Runner.Run does not resume direct WorkflowAgent graph root after RequestInput interrupt with native join

B ----\
       → join → D
C ----/

cd /tmp/adk_root_repro   # module adk-root-repro, requires adk/v2 v2.3.0
GOCACHE=/tmp/digital-garden-gocache \
  go test -run TestRunnerResumeDoesNotResumeGraphRoot -count=1 -v

package repro

import (
	"context"
	"iter"
	"testing"

	"google.golang.org/adk/v2/agent"
	"google.golang.org/adk/v2/agent/workflowagent"
	"google.golang.org/adk/v2/model"
	"google.golang.org/adk/v2/runner"
	"google.golang.org/adk/v2/session"
	"google.golang.org/adk/v2/workflow"
	"google.golang.org/genai"
)

func scripted(name, output string, interrupt bool) agent.Agent {
	a, err := agent.New(agent.Config{Name: name, Run: func(ctx agent.InvocationContext) iter.Seq2[*session.Event, error] {
		return func(yield func(*session.Event, error) bool) {
			if interrupt {
				if _, ok := workflow.ResumeOrRequestInput(agent.Promote(ctx), func(ev *session.Event) error { yield(ev, nil); return nil }, session.RequestInput{InterruptID: name, Message: "approve"}); ok != nil {
					return
				}
				yield(&session.Event{LLMResponse: model.LLMResponse{Content: genai.NewContentFromText(output, genai.RoleModel)}}, nil)
				return
			}
			ev := session.NewEvent(ctx, ctx.InvocationID())
			ev.Content = genai.NewContentFromText(output, genai.RoleModel)
			yield(ev, nil)
		}
	}})
	if err != nil {
		panic(err)
	}
	return a
}

func TestRunnerResumeDoesNotResumeGraphRoot(t *testing.T) {
	b := scripted("b", "B", true)
	c := scripted("c", "C", false)
	d := scripted("d", "D", false)
	bNode, _ := workflow.NewAgentNode(b, workflow.NodeConfig{})
	cNode, _ := workflow.NewAgentNode(c, workflow.NodeConfig{})
	dNode, _ := workflow.NewAgentNode(d, workflow.NodeConfig{})
	join := workflow.NewJoinNode("join")
	root, err := workflowagent.New(workflowagent.Config{Name: "root", SubAgents: []agent.Agent{b, c, d}, Edges: []workflow.Edge{
		{From: workflow.Start, To: bNode}, {From: workflow.Start, To: cNode},
		{From: bNode, To: join}, {From: cNode, To: join}, {From: join, To: dNode},
	}})
	if err != nil {
		t.Fatal(err)
	}
	svc := session.InMemoryService()
	r, err := runner.New(runner.Config{AppName: "repro", Agent: root, SessionService: svc, AutoCreateSession: true})
	if err != nil {
		t.Fatal(err)
	}
	ctx := context.Background()
	for ev, err := range r.Run(ctx, "u", "s", genai.NewContentFromText("start", genai.RoleUser), agent.RunConfig{}) {
		if err != nil {
			t.Fatal(err)
		}
	}
	msg := genai.NewContentFromFunctionResponse(workflow.WorkflowInputFunctionCallName, map[string]any{"response": "approved"}, genai.RoleUser)
	var sawD bool
	for ev, err := range r.Run(ctx, "u", "s", msg, agent.RunConfig{}) {
		if err != nil {
			t.Fatal(err)
		}
		if ev.Author == "d" {
			sawD = true
		}
	}
	if !sawD {
		t.Fatal("D never executed; workflow root was not resumed after RequestInput")
	}
}

before resume author=c ... waiting=<nil>
before resume author=b ... waiting=&{b approve <nil> <nil>}
after resume  author=c ... waiting=<nil>
after resume  author=b ... waiting=&{b approve <nil> <nil>}   # still waiting; nothing resolved

    A
   / \
  B   C