Can I move my WhatsApp Business app number to the API without losing my chats?

Yes, but only the right way. Through a partner that supports Business app number onboarding you keep your chats. If you delete the app account first, your history is lost.

• Delete first: your messaging history is lost and you cannot use the number on the app again unless you deregister it from the Cloud API.
• Partner onboarding: you can use both the app and the API and keep your chat history.
• Ask any provider which route it uses before you start.
• Export what you need before any change.