diff --git a/.env.example b/.env.example
index 128f15b..d58eee8 100644
--- a/.env.example
+++ b/.env.example
@@ -1,5 +1,8 @@
 # L1 Server Configuration
 
+# This L1 server's public URL (sent to L2 when publishing)
+L1_PUBLIC_URL=https://l1.artdag.rose-ash.com
+
 # L2 server URL (for authentication and publishing)
 L2_SERVER=https://artdag.rose-ash.com
 
diff --git a/server.py b/server.py
index 7bb8cb0..5ccd17f 100644
--- a/server.py
+++ b/server.py
@@ -31,6 +31,7 @@ from tasks import render_effect
 # L2 server for auth verification
 L2_SERVER = os.environ.get("L2_SERVER", "http://localhost:8200")
 L2_DOMAIN = os.environ.get("L2_DOMAIN", "artdag.rose-ash.com")
+L1_PUBLIC_URL = os.environ.get("L1_PUBLIC_URL", "http://localhost:8100")
 
 # Cache directory (use /data/cache in Docker, ~/.artdag/cache locally)
 CACHE_DIR = Path(os.environ.get("CACHE_DIR", str(Path.home() / ".artdag" / "cache")))
@@ -1298,11 +1299,11 @@ async def ui_publish_run(run_id: str, request: Request, output_name: str = Form(
     if not token:
         return HTMLResponse('<div class="error">Not logged in</div>')
 
-    # Call L2 to publish the run
+    # Call L2 to publish the run, including this L1's public URL
     try:
         resp = http_requests.post(
             f"{L2_SERVER}/registry/record-run",
-            json={"run_id": run_id, "output_name": output_name},
+            json={"run_id": run_id, "output_name": output_name, "l1_server": L1_PUBLIC_URL},
             headers={"Authorization": f"Bearer {token}"},
             timeout=10
         )