diff --git a/TODO_NEXT_STEPS.txt b/TODO_NEXT_STEPS.txt
index ea438ca..0e52db1 100644
--- a/TODO_NEXT_STEPS.txt
+++ b/TODO_NEXT_STEPS.txt
@@ -4,6 +4,7 @@
 ================================================================================
 
 【已完成】
+   - V10.201 強化 `/observability/ppt_audit_history` 線上預覽可診斷性：產線清單不觸發轉檔即可顯示 PDF 預覽快取狀態，Pipeline Health、Preview Workbench 與已產檔案表同步標記「PDF 快取 / 首次轉檔」。
    - V10.199 讓 `/observability/ppt_audit_history` Action Queue 可直接處理異常：待補齊與異常優先項目新增單一報表「重跑」按鈕，透過既有非阻塞背景產線排入指定 report_type。
    - V10.197 強化 `/observability/ppt_audit_history` Action Queue：新增「異常優先」lane，將產出失敗、PPTX 檔案異常、視覺 QA 失敗拉到最前面，並顯示錯誤訊息與可預覽入口。
    - V10.196 補 `/observability/ppt_audit_history` Action Queue：把待補齊、可預覽、視覺 QA、DB 寫入集中成工作隊列，讓使用者不用在多張卡與表格間找下一個處理點。
diff --git a/config.py b/config.py
index f428956..3e6a0f7 100644
--- a/config.py
+++ b/config.py
@@ -320,7 +320,7 @@ YOUTUBE_API_KEY = os.getenv('YOUTUBE_API_KEY', '')
 # ==========================================
 # 系統版本與路徑
 # ==========================================
-SYSTEM_VERSION = "V10.200"
+SYSTEM_VERSION = "V10.201"
 LOG_FILE_PATH = os.path.join(BASE_DIR, 'logs/system.log')
 public_url = PUBLIC_URL  # 用於模板顯示
 
diff --git a/routes/admin_observability_routes.py b/routes/admin_observability_routes.py
index a765250..cc1fba8 100644
--- a/routes/admin_observability_routes.py
+++ b/routes/admin_observability_routes.py
@@ -2255,6 +2255,10 @@ def _build_ppt_pipeline_view(files, auto_generation, audit_stats, generation_run
     missing_count = _as_int(auto_generation.get('missing_count'))
     coverage_pct = round((ready_count / total_count * 100), 1) if total_count else 0
     valid_preview_count = sum(1 for item in files if item.get('file_exists') and item.get('is_valid_ppt'))
+    cached_preview_count = sum(
+        1 for item in files
+        if item.get('file_exists') and item.get('is_valid_ppt') and item.get('preview_cache_ready')
+    )
     broken_file_count = sum(1 for item in files if item.get('file_exists') and not item.get('is_valid_ppt'))
     db_backed_count = sum(1 for item in files if item.get('source') in ('database', 'both'))
     run_error_count = sum(1 for item in generation_runs if item.get('status') == 'error')
@@ -2332,7 +2336,7 @@ def _build_ppt_pipeline_view(files, auto_generation, audit_stats, generation_run
             'icon': 'desktop',
             'label': '線上預覽',
             'value': f'{valid_preview_count} 份',
-            'meta': f'{db_backed_count} 份含 DB 紀錄',
+            'meta': f'{cached_preview_count} 份 PDF 快取',
             'detail': latest_file.get('name') or '尚無可預覽檔案',
             'status': 'error' if broken_file_count else ('ready' if valid_preview_count else 'planned'),
         },
@@ -2435,8 +2439,12 @@ def _build_ppt_pipeline_view(files, auto_generation, audit_stats, generation_run
                 {
                     'title': item.get('name') or '未命名檔案',
                     'meta': item.get('mtime') or '時間未知',
-                    'detail': f"{item.get('size_kb') if item.get('size_kb') is not None else '—'} KB · {item.get('source') or 'filesystem'}",
-                    'status_label': '線上預覽',
+                    'detail': (
+                        f"{item.get('size_kb') if item.get('size_kb') is not None else '—'} KB · "
+                        f"{item.get('source') or 'filesystem'} · "
+                        f"{'PDF 已快取' if item.get('preview_cache_ready') else '開啟時轉檔'}"
+                    ),
+                    'status_label': 'PDF 快取' if item.get('preview_cache_ready') else '線上預覽',
                     'filename': item.get('name'),
                 }
                 for item in preview_items[:4]
@@ -2487,6 +2495,7 @@ def _build_ppt_pipeline_view(files, auto_generation, audit_stats, generation_run
         'missing_count': missing_count,
         'coverage_pct': coverage_pct,
         'valid_preview_count': valid_preview_count,
+        'cached_preview_count': cached_preview_count,
         'broken_file_count': broken_file_count,
         'db_backed_count': db_backed_count,
         'run_error_count': run_error_count,
@@ -2578,6 +2587,31 @@ def ppt_audit_history():
         except Exception as e:
             return False, f'檢查失敗：{str(e)[:60]}'
 
+    def _guess_report_type(filename: str) -> str:
+        for opt in report_type_options:
+            prefix = opt.get('prefix')
+            if prefix and prefix != 'all' and filename.startswith(prefix):
+                return opt.get('key') or ''
+        return report_type if report_type != 'all' else ''
+
+    def _preview_cache_payload(file_path: str):
+        payload = {
+            'preview_cache_ready': False,
+            'preview_cache_size_kb': None,
+            'preview_cache_mtime': '',
+        }
+        try:
+            from services.ppt_preview_service import get_ppt_preview_cache_info
+
+            info = get_ppt_preview_cache_info(file_path)
+            payload['preview_cache_ready'] = bool(info.cache_exists)
+            payload['preview_cache_size_kb'] = info.cache_size_kb
+            if info.cache_mtime_ts:
+                payload['preview_cache_mtime'] = datetime.fromtimestamp(info.cache_mtime_ts).strftime('%Y-%m-%d %H:%M')
+        except Exception:
+            logger.debug("PPT preview cache state unavailable", exc_info=True)
+        return payload
+
     try:
         if not os.path.isdir(reports_dir):
             error = f'{reports_dir} 目錄不存在'
@@ -2604,8 +2638,10 @@ def ppt_audit_history():
                             'mtime_ts': mtime,
                             'file_exists': True,
                             'file_path': full,
+                            'report_type': _guess_report_type(f),
                             'is_valid_ppt': is_valid,
                             'file_error': check_msg,
+                            **_preview_cache_payload(full),
                         }
                 except OSError:
                     continue
@@ -2659,6 +2695,7 @@ def ppt_audit_history():
                             'report_type': rpt_type,
                             'is_valid_ppt': is_valid,
                             'file_error': None if exists else check_msg,
+                            **(_preview_cache_payload(candidate_path) if exists else {}),
                         }
                 finally:
                     session.close()
diff --git a/services/ppt_preview_service.py b/services/ppt_preview_service.py
index dba0875..9a9b5bd 100644
--- a/services/ppt_preview_service.py
+++ b/services/ppt_preview_service.py
@@ -24,6 +24,14 @@ class PPTPreviewResult:
     error: str | None = None
 
 
+@dataclass(frozen=True)
+class PPTPreviewCacheInfo:
+    pdf_path: str | None = None
+    cache_exists: bool = False
+    cache_size_kb: float | None = None
+    cache_mtime_ts: float | None = None
+
+
 def find_libreoffice_binary() -> str | None:
     return shutil.which("libreoffice") or shutil.which("soffice")
 
@@ -37,6 +45,30 @@ def _preview_cache_path(pptx_path: Path, cache_dir: Path) -> Path:
     return cache_dir / f"{safe_stem}_{cache_key}.pdf"
 
 
+def get_ppt_preview_cache_info(
+    pptx_path: str | os.PathLike[str],
+    *,
+    cache_dir: str | os.PathLike[str] | None = None,
+) -> PPTPreviewCacheInfo:
+    """只讀取預期 PDF 快取狀態，不啟動 LibreOffice 轉檔。"""
+    source = Path(pptx_path)
+    if not source.is_file() or source.suffix.lower() != ".pptx":
+        return PPTPreviewCacheInfo()
+
+    target_dir = Path(cache_dir or os.getenv("PPT_PREVIEW_CACHE_DIR", "/app/data/ppt_previews"))
+    target_pdf = _preview_cache_path(source, target_dir)
+    if not target_pdf.is_file() or target_pdf.stat().st_size <= 0:
+        return PPTPreviewCacheInfo(pdf_path=str(target_pdf), cache_exists=False)
+
+    stat = target_pdf.stat()
+    return PPTPreviewCacheInfo(
+        pdf_path=str(target_pdf),
+        cache_exists=True,
+        cache_size_kb=round(stat.st_size / 1024, 1),
+        cache_mtime_ts=stat.st_mtime,
+    )
+
+
 def build_ppt_preview(
     pptx_path: str | os.PathLike[str],
     *,
diff --git a/templates/admin/ppt_audit_history.html b/templates/admin/ppt_audit_history.html
index e03f977..f695b88 100644
--- a/templates/admin/ppt_audit_history.html
+++ b/templates/admin/ppt_audit_history.html
@@ -110,6 +110,9 @@
           <span>{{ f.size_kb if f.size_kb is not none else '—' }} KB</span>
           <span>{{ f.source }}</span>
           {% if f.file_exists and f.is_valid_ppt %}<span class="status-good">可預覽</span>{% else %}<span class="status-bad">需回補</span>{% endif %}
+          {% if f.file_exists and f.is_valid_ppt %}
+            {% if f.preview_cache_ready %}<span class="status-blue">PDF 快取</span>{% else %}<span class="status-warn">首次轉檔</span>{% endif %}
+          {% endif %}
         </div>
         <div class="ppt-file-actions">
           {% if f.file_exists and f.is_valid_ppt %}
@@ -136,6 +139,7 @@
       <div class="ppt-health-facts">
         <span><strong>{{ pipeline_view.ready_count }}/{{ pipeline_view.total_count }}</strong> 定義覆蓋</span>
         <span><strong>{{ pipeline_view.valid_preview_count }}</strong> 份可預覽</span>
+        <span><strong>{{ pipeline_view.cached_preview_count }}</strong> 份 PDF 快取</span>
         <span><strong>{{ pipeline_view.audit_total }}</strong> 筆視覺 QA</span>
       </div>
     </div>
@@ -417,6 +421,17 @@
                   {% if f.file_error %}
                   <div><small class="text-muted">{{ f.file_error }}</small></div>
                   {% endif %}
+                  {% if f.file_exists and f.is_valid_ppt %}
+                  <div>
+                    <small class="{{ 'status-blue' if f.preview_cache_ready else 'status-warn' }}">
+                      {% if f.preview_cache_ready %}
+                        PDF 預覽快取已建立{% if f.preview_cache_mtime %} · {{ f.preview_cache_mtime }}{% endif %}
+                      {% else %}
+                        PDF 預覽尚未快取，首次開啟會自動轉檔
+                      {% endif %}
+                    </small>
+                  </div>
+                  {% endif %}
                 </td>
                 <td>
                   <div class="ppt-file-actions">
diff --git a/tests/test_admin_observability_routes.py b/tests/test_admin_observability_routes.py
index 43ebfa6..a533dfb 100644
--- a/tests/test_admin_observability_routes.py
+++ b/tests/test_admin_observability_routes.py
@@ -256,12 +256,19 @@ def test_ppt_audit_history_shows_ppt_schedule_and_db_runs(client, monkeypatch):
 def test_ppt_audit_history_shows_recent_preview_workbench(client, monkeypatch, tmp_path):
     """有檔案時，頁面上方要先給可預覽簡報入口。"""
     import zipfile
+    from pathlib import Path
+    from services import ppt_preview_service as preview_svc
 
     reports_dir = tmp_path / 'reports'
+    cache_dir = tmp_path / 'preview-cache'
     reports_dir.mkdir()
     pptx = reports_dir / 'ocbot_daily_20260517.pptx'
     with zipfile.ZipFile(pptx, 'w') as zf:
         zf.writestr('[Content_Types].xml', '<Types></Types>')
+    monkeypatch.setenv('PPT_PREVIEW_CACHE_DIR', str(cache_dir))
+    cache_info = preview_svc.get_ppt_preview_cache_info(pptx)
+    Path(cache_info.pdf_path).parent.mkdir(parents=True, exist_ok=True)
+    Path(cache_info.pdf_path).write_bytes(b'%PDF-1.4\n')
 
     monkeypatch.setenv('REPORTS_DIR', str(reports_dir))
 
@@ -272,6 +279,8 @@ def test_ppt_audit_history_shows_recent_preview_workbench(client, monkeypatch, t
     assert '最近可預覽簡報' in html
     assert 'ocbot_daily_20260517.pptx' in html
     assert '線上預覽' in html
+    assert 'PDF 快取' in html
+    assert '1</strong> 份 PDF 快取' in html
 
 
 def test_ppt_audit_file_view_renders_online_preview(client, monkeypatch, tmp_path):
diff --git a/tests/test_ppt_auto_generation_service.py b/tests/test_ppt_auto_generation_service.py
index 96640d6..c27258f 100644
--- a/tests/test_ppt_auto_generation_service.py
+++ b/tests/test_ppt_auto_generation_service.py
@@ -188,3 +188,23 @@ def test_ppt_preview_reports_missing_converter(monkeypatch, tmp_path):
 
     assert result.ok is False
     assert "LibreOffice" in (result.error or "")
+
+
+def test_ppt_preview_cache_info_is_read_only(tmp_path):
+    from pathlib import Path
+    from services import ppt_preview_service as svc
+
+    pptx = tmp_path / "demo.pptx"
+    pptx.write_bytes(b"fake pptx")
+    cache_dir = tmp_path / "cache"
+
+    miss = svc.get_ppt_preview_cache_info(pptx, cache_dir=cache_dir)
+    assert miss.pdf_path
+    assert miss.cache_exists is False
+
+    Path(miss.pdf_path).parent.mkdir(parents=True, exist_ok=True)
+    Path(miss.pdf_path).write_bytes(b"%PDF-1.4\n")
+
+    hit = svc.get_ppt_preview_cache_info(pptx, cache_dir=cache_dir)
+    assert hit.cache_exists is True
+    assert hit.cache_size_kb is not None
diff --git a/web/static/css/page-ppt-audit-history.css b/web/static/css/page-ppt-audit-history.css
index 639611c..f2e418c 100644
--- a/web/static/css/page-ppt-audit-history.css
+++ b/web/static/css/page-ppt-audit-history.css
@@ -173,6 +173,15 @@
   font-size: var(--momo-text-caption, 12px);
 }
 
+.ppt-deck-facts {
+  justify-content: flex-start;
+  flex-wrap: wrap;
+}
+
+.ppt-deck-facts span {
+  min-height: 22px;
+}
+
 .ppt-deck-card h3 {
   margin: var(--momo-space-2, 8px) 0;
   color: var(--obs-ink);
diff --git a/web/static/css/page-ppt-preview.css b/web/static/css/page-ppt-preview.css
index 9ec13cd..16e4fee 100644
--- a/web/static/css/page-ppt-preview.css
+++ b/web/static/css/page-ppt-preview.css
@@ -29,7 +29,7 @@
   margin: var(--momo-space-2, 8px) 0 var(--momo-space-1, 4px);
   color: var(--obs-ink);
   font-family: var(--momo-font-display, "Inter", "Noto Sans TC", system-ui, sans-serif);
-  font-size: clamp(22px, 2vw, 30px);
+  font-size: var(--momo-text-headline, 22px);
   line-height: var(--momo-line-height-tight, 1.08);
   letter-spacing: 0;
   overflow-wrap: anywhere;