diff --git a/apps/desktop/src/main/services/CustomInstructionService.ts b/apps/desktop/src/main/services/CustomInstructionService.ts
index 37f49e9..72a6dd3 100644
--- a/apps/desktop/src/main/services/CustomInstructionService.ts
+++ b/apps/desktop/src/main/services/CustomInstructionService.ts
@@ -159,10 +159,11 @@ class CustomInstructionService {
 
     const existing = instructions[index]
 
-    // 프리셋은 프롬프트만 수정 가능
+    // 프리셋은 프롬프트만 수정 가능 — 폰과 짝이 있는 프리셋은 서버 프리셋 행으로도 올린다
     if (existing.isBuiltin) {
       if (data.prompt !== undefined) {
         instructions[index] = { ...existing, prompt: data.prompt, updatedAt: Date.now() }
+        getCloudSyncService().pushOne('builtin_instructions', id)
       }
     } else {
       instructions[index] = { ...existing, ...data, updatedAt: Date.now() }
@@ -203,6 +204,15 @@ class CustomInstructionService {
     saveInstructions()
   }
 
+  /** 동기화: 다른 기기에서 바꾼 프리셋 프롬프트를 반영한다(outbox에 넣지 않는다). 바꿨으면 true */
+  applyRemoteBuiltinPrompt(id: string, prompt: string): boolean {
+    const index = instructions.findIndex((i) => i.id === id)
+    if (index === -1 || !instructions[index].isBuiltin || instructions[index].prompt === prompt) return false
+    instructions[index] = { ...instructions[index], prompt, updatedAt: Date.now() }
+    saveInstructions()
+    return true
+  }
+
   /** 동기화: 다른 기기에서 지운 사용자 명령을 지운다. 프리셋은 건드리지 않는다. */
   removeRemote(id: string): boolean {
     const index = instructions.findIndex((i) => i.id === id)
@@ -252,6 +262,7 @@ class CustomInstructionService {
 
     instructions = [...builtins, ...userInstructions]
     saveInstructions()
+    for (const builtin of builtins) getCloudSyncService().pushOne('builtin_instructions', builtin.id)
     logger.info('Builtin instructions reset')
   }
 
@@ -260,6 +271,11 @@ class CustomInstructionService {
   }
 }
 
+/** 데스크톱 프리셋의 기본 프롬프트(되돌리기·수정 여부 판정용). 프리셋이 아니면 null */
+export function getBuiltinInstructionDefaultPrompt(id: string): string | null {
+  return BUILTIN_INSTRUCTIONS.find((b) => b.id === id)?.prompt ?? null
+}
+
 let instance: CustomInstructionService | null = null
 
 export function getCustomInstructionService(): CustomInstructionService {
diff --git a/apps/desktop/src/main/services/sync/SyncEngine.ts b/apps/desktop/src/main/services/sync/SyncEngine.ts
index 8dd3cb1..48b2471 100644
--- a/apps/desktop/src/main/services/sync/SyncEngine.ts
+++ b/apps/desktop/src/main/services/sync/SyncEngine.ts
@@ -20,6 +20,12 @@ import {
 } from './memo-tag-sync'
 import { fetchRemoteAudioOwners, isAudioSyncEnabled, listLocalAudioOwners, pushAudio } from './audio-sync'
 import { SETTINGS_ROW_ID, applyRemoteSettings, fetchRemoteSettings, pushSettings } from './settings-sync'
+import {
+  applyRemoteBuiltins,
+  editedBuiltinsDifferingFrom,
+  fetchRemoteBuiltins,
+  pushBuiltinPrompts,
+} from './builtin-instruction-sync'
 import {
   completeEntry,
   dropEntry,
@@ -223,6 +229,11 @@ export class SyncEngine extends EventEmitter {
       enqueueChange('user_settings', SETTINGS_ROW_ID, 'upsert', now)
       queued++
     }
+    // 데스크톱에서 고친 프리셋 프롬프트가 서버와 다르면 올린다(폰은 프리셋을 고칠 수 없다).
+    for (const id of editedBuiltinsDifferingFrom(await fetchRemoteBuiltins(ctx))) {
+      enqueueChange('builtin_instructions', id, 'upsert', now)
+      queued++
+    }
     if (isAudioSyncEnabled()) {
       for (const owner of ['history', 'meeting'] as const) {
         const local = listLocalAudioOwners(owner)
@@ -290,6 +301,7 @@ export class SyncEngine extends EventEmitter {
       'meeting_memos',
       'meeting_documents',
       'custom_instructions',
+      'builtin_instructions',
       'user_settings',
       'user_templates',
       'knowledge_documents',
@@ -326,6 +338,8 @@ export class SyncEngine extends EventEmitter {
         return pushMemoTagAdds(ctx, ids)
       case 'user_settings':
         return [{ id: SETTINGS_ROW_ID, error: await pushSettings(ctx) }]
+      case 'builtin_instructions':
+        return pushBuiltinPrompts(ctx, ids)
       case 'history_audio':
         return pushAudio(ctx, 'history', ids)
       case 'meeting_audio':
@@ -416,6 +430,19 @@ export class SyncEngine extends EventEmitter {
       logger.warn(`Pull user_settings failed: ${message}`)
     }
 
+    try {
+      const builtins = await fetchRemoteBuiltins({ remote: this.remote, userId: this.userId })
+      const applied = applyRemoteBuiltins(builtins, new Set(pendingOps('builtin_instructions').keys()))
+      if (applied > 0) {
+        changed.add('custom_instructions')
+        result.pulled += applied
+      }
+    } catch (err) {
+      const message = err instanceof Error ? err.message : String(err)
+      result.errors.push(`builtin_instructions: ${message}`)
+      logger.warn(`Pull builtin_instructions failed: ${message}`)
+    }
+
     result.changed = [...changed]
     if (result.errors.length === 0) setSyncState('lastPullAt', String(this.now()))
   }
diff --git a/apps/desktop/src/main/services/sync/builtin-instruction-sync.ts b/apps/desktop/src/main/services/sync/builtin-instruction-sync.ts
new file mode 100644
index 0000000..743c5fd
--- /dev/null
+++ b/apps/desktop/src/main/services/sync/builtin-instruction-sync.ts
@@ -0,0 +1,118 @@
+// src/main/services/sync/builtin-instruction-sync.ts
+// 데스크톱 프리셋 명령의 프롬프트 수정을 서버 프리셋 행(builtin_key)에 맞춘다.
+// 폰은 명령을 서버 행의 프롬프트로 실행하므로, 데스크톱에서 고친 프롬프트가 폰에서도 쓰인다.
+// 서버 행은 RLS상 직접 못 고치므로 sync_set_builtin_instruction_prompt_v1 로만 바꾼다(null = 기본값 복원).
+
+import { getBuiltinInstructionDefaultPrompt, getCustomInstructionService } from '../CustomInstructionService'
+import type { PushContext } from './sync-adapters'
+import { toSyncRemoteError, type PushOutcome } from './sync-types'
+
+/** 데스크톱 프리셋 id → 서버 builtin_key. '자유 프롬프트'는 실행 때 입력받는 명령이라 폰에 대응이 없다. */
+export const DESKTOP_TO_SERVER_BUILTIN: Readonly<Record<string, string>> = {
+  'builtin-translate': 'translate_en',
+  'builtin-summarize': 'summarize',
+  'builtin-formal': 'formal',
+  'builtin-explain-code': 'explain_code',
+}
+
+const SERVER_TO_DESKTOP_BUILTIN: Readonly<Record<string, string>> = Object.fromEntries(
+  Object.entries(DESKTOP_TO_SERVER_BUILTIN).map(([desktop, server]) => [server, desktop])
+)
+
+export function isSyncedBuiltin(id: string): boolean {
+  return id in DESKTOP_TO_SERVER_BUILTIN
+}
+
+/**
+ * 폰은 `{{text}}` 외의 자리표시자를 치환하지 않는다. 서버 번역 프리셋은 영어 고정(translate_en)이고
+ * 데스크톱 번역도 대상 언어 설정이 없어 영어로만 번역하므로 `{{targetLanguage}}` 를 English 로 바꿔 올린다.
+ */
+export function toServerPrompt(desktopId: string, prompt: string): string {
+  return desktopId === 'builtin-translate' ? prompt.replace(/\{\{targetLanguage\}\}/g, 'English') : prompt
+}
+
+function isEdited(desktopId: string, prompt: string): boolean {
+  const defaultPrompt = getBuiltinInstructionDefaultPrompt(desktopId)
+  return defaultPrompt !== null && prompt.trim() !== defaultPrompt.trim()
+}
+
+export async function pushBuiltinPrompts(ctx: PushContext, ids: string[]): Promise<PushOutcome[]> {
+  const service = getCustomInstructionService()
+  const outcomes: PushOutcome[] = []
+  for (const id of ids) {
+    const key = DESKTOP_TO_SERVER_BUILTIN[id]
+    const local = service.getById(id)
+    if (!key || !local) {
+      outcomes.push({ id, error: null })
+      continue
+    }
+    try {
+      await ctx.remote.rpc('sync_set_builtin_instruction_prompt_v1', {
+        p_builtin_key: key,
+        p_prompt: isEdited(id, local.prompt) ? toServerPrompt(id, local.prompt) : null,
+      })
+      outcomes.push({ id, error: null })
+    } catch (err) {
+      outcomes.push({ id, error: toSyncRemoteError(err) })
+    }
+  }
+  return outcomes
+}
+
+interface RemoteBuiltin {
+  key: string
+  prompt: string
+  isDefault: boolean
+}
+
+export async function fetchRemoteBuiltins(ctx: PushContext): Promise<RemoteBuiltin[]> {
+  const data = await ctx.remote.rpc('sync_list_builtin_instructions_v1', {})
+  if (!Array.isArray(data)) return []
+  const rows: RemoteBuiltin[] = []
+  for (const item of data) {
+    if (typeof item !== 'object' || item === null) continue
+    const row = item as Record<string, unknown>
+    if (typeof row.builtin_key === 'string' && typeof row.prompt === 'string') {
+      rows.push({ key: row.builtin_key, prompt: row.prompt, isDefault: row.is_default === true })
+    }
+  }
+  return rows
+}
+
+/** 데스크톱에서 고쳤지만 서버와 다른 프리셋 (최초 대조용) */
+export function editedBuiltinsDifferingFrom(remote: RemoteBuiltin[]): string[] {
+  const service = getCustomInstructionService()
+  const byKey = new Map(remote.map((r) => [r.key, r]))
+  return Object.entries(DESKTOP_TO_SERVER_BUILTIN)
+    .filter(([id, key]) => {
+      const local = service.getById(id)
+      if (!local || !isEdited(id, local.prompt)) return false
+      const server = byKey.get(key)
+      return !server || server.prompt !== toServerPrompt(id, local.prompt)
+    })
+    .map(([id]) => id)
+}
+
+/**
+ * 서버 프리셋 프롬프트를 로컬에 반영한다. 기본값이면 데스크톱 기본값으로, 아니면 서버 문구로.
+ * 올린 적이 있는 같은 문구(번역의 English 치환 포함)는 그대로 둔다. 바꾼 개수를 돌려준다.
+ */
+export function applyRemoteBuiltins(remote: RemoteBuiltin[], pending: ReadonlySet<string>): number {
+  const service = getCustomInstructionService()
+  let changed = 0
+  for (const row of remote) {
+    const id = SERVER_TO_DESKTOP_BUILTIN[row.key]
+    if (!id || pending.has(id)) continue
+    const local = service.getById(id)
+    if (!local) continue
+    let next: string | null = null
+    if (row.isDefault) {
+      const defaultPrompt = getBuiltinInstructionDefaultPrompt(id)
+      if (defaultPrompt !== null && isEdited(id, local.prompt)) next = defaultPrompt
+    } else if (toServerPrompt(id, local.prompt) !== row.prompt) {
+      next = row.prompt
+    }
+    if (next !== null && service.applyRemoteBuiltinPrompt(id, next)) changed++
+  }
+  return changed
+}
diff --git a/apps/desktop/src/main/services/sync/supabase-sync-remote.ts b/apps/desktop/src/main/services/sync/supabase-sync-remote.ts
index fce6e72..faa821e 100644
--- a/apps/desktop/src/main/services/sync/supabase-sync-remote.ts
+++ b/apps/desktop/src/main/services/sync/supabase-sync-remote.ts
@@ -122,6 +122,17 @@ export class SupabaseSyncRemote implements SyncRemote {
     if (error) throw toSyncRemoteError(error)
   }
 
+  async deleteChildrenFrom(
+    table: string,
+    parentColumn: string,
+    parentId: string,
+    indexColumn: string,
+    fromIndex: number
+  ): Promise<void> {
+    const { error } = await this.client.from(table).delete().eq(parentColumn, parentId).gte(indexColumn, fromIndex)
+    if (error) throw toSyncRemoteError(error)
+  }
+
   async invokeFunction(name: string, body: Record<string, unknown>): Promise<unknown> {
     const { data, error } = await this.client.functions.invoke(name, { body })
     if (error) throw toSyncRemoteError(error)
diff --git a/apps/desktop/src/main/services/sync/sync-adapters.ts b/apps/desktop/src/main/services/sync/sync-adapters.ts
index 57099c2..0ec6a6c 100644
--- a/apps/desktop/src/main/services/sync/sync-adapters.ts
+++ b/apps/desktop/src/main/services/sync/sync-adapters.ts
@@ -18,6 +18,7 @@ import { getDictationTemplateService } from '../DictationTemplateService'
 import { getMeetingDocTemplateService } from '../MeetingDocTemplateService'
 import { getRAGService } from '../RAGService'
 import { purgeRemoteAudio } from './audio-sync'
+import { pushMeetingSegments } from './transcript-sync'
 import { dropEntry } from './sync-outbox'
 import {
   SyncRemoteError,
@@ -441,6 +442,17 @@ const meetingsAdapter: SyncAdapter = {
       'meetings',
       rows.map((r) => ({ id: r.id, row: meetingToRemote(r, ctx.userId) }))
     )
+    // 회의 행이 올라간 뒤 전사 구간을 맞춘다 — 폰은 구간이 있으면 구간을 그린다.
+    const byId = new Map(rows.map((r) => [r.id, r]))
+    for (const outcome of outcomes) {
+      const row = byId.get(outcome.id)
+      if (outcome.error !== null || !row) continue
+      try {
+        await pushMeetingSegments(ctx, row)
+      } catch (err) {
+        outcome.error = toSyncRemoteError(err)
+      }
+    }
     return [...outcomes, ...missingAsDone(ids, found)]
   },
   async pushDeletes(ctx, ids) {
diff --git a/apps/desktop/src/main/services/sync/sync-types.ts b/apps/desktop/src/main/services/sync/sync-types.ts
index 5b24fa6..54f643e 100644
--- a/apps/desktop/src/main/services/sync/sync-types.ts
+++ b/apps/desktop/src/main/services/sync/sync-types.ts
@@ -17,6 +17,8 @@ export const SYNC_ENTITIES = [
   /** 녹음 파일 업로드(row_id = history id / meeting id) */
   'history_audio',
   'meeting_audio',
+  /** 데스크톱 프리셋 명령 프롬프트(row_id = 데스크톱 프리셋 id) → 서버 프리셋 행 */
+  'builtin_instructions',
 ] as const
 
 export type SyncEntity = (typeof SYNC_ENTITIES)[number]
@@ -68,6 +70,8 @@ export interface SyncRemote {
   updateMatching(table: string, userId: string, match: Record<string, string | number>, patch: RemoteRow): Promise<number>
   deleteByIds(table: string, userId: string, ids: string[]): Promise<void>
   deleteChildren(table: string, parentColumn: string, parentId: string): Promise<void>
+  /** 부모의 자식 중 indexColumn >= fromIndex 인 행을 지운다 (줄어든 구간 정리) */
+  deleteChildrenFrom(table: string, parentColumn: string, parentId: string, indexColumn: string, fromIndex: number): Promise<void>
   rpc(name: string, params: Record<string, unknown>): Promise<unknown>
   invokeFunction(name: string, body: Record<string, unknown>): Promise<unknown>
   uploadObject(bucket: string, key: string, bytes: Uint8Array, contentType: string): Promise<void>
diff --git a/apps/desktop/src/main/services/sync/transcript-sync.ts b/apps/desktop/src/main/services/sync/transcript-sync.ts
new file mode 100644
index 0000000..6aec8d5
--- /dev/null
+++ b/apps/desktop/src/main/services/sync/transcript-sync.ts
@@ -0,0 +1,44 @@
+// src/main/services/sync/transcript-sync.ts
+// 데스크톱 회의 전사를 Supabase `transcripts` 구간으로 맞춘다.
+// 모바일은 구간이 하나라도 있으면 edited_transcript 대신 구간을 그리므로, 데스크톱이 전사를 바꾸면
+// (녹음 완료·직접 수정·자동 다듬기·화자 구분) 구간도 같이 바꿔야 폰에 보인다.
+
+import { parseTranscriptLines } from '@d3ro/core/meeting-transcript'
+import type { meetingSessions } from '../../db/schema'
+import type { PushContext } from './sync-adapters'
+import type { RemoteRow } from './sync-types'
+
+const SEGMENT_BATCH = 500
+
+/** 로컬 회의 행 → 서버 구간 행. 전사가 없으면(녹음 중 등) null — 서버 구간을 건드리지 않는다. */
+export function meetingSegmentsToRemote(row: typeof meetingSessions.$inferSelect): RemoteRow[] | null {
+  const edited = row.editedTranscript !== null && row.editedTranscript.trim() !== ''
+  const lines = parseTranscriptLines(edited ? row.editedTranscript : row.rawTranscript)
+  if (lines.length === 0) return null
+  return lines.map((line, index) => {
+    const next = lines[index + 1]
+    const duration = next ? next.timestampMs - line.timestampMs : null
+    return {
+      meeting_id: row.id,
+      segment_index: index,
+      timestamp_ms: line.timestampMs,
+      duration_ms: duration !== null && duration > 0 ? duration : null,
+      text: line.text,
+      speaker: line.speaker,
+      edited,
+    }
+  })
+}
+
+/** 구간을 upsert 하고, 줄 수가 줄었으면 뒤쪽 구간을 지운다(한 번에 비우지 않아 폰 화면이 깜빡이지 않는다). */
+export async function pushMeetingSegments(
+  ctx: PushContext,
+  row: typeof meetingSessions.$inferSelect
+): Promise<void> {
+  const segments = meetingSegmentsToRemote(row)
+  if (!segments) return
+  for (let i = 0; i < segments.length; i += SEGMENT_BATCH) {
+    await ctx.remote.upsert('transcripts', segments.slice(i, i + SEGMENT_BATCH), 'meeting_id,segment_index')
+  }
+  await ctx.remote.deleteChildrenFrom('transcripts', 'meeting_id', row.id, 'segment_index', segments.length)
+}
diff --git a/apps/desktop/src/renderer/components/meeting/MeetingDetailTabs.tsx b/apps/desktop/src/renderer/components/meeting/MeetingDetailTabs.tsx
index 56bc073..9e08f7f 100644
--- a/apps/desktop/src/renderer/components/meeting/MeetingDetailTabs.tsx
+++ b/apps/desktop/src/renderer/components/meeting/MeetingDetailTabs.tsx
@@ -2,6 +2,7 @@
 // Modern AI Meeting Studio: Dual-Canvas Split View (Transcript + AI Minutes & Granola Notepad)
 
 import React, { useState, useEffect, useCallback, useMemo, useRef } from 'react'
+import { parseTranscriptLines } from '@d3ro/core/meeting-transcript'
 import {
   Box,
   Tabs,
@@ -54,33 +55,14 @@ function parseSegments(
   rawTranscript: string | null,
   editedTranscript: string | null,
 ): Array<{ id: string; timestamp: number; text: string; edited: boolean; speaker?: string }> {
-  const source = editedTranscript || rawTranscript || ''
-  const regex = /^\[(\d{2}):(\d{2})\]\s*(?:\[([^\]]+)\]\s*)?(.+)$/
-  return source
-    .split('\n')
-    .filter((line) => line.trim())
-    .map((line, idx) => {
-      const m = regex.exec(line.trim())
-      if (m) {
-        const min = parseInt(m[1], 10)
-        const sec = parseInt(m[2], 10)
-        const speaker = m[3] || undefined
-        const text = m[4]
-        return {
-          id: `seg-${idx}`,
-          timestamp: (min * 60 + sec) * 1000,
-          text,
-          edited: false,
-          speaker,
-        }
-      }
-      return {
-        id: `seg-${idx}`,
-        timestamp: idx * 4000,
-        text: line.trim(),
-        edited: false,
-      }
-    })
+  // 줄 ↔ 구간 변환은 core 정본을 쓴다 — 서버 transcripts 구간도 같은 규칙으로 만들어진다.
+  return parseTranscriptLines(editedTranscript || rawTranscript).map((line, idx) => ({
+    id: `seg-${idx}`,
+    timestamp: line.timestampMs,
+    text: line.text,
+    edited: false,
+    speaker: line.speaker ?? undefined,
+  }))
 }
 
 // Extract Action items from documents
diff --git a/apps/desktop/tests/helpers/fakeSyncRemote.ts b/apps/desktop/tests/helpers/fakeSyncRemote.ts
index 774f64e..8b73939 100644
--- a/apps/desktop/tests/helpers/fakeSyncRemote.ts
+++ b/apps/desktop/tests/helpers/fakeSyncRemote.ts
@@ -156,6 +156,36 @@ export class FakeSyncRemote implements SyncRemote {
     for (let i = rows.length - 1; i >= 0; i--) if (rows[i][parentColumn] === parentId) rows.splice(i, 1)
   }
 
+  async deleteChildrenFrom(
+    table: string,
+    parentColumn: string,
+    parentId: string,
+    indexColumn: string,
+    fromIndex: number
+  ): Promise<void> {
+    this.guard()
+    const rows = this.rows(table)
+    for (let i = rows.length - 1; i >= 0; i--) {
+      if (rows[i][parentColumn] === parentId && Number(rows[i][indexColumn]) >= fromIndex) rows.splice(i, 1)
+    }
+  }
+
+  /** 서버 프리셋 기본 프롬프트 (마이그레이션 0036 과 같은 문구) */
+  static readonly BUILTIN_DEFAULTS: Record<string, string> = {
+    translate_en: 'Translate the following text into natural English. Return only the translation.',
+    summarize: 'Summarize the following text in no more than three concise lines.',
+    formal: 'Rewrite the following text in a formal business style while preserving its meaning. Return only the rewritten text.',
+    explain_code: 'Explain the following code in Korean, including its responsibilities and important caveats.',
+  }
+
+  private ensureBuiltins(): void {
+    for (const [key, prompt] of Object.entries(FakeSyncRemote.BUILTIN_DEFAULTS)) {
+      if (!this.rows('custom_instructions').some((r) => r.builtin_key === key)) {
+        this.mobileInsert('custom_instructions', { id: crypto.randomUUID(), builtin_key: key, name: key, prompt, icon: 'x', sort_order: 10 })
+      }
+    }
+  }
+
   async invokeFunction(name: string, body: Record<string, unknown>): Promise<unknown> {
     this.guard()
     this.invoked.push(`${name}:${String(body.document_id ?? '')}`)
@@ -298,6 +328,26 @@ export class FakeSyncRemote implements SyncRemote {
       else this.mobileInsert('user_settings', { active_instruction_id: instructionId, revision: 1 })
       return row
     }
+    if (name === 'sync_set_builtin_instruction_prompt_v1') {
+      this.ensureBuiltins()
+      const key = String(params.p_builtin_key)
+      const fallback = FakeSyncRemote.BUILTIN_DEFAULTS[key]
+      if (!fallback) throw new SyncRemoteError('invalid_builtin_key', '22023', false)
+      const next = typeof params.p_prompt === 'string' && params.p_prompt.trim() ? params.p_prompt.trim() : fallback
+      const row = this.rows('custom_instructions').find((r) => r.builtin_key === key)!
+      if (row.prompt !== next) Object.assign(row, { prompt: next, revision: Number(row.revision) + 1, updated_at: this.now() })
+      return row
+    }
+    if (name === 'sync_list_builtin_instructions_v1') {
+      return this.rows('custom_instructions')
+        .filter((r) => typeof r.builtin_key === 'string')
+        .map((r) => ({
+          builtin_key: r.builtin_key,
+          prompt: r.prompt,
+          is_default: r.prompt === FakeSyncRemote.BUILTIN_DEFAULTS[String(r.builtin_key)],
+          updated_at: r.updated_at,
+        }))
+    }
     if (name === 'sync_delete_user_template_v1') {
       const id = String(params.p_id)
       if (!this.find('user_templates', id)) return false
diff --git a/apps/desktop/tests/integration/cross-device-sync.supabase.test.ts b/apps/desktop/tests/integration/cross-device-sync.supabase.test.ts
index 4d519a9..4df760f 100644
--- a/apps/desktop/tests/integration/cross-device-sync.supabase.test.ts
+++ b/apps/desktop/tests/integration/cross-device-sync.supabase.test.ts
@@ -332,6 +332,40 @@ describe.skipIf(!enabled)('cross-device sync against local Supabase', () => {
     vi.restoreAllMocks()
   }, 60_000)
 
+  it('데스크톱 전사가 폰이 그리는 구간으로 올라가고, 고친 프리셋 프롬프트가 폰 명령에 쓰인다', async () => {
+    const db = testDb.db
+    const meetingId = crypto.randomUUID()
+    const now = Date.now()
+    db.insert(meetingSessions).values({
+      id: meetingId,
+      title: 'segments',
+      status: 'completed',
+      startedAt: now,
+      rawTranscript: '[00:00] one\n[00:04] two\n[00:09] three',
+      createdAt: now,
+      updatedAt: now,
+    }).run()
+    enqueueChange('meetings', meetingId, 'upsert')
+    getCustomInstructionService().update('builtin-summarize', { prompt: '두 줄로 요약' })
+    enqueueChange('builtin_instructions', 'builtin-summarize', 'upsert')
+    const first = await engine.flush()
+    expect(first.errors).toEqual([])
+    const segments = must(await mobile.from('transcripts').select('segment_index,text,edited').eq('meeting_id', meetingId).order('segment_index'))
+    expect(segments.map((s) => s.text)).toEqual(['one', 'two', 'three'])
+
+    db.update(meetingSessions).set({ editedTranscript: '[00:00] [화자 1] one fixed', updatedAt: Date.now() }).where(eq(meetingSessions.id, meetingId)).run()
+    enqueueChange('meetings', meetingId, 'upsert')
+    expect((await engine.flush()).errors).toEqual([])
+    const edited = must(await mobile.from('transcripts').select('text,speaker,edited').eq('meeting_id', meetingId))
+    expect(edited).toEqual([{ text: 'one fixed', speaker: '화자 1', edited: true }])
+
+    const summarize = must(await mobile.from('custom_instructions').select('prompt').eq('user_id', userId).eq('builtin_key', 'summarize').single())
+    expect(summarize.prompt).toBe('두 줄로 요약')
+    // 폰은 여전히 프리셋 행을 직접 고칠 수 없다(RLS)
+    const blocked = await mobile.from('custom_instructions').update({ prompt: 'hack' }).eq('user_id', userId).eq('builtin_key', 'summarize').select('id')
+    expect(blocked.data ?? []).toEqual([])
+  })
+
   it('데스크톱이 기기 목록에 나타나고, 모바일에서 해제하면 revoked가 된다', async () => {
     const info = { deviceName: 'IT-DESKTOP', appVersion: '9.9.9', osVersion: 'test' }
     const first = await checkInDesktopDevice(desktop, userId, 'signin', info, null)
diff --git a/apps/desktop/tests/main/sync/SyncTranscriptsPresets.test.ts b/apps/desktop/tests/main/sync/SyncTranscriptsPresets.test.ts
new file mode 100644
index 0000000..c3e28e6
--- /dev/null
+++ b/apps/desktop/tests/main/sync/SyncTranscriptsPresets.test.ts
@@ -0,0 +1,135 @@
+// 회의 전사 구간(transcripts)과 프리셋 명령 프롬프트 동기화.
+
+import { afterEach, beforeEach, describe, expect, it } from 'vitest'
+import { eq } from 'drizzle-orm'
+import { createTestDb } from '../../helpers/createTestDb'
+import { FakeSyncRemote } from '../../helpers/fakeSyncRemote'
+import { bindTestDatabase, unbindTestDatabase } from '../../../src/main/db'
+import { meetingSessions } from '../../../src/main/db/schema'
+import { initInMemoryConfig, resetInMemoryConfig } from '../../../src/main/services/ConfigService'
+import {
+  getBuiltinInstructionDefaultPrompt,
+  getCustomInstructionService,
+  resetCustomInstructionServiceForTests,
+} from '../../../src/main/services/CustomInstructionService'
+import { resetDictationTemplateServiceForTests } from '../../../src/main/services/DictationTemplateService'
+import { resetMeetingDocTemplateServiceForTests } from '../../../src/main/services/MeetingDocTemplateService'
+import { SyncEngine } from '../../../src/main/services/sync/SyncEngine'
+import { enqueueChange, outboxCounts } from '../../../src/main/services/sync/sync-outbox'
+
+const USER = '11111111-1111-4111-8111-111111111111'
+
+let testDb: ReturnType<typeof createTestDb>
+let remote: FakeSyncRemote
+let engine: SyncEngine
+
+beforeEach(() => {
+  testDb = createTestDb()
+  bindTestDatabase(testDb.db, USER)
+  initInMemoryConfig()
+  resetCustomInstructionServiceForTests()
+  resetDictationTemplateServiceForTests()
+  resetMeetingDocTemplateServiceForTests()
+  getCustomInstructionService().initialize()
+  remote = new FakeSyncRemote(USER)
+  engine = new SyncEngine({ remote, userId: USER })
+})
+
+afterEach(() => {
+  engine.dispose()
+  unbindTestDatabase()
+  resetInMemoryConfig()
+  testDb.close()
+})
+
+function segmentsOf(meetingId: string): Array<Record<string, unknown>> {
+  return remote
+    .rows('transcripts')
+    .filter((r) => r.meeting_id === meetingId)
+    .sort((a, b) => Number(a.segment_index) - Number(b.segment_index))
+}
+
+describe('회의 전사 구간', () => {
+  it('데스크톱 전사를 구간으로 올리고, 수정·화자 구분을 반영하며 줄어든 구간은 지운다', async () => {
+    const id = crypto.randomUUID()
+    const now = Date.now()
+    testDb.db
+      .insert(meetingSessions)
+      .values({
+        id,
+        title: 'desk',
+        status: 'completed',
+        startedAt: now,
+        rawTranscript: '[00:00] 시작합니다\n[00:07] 첫 안건\n[00:15] 마무리',
+        createdAt: now,
+        updatedAt: now,
+      })
+      .run()
+    await engine.runFullSync()
+    expect(segmentsOf(id).map((s) => [s.segment_index, s.timestamp_ms, s.duration_ms, s.text, s.edited])).toEqual([
+      [0, 0, 7000, '시작합니다', false],
+      [1, 7000, 8000, '첫 안건', false],
+      [2, 15000, null, '마무리', false],
+    ])
+
+    testDb.db
+      .update(meetingSessions)
+      .set({ editedTranscript: '[00:00] [화자 1] 시작합니다\n[00:15] [화자 2] 마무리', updatedAt: Date.now() })
+      .where(eq(meetingSessions.id, id))
+      .run()
+    enqueueChange('meetings', id, 'upsert')
+    await engine.flush()
+    expect(segmentsOf(id).map((s) => [s.segment_index, s.speaker, s.text, s.edited])).toEqual([
+      [0, '화자 1', '시작합니다', true],
+      [1, '화자 2', '마무리', true],
+    ])
+  })
+
+  it('전사가 없는 회의(녹음 중)는 서버 구간을 건드리지 않는다', async () => {
+    const id = crypto.randomUUID()
+    remote.mobileInsert('meetings', { id, title: 'phone', status: 'completed', started_at: remote.now() })
+    remote.rows('transcripts').push({ id: crypto.randomUUID(), meeting_id: id, segment_index: 0, timestamp_ms: 0, text: 'phone text' })
+    await engine.runFullSync()
+    testDb.db.update(meetingSessions).set({ title: 'renamed', rawTranscript: null, updatedAt: Date.now() }).where(eq(meetingSessions.id, id)).run()
+    enqueueChange('meetings', id, 'upsert')
+    await engine.flush()
+    expect(segmentsOf(id).map((s) => s.text)).toEqual(['phone text'])
+  })
+})
+
+describe('프리셋 명령 프롬프트', () => {
+  it('데스크톱에서 고친 프리셋만 서버 프리셋 행으로 올리고, 번역 자리표시자는 English 로 바꾼다', async () => {
+    const service = getCustomInstructionService()
+    service.update('builtin-summarize', { prompt: '핵심만 두 줄로' })
+    service.update('builtin-translate', { prompt: '{{targetLanguage}}로 자연스럽게 번역' })
+    await engine.runFullSync()
+    const byKey = (key: string) => remote.rows('custom_instructions').find((r) => r.builtin_key === key)
+    expect(byKey('summarize')?.prompt).toBe('핵심만 두 줄로')
+    expect(byKey('translate_en')?.prompt).toBe('English로 자연스럽게 번역')
+    expect(byKey('formal')?.prompt).toBe(FakeSyncRemote.BUILTIN_DEFAULTS.formal)
+    expect(outboxCounts().pending).toBe(0)
+
+    // 다시 받아도 로컬 문구({{targetLanguage}})를 바꾸지 않는다
+    await engine.pull()
+    expect(service.getById('builtin-translate')?.prompt).toBe('{{targetLanguage}}로 자연스럽게 번역')
+
+    // 되돌리기 → 서버도 기본값
+    service.update('builtin-summarize', { prompt: getBuiltinInstructionDefaultPrompt('builtin-summarize') ?? '' })
+    enqueueChange('builtin_instructions', 'builtin-summarize', 'upsert')
+    await engine.flush()
+    expect(byKey('summarize')?.prompt).toBe(FakeSyncRemote.BUILTIN_DEFAULTS.summarize)
+  })
+
+  it('다른 데스크톱에서 고친 프리셋 프롬프트를 받고, 기본값 복원도 반영한다', async () => {
+    await remote.rpc('sync_set_builtin_instruction_prompt_v1', { p_builtin_key: 'formal', p_prompt: '회사 공문 말투로' })
+    const service = getCustomInstructionService()
+    await engine.runFullSync()
+    expect(service.getById('builtin-formal')?.prompt).toBe('회사 공문 말투로')
+
+    await remote.rpc('sync_set_builtin_instruction_prompt_v1', { p_builtin_key: 'formal', p_prompt: null })
+    await engine.pull()
+    expect(service.getById('builtin-formal')?.prompt).toBe(getBuiltinInstructionDefaultPrompt('builtin-formal'))
+    // '자유 프롬프트'는 폰에 대응이 없어 건드리지 않는다
+    expect(service.getById('builtin-free-prompt')?.prompt).toBe('{{userPrompt}}')
+  })
+})
diff --git a/packages/core/__tests__/meeting-transcript.test.ts b/packages/core/__tests__/meeting-transcript.test.ts
new file mode 100644
index 0000000..aefe723
--- /dev/null
+++ b/packages/core/__tests__/meeting-transcript.test.ts
@@ -0,0 +1,33 @@
+import { describe, expect, it } from 'vitest'
+import { formatTranscriptLines, parseTranscriptLines } from '../src/meeting-transcript'
+
+describe('meeting transcript lines', () => {
+  it('parses timestamps and speakers written by the desktop recorder and diarization', () => {
+    const text = '[00:05] 안녕하세요\n\n[01:12] [화자 2] 다음 안건입니다\n[12:03] [Speaker 1]   끝'
+    expect(parseTranscriptLines(text)).toEqual([
+      { timestampMs: 5_000, timed: true, speaker: null, text: '안녕하세요' },
+      { timestampMs: 72_000, timed: true, speaker: '화자 2', text: '다음 안건입니다' },
+      { timestampMs: 723_000, timed: true, speaker: 'Speaker 1', text: '끝' },
+    ])
+  })
+
+  it('keeps untimed lines (phone transcripts, manual edits) and carries the last time forward', () => {
+    expect(parseTranscriptLines('first line\n[00:30] timed\nfollow-up')).toEqual([
+      { timestampMs: 0, timed: false, speaker: null, text: 'first line' },
+      { timestampMs: 30_000, timed: true, speaker: null, text: 'timed' },
+      { timestampMs: 30_000, timed: false, speaker: null, text: 'follow-up' },
+    ])
+  })
+
+  it('drops empty and timestamp-only lines and round-trips through the formatter', () => {
+    const text = '[00:01] [화자 1] a\n[00:02]\nb'
+    const lines = parseTranscriptLines(text)
+    expect(lines).toHaveLength(2)
+    expect(formatTranscriptLines(lines)).toBe('[00:01] [화자 1] a\nb')
+  })
+
+  it('returns nothing for empty input', () => {
+    expect(parseTranscriptLines(null)).toEqual([])
+    expect(parseTranscriptLines('  \n ')).toEqual([])
+  })
+})
diff --git a/packages/core/package.json b/packages/core/package.json
index 705eaba..1750553 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -42,6 +42,10 @@
       "types": "./src/caption-streaming.ts",
       "default": "./src/caption-streaming.ts"
     },
+    "./meeting-transcript": {
+      "types": "./src/meeting-transcript.ts",
+      "default": "./src/meeting-transcript.ts"
+    },
     "./entitlement": {
       "types": "./src/entitlement.ts",
       "default": "./src/entitlement.ts"
diff --git a/packages/core/src/meeting-transcript.ts b/packages/core/src/meeting-transcript.ts
new file mode 100644
index 0000000..10edfdf
--- /dev/null
+++ b/packages/core/src/meeting-transcript.ts
@@ -0,0 +1,54 @@
+// packages/core/src/meeting-transcript.ts
+// 회의 전사 텍스트 ↔ 구간(segment) 변환의 정본.
+// 데스크톱은 전사를 `[MM:SS] [화자] 내용` 줄로 저장하고, Supabase `transcripts` 는 구간 행으로 저장한다
+// (모바일은 구간이 있으면 구간을 우선 표시한다). 두 표현을 이 한 곳에서만 바꾼다.
+
+export interface TranscriptLine {
+  /** 회의 시작 기준 ms. 시각 표기가 없는 줄은 앞 줄의 시각을 이어받는다(처음이면 0). */
+  timestampMs: number
+  /** 시각 표기가 있었는지 — 없으면 화면이 순번으로 대신 표시할 수 있다 */
+  timed: boolean
+  speaker: string | null
+  text: string
+}
+
+const LINE_PATTERN = /^\[(\d{1,3}):(\d{2})\]\s*(?:\[([^\]]+)\]\s*)?(.*)$/
+
+/** 빈 줄을 버리고 각 줄을 구간으로 나눈다. 내용이 빈 줄(`[00:01]` 만 있는 줄)도 버린다. */
+export function parseTranscriptLines(text: string | null | undefined): TranscriptLine[] {
+  if (!text) return []
+  const lines: TranscriptLine[] = []
+  let lastTimestamp = 0
+  for (const raw of text.split('\n')) {
+    const line = raw.trim()
+    if (!line) continue
+    const match = LINE_PATTERN.exec(line)
+    if (match) {
+      const content = match[4].trim()
+      lastTimestamp = (Number(match[1]) * 60 + Number(match[2])) * 1000
+      if (!content) continue
+      lines.push({ timestampMs: lastTimestamp, timed: true, speaker: match[3]?.trim() || null, text: content })
+    } else {
+      lines.push({ timestampMs: lastTimestamp, timed: false, speaker: null, text: line })
+    }
+  }
+  return lines
+}
+
+export function formatTranscriptTimestamp(ms: number): string {
+  const totalSeconds = Math.max(0, Math.floor(ms / 1000))
+  const minutes = Math.floor(totalSeconds / 60)
+  const seconds = totalSeconds % 60
+  return `${String(minutes).padStart(2, '0')}:${String(seconds).padStart(2, '0')}`
+}
+
+/** parseTranscriptLines 의 역변환(시각 표기가 없던 줄은 그대로). */
+export function formatTranscriptLines(lines: readonly TranscriptLine[]): string {
+  return lines
+    .map((l) => {
+      if (!l.timed) return l.text
+      const speaker = l.speaker ? `[${l.speaker}] ` : ''
+      return `[${formatTranscriptTimestamp(l.timestampMs)}] ${speaker}${l.text}`
+    })
+    .join('\n')
+}