mongodb/mongoid · error · Mongoid::Errors::UnrecognizedModelAlias

Cannot find any model with type

Error message

Cannot find any model with type %{model_alias}

What it means

Raised by Mongoid::ModelResolver#model_for when the given type key (model alias, typically stored in the _type field) is not registered with any resolver. No document class corresponds to that alias, so Mongoid::Errors::UnrecognizedModelAlias is raised; the faulting input is the unrecognized model_alias string.

Solutions

1. Register the class under the alias via the model resolver registration API
2. Correct the stored alias value in the document's discriminator field
3. Ensure the model class is loaded before deserialization

When it happens

Trigger: Thrown at lib/mongoid/model_resolver.rb:150 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mongodb/mongoid@0da0e23d71 (2026-08-23). Data as JSON: /api/errors/65262a76828b839f. Report an issue: GitHub.

Appendix: source

Thrown at lib/mongoid/model_resolver.rb:150

                     else
                       Mongoid::ModelResolver.resolvers.keys.detect { |k| Mongoid::ModelResolver.resolvers[k] == self }
                     end
          resolver ||= self # if it hasn't been registered, we'll show it the best we can
          raise Mongoid::Errors::UnregisteredClass.new(klass, resolver)
        end
      end

      # Returns the document class that has been registered by the given key.
      #
      # @param [ String ] key the key by which to query the corresponding class.
      #
      # @raise Mongoid::Errors::UnrecognizedModelAlias if the given key has not
      #   been registered with this resolver.
      #
      # @return [ Class ] the document class that has been registered with the given key.
      def model_for(key)
        @key_to_model.fetch(key) do
          raise Mongoid::Errors::UnrecognizedModelAlias, key
        end
      end
    end
  end
end

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