The Envoy span API:

Does not support getting/setting baggage. At Lyft we will need to make use of this against the OT driver so will need to add this support. It should be fairly trivial to call through to the OT driver code for this but will need to figure out how to handle this generically for tracers that do not support baggage (possibly a feature capability bit or similar).

cc @rnburn @objectiser @garrettheel