Workflow DevKit 5: 12 MiB frames, pass Sume URLs not video

Workflow Development Kit v5.0.1, released Oct 1, 2026, limits each WebSocket message: a frame over WORKFLOW_WS_MAX_MESSAGE_BYTES (default 12 MiB, at most 16 MiB) is sent as several messages and rebuilt by the receiver, per the release notes. A generated video can exceed that, so pass the Sume artifact URL between workflow steps and let the step that needs the file download it.

Why URLs instead of bytes

The release notes say oversized frames are split and rebuilt, so large values are not rejected, but every extra chunk is more transport work. A URL is a few hundred bytes. The video stays on media.sume.com and any step with network access can fetch it when needed.

What a Sume result contains

A completed Sume job returns artifacts, and the webhook payload carries the same fields. Each artifact has an id, a url on media.sume.com, a type and a content_type. Store the artifact url and the job id and treat them as the unit you pass between steps.

Webhook delivery and retries

Use the job id as your idempotency key in the receiving step. Sume's docs say the job webhook retries up to 10 attempts, so the same event can arrive more than once. Return success after durably storing the event.

Copy what you must keep

Keep the file for as long as you need it: the docs describe the artifacts as Sume-hosted URLs and state no retention period, so copy the file to your own storage when you must keep it.

• Pass artifacts[].url, not file contents
• Use job_id to dedupe repeated events
• Download in the step that needs the file
• Copy to your own storage for long retention