Merge pull request 'Record tool intent before execution and add file checkpoints' (#14) from feature/durable-rewind into main

adapters/native/backend.go

@@ -14,6 +14,7 @@ import (
 
 	"agent-native/exec"
 	"agent-native/runtime"
+	"agent-native/runtime/checkpoint"
 	"agent-native/runtime/filestate"
 	"agent-native/runtime/hooks"
 	"agent-native/runtime/llm"
@@ -39,13 +40,15 @@ type ModelOptions struct {
 
 // ToolOptions 是可选工具装配。nil 字段不注册对应工具。
 type ToolOptions struct {
-	Search      tools.SearchProvider
-	Exec        *tools.ExecConfig
-	Fetch       *tools.FetchConfig
-	MCP         *mcp.Manager
-	SkillsRoots []string
-	Subagent    subagent.Factory
-	HostTools   []tools.Tool
+	Search           tools.SearchProvider
+	Exec             *tools.ExecConfig
+	Fetch            *tools.FetchConfig
+	MCP              *mcp.Manager
+	SkillsRoots      []string
+	Subagent         subagent.Factory
+	HostTools        []tools.Tool
+	Checkpoints      *checkpoint.Log
+	CheckpointAnchor func() string
 }
 
 // SessionOptions 是单次执行的会话预算与压缩。
@@ -58,6 +61,8 @@ type SessionOptions struct {
 type ObserveOptions struct {
 	Log         *logsys.Logger
 	ExecutionID string
+	// Trace 交给运行循环。nil 不采集。
+	Trace func(name string, attrs map[string]string) func()
 }
 
 // GateOptions 把直连已经使用的停止、提醒和工具钩子交给小队成员。零值不改变行为。
@@ -184,7 +189,7 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 
 	var reg *tools.Registry
 	if profile == exec.ToolProfileWorkspace {
-		reg = tools.WorkspaceToolsTracked(workDir, filestate.New())
+		reg = tools.WorkspaceToolsCheckpointed(workDir, filestate.New(), b.opts.Checkpoints, b.opts.CheckpointAnchor)
 		skills.RegisterLoader(reg, skillStore)
 		if b.opts.Search != nil {
 			tools.RegisterSearch(reg, b.opts.Search)
@@ -348,6 +353,7 @@ func (b *Backend) run(ctx context.Context, model string, budget *runtime.Budget,
 		Reminders:    b.opts.Reminders,
 		RepeatGuard:  b.opts.RepeatGuard,
 		Hooks:        gateBus(b.opts.GateOptions),
+		Trace:        b.opts.Trace,
 		OnEvent: func(ev runtime.Event) {
 			logs.WriteString(ev.Type)
 			if ev.Tool != "" {

runtime/checkpoint/checkpoint.go

@@ -0,0 +1,242 @@
+// Package checkpoint 记录写文件之前的内容，并按用户消息把文件退回去。
+// 只追踪显式交给它的写入。shell 与 python 的改动不经过这里。
+package checkpoint
+
+import (
+	"bytes"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+// Record 是一次被追踪的写入。Before 是写入前的字节，After 是写入后的字节。
+type Record struct {
+	Seq     int    `json:"seq"`
+	Anchor  string `json:"anchor,omitempty"`
+	Root    string `json:"root"`
+	Path    string `json:"path"`
+	Existed bool   `json:"existed"`
+	Before  []byte `json:"before,omitempty"`
+	After   []byte `json:"after,omitempty"`
+}
+
+// Result 是一次回滚的分类。Skipped 是当前内容既不是写入后也不是写入前的文件。
+type Result struct {
+	Restored []string
+	Skipped  []string
+}
+
+// Log 是追加写的检查点文件。
+type Log struct {
+	path string
+	mu   sync.Mutex
+}
+
+func Open(path string) (*Log, error) {
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return nil, err
+	}
+	f, err := os.OpenFile(path, os.O_CREATE, 0o644)
+	if err != nil {
+		return nil, err
+	}
+	_ = f.Close()
+	return &Log{path: path}, nil
+}
+
+func (l *Log) Path() string { return l.path }
+
+// Record 追加一条检查点。rel 是相对 root 的路径。
+func (l *Log) Record(anchor, root, rel string, before []byte, existed bool, after []byte) error {
+	if l == nil {
+		return nil
+	}
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	all, err := l.read()
+	if err != nil {
+		return err
+	}
+	rec := Record{
+		Seq: len(all) + 1, Anchor: anchor, Root: root, Path: filepath.ToSlash(rel),
+		Existed: existed, Before: append([]byte(nil), before...), After: append([]byte(nil), after...),
+	}
+	raw, err := json.Marshal(rec)
+	if err != nil {
+		return err
+	}
+	f, err := os.OpenFile(l.path, os.O_APPEND|os.O_WRONLY, 0o644)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = f.Write(append(raw, '\n'))
+	return err
+}
+
+// Plan 列出从 anchor 起（含）会被回滚的文件，不改磁盘。
+// ordered 是用户消息 id 的时间顺序。
+func (l *Log) Plan(anchor string, ordered []string) (Result, error) {
+	if l == nil {
+		return Result{}, nil
+	}
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	all, err := l.read()
+	if err != nil {
+		return Result{}, err
+	}
+	return classify(all, anchor, ordered), nil
+}
+
+// Rewind 把 anchor 及其后的被追踪写入退回写入前。
+// 当前内容与最后一次记录的 After 不一致时跳过并列入 Skipped。
+func (l *Log) Rewind(anchor string, ordered []string) (Result, error) {
+	if l == nil {
+		return Result{}, nil
+	}
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	all, err := l.read()
+	if err != nil {
+		return Result{}, err
+	}
+	plan := classify(all, anchor, ordered)
+	for _, rel := range plan.Restored {
+		group := groupFor(selected(all, anchor, ordered), rel)
+		if err := restore(group); err != nil {
+			return Result{}, err
+		}
+	}
+	return plan, nil
+}
+
+func (l *Log) read() ([]Record, error) {
+	b, err := os.ReadFile(l.path)
+	if err != nil {
+		return nil, err
+	}
+	var out []Record
+	for _, line := range bytes.Split(b, []byte("\n")) {
+		line = bytes.TrimSpace(line)
+		if len(line) == 0 {
+			continue
+		}
+		var rec Record
+		if err := json.Unmarshal(line, &rec); err != nil {
+			return nil, err
+		}
+		out = append(out, rec)
+	}
+	return out, nil
+}
+
+func selected(all []Record, anchor string, ordered []string) []Record {
+	keep := map[string]bool{}
+	on := false
+	for _, id := range ordered {
+		if id == anchor {
+			on = true
+		}
+		if on {
+			keep[id] = true
+		}
+	}
+	if anchor != "" && len(ordered) == 0 {
+		keep[anchor] = true
+	}
+	var out []Record
+	for _, rec := range all {
+		if keep[rec.Anchor] {
+			out = append(out, rec)
+		}
+	}
+	return out
+}
+
+func classify(all []Record, anchor string, ordered []string) Result {
+	sel := selected(all, anchor, ordered)
+	seen := map[string]bool{}
+	var restored, skipped []string
+	for _, rec := range sel {
+		if seen[rec.Path] {
+			continue
+		}
+		seen[rec.Path] = true
+		group := groupFor(sel, rec.Path)
+		switch fileState(group) {
+		case stateRestore:
+			restored = append(restored, rec.Path)
+		case stateSkip:
+			skipped = append(skipped, rec.Path)
+		}
+	}
+	return Result{Restored: restored, Skipped: skipped}
+}
+
+func groupFor(sel []Record, rel string) []Record {
+	var group []Record
+	for _, rec := range sel {
+		if rec.Path == rel {
+			group = append(group, rec)
+		}
+	}
+	return group
+}
+
+const (
+	stateAlready = iota
+	stateRestore
+	stateSkip
+)
+
+func fileState(group []Record) int {
+	if len(group) == 0 {
+		return stateAlready
+	}
+	first, last := group[0], group[len(group)-1]
+	abs := filepath.Join(last.Root, filepath.FromSlash(last.Path))
+	current, err := os.ReadFile(abs)
+	missing := os.IsNotExist(err)
+	if err != nil && !missing {
+		return stateSkip
+	}
+	if missing {
+		if !last.Existed && len(last.After) == 0 {
+			return stateAlready
+		}
+		if !first.Existed && bytes.Equal(nil, first.Before) && len(last.After) > 0 {
+			return stateSkip
+		}
+		return stateSkip
+	}
+	if bytes.Equal(current, last.After) {
+		if !first.Existed {
+			return stateRestore
+		}
+		if bytes.Equal(current, first.Before) {
+			return stateAlready
+		}
+		return stateRestore
+	}
+	if first.Existed && bytes.Equal(current, first.Before) {
+		return stateAlready
+	}
+	return stateSkip
+}
+
+func restore(group []Record) error {
+	if len(group) == 0 {
+		return nil
+	}
+	first := group[0]
+	abs := filepath.Join(first.Root, filepath.FromSlash(first.Path))
+	if !first.Existed {
+		return os.Remove(abs)
+	}
+	if err := os.MkdirAll(filepath.Dir(abs), 0o755); err != nil {
+		return err
+	}
+	return os.WriteFile(abs, first.Before, 0o644)
+}

runtime/checkpoint/checkpoint_test.go

@@ -0,0 +1,80 @@
+package checkpoint
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestRewindRestoresTrackedWriteAndSkipsExternalChange(t *testing.T) {
+	root := t.TempDir()
+	log, err := Open(filepath.Join(t.TempDir(), "cp.jsonl"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(root, "keep.txt"), []byte("old"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := log.Record("m1", root, "keep.txt", []byte("old"), true, []byte("new")); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(root, "keep.txt"), []byte("new"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(root, "side.txt"), []byte("from-shell"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := log.Record("m1", root, "moved.txt", []byte("a"), true, []byte("b")); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(root, "moved.txt"), []byte("someone-else"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := log.Rewind("m1", []string{"m1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got.Restored) != 1 || got.Restored[0] != "keep.txt" {
+		t.Fatalf("restored %#v", got.Restored)
+	}
+	if len(got.Skipped) != 1 || got.Skipped[0] != "moved.txt" {
+		t.Fatalf("skipped %#v", got.Skipped)
+	}
+	body, err := os.ReadFile(filepath.Join(root, "keep.txt"))
+	if err != nil || string(body) != "old" {
+		t.Fatalf("keep.txt %q %v", body, err)
+	}
+	side, err := os.ReadFile(filepath.Join(root, "side.txt"))
+	if err != nil || string(side) != "from-shell" {
+		t.Fatalf("untracked file changed: %q %v", side, err)
+	}
+	moved, _ := os.ReadFile(filepath.Join(root, "moved.txt"))
+	if string(moved) != "someone-else" {
+		t.Fatalf("external edit was reverted: %q", moved)
+	}
+}
+
+func TestRewindRemovesCreatedFile(t *testing.T) {
+	root := t.TempDir()
+	log, err := Open(filepath.Join(t.TempDir(), "cp.jsonl"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(root, "new.txt"), []byte("hi"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := log.Record("m2", root, "new.txt", nil, false, []byte("hi")); err != nil {
+		t.Fatal(err)
+	}
+	got, err := log.Rewind("m2", []string{"m1", "m2"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got.Restored) != 1 {
+		t.Fatalf("restored %#v", got.Restored)
+	}
+	if _, err := os.Stat(filepath.Join(root, "new.txt")); !os.IsNotExist(err) {
+		t.Fatalf("created file still present: %v", err)
+	}
+}

runtime/durable_test.go

@@ -0,0 +1,210 @@
+package runtime
+
+import (
+	"context"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"agent-native/runtime/llm"
+	"agent-native/runtime/session"
+	"agent-native/runtime/tools"
+)
+
+type replayTool struct {
+	countingTool
+	replay string
+}
+
+func (r *replayTool) Replay() string {
+	if r.replay == "" {
+		return tools.ReplayNever
+	}
+	return r.replay
+}
+
+func TestPendingUnsafeToolIsNotRerun(t *testing.T) {
+	dir := t.TempDir()
+	st, err := session.Open(filepath.Join(dir, "s.jsonl"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := st.Append(llm.Message{
+		Role: llm.RoleAssistant, StopReason: llm.StopToolCalls,
+		ToolCalls: []llm.ToolCall{{ID: "c1", Name: "write_file", Arguments: `{}`}},
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if err := st.AppendToolIntent(session.ToolIntent{CallID: "c1", Name: "write_file", Arguments: `{}`, Replay: tools.ReplayNever}); err != nil {
+		t.Fatal(err)
+	}
+	tool := &countingTool{name: "write_file"}
+	reg := tools.NewRegistry(dir)
+	reg.Register(tool)
+	_, err = Run(context.Background(), Config{
+		Model: "fake", Session: st, Tools: reg, MaxTurns: 2,
+		Stream: script(llm.Message{Role: llm.RoleAssistant, Content: "later", StopReason: llm.StopEnd}),
+	}, llm.Message{Role: llm.RoleUser, Content: "next"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if tool.calls != 0 {
+		t.Fatalf("unsafe tool reran: %d", tool.calls)
+	}
+	msgs, err := st.Load()
+	if err != nil {
+		t.Fatal(err)
+	}
+	var paired bool
+	for _, m := range msgs {
+		if m.Role == llm.RoleTool && m.ToolCallID == "c1" && m.Content == unknownSideEffect {
+			paired = true
+		}
+	}
+	if !paired {
+		t.Fatalf("pair missing: %#v", msgs)
+	}
+}
+
+func TestPendingSafeToolRerunsOnce(t *testing.T) {
+	dir := t.TempDir()
+	st, err := session.Open(filepath.Join(dir, "s.jsonl"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := st.Append(llm.Message{
+		Role: llm.RoleAssistant, StopReason: llm.StopToolCalls,
+		ToolCalls: []llm.ToolCall{{ID: "c1", Name: "read_file", Arguments: `{}`}},
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if err := st.AppendToolIntent(session.ToolIntent{CallID: "c1", Name: "read_file", Arguments: `{}`, Replay: tools.ReplaySafe}); err != nil {
+		t.Fatal(err)
+	}
+	tool := &replayTool{countingTool: countingTool{name: "read_file"}, replay: tools.ReplaySafe}
+	reg := tools.NewRegistry(dir)
+	reg.Register(tool)
+	_, err = Run(context.Background(), Config{
+		Model: "fake", Session: st, Tools: reg, MaxTurns: 2,
+		Stream: script(llm.Message{Role: llm.RoleAssistant, Content: "later", StopReason: llm.StopEnd}),
+	}, llm.Message{Role: llm.RoleUser, Content: "next"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if tool.calls != 1 {
+		t.Fatalf("calls %d", tool.calls)
+	}
+	msgs, err := st.Load()
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, m := range msgs {
+		if m.Role == llm.RoleTool && m.ToolCallID == "c1" {
+			if m.Content != "ok" || strings.Contains(m.Content, unknownSideEffect) {
+				t.Fatalf("result %#v", m)
+			}
+			return
+		}
+	}
+	t.Fatal("missing tool result")
+}
+
+func TestStoredSafeCurrentNeverDoesNotRerun(t *testing.T) {
+	dir := t.TempDir()
+	st, err := session.Open(filepath.Join(dir, "s.jsonl"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := st.AppendToolIntent(session.ToolIntent{CallID: "c1", Name: "read_file", Arguments: `{}`, Replay: tools.ReplaySafe}); err != nil {
+		t.Fatal(err)
+	}
+	tool := &replayTool{countingTool: countingTool{name: "read_file"}, replay: tools.ReplayNever}
+	reg := tools.NewRegistry(dir)
+	reg.Register(tool)
+	if err := recoverPending(context.Background(), Config{Session: st, Tools: reg}); err != nil {
+		t.Fatal(err)
+	}
+	if tool.calls != 0 {
+		t.Fatalf("calls %d", tool.calls)
+	}
+}
+
+func TestFollowUpIsPersistedBeforeNextRequest(t *testing.T) {
+	dir := t.TempDir()
+	st, err := session.Open(filepath.Join(dir, "s.jsonl"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	sent := false
+	var saw bool
+	stream := func(ctx context.Context, model string, messages []llm.Message, tools []llm.ToolDecl, opts llm.StreamOptions) <-chan llm.Event {
+		ch := make(chan llm.Event, 1)
+		go func() {
+			defer close(ch)
+			for _, m := range messages {
+				if m.Content == "follow-please" {
+					loaded, err := st.Load()
+					if err != nil {
+						t.Errorf("load %v", err)
+					}
+					for _, got := range loaded {
+						if got.Content == "follow-please" {
+							saw = true
+						}
+					}
+				}
+			}
+			ch <- llm.Event{Kind: llm.KindMessageEnd, Message: llm.Message{Role: llm.RoleAssistant, Content: "ok", StopReason: llm.StopEnd}}
+		}()
+		return ch
+	}
+	_, err = Run(context.Background(), Config{
+		Model: "fake", Session: st, MaxTurns: 3, Stream: stream,
+		GetFollowUp: func() []llm.Message {
+			if sent {
+				return nil
+			}
+			sent = true
+			return []llm.Message{{Role: llm.RoleUser, Content: "follow-please"}}
+		},
+	}, llm.Message{Role: llm.RoleUser, Content: "go"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !saw {
+		t.Fatal("follow-up entered the request before it was stored")
+	}
+}
+
+func TestSpansUseAgreedNamesWithoutPrompt(t *testing.T) {
+	var names []string
+	var leaked bool
+	reg := tools.NewRegistry(t.TempDir())
+	reg.Register(&countingTool{name: "read_file"})
+	_, err := Run(context.Background(), Config{
+		Model: "fake", Tools: reg, MaxTurns: 2,
+		Trace: func(name string, attrs map[string]string) func() {
+			names = append(names, name)
+			if _, ok := attrs["prompt"]; ok || attrs["content"] != "" {
+				leaked = true
+			}
+			return func() {}
+		},
+		Stream: script(
+			llm.Message{Role: llm.RoleAssistant, StopReason: llm.StopToolCalls, ToolCalls: []llm.ToolCall{{ID: "1", Name: "read_file", Arguments: `{}`}}},
+			llm.Message{Role: llm.RoleAssistant, Content: "done", StopReason: llm.StopEnd},
+		),
+	}, llm.Message{Role: llm.RoleUser, Content: "用户的秘密提示词"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	joined := strings.Join(names, ",")
+	for _, want := range []string{"invoke_agent", "chat", "execute_tool"} {
+		if !strings.Contains(joined, want) {
+			t.Fatalf("names %s", joined)
+		}
+	}
+	if leaked {
+		t.Fatal("prompt leaked into span attrs")
+	}
+}

runtime/llm/client.go

@@ -92,6 +92,7 @@ func (c *Client) run(ctx context.Context, model string, messages []Message, tool
 		msg := fmt.Sprintf("provider status %d: %s", resp.StatusCode, strings.TrimSpace(string(slurp)))
 		ev := Event{
 			Kind:         KindError,
+			HTTPStatus:   resp.StatusCode,
 			Retryable:    StatusRetryable(resp.StatusCode) && !ContextOverflow(msg),
 			ErrorMessage: msg,
 			Err:          &StreamError{Message: msg, Retryable: StatusRetryable(resp.StatusCode) && !ContextOverflow(msg)},

runtime/llm/fallback.go

@@ -0,0 +1,79 @@
+package llm
+
+import "context"
+
+// WithFallback 在尚未转发任何增量时，遇到 5xx 就改用链上下一个模型。
+// fallbacks 为空时返回原来的 StreamFunc，不改变行为。
+func WithFallback(base StreamFunc, fallbacks []string, onSwitch func(from, to string)) StreamFunc {
+	chain := nonEmpty(fallbacks)
+	if base == nil || len(chain) == 0 {
+		return base
+	}
+	return func(ctx context.Context, model string, messages []Message, tools []ToolDecl, opts StreamOptions) <-chan Event {
+		out := make(chan Event)
+		go func() {
+			defer close(out)
+			models := append([]string{model}, chain...)
+			for i, current := range models {
+				forwarded := false
+				switchNext := false
+				for ev := range base(ctx, current, messages, tools, opts) {
+					if isDelta(ev) {
+						forwarded = true
+					}
+					if ev.Kind == KindError && !forwarded && serverError(ev) && i+1 < len(models) {
+						switchNext = true
+						if onSwitch != nil {
+							onSwitch(current, models[i+1])
+						}
+						break
+					}
+					select {
+					case out <- ev:
+					case <-ctx.Done():
+						return
+					}
+					if ev.Kind == KindMessageEnd || ev.Kind == KindError {
+						return
+					}
+				}
+				if !switchNext {
+					return
+				}
+			}
+		}()
+		return out
+	}
+}
+
+func nonEmpty(in []string) []string {
+	var out []string
+	seen := map[string]bool{}
+	for _, s := range in {
+		s = trimModel(s)
+		if s == "" || seen[s] {
+			continue
+		}
+		seen[s] = true
+		out = append(out, s)
+	}
+	return out
+}
+
+func trimModel(s string) string {
+	for len(s) > 0 && (s[0] == ' ' || s[0] == '\t') {
+		s = s[1:]
+	}
+	for len(s) > 0 && (s[len(s)-1] == ' ' || s[len(s)-1] == '\t') {
+		s = s[:len(s)-1]
+	}
+	return s
+}
+
+func isDelta(ev Event) bool {
+	return ev.Kind == KindTextDelta || ev.Kind == KindReasoningDelta || ev.Kind == KindToolCallDelta
+}
+
+func serverError(ev Event) bool {
+	return ev.HTTPStatus >= 500 && ev.HTTPStatus <= 599
+}

runtime/llm/fallback_test.go

@@ -0,0 +1,74 @@
+package llm
+
+import (
+	"context"
+	"testing"
+)
+
+func TestFallbackSwitchesOn5xxBeforeOutput(t *testing.T) {
+	var switched string
+	base := func(ctx context.Context, model string, messages []Message, tools []ToolDecl, opts StreamOptions) <-chan Event {
+		ch := make(chan Event, 2)
+		go func() {
+			defer close(ch)
+			if model == "primary" {
+				ch <- Event{Kind: KindError, HTTPStatus: 503, ErrorMessage: "provider status 503", Message: Message{Role: RoleAssistant, StopReason: StopError}}
+				return
+			}
+			ch <- Event{Kind: KindTextDelta, Text: "ok"}
+			ch <- Event{Kind: KindMessageEnd, Message: Message{Role: RoleAssistant, Content: "ok", StopReason: StopEnd}}
+		}()
+		return ch
+	}
+	stream := WithFallback(base, []string{"backup"}, func(from, to string) {
+		switched = from + "->" + to
+	})
+	var text string
+	var sawError bool
+	for ev := range stream(context.Background(), "primary", nil, nil, StreamOptions{}) {
+		if ev.Kind == KindTextDelta {
+			text += ev.Text
+		}
+		if ev.Kind == KindError {
+			sawError = true
+		}
+	}
+	if switched != "primary->backup" || text != "ok" || sawError {
+		t.Fatalf("switched %q text %q error %v", switched, text, sawError)
+	}
+}
+
+func TestFallbackStaysAfterFirstDelta(t *testing.T) {
+	calls := 0
+	base := func(ctx context.Context, model string, messages []Message, tools []ToolDecl, opts StreamOptions) <-chan Event {
+		calls++
+		ch := make(chan Event, 2)
+		go func() {
+			defer close(ch)
+			ch <- Event{Kind: KindTextDelta, Text: "partial"}
+			ch <- Event{Kind: KindError, HTTPStatus: 500, Message: Message{Role: RoleAssistant, StopReason: StopError}}
+		}()
+		return ch
+	}
+	stream := WithFallback(base, []string{"backup"}, func(from, to string) {
+		t.Fatal("switched after output")
+	})
+	n := 0
+	for range stream(context.Background(), "primary", nil, nil, StreamOptions{}) {
+		n++
+	}
+	if calls != 1 || n != 2 {
+		t.Fatalf("calls %d events %d", calls, n)
+	}
+}
+
+func TestEmptyFallbackIsIdentity(t *testing.T) {
+	base := func(ctx context.Context, model string, messages []Message, tools []ToolDecl, opts StreamOptions) <-chan Event {
+		ch := make(chan Event)
+		close(ch)
+		return ch
+	}
+	if WithFallback(base, nil, nil) == nil {
+		t.Fatal("nil stream")
+	}
+}

runtime/llm/types.go

@@ -103,6 +103,8 @@ type Event struct {
 	Err          error
 	Retryable    bool
 	ErrorMessage string
+	// HTTPStatus 是提供方的 HTTP 状态。0 表示这条错误不是 HTTP 响应。
+	HTTPStatus int
 	// RetryAfter is the provider's requested wait. HasRetryAfter distinguishes
 	// a real zero from a missing or unparseable header.
 	RetryAfter    time.Duration

runtime/loop.go

@@ -47,11 +47,14 @@ type Event struct {
 
 // Config drives one agent session.
 type Config struct {
-	Model         string
-	SystemPrompt  string
-	Tools         *tools.Registry
-	Stream        llm.StreamFunc
-	Session       *session.Store
+	Model        string
+	SystemPrompt string
+	Tools        *tools.Registry
+	Stream       llm.StreamFunc
+	Session      *session.Store
+	// Trace 开始一个 span，返回的函数结束它。nil 表示不采集。
+	// 属性里不要放提示词正文。
+	Trace         func(name string, attrs map[string]string) func()
 	MaxTurns      int
 	ToolExecution string
 	GetSteering   func() []llm.Message
@@ -154,6 +157,8 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 		cfg.ToolExecution = ExecSequential
 	}
 	serializeHostCallbacks(&cfg)
+	endRun := startSpan(cfg, "invoke_agent", map[string]string{"model": cfg.Model})
+	defer endRun()
 	var messages []llm.Message
 	if cfg.Session != nil {
 		loaded, err := cfg.Session.Load()
@@ -162,6 +167,16 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 		}
 		messages = loaded
 	}
+	if err := recoverPending(ctx, cfg); err != nil {
+		return Result{}, err
+	}
+	if cfg.Session != nil {
+		loaded, err := cfg.Session.Load()
+		if err != nil {
+			return Result{}, err
+		}
+		messages = loaded
+	}
 	if len(messages) == 0 && len(cfg.History) > 0 {
 		messages = append([]llm.Message{}, cfg.History...)
 	}
@@ -349,6 +364,8 @@ func systemText(cfg Config) string {
 }
 
 func consume(ctx context.Context, cfg Config, messages []llm.Message) (llm.Event, error) {
+	endSpan := startSpan(cfg, "chat", map[string]string{"model": cfg.Model})
+	defer endSpan()
 	var decls []llm.ToolDecl
 	if cfg.Tools != nil {
 		for _, d := range cfg.Tools.Decls() {
@@ -576,6 +593,13 @@ func runOne(ctx context.Context, cfg Config, call llm.ToolCall) llm.Message {
 		}
 	}
 	emit(cfg, Event{Type: "tool_execution_update", Tool: call.Name, Detail: call.Arguments})
+	if err := commitToolIntent(cfg, call); err != nil {
+		msg := llm.Message{Role: llm.RoleTool, Name: call.Name, ToolCallID: call.ID, Content: err.Error(), IsError: true}
+		emit(cfg, Event{Type: "tool_execution_end", Tool: call.Name, Text: msg.Content})
+		return msg
+	}
+	endSpan := startSpan(cfg, "execute_tool", map[string]string{"tool": call.Name})
+	defer endSpan()
 	res := tools.Result{Content: "no tools configured", IsError: true}
 	known := cfg.Tools != nil && cfg.Tools.Has(call.Name)
 	switch {
@@ -609,10 +633,78 @@ func settle(cfg Config, last llm.Message, messages []llm.Message, usage llm.Usag
 }
 
 func prepareRequest(cfg Config, messages []llm.Message, turn int, repeats *repeatState, lengthNudge *bool) []llm.Message {
-	request := clearOldResults(cfg, messages)
+	request := clearOldResults(cfg, persistedProjection(cfg, messages))
 	return reminders.Attach(request, turnReminderTexts(cfg, turn, repeats, lengthNudge))
 }
 
+// persistedProjection 在有会话存储时只采用已经落盘的消息。
+// steer 与 follow-up 必须先写入存储，下一轮请求才会看见它们。
+func persistedProjection(cfg Config, messages []llm.Message) []llm.Message {
+	if cfg.Session == nil {
+		return messages
+	}
+	loaded, err := cfg.Session.Load()
+	if err != nil {
+		return messages
+	}
+	return loaded
+}
+
+const unknownSideEffect = "副作用未知，未重试"
+
+func recoverPending(ctx context.Context, cfg Config) error {
+	if cfg.Session == nil {
+		return nil
+	}
+	pending, err := cfg.Session.PendingIntents()
+	if err != nil {
+		return err
+	}
+	for _, in := range pending {
+		current := tools.ReplayNever
+		if cfg.Tools != nil {
+			current = cfg.Tools.Replay(in.Name)
+		}
+		msg := llm.Message{
+			Role: llm.RoleTool, Name: in.Name, ToolCallID: in.CallID,
+			Content: unknownSideEffect, IsError: true,
+		}
+		if in.Replay == tools.ReplaySafe && current == tools.ReplaySafe && cfg.Tools != nil {
+			res := cfg.Tools.Execute(ctx, in.Name, json.RawMessage(in.Arguments))
+			msg.Content = res.Content
+			msg.IsError = res.IsError
+		}
+		if err := persist(cfg, msg); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func commitToolIntent(cfg Config, call llm.ToolCall) error {
+	if cfg.Session == nil {
+		return nil
+	}
+	replay := tools.ReplayNever
+	if cfg.Tools != nil {
+		replay = cfg.Tools.Replay(call.Name)
+	}
+	return cfg.Session.AppendToolIntent(session.ToolIntent{
+		CallID: call.ID, Name: call.Name, Arguments: call.Arguments, Replay: replay,
+	})
+}
+
+func startSpan(cfg Config, name string, attrs map[string]string) func() {
+	if cfg.Trace == nil {
+		return func() {}
+	}
+	end := cfg.Trace(name, attrs)
+	if end == nil {
+		return func() {}
+	}
+	return end
+}
+
 func clearOldResults(cfg Config, messages []llm.Message) []llm.Message {
 	window := cfg.ContextWindow
 	if window <= 0 {

runtime/session/intent.go

@@ -0,0 +1,57 @@
+package session
+
+import (
+	"encoding/json"
+
+	"agent-native/runtime/llm"
+)
+
+// ToolIntent 是一次尚未配对结果的工具调用声明。
+type ToolIntent struct {
+	CallID    string `json:"callId"`
+	Name      string `json:"name"`
+	Arguments string `json:"arguments,omitempty"`
+	Replay    string `json:"replay"`
+}
+
+// AppendToolIntent 先落下「即将执行」。结果另写一条 tool 消息。
+func (s *Store) AppendToolIntent(in ToolIntent) error {
+	raw, err := json.Marshal(in)
+	if err != nil {
+		return err
+	}
+	_, err = s.AppendEntry(Entry{Type: TypeToolIntent, Data: raw})
+	return err
+}
+
+// PendingIntents 返回活动分支上还没有对应 tool 结果的意图。
+func (s *Store) PendingIntents() ([]ToolIntent, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	entries, err := s.readEntriesLocked()
+	if err != nil {
+		return nil, err
+	}
+	answered := map[string]bool{}
+	var intents []ToolIntent
+	for _, e := range pathTo(entries, s.leafLocked(entries)) {
+		if e.Type == TypeMessage && e.Message != nil && e.Message.Role == llm.RoleTool && e.Message.ToolCallID != "" {
+			answered[e.Message.ToolCallID] = true
+		}
+		if e.Type != TypeToolIntent {
+			continue
+		}
+		var in ToolIntent
+		if err := json.Unmarshal(e.Data, &in); err != nil {
+			return nil, err
+		}
+		intents = append(intents, in)
+	}
+	var pending []ToolIntent
+	for _, in := range intents {
+		if !answered[in.CallID] {
+			pending = append(pending, in)
+		}
+	}
+	return pending, nil
+}

runtime/session/tree.go

@@ -26,6 +26,7 @@ const (
 	TypeLabel               EntryType = "label"
 	TypeCustom              EntryType = "custom"
 	TypeSessionInfo         EntryType = "session_info"
+	TypeToolIntent          EntryType = "tool_intent"
 )
 
 // Entry is one node in the session tree. Files written before the tree

runtime/telemetry/telemetry.go

@@ -0,0 +1,112 @@
+// Package telemetry 记录 GenAI span。默认不采集提示词正文。
+package telemetry
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/hex"
+	"encoding/json"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"logging-system/logsys"
+)
+
+// Span 是一次 invoke_agent、chat 或 execute_tool。
+type Span struct {
+	Name    string
+	TraceID string
+	SpanID  string
+	Start   time.Time
+	End     time.Time
+	Attrs   map[string]string
+}
+
+// StartFunc 返回循环使用的追踪函数。设置了 OTEL_EXPORTER_OTLP_ENDPOINT 时，
+// 结束 span 后以 OTLP/HTTP JSON 上报，不引入新的依赖。
+func StartFunc(log *logsys.Logger) func(name string, attrs map[string]string) func() {
+	endpoint := strings.TrimRight(os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT"), "/")
+	return func(name string, attrs map[string]string) func() {
+		sp := Span{
+			Name: name, TraceID: newID(16), SpanID: newID(8),
+			Start: time.Now(), Attrs: publicAttrs(attrs),
+		}
+		return func() {
+			sp.End = time.Now()
+			if log != nil {
+				kvs := []any{"span", sp.Name, "trace_id", sp.TraceID, "span_id", sp.SpanID}
+				for k, v := range sp.Attrs {
+					kvs = append(kvs, k, v)
+				}
+				log.Info("genai span", kvs...)
+			}
+			if endpoint != "" {
+				_ = ExportOTLP(endpoint, sp)
+			}
+		}
+	}
+}
+
+// publicAttrs 丢掉提示词正文。调用方即使传入也不会进入 span。
+func publicAttrs(in map[string]string) map[string]string {
+	out := map[string]string{}
+	for k, v := range in {
+		if k == "prompt" || k == "messages" || k == "content" {
+			continue
+		}
+		out[k] = v
+	}
+	return out
+}
+
+// ExportOTLP 把一个 span POST 到端点的 /v1/traces。
+func ExportOTLP(endpoint string, sp Span) error {
+	endpoint = strings.TrimRight(endpoint, "/")
+	if !strings.HasSuffix(endpoint, "/v1/traces") {
+		endpoint += "/v1/traces"
+	}
+	body, err := json.Marshal(otlpBody(sp))
+	if err != nil {
+		return err
+	}
+	req, err := http.NewRequest(http.MethodPost, endpoint, bytes.NewReader(body))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	return nil
+}
+
+func otlpBody(sp Span) map[string]any {
+	var attrs []map[string]any
+	for k, v := range publicAttrs(sp.Attrs) {
+		attrs = append(attrs, map[string]any{"key": k, "value": map[string]any{"stringValue": v}})
+	}
+	return map[string]any{
+		"resourceSpans": []any{map[string]any{
+			"scopeSpans": []any{map[string]any{
+				"spans": []any{map[string]any{
+					"traceId":           sp.TraceID,
+					"spanId":            sp.SpanID,
+					"name":              sp.Name,
+					"startTimeUnixNano": sp.Start.UnixNano(),
+					"endTimeUnixNano":   sp.End.UnixNano(),
+					"attributes":        attrs,
+				}},
+			}},
+		}},
+	}
+}
+
+func newID(n int) string {
+	b := make([]byte, n)
+	_, _ = rand.Read(b)
+	return hex.EncodeToString(b)
+}

runtime/telemetry/telemetry_test.go

@@ -0,0 +1,42 @@
+package telemetry
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestSpanOmitsPromptAndUsesAgreedName(t *testing.T) {
+	var body string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/v1/traces" {
+			t.Errorf("path %s", r.URL.Path)
+		}
+		b, _ := io.ReadAll(r.Body)
+		body = string(b)
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer srv.Close()
+
+	sp := Span{
+		Name: "chat", TraceID: "abc", SpanID: "def",
+		Start: time.Unix(0, 0), End: time.Unix(1, 0),
+		Attrs: map[string]string{"model": "m", "prompt": "用户的秘密提示词"},
+	}
+	if err := ExportOTLP(srv.URL, sp); err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(body, `"name":"chat"`) {
+		t.Fatalf("span name missing: %s", body)
+	}
+	if strings.Contains(body, "用户的秘密提示词") || strings.Contains(body, "prompt") {
+		t.Fatalf("prompt leaked: %s", body)
+	}
+	got := publicAttrs(map[string]string{"tool": "read_file", "content": "全文"})
+	if _, ok := got["content"]; ok || got["tool"] != "read_file" {
+		t.Fatalf("%#v", got)
+	}
+}

runtime/tools/builtin.go

@@ -17,7 +17,8 @@ type readFile struct {
 	files *filestate.Tracker
 }
 
-func (t *readFile) Name() string { return "read_file" }
+func (t *readFile) Name() string   { return "read_file" }
+func (t *readFile) Replay() string { return ReplaySafe }
 func (t *readFile) Description() string {
 	return "Read a UTF-8 text file inside the workspace. Without offset/limit returns the whole file (truncated at 200 KiB); with offset/limit returns numbered lines from a 1-based offset."
 }
@@ -79,6 +80,7 @@ func (t *readFile) Execute(_ context.Context, args json.RawMessage) (Result, err
 type writeFile struct {
 	root  string
 	files *filestate.Tracker
+	mark  func(rel string, before []byte, existed bool, after []byte)
 }
 
 func (t *writeFile) Name() string { return "write_file" }
@@ -106,15 +108,20 @@ func (t *writeFile) Execute(_ context.Context, args json.RawMessage) (Result, er
 	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
 		return Result{Content: err.Error(), IsError: true}, nil
 	}
+	before, existed := fileBefore(path)
 	if err := atomicWriteFile(path, []byte(obj.Content), 0o644); err != nil {
 		return Result{Content: err.Error(), IsError: true}, nil
 	}
+	if t.mark != nil {
+		t.mark(obj.Path, before, existed, []byte(obj.Content))
+	}
 	return Result{Content: "wrote " + obj.Path}, nil
 }
 
 type editFile struct {
 	root  string
 	files *filestate.Tracker
+	mark  func(rel string, before []byte, existed bool, after []byte)
 }
 
 func (t *editFile) Name() string { return "edit_file" }
@@ -156,12 +163,16 @@ func (t *editFile) Execute(_ context.Context, args json.RawMessage) (Result, err
 	if err := atomicWriteFile(path, []byte(updated), 0o644); err != nil {
 		return Result{Content: err.Error(), IsError: true}, nil
 	}
+	if t.mark != nil {
+		t.mark(obj.Path, b, true, []byte(updated))
+	}
 	return Result{Content: "edited " + obj.Path}, nil
 }
 
 type listDir struct{ root string }
 
-func (t *listDir) Name() string { return "list_dir" }
+func (t *listDir) Name() string   { return "list_dir" }
+func (t *listDir) Replay() string { return ReplaySafe }
 func (t *listDir) Description() string {
 	return "List names in a workspace directory."
 }
@@ -194,7 +205,8 @@ func (t *listDir) Execute(_ context.Context, args json.RawMessage) (Result, erro
 
 type grepTool struct{ root string }
 
-func (t *grepTool) Name() string { return "grep" }
+func (t *grepTool) Name() string   { return "grep" }
+func (t *grepTool) Replay() string { return ReplaySafe }
 func (t *grepTool) Description() string {
 	return "Search workspace text files. Literal substring by default; regex=true switches to Go regexp, include filters file names (e.g. *.go), ignore_case folds case. Caps at 50 hits."
 }
@@ -284,6 +296,7 @@ func (t *grepTool) Execute(_ context.Context, args json.RawMessage) (Result, err
 type multiEditTool struct {
 	root  string
 	files *filestate.Tracker
+	mark  func(rel string, before []byte, existed bool, after []byte)
 }
 
 func (t *multiEditTool) Name() string { return "multi_edit" }
@@ -335,5 +348,16 @@ func (t *multiEditTool) Execute(_ context.Context, args json.RawMessage) (Result
 	if err := atomicWriteFile(path, []byte(text), 0o644); err != nil {
 		return Result{Content: err.Error(), IsError: true}, nil
 	}
+	if t.mark != nil {
+		t.mark(obj.Path, b, true, []byte(text))
+	}
 	return Result{Content: fmt.Sprintf("applied %d edits to %s", len(obj.Edits), obj.Path)}, nil
 }
+
+func fileBefore(path string) ([]byte, bool) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return nil, false
+	}
+	return b, true
+}

runtime/tools/checkpoint_hook_test.go

@@ -0,0 +1,42 @@
+package tools
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"agent-native/runtime/checkpoint"
+)
+
+func TestWriteAndEditRecordCheckpoints(t *testing.T) {
+	root := t.TempDir()
+	log, err := checkpoint.Open(filepath.Join(t.TempDir(), "cp.jsonl"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	reg := WorkspaceToolsCheckpointed(root, nil, log, func() string { return "m1" })
+	if reg.Execute(context.Background(), "write_file", []byte(`{"path":"a.txt","content":"one"}`)).IsError {
+		t.Fatal("write")
+	}
+	if reg.Execute(context.Background(), "edit_file", []byte(`{"path":"a.txt","old":"one","new":"two"}`)).IsError {
+		t.Fatal("edit")
+	}
+	if err := os.WriteFile(filepath.Join(root, "shell.txt"), []byte("nope"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	got, err := log.Rewind("m1", []string{"m1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got.Restored) != 1 || got.Restored[0] != "a.txt" {
+		t.Fatalf("restored %#v skipped %#v", got.Restored, got.Skipped)
+	}
+	if _, err := os.Stat(filepath.Join(root, "a.txt")); !os.IsNotExist(err) {
+		t.Fatal("created file was kept")
+	}
+	side, err := os.ReadFile(filepath.Join(root, "shell.txt"))
+	if err != nil || string(side) != "nope" {
+		t.Fatalf("shell file %q %v", side, err)
+	}
+}

runtime/tools/glob.go

@@ -15,7 +15,8 @@ const maxGlobResults = 500
 
 type globTool struct{ root string }
 
-func (t *globTool) Name() string { return "glob" }
+func (t *globTool) Name() string   { return "glob" }
+func (t *globTool) Replay() string { return ReplaySafe }
 
 func (t *globTool) Description() string {
 	return "Find workspace files matching a glob pattern (** crosses directories, * within one segment). Returns up to 500 relative paths."

runtime/tools/registry.go

@@ -9,6 +9,7 @@ import (
 	"sync"
 	"time"
 
+	"agent-native/runtime/checkpoint"
 	"agent-native/runtime/filestate"
 )
 
@@ -26,6 +27,26 @@ type Tool interface {
 	Execute(ctx context.Context, args json.RawMessage) (Result, error)
 }
 
+const (
+	// ReplaySafe 表示恢复时可以再执行一次。ReplayNever 是缺省，不重跑。
+	ReplaySafe  = "safe"
+	ReplayNever = "never"
+)
+
+// Replayer 是可选声明。未实现或返回其他值都按 never。
+type Replayer interface {
+	Replay() string
+}
+
+// ReplayOf 读取工具的重放声明。
+func ReplayOf(t Tool) string {
+	r, ok := t.(Replayer)
+	if !ok || r.Replay() != ReplaySafe {
+		return ReplayNever
+	}
+	return ReplaySafe
+}
+
 // BeforeHook can block a call after schema validation.
 type BeforeHook func(ctx context.Context, name string, args json.RawMessage) (block bool, reason string)
 
@@ -55,6 +76,18 @@ func (r *Registry) Has(name string) bool {
 	return ok
 }
 
+// Replay 返回已注册工具的重放声明。未知工具是 never。
+func (r *Registry) Replay(name string) string {
+	if r == nil {
+		return ReplayNever
+	}
+	t, ok := r.tools[name]
+	if !ok {
+		return ReplayNever
+	}
+	return ReplayOf(t)
+}
+
 func (r *Registry) Register(t Tool) {
 	if _, ok := r.tools[t.Name()]; !ok {
 		r.order = append(r.order, t.Name())
@@ -276,17 +309,36 @@ func WorkspaceTools(root string) *Registry {
 
 // WorkspaceToolsTracked 与 WorkspaceTools 相同，但改写已存在的文件前要先在本轮读过。
 func WorkspaceToolsTracked(root string, files *filestate.Tracker) *Registry {
+	return WorkspaceToolsCheckpointed(root, files, nil, nil)
+}
+
+// WorkspaceToolsCheckpointed 在写、改文件前把改前内容交给检查点。log 为空则不记录。
+func WorkspaceToolsCheckpointed(root string, files *filestate.Tracker, log *checkpoint.Log, anchor func() string) *Registry {
+	mark := writeMark(log, root, anchor)
 	r := NewRegistry(root)
 	r.Register(&readFile{root: root, files: files})
-	r.Register(&writeFile{root: root, files: files})
-	r.Register(&editFile{root: root, files: files})
-	r.Register(&multiEditTool{root: root, files: files})
+	r.Register(&writeFile{root: root, files: files, mark: mark})
+	r.Register(&editFile{root: root, files: files, mark: mark})
+	r.Register(&multiEditTool{root: root, files: files, mark: mark})
 	r.Register(&listDir{root: root})
 	r.Register(&grepTool{root: root})
 	r.Register(&globTool{root: root})
 	return r
 }
 
+func writeMark(log *checkpoint.Log, root string, anchor func() string) func(rel string, before []byte, existed bool, after []byte) {
+	if log == nil {
+		return nil
+	}
+	return func(rel string, before []byte, existed bool, after []byte) {
+		id := ""
+		if anchor != nil {
+			id = anchor()
+		}
+		_ = log.Record(id, root, rel, before, existed, after)
+	}
+}
+
 func rejectStaleWrite(files *filestate.Tracker, path string) string {
 	if files == nil {
 		return ""