fix: address review feedback for trace context propagation

- Remove unnecessary set_global_textmap override in Python tracing
  setup; the OTEL SDK already configures TraceContext + W3CBaggage
  propagators by default.
- Move trace header context utilities (TraceHeadersFrom/To) from
  go/core/pkg/auth into go/core/internal/tracecontext, since they
  are unrelated to auth.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Simon Zhu <simon.zhu@mongodb.com>

Author: syn-zhu

go/core/internal/httpserver/auth/authn.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"net/url"
 
+	"github.com/kagent-dev/kagent/go/core/internal/tracecontext"
 	"github.com/kagent-dev/kagent/go/core/pkg/auth"
 	"k8s.io/apimachinery/pkg/types"
 )
@@ -81,7 +82,7 @@ func (p *A2AAuthenticator) Wrap(next http.Handler) http.Handler {
 			if ts := r.Header.Get("tracestate"); ts != "" {
 				traceHeaders.Set("tracestate", ts)
 			}
-			r = r.WithContext(auth.TraceHeadersTo(r.Context(), traceHeaders))
+			r = r.WithContext(tracecontext.HeadersTo(r.Context(), traceHeaders))
 		}
 		authn.ServeHTTP(w, r)
 	})
@@ -122,7 +123,7 @@ func A2ARequestHandler(authProvider auth.AuthProvider, agentNns types.Namespaced
 		}
 
 		// Propagate W3C trace context headers captured from the incoming request.
-		if traceHeaders, ok := auth.TraceHeadersFrom(ctx); ok {
+		if traceHeaders, ok := tracecontext.HeadersFrom(ctx); ok {
 			for key, values := range traceHeaders {
 				for _, v := range values {
 					req.Header.Set(key, v)

go/core/internal/tracecontext/tracecontext.go

@@ -0,0 +1,23 @@
+package tracecontext
+
+import (
+	"context"
+	"net/http"
+)
+
+type traceHeadersKeyType struct{}
+
+var traceHeadersKey = traceHeadersKeyType{}
+
+// HeadersFrom retrieves W3C trace context headers (traceparent, tracestate)
+// that were captured from an incoming request.
+func HeadersFrom(ctx context.Context) (http.Header, bool) {
+	v, ok := ctx.Value(traceHeadersKey).(http.Header)
+	return v, ok && v != nil
+}
+
+// HeadersTo stores W3C trace context headers in the context so they can
+// be propagated to outgoing requests (e.g., from the controller to agent pods).
+func HeadersTo(ctx context.Context, headers http.Header) context.Context {
+	return context.WithValue(ctx, traceHeadersKey, headers)
+}

go/core/pkg/auth/auth.go

@@ -58,12 +58,8 @@ type Authorizer interface {
 // context utils
 
 type sessionKeyType struct{}
-type traceHeadersKeyType struct{}
 
-var (
-	sessionKey      = sessionKeyType{}
-	traceHeadersKey = traceHeadersKeyType{}
-)
+var sessionKey = sessionKeyType{}
 
 func AuthSessionFrom(ctx context.Context) (Session, bool) {
 	v, ok := ctx.Value(sessionKey).(Session)
@@ -74,19 +70,6 @@ func AuthSessionTo(ctx context.Context, session Session) context.Context {
 	return context.WithValue(ctx, sessionKey, session)
 }
 
-// TraceHeadersFrom retrieves W3C trace context headers (traceparent, tracestate)
-// that were captured from an incoming request.
-func TraceHeadersFrom(ctx context.Context) (http.Header, bool) {
-	v, ok := ctx.Value(traceHeadersKey).(http.Header)
-	return v, ok && v != nil
-}
-
-// TraceHeadersTo stores W3C trace context headers in the context so they can
-// be propagated to outgoing requests (e.g., from the controller to agent pods).
-func TraceHeadersTo(ctx context.Context, headers http.Header) context.Context {
-	return context.WithValue(ctx, traceHeadersKey, headers)
-}
-
 func AuthnMiddleware(authn AuthProvider) func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

python/packages/kagent-core/src/kagent/core/tracing/_utils.py

@@ -5,9 +5,6 @@
 from opentelemetry import _logs, trace
 from opentelemetry.exporter.otlp.proto.grpc._log_exporter import OTLPLogExporter
 from opentelemetry.exporter.otlp.proto.grpc.trace_exporter import OTLPSpanExporter
-from opentelemetry.propagate import set_global_textmap
-from opentelemetry.propagators.composite import CompositeHTTPPropagator
-from opentelemetry.trace.propagation.tracecontext import TraceContextTextMapPropagator
 from opentelemetry.instrumentation.fastapi import FastAPIInstrumentor
 from opentelemetry.instrumentation.httpx import HTTPXClientInstrumentor
 from opentelemetry.instrumentation.openai import OpenAIInstrumentor
@@ -80,9 +77,6 @@ def configure(name: str = "kagent", namespace: str = "kagent", fastapi_app: Fast
     # Configure tracing if enabled
     if tracing_enabled:
         logging.info("Enabling tracing")
-        # Set up W3C TraceContext propagator so incoming traceparent headers
-        # are extracted and outgoing requests carry them forward.
-        set_global_textmap(CompositeHTTPPropagator([TraceContextTextMapPropagator()]))
         # Check standard OTEL env vars: signal-specific endpoint first, then general endpoint
         trace_endpoint = (
             os.getenv("OTEL_EXPORTER_OTLP_TRACES_ENDPOINT")