Multiple agents and systems answering one Coexistence number

How do several people answer the same number?

Through linked devices. WhatsApp lets one account be used on up to four additional devices besides the primary phone, and its announcement of the feature named the use case directly: employees of a small business responding to customers from their own phones under the same WhatsApp Business account.

On a Coexistence number that still holds. The primary phone stays the owner of the account, and other staff work from linked phones, tablets, browsers or desktop apps. Which companion clients are supported, and what onboarding does to them, is covered on the page about linked devices.

Where does software fit in?

On the API side of the same number. A CRM, an automation tool or an AI agent sends through the Cloud API and receives customer messages through webhooks, while the people keep using the app.

The number is the same line on both sides, so a customer sees one conversation regardless of who wrote each message. Messages the API sends appear in the app thread, so staff see what the system already said. The only shared constraint is volume: Meta fixes a number in use with both the app and Cloud API at 20 messages per second.

How does software know a person already answered?

From the echo. Meta's smb_message_echoes webhook fires when a business onboarded by a partner sends a message using the WhatsApp Business app or a companion device, and also when a message is edited or deleted from the app.

That covers every human on the number, whether they typed on the primary phone or on a linked laptop. A system that reads echoes can mark a conversation as handled by a person and stop its own reply, which is the difference between automation that assists a team and automation that talks over it.

• Sent from the app or a companion device: an echo arrives.
• Edited in the app: an echo arrives.
• Deleted in the app: an echo arrives.

What does each side have to keep in mind?

Staff keep the primary phone in use. Meta disconnects a Coexistence number after roughly 14 days of inactivity on the primary device, and a companion device after about 30 days of its own inactivity, so a team that works only from laptops can lose both.

Software keeps to the platform's rules: free text within the 24 hour customer service window, templates outside it. And neither side gets group chats through the API, which Meta excludes on numbers shared with the app.

Common mistakes

• Ignoring smb_message_echoes. Without them a bot cannot tell a human already replied from a linked laptop.
• Running the whole team from linked laptops while the primary phone sits unused for weeks.
• Linking WhatsApp for Windows after onboarding. Meta lists it as unsupported on Coexistence numbers.

Frequently asked questions

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