diff --git a/scripts/gh.sh b/scripts/gh.sh
index 6113a75be6..06c15c847b 100755
--- a/scripts/gh.sh
+++ b/scripts/gh.sh
@@ -11,6 +11,15 @@ set -euo pipefail
 #   ./scripts/gh.sh search issues "search query" --limit 10
 #   ./scripts/gh.sh label list --limit 100
 
+export GH_HOST=github.com
+
+REPO="${GH_REPO:-${GITHUB_REPOSITORY:-}}"
+if [[ -z "$REPO" || "$REPO" == */*/* || "$REPO" != */* ]]; then
+  echo "Error: GH_REPO or GITHUB_REPOSITORY must be set to owner/repo format (e.g., GITHUB_REPOSITORY=anthropics/claude-code)" >&2
+  exit 1
+fi
+export GH_REPO="$REPO"
+
 ALLOWED_FLAGS=(--comments --state --limit --label)
 FLAGS_WITH_VALUES=(--state --limit --label)
 
@@ -21,6 +30,7 @@ case "$CMD" in
   "issue view"|"issue list"|"search issues"|"label list")
     ;;
   *)
+    echo "Error: only 'issue view', 'issue list', 'search issues', 'label list' are allowed (e.g., ./scripts/gh.sh issue view 123)" >&2
     exit 1
     ;;
 esac
@@ -45,6 +55,7 @@ for arg in "$@"; do
       fi
     done
     if [[ "$matched" == false ]]; then
+      echo "Error: only --comments, --state, --limit, --label flags are allowed (e.g., ./scripts/gh.sh issue list --state open --limit 20)" >&2
       exit 1
     fi
     FLAGS+=("$arg")
@@ -62,24 +73,24 @@ for arg in "$@"; do
   fi
 done
 
-REPO="${GH_REPO:-${GITHUB_REPOSITORY:-}}"
-
 if [[ "$CMD" == "search issues" ]]; then
-  if [[ -z "$REPO" ]]; then
-    exit 1
-  fi
   QUERY="${POSITIONAL[0]:-}"
   QUERY_LOWER=$(echo "$QUERY" | tr '[:upper:]' '[:lower:]')
   if [[ "$QUERY_LOWER" == *"repo:"* || "$QUERY_LOWER" == *"org:"* || "$QUERY_LOWER" == *"user:"* ]]; then
+    echo "Error: search query must not contain repo:, org:, or user: qualifiers (e.g., ./scripts/gh.sh search issues \"bug report\" --limit 10)" >&2
     exit 1
   fi
   gh "$SUB1" "$SUB2" "$QUERY" --repo "$REPO" "${FLAGS[@]}"
+elif [[ "$CMD" == "issue view" ]]; then
+  if [[ ${#POSITIONAL[@]} -ne 1 ]] || ! [[ "${POSITIONAL[0]}" =~ ^[0-9]+$ ]]; then
+    echo "Error: issue view requires exactly one numeric issue number (e.g., ./scripts/gh.sh issue view 123)" >&2
+    exit 1
+  fi
+  gh "$SUB1" "$SUB2" "${POSITIONAL[0]}" "${FLAGS[@]}"
 else
-  # Reject URLs in positional args to prevent cross-repo access
-  for pos in "${POSITIONAL[@]}"; do
-    if [[ "$pos" == http://* || "$pos" == https://* ]]; then
-      exit 1
-    fi
-  done
-  gh "$SUB1" "$SUB2" "${POSITIONAL[@]}" "${FLAGS[@]}"
+  if [[ ${#POSITIONAL[@]} -ne 0 ]]; then
+    echo "Error: issue list and label list do not accept positional arguments (e.g., ./scripts/gh.sh issue list --state open, ./scripts/gh.sh label list --limit 100)" >&2
+    exit 1
+  fi
+  gh "$SUB1" "$SUB2" "${FLAGS[@]}"
 fi