Activepieces multipart Content-Length: what body Sume wants

For Sume, do not pick multipart form-data in an Activepieces HTTP step. Job submits must be application/json; a request in any other content type fails with 415 unsupported_media_type. Pass media as a public HTTPS URL inside the JSON body.

Activepieces 0.91.0 (2026-09-14) lists "send known-length multipart bodies with Content-Length instead of chunked (#15367)". That changes how multipart is framed, not whether Sume accepts it. Sume side: Errors and credits, read 2026-10-01.

What happens if I send multipart to a Sume submit?

The documented error is 415 with code unsupported_media_type: "The request body was not application/json", and details.received_content_type shows what arrived. A fixed Content-Length does not change that.

How do I get a local file to Sume?

The API reference says to prefer public HTTPS media URLs in generation requests. The /v1/assets upload endpoints are implemented but hidden from the public OpenAPI document, so treat them as undocumented contract. In hosted MCP, the flow is create an upload URL, have the client PUT the bytes, then call assets_complete; hosted MCP cannot read files from your machine.

Which Activepieces body mode fits each call?

Should I host the file first?

If the file is not already at a public HTTPS URL, put it on storage you control and pass that URL. Treat signed upload and download URLs as temporary secrets, per Sume's safety rules, and keep them out of flow logs. For image upload size limits on another vendor and the URL approach, see Ideogram multipart upload limits vs Sume public HTTPS image URLs.