How to Create a Comment in a Task and Attach a File

Scope: drive, tasks

Who can execute the method: users with access to the drive and tasks sections

If you are developing integrations for Bitrix24 using AI tools (Codex, Claude Code, Cursor), connect to the MCP server so that the assistant can utilize the official REST documentation.

In Bitrix24, there are two types of file fields:

File. This field is not linked to the drive; files are uploaded directly through a Base64 format string.
File (drive). This field is linked to the drive, storing the ID of the drive object. The Base64 format is not processed in this field, so the file must first be uploaded to the Bitrix24 drive.

To create a comment in a task and attach a file, we will sequentially execute two methods:

drive.folder.uploadfile — this method uploads a file to the drive.
task.commentitem.add — this method creates a comment.

1. Uploading a File to the Bitrix24 Drive

To upload a file to the drive, we use the method drive.folder.uploadfile with the following parameters:

id — we will specify the value 1739 — the identifier of the drive folder where we are uploading the file.
data — we will specify the file name NAME, which will be the name under which the file is saved on the Bitrix24 drive.
fileContent — we pass the file in the format ['file_name.extension', 'file as a Base64 encoded string'].

Uploading the file to the drive is a necessary step, as the UF_FORUM_MESSAGE_DOC field in comments only accepts the IDs of drive files.

How to Use Examples in Documentation

PHP

Python

BX24.callMethod(
            "drive.folder.uploadfile",
            {
                id: 1739,
                data: {
                    NAME: "file.pdf"
                },
                fileContent: [
                    'file555.pdf',
                    '/9j/4AAQSkZJRgABAQEASABIAAD/2wBDAAQDAwQDAwQEAwQ///+dAYq6YFKoAv/AFnAa6ArKv8AAtFJVppxCEAulxQ2DWgfMR//2Q=='
                ]
            }
        );

require_once('crest.php');
        
        $result = CRest::call(
            'drive.folder.uploadfile',
            [
                'id' => 1739,
                'data' => [
                    'NAME' => 'file.pdf'
                ],
                'fileContent' => [
                    'file555.pdf',
                    '/9j/4AAQSkZJRgABAQEASABIAAD/2wBDAAQDAwQDAwQEAwQ///+dAYq6YFKoAv/AFnAa6ArKv8AAtFJVppxCEAulxQ2DWgfMR//2Q=='
                ]
            ]
        );

from b24pysdk import BitrixWebhook, Client
        
        
        client = Client(
            BitrixWebhook(
                domain="your-domain.bitrix24.com",
                auth_token="your-webhook-token",
            )
        )
        
        response = client.disk.folder.uploadfile(
            bitrix_id=1739,
            data={
                "NAME": "file.pdf",
            },
            file_content=[
                "file555.pdf",
                "/9j/4AAQSkZJRgABAQEASABIAAD/2wBDAAQDAwQDAwQEAwQ///+dAYq6YFKoAv/AFnAa6ArKv8AAtFJVppxCEAulxQ2DWgfMR//2Q==",
            ],
        ).response

As a result of uploading the file to the drive, we receive two different file ID values:

FILE_ID: 28073 — the internal file ID value.
ID: 6687 — the drive object ID, which we will use in methods for working with fields of the "file (drive)" type. If we pass the FILE_ID value in the request to modify the "file (drive)" field, the file will either not be attached to the task because there is no drive object with that ID, or the wrong file will be attached.

{
            "result": {
                "ID": 6687,
                "NAME": "file.pdf",
                "CODE": null,
                "STORAGE_ID": "1",
                "TYPE": "file",
                "PARENT_ID": "1739",
                "DELETED_TYPE": 0,
                "GLOBAL_CONTENT_VERSION": 1,
                "FILE_ID": 28073,
                "SIZE": "405559",
                "CREATE_TIME": "2024-11-01T17:00:55+01:00",
                "UPDATE_TIME": "2024-11-01T17:00:55+01:00",
                "DELETE_TIME": null,
                "CREATED_BY": "1",
                "UPDATED_BY": "1",
                "DELETED_BY": null,
                "DOWNLOAD_URL": "https://your-domain.bitrix24.com/rest/download.json?sessid=9dd90ed5a58ccc41af81f5f0043739db&token=disk%7CaWQ9NjY4NyZfPTJ5ZXdvN2Fsb09SMGw1b0FHTkRMSGR5MFJkN1pLTjNS%7CImRvd25sb2FkfGRpc2t8YVdROU5qWTROeVpmUFRKNVpYZHZOMkZzYjA5U01HdzFiMEZIVGtSTVNHUjVNRkprTjFwTFRqTlN8OWRkOTBlZDVhNThjY2M0MWFmODFmNWYwMDQzNzM5ZGIi.Lup1vDbibL6twiCPfCMFnLSoDLleNX0cfMHGv5PFaJw%3D",
                "DETAIL_URL": "https://your-domain.bitrix24.com/company/personal/user/1/drive/file/Created files/New test folder/file.pdf"
            }
        }

2. Creating a Comment and Attaching a File

To create a comment in a task, we use the method task.commentitem.add with the following parameters:

TASKID — the ID of the task, a required field. Without the task ID, the comment will not be created. To obtain the task ID, we use the method tasks.task.list.
AUTHOR_ID — the ID of the comment author. This parameter can be omitted, in which case the author will automatically be the employee from whose account the request is made.
POST_MESSAGE — the text of the comment.
UF_FORUM_MESSAGE_DOC — we will specify the value n6687. This is the drive file ID from the result of the previous method, to which we add the prefix n for uploading the file to the field.

PHP

Python

BX24.callMethod(
            'task.commentitem.add',
            {
                TASKID: 3711,
                FIELDS: {
                    POST_MESSAGE: 'comment for test',
                    AUTHOR_ID: 29,
                    UF_FORUM_MESSAGE_DOC: [
                        "n6687"
                    ]
                }
            }
        );

require_once('crest.php');
        
        $result = CRest::call(
            'task.commentitem.add',
            [
                'TASKID' => 3711,
                'FIELDS' => [
                    'POST_MESSAGE' => 'comment for test',
                    'AUTHOR_ID' => 29,
                    'UF_FORUM_MESSAGE_DOC' => [
                        'n6687'
                    ]
                ]
            ]
        );

response = client.task.commentitem.add(
            task_id=3711,
            fields={
                "POST_MESSAGE": "comment for test",
                "AUTHOR_ID": 29,
                "UF_FORUM_MESSAGE_DOC": [
                    "n6687",
                ],
            },
        ).response

We created a comment with ID 9393.

{
            "result": 9393
        }

In the received result, there is no information about the file attached to the comment. To check if the file was successfully attached, we will execute the method task.commentitem.get.

Code Example

PHP

Python

// Function to upload a file
        function uploadFileToDrive() {
            // ID of the folder to which the file needs to be uploaded
            var folderId = 'FOLDER_ID';
            // File name and its content in Base64 format
            var fileName = 'file_name';
            var fileContentBase64 = 'file_content_Base64';
        
            // Call the method drive.folder.uploadfile
            BX24.callMethod(
                'drive.folder.uploadfile',
                {
                    id: folderId,
                    data: {
                        NAME: fileName
                    },
                    fileContent: [
                        fileName,
                        fileContentBase64
                    ]
                },
                function(result) {
                    if (result.error()) {
                        console.error('Error uploading file:', result.error());
                    } else {
                        console.log('File successfully uploaded!', result.data());
                        var fileId = result.data().ID; // Use ID from the result
                        createCommentWithFile(fileId);
                    }
                }
            );
        }
        
        // Function to create a comment with a file
        function createCommentWithFile(fileId) {
            // Comment parameters
            var taskID = 'TASK_ID';
            var commentMessage = 'comment_text';
            var authorId = 'AUTHOR_ID';
        
            // Call the method task.commentitem.add
            BX24.callMethod(
                'task.commentitem.add',
                {
                    TASKID: taskID,
                    FIELDS: {
                        POST_MESSAGE: commentMessage,
                        AUTHOR_ID: authorId,
                        UF_FORUM_MESSAGE_DOC: ['n' + fileId] // Add prefix 'n' to the file ID
                    }
                },
                function(result) {
                    if (result.error()) {
                        console.error('Error creating comment:', result.error());
                    } else {
                        console.log('Comment successfully created!', result.data());
                    }
                }
            );
        }
        
        // Call the function to upload a file and create a comment
        uploadFileToDrive();

require_once('crest.php');
        
        // Function to upload a file
        function uploadFileToDrive() {
            // ID of the folder to which the file needs to be uploaded
            $folderId = 'FOLDER_ID';
            // Name of the file you want to upload
            $fileName = 'file_name';
            // Path to the file on your file system
            $filePath = '/path/to/your/file';
        
            // Read the file content and encode it in Base64
            $fileContentBase64 = base64_encode(file_get_contents($filePath));
        
            // Call the method drive.folder.uploadfile
            $result = CRest::call(
                'drive.folder.uploadfile',
                [
                    'id' => $folderId,
                    'data' => [
                        'NAME' => $fileName
                    ],
                    'fileContent' => [
                        $fileName,
                        $fileContentBase64
                    ]
                ]
            );
        
            if (isset($result['error'])) {
                echo 'Error uploading file: ' . $result['error'];
            } else {
                echo 'File successfully uploaded!';
                $fileId = $result['result']['ID']; // Use ID from the result
                createCommentWithFile($fileId);
            }
        }
        
        // Function to create a comment with a file
        function createCommentWithFile($fileId) {
            // Comment parameters
            $taskID = 'TASK_ID';
            $commentMessage = 'comment_text';
            $authorId = 'AUTHOR_ID';
        
            // Call the method task.commentitem.add
            $result = CRest::call(
                'task.commentitem.add',
                [
                    'TASKID' => $taskID,
                    'FIELDS' => [
                        'POST_MESSAGE' => $commentMessage,
                        'AUTHOR_ID' => $authorId,
                        'UF_FORUM_MESSAGE_DOC' => ['n' . $fileId] // Add prefix 'n' to the file ID
                    ]
                ]
            );
        
            if (isset($result['error'])) {
                echo 'Error creating comment: ' . $result['error'];
            } else {
                echo 'Comment successfully created!';
            }
        }
        
        // Call the function to upload a file and create a comment
        uploadFileToDrive();

from b24pysdk import BitrixWebhook, Client
        from b24pysdk.errors import BitrixAPIError
        
        
        def upload_file_to_drive(client):
            folder_id = 1739
            file_name = "file_name"
            file_content_base64 = "file_content_Base64"
        
            try:
                result = client.disk.folder.uploadfile(
                    bitrix_id=folder_id,
                    data={"NAME": file_name},
                    file_content=[file_name, file_content_base64],
                ).response.result
            except BitrixAPIError as error:
                print(f"Error uploading file: {error}")
            else:
                print("File successfully uploaded!")
                file_id = result["ID"]
                create_comment_with_file(client, file_id)
        
        
        def create_comment_with_file(client, file_id):
            task_id = "TASK_ID"
            comment_message = "comment_text"
            author_id = "AUTHOR_ID"
        
            try:
                client.task.commentitem.add(
                    task_id=task_id,
                    fields={
                        "POST_MESSAGE": comment_message,
                        "AUTHOR_ID": author_id,
                        "UF_FORUM_MESSAGE_DOC": [f"n{file_id}"],
                    },
                ).response
            except BitrixAPIError as error:
                print(f"Error creating comment: {error}")
            else:
                print("Comment successfully created!")
        
        
        client = Client(
            BitrixWebhook(
                domain="your-domain.bitrix24.com",
                auth_token="your-webhook-token",
            )
        )
        
        upload_file_to_drive(client)

How to upload a file to a task

How to attach a task to an SPA

How to Create a Comment in a Task and Attach a File

1. Uploading a File to the Bitrix24 Drive1. Uploading a File to the Bitrix24 Drive

2. Creating a Comment and Attaching a File2. Creating a Comment and Attaching a File

Code ExampleCode Example

1. Uploading a File to the Bitrix24 Drive

2. Creating a Comment and Attaching a File

Code Example