sspiPackagesUsed: ['Negotiate'] is prompting user to login?

[thegoatherder]

The following NodeSSPI options successfully auth a user (without prompting for credentials) accessing https://myhost:9990/ over XHR request (node v14.15.1):

options = {
  // sspi cache = 1 hour
  cacheTTL: process.env.AUTH_CACHE_TTL || 60000 * 60,
  // sspi initialisation settings
  retrieveGroups: true,
  authoritative: true,
  offerBasic: false,
  sspiPackagesUsed: ['NTLM']
};

We have been instructed by IT that NTLM is not allowed and we must use Negotiate authentication. This appears to be supported by NodeSSPI but I can’t get it to work properly.

When I try to update above config with:

sspiPackagesUsed: ['Negotiate', 'NTLM']

or

sspiPackagesUsed: ['Negotiate']

the browser accessing the service over XHR now prompts the user to enter their username and password for the request (tested in Chrome, Edge, IE11)

How can I use Negotiate authentication without prompting the user? Is Negotiate the correct value?

The site is already in the Intranet Security Zone. When I use Negotiate setting on an IIS .net site on the same domain/server, it successfully authenticates without prompting the user for credentials.

[thegoatherder]

Any update on this please?