Read the US Core 8.0.0-ballot Change Log (published January 2025 for the STU 8 ballot) and the 'Changes Between Versions' page to enumerate added, modified, and removed profiles compared to STU 7 (7.0.0)
Note the primary driver for 8.0.0: alignment with USCDI v5 data classes, which introduced new profiles and extended existing ones beyond what USCDI v4 required in 7.0.0
Check the Patient profile changes: the most significant breaking change is that Patient.gender was made optional (no longer a required must-support element) to comply with EO 14168; the new US Core Individual Sex Extension replaced the deprecated US Core Sex Extension
Review newly added or substantially revised profiles introduced for USCDI v5 elements; compare the Observation Summary Table between 7.0.0 and 8.0.0 to identify new Observation sub-profiles
Run the FHIR validator with the 8.0.0-ballot package (hl7.fhir.us.core#8.0.0-ballot) against resources that passed 7.0.0 validation to discover new must-support obligations or binding changes
Update server CapabilityStatement conformance claims from US Core 7.0.0 to 8.0.0 profiles and re-run conformance testing with the updated Touchstone or HL7 test scripts
Known gotchas
Making Patient.gender optional is a breaking behavioral change for clients that assumed its presence — downstream applications must handle its absence without erroring
The US Core Sex Extension was deprecated in 8.0.1 in favor of the new US Core Individual Sex Extension; implementers who adopted 8.0.0-ballot need to apply the 8.0.1 fix to avoid validation conflicts
US Core 8.0.0 targets FHIR R4 (not R5 or R6) — the separate R6 prototype branch (8.0.0-R6) is a research prototype and is not the balloted 8.0.0 specification
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp