diff --git a/internal/app/app.go b/internal/app/app.go
index df553d4..175ae5c 100644
--- a/internal/app/app.go
+++ b/internal/app/app.go
@@ -299,11 +299,7 @@ func Run(opt Options) error {
 	// 未配置时调用返回明确的「未配置」提示，不静默降级为空结果。
 	if err := tools.RegisterLazySearchTools(reg, func() agenttools.SearchProvider {
 		effNow := setSvc.Effective(store.OwnerDefault, "")
-		tavilyNow := effNow.GetString("tools.tavily.apiKeys", "")
-		if active, ok := st.ActiveSecret(store.OwnerDefault, "tools.tavily"); ok {
-			tavilyNow = active
-		}
-		keys := splitKeyPool(tavilyNow)
+		keys := tavilyKeyPool(st, effNow.GetString("tools.tavily.apiKeys", ""))
 		if len(keys) == 0 {
 			return nil
 		}
@@ -369,11 +365,7 @@ func Run(opt Options) error {
 			},
 		}
 		cfg.Stream = runtime.GuardProjectStream(rc, "", cfg.Client.Stream)
-		tavilyNow := effNow.GetString("tools.tavily.apiKeys", "")
-		if active, ok := st.ActiveSecret(store.OwnerDefault, "tools.tavily"); ok {
-			tavilyNow = active
-		}
-		if keys := splitKeyPool(tavilyNow); len(keys) > 0 {
+		if keys := tavilyKeyPool(st, effNow.GetString("tools.tavily.apiKeys", "")); len(keys) > 0 {
 			cfg.Search = agenttools.NewTavilyProvider(effNow.GetString("tools.tavily.endpoint", ""), keys)
 		}
 		if effNow.GetBool("runtime.exec", true) {
diff --git a/internal/app/regulations_tools.go b/internal/app/regulations_tools.go
index 731bcd2..89d2766 100644
--- a/internal/app/regulations_tools.go
+++ b/internal/app/regulations_tools.go
@@ -25,9 +25,60 @@ const (
 
 	toolRegulationsSearch  = "regulations_search"
 	toolRegulationEvidence = "regulation_evidence"
+	toolKnowledgeSearch    = "knowledge_search"
+
+	knowledgeRegulationsFallbackPrefix = "项目资料无命中；以下为法规知识库命中（可用 regulation_evidence 取原文）：\n"
 )
 
 func registerRegulationsTools(reg *tools.Registry, caps hostcaps) error {
+	if err := registerRegulationsSearchTools(reg, caps); err != nil {
+		return err
+	}
+	return wrapKnowledgeSearchWithRegulations(reg, caps)
+}
+
+// wrapKnowledgeSearchWithRegulations 让 knowledge_search 在项目资料无命中时回退
+// 法规知识库；未注册 knowledge_search 时不做任何事。
+func wrapKnowledgeSearchWithRegulations(reg *tools.Registry, caps hostcaps) error {
+	desc, inner, ok := reg.Get(toolKnowledgeSearch)
+	if !ok {
+		return nil
+	}
+	return reg.Register(desc, func(rc tools.ToolExecCtx, args json.RawMessage) (string, error) {
+		out, err := inner(rc, args)
+		if err != nil || out != tools.KnowledgeSearchNoHits {
+			return out, err
+		}
+		if fallback, ok := knowledgeRegulationsFallback(caps, rc, args); ok {
+			return knowledgeRegulationsFallbackPrefix + fallback, nil
+		}
+		return out, nil
+	})
+}
+
+func knowledgeRegulationsFallback(caps hostcaps, rc tools.ToolExecCtx, args json.RawMessage) (string, bool) {
+	var a struct {
+		Query string `json:"query"`
+	}
+	if json.Unmarshal(args, &a) != nil {
+		return "", false
+	}
+	q, err := json.Marshal(map[string]string{"query": a.Query})
+	if err != nil {
+		return "", false
+	}
+	res, err := regulationsSearchTool(caps, rc, q)
+	if err != nil {
+		return "", false
+	}
+	var parsed regulationsToolSearchOutput
+	if json.Unmarshal([]byte(res), &parsed) != nil || parsed.State == extension.RegulationsStateUnavailable || len(parsed.Hits) == 0 {
+		return "", false
+	}
+	return res, true
+}
+
+func registerRegulationsSearchTools(reg *tools.Registry, caps hostcaps) error {
 	if err := reg.Register(core.ToolDesc{
 		Name:        toolRegulationsSearch,
 		Description: "检索已发布的医疗器械法规、标准（GB/YY/YY/T 等）、指导原则、通告等共享法规知识库；用户提到标准号、法规名称、条款或监管要求时优先调用本工具，再考虑网络搜索；命中后可用 regulation_evidence 取条款原文以精确引用",
diff --git a/internal/app/regulations_tools_test.go b/internal/app/regulations_tools_test.go
index 3f2db92..2c1471d 100644
--- a/internal/app/regulations_tools_test.go
+++ b/internal/app/regulations_tools_test.go
@@ -224,3 +224,95 @@ func TestRegulationsToolsReportUnavailable(t *testing.T) {
 		t.Fatalf("provider failure reported as success: %+v", res)
 	}
 }
+
+type knowledgeHitsCtx struct {
+	regulationsToolCtx
+	hits []core.RetrievalHit
+}
+
+func (c knowledgeHitsCtx) Retrieve(core.RetrievalQuery) ([]core.RetrievalHit, error) {
+	return c.hits, nil
+}
+
+func newKnowledgeFallbackRegistry(t *testing.T, h inprocHost) *tools.Registry {
+	t.Helper()
+	reg := tools.NewRegistry()
+	if err := reg.RegisterBuiltin(); err != nil {
+		t.Fatal(err)
+	}
+	before, _, _ := reg.Get(toolKnowledgeSearch)
+	if err := registerRegulationsTools(reg, h.caps); err != nil {
+		t.Fatal(err)
+	}
+	if after, _, _ := reg.Get(toolKnowledgeSearch); !reflect.DeepEqual(after, before) {
+		t.Fatalf("knowledge_search desc changed: %+v", after)
+	}
+	return reg
+}
+
+func callKnowledgeSearch(reg *tools.Registry, hits []core.RetrievalHit) core.ToolCallResult {
+	rc := knowledgeHitsCtx{regulationsToolCtx: regulationsToolCtx{owner: "alice"}, hits: hits}
+	return reg.Execute(rc, core.ToolCallRequest{CallID: "c1", Name: toolKnowledgeSearch, Arguments: json.RawMessage(`{"query":"电气安全"}`)})
+}
+
+func TestKnowledgeSearchFallsBackToRegulationsHits(t *testing.T) {
+	h, _ := newRegulationsTestHost(t)
+	p := registerRecordingRegulations(t, h)
+	p.search = extension.RegulationsSearchResult{CorpusRevision: "rev-9", State: extension.RegulationsStateOK,
+		Hits: []extension.RegulationHit{{RegulationID: "r1", EditionID: "e1", NodeID: "n1", DocNo: "GB 9706.1-2020",
+			Excerpt: "法规条款片段", Disclosure: extension.RegulationDisclosureFull}}}
+	reg := newKnowledgeFallbackRegistry(t, h)
+	res := callKnowledgeSearch(reg, nil)
+	if res.Status != "ok" || !strings.HasPrefix(res.Output, knowledgeRegulationsFallbackPrefix) ||
+		!strings.Contains(res.Output, "法规条款片段") || !strings.Contains(res.Output, "GB 9706.1-2020") {
+		t.Fatalf("fallback result = %+v", res)
+	}
+	if len(p.searches) != 1 || p.searches[0].Query != "电气安全" {
+		t.Fatalf("regulations request = %+v", p.searches)
+	}
+}
+
+func TestKnowledgeSearchKeepsNoHitsWhenRegulationsEmpty(t *testing.T) {
+	h, _ := newRegulationsTestHost(t)
+	p := registerRecordingRegulations(t, h)
+	p.search = extension.RegulationsSearchResult{CorpusRevision: "rev-9", State: extension.RegulationsStateOK}
+	reg := newKnowledgeFallbackRegistry(t, h)
+	if res := callKnowledgeSearch(reg, nil); res.Status != "ok" || res.Output != tools.KnowledgeSearchNoHits {
+		t.Fatalf("empty regulations result = %+v", res)
+	}
+	if len(p.searches) != 1 {
+		t.Fatalf("regulations not consulted: %+v", p.searches)
+	}
+}
+
+func TestKnowledgeSearchKeepsNoHitsWhenRegulationsUnavailable(t *testing.T) {
+	h, _ := newRegulationsTestHost(t)
+	reg := newKnowledgeFallbackRegistry(t, h)
+	if res := callKnowledgeSearch(reg, nil); res.Status != "ok" || res.Output != tools.KnowledgeSearchNoHits {
+		t.Fatalf("no provider result = %+v", res)
+	}
+	p := registerRecordingRegulations(t, h)
+	for _, err := range []error{extension.ErrRegulationsUnavailable, errors.New("provider failure")} {
+		p.err = err
+		if res := callKnowledgeSearch(reg, nil); res.Status != "ok" || res.Output != tools.KnowledgeSearchNoHits {
+			t.Fatalf("provider %v result = %+v", err, res)
+		}
+	}
+}
+
+func TestKnowledgeSearchProjectHitSkipsRegulations(t *testing.T) {
+	h, _ := newRegulationsTestHost(t)
+	p := registerRecordingRegulations(t, h)
+	p.search = extension.RegulationsSearchResult{CorpusRevision: "rev-9", State: extension.RegulationsStateOK,
+		Hits: []extension.RegulationHit{{RegulationID: "r1", EditionID: "e1", NodeID: "n1", Excerpt: "法规条款片段"}}}
+	reg := newKnowledgeFallbackRegistry(t, h)
+	hits := []core.RetrievalHit{{Doc: core.KnowledgeDoc{Title: "项目说明书", Source: "upload", Chunk: "项目片段"}, Score: 0.8}}
+	res := callKnowledgeSearch(reg, hits)
+	if res.Status != "ok" || !strings.Contains(res.Output, "项目片段") ||
+		strings.Contains(res.Output, knowledgeRegulationsFallbackPrefix) || strings.Contains(res.Output, "法规条款片段") {
+		t.Fatalf("project hit result = %+v", res)
+	}
+	if len(p.searches) != 0 {
+		t.Fatalf("regulations consulted on project hit: %+v", p.searches)
+	}
+}
diff --git a/internal/app/tavily_keys.go b/internal/app/tavily_keys.go
new file mode 100644
index 0000000..8a76067
--- /dev/null
+++ b/internal/app/tavily_keys.go
@@ -0,0 +1,23 @@
+package app
+
+import (
+	"agent-system-backend/internal/settings"
+	"agent-system-backend/internal/store"
+)
+
+const tavilySecretService = "tools.tavily"
+
+type activeSecretSource interface {
+	ActiveSecret(owner, service string) (string, bool)
+}
+
+// tavilyKeyPool 解析 Tavily 密钥池：默认属主受管密钥 → 系统行受管密钥
+// （owner=settings.OwnerSystemRow）→ 设置明文 tools.tavily.apiKeys。
+func tavilyKeyPool(secrets activeSecretSource, plaintext string) []string {
+	for _, owner := range []string{store.OwnerDefault, settings.OwnerSystemRow} {
+		if active, ok := secrets.ActiveSecret(owner, tavilySecretService); ok {
+			return splitKeyPool(active)
+		}
+	}
+	return splitKeyPool(plaintext)
+}
diff --git a/internal/app/tavily_keys_test.go b/internal/app/tavily_keys_test.go
new file mode 100644
index 0000000..0618c99
--- /dev/null
+++ b/internal/app/tavily_keys_test.go
@@ -0,0 +1,53 @@
+package app
+
+import (
+	"path/filepath"
+	"reflect"
+	"testing"
+
+	"agent-system-backend/internal/settings"
+	"agent-system-backend/internal/store"
+)
+
+func newTavilyKeysStore(t *testing.T) *store.Store {
+	t.Helper()
+	st, err := store.OpenSQLite(filepath.Join(t.TempDir(), "tavily.db"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { st.Close() })
+	return st
+}
+
+func TestTavilyKeyPoolFallsBackToSystemRowSecret(t *testing.T) {
+	st := newTavilyKeysStore(t)
+	if _, err := st.AddSecret(settings.OwnerSystemRow, tavilySecretService, "system", "fake-sys-a, fake-sys-b"); err != nil {
+		t.Fatal(err)
+	}
+	if got, want := tavilyKeyPool(st, "fake-plain"), []string{"fake-sys-a", "fake-sys-b"}; !reflect.DeepEqual(got, want) {
+		t.Fatalf("system-row key pool = %v, want %v", got, want)
+	}
+}
+
+func TestTavilyKeyPoolPrefersOwnerRowSecret(t *testing.T) {
+	st := newTavilyKeysStore(t)
+	if _, err := st.AddSecret(settings.OwnerSystemRow, tavilySecretService, "system", "fake-sys"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := st.AddSecret(store.OwnerDefault, tavilySecretService, "owner", "fake-owner"); err != nil {
+		t.Fatal(err)
+	}
+	if got, want := tavilyKeyPool(st, "fake-plain"), []string{"fake-owner"}; !reflect.DeepEqual(got, want) {
+		t.Fatalf("owner-row key pool = %v, want %v", got, want)
+	}
+}
+
+func TestTavilyKeyPoolFallsBackToPlaintextSetting(t *testing.T) {
+	st := newTavilyKeysStore(t)
+	if got, want := tavilyKeyPool(st, " fake-plain-a ,, fake-plain-b"), []string{"fake-plain-a", "fake-plain-b"}; !reflect.DeepEqual(got, want) {
+		t.Fatalf("plaintext key pool = %v, want %v", got, want)
+	}
+	if got := tavilyKeyPool(st, ""); len(got) != 0 {
+		t.Fatalf("empty key pool = %v", got)
+	}
+}
diff --git a/internal/prompts/library/base-tools.md b/internal/prompts/library/base-tools.md
index 724f889..5a03fea 100644
--- a/internal/prompts/library/base-tools.md
+++ b/internal/prompts/library/base-tools.md
@@ -7,7 +7,7 @@ description: 何时用工具、如何并行调用、如何处理工具结果
 ---
 使用工具时遵循：
 
-- 优先专用工具而非通用手段：读文件用 read_file（行号分页）、找内容用 grep、找文件用 glob、改文件用 edit_file/multi_edit（须先读过、old_string 唯一）；会话工作区内的文件操作一律用这些工具，不用 run_shell 的 cat/sed 代替。检索知识用检索工具、查时间用时间工具；能用结构化工具完成的，不绕道自由文本。
+- 优先专用工具而非通用手段：读文件用 read_file（行号分页）、找内容用 grep、找文件用 glob、改文件用 edit_file/multi_edit（须先读过、old_string 唯一）；会话工作区内的文件操作一律用这些工具，不用 run_shell 的 cat/sed 代替。检索项目资料用 knowledge_search；法规、标准、标准号（GB、YY、YY/T、IEC 等）、指导原则类问题优先用 regulations_search，需条款原文再用 regulation_evidence；查时间用时间工具；能用结构化工具完成的，不绕道自由文本。
 - 相互独立的调用并行发起；有依赖的调用按依赖顺序串行。
 - 调用前确认参数完整、类型正确；不确定参数含义时先查阅工具描述，不猜测字段。
 - 工具结果是事实来源：基于结果作答并如实转述；结果为空或报错时说明情况，不假装拿到了数据。
diff --git a/internal/prompts/library/tool-knowledge-search.md b/internal/prompts/library/tool-knowledge-search.md
index 61e1c34..4e859cc 100644
--- a/internal/prompts/library/tool-knowledge-search.md
+++ b/internal/prompts/library/tool-knowledge-search.md
@@ -5,4 +5,4 @@ version: 1
 title: knowledge_search 工具描述
 description: 知识检索工具的模型侧说明文案
 ---
-在项目知识与插件知识库中做全文检索，返回命中片段。用法：一次一个明确的检索意图；换角度检索时改关键词再查，不重复同一查询。命中为空说明库中没有该表述，可换同义词再试一到两次；仍为空就承认未命中，不虚构结果。回答"项目里有没有/是什么"类问题优先用本工具。
+在项目知识与插件知识库中做全文检索，返回命中片段。用法：一次一个明确的检索意图；换角度检索时改关键词再查，不重复同一查询。命中为空说明库中没有该表述，可换同义词再试一到两次；仍为空就承认未命中，不虚构结果。回答"项目里有没有/是什么"类项目资料问题优先用本工具；法规、标准、标准号（GB、YY、YY/T、IEC 等）或指导原则类问题优先用 regulations_search，再用 regulation_evidence 取条款原文。
diff --git a/internal/tools/registry.go b/internal/tools/registry.go
index 7d9b408..847dd3e 100644
--- a/internal/tools/registry.go
+++ b/internal/tools/registry.go
@@ -13,6 +13,9 @@ import (
 	core "agent-system-core"
 )
 
+// KnowledgeSearchNoHits 是 knowledge_search 项目资料无命中时的输出。
+const KnowledgeSearchNoHits = "（无命中）"
+
 // Executor 是无状态执行器：入参已校验，返回输出文本或错误。
 type Executor func(rc ToolExecCtx, args json.RawMessage) (string, error)
 
@@ -121,7 +124,7 @@ func (r *Registry) RegisterBuiltin() error {
 		return err
 	}
 	if err := r.Register(core.ToolDesc{
-		Name: "knowledge_search", Description: "在项目知识与插件知识库中做全文检索，返回命中片段", Source: core.SourceBuiltin, ReadOnly: true,
+		Name: "knowledge_search", Description: "在项目资料（项目知识与插件知识库）中做全文检索，返回命中片段；法规、标准、标准号（GB/YY/YY/T/IEC 等）或指导原则类问题优先用 regulations_search", Source: core.SourceBuiltin, ReadOnly: true,
 		Parameters: json.RawMessage(`{"type":"object","properties":{"query":{"type":"string","description":"检索词"}},"required":["query"]}`),
 	}, func(rc ToolExecCtx, args json.RawMessage) (string, error) {
 		var a struct {
@@ -141,7 +144,7 @@ func (r *Registry) RegisterBuiltin() error {
 			return "", err
 		}
 		if len(hits) == 0 {
-			return "（无命中）", nil
+			return KnowledgeSearchNoHits, nil
 		}
 		var sb strings.Builder
 		for i, h := range hits {