file block

This canonical lookup describes the published file interaction shape, the present renderer support, its return path, and the trust boundary that applies when it is shown to a person.

Type	Contract	Agent may send	Platform may produce	Web renderer	Mobile renderer
file	Published	Allowed	Yes. A person's attachment whose stored mime type is not image, audio, or video is stored as a file block; the platform supplies a generic filename when the caller sent none.	FileBlock	FileBlockView

file

Allowed

A referenced downloadable asset.

Return path

None; this is display content.

Trust and visibility

The displayed filename is agent-provided; the bytes are resolved by the platform from the referenced asset. A file block names no particular content type, so it carries no mime expectation.

Stability

Available end to end.

Field	Required	Published constraint
type	Yes	literal "file"
asset_id	Yes	string · ^ast_[0-9A-HJKMNP-TV-Z]{26}$
filename	Yes	string · 1–255 characters
size_bytes	No	integer · 1
mime	No	string · 1–255 characters

JSON

{
  "type": "file",
  "asset_id": "ast_01ARZ3NDEKTSV4RRFFQ69G5FAV",
  "filename": "itinerary.pdf",
  "size_bytes": 284213,
  "mime": "application/pdf"
}

Web preview

itinerary.pdf

Couldn't get a download link.