WhatsApp Flows: validation errors not displaying under form fields

I'm building a WhatsApp Flow with a data_exchange action. When validating user input (e.g. time format on the BIRTH_DETAILS screen), I return a 200 OK response with the expected JSON format:

{
  "version": "3.0",
  "screen": "BIRTH_DETAILS",
  "data": {
    "error_messages": {
      "birth_time": "Time format invalid — please use 14:30"
    }
  }
}

The birth_time field is correctly defined in the Flow screen:

    "error_messages": {
      "type": "object",
      "__example__": {
        "birth_time": "Please enter a valid time (e.g., 14:30)"
        }
    }
.............................
{
  "type": "TextInput",
  "name": "birth_time",
  "required": true,
  "label": "Your birth time"
}

My endpoint encrypts the response as expected using AES-128-GCM and returns it directly in the body (with isBase64Encoded: false).

✅ What works:

• The validation does prevent the user from proceeding, which suggests the Flow backend received and processed the response.
• The screen does not reload or show errors, but the “Continue” button stays stuck, which is expected behavior on invalid input.

❌ What doesn’t work:

• No error message is shown under the birth_time field.
• No pop-up or general alert/error appears.

I'm wondering if this is:

• A known limitation or bug
• A formatting issue
• A caching problem on the client
• Or something I missed in the Flow schema

Has anyone successfully displayed field-level errors in WhatsApp Flows during data_exchange?

Thanks for all those details. I just had a look at your Flow, and you need to either:

• Wrap your components in a Form, and provide "error-messages" as a property.

• Provide each error individually to each component with the property "error-message".

Right now you've defined "error_messages" in "data", but you are not making use of it.