Is it possible to combine a csv feeder with a foreach to create a List of case classes and store them in Session?

Wrong word indeed, replacing with “In particular”.

That seems backward to me for some reason. I must be missing how you create a parameterized http request based on data from a csv for example if the http request happens first.

No.

exec(
http("auth")
          .post(authUrl)
          .formParamMap(Map(
            "client_id" -> "#{client.clientId}",
            "client_secret" -> "#{client.clientSecret}",
            "grant_type" -> "client_credentials"
          ))
          .check(jsonPath("$.access_token").saveAs("accessToken"))
)
.exec { session =>
 // fetch session data, including accessToken that you only have now
// build a Client
// add it to your buffer
 session
}