diff --git a/server/maps/liveMapHotReloader.ts b/server/maps/liveMapHotReloader.ts
new file mode 100644
index 00000000..284a872d
--- /dev/null
+++ b/server/maps/liveMapHotReloader.ts
@@ -0,0 +1,28 @@
+export interface LiveMapSnapshot {
+  mapId: number;
+  version: number;
+  width: number;
+  height: number;
+  checksumSha256: string;
+  tiles: Uint16Array;
+}
+
+export class LiveMapHotReloader {
+  private readonly activeMaps = new Map<number, LiveMapSnapshot>();
+
+  getMap(mapId: number): LiveMapSnapshot | undefined {
+    return this.activeMaps.get(mapId);
+  }
+
+  publishLiveMap(next: LiveMapSnapshot): { reloaded: boolean; version: number } {
+    if (next.width <= 0 || next.height <= 0 || next.tiles.length !== next.width * next.height) {
+      throw new Error(`Invalid dimensions for map ${next.mapId}`);
+    }
+    const prev = this.activeMaps.get(next.mapId);
+    if (prev && prev.checksumSha256 === next.checksumSha256) {
+      return { reloaded: false, version: prev.version };
+    }
+    this.activeMaps.set(next.mapId, next);
+    return { reloaded: true, version: next.version };
+  }
+}