diff --git a/src/PSProxmoxVE.Core/Authentication/PveAuthMode.cs b/src/PSProxmoxVE.Core/Authentication/PveAuthMode.cs
new file mode 100644
index 0000000..2691ba3
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Authentication/PveAuthMode.cs
@@ -0,0 +1,9 @@
+namespace PSProxmoxVE.Core.Authentication
+{
+    /// <summary>Authentication mode for Proxmox VE API</summary>
+    public enum PveAuthMode
+    {
+        Ticket,
+        ApiToken
+    }
+}
diff --git a/src/PSProxmoxVE.Core/Authentication/PveAuthenticator.cs b/src/PSProxmoxVE.Core/Authentication/PveAuthenticator.cs
new file mode 100644
index 0000000..47ee43a
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Authentication/PveAuthenticator.cs
@@ -0,0 +1,110 @@
+using System;
+using System.Collections.Generic;
+using System.Text.RegularExpressions;
+using Newtonsoft.Json.Linq;
+using PSProxmoxVE.Core.Client;
+
+namespace PSProxmoxVE.Core.Authentication
+{
+    /// <summary>Provides methods to authenticate against a Proxmox VE server</summary>
+    public static class PveAuthenticator
+    {
+        // Pattern: USER@REALM!TOKENID=UUID
+        private static readonly Regex ApiTokenRegex = new Regex(
+            @"^[^@]+@[^!]+![^=]+=.+$",
+            RegexOptions.Compiled);
+
+        /// <summary>
+        /// Authenticates using username and password, obtaining a ticket and CSRF token.
+        /// The username must be in the form user@realm (e.g. root@pam).
+        /// </summary>
+        public static PveSession AuthenticateWithCredentials(
+            string hostname,
+            int port,
+            bool skipCertificateCheck,
+            string username,
+            string password)
+        {
+            if (string.IsNullOrWhiteSpace(hostname))
+                throw new ArgumentException("Hostname cannot be null or empty.", nameof(hostname));
+            if (string.IsNullOrWhiteSpace(username))
+                throw new ArgumentException("Username cannot be null or empty.", nameof(username));
+            if (!username.Contains("@"))
+                throw new ArgumentException("Username must include a realm (e.g. 'root@pam').", nameof(username));
+            if (password == null)
+                throw new ArgumentNullException(nameof(password));
+
+            var formData = new Dictionary<string, string>
+            {
+                { "username", username },
+                { "password", password }
+            };
+
+            string responseBody;
+            using (var httpClient = new PveHttpClient(hostname, port, skipCertificateCheck))
+            {
+                responseBody = httpClient.Post("/api2/json/access/ticket", formData);
+            }
+
+            var json = JObject.Parse(responseBody);
+            var data = json["data"] ?? throw new InvalidOperationException("Response did not contain a 'data' field.");
+
+            var ticket = data["ticket"]?.Value<string>()
+                ?? throw new InvalidOperationException("Response did not contain a ticket.");
+            var csrfToken = data["CSRFPreventionToken"]?.Value<string>()
+                ?? throw new InvalidOperationException("Response did not contain a CSRFPreventionToken.");
+
+            var ticketExpiry = DateTime.UtcNow.AddHours(2);
+
+            var session = new PveSession(hostname, port, skipCertificateCheck, ticket, csrfToken, ticketExpiry);
+
+            session.ServerVersion = GetVersion(session);
+
+            return session;
+        }
+
+        /// <summary>
+        /// Authenticates using a Proxmox VE API token.
+        /// The token must be in the format USER@REALM!TOKENID=UUID (e.g. root@pam!mytoken=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx).
+        /// </summary>
+        public static PveSession AuthenticateWithApiToken(
+            string hostname,
+            int port,
+            bool skipCertificateCheck,
+            string apiToken)
+        {
+            if (string.IsNullOrWhiteSpace(hostname))
+                throw new ArgumentException("Hostname cannot be null or empty.", nameof(hostname));
+            if (string.IsNullOrWhiteSpace(apiToken))
+                throw new ArgumentException("API token cannot be null or empty.", nameof(apiToken));
+            if (!ApiTokenRegex.IsMatch(apiToken))
+                throw new ArgumentException(
+                    "API token must be in the format 'USER@REALM!TOKENID=UUID' (e.g. root@pam!mytoken=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx).",
+                    nameof(apiToken));
+
+            var session = new PveSession(hostname, port, skipCertificateCheck, apiToken);
+
+            session.ServerVersion = GetVersion(session);
+
+            return session;
+        }
+
+        /// <summary>Retrieves and parses the server version from the PVE API</summary>
+        private static PveVersion GetVersion(PveSession session)
+        {
+            string responseBody;
+            using (var httpClient = new PveHttpClient(session))
+            {
+                responseBody = httpClient.Get("/api2/json/version");
+            }
+
+            var json = JObject.Parse(responseBody);
+            var data = json["data"] ?? throw new InvalidOperationException("Version response did not contain a 'data' field.");
+
+            var versionString = data["version"]?.Value<string>()
+                ?? throw new InvalidOperationException("Version response did not contain a 'version' field.");
+
+            return PveVersion.Parse(versionString);
+        }
+    }
+}
diff --git a/src/PSProxmoxVE.Core/Authentication/PveSession.cs b/src/PSProxmoxVE.Core/Authentication/PveSession.cs
new file mode 100644
index 0000000..cdbb587
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Authentication/PveSession.cs
@@ -0,0 +1,66 @@
+using System;
+using PSProxmoxVE.Core.Models;
+
+namespace PSProxmoxVE.Core.Authentication
+{
+    /// <summary>Represents an authenticated session to a Proxmox VE server</summary>
+    public class PveSession
+    {
+        public string Hostname { get; }
+        public int Port { get; }
+        public bool SkipCertificateCheck { get; }
+        public PveAuthMode AuthMode { get; }
+        public string? ApiToken { get; }
+        public string? Ticket { get; }
+        public string? CsrfToken { get; }
+        public DateTime TicketExpiry { get; }
+        public PveVersion ServerVersion { get; internal set; }
+
+        /// <summary>Returns true if the ticket has expired (only relevant for Ticket auth mode)</summary>
+        public bool IsExpired
+        {
+            get
+            {
+                if (AuthMode == PveAuthMode.ApiToken)
+                    return false;
+                return DateTime.UtcNow >= TicketExpiry;
+            }
+        }
+
+        /// <summary>Base URL for the Proxmox VE API</summary>
+        public string BaseUrl => $"https://{Hostname}:{Port}/api2/json";
+
+        /// <summary>Creates a session using ticket-based authentication</summary>
+        internal PveSession(
+            string hostname,
+            int port,
+            bool skipCertificateCheck,
+            string ticket,
+            string csrfToken,
+            DateTime ticketExpiry)
+        {
+            Hostname = hostname;
+            Port = port;
+            SkipCertificateCheck = skipCertificateCheck;
+            AuthMode = PveAuthMode.Ticket;
+            Ticket = ticket;
+            CsrfToken = csrfToken;
+            TicketExpiry = ticketExpiry;
+        }
+
+        /// <summary>Creates a session using API token authentication</summary>
+        internal PveSession(
+            string hostname,
+            int port,
+            bool skipCertificateCheck,
+            string apiToken)
+        {
+            Hostname = hostname;
+            Port = port;
+            SkipCertificateCheck = skipCertificateCheck;
+            AuthMode = PveAuthMode.ApiToken;
+            ApiToken = apiToken;
+            TicketExpiry = DateTime.MaxValue;
+        }
+    }
+}
diff --git a/src/PSProxmoxVE.Core/Authentication/PveVersion.cs b/src/PSProxmoxVE.Core/Authentication/PveVersion.cs
new file mode 100644
index 0000000..ebcdac3
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Authentication/PveVersion.cs
@@ -0,0 +1,44 @@
+using System;
+
+namespace PSProxmoxVE.Core.Authentication
+{
+    /// <summary>Represents a Proxmox VE server version (major.minor only)</summary>
+    public class PveVersion
+    {
+        public int Major { get; }
+        public int Minor { get; }
+
+        public PveVersion(int major, int minor)
+        {
+            Major = major;
+            Minor = minor;
+        }
+
+        /// <summary>Parse version from PVE API format "major.minor-patchlevel" e.g. "9.1-1"</summary>
+        public static PveVersion Parse(string versionString)
+        {
+            if (string.IsNullOrWhiteSpace(versionString))
+                throw new ArgumentException("Version string cannot be null or empty.", nameof(versionString));
+
+            // Strip patchlevel: "9.1-1" -> "9.1"
+            var dashIndex = versionString.IndexOf('-');
+            var majorMinor = dashIndex >= 0 ? versionString.Substring(0, dashIndex) : versionString;
+
+            var parts = majorMinor.Split('.');
+            if (parts.Length < 2)
+                throw new FormatException($"Invalid PVE version format: '{versionString}'. Expected 'major.minor' or 'major.minor-patchlevel'.");
+
+            if (!int.TryParse(parts[0], out var major) || !int.TryParse(parts[1], out var minor))
+                throw new FormatException($"Invalid PVE version format: '{versionString}'. Major and minor must be integers.");
+
+            return new PveVersion(major, minor);
+        }
+
+        public bool IsAtLeast(int major, int minor)
+        {
+            return Major > major || (Major == major && Minor >= minor);
+        }
+
+        public override string ToString() => $"{Major}.{Minor}";
+    }
+}
diff --git a/src/PSProxmoxVE.Core/Exceptions/PveApiException.cs b/src/PSProxmoxVE.Core/Exceptions/PveApiException.cs
new file mode 100644
index 0000000..1d76a80
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Exceptions/PveApiException.cs
@@ -0,0 +1,29 @@
+using System;
+using System.Net;
+
+namespace PSProxmoxVE.Core.Exceptions
+{
+    /// <summary>Exception thrown when the Proxmox VE API returns an error response</summary>
+    public class PveApiException : Exception
+    {
+        public HttpStatusCode StatusCode { get; }
+        public string Resource { get; }
+        public string HttpMethod { get; }
+
+        public PveApiException(HttpStatusCode statusCode, string message, string resource, string httpMethod)
+            : base($"PVE API error ({(int)statusCode} {statusCode}) on {httpMethod} {resource}: {message}")
+        {
+            StatusCode = statusCode;
+            Resource = resource;
+            HttpMethod = httpMethod;
+        }
+
+        public PveApiException(HttpStatusCode statusCode, string message, string resource, string httpMethod, Exception innerException)
+            : base($"PVE API error ({(int)statusCode} {statusCode}) on {httpMethod} {resource}: {message}", innerException)
+        {
+            StatusCode = statusCode;
+            Resource = resource;
+            HttpMethod = httpMethod;
+        }
+    }
+}
diff --git a/src/PSProxmoxVE.Core/Exceptions/PveAuthenticationException.cs b/src/PSProxmoxVE.Core/Exceptions/PveAuthenticationException.cs
new file mode 100644
index 0000000..6d4112c
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Exceptions/PveAuthenticationException.cs
@@ -0,0 +1,18 @@
+using System;
+
+namespace PSProxmoxVE.Core.Exceptions
+{
+    /// <summary>Exception thrown when authentication to a Proxmox VE server fails</summary>
+    public class PveAuthenticationException : Exception
+    {
+        public PveAuthenticationException(string message)
+            : base(message)
+        {
+        }
+
+        public PveAuthenticationException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+    }
+}
diff --git a/src/PSProxmoxVE.Core/Exceptions/PveNotConnectedException.cs b/src/PSProxmoxVE.Core/Exceptions/PveNotConnectedException.cs
new file mode 100644
index 0000000..296bedd
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Exceptions/PveNotConnectedException.cs
@@ -0,0 +1,18 @@
+using System;
+
+namespace PSProxmoxVE.Core.Exceptions
+{
+    /// <summary>Exception thrown when an operation is attempted without an active Proxmox VE session</summary>
+    public class PveNotConnectedException : Exception
+    {
+        public PveNotConnectedException()
+            : base("No active Proxmox VE session. Run Connect-PveServer first.")
+        {
+        }
+
+        public PveNotConnectedException(Exception innerException)
+            : base("No active Proxmox VE session. Run Connect-PveServer first.", innerException)
+        {
+        }
+    }
+}
diff --git a/src/PSProxmoxVE.Core/Exceptions/PveSessionExpiredException.cs b/src/PSProxmoxVE.Core/Exceptions/PveSessionExpiredException.cs
new file mode 100644
index 0000000..eb78e03
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Exceptions/PveSessionExpiredException.cs
@@ -0,0 +1,18 @@
+using System;
+
+namespace PSProxmoxVE.Core.Exceptions
+{
+    /// <summary>Exception thrown when the Proxmox VE session ticket has expired</summary>
+    public class PveSessionExpiredException : Exception
+    {
+        public PveSessionExpiredException()
+            : base("Your Proxmox VE session has expired. Please run Connect-PveServer to establish a new session.")
+        {
+        }
+
+        public PveSessionExpiredException(Exception innerException)
+            : base("Your Proxmox VE session has expired. Please run Connect-PveServer to establish a new session.", innerException)
+        {
+        }
+    }
+}
diff --git a/src/PSProxmoxVE.Core/Exceptions/PveTaskFailedException.cs b/src/PSProxmoxVE.Core/Exceptions/PveTaskFailedException.cs
new file mode 100644
index 0000000..0b99ffd
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Exceptions/PveTaskFailedException.cs
@@ -0,0 +1,25 @@
+using System;
+
+namespace PSProxmoxVE.Core.Exceptions
+{
+    /// <summary>Exception thrown when a Proxmox VE task completes with a failed exit status</summary>
+    public class PveTaskFailedException : Exception
+    {
+        public string Upid { get; }
+        public string ExitStatus { get; }
+
+        public PveTaskFailedException(string upid, string exitStatus)
+            : base($"Task {upid} failed with exit status: {exitStatus}")
+        {
+            Upid = upid;
+            ExitStatus = exitStatus;
+        }
+
+        public PveTaskFailedException(string upid, string exitStatus, Exception innerException)
+            : base($"Task {upid} failed with exit status: {exitStatus}", innerException)
+        {
+            Upid = upid;
+            ExitStatus = exitStatus;
+        }
+    }
+}
diff --git a/src/PSProxmoxVE.Core/Exceptions/PveTaskTimeoutException.cs b/src/PSProxmoxVE.Core/Exceptions/PveTaskTimeoutException.cs
new file mode 100644
index 0000000..3d5d725
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Exceptions/PveTaskTimeoutException.cs
@@ -0,0 +1,25 @@
+using System;
+
+namespace PSProxmoxVE.Core.Exceptions
+{
+    /// <summary>Exception thrown when a Proxmox VE task does not complete within the allowed timeout period</summary>
+    public class PveTaskTimeoutException : Exception
+    {
+        public string Upid { get; }
+        public TimeSpan Timeout { get; }
+
+        public PveTaskTimeoutException(string upid, TimeSpan timeout)
+            : base($"Task {upid} did not complete within {timeout.TotalSeconds} seconds.")
+        {
+            Upid = upid;
+            Timeout = timeout;
+        }
+
+        public PveTaskTimeoutException(string upid, TimeSpan timeout, Exception innerException)
+            : base($"Task {upid} did not complete within {timeout.TotalSeconds} seconds.", innerException)
+        {
+            Upid = upid;
+            Timeout = timeout;
+        }
+    }
+}
diff --git a/src/PSProxmoxVE.Core/Exceptions/PveVersionException.cs b/src/PSProxmoxVE.Core/Exceptions/PveVersionException.cs
new file mode 100644
index 0000000..e2606a8
--- /dev/null
+++ b/src/PSProxmoxVE.Core/Exceptions/PveVersionException.cs
@@ -0,0 +1,29 @@
+using System;
+using PSProxmoxVE.Core.Authentication;
+
+namespace PSProxmoxVE.Core.Exceptions
+{
+    /// <summary>Exception thrown when the connected Proxmox VE server does not meet the minimum version requirement for an operation</summary>
+    public class PveVersionException : Exception
+    {
+        public int RequiredMajor { get; }
+        public int RequiredMinor { get; }
+        public PveVersion ActualVersion { get; }
+
+        public PveVersionException(int requiredMajor, int requiredMinor, PveVersion actualVersion)
+            : base($"This operation requires Proxmox VE {requiredMajor}.{requiredMinor} or later. Connected server is version {actualVersion}.")
+        {
+            RequiredMajor = requiredMajor;
+            RequiredMinor = requiredMinor;
+            ActualVersion = actualVersion;
+        }
+
+        public PveVersionException(int requiredMajor, int requiredMinor, PveVersion actualVersion, Exception innerException)
+            : base($"This operation requires Proxmox VE {requiredMajor}.{requiredMinor} or later. Connected server is version {actualVersion}.", innerException)
+        {
+            RequiredMajor = requiredMajor;
+            RequiredMinor = requiredMinor;
+            ActualVersion = actualVersion;
+        }
+    }
+}