Auto-detect primary IP for webapp BASE_URL

socket.gethostname() returns "mcnode15" which resolves to 127.0.1.1
on the host itself and is not in every user's /etc/hosts. Replace
with a get_primary_ip() helper that asks the kernel which interface
routes outbound traffic — works on any machine without config.

Also bump webpage submodule: mcnode15 → 172.18.0.26 in static links.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: JihaoXin

ark/cli.py

@@ -3067,7 +3067,8 @@ def _check_linger():
 def _cmd_webapp_install(host: str, port: int, dev: bool = False):
     """Install and start ARK webapp as a systemd user service."""
     import subprocess as _sp
-    import socket as _socket
+
+    from ark.paths import get_primary_ip
 
     # Shared data directory for both dev and prod
     data_dir = get_ark_root() / ".ark" / "data"
@@ -3111,15 +3112,14 @@ def _cmd_webapp_install(host: str, port: int, dev: bool = False):
             prod_env_link.symlink_to(main_env)
 
     # Environment variables for systemd service
-    hostname = _socket.gethostname()
     env_vars = {
         "ARK_WEBAPP_DB_PATH": str(db_path),
         "PROJECTS_ROOT": str(data_dir / "projects"),
     }
 
     if dev:
         env_vars["ARK_SESSION_COOKIE"] = "session_dev"
-        env_vars["BASE_URL"] = f"http://{hostname}:{port}"
+        env_vars["BASE_URL"] = f"http://{get_primary_ip()}:{port}"
         # Load dev-only env overrides
         dev_env_file = get_config_dir() / "webapp-dev.env"
         if not dev_env_file.exists():

ark/paths.py

@@ -33,3 +33,21 @@ def get_config_dir() -> Path:
     d = get_ark_root() / ".ark"
     d.mkdir(exist_ok=True)
     return d
+
+
+def get_primary_ip() -> str:
+    """Return the IP of the interface that routes outbound traffic.
+
+    Uses socket.connect() on a UDP socket — no packet is sent, but the kernel
+    resolves the source IP for the route to 8.8.8.8. More reliable than
+    socket.gethostname() on hosts where the hostname resolves to 127.0.1.1.
+    """
+    import socket
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    try:
+        s.connect(("8.8.8.8", 80))
+        return s.getsockname()[0]
+    except Exception:
+        return socket.gethostname()
+    finally:
+        s.close()

ark/webapp/config.py

@@ -4,17 +4,16 @@
 
 import os
 import secrets
-import socket
 from pathlib import Path
 
-from ark.paths import get_ark_root, get_config_dir
+from ark.paths import get_ark_root, get_config_dir, get_primary_ip
 
 
 def _env_file() -> Path:
     return get_config_dir() / "webapp.env"
 
 _DEFAULTS = {
-    "BASE_URL": f"http://{socket.gethostname()}:9527",
+    "BASE_URL": f"http://{get_primary_ip()}:9527",
     "EMAIL_DOMAINS": "",
     "SMTP_HOST": "smtp.gmail.com",
     "SMTP_PORT": "587",
@@ -53,14 +52,14 @@ def _load_env_file() -> dict[str, str]:
 
 def _write_default_env():
     """Create .ark/webapp.env with placeholder values on first run."""
-    hostname = socket.gethostname()
+    ip = get_primary_ip()
     _root = get_ark_root()
     _config_dir = get_config_dir()
     content = f"""\
 # ARK Web App configuration
 # Edit this file, then restart: ark webapp
 
-BASE_URL=http://{hostname}:9527
+BASE_URL=http://{ip}:9527
 
 # SMTP — required for magic link login
 SMTP_HOST=smtp.gmail.com