Resolves the URL experiment spans are exported to, as the url argument to
register().
Explicit code-level configuration outranks the ambient environment: a client
created with an explicit baseUrl exports its spans to that server, so a
PHOENIX_COLLECTOR_ENDPOINT left in the shell cannot silently retarget it.
When the base URL itself came from the environment, so does trace export:
returning undefined hands resolution to register(), which reads the
trace-export chain (PHOENIX_COLLECTOR_ENDPOINT, the OTel-standard
variables, then PHOENIX_ENDPOINT) exactly as a standalone register()
call would.
A base URL of unknown provenance — a hand-built client rather than one from
createClient() — counts as explicit, since only deliberate configuration
puts a URL there.
Resolves the URL experiment spans are exported to, as the
urlargument toregister().Explicit code-level configuration outranks the ambient environment: a client created with an explicit
baseUrlexports its spans to that server, so aPHOENIX_COLLECTOR_ENDPOINTleft in the shell cannot silently retarget it. When the base URL itself came from the environment, so does trace export: returningundefinedhands resolution toregister(), which reads the trace-export chain (PHOENIX_COLLECTOR_ENDPOINT, the OTel-standard variables, thenPHOENIX_ENDPOINT) exactly as a standaloneregister()call would.A base URL of unknown provenance — a hand-built client rather than one from
createClient()— counts as explicit, since only deliberate configuration puts a URL there.