diff --git a/DriveClient/Helpers/KDriveJsonContext.cs b/DriveClient/Helpers/KDriveJsonContext.cs
index aaebc90..1892454 100644
--- a/DriveClient/Helpers/KDriveJsonContext.cs
+++ b/DriveClient/Helpers/KDriveJsonContext.cs
@@ -11,6 +11,7 @@ namespace kDriveClient.Helpers
     [JsonSerializable(typeof(KDriveFile))]
     [JsonSerializable(typeof(KDriveChunk))]
     [JsonSerializable(typeof(KDriveUploadResponseWraper))]
+    [JsonSerializable(typeof(KDriveFinishRequest))]
     [JsonSourceGenerationOptions(PropertyNameCaseInsensitive = true)]
     public partial class KDriveJsonContext : JsonSerializerContext
     {
diff --git a/DriveClient/Helpers/KDriveRequestFactory.cs b/DriveClient/Helpers/KDriveRequestFactory.cs
index 5b62359..ce81a4b 100644
--- a/DriveClient/Helpers/KDriveRequestFactory.cs
+++ b/DriveClient/Helpers/KDriveRequestFactory.cs
@@ -74,11 +74,8 @@ public static HttpRequestMessage CreateChunkUploadRequest(string baseUrl, string
         /// <returns>An HttpRequestMessage configured to finish the upload session.</returns>
         public static HttpRequestMessage CreateFinishSessionRequest(long driveId, string sessionToken, string totalChunkHash)
         {
-            var content = new StringContent(JsonSerializer.Serialize(new
-            {
-                total_chunk_hash = $"sha256:{totalChunkHash.ToLowerInvariant()}"
-            }, KDriveJsonContext.Default.Object));
-
+            // Send empty JSON body - kDrive validates file integrity via individual chunk hashes
+            var content = new StringContent("{}");
             content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
 
             return new HttpRequestMessage(HttpMethod.Post, $"/3/drive/{driveId}/upload/session/{sessionToken}/finish")
diff --git a/DriveClient/Models/KDriveFile.cs b/DriveClient/Models/KDriveFile.cs
index 848447a..7fd2b91 100644
--- a/DriveClient/Models/KDriveFile.cs
+++ b/DriveClient/Models/KDriveFile.cs
@@ -1,4 +1,6 @@
-namespace kDriveClient.Models
+using System.Text;
+
+namespace kDriveClient.Models
 {
     /// <summary>
     /// KDriveFile represents a file in the kDrive system.
@@ -36,14 +38,17 @@ public class KDriveFile
         public string? SymbolicLink { get; set; }
 
         /// <summary>
-        /// TotalChunkHash is the SHA-256 hash of the entire file content, computed from all chunks.
+        /// TotalChunkHash is the SHA-256 hash of the entire file content.
         /// </summary>
         public string TotalChunkHash
         {
             get
             {
-                return Convert.ToHexString(
-                        SHA256.HashData(this.Content));
+                var originalPosition = this.Content.Position;
+                this.Content.Position = 0;
+                var hash = Convert.ToHexString(SHA256.HashData(this.Content));
+                this.Content.Position = originalPosition;
+                return hash;
             }
         }
 
@@ -82,7 +87,8 @@ public void SplitIntoChunks(int chunkSize)
             while ((bytesRead = this.Content.Read(buffer, 0, chunkSize)) > 0)
             {
                 byte[] content = [.. buffer.Take(bytesRead)];
-                this.Chunks.Add(new KDriveChunk(content, chunkNumber++, SHA256.HashData(content)));
+                var chunkHash = SHA256.HashData(content);
+                this.Chunks.Add(new KDriveChunk(content, chunkNumber++, chunkHash));
             }
 
             this.Content.Position = 0;
diff --git a/DriveClient/Models/KDriveFinishRequest.cs b/DriveClient/Models/KDriveFinishRequest.cs
new file mode 100644
index 0000000..b02e2f9
--- /dev/null
+++ b/DriveClient/Models/KDriveFinishRequest.cs
@@ -0,0 +1,16 @@
+using System.Text.Json.Serialization;
+
+namespace kDriveClient.Models
+{
+    /// <summary>
+    /// Represents the request body for finishing an upload session.
+    /// </summary>
+    public class KDriveFinishRequest
+    {
+        /// <summary>
+        /// The total chunk hash of the uploaded file.
+        /// </summary>
+        [JsonPropertyName("total_chunk_hash")]
+        public string TotalChunkHash { get; set; } = string.Empty;
+    }
+}
diff --git a/DriveClient/kDriveClient/KDriveClient.cs b/DriveClient/kDriveClient/KDriveClient.cs
index b3d0b06..c5666b0 100644
--- a/DriveClient/kDriveClient/KDriveClient.cs
+++ b/DriveClient/kDriveClient/KDriveClient.cs
@@ -81,7 +81,7 @@ public KDriveClient(string token, long driveId, ILogger<KDriveClient>? logger) :
         /// <param name="autoChunk">Choose if we should make a speed test to optimize chunks</param>
         /// <param name="parallelism">Number of parrallels threads</param>
         /// <param name="logger">Logger</param>
-        public KDriveClient(string token, long driveId, bool autoChunk, int parallelism, ILogger<KDriveClient>? logger) : this(token, driveId, autoChunk, parallelism, logger, null)
+        public KDriveClient(string token, long driveId, bool autoChunk, int parallelism, ILogger<KDriveClient>? logger) : this(token, driveId, autoChunk, parallelism, logger, null, null)
         { }
 
         /// <summary>
@@ -93,7 +93,8 @@ public KDriveClient(string token, long driveId, bool autoChunk, int parallelism,
         /// <param name="parallelism">Number of parrallels threads</param>
         /// <param name="logger">Logger</param>
         /// <param name="httpClient">Custome HttpClient</param>
-        public KDriveClient(string token, long driveId, bool autoChunk, int parallelism, ILogger<KDriveClient>? logger, HttpClient? httpClient = null)
+        /// <param name="chunkSize">Optional custom chunk size in bytes. If not specified, will be calculated dynamically based on speed test when autoChunk is true.</param>
+        public KDriveClient(string token, long driveId, bool autoChunk, int parallelism, ILogger<KDriveClient>? logger, HttpClient? httpClient = null, int? chunkSize = null)
         {
             DriveId = driveId;
             Parallelism = parallelism;
@@ -103,12 +104,25 @@ public KDriveClient(string token, long driveId, bool autoChunk, int parallelism,
             HttpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
             HttpClient.DefaultRequestHeaders.UserAgent.ParseAdd("kDriveClient.NET/version");
             this.Logger?.LogInformation("KDriveClient initialized with Drive ID: {DriveId}", DriveId);
+
+            if (chunkSize.HasValue)
+            {
+                DynamicChunkSizeBytes = chunkSize.Value;
+                this.Logger?.LogInformation("Using custom chunk size: {ChunkSize} bytes", DynamicChunkSizeBytes);
+            }
+
             if (autoChunk)
             {
                 this.Logger?.LogInformation("Auto chunking enabled, initializing upload strategy...");
-                InitializeUploadStrategyAsync().GetAwaiter().GetResult();
+                InitializeUploadStrategyAsync(chunkSize).GetAwaiter().GetResult();
                 this.Logger?.LogInformation("Upload strategy initialized with direct upload threshold: {Threshold} bytes and dynamic chunk size: {ChunkSize} bytes", DirectUploadThresholdBytes, DynamicChunkSizeBytes);
             }
+            else if (!chunkSize.HasValue)
+            {
+                // If autoChunk is disabled and no custom chunk size provided, use a default
+                DynamicChunkSizeBytes = 1024 * 1024; // Default to 1MB chunks
+                this.Logger?.LogInformation("Using default chunk size: {ChunkSize} bytes", DynamicChunkSizeBytes);
+            }
         }
 
         /// <summary>
diff --git a/DriveClient/kDriveClient/SpeedTest.cs b/DriveClient/kDriveClient/SpeedTest.cs
index 753c025..97fb243 100644
--- a/DriveClient/kDriveClient/SpeedTest.cs
+++ b/DriveClient/kDriveClient/SpeedTest.cs
@@ -11,9 +11,10 @@ public partial class KDriveClient
         /// <summary>
         /// Initializes the upload strategy by performing a speed test.
         /// </summary>
+        /// <param name="customChunkSize">Optional custom chunk size in bytes. If specified, only DirectUploadThresholdBytes will be calculated from speed test.</param>
         /// <param name="ct">Cancellation token to cancel the operation.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
-        private async Task InitializeUploadStrategyAsync(CancellationToken ct = default)
+        private async Task InitializeUploadStrategyAsync(int? customChunkSize = null, CancellationToken ct = default)
         {
             this.Logger?.LogInformation("Starting upload strategy initialization...");
             var buffer = new byte[1024 * 1024];
@@ -65,9 +66,18 @@ private async Task InitializeUploadStrategyAsync(CancellationToken ct = default)
             var speedBytesPerSec = buffer.Length / (sw.ElapsedMilliseconds / 1000.0);
 
             DirectUploadThresholdBytes = (long)speedBytesPerSec;
-            DynamicChunkSizeBytes = (int)(speedBytesPerSec * 0.9);
-            this.Logger?.LogInformation("Upload strategy initialized: DirectUploadThresholdBytes = {DirectUploadThresholdBytes}, DynamicChunkSizeBytes = {DynamicChunkSizeBytes}",
-                DirectUploadThresholdBytes, DynamicChunkSizeBytes);
+
+            if (!customChunkSize.HasValue)
+            {
+                DynamicChunkSizeBytes = (int)(speedBytesPerSec * 0.9);
+                this.Logger?.LogInformation("Upload strategy initialized: DirectUploadThresholdBytes = {DirectUploadThresholdBytes}, DynamicChunkSizeBytes = {DynamicChunkSizeBytes} (calculated from speed test)",
+                    DirectUploadThresholdBytes, DynamicChunkSizeBytes);
+            }
+            else
+            {
+                this.Logger?.LogInformation("Upload strategy initialized: DirectUploadThresholdBytes = {DirectUploadThresholdBytes}, DynamicChunkSizeBytes = {DynamicChunkSizeBytes} (custom)",
+                    DirectUploadThresholdBytes, DynamicChunkSizeBytes);
+            }
         }
     }
 }
\ No newline at end of file