expect(result.endsWith("...")).toBe(true);

});

it("truncates on a code-point boundary without orphaning a surrogate half", () => {

// Body is 496 'a' + 😀 (U+1F600, a surrogate pair at UTF-16 indices 496-497)

// + "bcd". Raw `.slice(0, 497)` would split the emoji and leave a lone high

// surrogate (\uD83D) before the ellipsis. The fix must drop the half emoji.

const body = `${"a".repeat(496)}😀bcd`;

expect(body.length).toBe(501);

const result = summarizeMatrixReplyEvent({

event_id: "$original",

sender: "@alice:example.org",

type: "m.room.message",

origin_server_ts: Date.now(),

content: {

msgtype: "m.text",

body,

},

} as MatrixRawEvent);

if (result === undefined) {

throw new Error("expected truncated reply context");

}

expect(result).toBe(`${"a".repeat(496)}...`);

// No dangling high surrogate should survive the truncation.

expect(result.includes("\uD83D")).toBe(false);

});

it("handles media-only reply events", () => {

expect(

summarizeMatrixReplyEvent({

// Matrix plugin module implements reply context behavior.

import { sliceUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";

import type { MatrixClient } from "../sdk.js";

import { summarizeMatrixMessageContextEvent, trimMatrixMaybeString } from "./context-summary.js";

import type { MatrixRawEvent } from "./types.js";

if (value.length <= MAX_REPLY_BODY_LENGTH) {

return value;

}

return `${value.slice(0, MAX_REPLY_BODY_LENGTH - 3)}...`;

return `${sliceUtf16Safe(value, 0, MAX_REPLY_BODY_LENGTH - 3)}...`;

}

export function summarizeMatrixReplyEvent(event: MatrixRawEvent): string | undefined {