A US clinic network's legal team has confirmed a business associate agreement covering the Claude model endpoint the team uses. The engineering plan also sends full request and response payloads to a third-party tracing service, and uses a public MCP server to normalize medication names. What is the most important architectural change before PHI flows?

Answer: D — Keep PHI out of the tracing service and MCP server, or bring each under an appropriate agreement

HIPAA obligations follow the PHI. Every vendor that receives it needs to be covered, or must not receive it, for example through metadata-only tracing and de-identified inputs to the MCP server. (a) wrongly assumes one covered hop covers the whole system. (b) is a necessary safeguard but doesn't address disclosure to parties without an agreement. (c) is unrelated to the compliance gap.