05.08.2026: OTLP Project Routing via HTTP Header

Route OTLP traces to a named Phoenix project by setting the x-project-name HTTP header — no resource attribute required.

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.