diff --git a/CHANGELOG.md b/CHANGELOG.md
index e1befc3b..66c8ec2c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,9 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+### Fixed
+- Fixed group reassignment to remove previously assigned groups only when using the Escalade reassignment action
+
 ## [2.10.6] - 2026-07-31
 
 ### Fixed
diff --git a/front/ticket.form.php b/front/ticket.form.php
index cfd9ad4c..43826575 100644
--- a/front/ticket.form.php
+++ b/front/ticket.form.php
@@ -44,7 +44,14 @@
         throw new AccessDeniedHttpException();
     }
 
-    PluginEscaladeTicket::timelineClimbAction($group_id, $tickets_id, $_POST);
+    // Mark this operation as a real escalation from the Escalade form.
+    $_SESSION['plugin_escalade']['is_escalation'] = true;
+
+    try {
+        PluginEscaladeTicket::timelineClimbAction($group_id, $tickets_id, $_POST);
+    } finally {
+        unset($_SESSION['plugin_escalade']['is_escalation']);
+    }
 
     $track = new Ticket();
 
diff --git a/inc/history.class.php b/inc/history.class.php
index f2e7784d..d76a941f 100644
--- a/inc/history.class.php
+++ b/inc/history.class.php
@@ -160,12 +160,38 @@ public static function getHistory($tickets_id, $full_history = false)
         $group = new Group();
 
         $history = new self();
-        $found = $history->find(['tickets_id' => $tickets_id], "date_mod DESC");
+        $found = $history->find(
+            ['tickets_id' => $tickets_id],
+            ['date_mod DESC', 'id DESC'],
+        );
         $nb_histories = count($found);
 
         //remove first line (current assign)
         $first_group = array_shift($found);
 
+        // Do not display a group as a previous assignment while it is still
+        // assigned to the ticket. Its history entry stays in the database and
+        // becomes visible after a real reassignment removes the group.
+        $group_ticket = new Group_Ticket();
+        $currently_assigned = $group_ticket->find([
+            'tickets_id' => $tickets_id,
+            'type'       => CommonITILActor::ASSIGN,
+        ]);
+
+        $currently_assigned_ids = array_map(
+            static fn(array $actor): int => (int) $actor['groups_id'],
+            $currently_assigned,
+        );
+
+        $found = array_filter(
+            $found,
+            static fn(array $history_entry): bool => !in_array(
+                (int) $history_entry['groups_id'],
+                $currently_assigned_ids,
+                true,
+            ),
+        );
+
         if ($full_history) {
             //show 1st group
             echo "<div class='escalade_active'>";
diff --git a/inc/ticket.class.php b/inc/ticket.class.php
index b39f5bc6..93729fc4 100644
--- a/inc/ticket.class.php
+++ b/inc/ticket.class.php
@@ -502,7 +502,16 @@ public static function processAfterAddGroup(Group_Ticket $item)
         // getFromDB() is required first so isNewItem() returns false and deleted-actor
         // detection runs. _plugin_escalade_rules_only skips escalade logic in pre_item_update.
         // Safety net in case updateActors() above did not already remove old groups.
-        if ($_SESSION['glpi_plugins']['escalade']['config']['remove_group'] == true) {
+        if (
+            $_SESSION['glpi_plugins']['escalade']['config']['remove_group'] == true
+            && (
+                !empty($_SESSION['plugin_escalade']['is_escalation'])
+                || !empty($_SESSION['plugin_escalade']['climb_group'])
+                || !empty($_SESSION['plugin_escalade']['auto_group_assignment'])
+                || !empty($_SESSION['plugin_escalade']['category_group_reassignment'])
+            )
+        ) {
+
             $all_actors = self::getTicketFieldsWithActors($tickets_id, $groups_id);
 
             // Keep only the new group in the assign list (drop old ones).
@@ -667,12 +676,22 @@ public static function climb_group($tickets_id, $groups_id, $no_redirect = false
             // and wipes them from the ticket regardless of the
             // "Remove requester(s) on escalation" plugin config.
             $ticket = new Ticket();
-            $ticket->update([
-                'id'        => $tickets_id,
-                '_actors'   => self::getTicketFieldsWithActors($tickets_id, $groups_id),
-                'actortype' => CommonITILActor::ASSIGN,
-                'groups_id' => $groups_id,
-            ]);
+
+            // Mark this assignment as an actual Escalade reassignment.
+            // processAfterAddGroup() also runs for normal GLPI group assignments,
+            // so old groups must only be removed for this specific action.
+            $_SESSION['plugin_escalade']['climb_group'] = true;
+
+            try {
+                $ticket->update([
+                    'id'        => $tickets_id,
+                    '_actors'   => self::getTicketFieldsWithActors($tickets_id, $groups_id),
+                    'actortype' => CommonITILActor::ASSIGN,
+                    'groups_id' => $groups_id,
+                ]);
+            } finally {
+                unset($_SESSION['plugin_escalade']['climb_group']);
+            }
         }
 
         if (!$no_redirect) {
@@ -851,12 +870,19 @@ public static function item_add_user(Ticket_User $item, $type = CommonITILActor:
             //prevent user removal
             $_SESSION['plugin_escalade']['keep_users'][$item->fields['users_id']]
                 = $item->fields['users_id'];
-            //add new group to ticket
-            $group_ticket->add([
-                'tickets_id' => $tickets_id,
-                'groups_id'  => $groups_id,
-                'type'       => CommonITILActor::ASSIGN,
-            ]);
+
+            // Mark this group assignment as an automatic Escalade assignment.
+            $_SESSION['plugin_escalade']['auto_group_assignment'] = true;
+
+            try {
+                $group_ticket->add([
+                    'tickets_id' => $tickets_id,
+                    'groups_id'  => $groups_id,
+                    'type'       => CommonITILActor::ASSIGN,
+                ]);
+            } finally {
+                unset($_SESSION['plugin_escalade']['auto_group_assignment']);
+            }
         } elseif ($_SESSION['glpi_plugins']['escalade']['config']['remove_tech']) {
             self::removeAssignGroups($tickets_id);
         }
@@ -952,7 +978,14 @@ public static function qualification(CommonDBTM $item)
             $group_found = $group_ticket->find($group_condition);
             if (empty($group_found)) {
                 //add group to ticket
-                $group_ticket->add($group_condition);
+                $_SESSION['plugin_escalade']['category_group_reassignment'] = true;
+
+                try {
+                    $group_ticket->add($group_condition);
+                } finally {
+                    unset($_SESSION['plugin_escalade']['category_group_reassignment']);
+                }
+
                 //remove old group if needed
                 if ($_SESSION['glpi_plugins']['escalade']['config']['remove_group'] && isset($item->input['_groups_id_assign'])) {
                     foreach ($item->input['_groups_id_assign'] as $idActor => $actor) {
diff --git a/tests/EscaladeTestCase.php b/tests/EscaladeTestCase.php
index d831ddac..6421a125 100644
--- a/tests/EscaladeTestCase.php
+++ b/tests/EscaladeTestCase.php
@@ -176,7 +176,19 @@ public function escalateWithTimelineButton(Ticket $ticket, Group $group, array $
             ],
         );
         $_POST['comment'] = $options['comment'] ?? 'Default comment';
-        PluginEscaladeTicket::timelineClimbAction($group->getID(), $ticket->getID(), $options);
+
+        $_SESSION['plugin_escalade']['is_escalation'] = true;
+
+        try {
+            PluginEscaladeTicket::timelineClimbAction(
+                $group->getID(),
+                $ticket->getID(),
+                $options,
+            );
+        } finally {
+            unset($_SESSION['plugin_escalade']['is_escalation']);
+        }
+
         $ticketgroup = new Group_Ticket();
         $is_escalate = $ticketgroup->getFromDBByCrit([
             'tickets_id' => $ticket->getID(),
diff --git a/tests/Units/GroupEscalationTest.php b/tests/Units/GroupEscalationTest.php
index 8db2e4fc..56eff7a5 100644
--- a/tests/Units/GroupEscalationTest.php
+++ b/tests/Units/GroupEscalationTest.php
@@ -37,6 +37,7 @@
 use Notification;
 use NotificationTarget;
 use PluginEscaladeHistory;
+use PluginEscaladeTicket;
 use PluginEscaladeNotification;
 use QueuedNotification;
 use Ticket;
@@ -45,6 +46,153 @@
 
 final class GroupEscalationTest extends EscaladeTestCase
 {
+    /**
+     * Standard GLPI group assignment must not remove previously assigned groups.
+     */
+    public function testStandardGroupAssignmentKeepsExistingGroups(): void
+    {
+        $this->initConfig([
+            'remove_group' => 1,
+            'show_history' => 1,
+        ]);
+
+        $group1 = $this->createGroup('standard_group_1_' . uniqid());
+        $group2 = $this->createGroup('standard_group_2_' . uniqid());
+
+        $ticket = $this->createItem(Ticket::class, [
+            'name' => 'Standard group assignment regression test',
+            'content' => '',
+            '_actors' => [
+                'assign' => [
+                    [
+                        'items_id' => $group1->getID(),
+                        'itemtype' => 'Group',
+                    ],
+                ],
+            ],
+        ]);
+
+        // Simulate adding another group from the standard GLPI actors field.
+        $this->createItem(Group_Ticket::class, [
+            'tickets_id' => $ticket->getID(),
+            'groups_id' => $group2->getID(),
+            'type' => CommonITILActor::ASSIGN,
+        ]);
+
+        $group_ticket = new Group_Ticket();
+        $assigned_groups = $group_ticket->find([
+            'tickets_id' => $ticket->getID(),
+            'type' => CommonITILActor::ASSIGN,
+        ]);
+
+        $this->assertCount(2, $assigned_groups);
+
+        $this->assertCount(1, $group_ticket->find([
+            'tickets_id' => $ticket->getID(),
+            'groups_id' => $group1->getID(),
+            'type' => CommonITILActor::ASSIGN,
+        ]));
+
+        $this->assertCount(1, $group_ticket->find([
+            'tickets_id' => $ticket->getID(),
+            'groups_id' => $group2->getID(),
+            'type' => CommonITILActor::ASSIGN,
+        ]));
+    }
+
+    /**
+     * A real Escalade reassignment must remove old groups while preserving
+     * every previously assigned group in the visual assignment history.
+     */
+    public function testEscaladeReassignmentPreservesAllGroupsInHistory(): void
+    {
+        $this->initConfig([
+            'remove_group' => 1,
+            'show_history' => 1,
+        ]);
+
+        $group1 = $this->createGroup('history_group_1_' . uniqid());
+        $group2 = $this->createGroup('history_group_2_' . uniqid());
+        $group3 = $this->createGroup('history_group_3_' . uniqid());
+        $group4 = $this->createGroup('history_destination_' . uniqid());
+
+        $ticket = $this->createItem(Ticket::class, [
+            'name' => 'Multiple group history regression test',
+            'content' => '',
+            '_actors' => [
+                'assign' => [
+                    [
+                        'items_id' => $group1->getID(),
+                        'itemtype' => 'Group',
+                    ],
+                ],
+            ],
+        ]);
+
+        // Add groups through the normal GLPI assignment mechanism.
+        foreach ([$group2, $group3] as $group) {
+            $this->createItem(Group_Ticket::class, [
+                'tickets_id' => $ticket->getID(),
+                'groups_id' => $group->getID(),
+                'type' => CommonITILActor::ASSIGN,
+            ]);
+        }
+
+        $group_ticket = new Group_Ticket();
+
+        $this->assertCount(3, $group_ticket->find([
+            'tickets_id' => $ticket->getID(),
+            'type' => CommonITILActor::ASSIGN,
+        ]));
+
+        // Simulate the real Escalade button.
+        $_SESSION['plugin_escalade']['is_escalation'] = true;
+        $_POST['comment'] = 'Regression test escalation';
+
+        try {
+            PluginEscaladeTicket::timelineClimbAction(
+                $group4->getID(),
+                $ticket->getID(),
+                [
+                    'ticket_details' => [
+                        'id' => $ticket->getID(),
+                    ],
+                ],
+            );
+        } finally {
+            unset($_SESSION['plugin_escalade']['is_escalation']);
+            unset($_POST['comment']);
+        }
+
+        // Only the destination group must remain assigned.
+        $assigned_groups = $group_ticket->find([
+            'tickets_id' => $ticket->getID(),
+            'type' => CommonITILActor::ASSIGN,
+        ]);
+
+        $this->assertCount(1, $assigned_groups);
+        $assigned_group = reset($assigned_groups);
+        $this->assertEquals($group4->getID(), $assigned_group['groups_id']);
+
+        // All groups involved in the reassignment must remain visible
+        // in Escalade history.
+        $history = new PluginEscaladeHistory();
+
+        foreach ([$group1, $group2, $group3, $group4] as $group) {
+            $this->assertGreaterThanOrEqual(
+                1,
+                count($history->find([
+                    'tickets_id' => $ticket->getID(),
+                    'groups_id' => $group->getID(),
+                ])),
+                sprintf(
+                    'Group %d is missing from Escalade history',
+                    $group->getID(),
+                ),
+            );
+        }
+    }
+
     public function testTechGroupAttributionUpdateTicket()
     {
         $this->initConfig([
diff --git a/tests/Units/TicketTest.php b/tests/Units/TicketTest.php
index d3a305a6..8ca189a9 100644
--- a/tests/Units/TicketTest.php
+++ b/tests/Units/TicketTest.php
@@ -355,14 +355,14 @@ public function testTicketUpdateDoesNotChangeITILCategoryAssignedGroup()
             ],
         ]);
 
-        $this->assertEquals(0, count($group_ticket->find(['tickets_id' => $ticket_id, 'groups_id' => $group1_id, 'type' => CommonITILActor::ASSIGN])));
+        $this->assertEquals(1, count($group_ticket->find(['tickets_id' => $ticket_id, 'groups_id' => $group1_id, 'type' => CommonITILActor::ASSIGN])));
         $this->assertEquals(1, count($group_ticket->find(['tickets_id' => $ticket_id, 'groups_id' => $group2_id, 'type' => CommonITILActor::ASSIGN])));
 
         $this->updateItem('Ticket', $ticket_id, [
             'status' => CommonITILObject::WAITING,
         ]);
 
-        $this->assertEquals(0, count($group_ticket->find(['tickets_id' => $ticket_id, 'groups_id' => $group1_id, 'type' => CommonITILActor::ASSIGN])));
+        $this->assertEquals(1, count($group_ticket->find(['tickets_id' => $ticket_id, 'groups_id' => $group1_id, 'type' => CommonITILActor::ASSIGN])));
         $this->assertEquals(1, count($group_ticket->find(['tickets_id' => $ticket_id, 'groups_id' => $group2_id, 'type' => CommonITILActor::ASSIGN])));
     }