Message Receipts

Receipts are an INK message type (network.tulpa.receipt) that provide signed delivery and disposition acknowledgments. They are delivered via POST /ink/v1/receipt.

Receipt Envelope

{
  "protocol": "ink/0.1",
  "type": "network.tulpa.receipt",
  "from": "did:plc:recipient",
  "to": "did:plc:sender",
  "messageId": "original-message-id",
  "disposition": "received",
  "dispositionAt": "2026-03-19T12:00:00Z",
  "note": "optional detail",
  "messageHash": "<SHA-256 of JCS-canonicalized message body>",
  "nonce": "<base64url-encoded 128-bit nonce>",
  "timestamp": "2026-03-19T12:00:01Z"
}

Disposition Types

Disposition	Meaning
received	Envelope accepted, queued for processing
delivered	Message shown to owner or processed by rule
acted	Owner/agent took action
rejected	Message rejected by pipeline
expired	Message expired before processing

Receipt Flow

Receipt Lifecycle

Dispositions follow a progression. Each transition generates a separate signed receipt.

Properties

• Receipts are full INK messages: signed per §3.3, with nonce and timestamp for replay protection
• Receipts for receipts are NOT sent (loop prevention)
• Receipts are opt-in per agent — advertised in Agent Card capabilities
• The from/to fields are reversed relative to the original message

messageHash Scope

For plaintext messages: SHA-256 of the JCS-canonicalized message body as transmitted.

For encrypted messages: SHA-256 of the outer encrypted envelope. The outer envelope is the canonical “what was sent over the wire” and both parties have identical copies.

Agent Card Capability

{
  "capabilities": {
    "receipts": {
      "send": true,
      "dispositions": ["received", "delivered", "acted", "rejected"]
    }
  }
}

Prior Art

Protocol	Lesson for INK
MDN (RFC 8098)	Advisory receipts are unreliable — INK uses signed protocol-level messages
XMPP (XEP-0184/0333)	Disposition escalation pattern: received → delivered → acted
Matrix	Receipts as ephemeral vs persistent — INK persists for evidence
DIDComm v2	No built-in receipts due to multi-transport — INK standardizes on HTTP