The strongest signals
Common signals include a live opportunity with a technical solution component, a proposal that needs implementation credibility, a client asking for working software, or several specialist capabilities that are difficult to staff permanently.
What the consulting firm should retain
The consulting firm should retain strategic leadership, relationship ownership, and the narrative of the engagement. The delivery partner should make technical responsibilities, visibility, and handover explicit.
When to involve the delivery partner
Early involvement is valuable because it improves the solution shape, feasibility, timeline, and proposal language. The partner can still join later, but there is less room to influence scope and risk.