Unable to send message to a new contact after July 2nd update

Starting around 2026-07-02, we've noticed a change in behavior when sending messages with WhatsMeow.

The issue only affects contacts that meet all of the following conditions:

• The contact has never had a conversation with the account on phone.
• The contact is not saved in the phone's address book.
• There is no existing chat with that contact.

Steps to reproduce

1. Use a phone number that has never been contacted before.
2. Ensure there is no existing chat with that number.
3. Send a message using WhatsMeow.
4. The message is not delivered.
5. Save the contact in the phone's address book.
6. Try sending again with WhatsMeow.
7. The message is still not delivered.
8. Open the official WhatsApp app and send one message to that contact.
9. Try sending again using WhatsMeow.
10. The message is now delivered successfully.

Important observation

Simply saving the contact does not solve the problem.

Simply opening the conversation in the official WhatsApp client does not solve the problem.

The issue is only resolved after sending the first message through the official WhatsApp client.

Once that first message has been sent, WhatsMeow can send subsequent messages to the same contact normally.

Additional information

I've seen multiple users reporting the same behavior, so it does not appear to be an isolated issue.

The timing also seems to coincide with the rollout of WhatsApp usernames (@username) beginning around July 2nd. I don't know if the two are related, but the dates match closely enough that it may indicate a protocol change affecting how a first conversation with a new contact is initialized.

Has anyone else investigated this or identified what changed in the protocol?