Telegram chatbot in callin.io with OpenAI: Voice message error 'No prompt specified' despite transcription

Hello,

I’m currently developing a conversational agent on callin.io, connected to Telegram, with the goal of receiving messages (text or voice) and automatically replying via the AI Agent node.

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What works:

When I send a text message via Telegram:

• The message is successfully captured,
• It is passed to the AI Agent node,
• The prompt is recognized ({{ $json.message.text }}), and the response is correctly sent back via Telegram.

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Issue encountered:

When I send a voice message, I get the following error from the AI Agent node:

Problem in node 'AI Agent'
No prompt specified

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Details:

• The voice message is successfully downloaded using Telegram -> Get File.
• The transcription is correctly performed using OpenAI - Transcribe Recording, and the text field is present in the output.
• I use {{ $json.text }} in the Prompt (User Message) field of the AI Agent node.
• However, the "No prompt specified" error appears only with voice messages.
• The text field is clearly visible in the output JSON of the previous node.

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What I’ve tried:

• Added a Switch to handle text and voice messages separately.
• Used {{ $json.text }} for voice and {{ $json.message.text }} for text.
• Added a Set node to unify both into a common field like prompt = {{ $json.text }}.
• Set "language": "fr" in the transcription node to force French.

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What I need:

I want the AI Agent node to dynamically handle either case:

• Use message.text when the message is a text,
• Use text (transcription result) when it’s a voice message,
• And generate a response in both scenarios without triggering the "No prompt specified" error.

Any suggestions or working setups are welcome. Thanks in advance!

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