diff --git a/src/admin/user/commands.rs b/src/admin/user/commands.rs
index 9b4eea69..9d503605 100644
--- a/src/admin/user/commands.rs
+++ b/src/admin/user/commands.rs
@@ -17,7 +17,7 @@ use tuwunel_core::{
 	matrix::{Event, pdu::PduBuilder},
 	utils::{self, ReadyExt},
 };
-use tuwunel_service::Services;
+use tuwunel_service::{Services, users::Register};
 
 use crate::{
 	admin_command, get_room_info,
@@ -63,7 +63,12 @@ pub(super) async fn create_user(&self, username: String, password: Option<String
 
 	self.services
 		.users
-		.full_register(&user_id, Some(&password), None, None, false, true)
+		.full_register(Register {
+			user_id: Some(&user_id),
+			password: Some(&password),
+			grant_first_user_admin: true,
+			..Default::default()
+		})
 		.await?;
 
 	self.write_str(&format!("Created user with user_id: {user_id} and password: `{password}`"))
diff --git a/src/api/client/register.rs b/src/api/client/register.rs
index 85701639..2b7e5fe8 100644
--- a/src/api/client/register.rs
+++ b/src/api/client/register.rs
@@ -2,19 +2,18 @@ use std::fmt::Write;
 
 use axum::extract::State;
 use axum_client_ip::InsecureClientIp;
-use register::RegistrationKind;
 use ruma::{
 	UserId,
 	api::client::{
 		account::{
 			check_registration_token_validity, get_username_availability,
-			register::{self, LoginType},
+			register::{self, LoginType, RegistrationKind},
 		},
 		uiaa::{AuthFlow, AuthType, UiaaInfo},
 	},
 };
 use tuwunel_core::{Err, Error, Result, debug_info, debug_warn, info, utils};
-use tuwunel_service::users::device::generate_refresh_token;
+use tuwunel_service::users::{Register, device::generate_refresh_token};
 
 use super::SESSION_ID_LENGTH;
 use crate::Ruma;
@@ -337,7 +336,14 @@ pub(crate) async fn register_route(
 
 	services
 		.users
-		.full_register(&user_id, password, None, body.appservice_info.as_ref(), is_guest, true)
+		.full_register(Register {
+			user_id: Some(&user_id),
+			password,
+			appservice_info: body.appservice_info.as_ref(),
+			is_guest,
+			grant_first_user_admin: true,
+			..Default::default()
+		})
 		.await?;
 
 	if (!is_guest && body.inhibit_login)
diff --git a/src/api/client/session/ldap.rs b/src/api/client/session/ldap.rs
index 5eabfaf3..68953ec1 100644
--- a/src/api/client/session/ldap.rs
+++ b/src/api/client/session/ldap.rs
@@ -1,7 +1,7 @@
 use futures::FutureExt;
 use ruma::{OwnedUserId, UserId};
 use tuwunel_core::{Err, Result, debug};
-use tuwunel_service::Services;
+use tuwunel_service::{Services, users::Register};
 
 use super::password_login;
 
@@ -51,7 +51,12 @@ pub(super) async fn ldap_login(
 	if !services.users.exists(lowercased_user_id).await {
 		services
 			.users
-			.full_register(lowercased_user_id, Some("*"), Some("ldap"), None, false, false)
+			.full_register(Register {
+				user_id: Some(lowercased_user_id),
+				password: Some("*"),
+				origin: Some("ldap"),
+				..Default::default()
+			})
 			.await?;
 	}
 
diff --git a/src/service/users/mod.rs b/src/service/users/mod.rs
index 53ce4dc0..981c02f9 100644
--- a/src/service/users/mod.rs
+++ b/src/service/users/mod.rs
@@ -22,7 +22,7 @@ use tuwunel_core::{
 };
 use tuwunel_database::{Deserialized, Json, Map};
 
-pub use self::keys::parse_master_key;
+pub use self::{keys::parse_master_key, register::Register};
 
 pub struct Service {
 	services: Arc<crate::services::OnceServices>,
diff --git a/src/service/users/register.rs b/src/service/users/register.rs
index c8ce6e5f..5ba76cd0 100644
--- a/src/service/users/register.rs
+++ b/src/service/users/register.rs
@@ -6,19 +6,45 @@ use tuwunel_core::{Err, Result, error, implement, info, is_equal_to, warn};
 
 use crate::appservice::RegistrationInfo;
 
+#[derive(Debug, Default)]
+pub struct Register<'a> {
+	pub user_id: Option<&'a UserId>,
+	pub username: Option<&'a str>,
+	pub password: Option<&'a str>,
+	pub origin: Option<&'a str>,
+	pub appservice_info: Option<&'a RegistrationInfo>,
+	pub is_guest: bool,
+	pub grant_first_user_admin: bool,
+}
+
 /// Fully register a local user
 ///
 /// Returns a device id and access token for the registered user
 #[implement(super::Service)]
+#[tracing::instrument(level = "info", skip(self))]
 pub async fn full_register(
 	&self,
-	user_id: &UserId,
-	password: Option<&str>,
-	origin: Option<&str>,
-	appservice_info: Option<&RegistrationInfo>,
-	is_guest: bool,
-	grant_admin: bool,
+	Register {
+		username,
+		user_id,
+		password,
+		origin,
+		appservice_info,
+		is_guest,
+		grant_first_user_admin,
+	}: Register<'_>,
 ) -> Result {
+	let ref user_id = user_id
+		.map(ToOwned::to_owned)
+		.map(Ok)
+		.or_else(|| {
+			username.map(|username| {
+				UserId::parse_with_server_name(username, self.services.globals.server_name())
+			})
+		})
+		.transpose()?
+		.expect("Caller failed to supply either user_id or username parameter");
+
 	if !self.services.globals.user_is_local(user_id) {
 		return Err!("Cannot register remote user");
 	}
@@ -80,7 +106,7 @@ pub async fn full_register(
 	// users
 	// Note: the server user is generated first
 	if !is_guest
-		&& grant_admin
+		&& grant_first_user_admin
 		&& self.services.config.grant_admin_to_first_user
 		&& let Ok(admin_room) = self.services.admin.get_admin_room().await
 		&& self