diff --git a/adapters/native/backend.go b/adapters/native/backend.go
index c26d69e..7a7fcd6 100644
--- a/adapters/native/backend.go
+++ b/adapters/native/backend.go
@@ -19,6 +19,7 @@ import (
 	"agent-native/runtime/promptx"
 	"agent-native/runtime/session"
 	"agent-native/runtime/skills"
+	"agent-native/runtime/subagent"
 	"agent-native/runtime/tools"
 
 	"logging-system/logsys"
@@ -47,6 +48,8 @@ type Options struct {
 	SkillsRoots []string
 	// Compact 可选：转录超过阈值时把头部历史压成摘要（长会话上下文治理）。
 	Compact *CompactConfig
+	// Subagent 可选：提供时注册 delegate_task（委派由宿主实现，内核只开端口）。
+	Subagent subagent.Factory
 	// Log 可选。nil 时丢弃日志。
 	Log *logsys.Logger
 	// ExecutionID 写入日志，不参与执行控制。
@@ -164,6 +167,7 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 				return &exec.Result{Success: false, ErrorReason: err.Error()}, nil
 			}
 		}
+		subagent.Register(reg, b.opts.Subagent)
 		if err := reg.Restrict(req.ToolAllowlist); err != nil {
 			return &exec.Result{Success: false, ErrorReason: err.Error()}, nil
 		}
diff --git a/adapters/native/exec_tools_test.go b/adapters/native/exec_tools_test.go
index 5096e75..865b634 100644
--- a/adapters/native/exec_tools_test.go
+++ b/adapters/native/exec_tools_test.go
@@ -11,6 +11,7 @@ import (
 	"agent-native/exec"
 	"agent-native/runtime/llm"
 	"agent-native/runtime/mcp"
+	"agent-native/runtime/subagent"
 	"agent-native/runtime/tools"
 )
 
@@ -295,3 +296,47 @@ func TestBackendWorkspaceSkillsRootAutoMerged(t *testing.T) {
 		t.Fatalf("workspace skills root must be merged into index:\n%s", c.system)
 	}
 }
+
+func TestBackendSubagentWiredViaOptions(t *testing.T) {
+	var delegated *subagent.Request
+	stream, c := captureStream(
+		llm.Message{Role: llm.RoleAssistant, StopReason: llm.StopToolCalls, ToolCalls: []llm.ToolCall{{
+			ID: "c1", Name: "delegate_task",
+			Arguments: `{"goal":"查证数据","write_scope":"research/","done_criteria":"三来源"}`,
+		}}},
+		llm.Message{Role: llm.RoleAssistant, StopReason: llm.StopToolCalls, ToolCalls: []llm.ToolCall{{
+			ID: "c2", Name: "write_file",
+			Arguments: `{"path":"output.md","content":"done"}`,
+		}}},
+		llm.Message{Role: llm.RoleAssistant, Content: "ok", StopReason: llm.StopEnd},
+	)
+	b := New(Options{
+		Model:  "fake",
+		Stream: stream,
+		Subagent: func(ctx context.Context, req subagent.Request) (subagent.Result, error) {
+			delegated = &req
+			return subagent.Result{Success: true, Text: "结论已查明"}, nil
+		},
+	})
+	dir := t.TempDir()
+	res, err := b.Execute(context.Background(), exec.Request{
+		WorkDir: dir, Prompt: "分工", Targets: []string{"output.md"},
+	})
+	if err != nil || !res.Success {
+		t.Fatalf("execute: err=%v res=%+v logs=%s", err, res, res.Logs)
+	}
+	if delegated == nil || delegated.Goal != "查证数据" {
+		t.Fatalf("factory not invoked with fields: %+v", delegated)
+	}
+	sawDelegate := false
+	for _, names := range c.toolDecls {
+		for _, n := range names {
+			if n == "delegate_task" {
+				sawDelegate = true
+			}
+		}
+	}
+	if !sawDelegate {
+		t.Fatal("delegate_task must be declared when Subagent factory is set")
+	}
+}
diff --git a/runtime/subagent/subagent.go b/runtime/subagent/subagent.go
new file mode 100644
index 0000000..f7c2199
--- /dev/null
+++ b/runtime/subagent/subagent.go
@@ -0,0 +1,103 @@
+// Package subagent 定义委派端口：内核不内置嵌套执行（那是编排层职责），
+// 只提供工具面与信息集契约；宿主（产品 SpawnSubagent、小队引擎等）
+// 注入 Factory 实现真实派生执行。未注入则 delegate_task 不注册（fail-closed）。
+//
+// 信息集对齐 agent-execution 标准的委派条款：目标、输入、写范围、非目标、
+// 完成判据、预算与回传格式——子任务不能从父任务目标推导额外权限。
+package subagent
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"sort"
+	"strings"
+	"time"
+
+	"agent-native/runtime/tools"
+)
+
+// Request 是一次委派的完整信息集（模型经工具参数逐项填写）。
+type Request struct {
+	Goal         string   `json:"goal"`
+	Inputs       string   `json:"inputs,omitempty"`
+	WriteScope   string   `json:"write_scope,omitempty"`
+	NonGoals     string   `json:"non_goals,omitempty"`
+	DoneCriteria string   `json:"done_criteria,omitempty"`
+	Deliverables []string `json:"deliverables,omitempty"`
+	// Deadline / MaxToolCalls 是宿主注入的预算余量（模型不可自行扩权）。
+	Deadline    time.Time `json:"-"`
+	MaxToolCalls int      `json:"-"`
+}
+
+// Result 是子代理的回传：至少包含结论文本；文件由宿主按写范围物化。
+type Result struct {
+	Success bool
+	Text    string
+	Files   map[string][]byte
+	Err     string
+}
+
+// Factory 由宿主注入；ctx 取消必须传播到子执行。
+type Factory func(ctx context.Context, req Request) (Result, error)
+
+type delegateTool struct{ factory Factory }
+
+// Register 把 delegate_task 工具注册进注册表（factory 为 nil 时不注册）。
+func Register(r *tools.Registry, factory Factory) {
+	if factory == nil {
+		return
+	}
+	r.Register(&delegateTool{factory: factory})
+}
+
+func (t *delegateTool) Name() string { return "delegate_task" }
+func (t *delegateTool) Description() string {
+	return "Delegate a self-contained subtask to a fresh sub-agent. Fill every field: goal, inputs (with versions), write_scope (directory the sub-agent may write), non_goals, done_criteria, deliverables. The sub-agent cannot exceed your permissions; report back its conclusion and files."
+}
+func (t *delegateTool) Parameters() json.RawMessage {
+	return json.RawMessage(`{"type":"object","required":["goal","done_criteria"],"properties":{
+		"goal":{"type":"string"},
+		"inputs":{"type":"string"},
+		"write_scope":{"type":"string"},
+		"non_goals":{"type":"string"},
+		"done_criteria":{"type":"string"},
+		"deliverables":{"type":"array","items":{"type":"string"}}
+	}}`)
+}
+
+func (t *delegateTool) Execute(ctx context.Context, args json.RawMessage) (tools.Result, error) {
+	var req Request
+	if err := json.Unmarshal(args, &req); err != nil {
+		return tools.Result{}, err
+	}
+	if strings.TrimSpace(req.Goal) == "" {
+		return tools.Result{Content: "goal is empty", IsError: true}, nil
+	}
+	if ctx.Err() != nil {
+		return tools.Result{Content: "delegation canceled before start: " + ctx.Err().Error(), IsError: true}, nil
+	}
+	res, err := t.factory(ctx, req)
+	if err != nil {
+		return tools.Result{Content: fmt.Sprintf("sub-agent failed: %v", err), IsError: true}, nil
+	}
+	var b strings.Builder
+	if res.Success {
+		b.WriteString("[sub-agent succeeded]\n")
+	} else {
+		b.WriteString("[sub-agent failed]\n")
+	}
+	if res.Err != "" {
+		b.WriteString("error: " + res.Err + "\n")
+	}
+	b.WriteString(res.Text)
+	if len(res.Files) > 0 {
+		names := make([]string, 0, len(res.Files))
+		for name := range res.Files {
+			names = append(names, name)
+		}
+		sort.Strings(names)
+		b.WriteString("\nfiles: " + strings.Join(names, ", "))
+	}
+	return tools.Result{Content: b.String(), IsError: !res.Success}, nil
+}
diff --git a/runtime/subagent/subagent_test.go b/runtime/subagent/subagent_test.go
new file mode 100644
index 0000000..1c58bfb
--- /dev/null
+++ b/runtime/subagent/subagent_test.go
@@ -0,0 +1,86 @@
+package subagent
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+	"testing"
+
+	"agent-native/runtime/tools"
+)
+
+func TestRegisterNilFactoryNoop(t *testing.T) {
+	reg := tools.NewRegistry(t.TempDir())
+	Register(reg, nil)
+	for _, d := range reg.Decls() {
+		if d.Name == "delegate_task" {
+			t.Fatal("nil factory must not register delegate_task")
+		}
+	}
+}
+
+func TestDelegateToolRoundTrip(t *testing.T) {
+	var got Request
+	reg := tools.NewRegistry(t.TempDir())
+	Register(reg, func(ctx context.Context, req Request) (Result, error) {
+		got = req
+		return Result{
+			Success: true,
+			Text:    "调研完成：结论 A。",
+			Files:   map[string][]byte{"notes.md": []byte("n"), "data/table.csv": []byte("c")},
+		}, nil
+	})
+	res := reg.Execute(context.Background(), "delegate_task", json.RawMessage(`{
+		"goal":"调研主题 X",
+		"inputs":"docs/v2 规范",
+		"write_scope":"research/",
+		"non_goals":"不做实现",
+		"done_criteria":"产出三来源对照表",
+		"deliverables":["notes.md","data/table.csv"]
+	}`))
+	if res.IsError {
+		t.Fatal(res.Content)
+	}
+	if got.Goal != "调研主题 X" || got.WriteScope != "research/" || got.DoneCriteria != "产出三来源对照表" {
+		t.Fatalf("delegation fields lost: %+v", got)
+	}
+	if !strings.Contains(res.Content, "[sub-agent succeeded]") ||
+		!strings.Contains(res.Content, "调研完成") ||
+		!strings.Contains(res.Content, "files: data/table.csv, notes.md") {
+		t.Fatalf("result text wrong:\n%s", res.Content)
+	}
+}
+
+func TestDelegateToolFailureAndValidation(t *testing.T) {
+	reg := tools.NewRegistry(t.TempDir())
+	Register(reg, func(ctx context.Context, req Request) (Result, error) {
+		return Result{Success: false, Err: "子任务超出预算"}, nil
+	})
+	res := reg.Execute(context.Background(), "delegate_task", json.RawMessage(`{"goal":"g","done_criteria":"d"}`))
+	if !res.IsError || !strings.Contains(res.Content, "[sub-agent failed]") || !strings.Contains(res.Content, "子任务超出预算") {
+		t.Fatalf("failure must propagate, got %+v", res)
+	}
+	// goal 必填（schema 校验拦截）。
+	res = reg.Execute(context.Background(), "delegate_task", json.RawMessage(`{"done_criteria":"d"}`))
+	if !res.IsError || !strings.Contains(res.Content, "required argument goal") {
+		t.Fatalf("missing goal must fail schema validation, got %+v", res)
+	}
+}
+
+func TestDelegateToolFactoryErrorAndCancel(t *testing.T) {
+	reg := tools.NewRegistry(t.TempDir())
+	Register(reg, func(ctx context.Context, req Request) (Result, error) {
+		return Result{}, context.Canceled
+	})
+	res := reg.Execute(context.Background(), "delegate_task", json.RawMessage(`{"goal":"g","done_criteria":"d"}`))
+	if !res.IsError || !strings.Contains(res.Content, "sub-agent failed") {
+		t.Fatalf("factory error must surface, got %+v", res)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	res = reg.Execute(ctx, "delegate_task", json.RawMessage(`{"goal":"g","done_criteria":"d"}`))
+	if !res.IsError || !strings.Contains(res.Content, "canceled before start") {
+		t.Fatalf("pre-canceled delegation must not start, got %+v", res)
+	}
+}