𝐓𝐡𝐞 𝐬𝐜𝐚𝐫𝐢𝐞𝐬𝐭 𝐧𝟖𝐧 𝐛𝐮𝐠: 𝐚 𝐠𝐫𝐞𝐞𝐧 𝐭𝐢𝐜𝐤 𝐭𝐡𝐚𝐭 𝐝𝐢𝐝 𝐧𝐨𝐭𝐡𝐢𝐧𝐠

I'm building a WhatsApp booking assistant for a hotel in n8n (WhatsApp Cloud API + Gemini AI agent + Google Sheets). Booking, reschedule and cancel all work now, but I hit a few failures that gave no error at all:

𝟏. 𝐖𝐞𝐛𝐡𝐨𝐨𝐤 𝐯𝐞𝐫𝐢𝐟𝐢𝐞𝐝, 𝐧𝐨𝐭𝐡𝐢𝐧𝐠 𝐭𝐫𝐢𝐠𝐠𝐞𝐫𝐬.

The fix was subscribing the WhatsApp Business Account to the app (subscribed_apps), not just setting up the webhook.

𝟐. 𝐒𝐡𝐞𝐞𝐭 𝐮𝐩𝐝𝐚𝐭𝐞 𝐬𝐡𝐨𝐰𝐞𝐝 𝐚 𝐠𝐫𝐞𝐞𝐧 𝐭𝐢𝐜𝐤 𝐛𝐮𝐭 𝐜𝐡𝐚𝐧𝐠𝐞𝐝 𝐧𝐨𝐭𝐡𝐢𝐧𝐠.

The Booking ID was a number in Google Sheets but text in the workflow, so Update Row matched zero rows. No error, empty output.

𝟑. 𝐓𝐡𝐞 𝐀𝐈 𝐚𝐠𝐞𝐧𝐭 𝐜𝐨𝐧𝐟𝐢𝐫𝐦𝐞𝐝 𝐭𝐡𝐢𝐧𝐠𝐬 𝐭𝐡𝐚𝐭 𝐧𝐞𝐯𝐞𝐫 𝐡𝐚𝐩𝐩𝐞𝐧𝐞𝐝.

It told the guest "done" even when the tool returned nothing. 😬

𝐖𝐡𝐚𝐭 𝐈 𝐝𝐢𝐝 𝐚𝐛𝐨𝐮𝐭 𝐢𝐭:

✅ Added rules to the agent prompt: read every tool result, and never confirm on an empty result

✅ Moved reschedule into a sub-workflow that validates dates first (invalid dates like "32 October" or past dates never reach the sheet)

✅ Added a "row actually updated?" check, so a wrong Booking ID returns "not found" instead of fake success

I tested it by asking for a booking on "32 October". The bot rejected the date and the sheet stayed untouched.

𝐍𝐨𝐰 𝐈'𝐦 𝐜𝐮𝐫𝐢𝐨𝐮𝐬 𝐚𝐛𝐨𝐮𝐭 𝐲𝐨𝐮𝐫 𝐬𝐞𝐭𝐮𝐩:

How do you catch silent failures (empty outputs, 0 rows matched) in your workflows?
Do you use an Error Trigger workflow, scheduled checks, or something else?
Has anyone tried an AI that reads failed executions and suggests fixes?

Would love to hear what works for you. 🙌

15 comments

𝐓𝐡𝐞 𝐬𝐜𝐚𝐫𝐢𝐞𝐬𝐭 𝐧𝟖𝐧 𝐛𝐮𝐠: 𝐚 𝐠𝐫𝐞𝐞𝐧 𝐭𝐢𝐜𝐤 𝐭𝐡𝐚𝐭 𝐝𝐢𝐝 𝐧𝐨𝐭𝐡𝐢𝐧𝐠