fix(msteams): keep truncated parent context text well-formed

Leon-SK668 · Leon-SK668 · commit ca210f75bf9b · 2026-06-26T14:24:17.000+08:00
summarizeParentMessage truncated the parent body with text.slice(0, PARENT_TEXT_MAX_CHARS - 1), which can cut a surrogate pair in half and emit a lone surrogate into the injected "Replying to @sender: …" system event. Use the shared truncateUtf16Safe helper so truncation falls back to a whole code-point boundary. Add a regression asserting the summary stays isWellFormed() when the limit lands inside an emoji.
diff --git a/extensions/msteams/src/thread-parent-context.test.ts b/extensions/msteams/src/thread-parent-context.test.ts
@@ -10,6 +10,11 @@ import {
   summarizeParentMessage,
 } from "./thread-parent-context.js";
 
+// Matches an unpaired UTF-16 surrogate (lone high or lone low), without relying
+// on the ES2024 String.prototype.isWellFormed() runtime API.
+const UNPAIRED_SURROGATE_RE =
+  /[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]/;
+
 describe("summarizeParentMessage", () => {
   it("returns undefined for missing message", () => {
     expect(summarizeParentMessage(undefined)).toBeUndefined();
@@ -81,6 +86,20 @@ describe("summarizeParentMessage", () => {
     expect(summary?.text.length).toBeLessThanOrEqual(400);
     expect(summary?.text.endsWith("…")).toBe(true);
   });
+
+  it("keeps truncated parent text well-formed when truncating surrogate pairs", () => {
+    const msg: GraphThreadMessage = {
+      id: "p1",
+      from: { user: { displayName: "Dana" } },
+      body: { content: `${"a".repeat(398)}🦞${"b".repeat(50)}`, contentType: "text" },
+    };
+
+    const summary = summarizeParentMessage(msg);
+
+    expect(summary?.text).not.toMatch(UNPAIRED_SURROGATE_RE);
+    expect(summary?.text).toBe(`${"a".repeat(398)}…`);
+    expect(summary?.text.endsWith("\ud83e…")).toBe(false);
+  });
 });
 
 describe("formatParentContextEvent", () => {
diff --git a/extensions/msteams/src/thread-parent-context.ts b/extensions/msteams/src/thread-parent-context.ts
@@ -17,6 +17,7 @@ import {
   asDateTimestampMs,
   resolveExpiresAtMsFromDurationMs,
 } from "openclaw/plugin-sdk/number-runtime";
+import { truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
 import { fetchChannelMessage, stripHtmlFromTeamsMessage } from "./graph-thread.js";
 import type { GraphThreadMessage } from "./graph-thread.js";
 
@@ -138,7 +139,9 @@ export function summarizeParentMessage(
   return {
     sender,
     text:
-      text.length > PARENT_TEXT_MAX_CHARS ? `${text.slice(0, PARENT_TEXT_MAX_CHARS - 1)}…` : text,
+      text.length > PARENT_TEXT_MAX_CHARS
+        ? `${truncateUtf16Safe(text, PARENT_TEXT_MAX_CHARS - 1)}…`
+        : text,
   };
 }
 
