fix: flaky tests for utf8 warning test

router-tests/telemetry/attribute_processor_test.go

@@ -188,33 +188,6 @@ func TestAttributeProcessorIntegration(t *testing.T) {
 		})
 	})
 
-	t.Run("invalid UTF-8 export error logs config hint", func(t *testing.T) {
-		t.Parallel()
-
-		testenv.Run(t, &testenv.Config{
-			TraceExporter: &invalidUTF8Exporter{},
-			LogObservation: testenv.LogObservationConfig{
-				Enabled:  true,
-				LogLevel: zapcore.ErrorLevel,
-			},
-		}, func(t *testing.T, xEnv *testenv.Environment) {
-			require.Eventually(t, func() bool {
-				res := xEnv.MakeGraphQLRequestOK(testenv.GraphQLRequest{
-					Query: `query { employees { id } }`,
-				})
-				if res.Response.StatusCode != 200 {
-					return false
-				}
-				logs := xEnv.Observer().FilterMessageSnippet("sanitize_utf8").All()
-				return len(logs) > 0
-			}, 10*time.Second, 500*time.Millisecond)
-
-			logs := xEnv.Observer().FilterMessageSnippet("sanitize_utf8").All()
-			require.NotEmpty(t, logs)
-			require.Equal(t, "otel error: traces export: string field contains invalid UTF-8: Enable 'telemetry.tracing.sanitize_utf8.enabled' in your config to sanitize invalid UTF-8 attributes.", logs[0].Message)
-		})
-	})
-
 	t.Run("IPAnonymization hashes IP attributes", func(t *testing.T) {
 		t.Parallel()
 
@@ -250,6 +223,31 @@ func TestAttributeProcessorIntegration(t *testing.T) {
 			require.Positive(t, hashedIPCount)
 		})
 	})
+
+	t.Run("invalid UTF-8 export error logs config hint", func(t *testing.T) {
+		t.Parallel()
+
+		testenv.Run(t, &testenv.Config{
+			TraceExporter: &invalidUTF8Exporter{},
+			LogObservation: testenv.LogObservationConfig{
+				Enabled:  true,
+				LogLevel: zapcore.ErrorLevel,
+			},
+		}, func(t *testing.T, xEnv *testenv.Environment) {
+			_, err := xEnv.MakeGraphQLRequest(testenv.GraphQLRequest{
+				Query: `query { employees { id } }`,
+			})
+			require.NoError(t, err)
+			require.Eventually(t, func() bool {
+				logs := xEnv.Observer().FilterMessageSnippet("sanitize_utf8").All()
+				return len(logs) > 0
+			}, 10*time.Second, 500*time.Millisecond)
+
+			logs := xEnv.Observer().FilterMessageSnippet("sanitize_utf8").All()
+			require.NotEmpty(t, logs)
+			require.Equal(t, "otel error: traces export: string field contains invalid UTF-8: Enable 'telemetry.tracing.sanitize_utf8.enabled' in your config to sanitize invalid UTF-8 attributes.", logs[0].Message)
+		})
+	})
 }
 
 // errInvalidUTF8 mimics google.golang.org/protobuf/internal/impl.errInvalidUTF8

router/pkg/trace/meter.go

@@ -169,7 +169,13 @@ func NewTracerProvider(ctx context.Context, config *ProviderConfig) (*sdktrace.T
 
 		// Either memory exporter or the configured exporters are used.
 		if config.MemoryExporter != nil {
-			opts = append(opts, sdktrace.WithSyncer(config.MemoryExporter))
+			// Use a custom span processor that routes export errors through the
+			// instance's logger instead of the global otel.Handle. This avoids
+			// flaky tests when parallel tests overwrite the global error handler.
+			opts = append(opts, sdktrace.WithSpanProcessor(&syncSpanProcessor{
+				exporter: config.MemoryExporter,
+				handler:  errHandler(config),
+			}))
 		} else {
 			for _, exp := range config.Config.Exporters {
 				if exp.Disabled {

router/pkg/trace/syncspan_test_exporter.go

@@ -0,0 +1,33 @@
+package trace
+
+import (
+	"context"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+)
+
+// syncSpanProcessor exports spans synchronously and routes errors through a
+// local handler instead of the global otel.Handle. This is equivalent to
+// sdktrace.WithSyncer but avoids global error handler races in parallel tests.
+type syncSpanProcessor struct {
+	exporter sdktrace.SpanExporter
+	handler  func(error)
+}
+
+func (p *syncSpanProcessor) OnStart(_ context.Context, _ sdktrace.ReadWriteSpan) {}
+
+func (p *syncSpanProcessor) OnEnd(s sdktrace.ReadOnlySpan) {
+	if !s.SpanContext().IsSampled() {
+		return
+	}
+	if err := p.exporter.ExportSpans(context.Background(), []sdktrace.ReadOnlySpan{s}); err != nil {
+		p.handler(err)
+	}
+}
+
+func (p *syncSpanProcessor) Shutdown(ctx context.Context) error {
+	return p.exporter.Shutdown(ctx)
+}
+
+func (p *syncSpanProcessor) ForceFlush(ctx context.Context) error {
+	return nil
+}