From 35e8d7dda92001191cd18e557af395651fc8a2e3 Mon Sep 17 00:00:00 2001
From: misyaguziya <53165965+misyaguziya@users.noreply.github.com>
Date: Thu, 9 Oct 2025 18:43:12 +0900
Subject: [PATCH] =?UTF-8?q?=E3=82=B9=E3=83=AC=E3=83=83=E3=83=89=E3=82=BB?=
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---
 .../transliteration/transliteration_transliterator.py    | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src-python/models/transliteration/transliteration_transliterator.py b/src-python/models/transliteration/transliteration_transliterator.py
index 8aff912e..44464348 100644
--- a/src-python/models/transliteration/transliteration_transliterator.py
+++ b/src-python/models/transliteration/transliteration_transliterator.py
@@ -1,6 +1,7 @@
 from sudachipy import tokenizer
 from sudachipy import dictionary
 from typing import List, Dict, Any
+import threading
 try:
     from .transliteration_kana_to_hepburn import katakana_to_hepburn
 except ImportError:
@@ -14,6 +15,9 @@ class Transliterator:
     def __init__(self) -> None:
         self.tokenizer_obj = dictionary.Dictionary(dict_type="full").create()
         self.mode = tokenizer.Tokenizer.SplitMode.C
+        # Lock to prevent concurrent access to sudachipy tokenizer which may
+        # internally use Rust/PyO3 borrow semantics and raise "Already borrowed".
+        self._tokenizer_lock = threading.Lock()
 
     @staticmethod
     def is_kanji(ch: str) -> bool:
@@ -132,7 +136,10 @@ class Transliterator:
           results.
         """
 
-        tokens = self.tokenizer_obj.tokenize(text, self.mode)
+        # Tokenizer may raise RuntimeError: Already borrowed when called
+        # concurrently. Protect the call with a lock to serialize access.
+        with self._tokenizer_lock:
+            tokens = self.tokenizer_obj.tokenize(text, self.mode)
 
         results: List[Dict[str, Any]] = []
         for t in tokens: