{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://sigelo.invalid/schema/v0/challenge.json",
  "title": "sigelo/0 challenge",
  "description": "The §5.2 proof-of-control challenge: exactly these five fields; an agent library MUST refuse any other key. The world chooses nonce and ctx (opaque to the agent). Never in a bundle; signed with a detached sig like any body.",
  "type": "object",
  "required": ["v", "typ", "did", "ctx", "nonce"],
  "additionalProperties": false,
  "properties": {
    "v": { "$ref": "common.json#/$defs/version" },
    "typ": { "const": "challenge" },
    "did": { "$ref": "common.json#/$defs/did" },
    "ctx": { "$ref": "common.json#/$defs/string" },
    "nonce": { "$ref": "common.json#/$defs/string" }
  }
}