diff --git a/.gitmodules b/.gitmodules
index ef67b32..032d44a 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,9 @@
 [submodule "deps/development-guidelines"]
 	path = deps/development-guidelines
 	url = ssh://git@git-ssh.u1680832.nyat.app:31411/weichen/Development-Guidelines.git
+[submodule "deps/error-code-system"]
+	path = deps/error-code-system
+	url = ssh://git@git-ssh.u1680832.nyat.app:31411/weichen/Error-Code-System.git
+[submodule "deps/logging-system"]
+	path = deps/logging-system
+	url = ssh://git@git-ssh.u1680832.nyat.app:31411/weichen/Logging-System.git
diff --git a/PROJECT.md b/PROJECT.md
index 645963a..061827e 100644
--- a/PROJECT.md
+++ b/PROJECT.md
@@ -21,8 +21,8 @@
 | 逻辑 ID | 路径 | 角色 |
 |---|---|---|
 | development-guidelines | `deps/development-guidelines` | development-only，规范文本 |
-| error-code-system | `deps/error-code-system` | build-required（接入后） |
-| logging-system | `deps/logging-system` | build-required（接入后） |
+| error-code-system | `deps/error-code-system` | build-required，规范码目录 |
+| logging-system | `deps/logging-system` | build-required，可选日志器 |
 
 克隆：
 
diff --git a/README.md b/README.md
index 627b415..c734c93 100644
--- a/README.md
+++ b/README.md
@@ -9,9 +9,9 @@
 
 | 层 | 职责 | 依赖边界 |
 |---|---|---|
-| contract | 执行契约：Request/Result/Outcome/Error/Capability/Backend/Resolver | 不依赖内核、产品类型、数据库、配置 |
+| contract | 执行契约：Request/Result/Outcome/Error/Capability/Backend/Resolver | 不依赖内核、产品类型、数据库、配置，也不导入错误码库 |
 | exec | 执行端口：Backend/Request/Result/ProcessEvent、步骤重试与失败分类、交付物物化、Stub、并发限流 | 面向调用方的执行端口 |
-| runtime | 多轮循环、工具调度、模型调用、执行会话 | 实现 contract；不导入 Core/Squad |
+| runtime | 多轮循环、工具调度、模型调用、执行会话 | 不导入 Core/Squad；可选使用日志库，nil 日志器不改变结果 |
 | adapters | PI Runner transport / typed-result-v1；native：自研内核 runtime → exec.Backend（规范后端名 agent-native，含会话毒化轮转——resume-unsafe 失败后自动换新会话） | 显式映射外部差异，不伪造缺失能力 |
 | conformance | 所有 Backend 共用的行为验收 | fake 验证契约，真实 adapter 验证能力 |
 
@@ -37,6 +37,22 @@
 - 失败副作用显式分类（none/possible）；possible 禁止无条件重放。
 - 重试单一责任层：步骤级归调用方，传输级有界归 adapter，turn 上限归 runtime。
 - Workspace 路径授权 ≠ OS 沙箱。
+- `contract.ErrorCode` 取值是 `agent.*` 规范码。`ErrorCode()` / `ErrorFields()` 供日志库识别，本包不导入错误码库。
+
+## 依赖子模块
+
+| 路径 | 作用 |
+|---|---|
+| `deps/development-guidelines` | 开发规范，不参与编译 |
+| `deps/error-code-system` | 规范码目录。`go.mod` 的 `replace` 指向这里 |
+| `deps/logging-system` | 结构化日志。runtime 与 native 适配器可选使用 |
+
+版本以本仓 gitlink 为准。`scripts/submodule-consistency.sh` 核对 gitlink 与检出的 HEAD。
+
+```bash
+git clone --recurse-submodules ssh://git@git-ssh.u1680832.nyat.app:31411/weichen/Agent-Native.git
+# 已克隆时：git submodule update --init --recursive
+```
 
 ## CodeGraph
 
@@ -58,9 +74,11 @@ go test ./...
 ```
 require agent-native v0.0.0
 
-replace agent-native => ../Agent-Native
+replace agent-native => ./deps/agent-native
 ```
 
+本仓自己的 `go.mod` 则把错误码库和日志库替换到 `./deps/`。消费方若同时依赖这三仓，必须在消费方 `go.mod` 里写自己的 `replace`：依赖模块内部的 `replace` 不会在上层构建中生效。
+
 远程：`ssh://git@git-ssh.u1680832.nyat.app:31411/weichen/Agent-Native.git`
 
 ## CI
diff --git a/adapters/native/backend.go b/adapters/native/backend.go
index e421940..9bccc40 100644
--- a/adapters/native/backend.go
+++ b/adapters/native/backend.go
@@ -17,6 +17,8 @@ import (
 	"agent-native/runtime/llm"
 	"agent-native/runtime/session"
 	"agent-native/runtime/tools"
+
+	"logging-system/logsys"
 )
 
 // Options 构造后端所需的模型接入与执行参数（由组合根注入，无产品依赖）。
@@ -28,6 +30,10 @@ type Options struct {
 	Timeout  time.Duration
 	// Stream 测试注入的流函数；缺省按 APIBase/APIKey 构造 llm.Client。
 	Stream llm.StreamFunc
+	// Log 可选。nil 时丢弃日志。
+	Log *logsys.Logger
+	// ExecutionID 写入日志，不参与执行控制。
+	ExecutionID string
 }
 
 // Backend 以自研内核实现 exec.Backend。
@@ -35,7 +41,7 @@ type Backend struct {
 	opts Options
 	// lastFailure 记录各工作目录上次失败原因，用于会话毒化检测
 	// （context_overflow 等错误续跑同一会话只会复现失败，须换新会话）。
-	mu         sync.Mutex
+	mu          sync.Mutex
 	lastFailure map[string]string
 }
 
@@ -135,6 +141,14 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 		b.mu.Lock()
 		b.lastFailure[workDir] = reason
 		b.mu.Unlock()
+		assessment := exec.AssessStepFailure(exec.StepFailureSignals{
+			Err:     runRes.Err,
+			WorkDir: workDir,
+			Result:  &exec.Result{ErrorReason: reason, Retryable: runRes.Retryable, Logs: logs.String()},
+		})
+		b.logger().Error("native step failure classified", runRes.Err,
+			"failure_class", assessment.Class.String(),
+			"work_dir", workDir)
 		res := &exec.Result{Success: false, ErrorReason: reason, Logs: logs.String(), Retryable: runRes.Retryable}
 		if runRes.StopReason == llm.StopAborted {
 			res.Retryable = true
@@ -170,6 +184,8 @@ func (b *Backend) run(ctx context.Context, reg *tools.Registry, store *session.S
 		Stream:       stream,
 		Session:      store,
 		MaxTurns:     b.opts.MaxTurns,
+		Log:          b.logger(),
+		ExecutionID:  b.opts.ExecutionID,
 		OnEvent: func(ev runtime.Event) {
 			logs.WriteString(ev.Type)
 			if ev.Tool != "" {
@@ -224,10 +240,22 @@ func (b *Backend) rotateIfPoisoned(workDir string) {
 	if _, err := os.Stat(path); err != nil {
 		return
 	}
+	b.logger().Warn("rotating poisoned session", "work_dir", workDir)
 	_ = os.Rename(path, filepath.Join(workDir, ".agentx",
 		"transcript.poisoned."+time.Now().UTC().Format("20060102T150405.000000000")+".jsonl"))
 }
 
+func (b *Backend) logger() *logsys.Logger {
+	if b == nil || b.opts.Log == nil {
+		return logsys.Nop()
+	}
+	log := b.opts.Log.Module("native")
+	if b.opts.ExecutionID == "" {
+		return log
+	}
+	return log.With("execution_id", b.opts.ExecutionID)
+}
+
 // systemPrompt 组装系统提示：角色指令 + 交付物与工具档位约束。
 func systemPrompt(req exec.Request, profile string) string {
 	var b strings.Builder
diff --git a/adapters/pitransport/remote_result.go b/adapters/pitransport/remote_result.go
index be48ce7..c939733 100644
--- a/adapters/pitransport/remote_result.go
+++ b/adapters/pitransport/remote_result.go
@@ -7,11 +7,11 @@ import (
 )
 
 type remoteRunWire struct {
-	OK             bool      `json:"ok"`
-	RunID          string    `json:"run_id"`
-	FallbackReason string    `json:"fallback_reason"`
-	Retryable      bool      `json:"retryable"`
-	RunnerProtocol string    `json:"runner_protocol"`
+	OK             bool   `json:"ok"`
+	RunID          string `json:"run_id"`
+	FallbackReason string `json:"fallback_reason"`
+	Retryable      bool   `json:"retryable"`
+	RunnerProtocol string `json:"runner_protocol"`
 	Capabilities   *struct {
 		TypedResult bool `json:"typed_result"`
 	} `json:"capabilities"`
@@ -23,7 +23,7 @@ type remoteRunWire struct {
 }
 
 type decodedRemote struct {
-	OK       bool
+	OK        bool
 	Retryable bool
 	Reason    string
 	Incoming  map[string][]byte
@@ -91,17 +91,17 @@ func safeLegacyReason(reason string) string {
 	case r == "":
 		return "remote pi-agent reported task failure"
 	case strings.EqualFold(r, "prompt_empty"):
-		return "PROMPT_EMPTY"
+		return "agent.prompt_empty"
 	case strings.Contains(strings.ToLower(r), "unauthorized"):
-		return "UNAUTHORIZED"
+		return "agent.unauthorized"
 	case strings.Contains(strings.ToLower(r), "timeout"):
-		return "TIMEOUT"
+		return "agent.timeout"
 	default:
 		if strings.ContainsAny(r, "/\\") || strings.Contains(strings.ToLower(r), "token") {
-			return "RUN_FAILED"
+			return "agent.run_failed"
 		}
 		if len(r) > 64 {
-			return "RUN_FAILED"
+			return "agent.run_failed"
 		}
 		return r
 	}
diff --git a/adapters/pitransport/resultv1.go b/adapters/pitransport/resultv1.go
index 3085e44..0ca2798 100644
--- a/adapters/pitransport/resultv1.go
+++ b/adapters/pitransport/resultv1.go
@@ -20,20 +20,22 @@ const (
 
 var ErrTypedResult = fmt.Errorf("pitransport: typed result_v1 rejected")
 
+// 对外错误码与 Error-Code-System 的 agent 域一致。
+// CANCELLED 并入 agent.canceled，MISSING_TARGET 并入 agent.missing_deliverable。
 var allowedErrorCodes = map[string]struct{}{
-	"PROMPT_EMPTY":   {},
-	"UNAUTHORIZED":   {},
-	"TIMEOUT":        {},
-	"CANCELLED":      {},
-	"TRANSIENT":      {},
-	"MISSING_TARGET": {},
-	"RUN_FAILED":     {},
+	"agent.prompt_empty":        {},
+	"agent.unauthorized":        {},
+	"agent.timeout":             {},
+	"agent.canceled":            {},
+	"agent.transient":           {},
+	"agent.missing_deliverable": {},
+	"agent.run_failed":          {},
 }
 
 var retryableErrorCodes = map[string]struct{}{
-	"TIMEOUT":   {},
-	"CANCELLED": {},
-	"TRANSIENT": {},
+	"agent.timeout":   {},
+	"agent.canceled":  {},
+	"agent.transient": {},
 }
 
 type ResultV1Member struct {
diff --git a/adapters/pitransport/resultv1_test.go b/adapters/pitransport/resultv1_test.go
index 8446f05..3b9fb51 100644
--- a/adapters/pitransport/resultv1_test.go
+++ b/adapters/pitransport/resultv1_test.go
@@ -63,13 +63,13 @@ func TestResultV1RejectsMissingMemberBody(t *testing.T) {
 }
 
 func TestTypedRetryableAllowlist(t *testing.T) {
-	ok := BuildResultV1("r", "error", true, "TRANSIENT", nil)
+	ok := BuildResultV1("r", "error", true, "agent.transient", nil)
 	if !TypedRetryable(ok) {
-		t.Fatal("TRANSIENT retryable")
+		t.Fatal("agent.transient retryable")
 	}
-	denied := BuildResultV1("r", "error", true, "PROMPT_EMPTY", nil)
+	denied := BuildResultV1("r", "error", true, "agent.prompt_empty", nil)
 	if TypedRetryable(denied) {
-		t.Fatal("PROMPT_EMPTY must not retry")
+		t.Fatal("agent.prompt_empty must not retry")
 	}
 }
 
diff --git a/adapters/pitransport/testdata/result-v1.mjs b/adapters/pitransport/testdata/result-v1.mjs
index ac4f9fd..5c05737 100644
--- a/adapters/pitransport/testdata/result-v1.mjs
+++ b/adapters/pitransport/testdata/result-v1.mjs
@@ -8,35 +8,35 @@ export const MAX_RESULT_WIRE_BYTES = 6 * 1024 * 1024;
 /** Tail window for execution.log patches; full log remains on shared volume. */
 export const EXECUTION_LOG_PATCH_BYTES = 128 * 1024;
 
-const RETRYABLE_CODES = new Set(["TIMEOUT", "CANCELLED", "TRANSIENT"]);
+const RETRYABLE_CODES = new Set(["agent.timeout", "agent.canceled", "agent.transient"]);
 const ALLOWED_CODES = new Set([
-  "PROMPT_EMPTY",
-  "UNAUTHORIZED",
-  "TIMEOUT",
-  "CANCELLED",
-  "TRANSIENT",
-  "MISSING_TARGET",
-  "RUN_FAILED",
+  "agent.prompt_empty",
+  "agent.unauthorized",
+  "agent.timeout",
+  "agent.canceled",
+  "agent.transient",
+  "agent.missing_deliverable",
+  "agent.run_failed",
 ]);
 
 export function typedErrorCode(payload) {
   const raw = String(payload?.fallback_reason || payload?.error || "");
   const t = raw.toLowerCase();
-  if (t.includes("prompt_empty")) return "PROMPT_EMPTY";
-  if (t.includes("unauthorized")) return "UNAUTHORIZED";
-  if (t.includes("timeout") || t.includes("timed out")) return "TIMEOUT";
-  if (t.includes("cancel")) return "CANCELLED";
+  if (t.includes("prompt_empty")) return "agent.prompt_empty";
+  if (t.includes("unauthorized")) return "agent.unauthorized";
+  if (t.includes("timeout") || t.includes("timed out")) return "agent.timeout";
+  if (t.includes("cancel")) return "agent.canceled";
   if (
     t.includes("connection") ||
     t.includes("terminated") ||
     t.includes("econnreset") ||
     t.includes("socket hang")
   ) {
-    return "TRANSIENT";
+    return "agent.transient";
   }
-  if (t.includes("missing target")) return "MISSING_TARGET";
-  if (payload?.retryable) return "TRANSIENT";
-  if (!payload?.ok) return "RUN_FAILED";
+  if (t.includes("missing target")) return "agent.missing_deliverable";
+  if (payload?.retryable) return "agent.transient";
+  if (!payload?.ok) return "agent.run_failed";
   return "";
 }
 
@@ -117,7 +117,7 @@ export function withResultV1(payload) {
     run_id: String(out.run_id || "unknown").slice(0, 128),
     outcome: ok ? "success" : "error",
     retryable,
-    error_code: ALLOWED_CODES.has(errorCode) ? errorCode : ok ? "" : "RUN_FAILED",
+    error_code: ALLOWED_CODES.has(errorCode) ? errorCode : ok ? "" : "agent.run_failed",
     members,
     content_digest: membersDigest(members),
   };
diff --git a/catalogcheck/align_test.go b/catalogcheck/align_test.go
new file mode 100644
index 0000000..8ffe78d
--- /dev/null
+++ b/catalogcheck/align_test.go
@@ -0,0 +1,34 @@
+package catalogcheck
+
+import (
+	"testing"
+
+	"agent-native/contract"
+	"error-code-system/errcode"
+)
+
+// 常量取值必须与错误码库种子码相同。旧短字符串只作为错误码库里的别名存在。
+func TestContractCodesMatchCatalog(t *testing.T) {
+	pairs := []struct {
+		got  contract.ErrorCode
+		want errcode.Code
+	}{
+		{contract.ErrCanceled, errcode.AgentCanceled},
+		{contract.ErrDeadlineExceeded, errcode.AgentDeadlineExceeded},
+		{contract.ErrBudgetExceeded, errcode.AgentBudgetExceeded},
+		{contract.ErrProviderUnavailable, errcode.AgentProviderUnavailable},
+		{contract.ErrProviderRejected, errcode.AgentProviderRejected},
+		{contract.ErrToolRejected, errcode.AgentToolRejected},
+		{contract.ErrPathOutsideWorkspace, errcode.AgentPathOutsideWorkspace},
+		{contract.ErrMissingCapability, errcode.AgentMissingCapability},
+		{contract.ErrMissingDeliverable, errcode.AgentMissingDeliverable},
+		{contract.ErrEmptyOutput, errcode.AgentEmptyOutput},
+		{contract.ErrUnknownOutcome, errcode.AgentUnknownOutcome},
+		{contract.ErrInternal, errcode.AgentInternal},
+	}
+	for _, pair := range pairs {
+		if string(pair.got) != string(pair.want) {
+			t.Errorf("contract %q != catalog %q", pair.got, pair.want)
+		}
+	}
+}
diff --git a/contract/contract.go b/contract/contract.go
index 450cb50..d22d727 100644
--- a/contract/contract.go
+++ b/contract/contract.go
@@ -52,8 +52,8 @@ const (
 
 // ToolProfile 是预定义工具策略名；与现有产品配置兼容。
 const (
-	ToolProfileWorkspace = "workspace"  // 默认：文档类工具受限集合
-	ToolProfileReasoning = "reasoning"  // 无工具，仅推理
+	ToolProfileWorkspace = "workspace" // 默认：文档类工具受限集合
+	ToolProfileReasoning = "reasoning" // 无工具，仅推理
 )
 
 // ToolPolicy 描述执行允许的工具范围。实现不得自行扩展；未知工具一律拒绝。
@@ -106,8 +106,8 @@ type Request struct {
 	// SessionScope 为隔离身份；可为零值（一次性任务）。
 	SessionScope SessionScope `json:"session_scope"`
 
-	Prompt       string    `json:"prompt"`
-	Instructions string    `json:"instructions,omitempty"`
+	Prompt       string `json:"prompt"`
+	Instructions string `json:"instructions,omitempty"`
 	// Context 为可选历史消息；实现不得将其与 Prompt 之外的数据混合。
 	Context []Message `json:"context,omitempty"`
 
@@ -143,12 +143,12 @@ const (
 type EventKind string
 
 const (
-	EventTextDelta       EventKind = "text_delta"
-	EventReasoningDelta  EventKind = "reasoning_delta"
-	EventToolCallDelta   EventKind = "tool_call_delta"
-	EventToolExecStart   EventKind = "tool_execution_start"
-	EventToolExecEnd     EventKind = "tool_execution_end"
-	EventMessageEnd      EventKind = "message_end"
+	EventTextDelta      EventKind = "text_delta"
+	EventReasoningDelta EventKind = "reasoning_delta"
+	EventToolCallDelta  EventKind = "tool_call_delta"
+	EventToolExecStart  EventKind = "tool_execution_start"
+	EventToolExecEnd    EventKind = "tool_execution_end"
+	EventMessageEnd     EventKind = "message_end"
 )
 
 // Event 是过程事件帧；消费方（Core）负责映射为 SSE/持久化事件。
@@ -174,30 +174,60 @@ const (
 type ErrorCode string
 
 const (
-	ErrCanceled             ErrorCode = "canceled"
-	ErrDeadlineExceeded     ErrorCode = "deadline_exceeded"
-	ErrBudgetExceeded       ErrorCode = "budget_exceeded"
-	ErrProviderUnavailable  ErrorCode = "provider_unavailable"
-	ErrProviderRejected     ErrorCode = "provider_rejected"
-	ErrToolRejected         ErrorCode = "tool_rejected"
-	ErrPathOutsideWorkspace ErrorCode = "path_outside_workspace"
-	ErrMissingCapability    ErrorCode = "missing_capability"
-	ErrMissingDeliverable   ErrorCode = "missing_deliverable"
-	ErrEmptyOutput          ErrorCode = "empty_output"
-	ErrUnknownOutcome       ErrorCode = "unknown_outcome"
-	ErrInternal             ErrorCode = "internal"
+	ErrCanceled             ErrorCode = "agent.canceled"
+	ErrDeadlineExceeded     ErrorCode = "agent.deadline_exceeded"
+	ErrBudgetExceeded       ErrorCode = "agent.budget_exceeded"
+	ErrProviderUnavailable  ErrorCode = "agent.provider_unavailable"
+	ErrProviderRejected     ErrorCode = "agent.provider_rejected"
+	ErrToolRejected         ErrorCode = "agent.tool_rejected"
+	ErrPathOutsideWorkspace ErrorCode = "agent.path_outside_workspace"
+	ErrMissingCapability    ErrorCode = "agent.missing_capability"
+	ErrMissingDeliverable   ErrorCode = "agent.missing_deliverable"
+	ErrEmptyOutput          ErrorCode = "agent.empty_output"
+	ErrUnknownOutcome       ErrorCode = "agent.unknown_outcome"
+	ErrInternal             ErrorCode = "agent.internal"
 )
 
 // Error 是标准化执行错误。Retryable 仅表示传输级瞬时故障可由 adapter 有界
 // 重试或调用方作为新步骤重试；与 SideEffects 独立判定。
 type Error struct {
-	Code       ErrorCode  `json:"code"`
-	Reason     string     `json:"reason,omitempty"`
-	Retryable  bool       `json:"retryable,omitempty"`
+	Code        ErrorCode   `json:"code"`
+	Reason      string      `json:"reason,omitempty"`
+	Retryable   bool        `json:"retryable,omitempty"`
 	SideEffects SideEffects `json:"side_effects"`
 }
 
-func (e *Error) Error() string { return string(e.Code) + ": " + e.Reason }
+func (e *Error) Error() string {
+	if e == nil {
+		return ""
+	}
+	return string(e.Code) + ": " + e.Reason
+}
+
+// ErrorCode 返回规范码字符串。日志库用这个方法识别错误，因此 contract 不导入错误码模块。
+func (e *Error) ErrorCode() string {
+	if e == nil {
+		return ""
+	}
+	return string(e.Code)
+}
+
+// ErrorFields 返回可写入日志的字段。执行标识由调用方随日志字段另传，不放进本结构。
+func (e *Error) ErrorFields() map[string]any {
+	if e == nil {
+		return nil
+	}
+	fields := map[string]any{
+		"retryable": e.Retryable,
+	}
+	if e.Reason != "" {
+		fields["reason"] = e.Reason
+	}
+	if e.SideEffects != "" {
+		fields["side_effects"] = string(e.SideEffects)
+	}
+	return fields
+}
 
 // Usage 报告 token 用量；实现报告不了时保持零值，不猜测。
 type Usage struct {
diff --git a/contract/contract_test.go b/contract/contract_test.go
index 88087ee..9349258 100644
--- a/contract/contract_test.go
+++ b/contract/contract_test.go
@@ -26,7 +26,7 @@ func TestFakeBackendSuite(t *testing.T) {
 func TestFakeCancelSemantics(t *testing.T) {
 	block := make(chan struct{})
 	b := &conformance.FakeBackend{
-		Desc: contract.BackendDescriptor{Name: "fake", Capabilities: []contract.Capability{contract.CapCancel}},
+		Desc:       contract.BackendDescriptor{Name: "fake", Capabilities: []contract.Capability{contract.CapCancel}},
 		BlockUntil: block,
 	}
 	conformance.Run(t, conformance.Case{
@@ -41,3 +41,23 @@ func TestFakeCancelSemantics(t *testing.T) {
 		t.Fatal("backend must observe ctx cancellation before returning")
 	}
 }
+
+func TestErrorDuckTypeForLogs(t *testing.T) {
+	e := &contract.Error{
+		Code:        contract.ErrProviderUnavailable,
+		Reason:      "down",
+		Retryable:   true,
+		SideEffects: contract.SideEffectNone,
+	}
+	if e.ErrorCode() != "agent.provider_unavailable" {
+		t.Fatal(e.ErrorCode())
+	}
+	fields := e.ErrorFields()
+	if fields["reason"] != "down" || fields["side_effects"] != "none" || fields["retryable"] != true {
+		t.Fatalf("%v", fields)
+	}
+	var nilErr *contract.Error
+	if nilErr.ErrorCode() != "" || nilErr.ErrorFields() != nil {
+		t.Fatal("nil error")
+	}
+}
diff --git a/deps/error-code-system b/deps/error-code-system
new file mode 160000
index 0000000..b67696d
--- /dev/null
+++ b/deps/error-code-system
@@ -0,0 +1 @@
+Subproject commit b67696d393e7abfbdd16fdde1064c07f5ecd2f72
diff --git a/deps/logging-system b/deps/logging-system
new file mode 160000
index 0000000..7f59720
--- /dev/null
+++ b/deps/logging-system
@@ -0,0 +1 @@
+Subproject commit 7f5972007bdcb6047ce7f95ee891f53e0af9d136
diff --git a/go.mod b/go.mod
index 4de126e..f46d604 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,12 @@
 module agent-native
 
 go 1.27
+
+require (
+	error-code-system v0.0.0
+	logging-system v0.0.0
+)
+
+replace error-code-system => ./deps/error-code-system
+
+replace logging-system => ./deps/logging-system
diff --git a/runtime/loop.go b/runtime/loop.go
index c125d9e..73291f7 100644
--- a/runtime/loop.go
+++ b/runtime/loop.go
@@ -9,6 +9,8 @@ import (
 	"agent-native/runtime/llm"
 	"agent-native/runtime/session"
 	"agent-native/runtime/tools"
+
+	"logging-system/logsys"
 )
 
 const (
@@ -39,6 +41,10 @@ type Config struct {
 	GetSteering   func() []llm.Message
 	GetFollowUp   func() []llm.Message
 	OnEvent       func(Event)
+	// Log 可选。nil 时丢弃日志，不改变循环结果。
+	Log *logsys.Logger
+	// ExecutionID 只用于日志字段，不参与控制流。
+	ExecutionID string
 }
 
 // Result is the final assistant text and the transcript produced by one run.
@@ -87,11 +93,13 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 	var usage llm.Usage
 	for turn := 0; turn < cfg.MaxTurns; turn++ {
 		if ctx.Err() != nil {
+			cfg.logger().Error("runtime turn aborted", ctx.Err())
 			return Result{Text: last.Content, Messages: messages, StopReason: llm.StopAborted, Err: ctx.Err()}, nil
 		}
 		emit(cfg, Event{Type: "turn_start"})
 		end, errEv := consume(ctx, cfg, messages)
 		if errEv != nil {
+			cfg.logger().Error("runtime turn failed", errEv, "retryable", end.Retryable)
 			return Result{Text: end.Message.Content, Messages: messages, StopReason: end.Message.StopReason, Err: errEv, Retryable: end.Retryable}, nil
 		}
 		last = end.Message
@@ -136,15 +144,28 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 		emit(cfg, Event{Type: "agent_end", Message: last})
 		return Result{Text: last.Content, Messages: messages, StopReason: last.StopReason, Usage: usage}, nil
 	}
+	errCap := errString("max turns exceeded")
+	cfg.logger().Error("runtime turn cap hit", errCap)
 	return Result{
 		Text:       last.Content,
 		Messages:   messages,
 		StopReason: llm.StopError,
 		Usage:      usage,
-		Err:        errString("max turns exceeded"),
+		Err:        errCap,
 	}, nil
 }
 
+func (cfg Config) logger() *logsys.Logger {
+	if cfg.Log == nil {
+		return logsys.Nop()
+	}
+	log := cfg.Log.Module("runtime")
+	if cfg.ExecutionID == "" {
+		return log
+	}
+	return log.With("execution_id", cfg.ExecutionID)
+}
+
 func systemText(cfg Config) string {
 	var b strings.Builder
 	b.WriteString(cfg.SystemPrompt)
diff --git a/scripts/submodule-consistency.sh b/scripts/submodule-consistency.sh
new file mode 100755
index 0000000..76d427b
--- /dev/null
+++ b/scripts/submodule-consistency.sh
@@ -0,0 +1,22 @@
+#!/bin/sh
+# 核对本仓 gitlink 与已检出子模块 HEAD 是否一致。
+# 嵌套副本是否与消费方自己的 deps 相同，由消费方仓库的同名脚本比较。
+set -eu
+cd "$(dirname "$0")/.."
+fail=0
+for path in deps/development-guidelines deps/error-code-system deps/logging-system; do
+  if [ ! -e "$path/.git" ]; then
+    echo "missing submodule checkout: $path" >&2
+    fail=1
+    continue
+  fi
+  recorded=$(git rev-parse ":$path")
+  actual=$(git -C "$path" rev-parse HEAD)
+  if [ "$recorded" != "$actual" ]; then
+    echo "gitlink mismatch: $path recorded=$recorded HEAD=$actual" >&2
+    fail=1
+  else
+    echo "ok $path $recorded"
+  fi
+done
+exit "$fail"