fix(adk): bridge workflow input through native HITL

go/adk/pkg/a2a/executor.go

@@ -344,7 +344,12 @@ func (e *KAgentExecutor) Execute(ctx context.Context, reqCtx *a2asrv.ExecutorCon
 			// If the event is a task status update event and the status is input required, build the HITL status message
 			if update, ok := event.(*a2atype.TaskStatusUpdateEvent); ok &&
 				update.Status.State == a2atype.TaskStateInputRequired && update.Status.Message != nil {
-				update.Status.Message = BuildHITLStatusMessage(update.Status.Message, hitlActivated)
+				public, buildErr := BuildHITLStatusMessage(update.Status.Message, hitlActivated)
+				if buildErr != nil {
+					yield(nil, fmt.Errorf("failed to build HITL status message: %w", buildErr))
+					return
+				}
+				update.Status.Message = public
 				update.Status.Message.TaskID = update.TaskID
 				update.Status.Message.ContextID = update.ContextID
 			}

go/adk/pkg/a2a/hitl.go

@@ -460,10 +460,13 @@ func hitlStatusText(tools []apia2a.HITLTool, hints []string) string {
 	return genericHITLText
 }
 
-// BuildHITLStatusMessage: ADK confirmation DataParts → public HITL Message extension.
-func BuildHITLStatusMessage(message *a2atype.Message, activated bool) *a2atype.Message {
+// BuildHITLStatusMessage maps ADK pause DataParts to the public HITL Message extension.
+func BuildHITLStatusMessage(message *a2atype.Message, activated bool) (*a2atype.Message, error) {
 	if message == nil {
-		return nil
+		return nil, nil
+	}
+	if public, err := buildWorkflowInputStatus(message, activated); public != nil || err != nil {
+		return public, err
 	}
 	var tools []apia2a.HITLTool
 	var remote *RemoteHitlState
@@ -488,7 +491,7 @@ func BuildHITLStatusMessage(message *a2atype.Message, activated bool) *a2atype.M
 		}
 	}
 	if len(tools) == 0 {
-		return message
+		return message, nil
 	}
 
 	// The text part carries the same information as the typed payload, so a client
@@ -498,7 +501,7 @@ func BuildHITLStatusMessage(message *a2atype.Message, activated bool) *a2atype.M
 	public := a2atype.NewMessage(a2atype.MessageRoleAgent, a2atype.NewTextPart(text))
 	public.TaskID, public.ContextID = message.TaskID, message.ContextID
 	if !activated {
-		return public
+		return public, nil
 	}
 
 	var nested *apia2a.NestedHITLRequest
@@ -515,7 +518,7 @@ func BuildHITLStatusMessage(message *a2atype.Message, activated bool) *a2atype.M
 		return AttachHitlExtension(public, &apia2a.AskUserRequest{
 			Type: HITLTypeAskUserRequest, ID: tools[0].ID,
 			Questions: remote.AskUserRequest.Questions, Nested: nested,
-		})
+		}), nil
 	}
 	// An ask_user call with no answerable question becomes an approval: an empty
 	// question list gives a request that no response can satisfy, because resume
@@ -524,11 +527,11 @@ func BuildHITLStatusMessage(message *a2atype.Message, activated bool) *a2atype.M
 		return AttachHitlExtension(public, &apia2a.AskUserRequest{
 			Type: HITLTypeAskUserRequest, ID: tools[0].ID,
 			Questions: questions,
-		})
+		}), nil
 	}
 	return AttachHitlExtension(public, &apia2a.ToolApprovalRequest{
 		Type: HITLTypeToolApprovalRequest, Hint: text, Tools: tools, Nested: nested,
-	})
+	}), nil
 }
 
 func publicAskUserQuestions(value any) []apia2a.HITLQuestion {
@@ -587,6 +590,8 @@ func BuildResumeHITLMessage(storedTask *a2atype.Task, incoming *a2atype.Message)
 	var parts []*a2atype.Part
 	var err error
 	switch {
+	case askReq != nil && isWorkflowInput(storedTask.Status.Message, askReq.ID):
+		parts, err = workflowInputResponse(askReq, incoming)
 	case askReq != nil && askReq.Nested != nil:
 		parts, err = processNestedAskUser(askReq, incoming)
 	case approvalReq != nil && approvalReq.Nested != nil:

go/adk/pkg/a2a/hitl_test.go

@@ -138,7 +138,7 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 	t.Run("tool approval", func(t *testing.T) {
 		internal := a2atype.NewMessage(a2atype.MessageRoleAgent,
 			confirmationPart("confirm-1", "delete_file", "call-1", map[string]any{"path": "/tmp/x"}, nil))
-		payload := GetToolApprovalRequest(BuildHITLStatusMessage(internal, true))
+		payload := GetToolApprovalRequest(mustBuildHITLStatusMessage(t, internal, true))
 		if payload == nil || payload.Tools[0].ID != "confirm-1" {
 			t.Fatalf("payload = %#v", payload)
 		}
@@ -150,7 +150,7 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 		}}
 		internal := a2atype.NewMessage(a2atype.MessageRoleAgent,
 			confirmationPart("confirm-2", "ask_user", "call-2", map[string]any{"questions": questions}, nil))
-		payload := GetAskUserRequest(BuildHITLStatusMessage(internal, true))
+		payload := GetAskUserRequest(mustBuildHITLStatusMessage(t, internal, true))
 		if payload == nil || len(payload.Questions) != 1 || payload.Questions[0].Question != "Which databases?" ||
 			!slices.Equal(payload.Questions[0].Choices, []string{"PostgreSQL", "MySQL"}) || !payload.Questions[0].Multiple {
 			t.Fatalf("payload = %#v", payload)
@@ -160,7 +160,7 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 	t.Run("ask user without questions asks for approval", func(t *testing.T) {
 		internal := a2atype.NewMessage(a2atype.MessageRoleAgent,
 			hintlessConfirmationPart("confirm-2", "ask_user", "call-2"))
-		public := BuildHITLStatusMessage(internal, true)
+		public := mustBuildHITLStatusMessage(t, internal, true)
 		if GetAskUserRequest(public) != nil {
 			t.Fatal("an ask_user call without questions must not become an ask_user request")
 		}
@@ -177,7 +177,7 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 		questions := []any{map[string]any{"question": ""}, map[string]any{"question": "Which cluster?"}}
 		internal := a2atype.NewMessage(a2atype.MessageRoleAgent,
 			confirmationPart("confirm-2", "ask_user", "call-2", map[string]any{"questions": questions}, nil))
-		public := BuildHITLStatusMessage(internal, true)
+		public := mustBuildHITLStatusMessage(t, internal, true)
 		payload := GetAskUserRequest(public)
 		if payload == nil || len(payload.Questions) != 1 || payload.Questions[0].Question != "Which cluster?" {
 			t.Fatalf("payload = %#v", payload)
@@ -198,7 +198,7 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 				}},
 			},
 		}
-		payload := GetToolApprovalRequest(BuildHITLStatusMessage(
+		payload := GetToolApprovalRequest(mustBuildHITLStatusMessage(t,
 			a2atype.NewMessage(a2atype.MessageRoleAgent,
 				confirmationPart("parent-confirm", "k8s_agent", "parent-call", nil, remote.ToMap())),
 			true,
@@ -209,7 +209,7 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 	})
 
 	t.Run("not activated", func(t *testing.T) {
-		public := BuildHITLStatusMessage(a2atype.NewMessage(a2atype.MessageRoleAgent,
+		public := mustBuildHITLStatusMessage(t, a2atype.NewMessage(a2atype.MessageRoleAgent,
 			confirmationPart("confirm-1", "delete_file", "call-1", nil, nil)), false)
 		if GetToolApprovalRequest(public) != nil {
 			t.Fatalf("unexpected payload on inactive client")
@@ -220,7 +220,7 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 	})
 
 	t.Run("not activated without a tool hint names the tool", func(t *testing.T) {
-		public := BuildHITLStatusMessage(a2atype.NewMessage(a2atype.MessageRoleAgent,
+		public := mustBuildHITLStatusMessage(t, a2atype.NewMessage(a2atype.MessageRoleAgent,
 			hintlessConfirmationPart("confirm-1", "delete_file", "call-1")), false)
 		if want := "Approval is required for tool(s): delete_file"; messageText(public) != want {
 			t.Errorf("text = %q, want %q", messageText(public), want)
@@ -232,7 +232,7 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 			confirmationPart("confirm-1", "delete_file", "call-1", nil, nil),
 			hintlessConfirmationPart("confirm-2", "restart_pod", "call-2"))
 		want := "Please confirm (delete_file, restart_pod)"
-		if text := messageText(BuildHITLStatusMessage(internal, false)); text != want {
+		if text := messageText(mustBuildHITLStatusMessage(t, internal, false)); text != want {
 			t.Errorf("text = %q, want %q", text, want)
 		}
 	})
@@ -242,13 +242,13 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 			hintedConfirmationPart("confirm-1", "delete_file", "call-1", "First hint"),
 			hintedConfirmationPart("confirm-2", "restart_pod", "call-2", "Second hint"))
 		want := "First hint; Second hint (delete_file, restart_pod)"
-		if text := messageText(BuildHITLStatusMessage(internal, false)); text != want {
+		if text := messageText(mustBuildHITLStatusMessage(t, internal, false)); text != want {
 			t.Errorf("text = %q, want %q", text, want)
 		}
 	})
 
 	t.Run("activated payload hint repeats the text", func(t *testing.T) {
-		public := BuildHITLStatusMessage(a2atype.NewMessage(a2atype.MessageRoleAgent,
+		public := mustBuildHITLStatusMessage(t, a2atype.NewMessage(a2atype.MessageRoleAgent,
 			hintlessConfirmationPart("confirm-1", "delete_file", "call-1")), true)
 		payload := GetToolApprovalRequest(public)
 		if payload == nil {
@@ -263,7 +263,7 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 		questions := []any{map[string]any{"question": "Which database?"}}
 		internal := a2atype.NewMessage(a2atype.MessageRoleAgent,
 			askUserConfirmationPart("confirm-2", "call-2", questions, "Which database?"))
-		public := BuildHITLStatusMessage(internal, false)
+		public := mustBuildHITLStatusMessage(t, internal, false)
 		if GetAskUserRequest(public) != nil {
 			t.Fatal("unexpected payload on inactive client")
 		}
@@ -273,7 +273,7 @@ func TestBuildHITLStatusMessage(t *testing.T) {
 	})
 
 	t.Run("non-confirmation long-running call", func(t *testing.T) {
-		public := BuildHITLStatusMessage(a2atype.NewMessage(a2atype.MessageRoleAgent,
+		public := mustBuildHITLStatusMessage(t, a2atype.NewMessage(a2atype.MessageRoleAgent,
 			dataPart(map[string]any{"name": "auth_required"}, map[string]any{
 				"adk_type": "function_call", "adk_is_long_running": true,
 			})), true)
@@ -469,3 +469,12 @@ func TestBuildRemoteHitlStateAndHintAskUserNested(t *testing.T) {
 		t.Fatalf("hint = %q, want %q", got, want)
 	}
 }
+
+func mustBuildHITLStatusMessage(t *testing.T, message *a2atype.Message, activated bool) *a2atype.Message {
+	t.Helper()
+	public, err := BuildHITLStatusMessage(message, activated)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return public
+}

go/adk/pkg/a2a/workflow_input.go

@@ -0,0 +1,75 @@
+package a2a
+
+import (
+	"fmt"
+
+	a2atype "github.com/a2aproject/a2a-go/v2/a2a"
+	"google.golang.org/adk/v2/server/adka2a/v2"
+	"google.golang.org/adk/v2/workflow"
+
+	apia2a "github.com/kagent-dev/kagent/go/api/a2a"
+)
+
+// Keep the canonical call so resume reaches the workflow input dispatcher.
+func buildWorkflowInputStatus(message *a2atype.Message, activated bool) (*a2atype.Message, error) {
+	var public *a2atype.Message
+	var pending int
+	for _, part := range message.Parts {
+		data := asDataPart(part)
+		if data == nil ||
+			part.Metadata[adka2a.ToA2AMetaKey(A2ADataPartMetadataTypeKey)] != A2ADataPartMetadataTypeFunctionCall ||
+			part.Metadata[adka2a.ToA2AMetaKey(A2ADataPartMetadataIsLongRunningKey)] != true {
+			continue
+		}
+		pending++
+		if data["name"] != workflow.WorkflowInputFunctionCallName {
+			continue
+		}
+		if public != nil {
+			return nil, fmt.Errorf("workflow pause requires exactly one input request")
+		}
+		converted, err := adka2a.ToGenAIPart(part)
+		if err != nil {
+			return nil, fmt.Errorf("failed to decode workflow input request: %w", err)
+		}
+		if converted == nil || converted.FunctionCall == nil || converted.FunctionCall.ID == "" {
+			return nil, fmt.Errorf("workflow input request requires a correlation id")
+		}
+		call := converted.FunctionCall
+		text, _ := call.Args["message"].(string)
+		if text == "" {
+			text = "Provide input to continue the workflow."
+		}
+		public = a2atype.NewMessage(a2atype.MessageRoleAgent, a2atype.NewTextPart(text), apia2a.NewToolCallPart(call.ID, call.Name, call.Args))
+		public.TaskID, public.ContextID = message.TaskID, message.ContextID
+		if activated {
+			AttachHitlExtension(public, &apia2a.AskUserRequest{
+				Type: HITLTypeAskUserRequest, ID: call.ID,
+				Questions: []apia2a.HITLQuestion{{Question: text}},
+			})
+		}
+	}
+	if public != nil && pending != 1 {
+		return nil, fmt.Errorf("workflow pause requires exactly one input request")
+	}
+	return public, nil
+}
+
+func isWorkflowInput(message *a2atype.Message, id string) bool {
+	for _, part := range message.Parts {
+		call, ok := apia2a.ParseToolActivity(part)
+		if ok && call.Kind == apia2a.ToolCallKind && call.Name == workflow.WorkflowInputFunctionCallName && call.ID == id {
+			return true
+		}
+	}
+	return false
+}
+
+func workflowInputResponse(request *apia2a.AskUserRequest, message *a2atype.Message) ([]*a2atype.Part, error) {
+	response := GetAskUserResponse(message)
+	if response == nil || response.ID != request.ID || len(response.Answers) != 1 || len(response.Answers[0].Answer) != 1 {
+		return nil, fmt.Errorf("workflow input response requires one correlated answer")
+	}
+	return []*a2atype.Part{apia2a.NewToolResultPart(request.ID, workflow.WorkflowInputFunctionCallName,
+		map[string]any{"response": response.Answers[0].Answer[0]})}, nil
+}