{
  "openapi": "3.0.0",
  "info": {
    "title": "API definition with circular $refs in request bodies",
    "version": "1.0.0"
  },
  "servers": [{ "url": "https://httpbin.org" }],
  "paths": {
    "/direct": {
      "post": {
        "operationId": "directCircular",
        "summary": "Direct self-reference (TreeNode.parent → TreeNode)",
        "requestBody": {
          "content": {
            "application/json": {
              "schema": { "$ref": "#/components/schemas/TreeNode" }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Success",
            "content": {
              "application/json": {
                "schema": { "$ref": "#/components/schemas/TreeNode" }
              }
            }
          }
        }
      }
    },
    "/indirect": {
      "post": {
        "operationId": "indirectCircular",
        "summary": "Two-hop chain (Person → Company → Person)",
        "requestBody": {
          "content": {
            "application/json": {
              "schema": { "$ref": "#/components/schemas/Person" }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Success",
            "content": {
              "application/json": {
                "schema": { "$ref": "#/components/schemas/Person" }
              }
            }
          }
        }
      }
    },
    "/polymorphic": {
      "post": {
        "operationId": "polymorphicCircular",
        "summary": "Circular in oneOf option",
        "requestBody": {
          "content": {
            "application/json": {
              "schema": { "$ref": "#/components/schemas/Expression" }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Success",
            "content": {
              "application/json": {
                "schema": { "$ref": "#/components/schemas/Expression" }
              }
            }
          }
        }
      }
    },
    "/multiple": {
      "post": {
        "operationId": "multipleCircular",
        "summary": "Multiple self-referencing properties",
        "requestBody": {
          "content": {
            "application/json": {
              "schema": { "$ref": "#/components/schemas/LinkedNode" }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Success",
            "content": {
              "application/json": {
                "schema": { "$ref": "#/components/schemas/LinkedNode" }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "TreeNode": {
        "type": "object",
        "title": "TreeNode",
        "required": ["id", "name", "parent"],
        "properties": {
          "id": { "type": "string" },
          "name": { "type": "string" },
          "parent": { "$ref": "#/components/schemas/TreeNode" },
          "children": {
            "type": "array",
            "items": { "$ref": "#/components/schemas/TreeNode" }
          }
        }
      },
      "Person": {
        "type": "object",
        "title": "Person",
        "required": ["name"],
        "properties": {
          "name": { "type": "string" },
          "employer": { "$ref": "#/components/schemas/Company" }
        }
      },
      "Company": {
        "type": "object",
        "title": "Company",
        "required": ["name"],
        "properties": {
          "name": { "type": "string" },
          "ceo": { "$ref": "#/components/schemas/Person" }
        }
      },
      "Expression": {
        "type": "object",
        "title": "Expression",
        "properties": {
          "type": { "type": "string", "enum": ["literal", "binary"] },
          "value": {
            "oneOf": [{ "type": "string", "title": "LiteralValue" }, { "$ref": "#/components/schemas/Expression" }]
          }
        }
      },
      "LinkedNode": {
        "type": "object",
        "title": "LinkedNode",
        "required": ["id"],
        "properties": {
          "id": { "type": "string" },
          "prev": { "$ref": "#/components/schemas/LinkedNode" },
          "next": { "$ref": "#/components/schemas/LinkedNode" }
        }
      }
    }
  }
}