From e09a2c0e0f15dcbcd7f75f4b497c2dbc3d918d5a Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Fri, 25 Jul 2025 18:21:03 +0000
Subject: [PATCH] Window sync ranges below any partially completed writes.

Signed-off-by: Jason Volk <jason@zemos.net>
---
 src/api/client/sync/v3.rs | 11 +++++++----
 src/api/client/sync/v5.rs |  2 +-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/api/client/sync/v3.rs b/src/api/client/sync/v3.rs
index 58a96796..09cccfdc 100644
--- a/src/api/client/sync/v3.rs
+++ b/src/api/client/sync/v3.rs
@@ -133,7 +133,8 @@ pub(crate) async fn sync_events_route(
 	// Setup watchers, so if there's no response, we can wait for them
 	let watcher = services.sync.watch(sender_user, sender_device);
 
-	let response = build_sync_events(&services, &body).await?;
+	let next_batch = services.globals.current_count();
+	let response = build_sync_events(&services, &body, next_batch).await?;
 	if body.body.full_state
 		|| !(response.rooms.is_empty()
 			&& response.presence.is_empty()
@@ -147,20 +148,22 @@ pub(crate) async fn sync_events_route(
 	// Hang a few seconds so requests are not spammed
 	// Stop hanging if new info arrives
 	let default = Duration::from_secs(30);
-	let duration = cmp::min(body.body.timeout.unwrap_or(default), default);
+	let timeout = body.body.timeout.unwrap_or(default);
+	let duration = cmp::min(timeout, default);
 	_ = tokio::time::timeout(duration, watcher).await;
 
 	// Retry returning data
-	build_sync_events(&services, &body).await
+	let next_batch = services.globals.current_count();
+	build_sync_events(&services, &body, next_batch).await
 }
 
 pub(crate) async fn build_sync_events(
 	services: &Services,
 	body: &Ruma<sync_events::v3::Request>,
+	next_batch: u64,
 ) -> Result<sync_events::v3::Response, RumaResponse<UiaaResponse>> {
 	let (sender_user, sender_device) = body.sender();
 
-	let next_batch = services.globals.current_count();
 	let since = body
 		.body
 		.since
diff --git a/src/api/client/sync/v5.rs b/src/api/client/sync/v5.rs
index fb3a97cd..6d29e836 100644
--- a/src/api/client/sync/v5.rs
+++ b/src/api/client/sync/v5.rs
@@ -87,7 +87,7 @@ pub(crate) async fn sync_events_v5_route(
 	// Setup watchers, so if there's no response, we can wait for them
 	let watcher = services.sync.watch(sender_user, sender_device);
 
-	let next_batch = services.globals.next_count();
+	let next_batch = services.globals.current_count();
 
 	// Get sticky parameters from cache
 	let mut cached = body.body.clone();