diff --git a/docs/master-architecture.md b/docs/master-architecture.md
index 9a4ab34c..9d10ba1a 100644
--- a/docs/master-architecture.md
+++ b/docs/master-architecture.md
@@ -204,7 +204,7 @@ posimai-store（LP）
 | posimai-store | Stripe / VPS | アプリ販売 LP |
 | posimai-log | — | 開発ログビューワー（scribe 連携） |
 | posimai-boki | — | 簿記2級 学習 PWA（localStorage） |
-| posimai-sc | — | 支援士試験 学習 PWA（localStorage・非公式補助） |
+| posimai-sc | VPS API（app-state） | 支援士試験 学習 PWA（初学者向け・用語インデックス・試験モード・端末間再開同期） |
 
 ---
 
diff --git a/posimai-sc/index.html b/posimai-sc/index.html
index 9404785f..d71b8a19 100644
--- a/posimai-sc/index.html
+++ b/posimai-sc/index.html
@@ -135,6 +135,14 @@ header{display:flex;align-items:center;justify-content:space-between;padding:0 1
 .home-hint strong{color:var(--text2);font-weight:600}
 .home-hint kbd{font-family:'JetBrains Mono',monospace;font-size:10px;padding:2px 5px;border:1px solid var(--border);border-radius:4px;background:var(--surface)}
 .home-tools{display:flex;justify-content:center;flex-wrap:wrap;gap:10px;margin-bottom:16px}
+.sync-card{max-width:540px;margin:0 auto 16px;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:12px 14px}
+.sync-title{font-size:11px;font-weight:600;color:var(--text3);letter-spacing:.08em;text-transform:uppercase;display:flex;align-items:center;gap:6px;margin-bottom:8px}
+.sync-text{font-size:12px;color:var(--text2);line-height:1.6}
+.sync-row{display:flex;align-items:center;gap:8px;flex-wrap:wrap;margin-top:8px}
+.sync-status{font-size:11px;color:var(--text3)}
+.sync-error{font-size:11px;color:var(--err);margin-top:4px}
+.sync-input{flex:1;min-width:220px;background:var(--surface2);border:1px solid var(--border);border-radius:var(--radius-sm);padding:7px 10px;font-size:12px;color:var(--text);outline:none;font-family:'JetBrains Mono',monospace}
+.sync-input:focus{border-color:var(--accent-border)}
 .glossary-intro{font-size:12px;color:var(--text2);line-height:1.65;margin-bottom:12px}
 .glossary-search-wrap{position:relative;margin-bottom:8px}
 .glossary-search-icon{position:absolute;left:8px;top:50%;transform:translateY(-50%);color:var(--text3);pointer-events:none}
@@ -478,6 +486,23 @@ header{display:flex;align-items:center;justify-content:space-between;padding:0 1
           </button>
         </div>
 
+        <div class="sync-card">
+          <div class="sync-title">
+            <i data-lucide="cloud" style="width:12px;height:12px"></i>
+            端末間の再開同期
+          </div>
+          <div class="sync-text">PC とスマホで同じ学習状態を再開するため、クラウドに進捗を保存します。</div>
+          <div class="sync-row" x-show="syncEnabled">
+            <span class="sync-status" x-text="syncStatus"></span>
+            <button class="btn-sm" type="button" :disabled="syncBusy" @click="syncNow()">今すぐ同期</button>
+          </div>
+          <div class="sync-row" x-show="!syncEnabled">
+            <input class="sync-input" type="password" placeholder="posimai_api_key または JWT" x-model="syncToken" aria-label="同期キー入力">
+            <button class="btn-sm btn-accent" type="button" @click="enableSyncWithInput()">同期を有効化</button>
+          </div>
+          <div class="sync-error" x-show="syncLastError" x-text="syncLastError"></div>
+        </div>
+
         <!-- Weak drill button -->
         <div style="margin-bottom:20px;display:flex;justify-content:center">
           <button class="btn-sm" :class="weakDrillCandidates.length ? 'btn-accent' : ''"
diff --git a/posimai-sc/js/app.js b/posimai-sc/js/app.js
index 9ce6954b..f94ec3b0 100644
--- a/posimai-sc/js/app.js
+++ b/posimai-sc/js/app.js
@@ -1,6 +1,10 @@
 import { DRILLS } from './data/drills.js';
 import { CATEGORIES } from './data/categories.js';
 
+const API_BASE = 'https://api.soar-enrich.com/brain/api';
+const APP_ID = 'posimai-sc';
+const SYNC_KEY_LS = 'posimai_api_key';
+
 function shuffleInPlace(arr) {
   for (let i = arr.length - 1; i > 0; i--) {
     const j = Math.floor(Math.random() * (i + 1));
@@ -127,6 +131,14 @@ document.addEventListener('alpine:init', () => {
     examQuestions:[],
     examIdx:0,
     examQuizState:{},
+    syncToken:'',
+    syncEnabled:false,
+    syncBusy:false,
+    syncStatus:'未同期',
+    syncLastError:'',
+    syncStateAt:0,
+    syncRemoteAt:0,
+    syncTimer:null,
 
     init(){
       this.categories = CATEGORIES.map(cat=>({
@@ -140,6 +152,11 @@ document.addEventListener('alpine:init', () => {
       catch{ this.scores = {}; }
       try{ this.wrongUnits = JSON.parse(localStorage.getItem('posimai-sc-wrong')||'{}'); }
       catch{ this.wrongUnits = {}; }
+      this.syncStateAt = parseInt(localStorage.getItem('posimai-sc-state-at') || '0', 10) || 0;
+      const jwtToken = (localStorage.getItem('posimai_token') || '').trim();
+      const apiKey = (localStorage.getItem(SYNC_KEY_LS) || '').trim();
+      this.syncToken = jwtToken || apiKey;
+      this.syncEnabled = !!this.syncToken;
       const t = localStorage.getItem('posimai-sc-theme')||'system';
       this.isDark = t==='dark'||(t==='system'&&matchMedia('(prefers-color-scheme:dark)').matches);
       const uid=(new URLSearchParams(location.search).get('unit')||'').trim().toLowerCase();
@@ -153,6 +170,11 @@ document.addEventListener('alpine:init', () => {
       this.$watch('search', ()=>{
         this.$nextTick(()=>{ if(window.lucide) lucide.createIcons(); });
       });
+      if(this.syncEnabled){
+        this.pullCloudState().catch(()=>{});
+      } else {
+        this.syncStatus = '同期キー未設定';
+      }
       if('serviceWorker' in navigator){
         navigator.serviceWorker.register('/sw.js').catch(()=>{});
       }
@@ -180,6 +202,127 @@ document.addEventListener('alpine:init', () => {
           history.replaceState(null,'',path);
       }catch(e){}
     },
+    nowTs(){
+      return Date.now();
+    },
+    get localStateBlob(){
+      return {
+        progress: this.progress || {},
+        scores: this.scores || {},
+        wrongUnits: this.wrongUnits || {},
+        currentUnitId: this.currentUnit?.id || '',
+        stateAt: this.syncStateAt || this.nowTs()
+      };
+    },
+    applyStateBlob(blob){
+      const nextProgress = (blob && typeof blob.progress === 'object') ? blob.progress : {};
+      const nextScores = (blob && typeof blob.scores === 'object') ? blob.scores : {};
+      const nextWrong = (blob && typeof blob.wrongUnits === 'object') ? blob.wrongUnits : {};
+      this.progress = { ...nextProgress };
+      this.scores = { ...nextScores };
+      this.wrongUnits = { ...nextWrong };
+      try{ localStorage.setItem('posimai-sc-progress', JSON.stringify(this.progress)); }catch(e){}
+      try{ localStorage.setItem('posimai-sc-scores', JSON.stringify(this.scores)); }catch(e){}
+      try{ localStorage.setItem('posimai-sc-wrong', JSON.stringify(this.wrongUnits)); }catch(e){}
+      if(blob && blob.currentUnitId){
+        const u = this.allUnits().find(x => x.id === blob.currentUnitId);
+        if(u) this.currentUnit = u;
+      }
+      this.syncStateAt = parseInt(String(blob?.stateAt || this.nowTs()), 10) || this.nowTs();
+      try{ localStorage.setItem('posimai-sc-state-at', String(this.syncStateAt)); }catch(e){}
+      this.syncUnitToUrl();
+    },
+    markStateChanged(){
+      this.syncStateAt = this.nowTs();
+      try{ localStorage.setItem('posimai-sc-state-at', String(this.syncStateAt)); }catch(e){}
+      if(this.syncEnabled) this.scheduleCloudPush();
+    },
+    get syncHeader(){
+      const token = (localStorage.getItem('posimai_token') || '').trim() || (this.syncToken || '').trim();
+      return token ? { Authorization: 'Bearer ' + token } : null;
+    },
+    async pullCloudState(){
+      const hdr = this.syncHeader;
+      if(!hdr){
+        this.syncEnabled = false;
+        this.syncStatus = '同期キー未設定';
+        return;
+      }
+      this.syncBusy = true;
+      this.syncStatus = '同期を確認中...';
+      this.syncLastError = '';
+      try{
+        const res = await fetch(`${API_BASE}/app-state/${APP_ID}`, { headers: hdr });
+        if(res.status===404){
+          this.syncEnabled = true;
+          this.syncStatus = 'クラウド初期化前（この端末の状態を保存できます）';
+          return;
+        }
+        if(!res.ok) throw new Error('HTTP '+res.status);
+        const data = await res.json();
+        const remoteState = data?.state || {};
+        const remoteAt = parseInt(String(remoteState?.stateAt || 0), 10) || 0;
+        this.syncRemoteAt = remoteAt;
+        if(remoteAt > (this.syncStateAt || 0)){
+          this.applyStateBlob(remoteState);
+          this.syncStatus = 'クラウドから最新状態を復元';
+        } else if(remoteAt > 0){
+          this.syncStatus = 'この端末の状態が最新';
+        } else {
+          this.syncStatus = 'クラウド初期化前（この端末の状態を保存できます）';
+        }
+      }catch(e){
+        this.syncLastError = String(e?.message || e || '同期失敗');
+        this.syncStatus = '同期エラー';
+      }finally{
+        this.syncBusy = false;
+      }
+    },
+    async pushCloudState(){
+      const hdr = this.syncHeader;
+      if(!hdr || !this.syncEnabled) return;
+      this.syncBusy = true;
+      this.syncStatus = 'クラウドへ保存中...';
+      this.syncLastError = '';
+      try{
+        const payload = this.localStateBlob;
+        const res = await fetch(`${API_BASE}/app-state/${APP_ID}`, {
+          method:'PUT',
+          headers:{ 'Content-Type':'application/json', ...hdr },
+          body: JSON.stringify({ state: payload })
+        });
+        if(!res.ok) throw new Error('HTTP '+res.status);
+        this.syncRemoteAt = payload.stateAt;
+        this.syncStatus = 'クラウド同期済み';
+      }catch(e){
+        this.syncLastError = String(e?.message || e || '同期失敗');
+        this.syncStatus = '同期エラー';
+      }finally{
+        this.syncBusy = false;
+      }
+    },
+    scheduleCloudPush(){
+      if(this.syncTimer) clearTimeout(this.syncTimer);
+      this.syncTimer = setTimeout(()=>{ this.pushCloudState().catch(()=>{}); }, 800);
+    },
+    enableSyncWithInput(){
+      const token = (this.syncToken || '').trim();
+      if(!token){
+        this.syncStatus = '同期キー未設定';
+        return;
+      }
+      localStorage.setItem(SYNC_KEY_LS, token);
+      this.syncEnabled = true;
+      this.pullCloudState().catch(()=>{});
+    },
+    async syncNow(){
+      if(!this.syncEnabled){
+        this.syncStatus = '同期キー未設定';
+        return;
+      }
+      await this.pushCloudState();
+      await this.pullCloudState();
+    },
 
     goHome(){
       this.currentUnit=null;
@@ -194,6 +337,7 @@ document.addEventListener('alpine:init', () => {
       this.examQuestions=[];
       this.examIdx=0;
       this.examQuizState={};
+      this.markStateChanged();
       this.syncUnitToUrl();
       this.$nextTick(()=>{ if(window.lucide) lucide.createIcons(); });
     },
@@ -251,6 +395,7 @@ document.addEventListener('alpine:init', () => {
       if(!this.currentUnit) return;
       this.progress[this.currentUnit.id]=true;
       localStorage.setItem('posimai-sc-progress',JSON.stringify(this.progress));
+      this.markStateChanged();
     },
     bestScore(id){
       const s=this.scores[id];
@@ -269,6 +414,7 @@ document.addEventListener('alpine:init', () => {
       if(!prev||correct>prev.best){
         this.scores[id]={best:correct,total};
         localStorage.setItem('posimai-sc-scores',JSON.stringify(this.scores));
+        this.markStateChanged();
       }
     },
     get freqBadgeCls(){
@@ -295,6 +441,7 @@ document.addEventListener('alpine:init', () => {
       this.quizState={};
       this.conceptExpanded=true;
       this.stepMode=false;
+      this.markStateChanged();
       this.syncUnitToUrl();
       this.$nextTick(()=>{
         if(window.lucide) lucide.createIcons();
@@ -317,12 +464,14 @@ document.addEventListener('alpine:init', () => {
         if(!this.progress[uid]){
           this.progress[uid]=true;
           try{ localStorage.setItem('posimai-sc-progress',JSON.stringify(this.progress)); }catch(e){}
+          this.markStateChanged();
         }
       } else {
         this.wrongUnits[uid]=(this.wrongUnits[uid]||0)+1;
       }
       try{ localStorage.setItem('posimai-sc-wrong',JSON.stringify(this.wrongUnits)); }catch(e){}
       this.wrongUnits={...this.wrongUnits};
+      this.markStateChanged();
     },
     get weakUnits(){
       return this.allUnits().filter(u=>this.wrongUnits[u.id]>0)
@@ -637,6 +786,7 @@ document.addEventListener('alpine:init', () => {
         delete this.wrongUnits[unit.id];
         localStorage.setItem('posimai-sc-wrong',JSON.stringify(this.wrongUnits));
         this.wrongUnits={...this.wrongUnits};
+        this.markStateChanged();
       }
       if(this.weakDrillUnitIdx<this.weakDrillUnits.length-1){
         this.weakDrillUnitIdx++;
diff --git a/posimai-sc/sw.js b/posimai-sc/sw.js
index 10186ab7..6b56992c 100644
--- a/posimai-sc/sw.js
+++ b/posimai-sc/sw.js
@@ -1,5 +1,5 @@
 // posimai-sc SW — same-origin の静的資産のみキャッシュ（CDN は対象外）
-const CACHE = 'posimai-sc-v4';
+const CACHE = 'posimai-sc-v5';
 const STATIC = [
   '/',
   '/index.html',
diff --git a/server.js b/server.js
index 14697ff6..98d1497b 100644
--- a/server.js
+++ b/server.js
@@ -842,6 +842,9 @@ async function togetherEnsureMemberForShare(pool, res, shareId, username, jwtUse
     }
 }
 
+const APP_STATE_DIR = path.join(__dirname, 'app-state');
+if (!fs.existsSync(APP_STATE_DIR)) fs.mkdirSync(APP_STATE_DIR, { recursive: true });
+
 // ── ルーター ──────────────────────────────
 function buildRouter() {
     const r = express.Router();
@@ -897,6 +900,51 @@ function buildRouter() {
         res.json({ ok: true, userId: req.userId });
     });
 
+    // ── App state sync (cross-device resume) ──────────────────────────
+    r.get('/app-state/:appId', authMiddleware, (req, res) => {
+        const appId = String(req.params.appId || '').trim();
+        if (!/^[a-z0-9-]{2,40}$/.test(appId)) {
+            return res.status(400).json({ error: 'invalid_app_id' });
+        }
+        const userDir = path.join(APP_STATE_DIR, req.userId);
+        const file = path.join(userDir, `${appId}.json`);
+        if (!fs.existsSync(file)) return res.status(404).json({ error: 'not_found' });
+        try {
+            const raw = fs.readFileSync(file, 'utf8');
+            const parsed = JSON.parse(raw);
+            return res.json({ ok: true, appId, userId: req.userId, state: parsed.state || {} });
+        } catch (e) {
+            console.error('[AppState] read error:', e.message);
+            return res.status(500).json({ error: 'read_failed' });
+        }
+    });
+
+    r.put('/app-state/:appId', authMiddleware, (req, res) => {
+        const appId = String(req.params.appId || '').trim();
+        if (!/^[a-z0-9-]{2,40}$/.test(appId)) {
+            return res.status(400).json({ error: 'invalid_app_id' });
+        }
+        const state = req.body?.state;
+        if (!state || typeof state !== 'object' || Array.isArray(state)) {
+            return res.status(400).json({ error: 'invalid_state' });
+        }
+        // 安全上限: 100KB
+        const payload = JSON.stringify({ appId, userId: req.userId, state, updatedAt: new Date().toISOString() });
+        if (Buffer.byteLength(payload, 'utf8') > 100 * 1024) {
+            return res.status(413).json({ error: 'state_too_large' });
+        }
+        const userDir = path.join(APP_STATE_DIR, req.userId);
+        const file = path.join(userDir, `${appId}.json`);
+        try {
+            if (!fs.existsSync(userDir)) fs.mkdirSync(userDir, { recursive: true });
+            fs.writeFileSync(file, payload, 'utf8');
+            return res.json({ ok: true, appId, updatedAt: new Date().toISOString() });
+        } catch (e) {
+            console.error('[AppState] write error:', e.message);
+            return res.status(500).json({ error: 'write_failed' });
+        }
+    });
+
     // ── Auth: Magic Link ─────────────────────────────────────────────
 
     // POST /api/auth/magic-link/send