diff --git a/scripts/load-stack-stop.sh b/scripts/load-stack-stop.sh
index d66ae8f..8088803 100755
--- a/scripts/load-stack-stop.sh
+++ b/scripts/load-stack-stop.sh
@@ -4,6 +4,7 @@ set -eu
 ROOT=$(CDPATH='' cd -- "$(dirname -- "$0")/.." && pwd)
 ENV_FILE=${WNH_LOAD_ENV_FILE:-"$ROOT/output/runtime/load.env"}
 LOAD_TOOLS_IMAGE=${WNH_LOAD_TOOLS_IMAGE:-who-need-help:load-tools}
+RUNTIME_OWNER_IMAGE=python:3.14.6-alpine3.23@sha256:b165067c5afc37fa5608a3c05609cc3d51aafd808a30fbfd822ee594fef55ad4
 
 if [ ! -f "$ENV_FILE" ]; then
   echo "Missing $ENV_FILE; no load-profile project was selected." >&2
@@ -22,6 +23,13 @@ if [ "$LOAD_PROJECT" = who_need_help ]; then
   exit 1
 fi
 
+case "$LOAD_PROJECT" in
+  *[!a-z0-9_-]* | '')
+    echo "LOAD_PROJECT contains unsupported characters." >&2
+    exit 1
+    ;;
+esac
+
 cd "$ROOT"
 docker compose \
   --env-file "$ENV_FILE" \
@@ -53,4 +61,27 @@ if image_id=$(docker image inspect --format '{{.Id}}' "$LOAD_TOOLS_IMAGE" 2>/dev
   fi
 fi
 
-echo "Removed the isolated load-profile containers and networks; its named volumes remain."
+# Prometheus and Grafana read run-scoped files under their container UIDs. Once
+# every container and network for this exact isolated project is gone, restore
+# the host owner and remove only that project's generated runtime directory.
+# Without this step, an otherwise successful cleanup can leave empty UID-owned
+# directories that the invoking user cannot remove.
+observability_runtime="$ROOT/tmp/observability/$LOAD_PROJECT"
+if [ -d "$observability_runtime" ]; then
+  if [ -n "$(docker ps -aq --filter "label=com.docker.compose.project=$LOAD_PROJECT")" ] ||
+    [ -n "$(docker network ls -q --filter "label=com.docker.compose.project=$LOAD_PROJECT")" ]; then
+    echo "Refusing to remove observability runtime while project resources remain." >&2
+    exit 1
+  fi
+
+  docker run --rm \
+    --user 0:0 \
+    --volume "$observability_runtime:/runtime" \
+    --entrypoint /bin/sh \
+    "$RUNTIME_OWNER_IMAGE" \
+    -euc "chown -R $(id -u):$(id -g) /runtime; chmod -R u+rwX /runtime"
+
+  find "$observability_runtime" -xdev -depth -delete
+fi
+
+echo "Removed the isolated load-profile containers, networks, and generated observability runtime; its named volumes remain."