Set Participant Data action failing to persist custom JSON attributes in IVR flow

Architect & Flows
1

We’re trying to pass a custom JSON payload through an IVR flow using the Set Participant Data action in Architect. The goal is to store a complex object containing user preferences so it can be retrieved later by a downstream integration.

Here is the JSON structure we are attempting to set:

{
 "userPrefs": {
 "language": "en-US",
 "voiceLevel": "high",
 "skipIntro": true
 }
}

In the Set Participant Data action, we map the input variable customPayload to the participant data key userPrefs. We’ve verified that customPayload contains the correct JSON string before the action executes by logging it to the interaction log. The log shows the string is valid.

However, when we try to retrieve this data in the next node using a Data Action with the mapping participant.data.userPrefs, it returns null. We also tried accessing it via participant.data.custom.userPrefs but that also fails. The documentation is vague about the exact path structure for nested objects in participant data.

We’ve tried these steps:

  1. Ensuring the data type is set to String in the Set Participant Data action.
  2. Using a simple key-value pair like "test": "value" which works fine, but nesting breaks it.
  3. Checking for any syntax errors in the JSON string using an external validator.

Is there a specific format required for nested JSON in participant data? Or is there a limit to the depth of objects allowed? We’re on the latest version of CXone and haven’t seen this documented clearly. Any working examples or known limitations would be appreciated. The flow stops working because the downstream node can’t find the data, causing a fallback to the default greeting. We need this to work for personalization.

2

Check the data type mapping in Architect first. The Set Participant Data action expects the value to be a string if you’re passing raw JSON, not an object literal. If you drop a complex object directly into the value field without serializing it, the API often rejects it or truncates it.

You need to serialize that JSON payload into a string before setting it. In C#, using Newtonsoft.Json or System.Text.Json, it looks like this:

var prefs = new { language = "en-US", voiceLevel = "high", skipIntro = true };
string jsonPayload = JsonConvert.SerializeObject(prefs);

// Then pass jsonPayload as the string value to the Set Participant Data action
// via the Architect API or flow configuration

If you’re doing this inside Architect expressions, use the stringify() function if available for your expression context, or ensure the input variable is already a serialized string from an upstream HTTP action. The docs mention that participant data keys are limited in size, so keep the payload lean. It’s usually a type mismatch causing the 400 error here.