diff --git a/implementation/auditing/audit_engine.py b/implementation/auditing/audit_engine.py
index d416fde..b2ff25a 100644
--- a/implementation/auditing/audit_engine.py
+++ b/implementation/auditing/audit_engine.py
@@ -37,7 +37,7 @@ SEVERITY_ENHANCEMENT = "enhancement" # 🟩
 
 
 def _safe_get(data, *keys, default=None):
-    """Nested dict access without KeyError."""
+    """Nested dict access without KeyError. Last positional arg is default if not a key."""
     if not keys:
         return default
     cur = data
@@ -779,13 +779,23 @@ def to_markdown(findings, summary, contract):
 
 def main():
     if len(sys.argv) < 2:
-        print("Usage: audit_engine.py <multi_surface_json> [--json] [--md]")
+        print("Usage: audit_engine.py <multi_surface_json> [--json] [--md] [--output-dir DIR]")
         sys.exit(1)
 
     filepath = sys.argv[1]
     output_json = "--json" in sys.argv
     output_md = "--md" in sys.argv
 
+    # --output-dir: write results to directory instead of stdout
+    output_dir = None
+    i = 2
+    while i < len(sys.argv):
+        if sys.argv[i] == "--output-dir" and i + 1 < len(sys.argv):
+            output_dir = sys.argv[i + 1]
+            i += 2
+            continue
+        i += 1
+
     if not os.path.exists(filepath):
         print(f"Error: {filepath} not found")
         sys.exit(1)
@@ -796,28 +806,33 @@ def main():
     findings = analyze(contract)
     summary = summarize(findings, contract)
 
-    if output_md:
-        md = to_markdown(findings, summary, contract)
-        print(md)
-    elif output_json:
-        result = {
-            "audit_engine": "v1",
-            "timestamp": datetime.now(timezone.utc).isoformat(),
-            "business": _safe_get(contract, "name"),
-            "summary": summary,
-            "findings": findings,
-        }
-        print(json.dumps(result, indent=2))
+    result = {
+        "audit_engine": "v1",
+        "timestamp": datetime.now(timezone.utc).isoformat(),
+        "business": _safe_get(contract, "name"),
+        "summary": summary,
+        "findings": findings,
+    }
+
+    if output_dir:
+        os.makedirs(output_dir, exist_ok=True)
+        json_path = os.path.join(output_dir, "findings.json")
+        with open(json_path, "w") as f:
+            json.dump(result, f, indent=2)
+        print(f"Findings written to {json_path}", file=sys.stderr)
+
+        if output_md:
+            md = to_markdown(findings, summary, contract)
+            md_path = os.path.join(output_dir, "findings.md")
+            with open(md_path, "w") as f:
+                f.write(md)
+            print(f"Report written to {md_path}", file=sys.stderr)
     else:
-        # Default: JSON
-        result = {
-            "audit_engine": "v1",
-            "timestamp": datetime.now(timezone.utc).isoformat(),
-            "business": _safe_get(contract, "name"),
-            "summary": summary,
-            "findings": findings,
-        }
-        print(json.dumps(result, indent=2))
+        if output_md:
+            md = to_markdown(findings, summary, contract)
+            print(md)
+        else:
+            print(json.dumps(result, indent=2))
 
 
 if __name__ == "__main__":