Hi, you must play with widget settings as well.
'containerWidth': '100%25',
'layoutWidth': '100%25',
I change it for each device using CSS and javascript by recognizing the screen size.
Use it inside your bot webchat->configurable:
window.botpressWebChat.init({
"botId": "",
"hostUrl": "https://cdn.botpress.cloud/webchat/v1",
"messagingUrl": "https://messaging.botpress.cloud",
"clientId": "",
"webhookId": "",
"lazySocket": true,
"themeName": "prism",
"botName": "",
"avatarUrl": "",
"stylesheet": "",
"frontendVersion": "v1",
"useSessionStorage": true,
"enableConversationDeletion": true,
"themeColor": "#2563eb",
"containerWidth": "100%25",
"layoutWidth": "100%25",
});