Direct answer
CTO as a Service is the broader category for outsourced technical leadership. Fractional CTO usually means a recurring part-time leader embedded with the founder and team. The right choice depends on whether you need one decision sprint or ongoing technical operating rhythm.
Use CTO as a Service for decision packages
A CTO as a Service engagement can be a focused audit, MVP scope, vendor review, hiring screen, or technical diligence package. It is useful when the founder needs a defined answer.
Use fractional CTO for recurring judgment
A fractional CTO retainer is better when decisions keep arriving every week: roadmap tradeoffs, sprint reviews, engineering interviews, AI vendors, data quality, launch risk, and GTM system choices.
How Fruitful Code scopes it
Most engagements start small: a paid diagnostic or architecture sprint. If the decision load is recurring, it becomes fractional CTO support with a monthly cadence.