Choose the model around the responsibility that is missing. You may need delivery of a defined result, additional engineering judgment inside your team, an independent quality view or someone to own technical and product decisions.
Match the gap to the model - A defined build or milestone: agree an outcome, acceptance criteria, inputs and handover. Discovery may be needed to establish a credible scope first. - Support for an existing team: keep your product ownership and discuss a bounded contribution. Clarify interfaces, review, release access and who resolves conflicting priorities. - Software QA: get focused investigation and evidence about a product you already have. Decide separately who implements fixes and verifies them. - Fractional leadership: address architecture, roadmap, vendor coordination or engineering decisions that lack an accountable owner. The role and authority need to be explicit.
A product whose customer need is still uncertain may need validation before a full build. More developers will not resolve an unclear decision on their own.
Use the service overview to compare the roles and the pricing page for current commercial models. Titles do not define the whole engagement: responsibilities, staffing, availability and deliverables belong in the offer.
A useful starting sentence: “Our team can already handle [work], but nobody currently owns [decision or task].” This helps choose the smallest useful contribution without duplicating your team's work.