Architecting Custom Web Messaging Attachments via Open Messaging and External Hosting

How-To-Articles
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Architecting Custom Web Messaging Attachments via Open Messaging and External Hosting

What This Guide Covers

  • Bypassing the native file size and file type restrictions of Genesys Cloud Web Messaging by implementing a custom attachment handler via the Open Messaging API.
  • Architecting an external media hosting pipeline (using AWS S3 and API Gateway) to securely receive, scan, and serve customer attachments to agents within the Genesys Cloud UI.
  • The end result is a highly flexible digital channel capable of handling massive files (e.g., raw video evidence for insurance claims) without running into the platform’s standard payload limits.

Prerequisites, Roles & Licensing

  • Licensing: Genesys Cloud CX 2 or 3 (Digital).
  • Permissions: Messaging > Integration > Edit, Architect > Flow > Edit.
  • Infrastructure: AWS Account with S3, API Gateway, and Lambda (or equivalent Azure/GCP services).
  • API Access: OAuth Client Credentials with messaging scopes.

The Implementation Deep-Dive

1. The Limitation of Native Attachments

Native Genesys Cloud Web Messaging has strict limits on attachment sizes (usually 10MB to 25MB depending on the region) and restricted MIME types. For industries like insurance or healthcare, customers often need to upload high-resolution video files or specialized document formats (e.g., DICOM) that exceed these limits.

Architectural Reasoning:
Do not attempt to base64 encode massive files and stuff them into native Guest Attributes or interaction data. This will crash the agent desktop or result in HTTP 413 (Entity Too Large) errors. Instead, use an External Reference Pattern via Open Messaging.

2. Building the External Media Pipeline (AWS S3)

The customer never uploads the file directly to Genesys Cloud. They upload it to your custom infrastructure.

Implementation Steps:

  1. The Custom Chat Widget: Build a custom frontend chat UI (do not use the native Genesys Messenger widget) that interfaces with your backend.
  2. The Upload Endpoint: When a user clicks “Attach,” your frontend requests a Pre-Signed S3 URL from your AWS API Gateway.
  3. Direct-to-S3 Upload: The browser uploads the massive file directly to S3 using the pre-signed URL. This bypasses your API’s memory limits.
  4. Virus Scanning: Configure an S3 Event Notification to trigger a Lambda function that scans the file for malware (using ClamAV or similar).
  5. Generate Secure Link: If the file is clean, the Lambda function generates a temporary, signed “Read” URL for the file.

3. Injecting the Attachment via Open Messaging

Now that the file is safely stored and scanned, you must present it to the agent.

Implementation Steps:

  1. Your backend server uses the Genesys Cloud Open Messaging API to send a message to the active conversation thread.
  2. The payload must use the NormalizedMessage schema.
  3. The Attachment Array: Include the S3 Read URL in the content array of the Open Message payload:
{
  "id": "msg-12345",
  "channel": { ... },
  "type": "Text",
  "text": "The customer has uploaded a high-resolution video.",
  "content": [
    {
      "contentType": "Attachment",
      "attachment": {
        "id": "s3-doc-889",
        "url": "https://my-secure-bucket.s3.amazonaws.com/evidence.mp4?X-Amz-Signature=...",
        "mime": "video/mp4",
        "filename": "evidence.mp4"
      }
    }
  ]
}

The Magic:
Because you used the standard content schema in the Open Messaging payload, the Genesys Cloud Agent UI natively renders the attachment. The agent sees a standard file icon or video preview and can click it to download the file directly from your S3 bucket.

Validation, Edge Cases & Troubleshooting

Edge Case 1: Expired S3 URLs

  • The Failure Condition: The agent opens the interaction a week later (e.g., during a QA review) and clicks the attachment, but receives an HTTP 403 Forbidden error.
  • The Root Cause: Pre-signed S3 URLs have a maximum lifespan (usually 7 days).
  • The Solution: Do not send a raw S3 pre-signed URL in the Open Messaging payload. Instead, send a link to a secure “Proxy Endpoint” on your API Gateway (e.g., https://api.mycompany.com/files/s3-doc-889). When the agent clicks this link, your API verifies the agent’s authentication (via SSO) and then dynamically generates and redirects them to a fresh pre-signed S3 URL.

Edge Case 2: Unintentional Data Leaks

  • The Failure Condition: A malicious actor intercepts the URL from the Open Messaging payload and accesses the sensitive file.
  • The Root Cause: The proxy endpoint does not validate who is clicking the link.
  • The Solution: Implement OAuth Token Validation. Your proxy endpoint must require the agent’s Genesys Cloud Bearer token in the request header. The Lambda function should call the Genesys Cloud GET /api/v2/users/me API to verify the token belongs to an active, authorized agent before serving the file.

Official References