{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://dina.ai/protocol/schemas/d2d-envelope.json",
  "title": "Dina D2D Envelope",
  "description": "Logical Dina-to-Dina message envelope with optional transport metadata.",
  "type": "object",
  "required": [
    "schema_version",
    "message_id",
    "family",
    "from",
    "to",
    "created_at",
    "body"
  ],
  "properties": {
    "schema_version": {
      "const": "1"
    },
    "message_id": {
      "type": "string",
      "minLength": 1
    },
    "family": {
      "type": "string",
      "minLength": 1
    },
    "from": {
      "$ref": "#/$defs/did"
    },
    "to": {
      "type": "array",
      "items": {
        "$ref": "#/$defs/did"
      },
      "minItems": 1,
      "uniqueItems": true
    },
    "created_at": {
      "$ref": "#/$defs/timestamp"
    },
    "correlation_id": {
      "type": "string"
    },
    "response_mode": {
      "type": "string",
      "enum": ["inline_preferred", "async", "subscription"]
    },
    "status": {
      "type": "string",
      "enum": [
        "accepted",
        "waiting_approval",
        "waiting_input",
        "running",
        "partial",
        "completed",
        "failed",
        "cancelled",
        "expired"
      ]
    },
    "body": {
      "type": "object",
      "additionalProperties": true
    },
    "attachments": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "name": {
            "type": "string"
          },
          "media_type": {
            "type": "string"
          },
          "uri": {
            "type": "string",
            "format": "uri"
          }
        },
        "required": ["name"],
        "additionalProperties": true
      }
    },
    "transport": {
      "type": "object",
      "properties": {
        "mode": {
          "type": "string"
        },
        "ciphertext": {
          "type": "string"
        },
        "signature": {
          "type": "string"
        }
      },
      "additionalProperties": true
    },
    "extensions": {
      "$ref": "#/$defs/extensions"
    }
  },
  "additionalProperties": false,
  "$defs": {
    "did": {
      "type": "string",
      "pattern": "^did:[a-z0-9]+:.+$"
    },
    "timestamp": {
      "oneOf": [
        {
          "type": "integer",
          "minimum": 0
        },
        {
          "type": "string",
          "format": "date-time"
        }
      ]
    },
    "extensions": {
      "type": "object",
      "propertyNames": {
        "pattern": "^[A-Za-z0-9._:-]+$"
      },
      "additionalProperties": true
    }
  }
}