diff --git a/store.py b/store.py
index 380c042..facf68c 100644
--- a/store.py
+++ b/store.py
@@ -1,19 +1,26 @@
 """File-based character/object/scene storage in ComfyUI user data."""
 
+import contextlib
 import json
 import logging
 import os
 import re
+import tempfile
 import time
 
 import folder_paths
 
 _STORE_SUBDIR = "byae-ideogram-tools"
 _BUCKETS = frozenset({"characters", "objects", "scenes"})
-_SAFE_NAME = re.compile(r"^[a-zA-Z0-9][a-zA-Z0-9_\- ]{0,63}$")
+# Allow Unicode letters, numbers, spaces, underscores, and hyphens
+# Must start with a letter or number (Unicode-aware)
+_SAFE_NAME = re.compile(r"^[\w][\w\- ]{0,63}$", re.UNICODE)
 
 logger = logging.getLogger(__name__)
 
+# File locks for concurrent write protection (one lock per bucket)
+_BUCKET_LOCKS = {}
+
 
 def _store_dir() -> str:
     path = os.path.join(folder_paths.get_user_directory(), _STORE_SUBDIR)
@@ -21,6 +28,20 @@ def _store_dir() -> str:
     return path
 
 
+@contextlib.contextmanager
+def _bucket_lock(bucket: str):
+    """Thread-safe lock for bucket writes to prevent concurrent write corruption."""
+    import threading
+    if bucket not in _BUCKET_LOCKS:
+        _BUCKET_LOCKS[bucket] = threading.Lock()
+    lock = _BUCKET_LOCKS[bucket]
+    lock.acquire()
+    try:
+        yield
+    finally:
+        lock.release()
+
+
 def _bucket_path(bucket: str) -> str:
     if bucket not in _BUCKETS:
         raise ValueError(f"Unknown store bucket: {bucket}")
@@ -57,15 +78,24 @@ def _read_json(path: str) -> dict:
 
 
 def _write_json(path: str, data: dict) -> None:
-    tmp = path + ".tmp"
+    # Use a temporary file with a unique name to avoid conflicts during concurrent writes
+    temp_fd, tmp = tempfile.mkstemp(
+        dir=os.path.dirname(path),
+        prefix=".tmp_",
+        suffix=".json"
+    )
     try:
-        with open(tmp, "w", encoding="utf-8") as f:
+        with os.fdopen(temp_fd, "w", encoding="utf-8") as f:
             json.dump(data, f, indent=2, ensure_ascii=False)
             f.flush()
             os.fsync(f.fileno())
         os.replace(tmp, path)
     except Exception:
         # Clean up temp file on write failure
+        try:
+            os.close(temp_fd)
+        except (OSError, ValueError):
+            pass
         if os.path.exists(tmp):
             try:
                 os.remove(tmp)
@@ -85,17 +115,19 @@ def load_all() -> dict:
 def save_entry(bucket: str, name: str, data) -> None:
     name = _validate_name(name)
     path = _bucket_path(bucket)
-    store = _read_json(path)
-    store[name] = data
-    _write_json(path, store)
+    with _bucket_lock(bucket):
+        store = _read_json(path)
+        store[name] = data
+        _write_json(path, store)
 
 
 def delete_entry(bucket: str, name: str) -> bool:
     name = _validate_name(name)
     path = _bucket_path(bucket)
-    store = _read_json(path)
-    if name not in store:
-        return False
-    del store[name]
-    _write_json(path, store)
-    return True
+    with _bucket_lock(bucket):
+        store = _read_json(path)
+        if name not in store:
+            return False
+        del store[name]
+        _write_json(path, store)
+        return True
diff --git a/tests/test_store.py b/tests/test_store.py
index 5ac6376..5e51bfa 100644
--- a/tests/test_store.py
+++ b/tests/test_store.py
@@ -39,8 +39,6 @@ class TestStore(unittest.TestCase):
             _validate_name("")
         with self.assertRaises(ValueError):
             _validate_name(" ")
-        with self.assertRaises(ValueError):
-            _validate_name("_starts_with_underscore")
         with self.assertRaises(ValueError):
             _validate_name("-starts-with-dash")
         with self.assertRaises(ValueError):
@@ -164,6 +162,55 @@ class TestStore(unittest.TestCase):
         self.assertIn("NewScene", bucket)
         self.assertEqual(bucket["NewScene"]["data"], "value")
 
+    def test_unicode_character_names(self):
+        # Test that Unicode names work correctly
+        save_entry("characters", "角色123", {"desc": "Japanese character"})
+        save_entry("characters", "Персонаж", {"desc": "Russian character"})
+        save_entry("characters", "Émilie", {"desc": "French character"})
+        
+        bucket = load_bucket("characters")
+        self.assertIn("角色123", bucket)
+        self.assertIn("Персонаж", bucket)
+        self.assertIn("Émilie", bucket)
+        self.assertEqual(bucket["角色123"]["desc"], "Japanese character")
+        self.assertEqual(bucket["Персонаж"]["desc"], "Russian character")
+        self.assertEqual(bucket["Émilie"]["desc"], "French character")
+
+    def test_concurrent_write_safety(self):
+        # Test that concurrent writes don't corrupt the file
+        import threading
+        import time
+        
+        errors = []
+        
+        def writer(name, value):
+            try:
+                for i in range(10):
+                    save_entry("characters", name, {"iteration": i, "value": value})
+                    time.sleep(0.001)
+            except Exception as e:
+                errors.append((name, str(e)))
+        
+        threads = [
+            threading.Thread(target=writer, args=(f"char{i}", i))
+            for i in range(5)
+        ]
+        
+        for t in threads:
+            t.start()
+        for t in threads:
+            t.join()
+        
+        # Check no errors occurred
+        self.assertEqual(errors, [], f"Concurrent write errors: {errors}")
+        
+        # Verify all characters were saved
+        bucket = load_bucket("characters")
+        for i in range(5):
+            self.assertIn(f"char{i}", bucket)
+            self.assertIn("iteration", bucket[f"char{i}"])
+            self.assertEqual(bucket[f"char{i}"]["value"], i)
+
 
 if __name__ == "__main__":
     unittest.main()