AI assistants and AI agents are not the same product class. An AI assistant is a productivity-augmentation tool that suggests; an AI agent is an automation-execution system that acts on a downstream surface (tools, APIs, write-paths). Conflating them in 2026 enterprise procurement produces the most common single category mistake — buying an assistant under the assumption it is an agent, or buying an agent and governing it as if it were an assistant. The risk profile, contract structure, audit obligation, and TCO model differ categorically.

Claim is scoped to enterprise procurement decisions in 2026. Vendors are actively blurring the distinction in marketing — the line between 'assistant with tool use' and 'agent with bounded scope' has narrowed technically but is still procedurally distinct because of who signs the approval, what audit evidence is required, and what blast radius is being underwritten. 60-day review cadence. Watches: (1) regulatory frameworks that explicitly define one or both categories with operative legal effect (EU AI Act delegated acts especially), (2) major vendors collapsing the product naming, (3) NIST AI RMF revisions that adopt or reject the distinction.