API Update: Multiple Contacts per Opportunity

Daria from Flowlu

Lead Product Marketing Manager

January 28, 2026

3 min read

This post explains what changed, how the new approach works, and what API users need to know.

What changed when creating opportunity links

Before

When creating or updating an opportunity, contact and organization links were set directly using fields in the opportunity:

• customer_id — used to link an organization
• contact_id — used to link a contact

This approach supported linking only two CRM accounts to an opportunity: one organization and one contact.

As a result, it was not possible to associate multiple contacts with the same opportunity.

Now

A new endpoint has been introduced:
crm/lead_accounts/create

This endpoint is designed specifically to create links between CRM accounts and an opportunity.

The key difference from the previous approach is support for multiple CRM accounts linked to a single opportunity, which enables linking multiple contacts to the same opportunity.

This change provides a more flexible and explicit way to manage opportunity relationships.

Request structure

The endpoint accepts the following parameters:

• lead_id — ID of the opportunity the account is linked to (required)
• account_id — ID of the CRM account being linked (required)
• account_type — type of CRM account (required):

1 — organization

2 — contact

• created_at — system field, filled automatically
• updated_at — system field, filled automatically

What changed when retrieving opportunity data

Before

When retrieving an opportunity, the response included:

• customer_id
• contact_id

This made it possible to retrieve only two linked CRM accounts: one organization and one contact.

Now

The fields customer_id and contact_id are no longer returned as part of the opportunity entity and are no longer used to retrieve links to CRM accounts.

To get information about CRM accounts linked to an opportunity, the API now provides dedicated endpoints:

• crm/lead_accounts/get/{id} — retrieve a specific opportunity–account link
• crm/lead_accounts/list — retrieve all CRM accounts linked to an opportunity

This approach fully supports multiple contact links and is the current, supported way to access relationship data.

Backward compatibility

Backward compatibility is not supported.

If your integration relies on:

• setting customer_id or contact_id when creating opportunities, or
• reading these fields from opportunity responses,

you must update it to use the new API approach.

If you don’t use the Flowlu API, this update does not affect you.

Documentation

Full technical details are available in the API documentation.