diff --git a/skills/ingest/scripts/run-ingest.sh b/skills/ingest/scripts/run-ingest.sh
index 4ae9c97..032761c 100644
--- a/skills/ingest/scripts/run-ingest.sh
+++ b/skills/ingest/scripts/run-ingest.sh
@@ -36,7 +36,7 @@ contradictions="$(jq -r '.contradictions // "None"' "$manifest")"
 
 [[ -n "$raw_source" && "$raw_source" != "null" ]] || fail "manifest" "raw_source missing"
 
-slug="$(bash "${SCRIPTS}/slug.sh" "$raw_source")"
+slug="$(bash "${SCRIPTS}/slug.sh" "$raw_source")" || fail "slug" "empty or invalid slug for ${raw_source}"
 
 # --- collect touched paths ---
 mapfile -t created_paths  < <(jq -r '.pages[] | select(.status=="created")  | .path' "$manifest")
diff --git a/skills/ingest/scripts/slug.sh b/skills/ingest/scripts/slug.sh
index a5711ac..2f7fdc5 100644
--- a/skills/ingest/scripts/slug.sh
+++ b/skills/ingest/scripts/slug.sh
@@ -13,6 +13,11 @@ input="${1:?usage: slug.sh <path-or-title>}"
 base="${input##*/}"
 base="${base%.*}"
 
-printf '%s\n' "$base" \
+slug="$(printf '%s\n' "$base" \
   | tr '[:upper:]' '[:lower:]' \
-  | sed -E 's/[^a-z0-9]+/-/g; s/-{2,}/-/g; s/^-+//; s/-+$//'
+  | sed -E 's/[^a-z0-9]+/-/g; s/-{2,}/-/g; s/^-+//; s/-+$//')"
+
+# An all-symbols input (e.g. "!!!.md") collapses to "" — refuse rather than emit a
+# broken/empty slug that would produce an invalid branch name downstream.
+[[ -n "$slug" ]] || { echo "slug: empty result for input '${input}'" >&2; exit 1; }
+printf '%s\n' "$slug"