Show A2A and FastAPI spans in Phoenix

[jenna-winkler]

Description

Phoenix currently filters out A2A and FastAPI spans, showing only OpenInference-compatible traces. This hides valuable instrumentation that's already being captured, making it harder to debug agent execution flow and infrastructure issues.

Why this matters

A2A and FastAPI instrumentation shows:

• A2A spans: Message handling, context propagation, task lifecycle, agent execution flow
• FastAPI spans: HTTP request/response details, routing, middleware execution, authentication

Without these spans, developers debugging issues like "why didn't my agent receive the message?" or "why did authentication fail?" have no visibility into the infrastructure layer - they only see framework operations in isolation. And it could be that they are not using a framework at all (custom code) and did not instrument their code.

Current state

The OTLP collector filters spans before sending to Phoenix:

• Only OpenInference spans (matching openinference.instrumentation.* pattern) pass through
• A2A spans (message handling, context propagation) are filtered out
• FastAPI spans (HTTP requests, routing) are filtered out
• Filter configured in helm/templates/collector/config.yaml under processors.filter/phoenix

Changes needed

1. Relax filter in OTLP collector config to allow A2A spans through
2. Relax filter to allow FastAPI spans through
3. Test that spans display properly in Phoenix UI alongside OpenInference traces
4. Update documentation on what instrumentation is visible

Acceptance criteria

• A2A spans visible in Phoenix traces
• FastAPI spans visible in Phoenix traces
• Spans properly nest with framework-specific instrumentation when present
• Phoenix UI remains usable with mixed span types
• Documentation updated showing what's automatically instrumented

[dosubot]

To show A2A and FastAPI spans in Phoenix, update the OTLP collector filter in helm/templates/collector/config.yaml under processors.filter/phoenix. The current filter only allows spans where instrumentation_scope.name matches OpenInference patterns, which excludes A2A and FastAPI spans. Remove or relax this filter so it does not restrict by instrumentation_scope.name—this will allow all spans, including A2A and FastAPI, to be forwarded to Phoenix and displayed in the UI. For example, you can comment out or delete the line:

- not(IsMatch(instrumentation_scope.name, "^openinference\\.instrumentation\\..*") or IsMatch(instrumentation_scope.name, "^@arizeai/openinference-instrumentation-.*") or instrumentation_scope.name == "crewai.telemetry")

After updating the filter, redeploy the collector. Then, trigger agent activity that generates A2A and FastAPI spans. In Phoenix, you should now see these spans alongside OpenInference traces. Check that A2A spans (message handling, context propagation, etc.) and FastAPI spans (HTTP requests, routing, middleware) appear and nest correctly with framework-specific instrumentation.

Phoenix is OpenInference-first, so non-OpenInference spans may not display as richly, but they will be visible for debugging infrastructure and agent execution flow issues. For documentation, update the telemetry/observability section (see issue #303) to clarify which spans are now visible by default and note any UI caveats with mixed span types. For more context, see this discussion and the current filter config.

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