This issue was addressed with improved checks. This issue is fixed in iOS 18.0.1 and iPadOS 18.0.1. Audio messages in Messages may be able to capture a few seconds of audio before the microphone indicator is activated.
| Name | Vendor | Start Version | End Version | 
|---|---|---|---|
| Ipados | Apple | * | 18.0.1 (excluding) | 
| Iphone_os | Apple | * | 18.0.1 (excluding) |