diff --git a/php/chronotrack_api/fx_chronotrack_admin.php b/php/chronotrack_api/fx_chronotrack_admin.php
index 63ae9ea..bbc1619 100644
--- a/php/chronotrack_api/fx_chronotrack_admin.php
+++ b/php/chronotrack_api/fx_chronotrack_admin.php
@@ -1453,7 +1453,7 @@ function fxChronotrackApiAdminRenderPageScript($intEveId, $arrConfig, $blnClosed
             url: strAjaxUrl,
             type: 'POST',
             dataType: 'json',
-            timeout: 60000,
+            timeout: 120000,
             data: { a: 'sync_preview', eve_id: intEveId }
         }).done(function (res) {
             if (rejectIfSessionLost(res)) {
@@ -1465,14 +1465,21 @@ function fxChronotrackApiAdminRenderPageScript($intEveId, $arrConfig, $blnClosed
             if (strStatus === 'abort') {
                 return;
             }
-            var strMsg = (strStatus === 'timeout')
-                ? 'Délai dépassé — réessayez Actualiser.'
-                : 'Erreur réseau (preview).';
+            var strMsg;
+            if (strStatus === 'timeout') {
+                strMsg = 'Délai dépassé (preview) — réessayez Actualiser.';
+            } else if (strStatus === 'parsererror') {
+                strMsg = 'Réponse invalide (preview) — souvent un envoi encore en cours ou erreur PHP.';
+            } else if (jqXHR && jqXHR.status) {
+                strMsg = 'Erreur preview HTTP ' + jqXHR.status + ' — réessayez Actualiser.';
+            } else {
+                strMsg = 'Erreur réseau (preview). Si un envoi tourne, attendez la fin puis Actualiser.';
+            }
             if ($status.length) {
                 $status.removeClass('ct-api-push-status--ok ct-api-push-status--todo ct-api-push-status--loading')
                     .html(
                         '<p class="ct-api-push-status__title text-danger mb-1">' + escHtml(strMsg) + '</p>'
-                        + '<p class="ct-api-push-status__hint mb-0 text-muted">Réessayez Actualiser.</p>'
+                        + '<p class="ct-api-push-status__hint mb-0 text-muted">Les derniers compteurs affichés sont conservés.</p>'
                         + '<p id="ct_api_status_refresh_cd" class="small text-muted mb-0 mt-1"></p>'
                     );
             }
@@ -1836,6 +1843,9 @@ function fxChronotrackApiAdminRenderPageScript($intEveId, $arrConfig, $blnClosed
             var blnFatal = false;
 
             blnPushRunning = true;
+            if (xhrPushPreview && xhrPushPreview.readyState !== 4) {
+                xhrPushPreview.abort();
+            }
             $('#ct_api_btn_push, #ct_api_btn_push_full, #ct_api_btn_push_refresh, #ct_api_btn_ct_count, #ct_api_btn_logs').prop('disabled', true);
 
             function renderProgress(intDone, intTot, strExtra) {
@@ -1879,7 +1889,13 @@ function fxChronotrackApiAdminRenderPageScript($intEveId, $arrConfig, $blnClosed
             }
 
             function pushChunk() {
-                renderProgress(intOffset, intTotal, 'lot en cours…');
+                var intLot = Math.floor(intOffset / Math.max(1, intChunk)) + 1;
+                var intLots = Math.max(1, Math.ceil(intTotal / Math.max(1, intChunk)));
+                renderProgress(
+                    intOffset,
+                    intTotal,
+                    'lot ' + intLot + '/' + intLots + ' (POST ' + Math.min(intChunk, intTotal - intOffset) + ')…'
+                );
                 $.ajax({
                     url: strAjaxUrl,
                     type: 'POST',
@@ -1967,7 +1983,7 @@ function fxChronotrackApiAdminRenderPageScript($intEveId, $arrConfig, $blnClosed
                 });
             }
 
-            renderProgress(0, intTotal, 'préparation…');
+            renderProgress(0, intTotal > 0 ? intTotal : 1, 'préparation MS1 (liste + job)…');
             $.ajax({
                 url: strAjaxUrl,
                 type: 'POST',
diff --git a/php/chronotrack_api/fx_chronotrack_sync.php b/php/chronotrack_api/fx_chronotrack_sync.php
index 933c0a7..afc58db 100644
--- a/php/chronotrack_api/fx_chronotrack_sync.php
+++ b/php/chronotrack_api/fx_chronotrack_sync.php
@@ -403,7 +403,7 @@ function fxChronotrackApiSyncGroupBlockedByType(array $tabBlocked) {
 /**
  * Classe les participants MS1 : transférables vs exclus (dossard, sexe, doublons MS1, mapping).
  */
-function fxChronotrackApiSyncClassifyParticipants(array $tabParticipants, array $arrRaceMap, $intCtEventId = 0) {
+function fxChronotrackApiSyncClassifyParticipants(array $tabParticipants, array $arrRaceMap, $intCtEventId = 0, $blnBuildPayloads = true) {
     $tabCandidates = array();
     $tabBlocked = array();
     $tabBibCounts = array();
@@ -560,9 +560,12 @@ function fxChronotrackApiSyncClassifyParticipants(array $tabParticipants, array
             continue;
         }
 
-        $arrPayload = fxChronotrackApiSyncBuildEntryPayload($arrRow, $arrRaceMap, $intCtEventId);
-        if ($arrPayload === null) {
-            continue;
+        $arrPayload = null;
+        if ($blnBuildPayloads) {
+            $arrPayload = fxChronotrackApiSyncBuildEntryPayload($arrRow, $arrRaceMap, $intCtEventId);
+            if ($arrPayload === null) {
+                continue;
+            }
         }
 
         $tabTransferable[] = array(
@@ -630,9 +633,12 @@ function fxChronotrackApiSyncClassifyParticipants(array $tabParticipants, array
             continue;
         }
 
-        $arrPayload = fxChronotrackApiSyncBuildEntryPayload($arrRep, $arrRaceMap, $intCtEventId);
-        if ($arrPayload === null) {
-            continue;
+        $arrPayload = null;
+        if ($blnBuildPayloads) {
+            $arrPayload = fxChronotrackApiSyncBuildEntryPayload($arrRep, $arrRaceMap, $intCtEventId);
+            if ($arrPayload === null) {
+                continue;
+            }
         }
 
         $tabTransferable[] = array(
@@ -2018,7 +2024,8 @@ function fxChronotrackApiSyncBuildPreview($intEveId) {
     $intCtEventId = intval($arrConfig['ct_event_id']);
     $arrRaceMap = fxChronotrackApiRaceMapGetForEvent($intEveId);
     $tabParticipants = fxChronotrackApiSyncLoadMs1Participants($intEveId);
-    $arrClass = fxChronotrackApiSyncClassifyParticipants($tabParticipants, $arrRaceMap, $intCtEventId);
+    // MSIN-4328 — preview rapide : pas de build payloads / entry_notes (seulement compteurs + exclus)
+    $arrClass = fxChronotrackApiSyncClassifyParticipants($tabParticipants, $arrRaceMap, $intCtEventId, false);
 
     $intMs1Total = count($tabParticipants);
     $intTransferable = count($arrClass['transferable']);
@@ -2036,7 +2043,7 @@ function fxChronotrackApiSyncBuildPreview($intEveId) {
         'transferable'           => $intTransferable,
         'blocked_count'          => $arrClass['blocked_count'],
         'blocked_by_type'        => $arrClass['blocked_by_type'],
-        'blocked'                => $arrClass['blocked'],
+        // Pas de liste plate « blocked » (doublon lourd) — l’UI utilise blocked_by_type
         'eligible'               => $intTransferable,
         'skipped_no_race'        => $arrClass['skipped_no_race'],
         'skipped_no_external'    => $arrClass['skipped_no_external'],
@@ -2048,7 +2055,6 @@ function fxChronotrackApiSyncBuildPreview($intEveId) {
         'anomaly_no_sex'         => $arrClass['blocked_no_sex'],
         'anomaly_duplicate_bib'  => $arrClass['blocked_duplicate_bib'],
         'duplicate_bib_numbers'  => $arrClass['duplicate_bib_numbers'],
-        'anomalies'              => $arrClass['blocked'],
         'ct_total'               => null,
         'ct_total_loaded'        => false,
         'already_in_ct'          => null,
@@ -2290,11 +2296,10 @@ function fxChronotrackApiSyncPushPrepare($intEveId, $arrOptions = array()) {
         $tabPending = fxChronotrackApiSyncFilterChangedSincePush($arrClass['transferable'], $strLastPushAt);
     }
 
-    // Plus de scan CT à la préparation : POST upsert (crée ou maj) sans entry_id.
+    // Garder entry_id en meta/job pour retry dossard ; l’envoi lot utilise POST upsert (pas PUT unitaire).
     $tabBatch = array();
     $tabMeta = array();
     foreach ($tabPending as $arrItem) {
-        // Garder entry_id si déjà lié CT → push chunk fera PUT (maj dossard fiable).
         $arrPayload = $arrItem['payload'];
         $strCtEntryId = preg_replace('/[^0-9]/', '', (string)($arrItem['row']['ct_entry_id'] ?? ''));
         if ($strCtEntryId !== '') {
@@ -2443,34 +2448,17 @@ function fxChronotrackApiSyncPushEvent($intEveId, $arrOptions = array()) {
     $tabErrors = array();
     $tabBibRetryChunk = array();
 
-    // MSIN-4328 — entries liées (ct_entry_id) : PUT unitaire (+ clear bib si swap).
-    // Sans entry_id : POST lot (upsert). Ne plus stripper entry_id avant adaptive.
+    // MSIN-4328 — toujours POST en lot (upsert par external_id).
+    // Avant : PUT unitaire si ct_entry_id → ~100 appels/lot = 1–2 min figé à 0/N.
+    // entry_id reste sur le payload pour la 2e passe dossard ; retiré seulement à l’appel POST.
     $tabPostEntries = array();
     $tabPostMeta = array();
     foreach ($tabBatch as $intI => $arrPayload) {
         if (!is_array($arrPayload)) {
             continue;
         }
-        $strEntryId = trim((string)($arrPayload['entry_id'] ?? ''));
-        if ($strEntryId !== '') {
-            $arrOne = fxChronotrackApiSyncPushOneEntryWithBibConflictHandling(
-                $intCtEventId,
-                $arrPayload,
-                $tabMeta[$intI] ?? array('par_id' => 0, 'external_id' => ''),
-                $intEveId
-            );
-            $intOk += intval($arrOne['ok'] ?? 0);
-            $intErr += intval($arrOne['err'] ?? 0);
-            $intPutOk += intval($arrOne['ok'] ?? 0);
-            if (!empty($arrOne['bib_retry']) && is_array($arrOne['bib_retry'])) {
-                foreach ($arrOne['bib_retry'] as $arrR) {
-                    $tabBibRetryChunk[] = $arrR;
-                }
-            }
-        } else {
-            $tabPostEntries[] = $arrPayload;
-            $tabPostMeta[] = $tabMeta[$intI] ?? array('par_id' => 0, 'external_id' => '');
-        }
+        $tabPostEntries[] = $arrPayload;
+        $tabPostMeta[] = $tabMeta[$intI] ?? array('par_id' => 0, 'external_id' => '');
     }
 
     if (count($tabPostEntries) > 0) {
diff --git a/superadm/ajax_chronotrack_api.php b/superadm/ajax_chronotrack_api.php
index 3870b13..977517b 100644
--- a/superadm/ajax_chronotrack_api.php
+++ b/superadm/ajax_chronotrack_api.php
@@ -6,6 +6,10 @@ require_once dirname(__FILE__) . '/php/inc_functions.php';
 require_once dirname(__FILE__) . '/../php/chronotrack_api/inc_bootstrap.php';
 
 $intUsaId = fxSuperadmAjaxAuthOrJsonExit();
+// MSIN-4328 — libérer le verrou session : sinon un push long bloque Actualiser / preview (Erreur réseau).
+if (session_status() === PHP_SESSION_ACTIVE) {
+    session_write_close();
+}
 
 $strAction = trim((string)($_REQUEST['a'] ?? ''));
 $intEveId = intval($_REQUEST['eve_id'] ?? 0);
@@ -91,7 +95,7 @@ switch ($strAction) {
             $tabRetour = array('state' => 'error', 'message' => 'eve_id manquant');
             break;
         }
-        set_time_limit(60);
+        set_time_limit(120);
         $tabRetour = fxChronotrackApiSyncBuildPreview($intEveId);
         break;