diff --git a/backend/services/runtimelog/migration.go b/backend/services/runtimelog/migration.go
new file mode 100644
index 0000000..33267a5
--- /dev/null
+++ b/backend/services/runtimelog/migration.go
@@ -0,0 +1,155 @@
+package runtimelog
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+)
+
+const legacyDirectory = "运行日志"
+
+// migrateLegacyLogs 在日志写入和维护启动前迁移旧目录；不覆盖同名文件，不处理未知文件。
+func migrateLegacyLogs(root *os.Root) error {
+	info, err := root.Lstat(legacyDirectory)
+	if os.IsNotExist(err) {
+		return nil
+	}
+	if err != nil {
+		return err
+	}
+	if !info.IsDir() || info.Mode()&os.ModeSymlink != 0 {
+		return fmt.Errorf("旧运行日志目录必须是实际目录：%w", ErrInvalid)
+	}
+	legacy, err := root.OpenRoot(legacyDirectory)
+	if err != nil {
+		return err
+	}
+	defer legacy.Close()
+	directory, err := legacy.Open(".")
+	if err != nil {
+		return err
+	}
+	opened, statErr := directory.Stat()
+	entries, readErr := directory.ReadDir(-1)
+	if err := errors.Join(statErr, readErr, directory.Close()); err != nil {
+		return err
+	}
+	if !os.SameFile(info, opened) {
+		return fmt.Errorf("旧运行日志目录在迁移前发生变化：%w", ErrInvalid)
+	}
+	type sourceFile struct {
+		name string
+		info os.FileInfo
+	}
+	var sources []sourceFile
+	unknown := false
+	// 先检查全部源文件和目标，不能迁移到一半才发现已有同名日志。
+	for _, entry := range entries {
+		name := entry.Name()
+		if _, ok := fileDay(name); !ok {
+			unknown = true
+			continue
+		}
+		source, err := legacy.Lstat(name)
+		if err != nil {
+			return err
+		}
+		if !source.Mode().IsRegular() {
+			return fmt.Errorf("旧运行日志不是普通文件 %s：%w", name, ErrInvalid)
+		}
+		if _, err := root.Lstat(name); err == nil {
+			return fmt.Errorf("运行日志迁移目标已存在，请核对两个目录的同名文件，拒绝覆盖：%s", name)
+		} else if !os.IsNotExist(err) {
+			return err
+		}
+		sources = append(sources, sourceFile{name: name, info: source})
+	}
+	for _, source := range sources {
+		if err := moveLegacyLog(legacy, root, source.name, source.info); err != nil {
+			return fmt.Errorf("运行日志迁移失败，未完成的源文件已保留 %s：%w", source.name, err)
+		}
+	}
+	if unknown {
+		return nil
+	}
+	if err := legacy.Close(); err != nil {
+		return err
+	}
+	current, err := root.Lstat(legacyDirectory)
+	if err != nil {
+		return err
+	}
+	if !os.SameFile(info, current) || !current.IsDir() || current.Mode()&os.ModeSymlink != 0 {
+		return fmt.Errorf("旧运行日志目录在迁移时发生变化：%w", ErrInvalid)
+	}
+	// 只移除迁移后的空目录；新出现的文件会使移除失败，绝不递归删除。
+	return root.Remove(legacyDirectory)
+}
+
+// moveLegacyLog 使用排他创建和流式复制，兼容不支持硬链接的文件系统。
+func moveLegacyLog(legacy, root *os.Root, name string, expected os.FileInfo) error {
+	source, err := legacy.Open(name)
+	if err != nil {
+		return err
+	}
+	defer source.Close()
+	opened, err := source.Stat()
+	if err != nil {
+		return err
+	}
+	if !unchangedLog(expected, opened) {
+		return ErrInvalid
+	}
+	target, err := root.OpenFile(name, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0600)
+	if err != nil {
+		return err
+	}
+	created, err := target.Stat()
+	complete := false
+	defer func() {
+		_ = target.Close()
+		// 只清理本次创建且尚未复制完成的目标；中断或异常时源文件仍然存在。
+		if !complete && created != nil {
+			if current, err := root.Lstat(name); err == nil && os.SameFile(created, current) {
+				_ = root.Remove(name)
+			}
+		}
+	}()
+	if err != nil {
+		return err
+	}
+	written, copyErr := io.Copy(target, source)
+	after, statErr := source.Stat()
+	if err := errors.Join(copyErr, statErr, target.Sync(), target.Close(), source.Close()); err != nil {
+		return err
+	}
+	if written != expected.Size() || !unchangedLog(expected, after) {
+		return fmt.Errorf("源日志在复制时发生变化：%w", ErrInvalid)
+	}
+	if err := root.Chtimes(name, expected.ModTime(), expected.ModTime()); err != nil {
+		return err
+	}
+	current, err := legacy.Lstat(name)
+	if err != nil {
+		return err
+	}
+	if !unchangedLog(expected, current) {
+		return fmt.Errorf("源日志在迁移时发生变化：%w", ErrInvalid)
+	}
+	destination, err := root.Lstat(name)
+	if err != nil {
+		return err
+	}
+	if !destination.Mode().IsRegular() || !os.SameFile(created, destination) || destination.Size() != written {
+		return fmt.Errorf("目标日志在迁移时发生变化：%w", ErrInvalid)
+	}
+	// 目标已完整落盘；删除源失败时保留两份，重启明确报冲突，不猜测应保留哪份。
+	complete = true
+	return legacy.Remove(name)
+}
+
+func unchangedLog(expected, current os.FileInfo) bool {
+	return current.Mode().IsRegular() && os.SameFile(expected, current) &&
+		expected.Size() == current.Size() && expected.ModTime().Equal(current.ModTime())
+}
diff --git a/backend/services/runtimelog/writer.go b/backend/services/runtimelog/writer.go
index b602027..9b6d2fd 100644
--- a/backend/services/runtimelog/writer.go
+++ b/backend/services/runtimelog/writer.go
@@ -42,14 +42,13 @@ func New(root string) (*Writer, error) {
 	if err != nil {
 		return nil, err
 	}
-	directory, err = runtimepath.SecureDirectory(directory, "运行日志")
-	if err != nil {
-		return nil, err
-	}
 	handle, err := os.OpenRoot(directory)
 	if err != nil {
 		return nil, err
 	}
+	if err := migrateLegacyLogs(handle); err != nil {
+		return nil, errors.Join(err, handle.Close())
+	}
 	return &Writer{root: handle, now: time.Now}, nil
 }
 
diff --git a/docs/日志改造任务.md b/docs/日志改造任务.md
index 3cb7601..270a7ec 100644
--- a/docs/日志改造任务.md
+++ b/docs/日志改造任务.md
@@ -1,10 +1,21 @@
 # 日志存储与可视化改造
 
+## 2026-09-09 运行日志目录简化
+
+- [✓] 已确认：保留顶层 `log/`，取消 `log/运行日志/` 这一层；修改前检查点 `3d8d1c8` 已推送。
+- [x] 已完成，等待复审：新部署直接写入 `log/runtime-YYYY-MM-DD.log`，压缩文件也直接保存在 `log/`。
+- [x] 已完成，等待复审：启动写入和维护之前自动迁移旧目录的受管日志；预检同名冲突，排他创建目标，流式复制完整落盘后才移除源文件，保留内容与修改时间。
+- [x] 已完成，等待复审：仅移除迁移后的空目录；未知文件、旧审计文件和启动诊断不动。迁移期间必须停止旧服务；遇到同名冲突（包括异常中断残留）保留现场并明确报错，需人工核对，不自动覆盖或合并。
+- [✓] 复审通过：新部署、旧文件及压缩文件迁移、重复启动、空目录、同日两种格式、同名冲突、源文件变化和原有日志保留策略回归。
+- [!] 验证限制：Windows 普通权限不能创建符号链接，目标链接、旧目录链接和源文件链接三个测试分支跳过；拒绝链接逻辑已实现，不声明这些分支已实测通过。
+- [✓] 全量回归：`test-log/run-2026-09-08T16-12-55-458Z-37964`，前端 149 项、部署 4 项和后端全包通过；测试使用独立临时目录，不清空现有账号或邮件。
+- [~] 进行中：全量构建部署到 `yunx-test`、重启以及 MCP 日志列表和详情验收。
+
 ## 已确认需求
 
 - 操作记录、配置审计、收发信记录兼容 SQLite、MySQL、PostgreSQL，默认沿用当前业务数据库连接，不要求额外安装 MySQL，不自动迁移业务数据库。
 - 设置导航在插件配置后增加日志入口，支持分类、时间筛选、分页与详情。
-- 运行日志保存在 `log/运行日志`，按天写入；满七天的日文件压缩为独立的 `.log.gz`，启动补做，避免整周归档跨越清理边界。
+- 运行日志直接保存在 `log/`，按天写入；满七天的日文件压缩为独立的 `.log.gz`，启动补做，避免整周归档跨越清理边界。
 - 压缩后的运行日志仍可在后台查看；仅在压缩校验通过后替换对应明文文件。
 - 配置审计展示操作者、时间、具体字段及修改前后值；秘密只显示配置状态。
 - 旧配置审计幂等迁移并保留原文件，不伪造历史缺失的变更详情。
diff --git a/test/backend/app_runtime_log_test.go b/test/backend/app_runtime_log_test.go
index c56ac97..0688487 100644
--- a/test/backend/app_runtime_log_test.go
+++ b/test/backend/app_runtime_log_test.go
@@ -31,7 +31,7 @@ func TestFatalErrorIsLoggedBeforeRuntimeClose(t *testing.T) {
 		if err == nil || !strings.Contains(err.Error(), "fatal-probe") {
 			t.Fatalf("fatal error lost: %v", err)
 		}
-		files, err := filepath.Glob(filepath.Join(root, "log", "运行日志", "runtime-*.log"))
+		files, err := filepath.Glob(filepath.Join(root, "log", "runtime-*.log"))
 		if err != nil || len(files) != 1 {
 			t.Fatalf("missing runtime log: %v", err)
 		}
diff --git a/test/backend/runtime_log_migration_test.go b/test/backend/runtime_log_migration_test.go
new file mode 100644
index 0000000..90fa0e5
--- /dev/null
+++ b/test/backend/runtime_log_migration_test.go
@@ -0,0 +1,320 @@
+package runtimelog
+
+import (
+	"bytes"
+	"compress/gzip"
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+func writeMigrationFile(t *testing.T, path string, data []byte) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0700); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(path, data, 0600); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestRuntimeLogFlatDirectoryAndLegacyMigration(t *testing.T) {
+	for _, upgrade := range []bool{false, true} {
+		t.Run(map[bool]string{false: "fresh", true: "upgrade"}[upgrade], func(t *testing.T) {
+			root := t.TempDir()
+			directory := filepath.Join(root, "log")
+			old := filepath.Join(directory, legacyDirectory)
+			now := time.Now().UTC()
+			name := prefix + now.Format("2006-01-02") + ".log"
+			archivedAt := now.Add(-9 * 24 * time.Hour)
+			archived := prefix + archivedAt.Format("2006-01-02") + ".log.gz"
+			line := "[" + now.Format(time.RFC3339Nano) + "] 迁移前的运行日志\n"
+			var compressed bytes.Buffer
+			archive := gzip.NewWriter(&compressed)
+			if _, err := archive.Write([]byte("[" + archivedAt.Format(time.RFC3339Nano) + "] 压缩记录\n")); err != nil {
+				t.Fatal(err)
+			}
+			if err := archive.Close(); err != nil {
+				t.Fatal(err)
+			}
+			var modified time.Time
+			if upgrade {
+				writeMigrationFile(t, filepath.Join(old, name), []byte(line))
+				writeMigrationFile(t, filepath.Join(old, archived), compressed.Bytes())
+				if err := os.Chtimes(filepath.Join(old, archived), archivedAt, archivedAt); err != nil {
+					t.Fatal(err)
+				}
+				info, err := os.Stat(filepath.Join(old, archived))
+				if err != nil {
+					t.Fatal(err)
+				}
+				modified = info.ModTime()
+			}
+			// 重复启动不重新创建旧目录，迁移后的当前日志仍可追加。
+			for attempt := 0; attempt < 2; attempt++ {
+				w, err := New(root)
+				if err != nil {
+					t.Fatal(err)
+				}
+				defer w.Close()
+				w.now = func() time.Time { return now }
+				if _, err := os.Lstat(old); !os.IsNotExist(err) {
+					t.Fatalf("legacy directory exists: %v", err)
+				}
+				if upgrade {
+					data, err := os.ReadFile(filepath.Join(directory, archived))
+					if err != nil || !bytes.Equal(data, compressed.Bytes()) {
+						t.Fatalf("archive changed: %v", err)
+					}
+					info, err := os.Stat(filepath.Join(directory, archived))
+					if err != nil || !modified.Equal(info.ModTime()) {
+						t.Fatalf("archive time changed: %v", err)
+					}
+					page, err := w.Read(context.Background(), archived, 0, 100)
+					if err != nil || len(page.Lines) != 1 || !strings.Contains(page.Lines[0], "压缩记录") {
+						t.Fatalf("archive query: %+v %v", page, err)
+					}
+				}
+				if err := w.WriteAt(now, "迁移后的日志"); err != nil {
+					t.Fatal(err)
+				}
+				if err := w.Maintain(context.Background(), now); err != nil {
+					t.Fatal(err)
+				}
+				files, err := w.Files()
+				if err != nil || len(files) != map[bool]int{false: 1, true: 2}[upgrade] {
+					t.Fatalf("files: %+v %v", files, err)
+				}
+				if err := w.Close(); err != nil {
+					t.Fatal(err)
+				}
+				data, err := os.ReadFile(filepath.Join(directory, name))
+				if err != nil || (upgrade && !bytes.HasPrefix(data, []byte(line))) {
+					t.Fatalf("original log prefix lost: %v", err)
+				}
+			}
+		})
+	}
+}
+
+func TestRuntimeLogMigrationPreflightPreservesConflicts(t *testing.T) {
+	for _, kind := range []string{"different", "identical", "directory", "symlink"} {
+		t.Run(kind, func(t *testing.T) {
+			root := t.TempDir()
+			directory := filepath.Join(root, "log")
+			old := filepath.Join(directory, legacyDirectory)
+			first, conflict := "runtime-2026-09-07.log", "runtime-2026-09-08.log"
+			for _, name := range []string{first, conflict} {
+				writeMigrationFile(t, filepath.Join(old, name), []byte("original"))
+			}
+			target := filepath.Join(directory, conflict)
+			switch kind {
+			case "directory":
+				if err := os.Mkdir(target, 0700); err != nil {
+					t.Fatal(err)
+				}
+			case "symlink":
+				if err := os.Symlink(filepath.Join(old, conflict), target); err != nil {
+					t.Skipf("symlink unavailable: %v", err)
+				}
+			default:
+				data := "conflicting"
+				if kind == "identical" {
+					data = "original"
+				}
+				writeMigrationFile(t, target, []byte(data))
+			}
+			before, err := os.Lstat(target)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if w, err := New(root); err == nil {
+				w.Close()
+				t.Fatal("conflict accepted")
+			}
+			for _, name := range []string{first, conflict} {
+				data, err := os.ReadFile(filepath.Join(old, name))
+				if err != nil || string(data) != "original" {
+					t.Fatalf("source changed: %v", err)
+				}
+			}
+			if _, err := os.Lstat(filepath.Join(directory, first)); !os.IsNotExist(err) {
+				t.Fatal("preflight moved a file before detecting conflict")
+			}
+			after, err := os.Lstat(target)
+			if err != nil || !os.SameFile(before, after) || before.Size() != after.Size() || !before.ModTime().Equal(after.ModTime()) {
+				t.Fatalf("target changed: %v", err)
+			}
+		})
+	}
+}
+
+func TestRuntimeLogMigrationPreservesUnknownAndResumes(t *testing.T) {
+	root := t.TempDir()
+	directory := filepath.Join(root, "log")
+	old := filepath.Join(directory, legacyDirectory)
+	// 顶层文件模拟前一次已完成的迁移，损坏归档只搬运，不在迁移阶段改写或删除。
+	files := map[string]string{
+		filepath.Join(directory, "runtime-2026-09-07.log"): "already migrated",
+		filepath.Join(directory, "config-audit-v2.jsonl"):  "historical audit",
+		filepath.Join(old, "runtime-2026-09-08.log.gz"):    "damaged archive",
+		filepath.Join(old, "runtime-2026-99-99.log"):       "unknown name",
+		filepath.Join(old, "manual", "notes.log"):          "manual notes",
+	}
+	for path, content := range files {
+		writeMigrationFile(t, path, []byte(content))
+	}
+	for attempt := 0; attempt < 2; attempt++ {
+		w, err := New(root)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := w.Close(); err != nil {
+			t.Fatal(err)
+		}
+	}
+	for path, content := range files {
+		if filepath.Base(path) == "runtime-2026-09-08.log.gz" {
+			if _, err := os.Lstat(path); !os.IsNotExist(err) {
+				t.Fatal("migrated source remains")
+			}
+			path = filepath.Join(directory, filepath.Base(path))
+		}
+		data, err := os.ReadFile(path)
+		if err != nil || string(data) != content {
+			t.Fatalf("evidence changed %s: %v", path, err)
+		}
+	}
+}
+
+func TestRuntimeLogMigrationRejectsUnsafeSource(t *testing.T) {
+	for _, kind := range []string{"legacy-file", "legacy-link", "entry-directory", "entry-link"} {
+		t.Run(kind, func(t *testing.T) {
+			root := t.TempDir()
+			directory := filepath.Join(root, "log")
+			old := filepath.Join(directory, legacyDirectory)
+			outside := t.TempDir()
+			if err := os.MkdirAll(directory, 0700); err != nil {
+				t.Fatal(err)
+			}
+			name := "runtime-2026-09-08.log"
+			writeMigrationFile(t, filepath.Join(outside, name), []byte("outside evidence"))
+			switch kind {
+			case "legacy-file":
+				writeMigrationFile(t, old, []byte("not a directory"))
+			case "legacy-link":
+				if err := os.Symlink(outside, old); err != nil {
+					t.Skipf("symlink unavailable: %v", err)
+				}
+			default:
+				if err := os.Mkdir(old, 0700); err != nil {
+					t.Fatal(err)
+				}
+				if kind == "entry-directory" {
+					if err := os.Mkdir(filepath.Join(old, name), 0700); err != nil {
+						t.Fatal(err)
+					}
+				} else if err := os.Symlink(filepath.Join(outside, name), filepath.Join(old, name)); err != nil {
+					t.Skipf("symlink unavailable: %v", err)
+				}
+			}
+			if w, err := New(root); err == nil {
+				w.Close()
+				t.Fatal("unsafe source accepted")
+			}
+			data, err := os.ReadFile(filepath.Join(outside, name))
+			if err != nil || string(data) != "outside evidence" {
+				t.Fatalf("outside file changed: %v", err)
+			}
+			if _, err := os.Lstat(filepath.Join(directory, name)); !os.IsNotExist(err) {
+				t.Fatal("unsafe source copied")
+			}
+		})
+	}
+}
+
+func TestRuntimeLogMigrationCopyRechecksTargetAndSource(t *testing.T) {
+	for _, conflict := range []bool{false, true} {
+		t.Run(map[bool]string{false: "source-changed", true: "target-created"}[conflict], func(t *testing.T) {
+			directory := t.TempDir()
+			old := filepath.Join(directory, legacyDirectory)
+			name := "runtime-2026-09-08.log"
+			writeMigrationFile(t, filepath.Join(old, name), []byte("original"))
+			expected, err := os.Stat(filepath.Join(old, name))
+			if err != nil {
+				t.Fatal(err)
+			}
+			root, err := os.OpenRoot(directory)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer root.Close()
+			legacy, err := root.OpenRoot(legacyDirectory)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer legacy.Close()
+			if conflict {
+				writeMigrationFile(t, filepath.Join(directory, name), []byte("target evidence"))
+			} else {
+				writeMigrationFile(t, filepath.Join(old, name), []byte("changed source"))
+			}
+			if err := moveLegacyLog(legacy, root, name, expected); err == nil {
+				t.Fatal("changed migration input accepted")
+			}
+			data, err := os.ReadFile(filepath.Join(old, name))
+			want := map[bool]string{false: "changed source", true: "original"}[conflict]
+			if err != nil || string(data) != want {
+				t.Fatalf("source lost: %v", err)
+			}
+			if conflict {
+				data, err := os.ReadFile(filepath.Join(directory, name))
+				if err != nil || string(data) != "target evidence" {
+					t.Fatalf("target overwritten: %v", err)
+				}
+			} else if _, err := os.Lstat(filepath.Join(directory, name)); !os.IsNotExist(err) {
+				t.Fatal("unexpected destination")
+			}
+		})
+	}
+}
+
+func TestRuntimeLogMigrationEmptyDirectoryAndSameDayFormats(t *testing.T) {
+	for _, empty := range []bool{true, false} {
+		t.Run(map[bool]string{true: "empty", false: "same-day-formats"}[empty], func(t *testing.T) {
+			root := t.TempDir()
+			directory := filepath.Join(root, "log")
+			old := filepath.Join(directory, legacyDirectory)
+			if err := os.MkdirAll(old, 0700); err != nil {
+				t.Fatal(err)
+			}
+			files := map[string]string{}
+			if !empty {
+				files["runtime-2026-09-08.log"] = "plain evidence"
+				files["runtime-2026-09-08.log.gz"] = "compressed evidence"
+				for name, content := range files {
+					writeMigrationFile(t, filepath.Join(old, name), []byte(content))
+				}
+			}
+			w, err := New(root)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if err := w.Close(); err != nil {
+				t.Fatal(err)
+			}
+			if _, err := os.Lstat(old); !os.IsNotExist(err) {
+				t.Fatalf("empty legacy directory remains: %v", err)
+			}
+			for name, content := range files {
+				data, err := os.ReadFile(filepath.Join(directory, name))
+				if err != nil || string(data) != content {
+					t.Fatalf("same-day evidence changed: %v", err)
+				}
+			}
+		})
+	}
+}
diff --git a/test/backend/runtime_logs_test.go b/test/backend/runtime_logs_test.go
index 41bd0d4..b923651 100644
--- a/test/backend/runtime_logs_test.go
+++ b/test/backend/runtime_logs_test.go
@@ -76,7 +76,7 @@ func TestRuntimeLogCorruptionAndUnknownFilesArePreserved(t *testing.T) {
 	defer w.Close()
 	now := time.Now().UTC()
 	w.now = func() time.Time { return now }
-	directory := filepath.Join(root, "log", "运行日志")
+	directory := filepath.Join(root, "log")
 	name := prefix + now.Add(-40*24*time.Hour).Format("2006-01-02") + ".log.gz"
 	if err := os.WriteFile(filepath.Join(directory, name), []byte("broken"), 0600); err != nil {
 		t.Fatal(err)
diff --git a/test/run.mjs b/test/run.mjs
index 4e0474e..6af67ed 100644
--- a/test/run.mjs
+++ b/test/run.mjs
@@ -56,6 +56,7 @@ if ((suite === 'all' || suite === 'backend') && result === 0) {
     'backend/services/logstore/log_store_test.go': 'test/backend/log_store_test.go',
     'backend/services/logstore/log_store_integration_test.go': 'test/backend/log_store_integration_test.go',
     'backend/services/runtimelog/runtime_logs_test.go': 'test/backend/runtime_logs_test.go',
+    'backend/services/runtimelog/migration_test.go': 'test/backend/runtime_log_migration_test.go',
     'backend/db/migration/log_migration_test.go': 'test/backend/log_migration_test.go',
     'backend/config/audit_changes_test.go': 'test/backend/audit_changes_test.go',
     'backend/config/json_format_test.go': 'test/backend/json_format_test.go',