diff --git a/src/gateway/live-chat-projector.ts b/src/gateway/live-chat-projector.ts
index 72faadc77d82..f0e432d9d1c8 100644
--- a/src/gateway/live-chat-projector.ts
+++ b/src/gateway/live-chat-projector.ts
@@ -1,3 +1,4 @@
+import { sliceUtf16Safe } from "@openclaw/normalization-core/utf16-slice";
 // Gateway live chat projector.
 // Converts streaming assistant events into display-safe live chat text.
 import { stripInternalRuntimeContext } from "../agents/internal-runtime-context.js";
@@ -36,7 +37,7 @@ function capLiveAssistantBuffer(text: string): string {
   if (text.length <= MAX_LIVE_CHAT_BUFFER_CHARS) {
     return text;
   }
-  return text.slice(-MAX_LIVE_CHAT_BUFFER_CHARS);
+  return sliceUtf16Safe(text, -MAX_LIVE_CHAT_BUFFER_CHARS);
 }
 
 /** Merges assistant full-text and delta events into a capped live buffer. */
diff --git a/src/gateway/server-chat.stream-text-merge.test.ts b/src/gateway/server-chat.stream-text-merge.test.ts
index 846bc4decff8..2e287f546d85 100644
--- a/src/gateway/server-chat.stream-text-merge.test.ts
+++ b/src/gateway/server-chat.stream-text-merge.test.ts
@@ -93,4 +93,15 @@ describe("server chat stream text merge", () => {
     expect(result).toHaveLength(MAX_LIVE_CHAT_BUFFER_CHARS);
     expect(result.endsWith("bbbb")).toBe(true);
   });
+
+  it("does not start the capped tail with the low half of a surrogate pair", () => {
+    const safeTail = "y".repeat(MAX_LIVE_CHAT_BUFFER_CHARS - 1);
+    const result = resolveMergedAssistantText({
+      previousText: "",
+      nextText: `x🚀${safeTail}`,
+      nextDelta: "",
+    });
+
+    expect(result).toBe(safeTail);
+  });
 });