Add OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT environment variable support to MEAI telemetry

src/Libraries/Microsoft.Extensions.AI/ChatCompletion/FunctionInvokingChatClient.cs

@@ -1128,7 +1128,7 @@ FunctionResultContent CreateFunctionResultContent(FunctionInvocationResult resul
             startingTimestamp = Stopwatch.GetTimestamp();
             if (_logger.IsEnabled(LogLevel.Trace))
             {
-                LogInvokingSensitive(context.Function.Name, LoggingHelpers.AsJson(context.Arguments, context.Function.JsonSerializerOptions));
+                LogInvokingSensitive(context.Function.Name, TelemetryHelpers.AsJson(context.Arguments, context.Function.JsonSerializerOptions));
             }
             else
             {
@@ -1169,7 +1169,7 @@ FunctionResultContent CreateFunctionResultContent(FunctionInvocationResult resul
 
                 if (result is not null && _logger.IsEnabled(LogLevel.Trace))
                 {
-                    LogInvocationCompletedSensitive(context.Function.Name, elapsed, LoggingHelpers.AsJson(result, context.Function.JsonSerializerOptions));
+                    LogInvocationCompletedSensitive(context.Function.Name, elapsed, TelemetryHelpers.AsJson(result, context.Function.JsonSerializerOptions));
                 }
                 else
                 {

src/Libraries/Microsoft.Extensions.AI/ChatCompletion/LoggingChatClient.cs

@@ -169,7 +169,7 @@ public override async IAsyncEnumerable<ChatResponseUpdate> GetStreamingResponseA
         }
     }
 
-    private string AsJson<T>(T value) => LoggingHelpers.AsJson(value, _jsonSerializerOptions);
+    private string AsJson<T>(T value) => TelemetryHelpers.AsJson(value, _jsonSerializerOptions);
 
     [LoggerMessage(LogLevel.Debug, "{MethodName} invoked.")]
     private partial void LogInvoked(string methodName);

src/Libraries/Microsoft.Extensions.AI/ChatCompletion/OpenTelemetryChatClient.cs

@@ -110,13 +110,16 @@ protected override void Dispose(bool disposing)
     /// <value>
     /// <see langword="true"/> if potentially sensitive information should be included in telemetry;
     /// <see langword="false"/> if telemetry shouldn't include raw inputs and outputs.
-    /// The default value is <see langword="false"/>.
+    /// The default value is <see langword="false"/>, unless the <c>OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT</c>
+    /// environment variable is set to "true" (case-insensitive).
     /// </value>
     /// <remarks>
     /// By default, telemetry includes metadata, such as token counts, but not raw inputs
     /// and outputs, such as message content, function call arguments, and function call results.
+    /// The default value can be overridden by setting the <c>OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT</c>
+    /// environment variable to "true". Explicitly setting this property will override the environment variable.
     /// </remarks>
-    public bool EnableSensitiveData { get; set; }
+    public bool EnableSensitiveData { get; set; } = TelemetryHelpers.EnableSensitiveDataDefault;
 
     /// <inheritdoc/>
     public override object? GetService(Type serviceType, object? serviceKey = null) =>

src/Libraries/Microsoft.Extensions.AI/Embeddings/OpenTelemetryEmbeddingGenerator.cs

@@ -89,13 +89,16 @@ public OpenTelemetryEmbeddingGenerator(IEmbeddingGenerator<TInput, TEmbedding> i
     /// <value>
     /// <see langword="true"/> if potentially sensitive information should be included in telemetry;
     /// <see langword="false"/> if telemetry shouldn't include raw inputs and outputs.
-    /// The default value is <see langword="false"/>.
+    /// The default value is <see langword="false"/>, unless the <c>OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT</c>
+    /// environment variable is set to "true" (case-insensitive).
     /// </value>
     /// <remarks>
     /// By default, telemetry includes metadata, such as token counts, but not raw inputs
     /// and outputs or additional options data.
+    /// The default value can be overridden by setting the <c>OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT</c>
+    /// environment variable to "true". Explicitly setting this property will override the environment variable.
     /// </remarks>
-    public bool EnableSensitiveData { get; set; }
+    public bool EnableSensitiveData { get; set; } = TelemetryHelpers.EnableSensitiveDataDefault;
 
     /// <inheritdoc/>
     public override object? GetService(Type serviceType, object? serviceKey = null) =>

src/Libraries/Microsoft.Extensions.AI/Image/LoggingImageGenerator.cs

@@ -102,7 +102,7 @@ public override async Task<ImageGenerationResponse> GenerateAsync(
         }
     }
 
-    private string AsJson<T>(T value) => LoggingHelpers.AsJson(value, _jsonSerializerOptions);
+    private string AsJson<T>(T value) => TelemetryHelpers.AsJson(value, _jsonSerializerOptions);
 
     [LoggerMessage(LogLevel.Debug, "{MethodName} invoked.")]
     private partial void LogInvoked(string methodName);

src/Libraries/Microsoft.Extensions.AI/OpenTelemetryConsts.cs

@@ -14,6 +14,9 @@ internal static class OpenTelemetryConsts
     public const string SecondsUnit = "s";
     public const string TokensUnit = "token";
 
+    /// <summary>Environment variable name for controlling whether sensitive content should be captured in telemetry by default.</summary>
+    public const string GenAICaptureMessageContentEnvVar = "OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT";
+
     public const string ToolTypeFunction = "function";
 
     public const string TypeText = "text";

src/Libraries/Microsoft.Extensions.AI/SpeechToText/LoggingSpeechToTextClient.cs

@@ -179,7 +179,7 @@ public override async IAsyncEnumerable<SpeechToTextResponseUpdate> GetStreamingT
         }
     }
 
-    private string AsJson<T>(T value) => LoggingHelpers.AsJson(value, _jsonSerializerOptions);
+    private string AsJson<T>(T value) => TelemetryHelpers.AsJson(value, _jsonSerializerOptions);
 
     [LoggerMessage(LogLevel.Debug, "{MethodName} invoked.")]
     private partial void LogInvoked(string methodName);

src/Libraries/Microsoft.Extensions.AI/LoggingHelpers.cs → src/Libraries/Microsoft.Extensions.AI/TelemetryHelpers.cs

@@ -4,14 +4,22 @@
 #pragma warning disable CA1031 // Do not catch general exception types
 #pragma warning disable S108 // Nested blocks of code should not be left empty
 #pragma warning disable S2486 // Generic exceptions should not be ignored
+#pragma warning disable SA1623 // Property summary documentation should match accessors
 
+using System;
 using System.Text.Json;
 
 namespace Microsoft.Extensions.AI;
 
-/// <summary>Provides internal helpers for implementing logging.</summary>
-internal static class LoggingHelpers
+/// <summary>Provides internal helpers for implementing telemetry.</summary>
+internal static class TelemetryHelpers
 {
+    /// <summary>Gets a value the OpenTelemetry clients should use for their EnableSensitiveData property's default value.</summary>
+    /// <remarks>Defaults to false. May be overridden by setting the OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT environment variable to "true".</remarks>
+    public static bool EnableSensitiveDataDefault { get; } =
+        Environment.GetEnvironmentVariable(OpenTelemetryConsts.GenAICaptureMessageContentEnvVar) is string envVar &&
+        string.Equals(envVar, "true", StringComparison.OrdinalIgnoreCase);
+
     /// <summary>Serializes <paramref name="value"/> as JSON for logging purposes.</summary>
     public static string AsJson<T>(T value, JsonSerializerOptions? options)
     {