diff --git a/src/api/server/send_join.rs b/src/api/server/send_join.rs
index 609f93df..62d37e7e 100644
--- a/src/api/server/send_join.rs
+++ b/src/api/server/send_join.rs
@@ -208,6 +208,7 @@ async fn create_join_event(
 		.handle_incoming_pdu(&origin, room_id, &event_id, value.clone(), true)
 		.boxed()
 		.await?
+		.map(at!(0))
 		.ok_or_else(|| err!(Request(InvalidParam("Could not accept as timeline event."))))?;
 
 	drop(mutex_lock);
diff --git a/src/api/server/send_knock.rs b/src/api/server/send_knock.rs
index 1938e8e3..bc9b7158 100644
--- a/src/api/server/send_knock.rs
+++ b/src/api/server/send_knock.rs
@@ -11,7 +11,7 @@ use ruma::{
 	serde::JsonObject,
 };
 use tuwunel_core::{
-	Err, Result, err,
+	Err, Result, at, err,
 	matrix::{event::gen_event_id_canonical_json, pdu::PduEvent},
 	warn,
 };
@@ -170,6 +170,7 @@ pub(crate) async fn create_knock_event_v1_route(
 		.handle_incoming_pdu(&origin, &body.room_id, &event_id, value.clone(), true)
 		.boxed()
 		.await?
+		.map(at!(0))
 		.ok_or_else(|| err!(Request(InvalidParam("Could not accept as timeline event."))))?;
 
 	drop(mutex_lock);
diff --git a/src/api/server/send_leave.rs b/src/api/server/send_leave.rs
index e0a0de1b..ca0dbc67 100644
--- a/src/api/server/send_leave.rs
+++ b/src/api/server/send_leave.rs
@@ -11,7 +11,7 @@ use ruma::{
 	},
 };
 use serde_json::value::RawValue as RawJsonValue;
-use tuwunel_core::{Err, Result, err, matrix::event::gen_event_id_canonical_json};
+use tuwunel_core::{Err, Result, at, err, matrix::event::gen_event_id_canonical_json};
 use tuwunel_service::Services;
 
 use crate::Ruma;
@@ -151,6 +151,7 @@ async fn create_leave_event(
 		.handle_incoming_pdu(origin, room_id, &event_id, value, true)
 		.boxed()
 		.await?
+		.map(at!(0))
 		.ok_or_else(|| err!(Request(InvalidParam("Could not accept as timeline event."))))?;
 
 	drop(mutex_lock);
diff --git a/src/service/membership/invite.rs b/src/service/membership/invite.rs
index cade9b16..a33c2d23 100644
--- a/src/service/membership/invite.rs
+++ b/src/service/membership/invite.rs
@@ -5,7 +5,7 @@ use ruma::{
 	events::room::member::{MembershipState, RoomMemberEventContent},
 };
 use tuwunel_core::{
-	Err, Result, err, implement, matrix::event::gen_event_id_canonical_json, pdu::PduBuilder,
+	Err, Result, at, err, implement, matrix::event::gen_event_id_canonical_json, pdu::PduBuilder,
 };
 
 use super::Service;
@@ -135,6 +135,7 @@ async fn remote_invite(
 		.event_handler
 		.handle_incoming_pdu(&origin, room_id, &event_id, value, true)
 		.await?
+		.map(at!(0))
 		.ok_or_else(|| {
 			err!(Request(InvalidParam("Could not accept incoming PDU as timeline event.")))
 		})?;
diff --git a/src/service/rooms/event_handler/handle_incoming_pdu.rs b/src/service/rooms/event_handler/handle_incoming_pdu.rs
index ab47f5b7..e249918a 100644
--- a/src/service/rooms/event_handler/handle_incoming_pdu.rs
+++ b/src/service/rooms/event_handler/handle_incoming_pdu.rs
@@ -57,11 +57,11 @@ pub async fn handle_incoming_pdu<'a>(
 	event_id: &'a EventId,
 	pdu: CanonicalJsonObject,
 	is_timeline_event: bool,
-) -> Result<Option<RawPduId>> {
+) -> Result<Option<(RawPduId, bool)>> {
 	// 1. Skip the PDU if we already have it as a timeline event
 	if let Ok(pdu_id) = self.services.timeline.get_pdu_id(event_id).await {
 		trace!(?event_id, "exists");
-		return Ok(Some(pdu_id));
+		return Ok(Some((pdu_id, false)));
 	}
 
 	// 1.1 Check the server is in the room
diff --git a/src/service/rooms/event_handler/upgrade_outlier_pdu.rs b/src/service/rooms/event_handler/upgrade_outlier_pdu.rs
index 2c85b7b5..eedd1eb6 100644
--- a/src/service/rooms/event_handler/upgrade_outlier_pdu.rs
+++ b/src/service/rooms/event_handler/upgrade_outlier_pdu.rs
@@ -28,7 +28,7 @@ pub(super) async fn upgrade_outlier_to_timeline_pdu(
 	val: CanonicalJsonObject,
 	room_version: &RoomVersionId,
 	create_event_id: &EventId,
-) -> Result<Option<RawPduId>> {
+) -> Result<Option<(RawPduId, bool)>> {
 	// Skip the PDU if we already have it as a timeline event
 	if let Ok(pduid) = self
 		.services
@@ -36,7 +36,7 @@ pub(super) async fn upgrade_outlier_to_timeline_pdu(
 		.get_pdu_id(incoming_pdu.event_id())
 		.await
 	{
-		return Ok(Some(pduid));
+		return Ok(Some((pduid, false)));
 	}
 
 	if self
@@ -270,5 +270,5 @@ pub(super) async fn upgrade_outlier_to_timeline_pdu(
 		"Accepted",
 	);
 
-	Ok(pdu_id)
+	Ok(pdu_id.zip(Some(true)))
 }
diff --git a/src/service/rooms/timeline/append.rs b/src/service/rooms/timeline/append.rs
index da310600..2328533e 100644
--- a/src/service/rooms/timeline/append.rs
+++ b/src/service/rooms/timeline/append.rs
@@ -33,7 +33,7 @@ use crate::rooms::{short::ShortRoomId, state_compressor::CompressedState};
 	skip_all,
 	ret(Debug)
 )]
-pub async fn append_incoming_pdu<'a, Leafs>(
+pub(crate) async fn append_incoming_pdu<'a, Leafs>(
 	&'a self,
 	pdu: &'a PduEvent,
 	pdu_json: CanonicalJsonObject,