diff --git a/crates/app/src/main.rs b/crates/app/src/main.rs
index c7b2dec..df844da 100644
--- a/crates/app/src/main.rs
+++ b/crates/app/src/main.rs
@@ -289,6 +289,9 @@ fn main() {
     app.add_plugins(CubePlugin);
     app.add_systems(Startup, initialize_offline_resources);
 
+    // Configure fixed timestep for deterministic game logic at 60fps
+    app.insert_resource(Time::<Fixed>::from_hz(60.0));
+
     // Insert control socket path as resource
     app.insert_resource(control::ControlSocketPath(args.control_socket.clone()));
     app.add_systems(Startup, control::start_control_socket_system);
diff --git a/crates/libmarathon/src/engine/networking.rs b/crates/libmarathon/src/engine/networking.rs
index 6e358ae..6b0c89c 100644
--- a/crates/libmarathon/src/engine/networking.rs
+++ b/crates/libmarathon/src/engine/networking.rs
@@ -185,10 +185,12 @@ impl NetworkingManager {
 
         // Spawn background task to maintain DHT presence
         let session_id_clone = session_id.clone();
+        let cancel_token_clone = cancel_token.clone();
         tokio::spawn(crate::engine::peer_discovery::maintain_dht_presence(
             session_id_clone,
             endpoint_id,
             pkarr_client,
+            cancel_token_clone,
         ));
 
         let manager = Self {
diff --git a/crates/libmarathon/src/engine/peer_discovery.rs b/crates/libmarathon/src/engine/peer_discovery.rs
index 922d89a..2d10356 100644
--- a/crates/libmarathon/src/engine/peer_discovery.rs
+++ b/crates/libmarathon/src/engine/peer_discovery.rs
@@ -138,14 +138,21 @@ pub async fn maintain_dht_presence(
     session_id: SessionId,
     our_endpoint_id: EndpointId,
     dht_client: pkarr::Client,
+    cancel_token: tokio_util::sync::CancellationToken,
 ) {
     let mut interval = tokio::time::interval(Duration::from_secs(30 * 60)); // 30 minutes
 
     loop {
-        interval.tick().await;
-
-        if let Err(e) = publish_peer_to_dht(&session_id, our_endpoint_id, &dht_client).await {
-            tracing::warn!("Failed to republish to DHT: {}", e);
+        tokio::select! {
+            _ = cancel_token.cancelled() => {
+                tracing::info!("DHT maintenance task shutting down");
+                break;
+            }
+            _ = interval.tick() => {
+                if let Err(e) = publish_peer_to_dht(&session_id, our_endpoint_id, &dht_client).await {
+                    tracing::warn!("Failed to republish to DHT: {}", e);
+                }
+            }
         }
     }
 }
diff --git a/crates/libmarathon/src/networking/plugin.rs b/crates/libmarathon/src/networking/plugin.rs
index 45e9616..7fc36fc 100644
--- a/crates/libmarathon/src/networking/plugin.rs
+++ b/crates/libmarathon/src/networking/plugin.rs
@@ -417,9 +417,9 @@ impl Plugin for NetworkingPlugin {
                 .chain(),
         );
 
-        // Update systems - handle local operations
+        // FixedUpdate systems - game logic at locked 60fps
         app.add_systems(
-            Update,
+            FixedUpdate,
             (
                 // Track Transform changes and mark NetworkedTransform as changed
                 auto_detect_transform_changes_system,
@@ -438,14 +438,14 @@ impl Plugin for NetworkingPlugin {
 
         // Trigger anti-entropy sync when going online (separate from chain to allow conditional execution)
         app.add_systems(
-            PostUpdate,
+            FixedPostUpdate,
             trigger_sync_on_connect
                 .run_if(bevy::ecs::schedule::common_conditions::resource_exists::<GossipBridge>),
         );
 
-        // PostUpdate systems - generate and send deltas
+        // FixedPostUpdate systems - generate and send deltas at locked 60fps
         app.add_systems(
-            PostUpdate,
+            FixedPostUpdate,
             (
                 // Generate deltas for changed entities, then cleanup markers
                 // CRITICAL: cleanup_skip_delta_markers_system must run immediately after