Base OTLP export flags on effective writer and span metrics

Report otlp_traces_export_enabled from the resolved writer type
(OtlpWriter) rather than the OTLP exporter selection, since an explicit
dd.writer.type override wins over dd.trace.otel.exporter=otlp in
WriterFactory. Also report otlp_metrics_export_enabled when client-side
span metrics are enabled, since those are exported over OTLP via
OtlpStatsMetricWriter independently of the OTel metrics signal.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: bm1549

dd-trace-core/src/main/java/datadog/trace/core/StatusLogger.java

@@ -2,6 +2,7 @@
 
 import static datadog.trace.api.Config.isDatadogProfilerEnablementOverridden;
 import static datadog.trace.api.Config.isDatadogProfilerSafeInCurrentEnvironment;
+import static datadog.trace.bootstrap.instrumentation.api.WriterConstants.OTLP_WRITER_TYPE;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 
 import com.squareup.moshi.JsonAdapter;
@@ -159,9 +160,17 @@ public void toJson(JsonWriter writer, Config config) throws IOException {
     writer.name("data_streams_transaction_extractors");
     writer.value(config.getDataStreamsTransactionExtractors());
     writer.name("otlp_traces_export_enabled");
-    writer.value(config.isTraceOtlpExporterEnabled());
+    // Report the effective trace writer, not just the exporter selection: an explicit
+    // dd.writer.type override wins over dd.trace.otel.exporter=otlp in WriterFactory, so traces are
+    // only exported over OTLP when the resolved writer is actually the OtlpWriter.
+    writer.value(OTLP_WRITER_TYPE.equals(config.getWriterType()));
     writer.name("otlp_metrics_export_enabled");
-    writer.value(config.isMetricsOtelEnabled() && config.isMetricsOtlpExporterEnabled());
+    // Client-side trace span-metrics are exported over OTLP whenever span metrics are enabled
+    // (MetricsAggregatorFactory routes them through OtlpStatsMetricWriter), independently of the
+    // OTel metrics signal, so OR that path in alongside OTel-API metrics export.
+    writer.value(
+        (config.isMetricsOtelEnabled() && config.isMetricsOtlpExporterEnabled())
+            || config.isOtelTracesSpanMetricsEnabled());
     writer.name("otlp_logs_export_enabled");
     writer.value(config.isLogsOtelEnabled() && config.isLogsOtlpExporterEnabled());
 

dd-trace-core/src/test/java/datadog/trace/core/StatusLoggerTest.java

@@ -5,6 +5,7 @@
 import com.squareup.moshi.Moshi;
 import datadog.trace.api.Config;
 import datadog.trace.api.config.OtlpConfig;
+import datadog.trace.api.config.TracerConfig;
 import datadog.trace.test.junit.utils.config.WithConfig;
 import java.io.IOException;
 import java.util.Map;
@@ -52,6 +53,28 @@ void metricsAndLogsRequireOtelSignalEnabled() throws IOException {
     assertEquals(false, startupLog.get("otlp_logs_export_enabled"));
   }
 
+  @Test
+  @WithConfig(key = OtlpConfig.TRACE_OTEL_EXPORTER, value = "otlp")
+  @WithConfig(key = TracerConfig.WRITER_TYPE, value = "DDAgentWriter")
+  void tracesNotExportedWhenWriterTypeOverridesOtlpExporter() throws IOException {
+    // The OTLP trace exporter is selected, but an explicit dd.writer.type override wins in
+    // WriterFactory, so the effective writer is the DDAgentWriter and traces are not exported over
+    // OTLP.
+    Map<String, Object> startupLog = startupLog(Config.get());
+
+    assertEquals(false, startupLog.get("otlp_traces_export_enabled"));
+  }
+
+  @Test
+  @WithConfig(key = OtlpConfig.OTEL_TRACES_SPAN_METRICS_ENABLED, value = "true")
+  void metricsExportedWhenSpanMetricsEnabled() throws IOException {
+    // Span metrics are exported over OTLP via OtlpStatsMetricWriter whenever span metrics are
+    // enabled, independently of the OTel metrics signal, so metrics export should be reported.
+    Map<String, Object> startupLog = startupLog(Config.get());
+
+    assertEquals(true, startupLog.get("otlp_metrics_export_enabled"));
+  }
+
   @SuppressWarnings("unchecked")
   private static Map<String, Object> startupLog(Config config) throws IOException {
     String json =