diff --git a/docs/tickets/open/TICKET-031.md b/docs/tickets/closed/TICKET-031.md
similarity index 100%
rename from docs/tickets/open/TICKET-031.md
rename to docs/tickets/closed/TICKET-031.md
diff --git a/docs/tickets/closed/TICKET-31.1.md b/docs/tickets/closed/TICKET-31.1.md
new file mode 100644
index 0000000..dd49b30
--- /dev/null
+++ b/docs/tickets/closed/TICKET-31.1.md
@@ -0,0 +1,280 @@
+# Ticket #031.1 — Ajouter une fermeture propre de l’application
+
+## Contexte
+
+L’application permet désormais :
+
+- de créer une enquête ;
+- d’ouvrir une enquête existante ;
+- de remplacer proprement la session active.
+
+La fermeture se fait encore avec :
+
+```text
+Ctrl+C
+```
+
+Cette méthode interrompt brutalement le processus et ne constitue pas un parcours utilisateur normal.
+
+## Objectif
+
+Ajouter un bouton :
+
+```text
+Quitter
+```
+
+permettant de fermer proprement l’application GTK.
+
+La fermeture doit déclencher le cycle normal de nettoyage :
+
+```text
+GtkApplication
+    ↓
+fin de la boucle principale
+    ↓
+application_free()
+    ↓
+InvestigationTreeModel libéré
+    ↓
+InvestigationSession fermée
+    ↓
+Database fermée
+    ↓
+MainWindow libérée
+```
+
+## Travail à réaliser
+
+### 1. Ajouter le bouton dans `MainWindow`
+
+Modifier :
+
+```text
+include/views/main_window.h
+src/views/main_window.c
+```
+
+La barre d’actions doit devenir :
+
+```text
+[ Nouvelle enquête ] [ Ouvrir une enquête ] [ Quitter ]
+```
+
+Ajouter dans la structure privée :
+
+```c
+GtkWidget *quit_button;
+```
+
+### 2. Ajouter le type de callback
+
+Dans `include/views/main_window.h`, ajouter :
+
+```c
+typedef void (*MainWindowQuitCallback)(
+    gpointer user_data
+);
+```
+
+Puis déclarer :
+
+```c
+void main_window_set_quit_callback(
+    MainWindow *main_window,
+    MainWindowQuitCallback callback,
+    gpointer user_data
+);
+```
+
+### 3. Conserver le callback dans `MainWindow`
+
+Ajouter dans la structure privée :
+
+```c
+MainWindowQuitCallback
+    quit_callback;
+
+gpointer
+    quit_user_data;
+```
+
+### 4. Ajouter le callback privé du bouton
+
+Dans `src/views/main_window.c`, ajouter :
+
+```c
+static void main_window_on_quit_clicked(
+    GtkButton *button,
+    gpointer user_data
+);
+```
+
+Cette fonction doit :
+
+- accepter `button == NULL` ;
+- accepter `main_window == NULL` ;
+- ne rien faire si aucun callback n’est défini ;
+- appeler le callback configuré sinon.
+
+### 5. Créer le bouton
+
+Dans `main_window_new()` :
+
+```c
+main_window->quit_button =
+    gtk_button_new_with_label(
+        "Quitter"
+    );
+```
+
+Ajouter le bouton à `action_bar`.
+
+Relier son signal `clicked` à :
+
+```c
+main_window_on_quit_clicked
+```
+
+### 6. Ajouter le setter public
+
+Implémenter :
+
+```c
+void main_window_set_quit_callback(
+    MainWindow *main_window,
+    MainWindowQuitCallback callback,
+    gpointer user_data
+)
+{
+    if (main_window == NULL)
+    {
+        return;
+    }
+
+    main_window->quit_callback = callback;
+    main_window->quit_user_data = user_data;
+}
+```
+
+### 7. Ajouter le contrôleur dans `Application`
+
+Dans `src/core/application.c`, ajouter :
+
+```c
+static void application_on_quit_requested(
+    gpointer user_data
+);
+```
+
+Cette fonction doit utiliser :
+
+```c
+g_application_quit(
+    G_APPLICATION(
+        application->gtk_application
+    )
+);
+```
+
+Aucun appel direct à `exit()` ne doit être ajouté.
+
+### 8. Relier le callback dans `application_on_activate()`
+
+Ajouter :
+
+```c
+main_window_set_quit_callback(
+    application->main_window,
+    application_on_quit_requested,
+    application
+);
+```
+
+## Tests manuels
+
+### Fermeture sans enquête
+
+1. lancer l’application ;
+2. cliquer sur `Quitter` ;
+3. vérifier que le processus se termine normalement.
+
+### Fermeture avec une enquête ouverte
+
+1. ouvrir ou créer une enquête ;
+2. cliquer sur `Quitter` ;
+3. vérifier que la fenêtre se ferme ;
+4. vérifier qu’aucun crash n’apparaît ;
+5. relancer l’application ;
+6. rouvrir la même enquête.
+
+### Fermeture après remplacement de session
+
+1. ouvrir une enquête A ;
+2. ouvrir une enquête B ;
+3. cliquer sur `Quitter` ;
+4. vérifier l’absence de crash ou de double libération.
+
+## Critères d’acceptation
+
+- [ ] Le bouton `Quitter` est visible.
+- [ ] Le bouton ferme l’application.
+- [ ] Aucun `exit()` direct n’est utilisé.
+- [ ] `g_application_quit()` est utilisé.
+- [ ] `MainWindow` ne connaît pas `GtkApplication`.
+- [ ] Le nettoyage reste géré par `Application`.
+- [ ] La fermeture fonctionne sans enquête ouverte.
+- [ ] La fermeture fonctionne avec une enquête ouverte.
+- [ ] La fermeture fonctionne après un changement d’enquête.
+- [ ] `make` réussit.
+- [ ] `make test` réussit.
+- [ ] `git diff --check` ne retourne aucune erreur.
+
+## Audit attendu
+
+```bash
+rg -n \
+    'quit_button|quit_callback|g_application_quit' \
+    include/views/main_window.h \
+    src/views/main_window.c \
+    src/core/application.c
+```
+
+La commande suivante ne doit rien afficher :
+
+```bash
+rg -n \
+    '\bexit\s*\(' \
+    src/core/application.c \
+    src/views/main_window.c
+```
+
+## Fichiers concernés
+
+```text
+include/views/main_window.h
+src/views/main_window.c
+src/core/application.c
+```
+
+## Commit attendu
+
+```bash
+make clean
+make
+make test
+git diff --check
+git status --short
+```
+
+```bash
+git add \
+    include/views/main_window.h \
+    src/views/main_window.c \
+    src/core/application.c
+```
+
+```bash
+git commit -m "feat(ui): add clean application quit action"
+git push
+```
diff --git a/include/views/main_window.h b/include/views/main_window.h
index b753945..112f07c 100644
--- a/include/views/main_window.h
+++ b/include/views/main_window.h
@@ -147,6 +147,15 @@ typedef void (*MainWindowOpenInvestigationCallback)(
     gpointer user_data
 );
 
+/**
+ * @brief Callback appelé lorsque l'utilisateur demande à quitter.
+ *
+ * @param user_data Données utilisateur associées au callback.
+ */
+typedef void (*MainWindowQuitCallback)(
+    gpointer user_data
+);
+
 /**
  * @brief Définit le callback du bouton « Ouvrir une enquête ».
  *
@@ -162,6 +171,21 @@ void main_window_set_open_investigation_callback(
     gpointer user_data
 );
 
+/**
+ * @brief Définit le callback du bouton « Quitter ».
+ *
+ * MainWindow transmet uniquement la demande au contrôleur.
+ *
+ * @param main_window Fenêtre principale.
+ * @param callback Fonction appelée lors du clic.
+ * @param user_data Données transmises au callback.
+ */
+void main_window_set_quit_callback(
+    MainWindow *main_window,
+    MainWindowQuitCallback callback,
+    gpointer user_data
+);
+
 /**
  * @brief Libère les ressources de la fenêtre.
  *
diff --git a/labfy-investigation b/labfy-investigation
index a1c6bd7..0825d5b 100755
Binary files a/labfy-investigation and b/labfy-investigation differ
diff --git a/src/core/application.c b/src/core/application.c
index a5a95bd..f08dda5 100644
--- a/src/core/application.c
+++ b/src/core/application.c
@@ -498,6 +498,30 @@ static void application_on_tree_node_selected(
     }
 }
 
+/**
+ * @brief Ferme proprement l'application.
+ *
+ * @param user_data Pointeur vers Application.
+ */
+static void application_on_quit_requested(
+    gpointer user_data
+)
+{
+    Application *application = user_data;
+
+    if (application == NULL ||
+        application->gtk_application == NULL)
+    {
+        return;
+    }
+
+    g_application_quit(
+        G_APPLICATION(
+            application->gtk_application
+        )
+    );
+}
+
 /**
  * @brief Crée la fenêtre principale lors de l'activation.
  *
@@ -559,6 +583,12 @@ static void application_on_activate(
         application
     );
 
+    main_window_set_quit_callback(
+        application->main_window,
+        application_on_quit_requested,
+        application
+    );
+
     main_window_present(
         application->main_window
     );
diff --git a/src/views/main_window.c b/src/views/main_window.c
index 5bd8210..4e395ab 100644
--- a/src/views/main_window.c
+++ b/src/views/main_window.c
@@ -54,6 +54,7 @@ struct MainWindow
     GtkWidget *open_investigation_button;
     GtkWidget *main_paned;
     GtkWidget *status_label;
+    GtkWidget *quit_button;
 
     Sidebar *sidebar;
     Workspace *workspace;
@@ -69,6 +70,12 @@ struct MainWindow
 
     gpointer
         open_investigation_user_data;
+
+    MainWindowQuitCallback
+        quit_callback;
+
+    gpointer
+        quit_user_data;
 };
 
 /**
@@ -123,6 +130,32 @@ static void main_window_on_open_investigation_clicked(
     );
 }
 
+/**
+ * @brief Transmet la demande de fermeture au contrôleur.
+ *
+ * @param button Bouton ayant reçu le clic.
+ * @param user_data Pointeur vers MainWindow.
+ */
+static void main_window_on_quit_clicked(
+    GtkButton *button,
+    gpointer user_data
+)
+{
+    MainWindow *main_window = user_data;
+
+    (void) button;
+
+    if (main_window == NULL ||
+        main_window->quit_callback == NULL)
+    {
+        return;
+    }
+
+    main_window->quit_callback(
+        main_window->quit_user_data
+    );
+}
+
 MainWindow *main_window_new(GtkApplication *application)
 {
     MainWindow *main_window = NULL;
@@ -206,6 +239,11 @@ MainWindow *main_window_new(GtkApplication *application)
             "Ouvrir une enquête"
         );
 
+    main_window->quit_button =
+        gtk_button_new_with_label(
+            "Quitter"
+        );
+    
     gtk_box_append(
         GTK_BOX(main_window->action_bar),
         main_window->new_investigation_button
@@ -216,6 +254,11 @@ MainWindow *main_window_new(GtkApplication *application)
         main_window->open_investigation_button
     );
 
+    gtk_box_append(
+        GTK_BOX(main_window->action_bar),
+        main_window->quit_button
+    );
+
     g_signal_connect(
         main_window->new_investigation_button,
         "clicked",
@@ -234,6 +277,15 @@ MainWindow *main_window_new(GtkApplication *application)
         main_window
     );
 
+    g_signal_connect(
+        main_window->quit_button,
+        "clicked",
+        G_CALLBACK(
+            main_window_on_quit_clicked
+        ),
+        main_window
+    );
+
     /*
      * GtkPaned sépare horizontalement le panneau latéral
      * et la zone de travail.
@@ -600,6 +652,21 @@ void main_window_set_open_investigation_callback(
     main_window->open_investigation_user_data = user_data;
 }
 
+void main_window_set_quit_callback(
+    MainWindow *main_window,
+    MainWindowQuitCallback callback,
+    gpointer user_data
+)
+{
+    if (main_window == NULL)
+    {
+        return;
+    }
+
+    main_window->quit_callback = callback;
+    main_window->quit_user_data = user_data;
+}
+
 void main_window_set_selected_node(
     MainWindow *main_window,
     const InvestigationNode *node
@@ -616,7 +683,9 @@ void main_window_set_selected_node(
     );
 }
 
-void main_window_free(MainWindow *main_window)
+void main_window_free(
+    MainWindow *main_window
+)
 {
     if (main_window == NULL)
     {
@@ -624,13 +693,31 @@ void main_window_free(MainWindow *main_window)
     }
 
     /*
-     * La structure Sidebar a été allouée par sidebar_new().
-     * MainWindow en est donc propriétaire et doit la libérer.
+     * La fenêtre et tous ses widgets doivent être détruits pendant que
+     * les structures MainWindow, Sidebar et Workspace existent encore.
      *
-     * Les widgets GTK, eux, restent gérés par GTK.
+     * Certains widgets possèdent des callbacks dont user_data pointe vers
+     * ces structures.
      */
-    workspace_free(main_window->workspace);
-    sidebar_free(main_window->sidebar);
+    if (main_window->window != NULL)
+    {
+        gtk_window_destroy(
+            main_window->window
+        );
+
+        main_window->window = NULL;
+    }
+
+    workspace_free(
+        main_window->workspace
+    );
+
+    sidebar_free(
+        main_window->sidebar
+    );
+
+    main_window->workspace = NULL;
+    main_window->sidebar = NULL;
 
     g_free(main_window);
 }
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