diff --git a/viewer/index.html b/viewer/index.html
index a40b905..57f8fd3 100644
--- a/viewer/index.html
+++ b/viewer/index.html
@@ -783,7 +783,7 @@ async function loadDate(date) {
 
     for (const { mission, dives } of missionDives) {
       for (const dive of dives) {
-        allFetches.push(loadDiveData(mission.id, dive.id));
+        allFetches.push(loadDiveData(mission.id, dive.id, date));
         totalShip += dive.ship_session_count || 0;
         totalSub  += dive.sub_session_count || 0;
       }
@@ -848,71 +848,75 @@ async function loadDate(date) {
   }
 }
 
-async function loadDiveData(missionId, diveId) {
+async function loadDiveData(missionId, diveId, filterDate) {
   try {
     const sResp = await fetch(`${API}/api/dives/${missionId}/${diveId}/sessions`);
     const sessions = await sResp.json();
-    const sessionFetches = [];
 
-    // Ship sessions
-    if (sessions.ship) {
-      sessions.ship.forEach(sess => {
-        sessionFetches.push(loadShipSession(missionId, diveId, sess.id));
-      });
-    }
-    // Sub sessions
-    if (sessions.sub) {
-      sessions.sub.forEach(sess => {
-        sessionFetches.push(loadSubSession(missionId, diveId, sess.id));
-      });
-    }
-    await Promise.all(sessionFetches);
+    // T3 FIX: filter ship sessions by date if provided (session.start = "YYYY-MM-DD_HH-MM-SS")
+    const shipSessions = (sessions.ship || []).filter(sess => {
+      if (!filterDate) return true;
+      // sess.start: "2026-04-17_07-43-23" → compare first 10 chars "2026-04-17" to filterDate
+      return !sess.start || sess.start.slice(0, 10) === filterDate;
+    });
+
+    // Phase 1: track-only fetches (needed for map polylines) — batch by 4
+    const trackFetches = shipSessions.map(sess =>
+      fetchShipTrack(missionId, diveId, sess.id)
+    );
+    await _batchedAll(trackFetches, 4);
+
+    // Phase 2: series + sub sessions in background (charts data)
+    const seriesFetches = [
+      ...shipSessions.map(sess => fetchShipSeries(missionId, diveId, sess.id)),
+      ...(sessions.sub || []).map(sess => loadSubSession(missionId, diveId, sess.id)),
+    ];
+    await _batchedAll(seriesFetches, 4);
   } catch(e) { console.warn('loadDiveData error', diveId, e); }
 }
 
-async function loadShipSession(missionId, diveId, sessionId) {
-  // Parallel fetch: track + series with 20s timeout each — neither blocks the other
-  const [trackResult, seriesResult] = await Promise.allSettled([
-    fetch(`${API}/api/ship/${missionId}/${diveId}/${sessionId}/track`,
-      { signal: AbortSignal.timeout(20000) }),
-    fetch(`${API}/api/ship/${missionId}/${diveId}/${sessionId}/series`,
-      { signal: AbortSignal.timeout(20000) }),
-  ]);
-  if (trackResult.status === 'fulfilled' && trackResult.value.ok) {
-    try {
-      const d = await trackResult.value.json();
-      const pts = (d.points||[]).map(p => ({
-        t_ms: isoToMs(p.t), lat: p.lat, lon: p.lon,
-        heading: p.heading || null, source: sessionId
-      }));
-      allPoints.push(...pts);
-    } catch(e) { console.warn('loadShipSession track json error', sessionId, e); }
-  } else {
-    console.warn('loadShipSession track timeout/fail', sessionId,
-      trackResult.status === 'rejected' ? trackResult.reason.name : trackResult.value?.status);
-  }
-  if (seriesResult.status === 'fulfilled' && seriesResult.value.ok) {
-    try {
-      const d = await seriesResult.value.json();
-      const motorKeys = Object.keys(d).filter(k => /^M\d+$/.test(k));
-      motorKeys.forEach((k, i) => {
-        const pts = d[k];
-        if (!pts || !pts.length) return;
-        pwmUsvTraces.push({
-          x: pts.map(p => new Date(isoToMs(p.t))),
-          y: pts.map(p => p.v),
-          name: k,
-          type: 'scatter', mode: 'lines',
-          line: { color: COLORS[i % COLORS.length], width: 1 },
-        });
-      });
-    } catch(e) { console.warn('loadShipSession series json error', sessionId, e); }
-  } else {
-    console.warn('loadShipSession series timeout/fail', sessionId,
-      seriesResult.status === 'rejected' ? seriesResult.reason.name : seriesResult.value?.status);
+// Run an array of promise-factories in batches of size n
+async function _batchedAll(fns, n) {
+  for (let i = 0; i < fns.length; i += n) {
+    await Promise.all(fns.slice(i, i + n));
   }
 }
 
+async function fetchShipTrack(missionId, diveId, sessionId) {
+  try {
+    const resp = await fetch(`${API}/api/ship/${missionId}/${diveId}/${sessionId}/track`,
+      { signal: AbortSignal.timeout(20000) });
+    if (!resp.ok) { console.warn('fetchShipTrack fail', sessionId, resp.status); return; }
+    const d = await resp.json();
+    const pts = (d.points||[]).map(p => ({
+      t_ms: isoToMs(p.t), lat: p.lat, lon: p.lon,
+      heading: p.heading || null, source: sessionId
+    }));
+    allPoints.push(...pts);
+  } catch(e) { console.warn('fetchShipTrack error', sessionId, e.name); }
+}
+
+async function fetchShipSeries(missionId, diveId, sessionId) {
+  try {
+    const resp = await fetch(`${API}/api/ship/${missionId}/${diveId}/${sessionId}/series`,
+      { signal: AbortSignal.timeout(20000) });
+    if (!resp.ok) return;
+    const d = await resp.json();
+    const motorKeys = Object.keys(d).filter(k => /^M\d+$/.test(k));
+    motorKeys.forEach((k, i) => {
+      const pts = d[k];
+      if (!pts || !pts.length) return;
+      pwmUsvTraces.push({
+        x: pts.map(p => new Date(isoToMs(p.t))),
+        y: pts.map(p => p.v),
+        name: k, type: 'scatter', mode: 'lines',
+        line: { color: COLORS[i % COLORS.length], width: 1 },
+      });
+    });
+  } catch(e) { console.warn('fetchShipSeries error', sessionId, e.name); }
+}
+
+
 async function loadSubSession(missionId, diveId, sessionId) {
   // Both usbl_track and series can hang — use parallel with timeout, non-blocking
   const [usblResult, seriesResult] = await Promise.allSettled([
@@ -1287,6 +1291,8 @@ async function loadSortieData(sortieId) {
     prog.textContent = 'Chargement AUV…';
     await loadAuvTabs(sortieId);
     prog.textContent = `${sortieId} chargé`;
+    // POLYLINE FIX: ensure map trail is drawn if allPoints already loaded from datebar
+    if (allPoints.length > 0) applyTrailAndCursor();
   } catch(e) {
     prog.textContent = `Erreur: ${e.message}`;
   }