Cut a long value in an approval between characters, not inside an emoji

CHANGELOG.md

@@ -78,6 +78,12 @@ Newest first. `Unreleased` is what is on `main` and not yet tagged.
   `COMPUTER_MEMORY_HIGH_PERCENT=0` and `COMPUTER_TAB_IDLE_MS=0` (Helm: `computers.memoryHighPercent`
   and `computers.tabIdleMs`) keep the old behaviour.
 
+### An approval cuts a long value between characters
+
+An approval shows what a Bot is about to type, write or send, cut to 2,000 characters, and each field
+on the OpenTag card is cut to 300. When the cut landed inside an emoji, the approval showed a "�"
+before the "…". The cut now drops the half character instead.
+
 ### A computer closes browsers nobody is using when its memory runs high
 
 A computer runs one browser for each Bot that is browsing, and the only limits were a count and half

server/src/approvals/types.ts

@@ -6,6 +6,7 @@ import {
   withApprovalContext,
 } from "@openbot/toolkit/continuation";
 import type { AuditInitiator } from "../audit";
+import { cutAtCodeUnits } from "../channels/text";
 
 /** `handled` answers a hand-off: the person did it themselves, so it is never executed for them. */
 export type ApprovalDecision =
@@ -374,7 +375,7 @@ export function approvalPreview(args: unknown, depth = 0): unknown {
         ]),
     );
   if (typeof args === "string")
-    return (args.length > 2000 ? `${args.slice(0, 1999)}…` : args)
+    return (args.length > 2000 ? `${cutAtCodeUnits(args, 1999)}…` : args)
       .replace(
         /((?:password|token|secret|api[_-]?key)\s*[=:]\s*)[^\s;]+/gi,
         "$1[private value]",

server/src/delivery/opentag.ts

@@ -19,6 +19,7 @@
  */
 import { timingSafeEqual } from "node:crypto";
 import { z } from "zod";
+import { cutAtCodeUnits } from "../channels/text";
 import { DELIVERY_REQUEST_TIMEOUT_MS } from "../timeouts";
 import {
   type BindingTransport,
@@ -391,7 +392,7 @@ export function approvalFields(preview: unknown) {
 }
 function clip(value: string | undefined, max = 300) {
   const text = value ?? "";
-  return text.length <= max ? text : `${text.slice(0, max - 1)}…`;
+  return text.length <= max ? text : `${cutAtCodeUnits(text, max - 1)}…`;
 }
 
 /** Minimal AG-UI SSE writer: `data: <event>\n\n` per event, as `@ag-ui/client`'s parser reads it. */

server/tests/approvals.test.ts

@@ -565,6 +565,26 @@ test("an approval preview shows what will be typed, written or sent, and still h
   });
 });
 
+test("an approval preview cuts a long value between characters, not inside an emoji", async () => {
+  const { approvalPreview } = await import("../src/approvals/types");
+  const { approvalFields } = await import("../src/delivery/opentag");
+  const hasLoneSurrogate = (text: string) =>
+    /[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]/.test(
+      text,
+    );
+  // Each cut lands between the two halves of the emoji that follows the letters.
+  const long = `${"a".repeat(1998)}😀${"b".repeat(100)}`;
+  const preview = approvalPreview(long) as string;
+  expect(hasLoneSurrogate(preview)).toBe(false);
+  expect(preview).toBe(`${"a".repeat(1998)}…`);
+
+  const field = approvalFields({
+    text: `${"a".repeat(298)}😀${"b".repeat(10)}`,
+  });
+  expect(hasLoneSurrogate(field[0]?.value ?? "")).toBe(false);
+  expect(field[0]?.value).toBe(`${"a".repeat(298)}…`);
+});
+
 test("an approved action interrupted before its result was saved continues the conversation once, without repeating", async () => {
   const store = storeFixture();
   const service = serviceModule.createApprovalService(store);