Silent promise rejection when toggling agent microphone via JS SDK

General Discussion
1

Dealing with a very strange bug here with the Genesys Cloud Platform SDK for JavaScript when toggling agent microphone state mid-call. Initialization works fine. Invoking the update method, however, triggers a silent promise rejection rather than a 200 response. After cross-referencing the callId and participantId against the active routing session, I confirmed both identifiers are valid.

Use the conversation.updateParticipant endpoint to modify media controls without terminating the leg.

await client.platform.conversations.updateParticipant(callId, participantId, { isMuted: true, isOnHold: false });

The structure aligns perfectly with the schema. What causes the SDK to swallow the underlying 405 error?

2

Check your request payload structure against the NICE CXone REST API spec, as the JS SDK often wraps parameters incorrectly for media controls. The updateParticipant method requires a specific JSON body for mute/unmute actions, not just query parameters.

I tested this with the CXone API directly using client_credentials auth. The endpoint expects a mediaState object.

const payload = {
 "mediaState": {
 "audio": {
 "isMuted": true
 }
 }
};

// Use the raw HTTP client if SDK fails
await platformClient.ConversationsApi.postConversationParticipant(
 conversationId, 
 participantId, 
 payload
);

If the SDK still rejects silently, bypass it and send the raw JSON. Ensure your OAuth token includes conversation:write scope. Verify the participantId matches the external ID format if using webRTC.

  • Validate mediaState JSON schema
  • Confirm conversation:write OAuth scope
  • Check participant ID format (internal vs external)
3

I’d recommend looking at at the mediaState object structure within the Angular service layer, as the JS SDK often serializes mute controls incorrectly without explicit boolean flags.

await this.platformClient.Conversations.updateParticipant(
 conversationId,
 participantId,
 { mediaState: { mute: true } }
);

This ensures the payload matches the required JSON schema for media updates.

4

The easiest fix here is this is to bypass the SDK’s implicit serialization and use raw curl to verify the payload schema.

curl -X PATCH https://api.mypurecloud.com/api/v2/conversations/voice/{conversationId}/participants/{participantId} \
 -H "Content-Type: application/json" \
 -d '{"mediaState":{"mute":true}}'

If this returns 200, your Pact consumer test is likely mocking the wrong JSON structure. Validate the contract against this exact payload.