Boolean field initialValue set to true displays toggle in middle position

No worries, this is a common confusion when starting with Sanity! The "toggle in the middle" state you're seeing is actually the undefined state for a boolean field. This happens because initialValue only applies when a document is first created from a template, but if you're viewing an existing document or the field hasn't been set yet, it shows as undefined (middle position).

Here are a few solutions:

1. Field-level initialValue (simplest for new documents)

In your schema definition, you can set the initialValue directly on the field:

defineField({
  name: 'approved',
  type: 'boolean',
  initialValue: true
})

This will set the value to true when new documents are created, but won't affect existing documents that already have an undefined value[^1].

2. Handle undefined in your application

In your queries or application code, you can treat undefined as false (or true, depending on your needs):

const isApproved = document.approved ?? true // defaults to true if undefined

3. Update existing documents

If you have existing documents with undefined boolean values, you'll need to update them. You can do this through the Studio UI by toggling each field, or use a migration script to bulk update documents.

4. Make the field required

If you want to force a value to be set:

defineField({
  name: 'approved',
  type: 'boolean',
  initialValue: true,
  validation: Rule => Rule.required()
})

The key thing to remember is that boolean fields in Sanity have three states: true, false, and undefined (the middle toggle position). The initialValue property only applies to newly created documents, not existing ones.

Hope this helps! Let me know if you need clarification on any of these approaches 🙂