.NET: Use OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT to control sensitive data capture in telemetry

[singankit]

Summary

The agent framework should respect the OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT environment variable to control whether sensitive data (raw inputs/outputs) is included in telemetry, consistent with the approach used in Microsoft.Extensions.AI.OpenTelemetryChatClient.

Reference

See: https://learn.microsoft.com/en-us/dotnet/api/microsoft.extensions.ai.opentelemetrychatclient.enablesensitivedata?view=net-10.0-pp

Desired Behavior

• By default, telemetry should include metadata (e.g., token counts) but not raw inputs and outputs (message content, function call arguments, function call results).
• If the environment variable OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT is set to "true" (case-insensitive), sensitive data should be captured in telemetry.
• An explicit programmatic override (e.g., a property or configuration option) should take precedence over the environment variable.

Why

This aligns with the OpenTelemetry GenAI semantic conventions and provides a standardized, user-controlled mechanism for opting into sensitive data capture — important for debugging while maintaining privacy by default.

[challaravinath]

Did some analysis and here are my Observations:

Observation 1 : Env var is already handled

OpenTelemetryAgent.EnableSensitiveData delegates entirely to _otelClient.EnableSensitiveData, which defaults to TelemetryHelpers.EnableSensitiveDataDefault. Confirmed in the M.E.AI source

Observation 2 : There is a real gap in the auto-wiring path

When __autoWireChatClient = true, GetRunOptionsWithChatClientWiring_ creates a new inner OpenTelemetryChatClient with only sourceName EnableSensitiveData is not propagated: cc.AsBuilder().UseOpenTelemetry(sourceName: sourceName).Build();

So if a user explicitly sets agent.EnableSensitiveData = true, the outer _otelClient respects it but the auto-wired inner client does not they are out of sync.

The fix would be to capture and propagate the value:

 static IChatClient WrapIfNeeded(IChatClient cc, string sourceName, bool enableSensitiveData) =>
      cc.GetService(typeof(OpenTelemetryChatClient)) is not null
          ? cc
          : cc.AsBuilder()
              .UseOpenTelemetry(sourceName: sourceName, configure: o =>
              {
                  _o.EnableSensitiveData = enableSensitiveData;_  //**<-- propagate it**
              })
              .Build();

Happy to raise a PR for Observation 2 if confirmed. I'd like to claim this one.