Document links

When you send a PDF (or other document) on an SMS conversation, Tether does not attach it as MMS media, because carriers strip or fail non-image MMS on long-code numbers, and delivery is inconsistent across handsets. Instead, you store the document privately and the recipient gets a plain SMS containing a short, branded link. You get the same behaviour across every SMS provider.

How it works

1. You attach a document and send it on an SMS conversation.
2. Tether stores the file in the private storage bucket and mints a hosted document link with an opaque, single-purpose token.
3. Tether sends a plain SMS whose body carries the link (for example, https://your-instance.example.com/d/{token}). You never expose the storage key. Only the token travels with the message.
4. You keep the attachment previewable inside the conversation.

Resolve a document link

GET /d/{token}

Public, unauthenticated. Tether validates the token (expiry and view count), resolves it to a short-lived, inline signed URL for the stored file, and returns a 302 redirect.

Expiry and security

• Links expire after a configurable window (DOC_LINK_TTL_SECONDS, default 3 days). The link host is set per deployment via DOC_LINK_BASE_URL.
• The recipient link points at an independent copy of the file. At expiry that copy is deleted from storage, so an expired link can never resolve to a document. The agent's in-app attachment is a separate object and stays previewable in the conversation.
• The signed URL the recipient is redirected to is short-lived and re-minted on every view.
• In production the link host must be a brand-aligned domain so messages are not filtered by carriers.