Can I get the file name of an uploaded attachment into a field?

Short answer: Not with a formula. Use an integration that copies the attachment's Name into a text field after submission, or a button that runs a short script.

Why it happens

• An attachment field holds a list of files, not text. A text formula fails with "Expression is returning 'JSONList' Allowed Types are 'String'".
• Field events can't be added to attachment fields, so nothing runs when a file is uploaded.

How to fix it

With an integration:

1. Create an integration with a Kissflow Process trigger such as When a draft item is submitted.
2. Add Update an item for the same item.
3. Map the attachment field's Name for the first file (index 0) into a text field.
4. Test the action, then turn on the integration.

With a button on the form:

1. Add a button and give it an On Click event.
2. Use a script that reads the field and writes the name, for example: let file = await kf.context.getField("Document"); kf.context.updateField({"Document_name": file[0]["name"]})
3. Replace Document and Document_name with your field IDs.