeIsRequested)
 
         sdk.environment.coreSdk.getCurrentEngagement = { .mock(source: .callVisualizer) }
@@ -185,7 +184,7 @@ final class GliaTests: XCTestCase {
         gliaEnv.callVisualizerPresenter = .init(presenter: { nil })
         gliaEnv.gcd.mainQueue.asyncIfNeeded = { callback in callback() }
         gliaEnv.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         gliaEnv.coreSDKConfigurator.configureWithInteractor = { _ in }
 
@@ -193,7 +192,7 @@ final class GliaTests: XCTestCase {
         sdk.onEvent = {
             calls.append(.onEvent($0))
         }
-        try sdk.configure(with: .mock())
+        try sdk.configure(with: .mock()) {}
         sdk.callVisualizer.delegate?(.visitorCodeIsRequested)
         sdk.environment.coreSdk.getCurrentEngagement = { .mock(source: .callVisualizer) }
 
@@ -220,7 +219,7 @@ final class GliaTests: XCTestCase {
         gliaEnv.gcd.mainQueue.asyncIfNeeded = { callback in callback() }
         gliaEnv.notificationCenter.addObserverClosure = { _, _, _, _ in }
         gliaEnv.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
         }
         gliaEnv.coreSDKConfigurator.configureWithInteractor = { _ in }
 
@@ -228,7 +227,7 @@ final class GliaTests: XCTestCase {
         sdk.onEvent = {
             calls.append(.onEvent($0))
         }
-        try sdk.configure(with: .mock())
+        try sdk.configure(with: .mock()) {}
         sdk.callVisualizer.delegate?(.visitorCodeIsRequested)
         sdk.environment.coreSdk.getCurrentEngagement = { .mock(source: .callVisualizer) }
 
@@ -243,7 +242,7 @@ final class GliaTests: XCTestCase {
         environment.coreSdk.getCurrentEngagement = { .mock() }
         let sdk = Glia(environment: environment)
 
-        XCTAssertThrowsError(try sdk.configure(with: .mock(), queueId: "queueId")) { error in
+        XCTAssertThrowsError(try sdk.configure(with: .mock()) {}) { error in
             XCTAssertEqual(error as? GliaError, GliaError.configuringDuringEngagementIsNotAllowed)
         }
     }
@@ -304,27 +303,46 @@ final class GliaTests: XCTestCase {
     func test_isConfiguredIsTrueWhenConfigurationPerformed() throws {
         var environment = Glia.Environment.failing
         environment.coreSDKConfigurator.configureWithConfiguration = { _, completion in
-            completion?()
+            completion(.success(()))
+        }
+        let sdk = Glia(environment: environment)
+        try sdk.configure(with: .mock()) {}
+        XCTAssertTrue(sdk.isConfigured)
+    }
+
+    func test_isConfiguredIsFalseWhenSecondConfigureCallThrowsError() throws {
+        var environment = Glia.Environment.failing
+        var isFirstConfigure = true
+        environment.coreSDKConfigurator.configureWithConfiguration = { _, completion in
+            if isFirstConfigure {
+                isFirstConfigure = false
+                completion(.success(()))
+            } else {
+                throw CoreSdkClient.GliaCoreError.mock()
+            }
         }
         let sdk = Glia(environment: environment)
-        try sdk.configure(with: .mock())
+        try sdk.configure(with: .mock()) {}
         XCTAssertTrue(sdk.isConfigured)
+
+        try? sdk.configure(with: .mock()) {}
+        XCTAssertFalse(sdk.isConfigured)
     }
 
-    func test_isConfiguredIsFalseWhenConfigureWithConfigurationThrowsError() throws {
+    func test_isConfiguredIsFalseWhenConfigureWithConfigurationThrowsError() {
         var environment = Glia.Environment.failing
         environment.coreSDKConfigurator.configureWithConfiguration = { _, _ in
             throw CoreSdkClient.GliaCoreError.mock()
         }
         let sdk = Glia(environment: environment)
-        try sdk.configure(with: .mock())
+        try? sdk.configure(with: .mock()) {}
         XCTAssertFalse(sdk.isConfigured)
     }
 
     func test_engagementCoordinatorGetsDeallocated() throws {
         var environment = Glia.Environment.failing
         environment.coreSDKConfigurator.configureWithConfiguration = { _, callback in
-            callback?()
+            callback(.success(()))
         }
         environment.coreSDKConfigurator.configureWithInteractor = { _ in }
         environment.coreSdk.localeProvider.getRemoteString = { _ in nil }
@@ -363,7 +381,7 @@ final class GliaTests: XCTestCase {
         gliaEnv.screenShareHandler = screenShareHandler
         gliaEnv.gcd.mainQueue.asyncIfNeeded = { callback in callback() }
         gliaEnv.coreSDKConfigurator.configureWithConfiguration = { _, callback in
-            callback?()
+            callback(.success(()))
         }
         gliaEnv.coreSDKConfigurator.configureWithInteractor = { _ in }
         let sdk = Glia(environment: gliaEnv)
diff --git a/GliaWidgetsTests/Sources/InteractorTests.swift b/GliaWidgetsTests/Sources/InteractorTests.swift
index c91c880e2..44da62bab 100644
--- a/GliaWidgetsTests/Sources/InteractorTests.swift
+++ b/GliaWidgetsTests/Sources/InteractorTests.swift
@@ -99,7 +99,7 @@ class InteractorTests: XCTestCase {
         var callbacks: [Callback] = []
         var interactorEnv = Interactor.Environment.failing
         interactorEnv.coreSdk.configureWithInteractor = { _ in }
-        interactorEnv.coreSdk.configureWithConfiguration = { $1?() }
+        interactorEnv.coreSdk.configureWithConfiguration = { $1(.success(())) }
         interactorEnv.coreSdk.queueForEngagement = { _, _ in }
         interactorEnv.gcd = .mock
         let interactor = Interactor.mock(environment: interactorEnv)
@@ -131,7 +131,7 @@ class InteractorTests: XCTestCase {
         var callbacks: [Callback] = []
         var interactorEnv = Interactor.Environment.failing
         interactorEnv.coreSdk.configureWithInteractor = { _ in }
-        interactorEnv.coreSdk.configureWithConfiguration = { $1?() }
+        interactorEnv.coreSdk.configureWithConfiguration = { $1(.success(())) }
         interactorEnv.coreSdk.queueForEngagement = { _, completion in
             completion(.success(.mock))
         }
@@ -166,7 +166,7 @@ class InteractorTests: XCTestCase {
         var callbacks: [Callback] = []
         var interactorEnv = Interactor.Environment.failing
         interactorEnv.coreSdk.configureWithInteractor = { _ in }
-        interactorEnv.coreSdk.configureWithConfiguration = { $1?() }
+        interactorEnv.coreSdk.configureWithConfiguration = { $1(.success(())) }
         interactorEnv.coreSdk.queueForEngagement = { _, completion in
             completion(.failure(.mock()))
         }
@@ -380,7 +380,7 @@ class InteractorTests: XCTestCase {
             callbacks.append(.sendMessageWithAttachment)
         }
         interactorEnv.coreSdk.configureWithInteractor = { _ in }
-        interactorEnv.coreSdk.configureWithConfiguration = { $1?() }
+        interactorEnv.coreSdk.configureWithConfiguration = { $1(.success(())) }
         let interactor = Interactor.mock(environment: interactorEnv)
         
         interactor.send(messagePayload: .mock(content: "mock-message")) { result in
diff --git a/TestingApp/ViewController/ViewController.swift b/TestingApp/ViewController/ViewController.swift
index 2d28283ca..e90b66357 100644
--- a/TestingApp/ViewController/ViewController.swift
+++ b/TestingApp/ViewController/ViewController.swift
@@ -90,19 +90,22 @@ class ViewController: UIViewController {
     }
 
     private func showErrorAlert(using error: Error) {
-        guard let gliaError = error as? GliaError else { return }
-
-        switch gliaError {
-        case GliaError.engagementExists:
-            alert(message: "Failed to start\nEngagement is ongoing, please use 'Resume' button")
-        case GliaError.engagementNotExist:
-            alert(message: "Failed to start\nNo ongoing engagement. Please start a new one with 'Start chat' button")
-        case GliaError.callVisualizerEngagementExists:
-            alert(message: "Failed to start\nCall Visualizer engagement is ongoing")
-        case GliaError.configuringDuringEngagementIsNotAllowed:
-            alert(message: "The operation couldn't be completed. '\(gliaError)'.")
-        default:
-            alert(message: "Failed to start\nCheck Glia parameters in Settings")
+        if let gliaError = error as? GliaError {
+
+            switch gliaError {
+            case GliaError.engagementExists:
+                alert(message: "Failed to start\nEngagement is ongoing, please use 'Resume' button")
+            case GliaError.engagementNotExist:
+                alert(message: "Failed to start\nNo ongoing engagement. Please start a new one with 'Start chat' button")
+            case GliaError.callVisualizerEngagementExists:
+                alert(message: "Failed to start\nCall Visualizer engagement is ongoing")
+            case GliaError.configuringDuringEngagementIsNotAllowed:
+                alert(message: "The operation couldn't be completed. '\(gliaError)'.")
+            default:
+                alert(message: "Failed to start\nCheck Glia parameters in Settings")
+            }
+        } else {
+            alert(message: "Failed to execute with error: \(error)\nCheck Glia parameters in Settings")
         }
     }
 
@@ -127,15 +130,18 @@ class ViewController: UIViewController {
     }
 
     @IBAction private func endEngagementTapped() {
-        self.catchingError {
-            // Since ending of engagement is possible
-            // only if such engagement exists, we need
-            // to configure SDK, and only then attempt
-            // to end engagement.
-            try Glia.sharedInstance.configure(with: configuration) {
+        // Since ending of engagement is possible
+        // only if such engagement exists, we need
+        // to configure SDK, and only then attempt
+        // to end engagement.
+        configureSDK(uiConfig: nil) { [weak self] result in
+            switch result {
+            case .success:
                 Glia.sharedInstance.endEngagement { result in
                     print("End engagement operation has been executed. Result='\(result)'.")
                 }
+            case let .failure(error):
+                self?.showErrorAlert(using: error)
             }
         }
     }
@@ -237,9 +243,15 @@ extension ViewController {
         do {
             try Glia.sharedInstance.configure(
                 with: configuration
-            ) {
-                completionBlock("SDK has been configured")
-                completion?(.success(()))
+            ) { result in
+                switch result {
+                case .success:
+                    completionBlock("SDK has been configured")
+                    completion?(.success(()))
+                case let .failure(error):
+                    completionBlock(error)
+                    completion?(.failure(error))
+                }
             }
         } catch {
             completionBlock(error)
@@ -288,18 +300,30 @@ extension ViewController {
     }
 
     private func startEngagement(with kind: EngagementKind, config name: String) {
-        try? Glia.sharedInstance.configure(
-            with: configuration,
-            queueId: queueId
-        )
-
         guard let config = retrieveRemoteConfiguration(name) else { return }
 
-        try? Glia.sharedInstance.startEngagementWithConfig(
-            engagement: kind,
-            in: [queueId],
-            uiConfig: config
-        )
+        let startEngagement = {
+            self.catchingError {
+                try Glia.sharedInstance.startEngagementWithConfig(
+                    engagement: kind,
+                    in: [self.queueId],
+                    uiConfig: config
+                )
+            }
+        }
+
+        if autoConfigureSdkToggle.isOn {
+            configureSDK(uiConfig: nil) { [weak self] result in
+                switch result {
+                case .success:
+                    startEngagement()
+                case let .failure(error):
+                    self?.showErrorAlert(using: error)
+                }
+            }
+        } else {
+            startEngagement()
+        }
     }
 
     private func jsonNames() -> [String] {
@@ -379,10 +403,7 @@ extension ViewController {
 
     @IBAction private func toggleAuthentication() {
         catchingError {
-            try Glia.sharedInstance.configure(
-                with: configuration,
-                queueId: queueId
-            ) { [weak self] in
+            try Glia.sharedInstance.configure(with: configuration) { [weak self] in
                 guard let self = self else { return }
                 self.catchingError {
                     let authentication = try Self.authentication()