From 1987f486bb82779da6f85f37503256c6314d7fab Mon Sep 17 00:00:00 2001
From: Day Dreamer <87640074+HugoXK@users.noreply.github.com>
Date: Sat, 31 Oct 2026 19:05:43 +0800
Subject: [PATCH] roster: cut a Bot's name and role on a code point boundary

A Bot's name is bounded at 40 units and its role at 24, both with `slice`, so a
name or role whose bound falls between the halves of a surrogate pair is stored
as half of one: the sidebar row, the session title and the store's JSON then
carry U+FFFD where the user typed a character. Both bounds now go through the
host `cut`, the same helper the other bounded fields use since #1916, so the
prefix stops before a split pair.

Docs-not-needed: no subsystem page states the roster's name or role bound, and
both keep their 40/24 limit; only the unit the prefix stops on changes.
---
 core/src/host/roster.js                   | 10 ++---
 core/test/roster.test.js                  | 32 +++++++++++++++
 patches/ds-bot/0002-flybot-api-host.patch | 44 ++++++++++++++++----
 patches/ds-bot/0009-identity-schema.patch | 49 +++++++++++++++++++----
 4 files changed, 114 insertions(+), 21 deletions(-)

diff --git a/core/src/host/roster.js b/core/src/host/roster.js
index 89d9fdceb..b1aae17f5 100644
--- a/core/src/host/roster.js
+++ b/core/src/host/roster.js
@@ -3,7 +3,7 @@
 import { mkdir } from 'node:fs/promises'
 import { join } from 'node:path'
 import { MAX_AVATAR_IMAGE, ROOM_MAX_MEMBERS, ROOM_MODES, ROOM_NAME_MAX, ROOM_NOTICE_MAX } from './constants.js'
-import { currentColor, isColor, unquote } from './text.js'
+import { currentColor, cut, isColor, unquote } from './text.js'
 import { nameProblem } from '../shared/mentions.js'
 import { cleanExternal } from './room-participant-external.js'
 import { ownEntry } from './store.js'
@@ -61,7 +61,7 @@ export function install(rt) {
   // `pickModel` leaves the model to the user: the chat opens on a model card. So does a
   // Bot made when no model is served.
   async function createBot({ name: botName, role = '', instructions = '', color, brief = '', createdBy, main = false, avatar, model, effort, workDir, pickModel = false, systemPrompt, fields, remote, external, ownerId: explicitOwnerId, hidden, ephemeral }) {
-    const cleanName = String(botName ?? '').trim().slice(0, 40)
+    const cleanName = cut(String(botName ?? '').trim(), 40).text
     // A friend's Bot (remote-chat.js) keeps its own name: it is not a team member, so
     // team names never clash with it and creating it starts no turn.
     const isRemote = typeof remote?.handle === 'string'
@@ -106,7 +106,7 @@ export function install(rt) {
       state.bots[id] = {
         id,
         name: cleanName,
-        role: String(role).trim().slice(0, 24),
+        role: cut(String(role).trim(), 24).text,
         // A color is only stored when the user picks one; otherwise the id picks it.
         ...(isColor(currentColor(color)) ? { color: currentColor(color) } : {}),
         ...(cleanAvatarValue ? { avatar: cleanAvatarValue } : {}),
@@ -189,7 +189,7 @@ export function install(rt) {
     const moving = patch.workDir !== undefined
     const workDir = moving ? await rt.cleanWorkDir(patch.workDir ?? '') : undefined
     if (patch.name !== undefined) {
-      const next = String(patch.name).trim().slice(0, 40)
+      const next = cut(String(patch.name).trim(), 40).text
       const clash = rt.findBot(next)
       if (next === '' || (clash && clash.id !== id)) throw new Error(`Name ${next} is not available`)
       // A name saved before the rule stays usable until it changes.
@@ -200,7 +200,7 @@ export function install(rt) {
       await ctx.sessionTitle.rename(agent.session, next)
       await followMemberNames(Object.values(state.rooms).filter(room => room.members.includes(id)))
     }
-    if (patch.role !== undefined) bot.role = String(patch.role).trim().slice(0, 24)
+    if (patch.role !== undefined) bot.role = cut(String(patch.role).trim(), 24).text
     if (patch.instructions !== undefined) bot.instructions = String(patch.instructions).trim()
     let modelChanged = false
     if (patch.color !== undefined) {
diff --git a/core/test/roster.test.js b/core/test/roster.test.js
index 1df44b24f..8eaf39509 100644
--- a/core/test/roster.test.js
+++ b/core/test/roster.test.js
@@ -144,6 +144,15 @@ test('a Bot made by the Main Bot starts on the Main Bot\'s model and level befor
   assert.equal(typed.model, 'deepseek/deepseek-v4-flash')
 })
 
+// P-275: a Bot's name is bounded at 40 and its role at 24, and both bounds cut UTF-16 units.
+// A bound that lands inside an emoji stores half of a surrogate pair, so the sidebar, the
+// session title and the store's JSON carry U+FFFD instead of the character.
+const bounded = (actual, source, max) => {
+  assert.ok(actual.length <= max, `${actual.length} code units, over ${max}`)
+  assert.equal(actual.isWellFormed(), true, `not well formed: ${actual}`)
+  assert.equal(Buffer.from(actual, 'utf8').equals(Buffer.from(source, 'utf8').subarray(0, Buffer.byteLength(actual))), true, 'the value is a UTF-8 byte prefix of what was typed')
+}
+
 test('a new name must be one "@" can call; a name saved before the rule still saves', async (t) => {
   const { call, stop } = start(undefined, { models: ['deepseek-v4-flash'] })
   t.after(stop)
@@ -154,6 +163,29 @@ test('a new name must be one "@" can call; a name saved before the rule still sa
   assert.equal((await call('update-bot', { id: writer.id, name: '新 Writer' })).ok, true)
 })
 
+test('a name and a role stop their bound before a split surrogate pair', async (t) => {
+  const { call, stop } = start(undefined, { models: ['deepseek-v4-flash'] })
+  t.after(stop)
+  await call('state', {})
+  const name = `${'a'.repeat(39)}\u{1F600}tail`
+  const role = `${'b'.repeat(23)}\u{1F600}tail`
+  const writer = (await call('create-bot', { name, role })).value
+  assert.equal(writer.name, 'a'.repeat(39), 'the bound retracts one unit instead of splitting the pair')
+  bounded(writer.name, name, 40)
+  assert.equal(writer.role, 'b'.repeat(23))
+  bounded(writer.role, role, 24)
+  // A rename and a role edit take the same two bounds.
+  const renamed = `${'c'.repeat(39)}\u{1F600}tail`
+  const reRole = `${'d'.repeat(23)}\u{1F600}tail`
+  assert.equal((await call('update-bot', { id: writer.id, name: renamed })).ok, true)
+  assert.equal((await call('update-bot', { id: writer.id, role: reRole })).ok, true)
+  const saved = (await call('state', {})).value.bots.find(entry => entry.id === writer.id)
+  assert.equal(saved.name, 'c'.repeat(39))
+  bounded(saved.name, renamed, 40)
+  assert.equal(saved.role, 'd'.repeat(23))
+  bounded(saved.role, reRole, 24)
+})
+
 // Creation is silent (#645): no path that makes a Bot opens a turn, and only a brief from a
 // Bot that creates one (`create_bot`) becomes instructions. A line typed in the new-Bot card
 // is the user's first request, sent as a turn by the client, never a standing rule.
diff --git a/patches/ds-bot/0002-flybot-api-host.patch b/patches/ds-bot/0002-flybot-api-host.patch
index fd32e5d5f..f83d7ce56 100644
--- a/patches/ds-bot/0002-flybot-api-host.patch
+++ b/patches/ds-bot/0002-flybot-api-host.patch
@@ -154,9 +154,12 @@ diff --git a/src/host/home-lock.js b/src/host/home-lock.js
 diff --git a/src/host/roster.js b/src/host/roster.js
 --- a/src/host/roster.js
 +++ b/src/host/roster.js
-@@ -5,6 +5,8 @@ import { join } from 'node:path'
+@@ -3,8 +3,10 @@
+ import { mkdir } from 'node:fs/promises'
+ import { join } from 'node:path'
  import { MAX_AVATAR_IMAGE, ROOM_MAX_MEMBERS, ROOM_MODES, ROOM_NAME_MAX, ROOM_NOTICE_MAX } from './constants.js'
- import { currentColor, isColor, unquote } from './text.js'
+-import { currentColor, isColor, unquote } from './text.js'
++import { currentColor, cut, isColor, unquote } from './text.js'
  import { nameProblem } from '../shared/mentions.js'
 +import { cleanExternal } from './room-participant-external.js'
 +import { ownEntry } from './store.js'
@@ -172,20 +175,21 @@ diff --git a/src/host/roster.js b/src/host/roster.js
      state.workspaceId = workspace.id
      await rt.save()
      return workspace.id
-@@ -56,18 +56,49 @@ export function install(rt) {
+@@ -56,69 +56,103 @@ export function install(rt) {
      return `${stem} ${index}`
    }
  
 -  // `pickModel` leaves the model to the user: the chat opens on a model card, and the
 -  // greeting waits until a model is chosen. So does a Bot made when no model is served.
 -  async function createBot({ name: botName, role = '', instructions = '', color, brief = '', createdBy, main = false, avatar, model, effort, workDir, copyOf, pickModel = false }) {
-+  // `pickModel` leaves the model to the user: the chat opens on a model card. So does a
-+  // Bot made when no model is served.
-+  async function createBot({ name: botName, role = '', instructions = '', color, brief = '', createdBy, main = false, avatar, model, effort, workDir, pickModel = false, systemPrompt, fields, remote, external, ownerId: explicitOwnerId, hidden, ephemeral }) {
-     const cleanName = String(botName ?? '').trim().slice(0, 40)
+-    const cleanName = String(botName ?? '').trim().slice(0, 40)
 -    const problem = nameProblem(cleanName)
 -    if (problem !== undefined) throw new Error(problem)
 -    if (rt.findBot(cleanName)) throw new Error(`A Bot named ${cleanName} already exists`)
++  // `pickModel` leaves the model to the user: the chat opens on a model card. So does a
++  // Bot made when no model is served.
++  async function createBot({ name: botName, role = '', instructions = '', color, brief = '', createdBy, main = false, avatar, model, effort, workDir, pickModel = false, systemPrompt, fields, remote, external, ownerId: explicitOwnerId, hidden, ephemeral }) {
++    const cleanName = cut(String(botName ?? '').trim(), 40).text
 +    // A friend's Bot (remote-chat.js) keeps its own name: it is not a team member, so
 +    // team names never clash with it and creating it starts no turn.
 +    const isRemote = typeof remote?.handle === 'string'
@@ -230,7 +234,13 @@ diff --git a/src/host/roster.js b/src/host/roster.js
      const id = await createSession(cleanName, { dir })
      try {
        state.bots[id] = {
-@@ -80,45 +80,48 @@ export function install(rt) {
+         id,
+         name: cleanName,
+-        role: String(role).trim().slice(0, 24),
++        role: cut(String(role).trim(), 24).text,
+         // A color is only stored when the user picks one; otherwise the id picks it.
+         ...(isColor(currentColor(color)) ? { color: currentColor(color) } : {}),
+         ...(cleanAvatarValue ? { avatar: cleanAvatarValue } : {}),
          ...(modelRef ? { model: modelRef } : {}),
          ...(effortId ? { effort: effortId } : {}),
          ...(dir ? { workDir: dir } : {}),
@@ -338,6 +348,24 @@ diff --git a/src/host/roster.js b/src/host/roster.js
      })
    }
  
+@@ -166,7 +166,7 @@ export function install(rt) {
+     const moving = patch.workDir !== undefined
+     const workDir = moving ? await rt.cleanWorkDir(patch.workDir ?? '') : undefined
+     if (patch.name !== undefined) {
+-      const next = String(patch.name).trim().slice(0, 40)
++      const next = cut(String(patch.name).trim(), 40).text
+       const clash = rt.findBot(next)
+       if (next === '' || (clash && clash.id !== id)) throw new Error(`Name ${next} is not available`)
+       // A name saved before the rule stays usable until it changes.
+@@ -177,7 +177,7 @@ export function install(rt) {
+       await ctx.sessionTitle.rename(agent.session, next)
+       await followMemberNames(Object.values(state.rooms).filter(room => room.members.includes(id)))
+     }
+-    if (patch.role !== undefined) bot.role = String(patch.role).trim().slice(0, 24)
++    if (patch.role !== undefined) bot.role = cut(String(patch.role).trim(), 24).text
+     if (patch.instructions !== undefined) bot.instructions = String(patch.instructions).trim()
+     let modelChanged = false
+     if (patch.color !== undefined) {
 @@ -189,6 +189,8 @@ export function install(rt) {
        if (avatar) bot.avatar = avatar
        else delete bot.avatar
diff --git a/patches/ds-bot/0009-identity-schema.patch b/patches/ds-bot/0009-identity-schema.patch
index e78069825..9610adecc 100644
--- a/patches/ds-bot/0009-identity-schema.patch
+++ b/patches/ds-bot/0009-identity-schema.patch
@@ -42,7 +42,7 @@ diff --git a/test/roster.test.js b/test/roster.test.js
  // busy machine.
  const until = async (check) => {
    const end = Date.now() + 2000
-@@ -77,46 +77,68 @@ const until = async (check) => {
+@@ -77,48 +77,79 @@ const until = async (check) => {
    }
  }
  
@@ -123,8 +123,19 @@ diff --git a/test/roster.test.js b/test/roster.test.js
 +  assert.equal(typed.model, 'deepseek/deepseek-v4-flash')
  })
  
++// P-275: a Bot's name is bounded at 40 and its role at 24, and both bounds cut UTF-16 units.
++// A bound that lands inside an emoji stores half of a surrogate pair, so the sidebar, the
++// session title and the store's JSON carry U+FFFD instead of the character.
++const bounded = (actual, source, max) => {
++  assert.ok(actual.length <= max, `${actual.length} code units, over ${max}`)
++  assert.equal(actual.isWellFormed(), true, `not well formed: ${actual}`)
++  assert.equal(Buffer.from(actual, 'utf8').equals(Buffer.from(source, 'utf8').subarray(0, Buffer.byteLength(actual))), true, 'the value is a UTF-8 byte prefix of what was typed')
++}
++
  test('a new name must be one "@" can call; a name saved before the rule still saves', async (t) => {
-@@ -129,85 +129,36 @@ test('a new name must be one "@" can call; a name saved before the rule still sa
+   const { call, stop } = start(undefined, { models: ['deepseek-v4-flash'] })
+   t.after(stop)
+@@ -129,85 +129,59 @@ test('a new name must be one "@" can call; a name saved before the rule still sa
    assert.equal((await call('update-bot', { id: writer.id, name: '新 Writer' })).ok, true)
  })
  
@@ -167,13 +178,10 @@ diff --git a/test/roster.test.js b/test/roster.test.js
 -
 -test('a first message from the user is helped with, not replaced by an opening question', async (t) => {
 -  const { call, stop, sent } = start(undefined, { models: ['deepseek-v4-flash'] })
-+// Creation is silent (#645): no path that makes a Bot opens a turn, and only a brief from a
-+// Bot that creates one (`create_bot`) becomes instructions. A line typed in the new-Bot card
-+// is the user's first request, sent as a turn by the client, never a standing rule.
-+test('creating a Bot sends it nothing, and only a parent Bot\'s brief becomes its instructions', async (t) => {
-+  const { call, stop, sent, ctx } = start(undefined, { models: ['deepseek-v4-flash'] })
++test('a name and a role stop their bound before a split surrogate pair', async (t) => {
++  const { call, stop } = start(undefined, { models: ['deepseek-v4-flash'] })
    t.after(stop)
--  await call('state', {})
+   await call('state', {})
 -  const brief = 'Review the team notes and list the next tasks.'
 -  const bot = (await call('create-bot', { name: 'Writer', brief })).value
 -  await until(() => sent.some(entry => entry.sessionId === bot.id))
@@ -181,6 +189,31 @@ diff --git a/test/roster.test.js b/test/roster.test.js
 -  assert.ok(text.includes(brief))
 -  assert.match(text, /then help with it\./)
 -  assert.doesNotMatch(text, /\b(?:ask_user(?:_question)?|allowCustom)\b/)
++  const name = `${'a'.repeat(39)}\u{1F600}tail`
++  const role = `${'b'.repeat(23)}\u{1F600}tail`
++  const writer = (await call('create-bot', { name, role })).value
++  assert.equal(writer.name, 'a'.repeat(39), 'the bound retracts one unit instead of splitting the pair')
++  bounded(writer.name, name, 40)
++  assert.equal(writer.role, 'b'.repeat(23))
++  bounded(writer.role, role, 24)
++  // A rename and a role edit take the same two bounds.
++  const renamed = `${'c'.repeat(39)}\u{1F600}tail`
++  const reRole = `${'d'.repeat(23)}\u{1F600}tail`
++  assert.equal((await call('update-bot', { id: writer.id, name: renamed })).ok, true)
++  assert.equal((await call('update-bot', { id: writer.id, role: reRole })).ok, true)
++  const saved = (await call('state', {})).value.bots.find(entry => entry.id === writer.id)
++  assert.equal(saved.name, 'c'.repeat(39))
++  bounded(saved.name, renamed, 40)
++  assert.equal(saved.role, 'd'.repeat(23))
++  bounded(saved.role, reRole, 24)
++})
++
++// Creation is silent (#645): no path that makes a Bot opens a turn, and only a brief from a
++// Bot that creates one (`create_bot`) becomes instructions. A line typed in the new-Bot card
++// is the user's first request, sent as a turn by the client, never a standing rule.
++test('creating a Bot sends it nothing, and only a parent Bot\'s brief becomes its instructions', async (t) => {
++  const { call, stop, sent, ctx } = start(undefined, { models: ['deepseek-v4-flash'] })
++  t.after(stop)
 +  const chief = (await call('state', {})).value.mainBotId
 +  const brief = '帮我写周报'
 +  const writer = (await call('create-bot', { name: 'Writer', instructions: 'Write.', brief })).value