05.08.2026: OTLP Project Routing via HTTP Header

Available in arize-phoenix 15.5.0+

Phoenix now reads the x-project-name HTTP header on incoming OTLP trace exports and routes all spans in the request to that project. The header takes precedence over the openinference.project.name resource attribute, so tools like the OpenTelemetry Collector, Openclaw, and Daytona can route traces to the right project without modifying the instrumented application.

Setting the header#

OpenTelemetry Collector

exporters:  otlphttp:    endpoint: http://localhost:6006    headers:      x-project-name: my-project

Environment variable

OTEL_EXPORTER_OTLP_HEADERS="x-project-name=my-project"

Precedence rules#

Source	Priority
`x-project-name` HTTP header	Highest
`openinference.project.name` resource attribute	Second
Server default project	Fallback

Every span in the request goes to the same project when the header is set, regardless of what individual spans report in their resource attributes.

Bug fix: built-in evaluator preserved on dataset evaluator delete#

Available in arize-phoenix 15.5.1+

Deleting a dataset evaluator link no longer removes the underlying evaluator — it stays available for other datasets.