@@ -0,0 +1 @@
+The host's turn lines no longer split a surrogate pair at their character bounds ([#1984](https://github.com/ThinkFlowLab/FlyBot/issues/1984)): a failed turn's 500-unit message, the 200-unit message of its one-line reason, the 79-unit step a running call shows, an approval card's 300-unit description and 400-unit command, and the 160-unit reason a failed turn leaves for the inbox now cut on a code point boundary, so a line that ends on an emoji keeps the whole emoji instead of an unpaired half the encoder turns into U+FFFD.
@@ -4,7 +4,7 @@
 // Turn tracking: which turns were triggered by another Bot, and what they said.
 import { REFERENCE_KIND, REPLY_KIND, SOURCE_KIND } from './constants.js'
 import { unwrapUntrusted } from './delivery.js'
-import { textOf } from './text.js'
+import { cut, textOf } from './text.js'
 import { reminderText } from './schedules.js'
 import { OTHER, combine, originOfSource, settled } from './turn-origin.js'
 
@@ -33,7 +33,7 @@ export function isRemoteFailureNotice(text) {
 // error row, an AUTH failure loses its message: providers may echo part of the key.
 export function turnFailure(error) {
   const code = typeof error?.code === 'string' && error.code !== '' ? error.code : 'UNKNOWN'
-  const message = code === 'AUTH' || typeof error?.message !== 'string' ? '' : error.message.trim().slice(0, 500)
+  const message = code === 'AUTH' || typeof error?.message !== 'string' ? '' : cut(error.message.trim(), 500).text
   return {
     code,
     message,
@@ -42,7 +42,7 @@ export function turnFailure(error) {
   }
 }
 
-export const failureLine = failure => `${failure.code}${failure.status ? ` ${failure.status}` : ''}${failure.message ? `: ${failure.message.slice(0, 200)}` : ''}`
+export const failureLine = failure => `${failure.code}${failure.status ? ` ${failure.status}` : ''}${failure.message ? `: ${cut(failure.message, 200).text}` : ''}`
 
 // A group's own Session never reaches a model, so the snapshot DSH prepared there
 // rides with the user's queued message to the members who answer it.
@@ -300,7 +300,9 @@ export function install(rt) {
     const value = ['command', 'cmd', 'pattern', 'query', 'url', 'file_path', 'path', 'description']
       .map(key => args?.[key]).find(item => typeof item === 'string' && item.trim() !== '')
     const line = value?.replace(/\s+/g, ' ').trim()
-    return line && line.length > 80 ? `${line.slice(0, 79)}…` : line
+    if (!line) return line
+    const bound = cut(line, 79)
+    return bound.cut ? `${bound.text}…` : line
   }
 
   // Work a group member hands a Bot with message_bot runs in a hidden turn of the Bot's own chat,
@@ -360,7 +362,7 @@ export function install(rt) {
     const first = keys => keys.map(key => args?.[key]).find(value => typeof value === 'string' && value.trim() !== '')
     const text = first(['description', 'justification'])
     const code = first(['command', 'cmd', 'file_path', 'path', 'url', 'query'])
-    return { ...(text ? { text: text.trim().slice(0, 300) } : {}), ...(code ? { code: code.trim().slice(0, 400) } : {}) }
+    return { ...(text ? { text: cut(text.trim(), 300).text } : {}), ...(code ? { code: cut(code.trim(), 400).text } : {}) }
   }
 
   // The latest turns of the user's own Bots that finished or failed, for a system notification
@@ -402,7 +404,7 @@ export function install(rt) {
       ...(owner ? { roomId: owner.roomId } : { sessionId: id }),
       at,
       ...(calls > 0 ? { calls } : {}),
-      ...(failure ? { failed: (failure.message || failure.code).slice(0, 160) } : {}),
+      ...(failure ? { failed: cut(failure.message || failure.code, 160).text } : {}),
       ...(rateLimited !== undefined ? { rateLimited } : {}),
       ...(silent ? { silent: true, streak } : {}),
     }], at)
 
@@ -101,6 +101,19 @@ test('#1044: a turn that wrote text then failed adds no line', async (t) => {
   assert.equal(failureLines({ ended: await host.ended() }, 'b', key => key).length, 0)
 })
 
+// The reason a failed turn leaves for the inbox is cut at 160 units: a bound inside a surrogate pair
+// leaves a lone high half, which the stored record keeps and every client draws as U+FFFD.
+test('a failed turn records its reason cut at 160 units without splitting a pair', async (t) => {
+  const host = await start()
+  t.after(host.stop)
+  const message = `${'a'.repeat(159)}😀tail`
+  die(host.emit, 'b', 1, { code: 'SERVER', message })
+  const [entry] = await host.ended()
+  assert.equal(entry.failed.isWellFormed(), true, `the stored reason is not well formed: ${JSON.stringify(entry.failed.slice(-4))}`)
+  assert.equal(entry.failed, message.slice(0, 159))
+  assert.ok(entry.failed.length <= 160, `the 160-unit budget moved: ${entry.failed.length}`)
+})
+
 test('#1044: three dead turns in a row are three lines and the streak is visible', async (t) => {
   const host = await start()
   t.after(host.stop)
 
@@ -234,6 +234,29 @@ test('turnFailure drops AUTH messages and keeps the facts', () => {
   assert.equal(failureLine({ code: 'SERVER', status: 503, message: 'busy' }), 'SERVER 503: busy')
 })
 
+// A bound that lands between the halves of a surrogate pair keeps the high half alone, and that lone
+// surrogate is what the record carries and every renderer draws as U+FFFD. The five bounds in
+// turns.js go through `cut()`; each has its own case, in the file that reads its value.
+test('a failure message cut at its 500-unit bound keeps the pair whole', () => {
+  const message = `${'a'.repeat(499)}😀tail`
+  const kept = turnFailure({ code: 'SERVER', message }).message
+  assert.equal(kept.isWellFormed(), true, `the message is not well formed: ${JSON.stringify(kept.slice(-4))}`)
+  // The emoji needs two units and only one is left inside the bound, so the prefix stops before it.
+  assert.equal(kept, message.slice(0, 499))
+  assert.ok(kept.length <= 500, `the 500-unit budget moved: ${kept.length}`)
+  // A pair that ends exactly on the bound stays whole.
+  const exact = `${'a'.repeat(498)}😀`
+  assert.deepEqual(turnFailure({ code: 'SERVER', message: exact }).message, exact)
+})
+
+test('a failure line cut at its 200-unit message bound keeps the pair whole', () => {
+  const line = failureLine({ code: 'SERVER', status: 503, message: `${'a'.repeat(199)}😀tail` })
+  assert.equal(line.isWellFormed(), true, `the line is not well formed: ${JSON.stringify(line.slice(-4))}`)
+  assert.equal(line, `SERVER 503: ${'a'.repeat(199)}`)
+  assert.ok(line.length <= 'SERVER 503: '.length + 200, `the 200-unit budget moved: ${line.length}`)
+  assert.equal(failureLine({ code: 'SERVER', status: 503, message: 'busy' }), 'SERVER 503: busy')
+})
+
 function turnsHost() {
   let listener
   const delivered = []
 
@@ -132,6 +132,29 @@ test('a group Session\'s approval waits in the team view, frees the round, and t
   assert.equal(text(post), '[Group post from Writer]\nCopied the doc to E:/docs.')
 })
 
+// Both fields of a card go through a bound of their own: 300 for the description, 400 for the
+// command. A cut that splits a surrogate pair leaves a lone high half the card draws as U+FFFD.
+test('an approval card cuts its description and command at their bounds without splitting a pair', async (t) => {
+  const host = await start()
+  t.after(host.stop)
+  const result = await openTurn(t, host)
+  const description = `${'a'.repeat(299)}😀tail`
+  const command = `${'b'.repeat(399)}😀tail`
+  host.emit('gb', 'tool/call', { callId: 'k1', name: 'pwsh', arguments: JSON.stringify({ command, description }) })
+  const outcome = host.askApproval('gb', { callId: 'k1' })
+
+  await settle(() => result() !== undefined)
+  const [approval] = (await host.call('state', {})).value.work.approvals
+  assert.equal(approval.detail.text.isWellFormed(), true, `the description is not well formed: ${JSON.stringify(approval.detail.text.slice(-4))}`)
+  assert.equal(approval.detail.text, description.slice(0, 299))
+  assert.equal(approval.detail.code.isWellFormed(), true, `the command is not well formed: ${JSON.stringify(approval.detail.code.slice(-4))}`)
+  assert.equal(approval.detail.code, command.slice(0, 399))
+  assert.ok(approval.detail.text.length <= 300 && approval.detail.code.length <= 400, `a budget moved: ${approval.detail.text.length}/${approval.detail.code.length}`)
+
+  assert.equal((await host.call('approval-answer', { id: approval.id, choice: 'allow' })).ok, true)
+  assert.equal(await outcome, 'allowed-once')
+})
+
 test('an own chat\'s approval stays with DSH and is listed while it waits', async (t) => {
   const host = await start()
   t.after(host.stop)
@@ -447,6 +470,24 @@ test('a running Bot\'s work names its current step, in one short line, until the
   assert.equal((await bots()).b, undefined)
 })
 
+// The step is 79 units plus an ellipsis, and the cut is decided by whether anything was dropped.
+test('a step line cut at its bound keeps the pair whole, and the ellipsis only shows when it cut', async (t) => {
+  const host = await start()
+  t.after(host.stop)
+  await openTurn(t, host)
+  const bots = async () => (await host.call('state', {})).value.work.bots
+  host.emit('gb', 'tool/call', { callId: 'k1', name: 'pwsh', arguments: JSON.stringify({ command: `${'a'.repeat(78)}😀tail` }) })
+  const { step } = (await bots()).b
+  assert.equal(step.isWellFormed(), true, `the step is not well formed: ${JSON.stringify(step.slice(-4))}`)
+  // The emoji needs two units and only one is left inside the 79, so the prefix stops before it.
+  assert.equal(step, `${'a'.repeat(78)}…`)
+  assert.ok(step.length <= 80, `the 79 + ellipsis budget moved: ${step.length}`)
+  host.emit('gb', 'tool/result', { callId: 'k1' })
+  host.emit('gb', 'tool/call', { callId: 'k2', name: 'pwsh', arguments: JSON.stringify({ command: 'npm test' }) })
+  assert.equal((await bots()).b.step, 'npm test')
+  host.emit('gb', 'tool/result', { callId: 'k2' })
+})
+
 // #626: the shape a Bot actually hits — the owner asks for work, the turn calls `subagent`, and the
 // child settles while that same turn is still running. The notice is an account of work the owner
 // already asked for, not a new request, so the connector tools stay.
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	+The host's turn lines no longer split a surrogate pair at their character bounds ([#1984](https://github.com/ThinkFlowLab/FlyBot/issues/1984)): a failed turn's 500-unit message, the 200-unit message of its one-line reason, the 79-unit step a running call shows, an approval card's 300-unit description and 400-unit command, and the 160-unit reason a failed turn leaves for the inbox now cut on a code point boundary, so a line that ends on an emoji keeps the whole emoji instead of an unpaired half the encoder turns into U+FFFD.