Files and multimodal input

Managed Channels can hydrate provider attachments into message.contentParts. The SDK carries text, images, audio, video, and PDF documents in one provider-neutral prompt shape.

Pass attachments to the agent#

Managed conversation history does not contain the current inbound turn. runAgent() automatically chooses the inbound text or attachment parts when prompt is omitted. Build a combined prompt when the same turn can contain both message.text and message.contentParts:

channel.onMessage(async ({ thread, message }) => {
  const prompt = message.contentParts?.length
    ? [
        ...(message.text
          ? [{ type: "text" as const, text: message.text }]
          : []),
        ...message.contentParts,
      ]
    : message.text;

  await thread.runAgent({ prompt });
});

If you pass only message.text, the model will not receive hydrated binary attachments. If contentParts exists, do not append it to managed history yourself; runAgent adds the explicit prompt for this turn.

Understand the content mapping#

The binary value is base64. Whether the agent actually understands a media part depends on its selected model and framework. Choose a multimodal model and test the exact media types you accept.

File retrieval is best-effort. A provider-ingest failure can omit the attachment before the SDK receives a file handle. If Intelligence delivers a handle but the SDK cannot hydrate it, the SDK inserts a short failure note instead of failing the whole turn.

Slack file access#

Teams file access#

Teams exposes files differently by surface:

• Personal 1:1 chat uploads can arrive as downloadable file.download.info attachments.
• Inline media such as images, audio, video, and PDFs with a Bot Connector contentUrl can hydrate in chats or channels through the connector token. This path does not require Graph consent.
• In team channels, SharePoint-reference uploads and inline pasted images use Microsoft Graph. Intelligence reads the channel message, then resolves its reference files or hosted content.
• Other group-chat file-upload shapes remain unsupported. Test every attachment shape your workflow accepts.

The generated Teams package already declares the supported personal and team bot scopes, sets supportsFiles: true, and requests ChannelMessage.Read.Group resource-specific consent. Upload that generated package as-is. Do not add groupChat; managed group chats are not supported. A team owner grants the resource-specific permission during installation.

For Graph-backed team-channel messages:

• The app manifest's ChannelMessage.Read.Group resource-specific consent lets Intelligence read the channel message and inline hosted content. A team owner grants it during installation; it does not need tenant-admin Graph consent. Microsoft documents it as a resource-specific consent permission.
• Add the broad Files.ReadWrite.All application permission to the Entra app for SharePoint-reference file ingest and managed outbound file support. It requires tenant-admin consent. Teams setup probes this permission and does not report the connection ready when the required Graph access is missing.

Without the required consent, the text turn still runs but affected files are omitted or represented by a retrieval-failure note. Test personal chat, standard/private team channels, inline media, pasted images, and SharePoint-reference uploads separately.

Post a file#

thread.postFile() takes bytes and returns a result instead of throwing for an unsupported provider capability:

const csv = new TextEncoder().encode(
  ["id,status", "INC-421,investigating"].join("\n"),
);

const result = await thread.postFile({
  bytes: csv,
  filename: "incident-report.csv",
  title: "Incident report",
  altText: "CSV export of the incident report",
});

if (!result.ok) {
  await thread.post(`The report could not be attached: ${result.error}`);
}

On managed Channels, result.ok means Intelligence stored the managed asset, the provider acknowledged the file or image effect, and the SDK recorded the asset in canonical Thread history.

Managed Teams supports general outbound files. In standard and private Team channels, Intelligence uploads the original bytes to the channel's SharePoint files area and sends a visible card or link. In personal chat, the same postFile() call starts Microsoft's native consent-card flow when required; acceptance completes the trusted upload and a decline remains a normal user choice. Images may use the inline Bot Connector path. Always check result.ok and send a text fallback when delivery is rejected.

Treat attachments as untrusted input#

• Validate declared MIME type and file signature before application-side processing.
• Put limits on decompression, parsing, page count, and extracted text.
• Do not execute macros or uploaded code.
• Resolve the provider user to an authenticated application identity before a file can trigger a consequential write.
• Avoid logging base64 content, signed download URLs, or document text.

See the IncomingMessage reference and AgentContentPart reference for the exact public shapes.