Open Epic publishes one CapabilityStatement. Production has many. The map plots ~3,800 real hospital FHIR endpoints by the shape of the CapStmt they actually serve, harvested from the public Brands Bundles. Wisps of dots away from the modal cluster are deployments that diverge from what the vendor publishes for developers — exactly the surprises integrators hit on go-live.
Epic: 481 endpoints, 9 distinct CapStmt-shape clusters, 135 outliers. Oracle Health (Cerner): 2,810 endpoints across both provider (fhir-ehr) and patient (fhir-myrecord) host fronts, 4 shape clusters. MEDITECH: 542 endpoints, 6 clusters, 114 outliers. See Epic's nine production shapes, including the cluster of stripped-down deployments that advertise zero US Core profiles.
Epic (189 element deviations, 10 resources probed) and Oracle Health (Cerner) (176 element deviations across both provider and patient host fronts) are the rich overlay entries today. MEDITECH has CapabilityStatement provenance captured with the multi-patient sweep in progress. Each deviation entry covers element-level differences from US Core 6.1, auth overlay, OperationOutcome examples, search-param probes, pagination behavior, and reference resolution sampling.
Every claim carries a source URL, a verbatim quote, the verification method, and the date checked. No editorialized "this EHR is broken" takes — just observed behavior with receipts. Open source on GitHub under CC-BY 4.0 (data) + Apache 2.0 (tooling). Vendor PRs welcome.
Want to build against the map? Studio turns these overlays into runtime behavior at /v/epic-cluster-A/fhir/r4/…, /v/cerner-cluster-A/fhir/r4/…, and /v/meditech-cluster-A/fhir/r4/… — same patients, three EHR personalities at the wire.