Refer to self in OpenAPI 3.0

Your definition is correct, it's just Swagger UI currently does not render circular-referenced definitions properly. See issue #3325 for details.

What you can do is add a model example, and Swagger UI will display this example instead of trying to generate an example from the definition.

    Foo:
      type: object
      properties:
        title:
          type: string
        related:
          type: array
          items: 
            $ref: '#/components/schemas/Foo'
      example:     # <-------
        title: foo
        related:
          - title: bar
          - title: baz
            related:
              - title: qux

Alternatively, you can add an example just for the related array:

    Foo:
      type: object
      properties:
        title:
          type: string
        related:
          type: array
          items: 
            $ref: '#/components/schemas/Foo'
          example:   # <--- Make sure "example" is on the same level as "type: array"
            - title: bar
            - title: baz
              related:
                - title: qux