Sending multiple messages on Whatsapp Cloud API with the same trigger

Hi everyone,

I’m working on a callin.io workflow that receives messages from WhatsApp (using the official WhatsApp Cloud API + callin.io WhatsApp Trigger).

I want to combine multiple short user messages into a single input before sending them to GPT or another processor.

My goal:

• When a user sends a message, I want to wait 8 seconds to see if any more messages are coming.
• If additional messages come within that window, I want to append them to the previous ones.
• Once there’s an 8-second pause, I consider the input complete and then send the combined message to the AI.

The problem:

• WhatsApp sends each message as a separate webhook call, so each message starts a new execution in callin.io.
• I’m trying to store the messages temporarily (using Simple Memory) and track the last_message_time.
• But since each execution is isolated, I can’t easily set up a delay inside the same flow that checks for future messages.
• I tried using Wait + IF nodes with timestamp comparison, but it doesn’t feel reliable because the workflow finishes before new messages arrive.

What I’m looking for:

• Has anyone successfully built a “delayed input merge” system in callin.io?
• Is there a way to delay response until user input is silent for X seconds, across multiple executions?
• Or should I use an external system (e.g. Redis, database + cron job) to collect and check messages before triggering GPT?

Any design patterns or ideas are welcome

Thanks in advance!