diff --git a/tools/hako_check.sh b/tools/hako_check.sh
index 42ae11eb..03acd87a 100644
--- a/tools/hako_check.sh
+++ b/tools/hako_check.sh
@@ -17,10 +17,24 @@ fi
 
 fail=0
 FORMAT="text"
+EXTRA_ARGS=""
 
-if [ "${1:-}" = "--format" ] && [ -n "${2:-}" ]; then
-  FORMAT="$2"; shift 2 || true
-fi
+# Parse optional flags (--format, --dead-code, --rules, etc.)
+while [ $# -gt 0 ]; do
+  case "${1:-}" in
+    --format)
+      FORMAT="$2"
+      shift 2 || true
+      ;;
+    --dead-code|--rules|--no-ast|--debug)
+      EXTRA_ARGS="$EXTRA_ARGS $1"
+      shift
+      ;;
+    *)
+      break
+      ;;
+  esac
+done
 list_targets() {
   local p="$1"
   if [ -d "$p" ]; then
@@ -64,7 +78,7 @@ run_one() {
   HAKO_ENABLE_USING=1 \
   NYASH_USING_AST=1 \
   NYASH_NY_COMPILER_TIMEOUT_MS="${NYASH_NY_COMPILER_TIMEOUT_MS:-8000}" \
-  "$BIN" --backend vm "$ROOT/tools/hako_check/cli.hako" -- "${args_arr[@]}" \
+  "$BIN" --backend vm "$ROOT/tools/hako_check/cli.hako" -- "${args_arr[@]}" --format "$FORMAT" $EXTRA_ARGS \
     >"/tmp/hako_lint_out_$$.log" 2>&1 || true
   local out rc
   out="$(cat "/tmp/hako_lint_out_$$.log")"; rc=0
diff --git a/tools/hako_check/cli.hako b/tools/hako_check/cli.hako
index 46a1de72..6531aff9 100644
--- a/tools/hako_check/cli.hako
+++ b/tools/hako_check/cli.hako
@@ -132,6 +132,15 @@ static box HakoAnalyzerBox {
         local no_ast_eff = no_ast
         if want_ast == 1 { no_ast_eff = 0 }
         ir = HakoAnalysisBuilderBox.build_from_source_flags(text, p, no_ast_eff)
+        // Fail-Fast: Guard against void return from builder
+        if ir == null || ir == void {
+          ir = new MapBox()
+          ir.set("path", p)
+          ir.set("methods", new ArrayBox())
+          ir.set("calls", new ArrayBox())
+          ir.set("boxes", new ArrayBox())
+          ir.set("entrypoints", new ArrayBox())
+        }
         // Phase 156: Integrate MIR CFG if available
         if mir_json_content != null { ir.set("_mir_json_text", mir_json_content) }
       } else {