Inline object not generated

[er1c]

      "ApiError": {
        "type": "object",
        "properties": {
          "attribute": {
            "type": "string",
            "description": "The attribute that this error applies to. Omitted if this error is not in the context of a resource, or cannot be isolated to a single attribute.\n"
          },
          "type": {
            "type": "string",
            "description": "A classification for this error, which can be used to render the appropriate custom error template, or take other programmatic actions.\n"
          },
          "details": {
            "description": "Variables associated with this error that can be injected into a custom error template, or used to parameterize any other programatic actions.\n",
            "allOf": [
              {
                "type": "object",
                "additionalProperties": {
                  "type": "string"
                }
              }
            ]
          },
          "message": {
            "type": "string",
            "description": "A human-readable, English description of the error.\n"
          }
        }
      },

Resulting code:

/*
 * This file was generated by guardrail (https://github.com/guardrail-dev/guardrail).
 * Modifications will be overwritten; instead edit the OpenAPI/Swagger spec file.
 */
package com.evenfinancial.finance.v1.http4s.client.definitions
import cats.syntax.either._
import io.circe.syntax._
import cats.instances.all._
import _root_.com.evenfinancial.finance.v1.http4s.client.Implicits._
case class ApiError(attribute: Option[String] = None, `type`: Option[String] = None, details: Option[ApiError.Details] = None, message: Option[String] = None)
object ApiError {
  implicit val encodeApiError: _root_.io.circe.Encoder.AsObject[ApiError] = {
    val readOnlyKeys = _root_.scala.Predef.Set[_root_.scala.Predef.String]()
    _root_.io.circe.Encoder.AsObject.instance[ApiError](a => _root_.io.circe.JsonObject.fromIterable(_root_.scala.Vector(("attribute", a.attribute.asJson), ("type", a.`type`.asJson), ("details", a.details.asJson), ("message", a.message.asJson)))).mapJsonObject(_.filterKeys(key => !(readOnlyKeys contains key)))
  }
  implicit val decodeApiError: _root_.io.circe.Decoder[ApiError] = new _root_.io.circe.Decoder[ApiError] { final def apply(c: _root_.io.circe.HCursor): _root_.io.circe.Decoder.Result[ApiError] = for (v0 <- c.downField("attribute").as[Option[String]]; v1 <- c.downField("type").as[Option[String]]; v2 <- c.downField("details").as[Option[ApiError.Details]]; v3 <- c.downField("message").as[Option[String]]) yield ApiError(v0, v1, v2, v3) }
}

There's no ApiError.Details generated.

[er1c]

Just to confirm, this did work if not trying to inline the object:

      "ApiError": {
        "type": "object",
        "properties": {
          "attribute": {
            "type": "string",
            "description": "The attribute that this error applies to. Omitted if this error is not in the context of a resource, or cannot be isolated to a single attribute.\n"
          },
          "type": {
            "type": "string",
            "description": "A classification for this error, which can be used to render the appropriate custom error template, or take other programmatic actions.\n"
          },
          "details": {
            "description": "Variables associated with this error that can be injected into a custom error template, or used to parameterize any other programatic actions.\n",
            "allOf": [
              {
                "$ref": "#/components/schemas/ApiErrorDetails"
              }
            ]
          },
          "message": {
            "type": "string",
            "description": "A human-readable, English description of the error.\n"
          }
        }
      },
      "ApiErrorDetails": {
        "type": "object",
        "additionalProperties": {
          "type": "string"
        }
      },