fix: propagate authorization header to subagents

go/adk/pkg/tools/remote_a2a_tool.go

@@ -11,6 +11,7 @@ import (
 	a2atype "github.com/a2aproject/a2a-go/a2a"
 	"github.com/a2aproject/a2a-go/a2aclient"
 	"github.com/a2aproject/a2a-go/a2aclient/agentcard"
+	"github.com/a2aproject/a2a-go/a2asrv"
 	"github.com/kagent-dev/kagent/go/adk/pkg/a2a"
 	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
 	"google.golang.org/adk/tool"
@@ -20,18 +21,59 @@ import (
 // userIDContextKey is the context key for passing the session user_id to the subagent.
 type userIDContextKey struct{}
 
-// userIDForwardingInterceptor forwards the session user_id as an x-user-id header.
-type userIDForwardingInterceptor struct {
+// authorizationHeaderContextKey is the context key for passing the parent Authorization header to the subagent.
+type authorizationHeaderContextKey struct{}
+
+// subagentForwardingInterceptor forwards x-user-id and the parent Authorization header.
+// Only Authorization is promoted from parent request metadata; all other headers stay scoped to the parent call.
+type subagentForwardingInterceptor struct {
 	a2aclient.PassthroughInterceptor
 }
 
-func (u *userIDForwardingInterceptor) Before(ctx context.Context, req *a2aclient.Request) (context.Context, error) {
+func (u *subagentForwardingInterceptor) Before(ctx context.Context, req *a2aclient.Request) (context.Context, error) {
 	if uid, ok := ctx.Value(userIDContextKey{}).(string); ok && uid != "" {
 		req.Meta.Append("x-user-id", uid)
 	}
+	if authorization, ok := ctx.Value(authorizationHeaderContextKey{}).(string); ok && authorization != "" {
+		for key := range req.Meta {
+			if strings.EqualFold(key, "authorization") {
+				delete(req.Meta, key)
+			}
+		}
+		req.Meta.Append("Authorization", authorization)
+	}
 	return ctx, nil
 }
 
+func subagentCallContext(ctx tool.Context) context.Context {
+	sendCtx := context.WithValue(ctx, userIDContextKey{}, ctx.UserID())
+	if authorization := authorizationHeaderFromContext(ctx); authorization != "" {
+		sendCtx = context.WithValue(sendCtx, authorizationHeaderContextKey{}, authorization)
+	}
+	return sendCtx
+}
+
+func authorizationHeaderFromContext(ctx context.Context) string {
+	callCtx, ok := a2asrv.CallContextFrom(ctx)
+	if !ok {
+		return ""
+	}
+	meta := callCtx.RequestMeta()
+	if meta == nil {
+		return ""
+	}
+	values, ok := meta.Get("authorization")
+	if !ok {
+		return ""
+	}
+	for _, value := range values {
+		if strings.TrimSpace(value) != "" {
+			return value
+		}
+	}
+	return ""
+}
+
 // remoteA2AInput is the typed argument for the remote A2A function tool.
 type remoteA2AInput struct {
 	Request string `json:"request"`
@@ -121,7 +163,7 @@ func (s *remoteA2AState) ensureClient(ctx context.Context) (*a2aclient.Client, e
 		}
 		opts = append(opts, a2aclient.WithInterceptors(
 			a2aclient.NewStaticCallMetaInjector(meta),
-			&userIDForwardingInterceptor{},
+			&subagentForwardingInterceptor{},
 		))
 
 		client, err := a2aclient.NewFromCard(ctx, card, opts...)
@@ -159,7 +201,7 @@ func (s *remoteA2AState) handleFirstCall(ctx tool.Context, requestText string) (
 	)
 	message.ContextID = s.lastContextID
 
-	sendCtx := context.WithValue(ctx, userIDContextKey{}, ctx.UserID())
+	sendCtx := subagentCallContext(ctx)
 	result, err := client.SendMessage(sendCtx, &a2atype.MessageSendParams{Message: message})
 	if err != nil {
 		slog.Error("Remote agent request failed", "tool", s.name, "error", err)
@@ -209,7 +251,7 @@ func (s *remoteA2AState) handleResume(ctx tool.Context) (map[string]any, error)
 		return map[string]any{"error": err.Error()}, nil
 	}
 
-	sendCtx := context.WithValue(ctx, userIDContextKey{}, ctx.UserID())
+	sendCtx := subagentCallContext(ctx)
 	result, err := client.SendMessage(sendCtx, &a2atype.MessageSendParams{Message: message})
 	if err != nil {
 		slog.Error("Remote agent resume failed", "tool", subagentName, "error", err)

go/adk/pkg/tools/remote_a2a_tool_test.go

@@ -0,0 +1,65 @@
+package tools
+
+import (
+	"context"
+	"reflect"
+	"testing"
+
+	"github.com/a2aproject/a2a-go/a2aclient"
+	"github.com/a2aproject/a2a-go/a2asrv"
+)
+
+func TestSubagentForwardingInterceptorForwardsUserIDAndAuthorization(t *testing.T) {
+	ctx := context.WithValue(context.Background(), userIDContextKey{}, "user-1")
+	ctx = context.WithValue(ctx, authorizationHeaderContextKey{}, "Bearer parent-token")
+
+	req := &a2aclient.Request{Meta: a2aclient.CallMeta{}}
+	_, err := (&subagentForwardingInterceptor{}).Before(ctx, req)
+	if err != nil {
+		t.Fatalf("Before() error = %v", err)
+	}
+
+	if got, want := req.Meta.Get("x-user-id"), []string{"user-1"}; !reflect.DeepEqual(got, want) {
+		t.Fatalf("x-user-id = %v, want %v", got, want)
+	}
+	if got, want := req.Meta.Get("authorization"), []string{"Bearer parent-token"}; !reflect.DeepEqual(got, want) {
+		t.Fatalf("authorization = %v, want %v", got, want)
+	}
+}
+
+func TestSubagentForwardingInterceptorReplacesExistingAuthorization(t *testing.T) {
+	ctx := context.WithValue(context.Background(), authorizationHeaderContextKey{}, "Bearer parent-token")
+
+	req := &a2aclient.Request{Meta: a2aclient.CallMeta{}}
+	req.Meta.Append("Authorization", "Bearer stale-token")
+
+	_, err := (&subagentForwardingInterceptor{}).Before(ctx, req)
+	if err != nil {
+		t.Fatalf("Before() error = %v", err)
+	}
+
+	if got, want := req.Meta.Get("authorization"), []string{"Bearer parent-token"}; !reflect.DeepEqual(got, want) {
+		t.Fatalf("authorization = %v, want %v", got, want)
+	}
+}
+
+func TestAuthorizationHeaderFromContext(t *testing.T) {
+	ctx, _ := a2asrv.WithCallContext(context.Background(), a2asrv.NewRequestMeta(map[string][]string{
+		"Authorization": []string{"Bearer parent-token"},
+		"X-Other":      []string{"ignored"},
+	}))
+
+	if got, want := authorizationHeaderFromContext(ctx), "Bearer parent-token"; got != want {
+		t.Fatalf("authorizationHeaderFromContext() = %q, want %q", got, want)
+	}
+}
+
+func TestAuthorizationHeaderFromContextWithoutHeader(t *testing.T) {
+	ctx, _ := a2asrv.WithCallContext(context.Background(), a2asrv.NewRequestMeta(map[string][]string{
+		"X-Other": []string{"ignored"},
+	}))
+
+	if got := authorizationHeaderFromContext(ctx); got != "" {
+		t.Fatalf("authorizationHeaderFromContext() = %q, want empty", got)
+	}
+}

python/packages/kagent-adk/src/kagent/adk/_remote_a2a_tool.py

@@ -56,27 +56,51 @@
 logger = logging.getLogger("kagent_adk." + __name__)
 
 _USER_ID_CONTEXT_KEY = "x-user-id"
+_HEADERS_CONTEXT_KEY = "headers"
 _SOURCE_HEADER = "x-kagent-source"
 _SOURCE_SUBAGENT = "agent"
 
 
 class _SubagentInterceptor(ClientCallInterceptor):
     """
-    Injects the authenticated user's ID as an ``x-user-id`` HTTP header and
-    marks the request as originating from an agent call via
-    ``x-kagent-source: agent`` on every outgoing A2A request.
+    Injects the authenticated user's ID as an ``x-user-id`` HTTP header,
+    forwards the parent ``Authorization`` header when available, and marks
+    the request as originating from an agent call via ``x-kagent-source:
+    agent`` on every outgoing A2A request.
+
+    Only ``Authorization`` is promoted from parent session headers; all
+    other session headers remain context-only.
     """
 
     async def intercept(self, method_name, request_payload, http_kwargs, agent_card, context):
         headers = dict(http_kwargs.get("headers", {}))
         # Always mark requests from a parent agent tool as subagent-originated
         headers[_SOURCE_HEADER] = _SOURCE_SUBAGENT
-        if context and _USER_ID_CONTEXT_KEY in context.state:
-            headers["x-user-id"] = context.state[_USER_ID_CONTEXT_KEY]
+        if context:
+            if _USER_ID_CONTEXT_KEY in context.state:
+                headers["x-user-id"] = context.state[_USER_ID_CONTEXT_KEY]
+
+            request_headers = context.state.get(_HEADERS_CONTEXT_KEY, {})
+            if isinstance(request_headers, dict):
+                for key, value in request_headers.items():
+                    if key.lower() == "authorization":
+                        headers = {k: v for k, v in headers.items() if k.lower() != "authorization"}
+                        headers[key] = value
+                        break
         http_kwargs["headers"] = headers
         return request_payload, http_kwargs
 
 
+def _build_subagent_call_context(tool_context: ToolContext) -> ClientCallContext:
+    """Build A2A call context for requests delegated to sub-agents."""
+    ctx_state = {_USER_ID_CONTEXT_KEY: tool_context.session.user_id}
+    session_state = getattr(tool_context.session, "state", {}) or {}
+    session_headers = session_state.get(_HEADERS_CONTEXT_KEY, {}) if isinstance(session_state, dict) else {}
+    if session_headers:
+        ctx_state[_HEADERS_CONTEXT_KEY] = session_headers
+    return ClientCallContext(state=ctx_state)
+
+
 def _extract_text_from_task(task: Task) -> str:
     """Extract text content from a completed task's artifacts or status message."""
     # Prefer artifacts (the canonical result)
@@ -239,7 +263,7 @@ async def _handle_first_call(self, args: dict[str, Any], tool_context: ToolConte
 
         # Forward the authenticated user ID so the subagent session is scoped
         # to the same user as the parent agent session.
-        call_context = ClientCallContext(state={_USER_ID_CONTEXT_KEY: tool_context.session.user_id})
+        call_context = _build_subagent_call_context(tool_context)
 
         task: Optional[Task] = None
         try:
@@ -381,7 +405,7 @@ async def _handle_resume(self, tool_context: ToolContext) -> Any:
         )
 
         client = await self._ensure_client()
-        call_context = ClientCallContext(state={_USER_ID_CONTEXT_KEY: tool_context.session.user_id})
+        call_context = _build_subagent_call_context(tool_context)
         task: Optional[Task] = None
         try:
             async for response in client.send_message(request=decision_message, context=call_context):