diff --git a/design/prototype/serve.mjs b/design/prototype/serve.mjs
index 811eaf4..3d3ad9c 100644
--- a/design/prototype/serve.mjs
+++ b/design/prototype/serve.mjs
@@ -47,6 +47,19 @@ const server = http.createServer((req, res) => {
 
   let urlPath = decodeURIComponent(req.url.split('?')[0]);
   if (urlPath === '/') urlPath = '/index.html';
+
+  // i18n 单源:直接服务 canonical design/i18n/strings.json(不在原型内复制)。
+  // 原型与 Flutter app 共用同一份翻译数据(design/codegen/gen_l10n_dart.mjs 由它生成 Dart)。
+  if (urlPath === '/i18n/strings.json' || urlPath === '/strings.json') {
+    const sjPath = path.join(ROOT, '..', 'i18n', 'strings.json');
+    fs.readFile(sjPath, (err, data) => {
+      if (err) { res.writeHead(404, { 'Content-Type': 'text/plain; charset=utf-8' }); res.end('strings.json not found'); return; }
+      res.writeHead(200, { 'Content-Type': 'application/json; charset=utf-8', 'Cache-Control': 'no-store' });
+      res.end(data);
+    });
+    return;
+  }
+
   const filePath = path.join(ROOT, urlPath);
   if (!filePath.startsWith(ROOT)) { res.writeHead(403); res.end('forbidden'); return; }