Attachments

This page explains how attachments work, storage rules, validation and ways to include them in messages.

Ways to Add Attachments

Method	Endpoint	Use Case	Notes
Inline URL shortcut	POST /message	Quick add of a single media via imageUrl / videoUrl / gifUrl	Creates transient attachment objects (not persisted if saveOnServer=false).
JSON attachments array	POST /message	Multiple attachments or fine-grained control	Provide objects with mediaType + url OR attachmentUuid.
Uploaded file (multipart)	POST /message	Direct file upload	Returns a message with linked stored attachment.
Reuse stored file	POST /message	Reference existing attachmentUuid	Avoids re-upload / re-download.

Uploading a File (Multipart Endpoint)

When you need to attach a binary file directly you can use the multipart endpoint instead of crafting an attachments array manually.

Endpoint: POST /message Open in API Reference ↗

Example:

curl -X POST http://localhost:3001/message \
  -H "Authorization: Bearer zat_<raw-token>" \
  -F "title=Invoice" \
  -F "bucketId=<bucket-uuid>" \
  -F "deliveryType=NORMAL" \
  -F "attachment=@invoice.pdf"

Notes:

• Booleans can be passed as true/false strings (they are transformed server-side).
• You can still mix a JSON attachments array plus the uploaded file if you need multiple attachments.
• To reuse a previously uploaded file, call the JSON endpoint with attachmentUuid instead.

Attachments API Reference

Use these endpoints when you want to upload or register files ahead of time and later reference them by attachmentUuid inside a message attachments array.

Purpose	Method & Path	Ref	Notes
Upload file (multipart)	POST /api/v1/attachments/upload	API ↗	Form field: file; optional filename, mediaType (auto-detected if omitted).
Download & persist from URL	POST /api/v1/attachments/download-from-url	API ↗	Server fetches remote file; optional filename, mediaType.
Get one (metadata)	GET /api/v1/attachments/{id}	API ↗	Returns metadata (auth required).
Download (auth)	GET /api/v1/attachments/{id}/download	API ↗	Binary stream (requires auth).
Download (public)	GET /api/v1/attachments/{id}/download/public	API ↗	Only for public attachments (linked to message or bucket ICON).
List by message	GET /api/v1/attachments/message/{messageId}	API ↗	Inspect attachments after message creation.
Delete	DELETE /api/v1/attachments/{id}	API ↗	Permanently removes attachment (breaks references).

Auth: All endpoints require Authorization: Bearer <jwt-access-token> or an access token (zat_...) except the explicit public download.

Upload Example

curl -X POST http://localhost:3001/api/v1/attachments/upload \
  -H "Authorization: Bearer <jwt-access-token>" \
  -F "file=@banner.png" \
  -F "filename=banner.png" \
  -F "mediaType=IMAGE"

Response (excerpt):

{
  "id": "<attachment-uuid>",
  "filename": "banner.png",
  "mediaType": "IMAGE"
}

Download & Persist From Remote URL

curl -X POST http://localhost:3001/api/v1/attachments/download-from-url \
  -H "Authorization: Bearer <jwt-access-token>" \
  -H "Content-Type: application/json" \
  -d '{"url":"https://example.com/image.png","filename":"promo.png","mediaType":"IMAGE"}'

Reference in a Message

{
  "title": "Promo Available",
  "bucketId": "<bucket-uuid>",
  "deliveryType": "NORMAL",
  "attachments": [
    { "attachmentUuid": "<attachment-uuid>", "mediaType": "IMAGE" }
  ]
}

Notes

• If both url and attachmentUuid are provided in a single attachment object, attachmentUuid wins.
• To persist a remote file inline (without pre-upload) you can use attachments[].url + saveOnServer=true directly in the message body.
• Public download succeeds only for attachments considered public (linked to a message or bucket icon). Otherwise use the authenticated download endpoint.

Attachment Object

Either url or attachmentUuid must be provided (mutually exclusive).

Field	Type	Required	Description
mediaType	enum MediaType	Yes	One of: VIDEO, IMAGE, GIF, AUDIO, ICON (ICON also fallback for generic/docs).
name	string	No	Friendly display name (filename).
url	string	Conditional	Remote URL to fetch/display. Can't be used with attachmentUuid.
attachmentUuid	string	Conditional	Existing stored attachment ID. Can't be used with url.
saveOnServer	boolean	No	If true with url, server downloads and persists a copy (requires attachments enabled).

Validation errors occur if both or neither of url and attachmentUuid are supplied.

Storage Layout

Files are persisted under a per-user, per-media-type, per-attachment folder structure:

/attachments/<userId>/<mediaType>/<attachmentId>/<attachmentId>.<ext>

Bucket icons may automatically be injected as an ICON attachment if present and not duplicated.

File Size & Types

Defaults (overridable by env):

• Max size: ATTACHMENTS_MAX_FILE_SIZE (default 10MB)
• Allowed MIME types: ATTACHMENTS_ALLOWED_MIME_TYPES (image/jpeg, image/png, image/gif, image/webp, video/mp4, video/webm, audio/mpeg, audio/wav, audio/ogg, application/pdf, text/plain)

If the MIME type or size fails validation a 400 is returned.

Public Access

Only attachments linked to a message OR bucket icon type (ICON) are publicly accessible through any public endpoint (if exposed). Others remain private.

Automatic URL Shortcuts

Shortcuts convert single URLs into implicit attachments:

• imageUrl => IMAGE attachment
• videoUrl => VIDEO attachment
• gifUrl => GIF attachment

These are merged with explicitly provided attachments if both forms are used.

Download & Persist Remote URL

Set saveOnServer: true on a URL-based attachment to have the server fetch and store the file, replacing url with a generated attachmentUuid.

Reusing Attachments

To reuse a file in multiple messages:

1. Upload once (multipart or URL + saveOnServer)
2. Reference via attachmentUuid in subsequent message payloads

Cleanup

A background cleanup job can remove old attachments (excluding ICON) based on retention settings. Ensure you don't rely on very old unreferenced files.

Example Payload (Mixed)

{
  "title": "Release Media",
  "bucketId": "<bucket-uuid>",
  "deliveryType": "NORMAL",
  "attachments": [
    { "mediaType": "IMAGE", "url": "https://example.com/banner.png", "saveOnServer": true },
    { "mediaType": "AUDIO", "attachmentUuid": "<existing-audio-uuid>", "name": "Theme" }
  ],
  "videoUrl": "https://cdn.example.com/teaser.mp4"
}

Troubleshooting

Symptom	Likely Cause	Fix
400 both url & attachmentUuid	Provided both fields	Remove one of them
400 invalid mediaType	Typo or unsupported value	Use an enum value exactly as listed
400 file size exceeds	File > max size	Increase env limit or compress file
Attachment not visible	Not linked to message and not ICON	Ensure message linkage or mediaType ICON
Download timeout	Remote host slow/unreachable	Host file on faster CDN or retry

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