diff --git a/internal/ai/runtime/executor/answerability_gate.go b/internal/ai/runtime/executor/answerability_gate.go
new file mode 100644
index 0000000..4b70936
--- /dev/null
+++ b/internal/ai/runtime/executor/answerability_gate.go
@@ -0,0 +1,78 @@
+package executor
+
+import (
+	"context"
+	"time"
+
+	"cs-agent/internal/ai/runtime/internal/impl/callbacks"
+	"cs-agent/internal/ai/runtime/internal/impl/factory"
+	"cs-agent/internal/ai/runtime/internal/impl/retrievers"
+	"cs-agent/internal/models"
+
+	"github.com/cloudwego/eino/components/model"
+	"github.com/cloudwego/eino/schema"
+)
+
+const (
+	answerabilityNodeRetrieve = "retrieve_knowledge"
+	answerabilityNodeGrade    = "grade_answerability"
+	answerabilityNodeAllow    = "allow_agent"
+	answerabilityNodeFallback = "fallback"
+
+	answerabilityStatusSkipped      = "skipped"
+	answerabilityStatusAnswerable   = "answerable"
+	answerabilityStatusUnanswerable = "unanswerable"
+)
+
+type knowledgeContextRetriever interface {
+	KnowledgeBaseIDs() []int64
+	RetrieveContextByOptions(ctx context.Context, opts retrievers.KnowledgeRetrieveOptions, query string) (*retrievers.KnowledgeRetrieveResult, error)
+}
+
+type answerabilityRetrieverFactory func(aiAgent models.AIAgent) knowledgeContextRetriever
+
+type answerabilityChatModelFactory func(ctx context.Context, aiConfig models.AIConfig) (model.BaseChatModel, error)
+
+type KnowledgeAnswerabilityGate struct {
+	newRetriever answerabilityRetrieverFactory
+	newChatModel answerabilityChatModelFactory
+	now          func() time.Time
+}
+
+type answerabilityGateInput struct {
+	Request   RunInput
+	Summary   *RunResult
+	Collector *callbacks.RuntimeTraceCollector
+	Messages  []*schema.Message
+}
+
+type answerabilityGateState struct {
+	Input          answerabilityGateInput
+	KnowledgeIDs   []int64
+	RetrieveResult *retrievers.KnowledgeRetrieveResult
+	Decision       knowledgeGuardDecision
+	Grade          answerabilityDecision
+	SkipGate       bool
+	FallbackReply  string
+	ErrorMessage   string
+}
+
+type answerabilityDecision struct {
+	Answerable         bool     `json:"answerable"`
+	Reason             string   `json:"reason"`
+	SupportingChunkIDs []string `json:"supportingChunkIds"`
+	MissingInfo        []string `json:"missingInfo"`
+}
+
+func NewKnowledgeAnswerabilityGate() *KnowledgeAnswerabilityGate {
+	chatModelFactory := factory.NewChatModelFactory()
+	return &KnowledgeAnswerabilityGate{
+		newRetriever: func(aiAgent models.AIAgent) knowledgeContextRetriever {
+			return retrievers.NewKnowledgeRetriever(aiAgent)
+		},
+		newChatModel: func(ctx context.Context, aiConfig models.AIConfig) (model.BaseChatModel, error) {
+			return chatModelFactory.Build(ctx, aiConfig)
+		},
+		now: time.Now,
+	}
+}
diff --git a/internal/ai/runtime/executor/knowledge_guard.go b/internal/ai/runtime/executor/knowledge_guard.go
index 34eca15..9c83de7 100644
--- a/internal/ai/runtime/executor/knowledge_guard.go
+++ b/internal/ai/runtime/executor/knowledge_guard.go
@@ -51,6 +51,18 @@ func resolveKnowledgeFallbackReply(aiAgent models.AIAgent) string {
 	}
 }
 
+func resolveKnowledgeHumanSupportFallback(aiAgent models.AIAgent) string {
+	base := strings.TrimSpace(resolveKnowledgeFallbackReply(aiAgent))
+	if base == "" {
+		base = "当前知识库暂无明确信息。"
+	}
+	suggestion := "建议你联系人工客服进一步确认。"
+	if strings.Contains(base, suggestion) {
+		return base
+	}
+	return strings.TrimSpace(base + " " + suggestion)
+}
+
 func buildKnowledgeRuntimeInstruction(answerMode enums.KnowledgeAnswerMode, fallbackReply string) string {
 	fallbackReply = strings.TrimSpace(fallbackReply)
 	if fallbackReply == "" {
diff --git a/internal/ai/runtime/executor/knowledge_guard_test.go b/internal/ai/runtime/executor/knowledge_guard_test.go
index 6446aca..0717755 100644
--- a/internal/ai/runtime/executor/knowledge_guard_test.go
+++ b/internal/ai/runtime/executor/knowledge_guard_test.go
@@ -100,6 +100,29 @@ func TestBuildKnowledgeUnavailableDecisionSkipsWhenAgentHasNoKnowledge(t *testin
 	}
 }
 
+func TestResolveKnowledgeHumanSupportFallbackUsesAgentMessage(t *testing.T) {
+	agent := newKnowledgeGuardAgentFixture()
+	agent.FallbackMessage = "我暂时没有找到足够准确的信息。"
+
+	got := resolveKnowledgeHumanSupportFallback(agent)
+
+	want := "我暂时没有找到足够准确的信息。 建议你联系人工客服进一步确认。"
+	if got != want {
+		t.Fatalf("unexpected fallback: %q", got)
+	}
+}
+
+func TestResolveKnowledgeHumanSupportFallbackUsesDefault(t *testing.T) {
+	agent := newKnowledgeGuardAgentFixture()
+
+	got := resolveKnowledgeHumanSupportFallback(agent)
+
+	want := "当前知识库暂无明确信息。 建议你联系人工客服进一步确认。"
+	if got != want {
+		t.Fatalf("unexpected fallback: %q", got)
+	}
+}
+
 func newKnowledgeGuardAgentFixture() models.AIAgent {
 	return models.AIAgent{
 		FallbackMode: enums.AIAgentFallbackModeNoAnswer,