How to know which strategy was used by fastify-auth?

[fusionfoxy]

💬 Question here

I use fastify-bearer-auth with fastify-auth to authenticate requests. I have a few endpoints where the bearer auth is optional. This pretty much follows this example perfectly: https://github.com/fastify/fastify-bearer-auth?tab=readme-ov-file#integration-with-fastifyauth

However, my endpoints should respond differently to the request depending on which of the two strategies was used.

So, in my request handler, how can I know if fastify-auth authenticated the request with bearer auth or as anonymous?

  await fastify
    .register(auth)
    .register(bearerAuthPlugin, { addHook: false, keys, verifyErrorLogLevel: 'debug' })
    .decorate('allowAnonymous', function (req, reply, done) {
      if (req.headers.authorization) {
        return done(Error('not anonymous'))
      }
      return done()
    })

  fastify.route({
    method: 'GET',
    url: '/multiauth',
    preHandler: fastify.auth([
      fastify.allowAnonymous,
      fastify.verifyBearerAuth
    ]),
    handler: function (req, reply) {
      if (AUTH WAS BEARER) { // <--- How to make this check?
        reply.send({ auth: 'bearer' })
      } else {
        reply.send({ auth: 'anonymous'});
      }
    }
  })

Your Environment

• node version: 23
• fastify version: >=5.2.0
• os: Linux