diff --git a/skills/sth/SKILL.md b/skills/sth/SKILL.md
index c09ff6a..fafbba2 100644
--- a/skills/sth/SKILL.md
+++ b/skills/sth/SKILL.md
@@ -20,7 +20,11 @@ This script:
 - otherwise clones or updates `sun-praise/static-html`
 - builds `dist/sth` when the Go source fingerprint changes
 
-2. Start the preview server:
+2. Start the preview server **only if not already running**:
+
+If `STATIC_HTML_SERVER_URL` is set (e.g. the server is already deployed elsewhere), skip this step entirely.
+
+Otherwise start locally:
 
 ```bash
 bash scripts/start-server.sh [port]
diff --git a/skills/sth/scripts/start-server.sh b/skills/sth/scripts/start-server.sh
index 80b11bf..d5b491a 100755
--- a/skills/sth/scripts/start-server.sh
+++ b/skills/sth/scripts/start-server.sh
@@ -2,6 +2,12 @@
 
 set -euo pipefail
 
+# If an external server is already configured, skip starting a local one.
+if [ -n "${STATIC_HTML_SERVER_URL:-}" ]; then
+  echo "STATIC_HTML_SERVER_URL is set ($STATIC_HTML_SERVER_URL) — skipping server start." >&2
+  exit 0
+fi
+
 script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 repo_dir="$("$script_dir/bootstrap-repo.sh")"
 host="${STATIC_HTML_HOST:-0.0.0.0}"