fix(telegram): keep draft preview chunks surrogate-safe

extensions/telegram/src/draft-stream.test.ts

@@ -819,6 +819,20 @@ describe("createTelegramDraftStream", () => {
     expect(stream.lastDeliveredText?.()).toBe("1234567890");
   });
 
+  it("does not split surrogate pairs when clamping a first oversized non-final preview", async () => {
+    const api = createMockDraftApi();
+    const stream = createDraftStream(api, { maxChars: 10 });
+
+    stream.update("123456789😀tail");
+    await stream.flush();
+
+    expect(api.sendMessage).toHaveBeenCalledTimes(1);
+    const sentText = requireSendMessageCallText(api, 0);
+    expect(sentText).toBe("123456789");
+    expect(/[\uD800-\uDBFF](?![\uDC00-\uDFFF])/.test(sentText)).toBe(false);
+    expect(stream.lastDeliveredText?.()).toBe("123456789");
+  });
+
   it("finalizes overflow that was hidden by a clamped non-final preview", async () => {
     const api = createMockDraftApi();
     api.sendMessage

extensions/telegram/src/draft-stream.ts

@@ -5,6 +5,7 @@ import {
   takeMessageIdAfterStop,
 } from "openclaw/plugin-sdk/channel-outbound";
 import { formatErrorMessage } from "openclaw/plugin-sdk/error-runtime";
+import { sliceUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
 import { buildTelegramThreadParams, type TelegramThreadSpec } from "./bot/helpers.js";
 import { renderTelegramHtmlText, telegramHtmlToPlainTextFallback } from "./format.js";
 import {
@@ -169,7 +170,7 @@ function findTelegramDraftChunkLength(
       high = mid - 1;
     }
   }
-  return best;
+  return sliceUtf16Safe(text, 0, best).length;
 }
 
 export function createTelegramDraftStream(params: {