Don't panic when receiving acks from disconnected clients

Backends might not discard messages immediately,
allowing to react to them.

Author: Shatur

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Don't panic when receiving acks from disconnected clients (backends might not discard messages immediately, allowing to react to them).
+
 ## [0.39.4] - 2026-04-08
 
 ### Fixed

src/server.rs

@@ -351,14 +351,13 @@ fn receive_acks(
     mut clients: Query<&mut ClientTicks>,
 ) {
     for (client, mut message) in messages.receive(ClientChannel::MutationAcks) {
+        let Ok(mut ticks) = clients.get_mut(client) else {
+            debug!("ignoring acks for disconnected client `{client}`");
+            continue;
+        };
         while message.has_remaining() {
             match postcard_utils::from_buf(&mut message) {
                 Ok(mutate_index) => {
-                    let mut ticks = clients.get_mut(client).unwrap_or_else(|_| {
-                        panic!(
-                            "messages from client `{client}` should have been removed on disconnect"
-                        )
-                    });
                     if let Some(entities) = ticks.ack_mutate_message(client, mutate_index) {
                         pools.recycle_entities(entities);
                     }