How to handle many_to_many relationship in ash_admin

I don’t believe there is a specific example or guide for that with ash_admin. When you say that you are unable to manage the many to many relationship, what happens when you try to do so? Is it just not showing in the UI? Can you show me the action in question?

EDIT: I think the issue is simpler than I realized, after rereading your question. Answer below:

Actions do not accept related data by default. You have to add an argument (the way to accept non-attribute values into an action), and then you have to use that argument. The most straightforward way to do so, and the way that tells ash_admin to generate proper inputs, is with the builtin manage_relationship change. For example:

update :update do
  argument :users, {:array, :map}

  change manage_relationship(:users, type: :append_and_remove)
end

Thanks for the quick response and pointing out the update method

change manage_relationship(:users, type: :append_and_remove)

After adding that, the update screen looks like this:

Screenshot 2023-12-27 at 9.39.02 AM1096×1147 53.5 KB

And when I click the Load button, it shows the “search” icon. Clicking that icon adds a row having the “remove” icon.

Screenshot 2023-12-27 at 9.42.30 AM1096×1147 52.9 KB

I have created a git repo which shows this problem

https://github.com/explorer2309/AshManyMany

Thank you for the reproduction Makes my life a million times easier.

Issue fixed in 0.10.1

Great. Its working now.
Many thanks!

Hi everyone,

Sorry if this is a basic question — I might be misunderstanding how ash_admin is expected to render many_to_many inputs.

Setup:

• User many_to_many Offices through Membership
• Office has admin do label_field :name; relationship_select_max_items 10 end
• User has admin do label_field :cip end
• Membership is a join resource with defaults [:create, :read, :destroy]

On User:

• update :update has:
  argument :offices, {:array, :map}
  change manage_relationship(:offices, type: :append_and_remove)

(I also added the same to create :create)

In ash_admin (User → Create/Edit), the “Offices” field renders as a plain nested input:
Offices
Id [__________]
So it looks like it expects office IDs (UUIDs) rather than a select/typeahead using Office.label_field.

Screenshot 2025-12-30 alle 19.10.151866×1044 31.1 KB

Could you please help me understand if this is expected?

• Should ash_admin be able to render a select/typeahead for many_to_many managed via manage_relationship?
• If yes, am I using the wrong argument shape/options (e.g. should it be {:array, :uuid} and/or value_is_key: :id)?
• Or is the current “enter IDs” UI expected here, and label_field only applies to relationship selects in other contexts?

I’m on ash_admin v0.13.x.

Thanks a lot for your time!

you can use the label_field option on a resource, which will make it appear with a dropdown/typeahead in the admin interface for anything with relationships that point to it:

Hi Zach,

Thanks a lot for the hint! Sorry if I’m still missing something basic here.

I tried setting label_field on the related resource, but in AshAdmin the field still renders as an “IDs-only” nested input (no select/typeahead).

Office:

admin do
  label_field :name
  relationship_select_max_items 10
end

User:

  relationships do
    has_many :memberships, Manager.Accounts.Membership

    many_to_many :offices, Manager.Org.Office do
      through Manager.Accounts.Membership
      source_attribute_on_join_resource :user_id
      destination_attribute_on_join_resource :office_id
    end
  end


  admin do
    label_field :cip

    form do
      field :cip, type: :default
      field :name, type: :default
      field :offices, type: :default
    end
  end

actions do
    defaults [:read, :destroy]

    create :create do
      accept [:cip, :name]
      argument :offices, {:array, :map}, allow_nil?: true, default: []
      change manage_relationship(:offices, type: :append_and_remove)
    end

    update :update do
      accept [:cip, :name]
      require_atomic? false
      argument :offices, {:array, :map}, allow_nil?: true, default: []
      change manage_relationship(:offices, type: :append_and_remove)
    end

    read :get_by_subject do
      description "Get a user by the subject claim in a JWT"
      argument :subject, :string, allow_nil?: false
      get? true
      prepare AshAuthentication.Preparations.FilterBySubject
    end
  end

Is this expected currently? Or is there some AshAdmin configuration I’m missing to force a relationship selector for a many_to_many managed via manage_relationship?

hmm…maybe there is a bug? It might not work for many to many relationships? I would have expected it to though… Can you create a reproduction project and push it up?

Hi Zach! first of all, I wish you Happy new Year!!!

I made a minimal reproduction repo here: GitHub - fbutano/demo_admin · GitHub

It only includes User, Office and Membership (many_to_many through join), plus AshAdmin.

In AshAdmin, in User create/update, the offices field still renders as an “Id [uuid]” nested input instead of a relationship selector (dropdown/typeahead) even with:

Office:

admin do

label_field :name

relationship_select_max_items 10

end

Thanks a lot for your time!