Problem

When uploading reference images larger than ~3MB in cloud mode, the WebSocket connection fails with code 1006 (abnormal closure) after approximately 2 seconds.

Logs observed:

2026-02-25 13:14:17,593 - scope.server.cloud_connection - INFO - [CLOUD] API request: POST /api/v1/assets?filename=image.jpg
2026-02-25 13:14:19,098 - scope.server.cloud_connection - WARNING - Cloud WebSocket closed (code=1006, reason=None)

Root Cause

The upload flow was:

1. Read file → base64 encode (~33% size increase)
2. Wrap in JSON: {"_base64_content": "<4MB+ string>", ...}
3. Send entire JSON through WebSocket

For a 3MB image, this creates a ~4MB+ WebSocket message. The fal.run WebSocket infrastructure appears to have message size limits or processing timeouts that cause connection drops for large payloads.

Solution

1. Upload directly to fal CDN via REST API (token-based auth)
2. Get CDN URL (e.g., https://v3.fal.media/files/...)
3. Send only the URL through WebSocket: {"_cdn_url": "...", ...}
4. Cloud runner downloads from CDN and processes

Changes:

• cloud_proxy.py: Added _upload_to_fal_cdn() function
• fal_app.py: Handle _cdn_url payload in addition to _base64_content

Testing

1. Upload large image (>3MB) in cloud mode → should now work (uses CDN)
2. Verify thumbnails still work locally (local copy is saved regardless)