In the main.js file, where it instantiates the Medplum client, you can pass in a different

baseUrl

. If you're running medplum locally with the default ports, you can pass in

baseUrl: "http://localhost:8103"

. https://github.com/medplum/foomedical/blob/c2dbb1a215acbfc1b2a9503997cd23e687c3dd10/src/main.tsx#L9-L11