diff --git a/Package.swift b/Package.swift
index 2021e13f..31c0f0ca 100644
--- a/Package.swift
+++ b/Package.swift
@@ -22,6 +22,9 @@ let package = Package(
       dependencies: ["FormbricksSDK"],
       resources: [
         .process("Mock/User.json"),
+        .process("Mock/UserWithErrors.json"),
+        .process("Mock/UserWithMessages.json"),
+        .process("Mock/UserWithErrorsAndMessages.json"),
         .process("Mock/Environment.json"),
       ]
     )
diff --git a/Sources/FormbricksSDK/Formbricks.swift b/Sources/FormbricksSDK/Formbricks.swift
index ac236a1b..d1a5315c 100644
--- a/Sources/FormbricksSDK/Formbricks.swift
+++ b/Sources/FormbricksSDK/Formbricks.swift
@@ -79,7 +79,7 @@ import Network
         if let attributes = config.attributes, !attributes.isEmpty {
             userManager?.set(attributes: attributes)
         }
-        if let language = config.attributes?["language"] {
+        if let language = config.attributes?["language"]?.stringValue {
             userManager?.set(language: language)
             self.language = language
         }
@@ -96,6 +96,11 @@ import Network
     
     /**
      Sets the user id for the current user with the given `String`.
+     
+     - If the same userId is already set, this is a no-op.
+     - If a different userId is already set, the previous user state is cleaned up first
+       before setting the new userId.
+     
      The SDK must be initialized before calling this method.
           
      Example:
@@ -110,21 +115,28 @@ import Network
             return
         }
         
-        if let existing = userManager?.userId, !existing.isEmpty {
-            logger?.error("A userId is already set (\"\(existing)\") – please call Formbricks.logout() before setting a new one.")
+        // If the same userId is already set, no-op
+        if let existing = userManager?.userId, existing == userId {
+            logger?.debug("UserId is already set to the same value, skipping")
             return
         }
         
+        // If a different userId is set, clean up the previous user state first
+        if let existing = userManager?.userId, !existing.isEmpty {
+            logger?.debug("Different userId is being set, cleaning up previous user state")
+            userManager?.logout()
+        }
+        
         userManager?.set(userId: userId)
     }
     
     /**
-     Adds an attribute for the current user with the given `String` value and `String` key.
+     Adds a string attribute for the current user.
      The SDK must be initialized before calling this method.
           
      Example:
      ```swift
-     Formbricks.setAttribute("ATTRIBUTE", forKey: "KEY")
+     Formbricks.setAttribute("John", forKey: "name")
      ```
      */
     @objc public static func setAttribute(_ attribute: String, forKey key: String) {
@@ -134,19 +146,71 @@ import Network
             return
         }
         
-        userManager?.add(attribute: attribute, forKey: key)
+        userManager?.add(attribute: .string(attribute), forKey: key)
+    }
+
+    /**
+     Adds a numeric attribute for the current user.
+     The SDK must be initialized before calling this method.
+          
+     Example:
+     ```swift
+     Formbricks.setAttribute(42.0, forKey: "age")
+     ```
+     */
+    public static func setAttribute(_ attribute: Double, forKey key: String) {
+        guard Formbricks.isInitialized else {
+            let error = FormbricksSDKError(type: .sdkIsNotInitialized)
+            Formbricks.logger?.error(error.message)
+            return
+        }
+        
+        userManager?.add(attribute: .number(attribute), forKey: key)
+    }
+
+    /**
+     Adds a date attribute for the current user.
+     The date is converted to an ISO 8601 string. The backend will detect the format and treat it as a date type.
+     The SDK must be initialized before calling this method.
+          
+     Example:
+     ```swift
+     Formbricks.setAttribute(Date(), forKey: "signupDate")
+     ```
+     */
+    public static func setAttribute(_ attribute: Date, forKey key: String) {
+        guard Formbricks.isInitialized else {
+            let error = FormbricksSDKError(type: .sdkIsNotInitialized)
+            Formbricks.logger?.error(error.message)
+            return
+        }
+        
+        userManager?.add(attribute: .string(ISO8601DateFormatter().string(from: attribute)), forKey: key)
     }
     
     /**
-     Sets the user attributes for the current user with the given `Dictionary` of `String` values and `String` keys.
+     Sets the user attributes for the current user.
+     
+     Attribute types are determined by the value:
+     - String values -> string attribute
+     - Number values -> number attribute
+     - Use ISO 8601 date strings for date attributes
+     
+     On first write to a new attribute, the type is set based on the value type.
+     On subsequent writes, the value must match the existing attribute type.
+     
      The SDK must be initialized before calling this method.
           
      Example:
      ```swift
-     Formbricks.setAttributes(["KEY", "ATTRIBUTE"])
+     Formbricks.setAttributes([
+         "name": "John",
+         "age": 30,
+         "score": 9.5
+     ])
      ```
      */
-    @objc public static func setAttributes(_ attributes: [String : String]) {
+    public static func setAttributes(_ attributes: [String : AttributeValue]) {
         guard Formbricks.isInitialized else {
             let error = FormbricksSDKError(type: .sdkIsNotInitialized)
             Formbricks.logger?.error(error.message)
diff --git a/Sources/FormbricksSDK/Helpers/ConfigBuilder.swift b/Sources/FormbricksSDK/Helpers/ConfigBuilder.swift
index 5159e9c8..28df5356 100644
--- a/Sources/FormbricksSDK/Helpers/ConfigBuilder.swift
+++ b/Sources/FormbricksSDK/Helpers/ConfigBuilder.swift
@@ -5,12 +5,12 @@ import Foundation
     let appUrl: String
     let environmentId: String
     let userId: String?
-    let attributes: [String:String]?
+    let attributes: [String: AttributeValue]?
     let logLevel: LogLevel
     /// Optional custom service, injected via Builder
     let customService: FormbricksServiceProtocol?
     
-    init(appUrl: String, environmentId: String, userId: String?, attributes: [String : String]?, logLevel: LogLevel, customService: FormbricksServiceProtocol?) {
+    init(appUrl: String, environmentId: String, userId: String?, attributes: [String: AttributeValue]?, logLevel: LogLevel, customService: FormbricksServiceProtocol?) {
             self.appUrl = appUrl
             self.environmentId = environmentId
             self.userId = userId
@@ -24,7 +24,7 @@ import Foundation
         var appUrl: String
         var environmentId: String
         var userId: String?
-        var attributes: [String:String] = [:]
+        var attributes: [String: AttributeValue] = [:]
         var logLevel: LogLevel = .error
         /// Optional custom service, injected via Builder
         var customService: FormbricksServiceProtocol?
@@ -41,14 +41,27 @@ import Foundation
         }
         
         /// Sets the attributes for the Builder object.
-        @objc public func set(attributes: [String:String]) -> Builder {
+        ///
+        /// Thanks to `ExpressibleByStringLiteral`, `ExpressibleByIntegerLiteral`,
+        /// and `ExpressibleByFloatLiteral` conformances on `AttributeValue`,
+        /// you can use literal syntax:
+        /// ```swift
+        /// .set(attributes: ["name": "John", "age": 30])
+        /// ```
+        public func set(attributes: [String: AttributeValue]) -> Builder {
             self.attributes = attributes
             return self
         }
+
+        /// Sets the attributes for the Builder object using string values (Obj-C compatible).
+        @objc public func set(stringAttributes: [String: String]) -> Builder {
+            self.attributes = stringAttributes.mapValues { .string($0) }
+            return self
+        }
         
-        /// Adds an attribute to the Builder object.
+        /// Adds a string attribute to the Builder object (Obj-C compatible).
         @objc public func add(attribute: String, forKey key: String) -> Builder {
-            self.attributes[key] = attribute
+            self.attributes[key] = .string(attribute)
             return self
         }
         
diff --git a/Sources/FormbricksSDK/Manager/SurveyManager.swift b/Sources/FormbricksSDK/Manager/SurveyManager.swift
index b60a5daa..b01be37a 100644
--- a/Sources/FormbricksSDK/Manager/SurveyManager.swift
+++ b/Sources/FormbricksSDK/Manager/SurveyManager.swift
@@ -83,7 +83,7 @@ final class SurveyManager {
         let actionClasses = environmentResponse?.data.data.actionClasses ?? []
         let codeActionClasses = actionClasses.filter { $0.type == "code" }
         guard let actionClass = codeActionClasses.first(where: { $0.key == action }) else {
-            Formbricks.logger?.error("\(action) action unknown. Please add this action in Formbricks first in order to use it in your code.")
+            Formbricks.logger?.error("Action with identifier '\(action)' is unknown. Please add this action in Formbricks in order to use it via the SDK action tracking.")
             return
         }
         
diff --git a/Sources/FormbricksSDK/Manager/UserManager.swift b/Sources/FormbricksSDK/Manager/UserManager.swift
index e523a7b3..43e49ef9 100644
--- a/Sources/FormbricksSDK/Manager/UserManager.swift
+++ b/Sources/FormbricksSDK/Manager/UserManager.swift
@@ -40,12 +40,12 @@ final class UserManager: UserManagerSyncable {
     }
     
     /// Starts an update queue with the given attribute.
-    func add(attribute: String, forKey key: String) {
+    func add(attribute: AttributeValue, forKey key: String) {
         updateQueue?.add(attribute: attribute, forKey: key)
     }
     
     /// Starts an update queue with the given attributes.
-    func set(attributes: [String: String]) {
+    func set(attributes: [String: AttributeValue]) {
         updateQueue?.set(attributes: attributes)
     }
     
@@ -85,7 +85,7 @@ final class UserManager: UserManagerSyncable {
     }
 
     /// Syncs the user state with the server, calls the `self?.surveyManager?.filterSurveys()` method and starts the sync timer.
-    func syncUser(withId id: String, attributes: [String: String]? = nil) {
+    func syncUser(withId id: String, attributes: [String: AttributeValue]? = nil) {
         service.postUser(id: id, attributes: attributes) { [weak self] result in
             switch result {
             case .success(let userResponse):
@@ -100,6 +100,20 @@ final class UserManager: UserManagerSyncable {
                 let serverLanguage = userResponse.data.state?.data?.language
                 Formbricks.language = serverLanguage ?? "default"
                 
+                // Log errors (always visible) - e.g., invalid attribute keys, type mismatches
+                if let errors = userResponse.data.errors {
+                    for error in errors {
+                        Formbricks.logger?.error(error)
+                    }
+                }
+                
+                // Log informational messages (debug only)
+                if let messages = userResponse.data.messages {
+                    for message in messages {
+                        Formbricks.logger?.debug("User update message: \(message)")
+                    }
+                }
+                
                 self?.updateQueue?.reset()
                 self?.surveyManager?.filterSurveys()
                 self?.startSyncTimer()
@@ -111,13 +125,7 @@ final class UserManager: UserManagerSyncable {
     
     /// Logs out the user and clears the user state.
     func logout() {
-        var isUserIdDefined = false
-        
-        if userId != nil {
-            isUserIdDefined = true
-        } else {
-            Formbricks.logger?.error("no userId is set, please set a userId first using the setUserId function")
-        }
+        Formbricks.logger?.debug("Logging out and cleaning user state")
         
         UserDefaults.standard.removeObject(forKey: UserManager.userIdKey)
         UserDefaults.standard.removeObject(forKey: UserManager.contactIdKey)
@@ -141,11 +149,6 @@ final class UserManager: UserManagerSyncable {
         
         // Re-filter surveys for logged out user
         surveyManager?.filterSurveys()
-        
-        if isUserIdDefined {
-            Formbricks.logger?.debug("Successfully logged out user and reset the user state.")
-        }
-        
     }
     
     func cleanupUpdateQueue() {
diff --git a/Sources/FormbricksSDK/Model/User/AttributeValue.swift b/Sources/FormbricksSDK/Model/User/AttributeValue.swift
new file mode 100644
index 00000000..ae33e0ae
--- /dev/null
+++ b/Sources/FormbricksSDK/Model/User/AttributeValue.swift
@@ -0,0 +1,88 @@
+import Foundation
+
+/// Represents a user attribute value that can be a string, number, or date.
+///
+/// Attribute types are determined by the Swift value type:
+/// - String values -> string attribute
+/// - Number values -> number attribute
+/// - Date values -> date attribute (converted to ISO string)
+///
+/// On first write to a new attribute, the type is set based on the value type.
+/// On subsequent writes, the value must match the existing attribute type.
+///
+/// Supports literal syntax in dictionaries:
+/// ```swift
+/// let attributes: [String: AttributeValue] = [
+///     "name": "John",
+///     "age": 30,
+///     "score": 9.5
+/// ]
+/// ```
+public enum AttributeValue: Codable, Equatable {
+    case string(String)
+    case number(Double)
+
+    public init(from decoder: Decoder) throws {
+        let container = try decoder.singleValueContainer()
+
+        if let doubleValue = try? container.decode(Double.self) {
+            self = .number(doubleValue)
+        } else if let stringValue = try? container.decode(String.self) {
+            self = .string(stringValue)
+        } else {
+            throw DecodingError.typeMismatch(
+                AttributeValue.self,
+                DecodingError.Context(
+                    codingPath: decoder.codingPath,
+                    debugDescription: "Expected String or Number for AttributeValue"
+                )
+            )
+        }
+    }
+
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.singleValueContainer()
+        switch self {
+        case .string(let value):
+            try container.encode(value)
+        case .number(let value):
+            try container.encode(value)
+        }
+    }
+
+    /// The string representation of this attribute value, if it is a string.
+    public var stringValue: String? {
+        if case .string(let value) = self {
+            return value
+        }
+        return nil
+    }
+
+    /// The numeric representation of this attribute value, if it is a number.
+    public var numberValue: Double? {
+        if case .number(let value) = self {
+            return value
+        }
+        return nil
+    }
+}
+
+// MARK: - Literal conformances for ergonomic dictionary syntax
+
+extension AttributeValue: ExpressibleByStringLiteral {
+    public init(stringLiteral value: String) {
+        self = .string(value)
+    }
+}
+
+extension AttributeValue: ExpressibleByIntegerLiteral {
+    public init(integerLiteral value: Int) {
+        self = .number(Double(value))
+    }
+}
+
+extension AttributeValue: ExpressibleByFloatLiteral {
+    public init(floatLiteral value: Double) {
+        self = .number(value)
+    }
+}
diff --git a/Sources/FormbricksSDK/Model/User/UserResponseData.swift b/Sources/FormbricksSDK/Model/User/UserResponseData.swift
index 98a8bffe..30c9b12c 100644
--- a/Sources/FormbricksSDK/Model/User/UserResponseData.swift
+++ b/Sources/FormbricksSDK/Model/User/UserResponseData.swift
@@ -1,3 +1,5 @@
 struct UserResponseData: Codable {
     let state: UserState?
+    let messages: [String]?
+    let errors: [String]?
 }
diff --git a/Sources/FormbricksSDK/Networking/ClientAPI/Endpoints/User/PostUserRequest.swift b/Sources/FormbricksSDK/Networking/ClientAPI/Endpoints/User/PostUserRequest.swift
index 398f525d..41078ed8 100644
--- a/Sources/FormbricksSDK/Networking/ClientAPI/Endpoints/User/PostUserRequest.swift
+++ b/Sources/FormbricksSDK/Networking/ClientAPI/Endpoints/User/PostUserRequest.swift
@@ -9,11 +9,11 @@ final class PostUserRequest: EncodableRequest<PostUserRequest.Body>, CodableRequ
     
     struct Body: Codable {
         let userId: String
-        let attributes: [String: String]?
+        let attributes: [String: AttributeValue]?
     }
     
         
-    init(userId: String, attributes: [String: String]?) {
+    init(userId: String, attributes: [String: AttributeValue]?) {
         super.init(object: Body(userId: userId, attributes: attributes))
     }
 }
diff --git a/Sources/FormbricksSDK/Networking/Queue/UpdateQueue.swift b/Sources/FormbricksSDK/Networking/Queue/UpdateQueue.swift
index 79d0a597..f7b10e86 100644
--- a/Sources/FormbricksSDK/Networking/Queue/UpdateQueue.swift
+++ b/Sources/FormbricksSDK/Networking/Queue/UpdateQueue.swift
@@ -1,7 +1,7 @@
 import Foundation
 
 protocol UserManagerSyncable: AnyObject {
-    func syncUser(withId id: String, attributes: [String: String]?)
+    func syncUser(withId id: String, attributes: [String: AttributeValue]?)
 }
 
 /// Update queue. This class is used to queue updates to the user.
@@ -12,7 +12,7 @@ final class UpdateQueue {
     
     private let syncQueue = DispatchQueue(label: "com.formbricks.updateQueue")
     private var userId: String?
-    private var attributes: [String : String]?
+    private var attributes: [String : AttributeValue]?
     private var language: String?
     private var timer: Timer?
     
@@ -29,14 +29,14 @@ final class UpdateQueue {
         }
     }
     
-    func set(attributes: [String : String]) {
+    func set(attributes: [String : AttributeValue]) {
         syncQueue.sync {
             self.attributes = attributes
             startDebounceTimer()
         }
     }
     
-    func add(attribute: String, forKey key: String) {
+    func add(attribute: AttributeValue, forKey key: String) {
         syncQueue.sync {
            if var attr = self.attributes {
                attr[key] = attribute
@@ -57,7 +57,7 @@ final class UpdateQueue {
             
             if effectiveUserId != nil {
                 // If we have a userId, set attributes
-                self.attributes = ["language": language]
+                self.attributes = ["language": .string(language)]
             } else {
                 // If no userId, just update locally without API call
                 Formbricks.logger?.debug("UpdateQueue - updating language locally: \(language)")
@@ -97,7 +97,7 @@ private extension UpdateQueue {
     
     @objc func commit() {
         var effectiveUserId: String?
-        var effectiveAttributes: [String: String]?
+        var effectiveAttributes: [String: AttributeValue]?
         
         // Capture a consistent snapshot under the sync queue
         syncQueue.sync {
diff --git a/Sources/FormbricksSDK/Networking/Service/FormbricksService.swift b/Sources/FormbricksSDK/Networking/Service/FormbricksService.swift
index f7f6ccd0..3d45f4c4 100644
--- a/Sources/FormbricksSDK/Networking/Service/FormbricksService.swift
+++ b/Sources/FormbricksSDK/Networking/Service/FormbricksService.swift
@@ -10,7 +10,7 @@ class FormbricksService: FormbricksServiceProtocol {
 
     // MARK: - User -
     /// Logs in a user with the given ID or creates one if it doesn't exist.
-    func postUser(id: String, attributes: [String: String]?, completion: @escaping (ResultType<PostUserRequest.Response>) -> Void) {
+    func postUser(id: String, attributes: [String: AttributeValue]?, completion: @escaping (ResultType<PostUserRequest.Response>) -> Void) {
         let endPointRequest = PostUserRequest(userId: id, attributes: attributes)
         execute(endPointRequest, withCompletion: completion)
     }
@@ -22,7 +22,7 @@ protocol FormbricksServiceProtocol {
     )
     func postUser(
       id: String,
-      attributes: [String: String]?,
+      attributes: [String: AttributeValue]?,
       completion: @escaping (ResultType<PostUserRequest.Response>) -> Void
     )
   }
diff --git a/Tests/FormbricksSDKTests/FormbricksSDKTests.swift b/Tests/FormbricksSDKTests/FormbricksSDKTests.swift
index e38e3795..65a3e8b9 100644
--- a/Tests/FormbricksSDKTests/FormbricksSDKTests.swift
+++ b/Tests/FormbricksSDKTests/FormbricksSDKTests.swift
@@ -261,6 +261,219 @@ final class FormbricksSDKTests: XCTestCase {
         XCTAssertNil(manager.getLanguageCode(survey: survey, language: "spanish"))
     }
 
+    // MARK: - UserManager syncUser errors/messages tests
+
+    func testSyncUserLogsErrors() {
+        let errorsMockService = MockFormbricksService()
+        errorsMockService.userMockResponse = .userWithErrors
+
+        let config = FormbricksConfig.Builder(appUrl: appUrl, environmentId: environmentId)
+            .setLogLevel(.debug)
+            .service(errorsMockService)
+            .build()
+        Formbricks.setup(with: config)
+
+        // Refresh environment first
+        Formbricks.surveyManager?.refreshEnvironmentIfNeeded(force: true)
+        let envExpectation = expectation(description: "Env loaded")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { envExpectation.fulfill() }
+        wait(for: [envExpectation])
+
+        // Set userId to trigger syncUser which uses the mock with errors
+        Formbricks.setUserId(userId)
+
+        let syncExpectation = expectation(description: "User synced with errors")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) {
+            syncExpectation.fulfill()
+        }
+        wait(for: [syncExpectation], timeout: 3.0)
+
+        // Verify the user was still synced successfully despite errors
+        XCTAssertEqual(Formbricks.userManager?.userId, userId, "User ID should be set even when response has errors")
+        XCTAssertNotNil(Formbricks.userManager?.syncTimer, "Sync timer should still be set")
+    }
+
+    func testSyncUserLogsMessages() {
+        let messagesMockService = MockFormbricksService()
+        messagesMockService.userMockResponse = .userWithMessages
+
+        let config = FormbricksConfig.Builder(appUrl: appUrl, environmentId: environmentId)
+            .setLogLevel(.debug)
+            .service(messagesMockService)
+            .build()
+        Formbricks.setup(with: config)
+
+        // Refresh environment first
+        Formbricks.surveyManager?.refreshEnvironmentIfNeeded(force: true)
+        let envExpectation = expectation(description: "Env loaded")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { envExpectation.fulfill() }
+        wait(for: [envExpectation])
+
+        // Set userId to trigger syncUser which uses the mock with messages
+        Formbricks.setUserId(userId)
+
+        let syncExpectation = expectation(description: "User synced with messages")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) {
+            syncExpectation.fulfill()
+        }
+        wait(for: [syncExpectation], timeout: 3.0)
+
+        // Verify the user was synced successfully
+        XCTAssertEqual(Formbricks.userManager?.userId, userId, "User ID should be set when response has messages")
+        XCTAssertNotNil(Formbricks.userManager?.syncTimer, "Sync timer should still be set")
+    }
+
+    func testSyncUserLogsErrorsAndMessages() {
+        let bothMockService = MockFormbricksService()
+        bothMockService.userMockResponse = .userWithErrorsAndMessages
+
+        let config = FormbricksConfig.Builder(appUrl: appUrl, environmentId: environmentId)
+            .setLogLevel(.debug)
+            .service(bothMockService)
+            .build()
+        Formbricks.setup(with: config)
+
+        // Refresh environment first
+        Formbricks.surveyManager?.refreshEnvironmentIfNeeded(force: true)
+        let envExpectation = expectation(description: "Env loaded")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { envExpectation.fulfill() }
+        wait(for: [envExpectation])
+
+        // Set userId to trigger syncUser which uses the mock with both errors and messages
+        Formbricks.setUserId(userId)
+
+        let syncExpectation = expectation(description: "User synced with errors and messages")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) {
+            syncExpectation.fulfill()
+        }
+        wait(for: [syncExpectation], timeout: 3.0)
+
+        // Verify the user was synced successfully despite having both errors and messages
+        XCTAssertEqual(Formbricks.userManager?.userId, userId, "User ID should be set when response has both errors and messages")
+        XCTAssertNotNil(Formbricks.userManager?.syncTimer, "Sync timer should still be set")
+    }
+
+    // MARK: - setUserId override behavior tests
+
+    func testSetUserIdSameValueIsNoOp() {
+        let config = FormbricksConfig.Builder(appUrl: appUrl, environmentId: environmentId)
+            .setLogLevel(.debug)
+            .service(mockService)
+            .build()
+        Formbricks.setup(with: config)
+
+        // Refresh environment first
+        Formbricks.surveyManager?.refreshEnvironmentIfNeeded(force: true)
+        let envExpectation = expectation(description: "Env loaded")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { envExpectation.fulfill() }
+        wait(for: [envExpectation])
+
+        // Set userId
+        Formbricks.setUserId(userId)
+        let setExpectation = expectation(description: "User set")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) { setExpectation.fulfill() }
+        wait(for: [setExpectation], timeout: 3.0)
+
+        XCTAssertEqual(Formbricks.userManager?.userId, userId)
+
+        // Set the same userId again — should be a no-op, userId stays the same
+        Formbricks.setUserId(userId)
+        XCTAssertEqual(Formbricks.userManager?.userId, userId, "Same userId should remain set (no-op)")
+    }
+
+    func testSetUserIdDifferentValueOverridesPrevious() {
+        let config = FormbricksConfig.Builder(appUrl: appUrl, environmentId: environmentId)
+            .setLogLevel(.debug)
+            .service(mockService)
+            .build()
+        Formbricks.setup(with: config)
+
+        // Refresh environment first
+        Formbricks.surveyManager?.refreshEnvironmentIfNeeded(force: true)
+        let envExpectation = expectation(description: "Env loaded")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { envExpectation.fulfill() }
+        wait(for: [envExpectation])
+
+        // Set initial userId and wait for sync to complete
+        Formbricks.setUserId(userId)
+        let setExpectation = expectation(description: "First user set")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) { setExpectation.fulfill() }
+        wait(for: [setExpectation], timeout: 3.0)
+
+        XCTAssertEqual(Formbricks.userManager?.userId, userId)
+
+        // Capture previous state to verify cleanup happens
+        Formbricks.surveyManager?.onNewDisplay(surveyId: surveyID)
+        XCTAssertEqual(Formbricks.userManager?.displays?.count, 1, "Should have 1 display before override")
+
+        // Set a different userId — should clean up previous user state first
+        let newUserId = "NEW-USER-ID-12345"
+        Formbricks.setUserId(newUserId)
+
+        // Immediately after setUserId, the previous user state should be cleaned up
+        // (logout was called synchronously before queueing the new userId)
+        XCTAssertNil(Formbricks.userManager?.userId, "Previous userId should be cleared by logout")
+        XCTAssertNil(Formbricks.userManager?.displays, "Previous displays should be cleared by logout")
+        XCTAssertNil(Formbricks.userManager?.responses, "Previous responses should be cleared by logout")
+        XCTAssertNil(Formbricks.userManager?.segments, "Previous segments should be cleared by logout")
+    }
+
+    func testLogoutWithoutUserIdDoesNotError() {
+        let config = FormbricksConfig.Builder(appUrl: appUrl, environmentId: environmentId)
+            .setLogLevel(.debug)
+            .service(mockService)
+            .build()
+        Formbricks.setup(with: config)
+
+        // Logout without ever setting a userId — should not crash or error
+        XCTAssertNil(Formbricks.userManager?.userId)
+        Formbricks.logout()
+        XCTAssertNil(Formbricks.userManager?.userId, "userId should remain nil after logout")
+    }
+
+    // MARK: - setAttribute overload tests
+
+    func testSetAttributeDouble() {
+        let config = FormbricksConfig.Builder(appUrl: appUrl, environmentId: environmentId)
+            .setLogLevel(.debug)
+            .service(mockService)
+            .build()
+        Formbricks.setup(with: config)
+
+        // Should not crash; exercises the Double overload
+        Formbricks.setAttribute(42.0, forKey: "age")
+    }
+
+    func testSetAttributeDate() {
+        let config = FormbricksConfig.Builder(appUrl: appUrl, environmentId: environmentId)
+            .setLogLevel(.debug)
+            .service(mockService)
+            .build()
+        Formbricks.setup(with: config)
+
+        // Should not crash; exercises the Date overload
+        Formbricks.setAttribute(Date(), forKey: "signupDate")
+    }
+
+    // MARK: - ConfigBuilder coverage tests
+
+    func testConfigBuilderStringAttributes() {
+        let config = FormbricksConfig.Builder(appUrl: appUrl, environmentId: environmentId)
+            .set(stringAttributes: ["key1": "val1", "key2": "val2"])
+            .build()
+
+        XCTAssertEqual(config.attributes?["key1"], "val1")
+        XCTAssertEqual(config.attributes?["key2"], "val2")
+    }
+
+    func testConfigBuilderAddAttribute() {
+        let config = FormbricksConfig.Builder(appUrl: appUrl, environmentId: environmentId)
+            .add(attribute: "hello", forKey: "greeting")
+            .build()
+
+        XCTAssertEqual(config.attributes?["greeting"], "hello")
+    }
+
     // MARK: - PresentSurveyManager tests
 
     func testPresentCompletesInHeadlessEnvironment() {
diff --git a/Tests/FormbricksSDKTests/Mock/UserWithErrors.json b/Tests/FormbricksSDKTests/Mock/UserWithErrors.json
new file mode 100644
index 00000000..a32a7aa7
--- /dev/null
+++ b/Tests/FormbricksSDKTests/Mock/UserWithErrors.json
@@ -0,0 +1,19 @@
+{
+  "data": {
+    "state": {
+      "data": {
+        "contactId": "cm6ovw6jl000hsf0knn547xyz",
+        "displays": [],
+        "lastDisplayAt": null,
+        "responses": [],
+        "segments": ["cm6ovw6jl000hsf0knn547w0y"],
+        "userId": "6CCCE716-6783-4D0F-8344-9C7DFA43D8F7"
+      },
+      "expiresAt": "2035-03-06T10:59:32.359Z"
+    },
+    "errors": [
+      "Attribute 'invalidKey' does not exist",
+      "Type mismatch for attribute 'age': expected number, got string"
+    ]
+  }
+}
diff --git a/Tests/FormbricksSDKTests/Mock/UserWithErrorsAndMessages.json b/Tests/FormbricksSDKTests/Mock/UserWithErrorsAndMessages.json
new file mode 100644
index 00000000..f21fd3ce
--- /dev/null
+++ b/Tests/FormbricksSDKTests/Mock/UserWithErrorsAndMessages.json
@@ -0,0 +1,21 @@
+{
+  "data": {
+    "state": {
+      "data": {
+        "contactId": "cm6ovw6jl000hsf0knn547xyz",
+        "displays": [],
+        "lastDisplayAt": null,
+        "responses": [],
+        "segments": ["cm6ovw6jl000hsf0knn547w0y"],
+        "userId": "6CCCE716-6783-4D0F-8344-9C7DFA43D8F7"
+      },
+      "expiresAt": "2035-03-06T10:59:32.359Z"
+    },
+    "messages": [
+      "Attribute 'email' already exists for this contact"
+    ],
+    "errors": [
+      "Attribute 'invalidKey' does not exist"
+    ]
+  }
+}
diff --git a/Tests/FormbricksSDKTests/Mock/UserWithMessages.json b/Tests/FormbricksSDKTests/Mock/UserWithMessages.json
new file mode 100644
index 00000000..d34957b7
--- /dev/null
+++ b/Tests/FormbricksSDKTests/Mock/UserWithMessages.json
@@ -0,0 +1,19 @@
+{
+  "data": {
+    "state": {
+      "data": {
+        "contactId": "cm6ovw6jl000hsf0knn547xyz",
+        "displays": [],
+        "lastDisplayAt": null,
+        "responses": [],
+        "segments": ["cm6ovw6jl000hsf0knn547w0y"],
+        "userId": "6CCCE716-6783-4D0F-8344-9C7DFA43D8F7"
+      },
+      "expiresAt": "2035-03-06T10:59:32.359Z"
+    },
+    "messages": [
+      "Attribute 'email' already exists for this contact",
+      "Contact successfully updated"
+    ]
+  }
+}
diff --git a/Tests/FormbricksSDKTests/MockFormbricksService/MockFormbricksService.swift b/Tests/FormbricksSDKTests/MockFormbricksService/MockFormbricksService.swift
index ad23504b..0a560dda 100644
--- a/Tests/FormbricksSDKTests/MockFormbricksService/MockFormbricksService.swift
+++ b/Tests/FormbricksSDKTests/MockFormbricksService/MockFormbricksService.swift
@@ -5,11 +5,17 @@ import UIKit
 enum MockResponse: String {
     case environment = "Environment"
     case user = "User"
+    case userWithErrors = "UserWithErrors"
+    case userWithMessages = "UserWithMessages"
+    case userWithErrorsAndMessages = "UserWithErrorsAndMessages"
 }
 
 class MockFormbricksService: FormbricksService {
     
     var isErrorResponseNeeded = false
+    /// Controls which mock JSON file is used for postUser responses.
+    /// Defaults to `.user` (the standard User.json).
+    var userMockResponse: MockResponse = .user
     
     override func getEnvironmentState(completion: @escaping (ResultType<GetEnvironmentRequest.Response>) -> Void) {
         if isErrorResponseNeeded {
@@ -19,11 +25,11 @@ class MockFormbricksService: FormbricksService {
         }
     }
     
-    override func postUser(id: String, attributes: [String : String]?, completion: @escaping (ResultType<PostUserRequest.Response>) -> Void) {
+    override func postUser(id: String, attributes: [String : AttributeValue]?, completion: @escaping (ResultType<PostUserRequest.Response>) -> Void) {
         if isErrorResponseNeeded {
             completion(.failure(RuntimeError(message: "")))
         } else {
-            execute(.user, completion: completion)
+            execute(userMockResponse, completion: completion)
         }
     }
     
diff --git a/Tests/FormbricksSDKTests/Networking/UpdateQueueTests.swift b/Tests/FormbricksSDKTests/Networking/UpdateQueueTests.swift
index 65dd30c3..c22f16a8 100644
--- a/Tests/FormbricksSDKTests/Networking/UpdateQueueTests.swift
+++ b/Tests/FormbricksSDKTests/Networking/UpdateQueueTests.swift
@@ -3,9 +3,9 @@ import XCTest
 
 class MockUserManager: UserManagerSyncable {
     var lastSyncedUserId: String?
-    var lastSyncedAttributes: [String: String]?
+    var lastSyncedAttributes: [String: AttributeValue]?
     var syncCallCount = 0
-    func syncUser(withId id: String, attributes: [String : String]?) {
+    func syncUser(withId id: String, attributes: [String : AttributeValue]?) {
         lastSyncedUserId = id
         lastSyncedAttributes = attributes
         syncCallCount += 1
@@ -73,6 +73,17 @@ final class UpdateQueueTests: XCTestCase {
         }
         wait(for: [exp], timeout: 1.0)
     }
+
+    func testAddNumberAttribute() {
+        let exp = expectation(description: "Add number attribute")
+        queue.set(userId: "user123")
+        queue.add(attribute: 42.0, forKey: "age")
+        DispatchQueue.main.asyncAfter(deadline: .now() + 0.6) {
+            XCTAssertEqual(self.mockUserManager.lastSyncedAttributes?["age"], 42.0)
+            exp.fulfill()
+        }
+        wait(for: [exp], timeout: 1.0)
+    }
     
     func testSetLanguageWithUserId() {
         let exp = expectation(description: "Set language with userId triggers commit")
@@ -133,4 +144,4 @@ final class UpdateQueueTests: XCTestCase {
         }
         wait(for: [exp], timeout: 1.0)
     }
-} 
\ No newline at end of file
+}