diff --git a/src/PhonebookManager.php b/src/PhonebookManager.php
index a84ecb3..05a32e8 100644
--- a/src/PhonebookManager.php
+++ b/src/PhonebookManager.php
@@ -48,14 +48,22 @@ class PhonebookManager
             CREATE INDEX IF NOT EXISTS idx_phonebook_group ON phonebook_contacts(group_name);
         ");
 
-        // 1. Récupère la cartographie des groupes d'extensions
-        $egRows = $db->query("SELECT id, name, members FROM extension_groups")->fetchAll();
-        $extToGroup = [];
+        // 1. Récupère la cartographie complète des groupes d'extensions (un poste peut appartenir à plusieurs groupes)
+        $egRows = $db->query("SELECT id, name, members FROM extension_groups ORDER BY name COLLATE NOCASE ASC")->fetchAll();
+        $extToGroups = [];
         foreach ($egRows as $eg) {
+            $grpName = trim((string)($eg['name'] ?? ''));
+            if ($grpName === '') {
+                continue;
+            }
             $members = json_decode((string)$eg['members'], true) ?: [];
             foreach ($members as $extNum) {
-                if (!isset($extToGroup[(string)$extNum])) {
-                    $extToGroup[(string)$extNum] = trim((string)$eg['name']);
+                $k = (string)$extNum;
+                if (!isset($extToGroups[$k])) {
+                    $extToGroups[$k] = [];
+                }
+                if (!in_array($grpName, $extToGroups[$k], true)) {
+                    $extToGroups[$k][] = $grpName;
                 }
             }
         }
@@ -80,7 +88,7 @@ class PhonebookManager
             $extNum = trim((string)$ext['extension']);
             $extName = trim((string)$ext['name']);
             $email = trim((string)($ext['voicemail_email'] ?? ''));
-            $group = $extToGroup[$extNum] ?? 'Général';
+            $group = !empty($extToGroups[$extNum]) ? implode(', ', $extToGroups[$extNum]) : 'Général';
             $activeExtIds[] = $extId;
 
             $findStmt->execute([':ext_id' => $extId, ':num' => $extNum]);
@@ -122,33 +130,48 @@ class PhonebookManager
     {
         self::syncExtensions($db);
 
-        $params = [];
-        $sql = "SELECT * FROM phonebook_contacts";
+        $stmt = $db->query("SELECT * FROM phonebook_contacts ORDER BY display_name COLLATE NOCASE ASC");
+        $contacts = $stmt ? $stmt->fetchAll(PDO::FETCH_ASSOC) : [];
 
-        if ($group !== null && trim($group) !== '' && strtolower(trim($group)) !== 'all' && strtolower(trim($group)) !== 'tous') {
-            $cleanGroup = trim($group);
-            $sql .= " WHERE LOWER(group_name) = LOWER(:grp) OR LOWER(group_name) LIKE LOWER(:grp_like) OR LOWER(group_name) IN ('tous', 'all')";
-            $params[':grp'] = $cleanGroup;
-            $params[':grp_like'] = "%{$cleanGroup}%";
-        }
+        $cleanGroup = ($group !== null) ? trim($group) : '';
+        $filterByGroup = ($cleanGroup !== '' && !in_array(mb_strtolower($cleanGroup), ['all', 'tous'], true));
+        $targetLower = mb_strtolower($cleanGroup);
 
-        $sql .= " ORDER BY display_name COLLATE NOCASE ASC";
-        $stmt = $db->prepare($sql);
-        $stmt->execute($params);
-        $contacts = $stmt->fetchAll(PDO::FETCH_ASSOC);
-
-        // Vérification de la présence réelle du fichier sur le disque
-        foreach ($contacts as &$c) {
+        $result = [];
+        foreach ($contacts as $c) {
             if (!empty($c['photo_url'])) {
                 $filename = basename((string)$c['photo_url']);
                 if (!file_exists(self::AVATARS_DIR . '/' . $filename)) {
                     $c['photo_url'] = '';
                 }
             }
-        }
-        unset($c);
 
-        return $contacts;
+            $rawGroups = preg_split('/\s*,\s*/', trim((string)($c['group_name'] ?? ''))) ?: [];
+            $groupsList = array_values(array_unique(array_filter($rawGroups, fn($g) => $g !== '')));
+            if (empty($groupsList)) {
+                $groupsList = ['Général'];
+            }
+            $c['groups'] = $groupsList;
+            $c['group_name'] = implode(', ', $groupsList);
+
+            if ($filterByGroup) {
+                $matched = false;
+                foreach ($groupsList as $g) {
+                    $gLower = mb_strtolower($g);
+                    if ($gLower === $targetLower || in_array($gLower, ['tous', 'all'], true)) {
+                        $matched = true;
+                        break;
+                    }
+                }
+                if (!$matched) {
+                    continue;
+                }
+            }
+
+            $result[] = $c;
+        }
+
+        return $result;
     }
 
     /**
@@ -163,9 +186,11 @@ class PhonebookManager
             if ($g !== '') $groups[$g] = true;
         }
         $pbRows = $db->query("SELECT DISTINCT group_name FROM phonebook_contacts WHERE group_name != ''")->fetchAll(PDO::FETCH_COLUMN);
-        foreach ($pbRows as $g) {
-            $g = trim((string)$g);
-            if ($g !== '') $groups[$g] = true;
+        foreach ($pbRows as $raw) {
+            foreach (preg_split('/\s*,\s*/', trim((string)$raw)) ?: [] as $g) {
+                $g = trim((string)$g);
+                if ($g !== '') $groups[$g] = true;
+            }
         }
 
         // Ajoute Issy-Les-Moulineaux si pas encore présent
diff --git a/ucp/assets/ucp.js b/ucp/assets/ucp.js
index a8b8ba8..b77ed35 100644
--- a/ucp/assets/ucp.js
+++ b/ucp/assets/ucp.js
@@ -756,14 +756,26 @@ async function loadPhonebook() {
     }
 }
 
+function getContactGroups(contact) {
+    if (Array.isArray(contact?.groups) && contact.groups.length > 0) {
+        return contact.groups.map(g => String(g || '').trim()).filter(Boolean);
+    }
+    const split = String(contact?.group_name || '')
+        .split(',')
+        .map(g => g.trim())
+        .filter(Boolean);
+    return split.length > 0 ? Array.from(new Set(split)) : ['Général'];
+}
+
 function renderPhonebookGroupTabs(allContacts) {
     const tabsEl = document.getElementById('ucp-pb-group-tabs');
     if (!tabsEl) return;
 
     const counts = {};
     for (const c of allContacts) {
-        const grp = String(c.group_name || '').trim() || 'Général';
-        counts[grp] = (counts[grp] || 0) + 1;
+        for (const grp of getContactGroups(c)) {
+            counts[grp] = (counts[grp] || 0) + 1;
+        }
     }
 
     const groups = Object.keys(counts).sort((a, b) => {
@@ -821,8 +833,7 @@ function renderPhonebookGrid() {
     const activeGroup = ucpState.selectedPbGroup || '__all__';
     const q = (document.getElementById('ucp-pb-search')?.value || '').trim().toLowerCase();
     const list = allContacts.filter(c => {
-        const grp = String(c.group_name || '').trim() || 'Général';
-        if (activeGroup !== '__all__' && grp !== activeGroup) return false;
+        if (activeGroup !== '__all__' && !getContactGroups(c).includes(activeGroup)) return false;
         if (!q) return true;
         return [c.display_name, c.internal_number, c.mobile_number, c.other_number, c.email, c.group_name]
             .some(v => String(v || '').toLowerCase().includes(q));
diff --git a/version.json b/version.json
index a5f0fa5..cd15a5e 100644
--- a/version.json
+++ b/version.json
@@ -1,9 +1,10 @@
 {
-  "version": "2.6.3",
+  "version": "2.6.4",
   "codename": "Pulsar UCP",
   "release_date": "2026-11-12",
   "min_php_version": "8.2",
   "changelog": [
+    "Correctif v2.6.4 : prise en charge multi-groupes dans l'annuaire UCP & Admin (un poste appartenant à plusieurs groupes apparaît bien dans chacun des onglets correspondants)",
     "UI v2.6.3 : onglets dynamiques par groupe (Tous, Général, Paris, New-York...) avec compteurs dans l'Annuaire UCP",
     "Correctif v2.6.2 : sélection stricte de <host> GroundWire (NAT si renseigné, sinon VIP HA si cluster actif, sinon IP locale + port d'écoute local)",
     "UI v2.6.1 : suppression de l'icône smartphone sur les éléments GroundWire et refonte des boutons d'action du tableau Postes (Redémarrer / Modifier / Supprimer)",