From c18ce37a4213ad6a4ffe999c3d0c2f870d0237c2 Mon Sep 17 00:00:00 2001
From: WiseDev <83840010+wisedevik@users.noreply.github.com>
Date: Mon, 24 Aug 2026 20:13:16 +0300
Subject: [PATCH] gate the heartbeat off; it was resyncing the client every
 turn

the live log showed the client requesting a full sector state every
500ms - one per turn, in lockstep with the heartbeat. the heartbeat
verifies the client's predicted checksum against ours, and the sim is
not yet bit-exact, so most turns mismatch, flip the client out of sync,
and it re-downloads the whole state. that resync storm is the "86%,
70%..." loading flicker at battle start and it hard-resets the battle
scene every turn, so nothing on screen can settle.

the heartbeat now stays off unless SCROLL_HEARTBEAT=1. this returns the
client to the snapshot-only path (a hard reset every 4 ticks, but no
per-turn off-sync request). turn it back on once checksums reliably
agree.
---
 crates/game-service/src/battle_session.rs  | 8 +++++++-
 crates/game-service/tests/walk_to_tower.rs | 2 ++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/crates/game-service/src/battle_session.rs b/crates/game-service/src/battle_session.rs
index fe5381b..5271a97 100644
--- a/crates/game-service/src/battle_session.rs
+++ b/crates/game-service/src/battle_session.rs
@@ -1,6 +1,9 @@
 use std::collections::HashMap;
 use std::sync::Arc;
 pub const SNAPSHOT_INTERVAL_TICKS: i32 = 4;
+pub fn heartbeats_enabled() -> bool {
+    std::env::var("SCROLL_HEARTBEAT").map(|v| v == "1").unwrap_or(false)
+}
 pub fn snapshot_interval_ticks() -> i32 {
     std::env::var("SCROLL_SNAPSHOT_INTERVAL_TICKS")
         .ok()
@@ -265,7 +268,10 @@ impl BattleSession {
                 }
                 self.recent_checksums.push_back((self.tick, checksum));
             }
-            if self.pushes_snapshots() && self.tick % TICKS_PER_TURN == 0 {
+            if heartbeats_enabled()
+                && self.pushes_snapshots()
+                && self.tick % TICKS_PER_TURN == 0
+            {
                 if let Some(checksum) = this_checksum {
                     let turn = self.tick / TICKS_PER_TURN;
                     if let Ok(message) =
diff --git a/crates/game-service/tests/walk_to_tower.rs b/crates/game-service/tests/walk_to_tower.rs
index f4e4aca..6433a07 100644
--- a/crates/game-service/tests/walk_to_tower.rs
+++ b/crates/game-service/tests/walk_to_tower.rs
@@ -495,9 +495,11 @@ fn the_session_emits_a_heartbeat_every_turn() {
             1,
         )
         .expect("battle");
+    std::env::set_var("SCROLL_HEARTBEAT", "1");
     let mut session = game_service::battle_session::BattleSession::new(mode, Vec::new());
     session.advance_to(25);
     let out = session.take_outbound();
+    std::env::remove_var("SCROLL_HEARTBEAT");
     let heartbeats: Vec<&service_rpc::WireMessage> = out
         .iter()
         .filter(|m| m.message_type == 21902)