Arize Phoenix handler for AgentObs.

This handler translates AgentObs telemetry events into OpenTelemetry spans with OpenInference semantic conventions, suitable for export to Arize Phoenix or any OpenInference-compatible observability platform.

Configuration

config :agent_obs,
  handlers: [AgentObs.Handlers.Phoenix]

config :agent_obs, AgentObs.Handlers.Phoenix,
  endpoint: "http://localhost:6006/v1/traces",
  api_key: nil  # Optional, for authenticated Phoenix instances

OpenTelemetry SDK Configuration

This handler requires the OpenTelemetry SDK to be configured in your application. Add to config/runtime.exs:

config :opentelemetry,
  span_processor: :batch,
  resource: [service: [name: "my_llm_agent"]]

config :opentelemetry_exporter,
  otlp_protocol: :http_protobuf,
  otlp_endpoint: System.fetch_env!("ARIZE_PHOENIX_OTLP_ENDPOINT"),
  otlp_headers: [
    {"authorization", "Bearer #{System.get_env("ARIZE_PHOENIX_API_KEY")}"}
  ]

How It Works

1. Attaches to all AgentObs telemetry events (:agent, :tool, :llm, :prompt)
2. On :start events, creates an OpenTelemetry span and stores context in process dictionary
3. On :stop events, adds attributes and ends the span
4. On :exception events, records the exception and marks span as errored
5. Uses Phoenix.Translator to convert metadata to OpenInference attributes

Span Context Management

Spans are stored in the process dictionary with a unique key per event type. This allows nested instrumentation (e.g., agent -> llm -> tool) to create proper parent-child span relationships automatically.