From 7bef17d7d8efcd30f71290f36dd36cc6a6feaf0b Mon Sep 17 00:00:00 2001
From: Day Dreamer <87640074+HugoXK@users.noreply.github.com>
Date: Sat, 31 Oct 2026 17:34:38 +0800
Subject: [PATCH] host: cut the last code-unit bounds on a code point boundary
 (#1916)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Eight rows (nine cuts) still used slice(0, max) on text that can carry an
emoji: the claim cue's fallback reference, the task lead's name in a member
prompt, a failed group Session's error text, read_own_chat's query and
anchor, an open page's address and title, a diagnostics browser-log line,
and cleanPeerName. Each now goes through cut(), so the prefix stops before a
split surrogate pair.

shared/remote-label.js cannot import host/text.js, so the boundary rule moved
to shared/text-boundary.js and host/text.js builds cut on it: one
implementation for both layers. The browser test joins patch 0014 beside
browser.js; 0001/0007/0008/0012/0014 are regenerated and the new shared file
and client bundle are in files/.

Docs-not-needed: core/client.js is regenerated only — the change reaches it from shared/remote-label.js (a bundle input), and no core/src/client file changed.
---
 changelog.d/1916-code-unit-cuts.fixed.md      |   1 +
 core/client.js                                |  12 +-
 core/src/host/browser.js                      |   2 +-
 core/src/host/diagnostics.js                  |   4 +-
 core/src/host/groups.js                       |  10 +-
 core/src/host/text.js                         |  19 +--
 core/src/shared/remote-label.js               |   6 +-
 core/src/shared/text-boundary.js              |  16 +++
 core/test/browser-channel.test.js             |  26 +++-
 core/test/claim-cue.test.js                   |  19 ++-
 core/test/diagnostics.test.js                 |  17 +++
 core/test/group-bot-label.test.js             |   8 ++
 core/test/group-work.test.js                  |  56 +++++++-
 docs/subsystems/core-host.md                  |   4 +-
 patches/ds-bot/0001-core-fixes.patch          | 123 +++++++++++++++---
 patches/ds-bot/0007-version-and-tooling.patch |  24 ++++
 patches/ds-bot/0008-client-bundle.patch       |  49 ++++---
 patches/ds-bot/0012-room-membership.patch     |  24 +++-
 patches/ds-bot/0014-flybot-branding.patch     |  48 +++++++
 .../ds-bot/files/src/shared/remote-label.js   |   6 +-
 .../ds-bot/files/src/shared/text-boundary.js  |  16 +++
 patches/ds-bot/files/test/claim-cue.test.js   |  19 ++-
 .../ds-bot/files/test/group-bot-label.test.js |   8 ++
 patches/ds-bot/topics.json                    |   3 +-
 24 files changed, 444 insertions(+), 76 deletions(-)
 create mode 100644 changelog.d/1916-code-unit-cuts.fixed.md
 create mode 100644 core/src/shared/text-boundary.js
 create mode 100644 patches/ds-bot/files/src/shared/text-boundary.js

diff --git a/changelog.d/1916-code-unit-cuts.fixed.md b/changelog.d/1916-code-unit-cuts.fixed.md
new file mode 100644
index 000000000..217fc9f74
--- /dev/null
+++ b/changelog.d/1916-code-unit-cuts.fixed.md
@@ -0,0 +1 @@
+Eight more places stopped storing or showing half of an emoji ([#1916](https://github.com/ThinkFlowLab/FlyBot/issues/1916)): the claim cue's fallback reference, the task lead's name in a member's prompt, a failed group Session's error text, `read_own_chat`'s query and anchor, an open page's address and title, a diagnostics browser-log line, and a friend's Bot name now cut on a code point boundary. The rule itself moved to `core/src/shared/text-boundary.js`, so the shared label code and the host's `cut` use one implementation instead of two.
diff --git a/core/client.js b/core/client.js
index aaa92232d..279ed1ec5 100644
--- a/core/client.js
+++ b/core/client.js
@@ -1718,10 +1718,18 @@ var call = async (endpoint, payload, signal) => {
   return result.value;
 };
 
+// src/shared/text-boundary.js
+var isHighSurrogate = (code) => code >= 55296 && code <= 56319;
+var isLowSurrogate = (code) => code >= 56320 && code <= 57343;
+var codePointStart = (text2, at) => at > 0 && isLowSurrogate(text2.charCodeAt(at)) && isHighSurrogate(text2.charCodeAt(at - 1)) ? at - 1 : at;
+var codePointEnd = (text2, end) => end > 0 && isHighSurrogate(text2.charCodeAt(end - 1)) && isLowSurrogate(text2.charCodeAt(end)) ? end - 1 : end;
+var cut = (text2, max) => ({ text: text2.slice(0, codePointEnd(text2, max)), cut: text2.length > max });
+
 // src/shared/remote-label.js
 function cleanPeerName(name, fallback = "") {
-  const text2 = String(name ?? "").replace(/[\u0000-\u001f\u007f-\u009f\u2028\u2029]/g, " ").replace(/[[\]"`<>]/g, "").replace(/\s+/g, " ").trim().slice(0, 60);
-  return text2 || fallback;
+  const text2 = String(name ?? "").replace(/[\u0000-\u001f\u007f-\u009f\u2028\u2029]/g, " ").replace(/[[\]"`<>]/g, "").replace(/\s+/g, " ").trim();
+  const label = cut(text2, 60).text;
+  return label || fallback;
 }
 function normRemoteHandle(handle) {
   return `@${String(handle ?? "").trim().replace(/^@+/, "").toLowerCase()}`;
diff --git a/core/src/host/browser.js b/core/src/host/browser.js
index c12a9afa4..1347f2fc0 100644
--- a/core/src/host/browser.js
+++ b/core/src/host/browser.js
@@ -251,7 +251,7 @@ export function install(rt) {
     if (value === null || typeof value !== 'object') return open
     for (const [botId, page] of Object.entries(value).slice(0, OPEN_MAX)) {
       if (rt.botOf(botId) === undefined || typeof page?.url !== 'string') continue
-      open[botId] = { url: page.url.slice(0, 2000), title: String(page.title ?? '').slice(0, 300) }
+      open[botId] = { url: cut(page.url, 2000).text, title: cut(String(page.title ?? ''), 300).text }
     }
     return open
   }
diff --git a/core/src/host/diagnostics.js b/core/src/host/diagnostics.js
index c2daf6dff..f8a9215c8 100644
--- a/core/src/host/diagnostics.js
+++ b/core/src/host/diagnostics.js
@@ -208,7 +208,7 @@ export function install(rt) {
   }
 
   const sanitizeClient = (client) => {
-    const pick = (value, max) => (typeof value === 'string' ? clean(value.slice(0, max)) : undefined)
+    const pick = (value, max) => (typeof value === 'string' ? clean(cut(value, max).text) : undefined)
     return {
       surface: pick(client?.surface, 40),
       language: pick(client?.language, 20),
@@ -217,7 +217,7 @@ export function install(rt) {
   }
   const sanitizeClientEntries = list => (Array.isArray(list) ? list : []).slice(-20).flatMap((item) => {
     if (typeof item?.text !== 'string' || typeof item.time !== 'number') return []
-    return [{ time: item.time, level: item.level === 'warn' ? 'warn' : 'error', source: 'browser', text: clean(item.text.slice(0, 500)), ...(typeof item.code === 'string' ? { code: clean(item.code.slice(0, 40)) } : {}) }]
+    return [{ time: item.time, level: item.level === 'warn' ? 'warn' : 'error', source: 'browser', text: clean(cut(item.text, 500).text), ...(typeof item.code === 'string' ? { code: clean(cut(item.code, 40).text) } : {}) }]
   })
 
   async function report(body = {}) {
diff --git a/core/src/host/groups.js b/core/src/host/groups.js
index 76eefe12c..f31897ee7 100644
--- a/core/src/host/groups.js
+++ b/core/src/host/groups.js
@@ -48,7 +48,7 @@ export function claimCueText(task) {
   const title = claimLine(task?.title, 300)
   if (title === '') return ''
   const found = title.match(/^#(\d{1,7})\b/) ?? title.match(/#(\d{1,7})\b/)
-  const ref = found ? `#${found[1]}` : title.slice(0, CLAIM_CUE_REF_MAX)
+  const ref = found ? `#${found[1]}` : cut(title, CLAIM_CUE_REF_MAX).text
   const rest = found ? title.slice(title.indexOf(found[0]) + found[0].length).trim() : ''
   const step = claimLine(task?.note, CLAIM_CUE_STEP_MAX) || claimLine(rest, CLAIM_CUE_STEP_MAX)
   return step === '' ? `接了 ${ref}` : `接了 ${ref}，第一步是 ${step}`
@@ -327,7 +327,7 @@ export function install(rt) {
     if (leadId === member.id) {
       return 'You are this room\'s task lead (总负责人) for the board. When the group is given a job, assign it on the board with track_tasks: one overall task, and a subtask for each part (assignee is that Bot\'s name). Nobody else plans. A chat line does not assign. A card you assign is claimed: that Bot starts the work in its own chat and does not wait for a confirmation. Progress is that card\'s column and progress. A question a person has to decide is one short post in this group; do not @ a Bot to hand the work on.'
     }
-    const name = String(rt.botOf(leadId)?.name ?? 'The task lead').replace(/[\r\n]+/g, ' ').slice(0, 80)
+    const name = cut(String(rt.botOf(leadId)?.name ?? 'The task lead').replace(/[\r\n]+/g, ' '), 80).text
     return `${name} is this room's task lead (总负责人) for the board: it assigns the parts on the board. Claim the card it assigns you by setting its column to in-progress with track_tasks, and update that card's column and progress as the work moves. Do not record a new plan, assign work, or post a status in the group. @Name only wakes someone; it does not assign. Start the work in your own chat; do not wait for a confirmation. A question a person has to decide is one short post in this group; do not @ a Bot to hand the work on.`
   }
 
@@ -719,7 +719,7 @@ export function install(rt) {
         round.speaking = null
         slot.status = 'failed'
         round.failed.push(member.name)
-        round.replies.push({ kind: 'failed', botId: member.id, name: member.name, color: member.color, code: 'SESSION', text: String(error?.message ?? error).slice(0, 300), time: Date.now() })
+        round.replies.push({ kind: 'failed', botId: member.id, name: member.name, color: member.color, code: 'SESSION', text: cut(String(error?.message ?? error), 300).text, time: Date.now() })
         continue
       }
       const prompt = roomPrompt(room, member, round)
@@ -961,8 +961,8 @@ export function install(rt) {
       if (botId === undefined) return 'Only Bots on the team can use read_own_chat.'
       const member = rt.botOf(botId)
       const room = rt.roomOf(owner?.roomId)
-      const query = String(args.query ?? '').trim().slice(0, 80)
-      const around = String(args.around ?? '').trim().slice(0, 40)
+      const query = cut(String(args.query ?? '').trim(), 80).text
+      const around = cut(String(args.around ?? '').trim(), 40).text
       const parts = rt.partsOf(botId)
       const number = Number.isInteger(args.part) ? args.part : undefined
       if (room !== undefined && member !== undefined) {
diff --git a/core/src/host/text.js b/core/src/host/text.js
index 5b109c849..c2f5e7878 100644
--- a/core/src/host/text.js
+++ b/core/src/host/text.js
@@ -1,6 +1,9 @@
 // Pure text helpers shared by the host modules: message text, names, model refs,
 // cutting and estimating text, and the clock format of chat anchors.
 import { COLORS, EXTRA_COLORS, LEGACY_COLORS, OWN_CHAT_LINE_MAX } from './constants.js'
+import { codePointEnd, codePointStart, cut } from '../shared/text-boundary.js'
+
+export { cut }
 
 // A color id saved under its legacy name reads as the current one.
 export const currentColor = color => (typeof color === 'string' && Object.hasOwn(LEGACY_COLORS, color) ? LEGACY_COLORS[color] : color)
@@ -34,18 +37,10 @@ export const codePoints = (text) => {
   return n
 }
 
-const isHighSurrogate = code => code >= 0xd800 && code <= 0xdbff
-const isLowSurrogate = code => code >= 0xdc00 && code <= 0xdfff
-
-// A cut moves back onto a code point boundary: half of a surrogate pair reaches a UTF-8 encoder as
-// U+FFFD, so a clipped emoji would show up as a replacement character at every exit (#1642 for the
-// client side, here for the host).
-const codePointStart = (text, at) => (at > 0 && isLowSurrogate(text.charCodeAt(at)) && isHighSurrogate(text.charCodeAt(at - 1)) ? at - 1 : at)
-const codePointEnd = (text, end) => (end > 0 && isHighSurrogate(text.charCodeAt(end - 1)) && isLowSurrogate(text.charCodeAt(end)) ? end - 1 : end)
-
-// A bounded prefix that never splits a surrogate pair (#1912): every other host module cuts its own
-// archive text, and a half pair is stored as U+FFFD. `cut` says whether anything was dropped.
-export const cut = (text, max) => ({ text: text.slice(0, codePointEnd(text, max)), cut: text.length > max })
+// A cut moves back onto a code point boundary (#1642 client side, #1912 here, #1916 shared): half of
+// a surrogate pair reaches a UTF-8 encoder as U+FFFD, so a clipped emoji shows up as a replacement
+// character at every exit. The boundary rule itself lives in `shared/text-boundary.js`, because a
+// shared label (`shared/remote-label.js`) bounds a peer name too and must not import this module.
 
 // The part of a long message around the first match, so a search hit stays visible.
 export const excerpt = (text, wanted, max = OWN_CHAT_LINE_MAX) => {
diff --git a/core/src/shared/remote-label.js b/core/src/shared/remote-label.js
index 7312732e0..f229208c2 100644
--- a/core/src/shared/remote-label.js
+++ b/core/src/shared/remote-label.js
@@ -1,10 +1,12 @@
 // Display labels for a friend's published Bot and for a room the owner did not start.
 // Peer-controlled strings (names, homes, handles) are untrusted: strip controls and
 // markup so a name cannot look like instructions when it later reaches a model.
+import { cut } from './text-boundary.js'
 
 export function cleanPeerName(name, fallback = '') {
-  const text = String(name ?? '').replace(/[\u0000-\u001f\u007f-\u009f\u2028\u2029]/g, ' ').replace(/[[\]"`<>]/g, '').replace(/\s+/g, ' ').trim().slice(0, 60)
-  return text || fallback
+  const text = String(name ?? '').replace(/[\u0000-\u001f\u007f-\u009f\u2028\u2029]/g, ' ').replace(/[[\]"`<>]/g, '').replace(/\s+/g, ' ').trim()
+  const label = cut(text, 60).text
+  return label || fallback
 }
 
 export function normRemoteHandle(handle) {
diff --git a/core/src/shared/text-boundary.js b/core/src/shared/text-boundary.js
new file mode 100644
index 000000000..af6579e24
--- /dev/null
+++ b/core/src/shared/text-boundary.js
@@ -0,0 +1,16 @@
+// Where a bounded prefix may end. Both sides bound text (#1908/#1912/#1916): the host cuts what a
+// Bot reads back and what it stores, and a shared label cuts a peer's name. A cut that lands between
+// the halves of a surrogate pair reaches a UTF-8 encoder as U+FFFD, so every bound goes through here
+// instead of `slice`, and `host/text.js` builds its `cut` on this one implementation.
+
+const isHighSurrogate = code => code >= 0xd800 && code <= 0xdbff
+const isLowSurrogate = code => code >= 0xdc00 && code <= 0xdfff
+
+// The start of a bounded window, moved back onto a code point boundary.
+export const codePointStart = (text, at) => (at > 0 && isLowSurrogate(text.charCodeAt(at)) && isHighSurrogate(text.charCodeAt(at - 1)) ? at - 1 : at)
+
+// The end of a bounded prefix, moved back onto a code point boundary.
+export const codePointEnd = (text, end) => (end > 0 && isHighSurrogate(text.charCodeAt(end - 1)) && isLowSurrogate(text.charCodeAt(end)) ? end - 1 : end)
+
+// A bounded prefix that never splits a surrogate pair. `cut` says whether anything was dropped.
+export const cut = (text, max) => ({ text: text.slice(0, codePointEnd(text, max)), cut: text.length > max })
diff --git a/core/test/browser-channel.test.js b/core/test/browser-channel.test.js
index e49ae0ef1..0ee67cbe0 100644
--- a/core/test/browser-channel.test.js
+++ b/core/test/browser-channel.test.js
@@ -1,6 +1,6 @@
 import { test } from 'node:test'
 import assert from 'node:assert/strict'
-import { createBrowserChannel, pageText, partEnd } from '../src/host/browser.js'
+import { createBrowserChannel, install, pageText, partEnd } from '../src/host/browser.js'
 
 const ids = items => items.map(item => item.id)
 
@@ -141,3 +141,27 @@ test('partEnd prefers a blank line, then a line break, and cuts hard only withou
   assert.equal(partEnd('a\n' + 'b'.repeat(20), 0, 10), 10)
   assert.equal(partEnd('short', 0, 10), 5)
 })
+
+// #1916: the open-page snapshot is what a Bot reads back from outside the team, and both bounds
+// are code-unit ones: 2000 for an address and 300 for a title must not land inside an emoji.
+test('the open-page snapshot never cuts a title or an address in half (#1916)', () => {
+  const registered = []
+  const rt = {
+    ctx: { get: () => ({ name: 'desktop' }), effect: () => {}, tools: { register: (tool) => registered.push(tool) } },
+    config: {},
+    botOf: () => ({ id: 'a' }),
+  }
+  install(rt)
+  const open = rt.browserOpen({
+    a: { url: `${'a'.repeat(1999)}\u{1F600}tail`, title: `${'b'.repeat(299)}\u{1F600}tail` },
+  })
+  assert.equal(open.a.url.isWellFormed(), true)
+  assert.equal(open.a.title.isWellFormed(), true)
+  assert.equal(open.a.url, 'a'.repeat(1999))
+  assert.equal(open.a.title, 'b'.repeat(299))
+  // A cut that lands on a whole character keeps it.
+  const roomy = rt.browserOpen({ a: { url: `${'a'.repeat(1998)}\u{1F600}`, title: `${'b'.repeat(298)}\u{1F600}` } })
+  assert.equal(roomy.a.url, `${'a'.repeat(1998)}\u{1F600}`)
+  assert.equal(roomy.a.title, `${'b'.repeat(298)}\u{1F600}`)
+  assert.equal(registered.length > 0, true)
+})
diff --git a/core/test/claim-cue.test.js b/core/test/claim-cue.test.js
index 0aa31cf61..feabe4a11 100644
--- a/core/test/claim-cue.test.js
+++ b/core/test/claim-cue.test.js
@@ -10,7 +10,7 @@ import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { test } from 'node:test'
 import { createRuntime } from '../index.js'
-import { CLAIM_CUE_REPEAT_MS } from '../src/host/groups.js'
+import { CLAIM_CUE_REPEAT_MS, claimCueText } from '../src/host/groups.js'
 import { fakeContext } from './fake-ctx.js'
 
 const team = () => ({
@@ -180,3 +180,20 @@ test('a claim outside a room posts no line (#1253)', async (t) => {
 test('the repeat window is a stated number of minutes, not forever (#1253)', () => {
   assert.equal(CLAIM_CUE_REPEAT_MS, 30 * 60 * 1000)
 })
+
+// #1916: the reference of a title with no issue number is a bounded prefix, and the bound is a
+// code-unit one: 60 must not land between the halves of an emoji, or the room notice and the
+// room log both keep an ill-formed string.
+const utf8Prefix = (whole, part) => Buffer.from(part, 'utf8').equals(Buffer.from(whole, 'utf8').subarray(0, Buffer.byteLength(part)))
+
+test('a claim cue reference cut at 60 never splits a surrogate pair (#1916)', () => {
+  const title = `${'a'.repeat(59)}\u{1F600}tail`
+  const ref = claimCueText({ title }).replace(/^接了 /, '')
+  assert.equal(ref.isWellFormed(), true)
+  assert.equal(ref.includes('\uFFFD'), false)
+  assert.ok(ref.length <= 60, `ref is ${ref.length} units`)
+  assert.equal(utf8Prefix(title, ref), true, 'the ref is a byte prefix of the title')
+  // A cut that lands on a whole character keeps the whole character.
+  const roomy = claimCueText({ title: `${'a'.repeat(58)}\u{1F600}tail` }).replace(/^接了 /, '')
+  assert.equal(roomy, `${'a'.repeat(58)}\u{1F600}`)
+})
diff --git a/core/test/diagnostics.test.js b/core/test/diagnostics.test.js
index ed54d6ebe..231934cdb 100644
--- a/core/test/diagnostics.test.js
+++ b/core/test/diagnostics.test.js
@@ -92,6 +92,23 @@ test('warnings are kept, cleaned, written to the log, and read back after a rest
   quiet.mock.restore()
 })
 
+// #1916: the browser-log lines in the report are bounded, and those bounds are code-unit ones:
+// a line cut inside an emoji is stored and shown as U+FFFD in a report meant for a public issue.
+test('a browser-log line cut at its bound never splits a surrogate pair (#1916)', async (t) => {
+  const home = mkdtempSync(join(tmpdir(), 'ds-bot-diag-'))
+  t.after(() => rmSync(home, { recursive: true, force: true, maxRetries: 5 }))
+  const rt = host(home, { config: { diagnosticsFile: false } })
+  const report = await rt.diagnostics.report({
+    clientErrors: [{ time: 1, text: `${'x'.repeat(499)}\u{1F600}tail`, code: `${'y'.repeat(39)}\u{1F600}tail` }],
+  })
+  const line = report.markdown.split('\n').find(item => item.includes('ERROR browser')) ?? ''
+  assert.notEqual(line, '')
+  assert.equal(line.isWellFormed(), true)
+  assert.equal(line.includes('\ufffd'), false)
+  assert.ok(line.includes('x'.repeat(499)), 'the text keeps its whole-character prefix')
+  assert.ok(line.includes(`[${'y'.repeat(39)}]`), `expected the code prefix, got ${line}`)
+})
+
 test('warnings send only cleaned text to the logger and stderr', (t) => {
   const home = mkdtempSync(join(tmpdir(), 'ds-bot-diag-'))
   t.after(() => rmSync(home, { recursive: true, force: true, maxRetries: 5 }))
diff --git a/core/test/group-bot-label.test.js b/core/test/group-bot-label.test.js
index 08ae245fd..f9c37ff94 100644
--- a/core/test/group-bot-label.test.js
+++ b/core/test/group-bot-label.test.js
@@ -117,3 +117,11 @@ test('#526: real names stay as they are', () => {
   const view = roster([seatMine, { ...reviewer, label: undefined }], 'group')
   assert.equal(remoteSpeaker({ remote: { handle }, senderName: 'Reviewer' }, view, 'r').name, 'Reviewer (flybot682b8a43)')
 })
+
+// #1916: a friend's Bot or room name reaches a display label, and its 60-unit bound must not land
+// inside an emoji: the half pair would show as U+FFFD wherever the label is drawn.
+test('a peer name cut at 60 never splits a surrogate pair (#1916)', () => {
+  assert.equal(labels.cleanPeerName(`${'b'.repeat(59)}\u{1F600}tail`), 'b'.repeat(59))
+  assert.equal(labels.cleanPeerName(`${'b'.repeat(58)}\u{1F600}tail`), `${'b'.repeat(58)}\u{1F600}`)
+  assert.equal(labels.cleanPeerName(`${'b'.repeat(59)}\u{1F600}tail`, 'fallback').isWellFormed(), true)
+})
diff --git a/core/test/group-work.test.js b/core/test/group-work.test.js
index 0be1eef2e..7bfaec18d 100644
--- a/core/test/group-work.test.js
+++ b/core/test/group-work.test.js
@@ -3,7 +3,7 @@ import { mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { test } from 'node:test'
-import { apply } from '../index.js'
+import { createRuntime, provideFlyBot } from '../index.js'
 import { fakeContext } from './fake-ctx.js'
 import { ROOM_LATE_ROUNDS, ROOM_WORK_GRACE_MS } from '../src/host/constants.js'
 import { compactStatus, prepareRoomLine } from '../src/host/room-context.js'
@@ -71,7 +71,8 @@ async function start(t, room, history = {}) {
   let route
   const register = ctx.connection.fetch.register
   ctx.connection.fetch.register = (options) => { route = options; return register(options) }
-  apply(ctx, { home })
+  const rt = createRuntime(ctx, { home })
+  provideFlyBot(ctx, rt.flybot)
   t.after(async () => {
     await ctx.dispose()
     rmSync(home, { recursive: true, force: true, maxRetries: 5, retryDelay: 20 })
@@ -116,7 +117,7 @@ async function start(t, room, history = {}) {
     return { content: post.content, source: post.source }
   }
   await tool('list_bots', {}, 'a')
-  return { home, agentOf, emit, tool, call, begin, finish, round, say, takePost }
+  return { home, ctx, rt, agentOf, emit, tool, call, begin, finish, round, say, takePost }
 }
 
 const settle = async (check) => {
@@ -466,6 +467,55 @@ test('a kind-carrying room line stays verbatim in the store (#1251)', async (t)
   assert.equal(prepareRoomLine(long), long)
 })
 
+// #1916: the lookup line goes into the room log and is also what the search matches, so a bound
+// that lands inside an emoji would store an ill-formed string and make the character unsearchable.
+const utf8Prefix = (whole, part) => Buffer.from(part, 'utf8').equals(Buffer.from(whole, 'utf8').subarray(0, Buffer.byteLength(part)))
+
+test('a read_own_chat query or anchor cut at its bound never splits a surrogate pair (#1916)', async (t) => {
+  const host = await start(t)
+  const log = () => JSON.parse(readFileSync(join(host.home, 'state.json'), 'utf8')).rooms.r1.log
+  const query = `${'a'.repeat(79)}\u{1F600}permalink`
+  await host.tool('read_own_chat', { query }, 'gb')
+  await settle(() => log().length === 1)
+  assert.equal(log()[0].text.isWellFormed(), true)
+  assert.ok(log()[0].text.length <= 80, `query is ${log()[0].text.length} units`)
+  assert.equal(utf8Prefix(query, log()[0].text), true, 'the stored query is a byte prefix of the input')
+  const around = `${'b'.repeat(39)}\u{1F600}anchor`
+  await host.tool('read_own_chat', { around }, 'gb')
+  await settle(() => log().length === 2)
+  assert.equal(log()[1].text.isWellFormed(), true)
+  assert.ok(log()[1].text.length <= `around ${'b'.repeat(39)}`.length, `anchor is ${log()[1].text.length} units`)
+  assert.equal(utf8Prefix(`around ${around}`, log()[1].text), true, 'the stored anchor is a byte prefix of the input')
+})
+
+// #1916: the task lead's name goes into every other member's system prompt, and a Bot name is the
+// owner's to set, emoji included (#1182).
+test('the task lead name in a member prompt never splits a surrogate pair (#1916)', async (t) => {
+  const host = await start(t, { taskLead: 'a' })
+  const name = `${'l'.repeat(79)}\u{1F600}tail`
+  host.rt.state.bots.a.name = name
+  const prompt = host.ctx.sections.get('bot-room').text({ agent: { id: 'gb' } })
+  assert.equal(prompt.isWellFormed(), true, 'the room prompt is well formed')
+  assert.equal(prompt.includes('\uFFFD'), false)
+  assert.ok(prompt.includes('l'.repeat(79)), 'the whole-character prefix is kept')
+})
+
+// #1916: a group Session that cannot be opened reports its error into the room (#1253 notice path),
+// so the 300-unit bound on that text must not land inside an emoji.
+test('a failed group Session reports its error without splitting a surrogate pair (#1916)', async (t) => {
+  const host = await start(t)
+  // No Session for Writer yet: the next round has to open one, and opening it fails.
+  delete host.rt.state.rooms.r1.sessions.b
+  host.ctx.sessionController.create = async () => { throw new Error(`${'e'.repeat(299)}\u{1F600}tail`) }
+  const result = host.round('c1', host.say('@Writer 汇报'))
+  await settle(() => result() !== undefined)
+  const failed = result().replies.find(reply => reply.kind === 'failed')
+  assert.ok(failed, `no failed reply: ${JSON.stringify(result())}`)
+  assert.equal(failed.text.isWellFormed(), true)
+  assert.equal(failed.text.includes('\uFFFD'), false)
+  assert.ok(failed.text.length <= 300, `text is ${failed.text.length} units`)
+})
+
 // #1906: a search shows its best 20 hits and a bare read the latest 12, and neither said
 // how much it left out, so a user asking "didn't we decide X?" could think the deciding
 // message was gone. The caps stay; the answer says what it did not show.
diff --git a/docs/subsystems/core-host.md b/docs/subsystems/core-host.md
index 7602d4ca4..8e6f6b69b 100644
--- a/docs/subsystems/core-host.md
+++ b/docs/subsystems/core-host.md
@@ -38,7 +38,7 @@ The server side of the patched `ds-bot` core (`core/`): the part of [ds-bot-core
 | --- | --- |
 | `core/index.js` | Server entry. |
 | `core/src/host/` | Host-side helpers (non-hooks). |
-| `core/src/host/text.js` | The pure text helpers the host modules share: message text, names, model refs, cutting and estimating text, and the clock format of chat anchors. Since #1895 `codePoints(text)` (a step per code point, no array built since #1898) is how the host counts a limit — one character costs one whatever its UTF-16 width — and the bounds this change puts through it are: a memory entry of 300 and a `MEMORY.md` of 4,000 or a topic of 16,000 (the refusal and the size note print the code-point number), a scheduled task's name of 120, a message of 20,000, and the Project memory entry of 600 in both writers, so an emoji is never charged twice. Both cuts land on a code point boundary: `clip` and `excerpt` move back rather than keep half of a surrogate pair, so a clipped emoji reaches a UTF-8 encoder as the character and not as U+FFFD ([#1907](https://github.com/ThinkFlowLab/FlyBot/issues/1907)). Since #1912 that rule is one exported helper rather than a private detail: `cut(text, max)` answers `{ text, cut }` with the longest prefix that stops before a split pair, and the archive writers that used to `slice(0, max)` go through it — the `oneLine` of `decisions.js` and `meetings.js` (into `decisions.jsonl` and `decisions/<date>-<slug>.md`), `claimLine` in `groups.js`, the report cap in `diagnostics.js`, `cleanLabel` in `flybot-feed.js` and `clean` in `browser.js` — so a decision or a meeting record holds the whole character instead of U+FFFD. |
+| `core/src/host/text.js` | The pure text helpers the host modules share: message text, names, model refs, cutting and estimating text, and the clock format of chat anchors. Since #1895 `codePoints(text)` (a step per code point, no array built since #1898) is how the host counts a limit — one character costs one whatever its UTF-16 width — and the bounds this change puts through it are: a memory entry of 300 and a `MEMORY.md` of 4,000 or a topic of 16,000 (the refusal and the size note print the code-point number), a scheduled task's name of 120, a message of 20,000, and the Project memory entry of 600 in both writers, so an emoji is never charged twice. Both cuts land on a code point boundary: `clip` and `excerpt` move back rather than keep half of a surrogate pair, so a clipped emoji reaches a UTF-8 encoder as the character and not as U+FFFD ([#1907](https://github.com/ThinkFlowLab/FlyBot/issues/1907)). Since #1912 that rule is one exported helper rather than a private detail: `cut(text, max)` answers `{ text, cut }` with the longest prefix that stops before a split pair, and the archive writers that used to `slice(0, max)` go through it — the `oneLine` of `decisions.js` and `meetings.js` (into `decisions.jsonl` and `decisions/<date>-<slug>.md`), `claimLine` in `groups.js`, the report cap in `diagnostics.js`, `cleanLabel` in `flybot-feed.js` and `clean` in `browser.js` — so a decision or a meeting record holds the whole character instead of U+FFFD. Since #1916 the boundary rule itself lives in `core/src/shared/text-boundary.js` (`codePointStart`, `codePointEnd`, `cut`), and `host/text.js` builds its `cut` on it so a shared module can bound text too; the eight remaining `slice(0, max)` writers follow it — the claim cue's fallback reference (60), the task lead's name in a member prompt (80), a failed group Session's error text (300), `read_own_chat`'s `query` (80) and `around` (40), the open-page address and title (2000/300), the diagnostics browser-log line and its code (500/40), and `cleanPeerName` in `shared/remote-label.js` (60) — each keeping the longest prefix that stops before a split pair, `length <= max` and a byte prefix of the input. |
 | `core/src/host/prompt.js` | The Bot system prompt; a Main Bot's section is headed `You are the Main Bot` and uses that one term, the one the UI shows (#276). The team rules state the idle default (#699): a Bot does nothing until the user addresses it, it is @-mentioned in a group, its parent gives it a task, or unfinished tasks it was already given are still on its board. It does not invent work. A coordinator acts on a user task rather than on its own initiative — an addressed Bot answers as before. |
 | `core/src/host/room-membership.js` | Typed room participants (human / local bot / granted remote), authorship, membership-window history (#50); rooms with friends' Bots or other owners take granted local Bots only and evict a Bot that stops qualifying (#90). Face-to-face rooms (#83) reuse this model (`origin: 'face-to-face'`, room-only remotes without a person-grant, `upsertFaceRoom` / `syncFaceParticipants` / `applyFaceRoomLine`); a face-room local Bot is `viaCode` (brought by number), `evictUnshared` skips face rooms (membership is the server's), and a Bot that returns to the member list drops the empty local `left` line (#236). Refusing an ungranted local Bot next to a friend's Bot throws `ungrantedRefusal`: a message that names the Bot, the friend and the two ways out, plus `error.details` `{ reason: 'ungranted-local', bots, remotes }`; `channel.js` `fail` forwards a plain-object `details` (empty otherwise) and `client/api.js` puts it on the thrown error, where `client/new-chat.js` draws a card (**Copy invite link for {Bot}** via `__flybot__.social.createInvite`, **Leave {Bot} out**) read through `ungrantedLocalFix` in `shared/remote-label.js`; the same file's `copiedToClipboard` reports whether the invite link really reached the clipboard (none, or a refused write, is `false`), and the card then shows the link to copy by hand instead of saying it was copied. |
 | `core/src/host/face-mentions.js` | Who "@" calls in a face-to-face room (#287): every alias of a participant (`faceAliases`, kept in `shared/remote-label.js` so the bubble chips the same names, #305; bare name, the picker label `<owner>'s Chief` / `<name> · <owner>'s Bot`, `<name> · <owner>`, handle), local and friend's Bots told apart. `faceMentions().handles` is the handle of every Bot a line names (the explicit mention list a sender attaches, #293) and `mentionedByHandle` resolves a received list to my Bots (`known` counts handles the room has). |
@@ -67,7 +67,7 @@ The server side of the patched `ds-bot` core (`core/`): the part of [ds-bot-core
 | `core/src/shared/workflow-run.js` | The running layer's pure half (#1316, #1272 step 4). `planJob({ definition, job, cards, facts, hold })` answers which node cards a job may create now: every decision is `enterNode`'s, so a node whose input is missing, stale or unreadable opens nothing and its refusal is that function's own sentence byte for byte, and a node that already has a card is in neither list — a card parented to another job is not this job's card, so `cardsOfJob` is what makes `(job, node)` one card across a replayed tick or a restarted host, even when a caller hands in the whole board. An open entry is the card the board already places (`parentId` the job card, `workflow`, `node`) plus the fields the pull queue reads (`role`, `queueRole`, `assignee: null`), so the hand-off is the claim and never an `@`. A held job opens nothing on any node, in the definition's own sentence: the planner renders that definition's `no-hold` guard (`pr` equal to `none`, refused for `hold`) through `renderRefusal`, which is the merge gate's wording byte for byte, and a definition guarding no held pull request gets `refusal: null` and the holder's name instead of a sentence this layer wrote. `jobDone` answers pin 6 — a job is done when its terminal node's outputs are present and current, never because a card moved — and `completions` is step (c)'s pure half: a done card whose declared outputs are current, append-only, an entry already in `history` never returned again. No fs, no clock, no timer, no network, no host import: `task-drive.js` `driveOnce` stays the only beat. Tests: `core/test/workflow-run.test.js`. |
 | `core/src/host/workflow-store.js` | Where a definition lives (#1272 step 3): the presets read from their modules plus the owner's `workflows/<id>.json` in the workspace, and the only writer. `save` validates with the engine's own `validateWorkflow` (the roster's roles are the team; an empty roster is no team to check), refuses a preset id (`workflow/preset-read-only` — *Customize* is the only way to start from one), writes `workflow-doc.js`'s bytes only when they changed, and answers `changed: false` for an unedited definition (acceptance 7). `customize`, `setDefault` (the project's `workflows/project.json`), `list`, `open` (definition + bytes + layout + preview) and `definitions()` (the presets plus the workspace files) round it out; `install` wires `rt.workflowEndpoint` for `workflows` (read) and `workflow-save` (write, in `authz.js`'s `TASK_ENDPOINTS`), so the client writes a file through the host and never to GitHub. A file that does not parse is skipped with one warning instead of breaking the list. Tests: `core/test/workflow-store.test.js`. |
 | `core/src/host/workflow-facts.js` | The fact providers (#1272 step 2, acceptance 10): one function per fact a guard asks about — `github.labels`, `github.checkAtSha`, `github.verdictAtTip`, `github.mergeable`, `github.prBodyTip`, `task.progress`, `manual.tick` — each taking the answer a reader already got and returning one artifact (spec, revision, value), never fetching. No `GITHUB_TOKEN`, no answer, or an answer missing the field is `{ ok: false, reason: 'unreadable', why }`, never a guess: a fact nobody could read refuses the node it feeds instead of passing it. `workflowFact(name, args)` is the one spelling for a caller that has the name as data, and an unknown name is unreadable with the name in the reason. Tests: `core/test/workflow-repo-dev.test.js`. |
-| `core/src/shared/remote-label.js` | Owner-badge labels for a friend's Bot and “Shared room from …” titles. `friendBotTitle(bot)` / `friendBotOwner(bot)` name a friend's chat from the roster (`Chief (SelfB1233)`) and its owner (`SelfB1233`, the person an approval card names) with one formatter for every client surface (#498); `friendRecord` reads a published roster record (`roster.remoteBots`, name/owner/home at the top level) as well as a chat's `remote`, so the name does not change when the chat appears (#967). `remoteMentionLabel(record, others)` is the one name a mention wears — that title, and on a title two different handles share the home too (`Chief (Bob) · bob2.home`), so the menu, the bubble, the preview and the host's match cannot drift apart (#967). `remoteBotName` / `isAutoOwnerName` / `seatOwnerName` keep group and face-room labels in that format too (#526): Bot Social's `<Bot> · <owner>` member label is not a Bot name, and an owner name made up from an install id (`FlyBot 682b8a43`) gives way to the username in the home handle (`Reviewer (flybot682b8a43)`). `isListedRemoteChat` / `listedChatBots` keep gone, hidden, and home-level (`@something.home`) remotes out of the **发给** picker, mentions, and `list_bots` friends lines: a share that ended is not a place to send to. The sidebar asks a different question through `isShownRemoteChat` (#956): a chat whose Bot left the published list keeps its row, marked *no longer shared*, while only a hide the user set (`bot.hidden`) takes a row out. History stays on disk either way. |
+| `core/src/shared/remote-label.js` | Owner-badge labels for a friend's Bot and “Shared room from …” titles. `friendBotTitle(bot)` / `friendBotOwner(bot)` name a friend's chat from the roster (`Chief (SelfB1233)`) and its owner (`SelfB1233`, the person an approval card names) with one formatter for every client surface (#498); `friendRecord` reads a published roster record (`roster.remoteBots`, name/owner/home at the top level) as well as a chat's `remote`, so the name does not change when the chat appears (#967). `remoteMentionLabel(record, others)` is the one name a mention wears — that title, and on a title two different handles share the home too (`Chief (Bob) · bob2.home`), so the menu, the bubble, the preview and the host's match cannot drift apart (#967). `remoteBotName` / `isAutoOwnerName` / `seatOwnerName` keep group and face-room labels in that format too (#526): Bot Social's `<Bot> · <owner>` member label is not a Bot name, and an owner name made up from an install id (`FlyBot 682b8a43`) gives way to the username in the home handle (`Reviewer (flybot682b8a43)`). `isListedRemoteChat` / `listedChatBots` keep gone, hidden, and home-level (`@something.home`) remotes out of the **发给** picker, mentions, and `list_bots` friends lines: a share that ended is not a place to send to. The sidebar asks a different question through `isShownRemoteChat` (#956): a chat whose Bot left the published list keeps its row, marked *no longer shared*, while only a hide the user set (`bot.hidden`) takes a row out. History stays on disk either way. Since #1916 `cleanPeerName` bounds a peer name through the shared `cut` (`shared/text-boundary.js`), so a 60-unit label never ends in half of an emoji. |
 
 ## Invariants
 
diff --git a/patches/ds-bot/0001-core-fixes.patch b/patches/ds-bot/0001-core-fixes.patch
index b344ae143..432ff6e67 100644
--- a/patches/ds-bot/0001-core-fixes.patch
+++ b/patches/ds-bot/0001-core-fixes.patch
@@ -4525,7 +4525,21 @@ diff --git a/src/host/diagnostics.js b/src/host/diagnostics.js
      console.error(`[ds-bot] ${line}${frames.length > 0 ? `\n${clean(frames.join('\n'))}` : ''}`)
      note({
        level: 'warn',
-@@ -217,7 +217,7 @@ export function install(rt) {
+@@ -204,7 +204,7 @@ export function install(rt) {
+   }
+ 
+   const sanitizeClient = (client) => {
+-    const pick = (value, max) => (typeof value === 'string' ? clean(value.slice(0, max)) : undefined)
++    const pick = (value, max) => (typeof value === 'string' ? clean(cut(value, max).text) : undefined)
+     return {
+       surface: pick(client?.surface, 40),
+       language: pick(client?.language, 20),
+@@ -213,11 +213,11 @@ export function install(rt) {
+   }
+   const sanitizeClientEntries = list => (Array.isArray(list) ? list : []).slice(-20).flatMap((item) => {
+     if (typeof item?.text !== 'string' || typeof item.time !== 'number') return []
+-    return [{ time: item.time, level: item.level === 'warn' ? 'warn' : 'error', source: 'browser', text: clean(item.text.slice(0, 500)), ...(typeof item.code === 'string' ? { code: clean(item.code.slice(0, 40)) } : {}) }]
++    return [{ time: item.time, level: item.level === 'warn' ? 'warn' : 'error', source: 'browser', text: clean(cut(item.text, 500).text), ...(typeof item.code === 'string' ? { code: clean(cut(item.code, 40).text) } : {}) }]
    })
  
    async function report(body = {}) {
@@ -6292,7 +6306,17 @@ diff --git a/src/host/steward.js b/src/host/steward.js
 diff --git a/src/host/text.js b/src/host/text.js
 --- a/src/host/text.js
 +++ b/src/host/text.js
-@@ -23,11 +23,36 @@ export const unquote = text => String(text ?? '').trim().replace(/^["'“”「
+@@ -1,6 +1,9 @@
+ // Pure text helpers shared by the host modules: message text, names, model refs,
+ // cutting and estimating text, and the clock format of chat anchors.
+ import { COLORS, EXTRA_COLORS, LEGACY_COLORS, OWN_CHAT_LINE_MAX } from './constants.js'
++import { codePointEnd, codePointStart, cut } from '../shared/text-boundary.js'
++
++export { cut }
+ 
+ // A color id saved under its legacy name reads as the current one.
+ export const currentColor = color => (typeof color === 'string' && Object.hasOwn(LEGACY_COLORS, color) ? LEGACY_COLORS[color] : color)
+@@ -23,11 +23,28 @@ export const unquote = text => String(text ?? '').trim().replace(/^["'“”「
  
  export const escapeRegExp = text => text.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
  
@@ -6307,18 +6331,10 @@ diff --git a/src/host/text.js b/src/host/text.js
 +  return n
 +}
 +
-+const isHighSurrogate = code => code >= 0xd800 && code <= 0xdbff
-+const isLowSurrogate = code => code >= 0xdc00 && code <= 0xdfff
-+
-+// A cut moves back onto a code point boundary: half of a surrogate pair reaches a UTF-8 encoder as
-+// U+FFFD, so a clipped emoji would show up as a replacement character at every exit (#1642 for the
-+// client side, here for the host).
-+const codePointStart = (text, at) => (at > 0 && isLowSurrogate(text.charCodeAt(at)) && isHighSurrogate(text.charCodeAt(at - 1)) ? at - 1 : at)
-+const codePointEnd = (text, end) => (end > 0 && isHighSurrogate(text.charCodeAt(end - 1)) && isLowSurrogate(text.charCodeAt(end)) ? end - 1 : end)
-+
-+// A bounded prefix that never splits a surrogate pair (#1912): every other host module cuts its own
-+// archive text, and a half pair is stored as U+FFFD. `cut` says whether anything was dropped.
-+export const cut = (text, max) => ({ text: text.slice(0, codePointEnd(text, max)), cut: text.length > max })
++// A cut moves back onto a code point boundary (#1642 client side, #1912 here, #1916 shared): half of
++// a surrogate pair reaches a UTF-8 encoder as U+FFFD, so a clipped emoji shows up as a replacement
++// character at every exit. The boundary rule itself lives in `shared/text-boundary.js`, because a
++// shared label (`shared/remote-label.js`) bounds a peer name too and must not import this module.
 +
  // The part of a long message around the first match, so a search hit stays visible.
  export const excerpt = (text, wanted, max = OWN_CHAT_LINE_MAX) => {
@@ -9343,8 +9359,12 @@ diff --git a/test/group-status.test.js b/test/group-status.test.js
 diff --git a/test/group-work.test.js b/test/group-work.test.js
 --- a/test/group-work.test.js
 +++ b/test/group-work.test.js
-@@ -6,6 +6,7 @@ import { test } from 'node:test'
- import { apply } from '../index.js'
+@@ -3,9 +3,10 @@ import { mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs'
+ import { tmpdir } from 'node:os'
+ import { join } from 'node:path'
+ import { test } from 'node:test'
+-import { apply } from '../index.js'
++import { createRuntime, provideFlyBot } from '../index.js'
  import { fakeContext } from './fake-ctx.js'
  import { ROOM_LATE_ROUNDS, ROOM_WORK_GRACE_MS } from '../src/host/constants.js'
 +import { compactStatus, prepareRoomLine } from '../src/host/room-context.js'
@@ -9360,7 +9380,7 @@ diff --git a/test/group-work.test.js b/test/group-work.test.js
    const home = mkdtempSync(join(tmpdir(), 'ds-bot-work-'))
    writeFileSync(join(home, 'state.json'), JSON.stringify(seed(room)))
    const ctx = fakeContext()
-@@ -46,14 +46,24 @@ async function start(t, room) {
+@@ -46,21 +46,32 @@ async function start(t, room) {
          },
        }
        const keep = (message) => { calls.push(message); held.push(message) }
@@ -9387,6 +9407,24 @@ diff --git a/test/group-work.test.js b/test/group-work.test.js
      sessionTitle: { rename: async () => {} },
      sessions: { flush: async () => {} },
    })
+   let route
+   const register = ctx.connection.fetch.register
+   ctx.connection.fetch.register = (options) => { route = options; return register(options) }
+-  apply(ctx, { home })
++  const rt = createRuntime(ctx, { home })
++  provideFlyBot(ctx, rt.flybot)
+   t.after(async () => {
+     await ctx.dispose()
+     rmSync(home, { recursive: true, force: true, maxRetries: 5, retryDelay: 20 })
+@@ -105,7 +105,7 @@ async function start(t, room) {
+     return { content: post.content, source: post.source }
+   }
+   await tool('list_bots', {}, 'a')
+-  return { home, agentOf, emit, tool, call, begin, finish, round, say, takePost }
++  return { home, ctx, rt, agentOf, emit, tool, call, begin, finish, round, say, takePost }
+ }
+ 
+ const settle = async (check) => {
 @@ -113,6 +113,7 @@ const settle = async (check) => {
    while (!check() && Date.now() < until) await new Promise(resolve => setImmediate(resolve))
    assert.ok(check(), 'condition not reached')
@@ -9395,7 +9433,7 @@ diff --git a/test/group-work.test.js b/test/group-work.test.js
  const text = message => message.content.map(block => block.text ?? '').join('\n')
  const kinds = result => result.replies.map(reply => [reply.kind ?? 'message', reply.name])
  
-@@ -287,3 +287,205 @@ test('members still at work show in the team view and in the prompts of the othe
+@@ -287,3 +287,254 @@ test('members still at work show in the team view and in the prompts of the othe
    host.finish('gc', '没问题。')
    await settle(() => result() !== undefined)
  })
@@ -9566,6 +9604,55 @@ diff --git a/test/group-work.test.js b/test/group-work.test.js
 +  assert.equal(prepareRoomLine(long), long)
 +})
 +
++// #1916: the lookup line goes into the room log and is also what the search matches, so a bound
++// that lands inside an emoji would store an ill-formed string and make the character unsearchable.
++const utf8Prefix = (whole, part) => Buffer.from(part, 'utf8').equals(Buffer.from(whole, 'utf8').subarray(0, Buffer.byteLength(part)))
++
++test('a read_own_chat query or anchor cut at its bound never splits a surrogate pair (#1916)', async (t) => {
++  const host = await start(t)
++  const log = () => JSON.parse(readFileSync(join(host.home, 'state.json'), 'utf8')).rooms.r1.log
++  const query = `${'a'.repeat(79)}\u{1F600}permalink`
++  await host.tool('read_own_chat', { query }, 'gb')
++  await settle(() => log().length === 1)
++  assert.equal(log()[0].text.isWellFormed(), true)
++  assert.ok(log()[0].text.length <= 80, `query is ${log()[0].text.length} units`)
++  assert.equal(utf8Prefix(query, log()[0].text), true, 'the stored query is a byte prefix of the input')
++  const around = `${'b'.repeat(39)}\u{1F600}anchor`
++  await host.tool('read_own_chat', { around }, 'gb')
++  await settle(() => log().length === 2)
++  assert.equal(log()[1].text.isWellFormed(), true)
++  assert.ok(log()[1].text.length <= `around ${'b'.repeat(39)}`.length, `anchor is ${log()[1].text.length} units`)
++  assert.equal(utf8Prefix(`around ${around}`, log()[1].text), true, 'the stored anchor is a byte prefix of the input')
++})
++
++// #1916: the task lead's name goes into every other member's system prompt, and a Bot name is the
++// owner's to set, emoji included (#1182).
++test('the task lead name in a member prompt never splits a surrogate pair (#1916)', async (t) => {
++  const host = await start(t, { taskLead: 'a' })
++  const name = `${'l'.repeat(79)}\u{1F600}tail`
++  host.rt.state.bots.a.name = name
++  const prompt = host.ctx.sections.get('bot-room').text({ agent: { id: 'gb' } })
++  assert.equal(prompt.isWellFormed(), true, 'the room prompt is well formed')
++  assert.equal(prompt.includes('\uFFFD'), false)
++  assert.ok(prompt.includes('l'.repeat(79)), 'the whole-character prefix is kept')
++})
++
++// #1916: a group Session that cannot be opened reports its error into the room (#1253 notice path),
++// so the 300-unit bound on that text must not land inside an emoji.
++test('a failed group Session reports its error without splitting a surrogate pair (#1916)', async (t) => {
++  const host = await start(t)
++  // No Session for Writer yet: the next round has to open one, and opening it fails.
++  delete host.rt.state.rooms.r1.sessions.b
++  host.ctx.sessionController.create = async () => { throw new Error(`${'e'.repeat(299)}\u{1F600}tail`) }
++  const result = host.round('c1', host.say('@Writer 汇报'))
++  await settle(() => result() !== undefined)
++  const failed = result().replies.find(reply => reply.kind === 'failed')
++  assert.ok(failed, `no failed reply: ${JSON.stringify(result())}`)
++  assert.equal(failed.text.isWellFormed(), true)
++  assert.equal(failed.text.includes('\uFFFD'), false)
++  assert.ok(failed.text.length <= 300, `text is ${failed.text.length} units`)
++})
++
 +// #1906: a search shows its best 20 hits and a bare read the latest 12, and neither said
 +// how much it left out, so a user asking "didn't we decide X?" could think the deciding
 +// message was gone. The caps stay; the answer says what it did not show.
diff --git a/patches/ds-bot/0007-version-and-tooling.patch b/patches/ds-bot/0007-version-and-tooling.patch
index c75e35449..2a97fa96b 100644
--- a/patches/ds-bot/0007-version-and-tooling.patch
+++ b/patches/ds-bot/0007-version-and-tooling.patch
@@ -834,6 +834,30 @@ diff --git a/test/diagnostics.test.js b/test/diagnostics.test.js
    const again = host(home)
    assert.deepEqual((await again.diagnostics.entries()).map(entry => entry.code), ['EACCES', 'RATE_LIMIT'])
    assert.match(await again.diagnostics.logText(), /\n {4}at TestContext/)
+@@ -84,6 +84,23 @@ test('warnings are kept, cleaned, written to the log, and read back after a rest
+   quiet.mock.restore()
+ })
+ 
++// #1916: the browser-log lines in the report are bounded, and those bounds are code-unit ones:
++// a line cut inside an emoji is stored and shown as U+FFFD in a report meant for a public issue.
++test('a browser-log line cut at its bound never splits a surrogate pair (#1916)', async (t) => {
++  const home = mkdtempSync(join(tmpdir(), 'ds-bot-diag-'))
++  t.after(() => rmSync(home, { recursive: true, force: true, maxRetries: 5 }))
++  const rt = host(home, { config: { diagnosticsFile: false } })
++  const report = await rt.diagnostics.report({
++    clientErrors: [{ time: 1, text: `${'x'.repeat(499)}\u{1F600}tail`, code: `${'y'.repeat(39)}\u{1F600}tail` }],
++  })
++  const line = report.markdown.split('\n').find(item => item.includes('ERROR browser')) ?? ''
++  assert.notEqual(line, '')
++  assert.equal(line.isWellFormed(), true)
++  assert.equal(line.includes('\ufffd'), false)
++  assert.ok(line.includes('x'.repeat(499)), 'the text keeps its whole-character prefix')
++  assert.ok(line.includes(`[${'y'.repeat(39)}]`), `expected the code prefix, got ${line}`)
++})
++
+ test('warnings send only cleaned text to the logger and stderr', (t) => {
+   const home = mkdtempSync(join(tmpdir(), 'ds-bot-diag-'))
+   t.after(() => rmSync(home, { recursive: true, force: true, maxRetries: 5 }))
 @@ -108,6 +108,23 @@ test('warnings send only cleaned text to the logger and stderr', (t) => {
    }
  })
diff --git a/patches/ds-bot/0008-client-bundle.patch b/patches/ds-bot/0008-client-bundle.patch
index d15f8c9d2..65836960a 100644
--- a/patches/ds-bot/0008-client-bundle.patch
+++ b/patches/ds-bot/0008-client-bundle.patch
@@ -1104,14 +1104,22 @@ diff --git a/client.js b/client.js
      if (!REFUSALS.has(code)) {
        noteClientError(endpoint, Object.assign(new Error(result.error?.message ?? "Request failed"), { code }));
        markNoted(error);
-@@ -1097,6 +1097,388 @@ var call = async (endpoint, payload, signal) => {
+@@ -1097,6 +1097,396 @@ var call = async (endpoint, payload, signal) => {
    return result.value;
  };
  
++// src/shared/text-boundary.js
++var isHighSurrogate = (code) => code >= 55296 && code <= 56319;
++var isLowSurrogate = (code) => code >= 56320 && code <= 57343;
++var codePointStart = (text2, at) => at > 0 && isLowSurrogate(text2.charCodeAt(at)) && isHighSurrogate(text2.charCodeAt(at - 1)) ? at - 1 : at;
++var codePointEnd = (text2, end) => end > 0 && isHighSurrogate(text2.charCodeAt(end - 1)) && isLowSurrogate(text2.charCodeAt(end)) ? end - 1 : end;
++var cut = (text2, max) => ({ text: text2.slice(0, codePointEnd(text2, max)), cut: text2.length > max });
++
 +// src/shared/remote-label.js
 +function cleanPeerName(name, fallback = "") {
-+  const text2 = String(name ?? "").replace(/[\u0000-\u001f\u007f-\u009f\u2028\u2029]/g, " ").replace(/[[\]"`<>]/g, "").replace(/\s+/g, " ").trim().slice(0, 60);
-+  return text2 || fallback;
++  const text2 = String(name ?? "").replace(/[\u0000-\u001f\u007f-\u009f\u2028\u2029]/g, " ").replace(/[[\]"`<>]/g, "").replace(/\s+/g, " ").trim();
++  const label = cut(text2, 60).text;
++  return label || fallback;
 +}
 +function normRemoteHandle(handle) {
 +  return `@${String(handle ?? "").trim().replace(/^@+/, "").toLowerCase()}`;
@@ -1760,16 +1768,7 @@ diff --git a/client.js b/client.js
 -    else delete SHAPES[id];
 -    refresh();
 -  };
-+// src/client/cluster-order.js
-+function clusterOrder(people2) {
-+  const list = Array.isArray(people2) ? people2 : [];
-+  const remote = (bot) => Boolean(bot?.remote);
-+  if (!list.some(remote)) return list;
-+  const locals = list.filter((bot) => !remote(bot));
-+  const remotes = list.filter(remote);
-+  if (list.length <= 4) return [...remotes, ...locals];
-+  return [...locals, ...remotes];
- }
+-}
 -function registerTheme(id, theme) {
 -  if (typeof id !== "string" || !/^[a-z][\w-]{0,31}$/.test(id)) throw new Error("Theme ids are lowercase words");
 -  for (const mode of ["light", "dark"]) {
@@ -1783,7 +1782,16 @@ diff --git a/client.js b/client.js
 -    else delete customThemes[id];
 -    registry.set((value) => value + 1);
 -  };
--}
++// src/client/cluster-order.js
++function clusterOrder(people2) {
++  const list = Array.isArray(people2) ? people2 : [];
++  const remote = (bot) => Boolean(bot?.remote);
++  if (!list.some(remote)) return list;
++  const locals = list.filter((bot) => !remote(bot));
++  const remotes = list.filter(remote);
++  if (list.length <= 4) return [...remotes, ...locals];
++  return [...locals, ...remotes];
+ }
 -var allThemes = () => ({ ...THEMES, ...customThemes });
  
  // src/shared/mentions.js
@@ -1834,9 +1842,6 @@ diff --git a/client.js b/client.js
  }
 -
 -// src/client/text.js
--var MENTION_ORIGIN = "https://bots.local/";
--function linkMentions(text, bots, selfId) {
--  if (!text || !text.includes("@")) return text;
 +function unmatchedMentions(text2, bots, { references = [] } = {}) {
 +  const value = String(text2 ?? "");
 +  const skip = [
@@ -1886,7 +1891,9 @@ diff --git a/client.js b/client.js
 +}
 +
 +// src/client/text.js
-+var MENTION_ORIGIN = "https://bots.local/";
+ var MENTION_ORIGIN = "https://bots.local/";
+-function linkMentions(text, bots, selfId) {
+-  if (!text || !text.includes("@")) return text;
 +function linkMentions(text2, bots, selfId) {
 +  if (!text2 || !text2.includes("@")) return text2;
 +  const ordered = [...bots ?? []].sort((a, b) => Number(Boolean(a?.remote)) - Number(Boolean(b?.remote)));
@@ -2124,7 +2131,7 @@ diff --git a/client.js b/client.js
  var formatTokens = (count) => count >= 1e6 ? `${(count / 1e6).toFixed(1)}M` : count >= 1e3 ? `${(count / 1e3).toFixed(1)}K` : String(count);
  function usageOf(list, ids) {
    let input = 0;
-@@ -1624,901 +1624,1981 @@ function usageOf(list, ids) {
+@@ -1624,902 +1624,1982 @@ function usageOf(list, ids) {
    const hit = input > 0 ? Math.round(cacheRead / input * 100) : 0;
    return t("{tokens} tok · Cache hit {hit}%", { tokens: formatTokens(input + output), hit });
  }
@@ -3969,6 +3976,7 @@ diff --git a/client.js b/client.js
 -.bt-mem-summary>:nth-child(5){animation-delay:.12s}
 -.bt-mem-summary>:nth-child(6){animation-delay:.15s}
 -.bt-mem-summary>:nth-child(n+7){animation-delay:.18s}
+-@keyframes bt-mem-line{from{opacity:0;transform:translateY(4px)}}
 +// src/client/motion.js
 +var import_react4 = require("react");
 +var reducedMotion = () => window.matchMedia?.("(prefers-reduced-motion: reduce)").matches === true;
@@ -4970,9 +4978,10 @@ diff --git a/client.js b/client.js
 +.bt-mem-summary>:nth-child(5){animation-delay:.12s}
 +.bt-mem-summary>:nth-child(6){animation-delay:.15s}
 +.bt-mem-summary>:nth-child(n+7){animation-delay:.18s}
- @keyframes bt-mem-line{from{opacity:0;transform:translateY(4px)}}
++@keyframes bt-mem-line{from{opacity:0;transform:translateY(4px)}}
  .bt-mem-skel{display:flex;flex-direction:column;gap:24px}
  .bt-mem-skel-block{display:flex;flex-direction:column;gap:10px}
+ .bt-mem-skel-block span{display:block;height:12px;border-radius:6px;background:linear-gradient(90deg,var(--bt-hover) 25%,var(--bt-active) 50%,var(--bt-hover) 75%);background-size:200% 100%;animation:bt-mem-skel 1.4s ease-in-out infinite}
 @@ -2574,2206 +2574,4679 @@ body[data-ds-dark-theme] .bt-theme-chip i{background:var(--da)}
  @media (max-width:640px){.bt-mem{width:100vw;height:100%;border-radius:0;border:0}.bt-mem-body{padding:18px 18px 20px}.bt-mem-foot{padding:8px 12px 12px}}
  @media (prefers-reduced-motion:reduce){.bt-mem,.bt-mem-scrim,.bt-mem-summary>*,.bt-mem-empty,.bt-mem-reply,.bt-mem-skel-block span,.bt-mem-entries,.bt-mem-send>*,.bt-mem-changes li svg{animation:none}}
diff --git a/patches/ds-bot/0012-room-membership.patch b/patches/ds-bot/0012-room-membership.patch
index e2bf5473a..07fd125d7 100644
--- a/patches/ds-bot/0012-room-membership.patch
+++ b/patches/ds-bot/0012-room-membership.patch
@@ -884,7 +884,7 @@ diff --git a/src/host/groups.js b/src/host/groups.js
 +  const title = claimLine(task?.title, 300)
 +  if (title === '') return ''
 +  const found = title.match(/^#(\d{1,7})\b/) ?? title.match(/#(\d{1,7})\b/)
-+  const ref = found ? `#${found[1]}` : title.slice(0, CLAIM_CUE_REF_MAX)
++  const ref = found ? `#${found[1]}` : cut(title, CLAIM_CUE_REF_MAX).text
 +  const rest = found ? title.slice(title.indexOf(found[0]) + found[0].length).trim() : ''
 +  const step = claimLine(task?.note, CLAIM_CUE_STEP_MAX) || claimLine(rest, CLAIM_CUE_STEP_MAX)
 +  return step === '' ? `接了 ${ref}` : `接了 ${ref}，第一步是 ${step}`
@@ -1153,7 +1153,7 @@ diff --git a/src/host/groups.js b/src/host/groups.js
 -    await rt.save()
 -    await rt.ensureCapabilities(id)
 -    return { id, brief: await rt.ownChatBrief(member) }
-+    const name = String(rt.botOf(leadId)?.name ?? 'The task lead').replace(/[\r\n]+/g, ' ').slice(0, 80)
++    const name = cut(String(rt.botOf(leadId)?.name ?? 'The task lead').replace(/[\r\n]+/g, ' '), 80).text
 +    return `${name} is this room's task lead (总负责人) for the board: it assigns the parts on the board. Claim the card it assigns you by setting its column to in-progress with track_tasks, and update that card's column and progress as the work moves. Do not record a new plan, assign work, or post a status in the group. @Name only wakes someone; it does not assign. Start the work in your own chat; do not wait for a confirmation. A question a person has to decide is one short post in this group; do not @ a Bot to hand the work on.`
    }
  
@@ -1603,7 +1603,14 @@ diff --git a/src/host/groups.js b/src/host/groups.js
        slot.status = 'speaking'
        round.speaking = member.id
        round.turns += 1
-@@ -339,8 +339,23 @@ export function install(rt) {
+@@ -333,14 +333,29 @@ export function install(rt) {
+         round.speaking = null
+         slot.status = 'failed'
+         round.failed.push(member.name)
+-        round.replies.push({ kind: 'failed', botId: member.id, name: member.name, color: member.color, code: 'SESSION', text: String(error?.message ?? error).slice(0, 300), time: Date.now() })
++        round.replies.push({ kind: 'failed', botId: member.id, name: member.name, color: member.color, code: 'SESSION', text: cut(String(error?.message ?? error), 300).text, time: Date.now() })
+         continue
+       }
        const prompt = roomPrompt(room, member, round)
        round.shown?.push(member.id)
        const text = session.brief === undefined ? prompt : `${session.brief}\n\n${prompt}`
@@ -1814,6 +1821,17 @@ diff --git a/src/host/groups.js b/src/host/groups.js
    // Private context enters a group only through this tool, and the group sees each use.
    ctx.tools.register(defineTool({
      name: 'read_own_chat',
+@@ -489,8 +489,8 @@ export function install(rt) {
+       if (botId === undefined) return 'Only Bots on the team can use read_own_chat.'
+       const member = rt.botOf(botId)
+       const room = rt.roomOf(owner?.roomId)
+-      const query = String(args.query ?? '').trim().slice(0, 80)
+-      const around = String(args.around ?? '').trim().slice(0, 40)
++      const query = cut(String(args.query ?? '').trim(), 80).text
++      const around = cut(String(args.around ?? '').trim(), 40).text
+       const parts = rt.partsOf(botId)
+       const number = Number.isInteger(args.part) ? args.part : undefined
+       if (room !== undefined && member !== undefined) {
 @@ -517,13 +517,17 @@ export function install(rt) {
          return `Part ${number} of your own chat (${rt.clock(part.startedAt)} – ${rt.clock(part.endedAt)}). The handoff note that closed it:\n${rt.noteText(part) ?? '(none: the part ended on a context overflow)'}${partsNote}`
        }
diff --git a/patches/ds-bot/0014-flybot-branding.patch b/patches/ds-bot/0014-flybot-branding.patch
index 06a38abcc..269102a91 100644
--- a/patches/ds-bot/0014-flybot-branding.patch
+++ b/patches/ds-bot/0014-flybot-branding.patch
@@ -551,6 +551,15 @@ diff --git a/src/host/browser.js b/src/host/browser.js
  
  /**
   * Where a part of the text that starts at `start` ends: at a blank line, else a line break,
+@@ -250,7 +250,7 @@ export function install(rt) {
+     if (value === null || typeof value !== 'object') return open
+     for (const [botId, page] of Object.entries(value).slice(0, OPEN_MAX)) {
+       if (rt.botOf(botId) === undefined || typeof page?.url !== 'string') continue
+-      open[botId] = { url: page.url.slice(0, 2000), title: String(page.title ?? '').slice(0, 300) }
++      open[botId] = { url: cut(page.url, 2000).text, title: cut(String(page.title ?? ''), 300).text }
+     }
+     return open
+   }
 diff --git a/src/host/dsh-update.js b/src/host/dsh-update.js
 --- a/src/host/dsh-update.js
 +++ b/src/host/dsh-update.js
@@ -1647,6 +1656,45 @@ diff --git a/src/host/update.js b/src/host/update.js
      const service = manager()
      if (typeof service?.installBundle !== 'function') throw new Error('The DSH plugin manager is not available in this profile')
      const chosen = target
+diff --git a/test/browser-channel.test.js b/test/browser-channel.test.js
+--- a/test/browser-channel.test.js
++++ b/test/browser-channel.test.js
+@@ -1,6 +1,6 @@
+ import { test } from 'node:test'
+ import assert from 'node:assert/strict'
+-import { createBrowserChannel, pageText, partEnd } from '../src/host/browser.js'
++import { createBrowserChannel, install, pageText, partEnd } from '../src/host/browser.js'
+ 
+ const ids = items => items.map(item => item.id)
+ 
+@@ -141,3 +141,27 @@ test('partEnd prefers a blank line, then a line break, and cuts hard only withou
+   assert.equal(partEnd('a\n' + 'b'.repeat(20), 0, 10), 10)
+   assert.equal(partEnd('short', 0, 10), 5)
+ })
++
++// #1916: the open-page snapshot is what a Bot reads back from outside the team, and both bounds
++// are code-unit ones: 2000 for an address and 300 for a title must not land inside an emoji.
++test('the open-page snapshot never cuts a title or an address in half (#1916)', () => {
++  const registered = []
++  const rt = {
++    ctx: { get: () => ({ name: 'desktop' }), effect: () => {}, tools: { register: (tool) => registered.push(tool) } },
++    config: {},
++    botOf: () => ({ id: 'a' }),
++  }
++  install(rt)
++  const open = rt.browserOpen({
++    a: { url: `${'a'.repeat(1999)}\u{1F600}tail`, title: `${'b'.repeat(299)}\u{1F600}tail` },
++  })
++  assert.equal(open.a.url.isWellFormed(), true)
++  assert.equal(open.a.title.isWellFormed(), true)
++  assert.equal(open.a.url, 'a'.repeat(1999))
++  assert.equal(open.a.title, 'b'.repeat(299))
++  // A cut that lands on a whole character keeps it.
++  const roomy = rt.browserOpen({ a: { url: `${'a'.repeat(1998)}\u{1F600}`, title: `${'b'.repeat(298)}\u{1F600}` } })
++  assert.equal(roomy.a.url, `${'a'.repeat(1998)}\u{1F600}`)
++  assert.equal(roomy.a.title, `${'b'.repeat(298)}\u{1F600}`)
++  assert.equal(registered.length > 0, true)
++})
 diff --git a/test/capabilities.test.js b/test/capabilities.test.js
 --- a/test/capabilities.test.js
 +++ b/test/capabilities.test.js
diff --git a/patches/ds-bot/files/src/shared/remote-label.js b/patches/ds-bot/files/src/shared/remote-label.js
index 7312732e0..f229208c2 100644
--- a/patches/ds-bot/files/src/shared/remote-label.js
+++ b/patches/ds-bot/files/src/shared/remote-label.js
@@ -1,10 +1,12 @@
 // Display labels for a friend's published Bot and for a room the owner did not start.
 // Peer-controlled strings (names, homes, handles) are untrusted: strip controls and
 // markup so a name cannot look like instructions when it later reaches a model.
+import { cut } from './text-boundary.js'
 
 export function cleanPeerName(name, fallback = '') {
-  const text = String(name ?? '').replace(/[\u0000-\u001f\u007f-\u009f\u2028\u2029]/g, ' ').replace(/[[\]"`<>]/g, '').replace(/\s+/g, ' ').trim().slice(0, 60)
-  return text || fallback
+  const text = String(name ?? '').replace(/[\u0000-\u001f\u007f-\u009f\u2028\u2029]/g, ' ').replace(/[[\]"`<>]/g, '').replace(/\s+/g, ' ').trim()
+  const label = cut(text, 60).text
+  return label || fallback
 }
 
 export function normRemoteHandle(handle) {
diff --git a/patches/ds-bot/files/src/shared/text-boundary.js b/patches/ds-bot/files/src/shared/text-boundary.js
new file mode 100644
index 000000000..af6579e24
--- /dev/null
+++ b/patches/ds-bot/files/src/shared/text-boundary.js
@@ -0,0 +1,16 @@
+// Where a bounded prefix may end. Both sides bound text (#1908/#1912/#1916): the host cuts what a
+// Bot reads back and what it stores, and a shared label cuts a peer's name. A cut that lands between
+// the halves of a surrogate pair reaches a UTF-8 encoder as U+FFFD, so every bound goes through here
+// instead of `slice`, and `host/text.js` builds its `cut` on this one implementation.
+
+const isHighSurrogate = code => code >= 0xd800 && code <= 0xdbff
+const isLowSurrogate = code => code >= 0xdc00 && code <= 0xdfff
+
+// The start of a bounded window, moved back onto a code point boundary.
+export const codePointStart = (text, at) => (at > 0 && isLowSurrogate(text.charCodeAt(at)) && isHighSurrogate(text.charCodeAt(at - 1)) ? at - 1 : at)
+
+// The end of a bounded prefix, moved back onto a code point boundary.
+export const codePointEnd = (text, end) => (end > 0 && isHighSurrogate(text.charCodeAt(end - 1)) && isLowSurrogate(text.charCodeAt(end)) ? end - 1 : end)
+
+// A bounded prefix that never splits a surrogate pair. `cut` says whether anything was dropped.
+export const cut = (text, max) => ({ text: text.slice(0, codePointEnd(text, max)), cut: text.length > max })
diff --git a/patches/ds-bot/files/test/claim-cue.test.js b/patches/ds-bot/files/test/claim-cue.test.js
index 0aa31cf61..feabe4a11 100644
--- a/patches/ds-bot/files/test/claim-cue.test.js
+++ b/patches/ds-bot/files/test/claim-cue.test.js
@@ -10,7 +10,7 @@ import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { test } from 'node:test'
 import { createRuntime } from '../index.js'
-import { CLAIM_CUE_REPEAT_MS } from '../src/host/groups.js'
+import { CLAIM_CUE_REPEAT_MS, claimCueText } from '../src/host/groups.js'
 import { fakeContext } from './fake-ctx.js'
 
 const team = () => ({
@@ -180,3 +180,20 @@ test('a claim outside a room posts no line (#1253)', async (t) => {
 test('the repeat window is a stated number of minutes, not forever (#1253)', () => {
   assert.equal(CLAIM_CUE_REPEAT_MS, 30 * 60 * 1000)
 })
+
+// #1916: the reference of a title with no issue number is a bounded prefix, and the bound is a
+// code-unit one: 60 must not land between the halves of an emoji, or the room notice and the
+// room log both keep an ill-formed string.
+const utf8Prefix = (whole, part) => Buffer.from(part, 'utf8').equals(Buffer.from(whole, 'utf8').subarray(0, Buffer.byteLength(part)))
+
+test('a claim cue reference cut at 60 never splits a surrogate pair (#1916)', () => {
+  const title = `${'a'.repeat(59)}\u{1F600}tail`
+  const ref = claimCueText({ title }).replace(/^接了 /, '')
+  assert.equal(ref.isWellFormed(), true)
+  assert.equal(ref.includes('\uFFFD'), false)
+  assert.ok(ref.length <= 60, `ref is ${ref.length} units`)
+  assert.equal(utf8Prefix(title, ref), true, 'the ref is a byte prefix of the title')
+  // A cut that lands on a whole character keeps the whole character.
+  const roomy = claimCueText({ title: `${'a'.repeat(58)}\u{1F600}tail` }).replace(/^接了 /, '')
+  assert.equal(roomy, `${'a'.repeat(58)}\u{1F600}`)
+})
diff --git a/patches/ds-bot/files/test/group-bot-label.test.js b/patches/ds-bot/files/test/group-bot-label.test.js
index 08ae245fd..f9c37ff94 100644
--- a/patches/ds-bot/files/test/group-bot-label.test.js
+++ b/patches/ds-bot/files/test/group-bot-label.test.js
@@ -117,3 +117,11 @@ test('#526: real names stay as they are', () => {
   const view = roster([seatMine, { ...reviewer, label: undefined }], 'group')
   assert.equal(remoteSpeaker({ remote: { handle }, senderName: 'Reviewer' }, view, 'r').name, 'Reviewer (flybot682b8a43)')
 })
+
+// #1916: a friend's Bot or room name reaches a display label, and its 60-unit bound must not land
+// inside an emoji: the half pair would show as U+FFFD wherever the label is drawn.
+test('a peer name cut at 60 never splits a surrogate pair (#1916)', () => {
+  assert.equal(labels.cleanPeerName(`${'b'.repeat(59)}\u{1F600}tail`), 'b'.repeat(59))
+  assert.equal(labels.cleanPeerName(`${'b'.repeat(58)}\u{1F600}tail`), `${'b'.repeat(58)}\u{1F600}`)
+  assert.equal(labels.cleanPeerName(`${'b'.repeat(59)}\u{1F600}tail`, 'fallback').isWellFormed(), true)
+})
diff --git a/patches/ds-bot/topics.json b/patches/ds-bot/topics.json
index 705dba5c6..73290f013 100644
--- a/patches/ds-bot/topics.json
+++ b/patches/ds-bot/topics.json
@@ -142,7 +142,8 @@
     "test/dsh-update.test.js",
     "test/store.test.js",
     "test/secrets.test.js",
-    "test/capabilities.test.js"
+    "test/capabilities.test.js",
+    "test/browser-channel.test.js"
   ],
   "0016-room-collaboration-smoke": [
     "dev/mock-llm.mjs"