{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://dina.ai/protocol/schemas/capability-negotiation.json",
  "title": "Dina Capability Negotiation",
  "description": "Live negotiation for selecting a common protocol subset between two Dina-compatible implementations.",
  "type": "object",
  "required": [
    "schema_version",
    "negotiation_id",
    "status",
    "requested"
  ],
  "properties": {
    "schema_version": {
      "const": "1"
    },
    "negotiation_id": {
      "type": "string",
      "minLength": 1
    },
    "requester_did": {
      "$ref": "#/$defs/did"
    },
    "responder_did": {
      "$ref": "#/$defs/did"
    },
    "status": {
      "type": "string",
      "enum": ["proposed", "accepted", "rejected", "partial"]
    },
    "requested": {
      "$ref": "#/$defs/selection"
    },
    "selected": {
      "$ref": "#/$defs/selection"
    },
    "common_subset": {
      "$ref": "#/$defs/selection"
    },
    "fallback": {
      "type": "object",
      "properties": {
        "use_common_subset": {
          "type": "boolean"
        },
        "reason": {
          "type": "string"
        }
      },
      "additionalProperties": true
    },
    "reason": {
      "type": "string"
    },
    "expires_at": {
      "type": "string",
      "format": "date-time"
    },
    "extensions": {
      "$ref": "#/$defs/extensions"
    }
  },
  "additionalProperties": false,
  "$defs": {
    "did": {
      "type": "string",
      "pattern": "^did:[a-z0-9]+:.+$"
    },
    "selection": {
      "type": "object",
      "properties": {
        "protocol_version": {
          "type": "string"
        },
        "profiles": {
          "type": "array",
          "items": {
            "type": "string",
            "minLength": 1
          },
          "uniqueItems": true
        },
        "auth_method": {
          "type": "string"
        },
        "message_family": {
          "type": "string"
        },
        "request_mode": {
          "type": "string"
        },
        "response_envelope_version": {
          "type": "string"
        },
        "required_operations": {
          "type": "array",
          "items": {
            "type": "string",
            "minLength": 1
          },
          "uniqueItems": true
        },
        "required_extensions": {
          "type": "array",
          "items": {
            "type": "string",
            "minLength": 1
          },
          "uniqueItems": true
        },
        "optional_extensions": {
          "type": "array",
          "items": {
            "type": "string",
            "minLength": 1
          },
          "uniqueItems": true
        }
      },
      "additionalProperties": true
    },
    "extensions": {
      "type": "object",
      "propertyNames": {
        "pattern": "^[A-Za-z0-9._:-]+$"
      },
      "additionalProperties": true
    }
  }
}