### Answer [(1) ]() [(2) ]() The error "Cannot update response engine of agent version > 0" indicates that you're trying to modify the

response_engine

field on an agent version that's already been created (version 1 or higher) . Based on the Update Voice Agent and Update Chat Agent API documentation, once an agent has versions beyond 0, you cannot change its

response_engine

configuration. Solution: If you need to change the response engine, you have two options: 1. Create a new agent with the desired response engine configuration 2. Update only version 0 of the existing agent before any subsequent versions are created When updating agents with version > 0, you can modify other fields like

agent_name

,

voice_id

,

webhook_url

, etc., but the

response_engine

field is locked after the initial version.

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

​ To learn more, see the sources I considered: [[1] Update Chat Agent](https://docs.retellai.com/api-references/update-chat-agent) [[2] Update Voice Agent](https://docs.retellai.com/api-references/update-agent) ​

4. Optional: Specify a version when retrieving If you need to retrieve a specific version (not for updating, but for reference) , you can use the optional

version

query parameter: [(3) ]() The key point: you don't need to explicitly set a conversation flow to "draft" mode. After publishing, a new draft is automatically created for you to edit safely while the published version remains in production. [(2) ]() [(1) ]()

### Answer When updating a conversation flow, the system automatically works with draft versions. [(1) ]() Published versions cannot be changed—only the latest draft version can be modified. [(2) ]() To ensure you're updating a draft version: 1. Check the current version status Use the Get Conversation Flow API to retrieve the current version number: [(3) ]()

javascript
const conversationFlowResponse = await client.conversationFlow.retrieve('conversation_flow_id') ;
console.log(conversationFlowResponse.version) ;

2. Understand the versioning behavior When you publish a conversation flow (via the "Deployment" button in the dashboard) , it creates a new published version and automatically generates a new draft for future edits. [(2) ]() [(1) ]() The conversation flow is "always in draft"—when you publish, it creates a new draft that you can edit. [(1) ]() 3. Update the conversation flow When calling the Update Conversation Flow API, you're always updating the current draft version: [(4) ]()

javascript
const conversationFlowResponse = await client.conversationFlow.update('conversation_flow_id') ;

​ To learn more, see the sources I considered: [[1] Discord message from @mauvatar on 2026-02-03](https://discord.com/channels/1186424376300679209/1186462578310910112/1468376961603862692) [[2] Setup versioning for agents](https://docs.retellai.com/agent/version) [[3] Get Conversation Flow](https://docs.retellai.com/api-references/get-conversation-flow) [[4] Update Conversation Flow](https://docs.retellai.com/api-references/update-conversation-flow) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer I don't have information in the available sources about how the API handles draft creation after publishing a conversation flow or how to explicitly create a draft version via API to avoid the "Cannot update published conversation flow" error. The available API documentation covers retrieving [(1) ]() , creating [(2) ]() , updating [(3) ]() , and listing [(4) ]() conversation flows, but doesn't specify the workflow for creating draft versions programmatically after publishing. Check out these potentially useful sources: [Get Conversation Flow]() , [Update Conversation Flow]() , [Create Conversation Flow]() Would you like me to try to answer generally based on my knowledge instead? For additional help with API-specific workflows, visit [Documentation]() or [Hire certified Retell partner]() .

​ To learn more, see the sources I considered: [[1] Get Conversation Flow](https://docs.retellai.com/api-references/get-conversation-flow) [[2] Create Conversation Flow](https://docs.retellai.com/api-references/create-conversation-flow) [[3] Update Conversation Flow](https://docs.retellai.com/api-references/update-conversation-flow) [[4] List Conversation Flows](https://docs.retellai.com/api-references/list-conversation-flows) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

Thanks for the follow-up, @Nicolas. I'll get back to you soon.

​ To learn more, see the sources I considered: [[1] Publish Agent](https://docs.retellai.com/api-references/publish-agent) [[2] Setup versioning for agents](https://docs.retellai.com/agent/version) [[3] Get Agent Versions](https://docs.retellai.com/api-references/get-agent-versions) [[4] List Voice Agents](https://docs.retellai.com/api-references/list-agents) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.