Rocket.Chat image preview "base64 undefined"

Description:

When using Filesystem as file storage, it fails to generate an image preview. I mounted a Backblaze bucket to /mnt/rocketfs using s3fs and then mounted that directory to /opt/rocketfs in the container. File upload and download work fine. But it can't generate a preview.

data:image/png;base64,undefined

Failed to load resource: net::ERR_INVALID_URL

These are what I'm seeing in browser console.

Steps to reproduce:

1. Mount a B2 Bucket using S3fs
2. Mount that dir to container in the compose file
3. Set Filesystem as file storage in Settings

Expected behavior:

Preview should be generated normally

Actual behavior:

Server Setup Information:

• Version of Rocket.Chat Server: 7.9.3
• License Type: Starter
• Number of Users: 2
• Operating System: Ubuntu
• Deployment Method: Docker
• Number of Running Instances: 1
• DB Replicaset Oplog:
• NodeJS Version: v22.16.0
• MongoDB Version: 8.0.12 / wiredTiger (oplog Enabled)

Client Setup Information

• Desktop App or Browser Version:
• Operating System:

Additional context

Relevant logs:

[2025-08-21T10:42:31.260Z] INFO 41779381-fa11-44d7-a4d9-508351821fd4/BROKER: ✔ ServiceBroker with 2 service(s) started successfully in 688ms.
{"level":50,"time":"2025-08-21T11:24:21.150Z","pid":1,"hostname":"69c272881f98","name":"System","err":{"type":"Error","message":"Input buffer contains unsupported image format","stack":"Error: Input buffer contains unsupported image format"},"msg":"Input buffer contains unsupported image format"}
{"level":50,"time":"2025-08-21T11:29:26.452Z","pid":1,"hostname":"69c272881f98","name":"System","err":{"type":"Error","message":"Input buffer contains unsupported image format","stack":"Error: Input buffer contains unsupported image format"},"msg":"Input buffer contains unsupported image format"}

The issue names no source file, test, or entry point. Start by tracing filesystem-backed image preview generation from the reported data:image/png;base64,undefined value and the Input buffer contains unsupported image format log. Done means previews generate normally for a filesystem mounted from an S3fs-backed B2 bucket without browser or server errors.