When can suppliers be added to a negotiation?

Summary:

When can suppliers be added to a negotiation, and why is "Register Supplier" available during Technical Stage if they cannot join a Closed negotiation?

Content (please ensure you mask any confidential information):

I have a couple of questions regarding supplier participation stages in Oracle Sourcing:

• Timing for Adding Suppliers: At which specific stage of a negotiation can we invite suppliers? Is it strictly restricted to when the negotiation status is Active, or can suppliers be added at later stages?
• Technical Evaluation Stage Conflict: During the Technical Evaluation / Technical Stage, the system provides the option to Register a New Supplier