How to lock slug field and customize apostrophe handling in Sanity slugs?

Great questions! Let me address both of them.

Locking/Making Fields Read-Only

Yes, you can absolutely lock a field like slug once it's generated! Sanity supports the readOnly option on fields, and it can accept either a boolean or a callback function to conditionally lock fields. For your slug use case, you could do something like this:

{
  name: 'slug',
  type: 'slug',
  options: {
    source: 'title'
  },
  readOnly: ({document}) => {
    // Lock the slug once it has been generated
    return !!document?.slug?.current
  }
}

Or if you want to lock it only after the document is published:

{
  name: 'slug',
  type: 'slug',
  options: {
    source: 'title'
  },
  readOnly: ({document}) => {
    // Lock after first publish
    return document?._id && !document._id.startsWith('drafts.')
  }
}

The readOnly callback receives parameters like document, parent, value, and currentUser, giving you full control over when the field should be locked.

Custom Slug Handling for Apostrophes

For your second question about handling apostrophes in slugs (so "VMI's RB" becomes vmis-rb instead of vmi-s-rb), you can use the slugify option on your slug field. The slug type supports custom slugification logic through this option:

{
  name: 'slug',
  type: 'slug',
  options: {
    source: 'title',
    slugify: input => input
      .toLowerCase()
      .replace(/'/g, '') // Remove apostrophes first
      .replace(/\s+/g, '-') // Replace spaces with hyphens
      .replace(/[^\w\-]+/g, '') // Remove all non-word chars except hyphens
      .replace(/\-\-+/g, '-') // Replace multiple hyphens with single hyphen
      .replace(/^-+/, '') // Trim hyphens from start
      .replace(/-+$/, '') // Trim hyphens from end
  }
}

This custom function strips out apostrophes before converting spaces to hyphens, so "VMI's RB staying for an extra year" will become vmis-rb-staying-for-an-extra-year instead of vmi-s-rb-staying-for-an-extra-year.

You can customize this function further to handle any other special characters or patterns specific to your content needs!