diff --git a/mempalace/cli.py b/mempalace/cli.py
index 0a24abf..895aa87 100644
--- a/mempalace/cli.py
+++ b/mempalace/cli.py
@@ -202,6 +202,7 @@ def cmd_repair(args):
     print(f"  Extracted {len(all_ids)} drawers")
 
     # Backup and rebuild
+    palace_path = palace_path.rstrip(os.sep)
     backup_path = palace_path + ".backup"
     if os.path.exists(backup_path):
         shutil.rmtree(backup_path)
diff --git a/mempalace/mcp_server.py b/mempalace/mcp_server.py
index db2f32e..bffd3b2 100644
--- a/mempalace/mcp_server.py
+++ b/mempalace/mcp_server.py
@@ -881,7 +881,7 @@ def handle_request(request):
         }
     elif method == "tools/call":
         tool_name = params.get("name")
-        tool_args = params.get("arguments", {})
+        tool_args = params.get("arguments") or {}
         if tool_name not in TOOLS:
             return {
                 "jsonrpc": "2.0",
diff --git a/mempalace/normalize.py b/mempalace/normalize.py
index ac11469..3d12087 100644
--- a/mempalace/normalize.py
+++ b/mempalace/normalize.py
@@ -26,6 +26,9 @@ def normalize(filepath: str) -> str:
     Plain text files pass through unchanged.
     """
     try:
+        file_size = os.path.getsize(filepath)
+        if file_size > 500 * 1024 * 1024:  # 500 MB safety limit
+            raise IOError(f"File too large ({file_size // (1024*1024)} MB): {filepath}")
         with open(filepath, "r", encoding="utf-8", errors="replace") as f:
             content = f.read()
     except OSError as e:
diff --git a/mempalace/split_mega_files.py b/mempalace/split_mega_files.py
index ae801df..24b5956 100644
--- a/mempalace/split_mega_files.py
+++ b/mempalace/split_mega_files.py
@@ -182,6 +182,10 @@ def split_file(filepath, output_dir, dry_run=False):
     Returns list of output paths written (or would be written if dry_run).
     """
     path = Path(filepath)
+    max_size = 500 * 1024 * 1024  # 500 MB safety limit
+    if path.stat().st_size > max_size:
+        print(f"  SKIP: {path.name} exceeds {max_size // (1024*1024)} MB limit")
+        return []
     lines = path.read_text(errors="replace").splitlines(keepends=True)
 
     boundaries = find_session_boundaries(lines)
@@ -266,7 +270,11 @@ def main():
         files = sorted(src_dir.glob("*.txt"))
 
     mega_files = []
+    max_scan_size = 500 * 1024 * 1024  # 500 MB
     for f in files:
+        if f.stat().st_size > max_scan_size:
+            print(f"  SKIP: {f.name} exceeds {max_scan_size // (1024*1024)} MB limit")
+            continue
         lines = f.read_text(errors="replace").splitlines(keepends=True)
         boundaries = find_session_boundaries(lines)
         if len(boundaries) >= args.min_sessions: