Getting "Invalid recursion selector value 'model' " error after adding a custom component and trying to add the message value.

Check your custom component for the selector which you are trying to use is not getting resolved.

If u can add ur custom component code then we can help u out more 

@ankur_khare below is the code for custom component java class:

import org.apache.sling.models.annotations.*;
import org.apache.sling.models.annotations.injectorspecific.ValueMapValue;
import com.adobe.cq.export.json.ComponentExporter;
import com.adobe.cq.export.json.ExporterConstants;
import org.apache.commons.lang3.StringUtils;
import org.apache.sling.api.SlingHttpServletRequest;
import com.adobe.aem.guides.wknd.spa.angular.core.models.CustomComponent;

@Model(adaptables = SlingHttpServletRequest.class, adapters = { CustomComponent.class,
ComponentExporter.class }, resourceType = CustomComponentImpl.RESOURCE_TYPE, defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)
@Exporter(name = ExporterConstants.SLING_MODEL_EXPORTER_NAME, extensions = ExporterConstants.SLING_MODEL_EXTENSION)
public class CustomComponentImpl implements CustomComponent {

static final String RESOURCE_TYPE = "wknd-spa-angular/components/custom-component";

@ValueMapValue
private String message;

@Override
public String getMessage() {
return StringUtils.isNotBlank(message) ? message.toUpperCase() : "";
}

@Override
public String getExportedType() {
return CustomComponentImpl.RESOURCE_TYPE;
}

}

and below is my customComponent.ts file:

import { Component, Input, OnInit } from '@angular/core';

import {MapTo} from '@adobe/cq-angular-editable-components';

const CustomEditConfig = {

  emptyLabel: 'Custom Component',

  isEmpty: cqModel =>

    !cqModel || !cqModel.message || cqModel.message.trim().length < 1

};

@Component({

  selector: 'app-custom',

  templateUrl: './custom.component.html',

  styleUrls: ['./custom.component.css']

})

export class CustomComponent implements OnInit {

  @Input() message: string;

  constructor() { }

  ngOnInit(): void {

  }

}

MapTo('wknd-spa-angular/components/custom-component')(CustomComponent, CustomEditConfig);

Can you show the detailled error message? I would assume that you are using the "model" selector at the wrong location/resource type.