File and Image Handling
This section covers how your app receives files and inline images and reads their bytes, and how it sends images back.
The high-level file API is being rolled out incrementally. Today it supports receiving files attached to messages via the TypeScript, Python, and C# SDKs: in personal (1:1) chats for every agent, and soon in group chats and channels for agentic users. Receiving inline images through the same API is planned for version 2.2.0.
Files vs. attachments
In personal scope, Activity.Attachments carries every non-text part: files the user attached, inline images, Adaptive Cards, @mentions, link previews, and other content the client or the platform adds. A file is the specific subset of attachments that describes a document the user attached, one whose ContentType is file.download.info.
The context.Files accessor is the attached-file view over that raw array. It maps each attached file and inline image to a lazy handle you can download from, and skips everything else. The original Activity.Attachments array is always available when you need the raw payload or a non-file attachment.
An inline image is an image attachment with an authenticated download URL, commonly paired with an HTML attachment that describes where the image appeared in the composed message. Inline images are listed by the high-level file API alongside attached files, marked with an inline image attachment style.
Sending works similarly: an image you send is an attachment whose content type is an image MIME type, which is why it renders inline rather than arriving as a document.
In this section
- Receiving Files — read files a user attaches to a message, stream or download their bytes, and handle unsupported scopes, expired links, and agentic users.
- Receiving Inline Images — list images pasted into a message, download their bytes, and handle image formats that cannot be downloaded.
- Sending Inline Images — send an image that renders directly in the conversation, from a hosted URL or as base64-encoded bytes, within the platform's size and format limits.