How to Answer a Webhook Instantly While AI Runs in the Background in n8n

Many senders give up if a webhook takes more than a few seconds to respond, but a long AI generation can run much longer. The pattern that solves this is respond first, work later: reply with a quick acknowledgement, then continue the heavy AI step on a separate branch and deliver the result somewhere else.

What you need

• An n8n instance, version 1.x
• A chat model credential for the slow generation step
• A place to deliver the finished result (Slack, email, or a callback URL)

Step 1: Respond before the AI step

Set the Webhook node Respond option to Using Respond to Webhook Node. Wire a Respond to Webhook node as the very next step so n8n returns a 200 right away, before any model call.

{
  "status": "accepted",
  "message": "Your request is processing. We'll post the result to Slack."
}

Step 2: Continue to the AI node

From the Webhook node, also connect a second branch into your AI Agent or HTTP model node. Because the response already went out, this branch can take as long as it needs.

Step 3: Deliver the finished result

After the AI node, add a delivery step. A Slack message, an email, or an HTTP request back to the caller all work. Include any id from the original payload so the result can be matched up.

Result: the caller gets a confirmation in well under a second, and the finished article shows up in your Slack channel a minute later with no timeout error.