Files

Sending a file takes two steps: upload it, then post a message that attaches it. Reading one is a single download call. Both work with personal tokens and app tokens.

Upload a file

Send multipart/form-data with one part named file. Missived keeps the part's file name and content type.

curl -X POST https://api.missived.com/v1/orgs/<orgId>/files \
  -H "Authorization: Bearer $MISSIVED_TOKEN" \
  -F "[email protected];type=text/plain"

The answer is 201 with the stored file:

{
  "id": "…",
  "file_name": "build.log",
  "content_type": "text/plain",
  "size": 18234,
  "created_at": "2026-10-18T09:12:00.000Z",
  "download_url": "https://api.missived.com/v1/attachments/…/content"
}

The file is now pending: stored, but not in any channel yet.

• Size: at most 25 MB per file through the API (bigger files can still be sent from the app). Larger uploads answer 413 payload_too_large.
• Types: the same file types the app's composer accepts: common images, video, audio, PDF, plain text, Markdown, CSV, Word, Excel and PowerPoint documents, and zip, tar and gzip archives. Anything else answers 415 unsupported_media_type, as does a body that isn't multipart. An empty file answers 400 invalid_request.
• Storage: the file counts against the org's storage. When it's full, the upload answers 413 storage_full.
• At rest: files are stored encrypted.

Attach it to a message

Post a message with the upload's id in attachment_ids:

curl -X POST https://api.missived.com/v1/channels/<channelId>/messages \
  -H "Authorization: Bearer $MISSIVED_TOKEN" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: build-1234-log" \
  -d '{"content": "Build 1234 log", "attachment_ids": ["<fileId>"]}'

• Up to 10 files per message.
• Only files you uploaded (or, for an app token, that the app's bot uploaded), to the same org, that aren't attached to a message yet. Anything else answers 400 invalid_request.
• content is optional when the message has files.
• Once attached, a file belongs to that message and channel; it can't be attached again.

Download an attachment

Messages list their files in attachments. Each one has:

Fetch the bytes with your token:

curl -L -o build.log \
  -H "Authorization: Bearer $MISSIVED_TOKEN" \
  https://api.missived.com/v1/attachments/<attachmentId>/content

The answer is the file, decrypted, with Content-Disposition: attachment and the file's name.

Who may download it:

• An attached file: anyone whose token may read that channel's messages. For an app, that means a channel it was added to (or any channel it can see, with messages:read:all), and never a direct message or group chat.
• A pending upload: only its uploader.
• Anything else, including files in other orgs, answers 404 not_found.

With the TypeScript SDK

The @missived/bot SDK has helpers for both steps:

import { RestClient } from '@missived/bot';

const rest = new RestClient({ token: process.env.MISSIVED_TOKEN! });

// Upload, then attach.
const file = await rest.uploadFile('<orgId>', { name: 'build.log', type: 'text/plain', data: logBytes });
await rest.createMessage('<channelId>', { content: 'Build log', attachment_ids: [file.id] });

// Download a message's first attachment.
const { data, fileName, contentType } = await rest.downloadAttachment(message.attachments[0].id);

data accepts a Blob, an ArrayBuffer or a Uint8Array. downloadAttachment returns the bytes as a Uint8Array, with the content type and the file name from the response.