{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "jupyter-kernel-message.json",
  "title": "Jupyter Kernel Message",
  "description": "Schema for messages in the Jupyter kernel messaging protocol (v5.4). All messages exchanged between frontends and kernels follow this envelope structure.",
  "type": "object",
  "properties": {
    "header": {
      "$ref": "#/$defs/MessageHeader"
    },
    "parent_header": {
      "description": "Header of the parent message this is a reply to. Empty object for initial requests.",
      "oneOf": [
        {"$ref": "#/$defs/MessageHeader"},
        {"type": "object", "maxProperties": 0}
      ]
    },
    "metadata": {
      "type": "object",
      "description": "Message metadata.",
      "additionalProperties": true
    },
    "content": {
      "type": "object",
      "description": "The message content. Structure varies by msg_type.",
      "additionalProperties": true
    },
    "buffers": {
      "type": "array",
      "description": "Optional binary buffers for the message.",
      "items": {
        "type": "string",
        "contentEncoding": "base64"
      }
    },
    "channel": {
      "type": "string",
      "description": "The messaging channel (used when multiplexed over WebSocket).",
      "enum": ["shell", "iopub", "stdin", "control"]
    }
  },
  "required": ["header", "parent_header", "metadata", "content"],
  "$defs": {
    "MessageHeader": {
      "type": "object",
      "description": "The header of a Jupyter kernel message.",
      "properties": {
        "msg_id": {
          "type": "string",
          "description": "Unique message identifier (typically a UUID)."
        },
        "msg_type": {
          "type": "string",
          "description": "The type of message.",
          "enum": [
            "execute_request",
            "execute_reply",
            "execute_input",
            "execute_result",
            "inspect_request",
            "inspect_reply",
            "complete_request",
            "complete_reply",
            "history_request",
            "history_reply",
            "is_complete_request",
            "is_complete_reply",
            "kernel_info_request",
            "kernel_info_reply",
            "shutdown_request",
            "shutdown_reply",
            "interrupt_request",
            "interrupt_reply",
            "debug_request",
            "debug_reply",
            "debug_event",
            "input_request",
            "input_reply",
            "stream",
            "display_data",
            "update_display_data",
            "error",
            "status",
            "clear_output",
            "comm_open",
            "comm_msg",
            "comm_close",
            "comm_info_request",
            "comm_info_reply"
          ]
        },
        "username": {
          "type": "string",
          "description": "Username associated with the message."
        },
        "session": {
          "type": "string",
          "description": "Session identifier (typically a UUID)."
        },
        "date": {
          "type": "string",
          "format": "date-time",
          "description": "ISO 8601 timestamp when the message was created."
        },
        "version": {
          "type": "string",
          "description": "Messaging protocol version.",
          "pattern": "^\\d+\\.\\d+$"
        }
      },
      "required": ["msg_id", "msg_type", "username", "session", "date", "version"]
    }
  }
}