return messages != null ? messages.size() : 0;
        }
    }

    /**
     * Clears all messages in this session and updates the last accessed timestamp.
     */
    public void clearMessages() {
        synchronized (messagesLock) {
            if (messages != null) {
                messages.clear();
            }
        }
        this.lastAccessedAt = LocalDateTime.now();
    }

        session.addAssistantMessage("Message 2");
        assertEquals(2, session.getMessageCount());

        final LocalDateTime beforeClear = session.getLastAccessedAt();
        session.clearMessages();

        assertEquals(0, session.getMessageCount());
        assertTrue(session.getLastAccessedAt().isAfter(beforeClear) || session.getLastAccessedAt().isEqual(beforeClear));
    }

    @Test