diff --git a/pipeline_runner/main.py b/pipeline_runner/main.py
index 68a3de5..a78905d 100644
--- a/pipeline_runner/main.py
+++ b/pipeline_runner/main.py
@@ -1,6 +1,7 @@
 import asyncio
 import gzip
 import json
+import time
 from pathlib import Path
 from typing import AsyncGenerator
 
@@ -9,7 +10,7 @@ from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse, StreamingResponse
 
 from .config import OUTPUT_DIR
-from .runner import run_pipeline, scan_sorties
+from .runner import run_pipeline, scan_sorties, scan_sorties_local
 
 app = FastAPI(title="COSMA Pipeline Runner")
 app.add_middleware(CORSMiddleware, allow_origins=["*"], allow_methods=["*"], allow_headers=["*"])
@@ -17,10 +18,51 @@ app.add_middleware(CORSMiddleware, allow_origins=["*"], allow_methods=["*"], all
 # Active pipeline jobs: sortie_id → asyncio.Queue
 _jobs: dict[str, asyncio.Queue] = {}
 
+# Cache sorties avec TTL 10min
+_sorties_cache: list | None = None
+_sorties_cache_ts: float = 0.0
+_SORTIES_TTL = 600.0  # 10 minutes
+_sorties_refresh_lock: asyncio.Lock | None = None
+
+
+def _get_lock() -> asyncio.Lock:
+    global _sorties_refresh_lock
+    if _sorties_refresh_lock is None:
+        _sorties_refresh_lock = asyncio.Lock()
+    return _sorties_refresh_lock
+
+
+async def _refresh_sorties_cache() -> None:
+    """Refresh cache in background (holds lock to avoid parallel rclone calls)."""
+    global _sorties_cache, _sorties_cache_ts
+    lock = _get_lock()
+    async with lock:
+        # Double-check after acquiring lock
+        if time.monotonic() - _sorties_cache_ts < _SORTIES_TTL:
+            return
+        result = await asyncio.to_thread(scan_sorties)
+        _sorties_cache = result
+        _sorties_cache_ts = time.monotonic()
+
 
 @app.get("/sorties")
 async def list_sorties():
-    return await scan_sorties()
+    global _sorties_cache, _sorties_cache_ts
+    now = time.monotonic()
+    if _sorties_cache is None:
+        # Premier appel: bloquant (cache vide)
+        await _refresh_sorties_cache()
+    elif now - _sorties_cache_ts >= _SORTIES_TTL:
+        # Cache périmé: retourne le cache, refresh en arrière-plan
+        asyncio.create_task(_refresh_sorties_cache())
+    return _sorties_cache or []
+
+
+@app.get("/sorties/local")
+async def list_sorties_local():
+    """Scan /data/sorties local (NAS, instantané) sans rclone."""
+    sorties = await asyncio.to_thread(scan_sorties_local)
+    return sorties
 
 
 @app.post("/run/{sortie_id:path}")
diff --git a/pipeline_runner/runner.py b/pipeline_runner/runner.py
index db70dc3..e9686f3 100644
--- a/pipeline_runner/runner.py
+++ b/pipeline_runner/runner.py
@@ -122,7 +122,7 @@ async def run_pipeline(sortie_id: str, queue: asyncio.Queue) -> None:
 
 
 async def scan_sorties() -> list[dict]:
-    """List available sorties on GDrive via rclone lsd."""
+    """List available sorties on GDrive via rclone lsd (lent ~30s)."""
     result = subprocess.run(
         ["rclone", "lsd", GDRIVE_REMOTE],
         capture_output=True, text=True
@@ -135,3 +135,15 @@ async def scan_sorties() -> list[dict]:
             processed = (OUTPUT_DIR / name / "processed" / "usv.json.gz").exists()
             sorties.append({"id": name, "processed": processed})
     return sorties
+
+
+def scan_sorties_local() -> list[dict]:
+    """List sorties already synced locally in OUTPUT_DIR (instantané, pas rclone)."""
+    if not OUTPUT_DIR.exists():
+        return []
+    sorties = []
+    for d in sorted(OUTPUT_DIR.iterdir()):
+        if d.is_dir():
+            processed = (d / "processed" / "usv.json.gz").exists()
+            sorties.append({"id": d.name, "processed": processed})
+    return sorties
diff --git a/viewer/index.html b/viewer/index.html
index c6b4e0c..ee236f6 100644
--- a/viewer/index.html
+++ b/viewer/index.html
@@ -1121,29 +1121,60 @@ async function loadSortieData(sortieId) {
   }
 }
 
-async function loadSorties() {
-  try {
-    const resp = await fetch(`${API2}/sorties`);
-    if (!resp.ok) return;
-    const sorties = await resp.json();
-    const sel = document.getElementById('sortie-select');
-    sorties.forEach(s => {
-      const opt = document.createElement('option');
-      opt.value = s.id;
-      opt.textContent = s.id + (s.processed ? ' ✓' : '');
-      sel.appendChild(opt);
-    });
-    sel.addEventListener('change', () => {
-      const btn = document.getElementById('btn-sync');
-      btn.disabled = !sel.value;
-      if (sel.value) {
-        const opt = sel.options[sel.selectedIndex];
-        if (opt.textContent.includes('✓')) {
-          loadSortieData(sel.value);
-        }
+function _wireSortieSelect() {
+  const sel = document.getElementById('sortie-select');
+  // Evite double-binding si appelé plusieurs fois
+  if (sel._wired) return;
+  sel._wired = true;
+  sel.addEventListener('change', () => {
+    const btn = document.getElementById('btn-sync');
+    btn.disabled = !sel.value;
+    if (sel.value) {
+      const opt = sel.options[sel.selectedIndex];
+      if (opt.textContent.includes('✓')) {
+        loadSortieData(sel.value);
       }
+    }
+  });
+}
+
+function _populateSortieSelect(sorties) {
+  const sel = document.getElementById('sortie-select');
+  // Vider sauf première option placeholder
+  while (sel.options.length > 1) sel.remove(1);
+  if (!sorties || !sorties.length) {
+    sel.options[0].textContent = '— Aucune sortie —';
+    return;
+  }
+  sel.options[0].textContent = '— Sortie —';
+  sorties.forEach(s => {
+    const opt = document.createElement('option');
+    opt.value = s.id;
+    opt.textContent = s.id + (s.processed ? ' ✓' : '');
+    sel.appendChild(opt);
+  });
+  _wireSortieSelect();
+}
+
+function loadSorties() {
+  const sel = document.getElementById('sortie-select');
+  sel.options[0].textContent = 'Sorties: chargement…';
+
+  const controller = new AbortController();
+  const timeoutId = setTimeout(() => controller.abort(), 5000);
+
+  fetch(`${API2}/sorties`, { signal: controller.signal })
+    .then(resp => {
+      clearTimeout(timeoutId);
+      if (!resp.ok) throw new Error('HTTP ' + resp.status);
+      return resp.json();
+    })
+    .then(sorties => { _populateSortieSelect(sorties); })
+    .catch(e => {
+      clearTimeout(timeoutId);
+      sel.options[0].textContent = '— Pipeline indisponible —';
+      console.warn('loadSorties:', e.message);
     });
-  } catch(e) { console.warn('pipeline-runner unavailable', e); }
 }
 
 document.getElementById('btn-sync').addEventListener('click', async () => {