diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4d46a1ea..25dcd3f9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -458,15 +458,16 @@ jobs:
           PR_HEAD_SHA: ${{ github.event.pull_request.head.sha }}
         run: |
           set -eu
-          test "$(git rev-parse HEAD^1)" = "$PR_BASE_SHA" || {
-            echo "focused test merge first parent does not match event base" >&2
-            exit 1
-          }
           test "$(git rev-parse HEAD^2)" = "$PR_HEAD_SHA" || {
             echo "focused test merge second parent does not match event head" >&2
             exit 1
           }
-          echo "TEST_BASE_REF=$PR_BASE_SHA" >> "$GITHUB_ENV"
+          merge_base_sha="$(git rev-parse HEAD^1)"
+          git merge-base --is-ancestor "$PR_BASE_SHA" "$merge_base_sha" || {
+            echo "focused test merge base is not a fast-forward of event base" >&2
+            exit 1
+          }
+          echo "TEST_BASE_REF=$merge_base_sha" >> "$GITHUB_ENV"
           echo "TEST_HEAD_REF=$(git rev-parse HEAD)" >> "$GITHUB_ENV"
 
       - name: Set up Go
@@ -1255,26 +1256,27 @@ jobs:
           PR_HEAD_SHA: ${{ github.event.pull_request.head.sha }}
         run: |
           set -eu
-          test "$(git rev-parse HEAD^1)" = "$PR_BASE_SHA" || {
-            echo "checked-out merge first parent does not match event base" >&2
-            exit 1
-          }
           test "$(git rev-parse HEAD^2)" = "$PR_HEAD_SHA" || {
             echo "checked-out merge second parent does not match event head" >&2
             exit 1
           }
+          merge_base_sha="$(git rev-parse HEAD^1)"
+          git merge-base --is-ancestor "$PR_BASE_SHA" "$merge_base_sha" || {
+            echo "checked-out merge base is not a fast-forward of event base" >&2
+            exit 1
+          }
+          echo "POLICY_BASE_SHA=$merge_base_sha" >> "$GITHUB_ENV"
 
       - name: Validate changed CHANGELOG content
         if: github.event_name == 'pull_request'
         env:
           CLASSIFIED_CHANGELOG_CHANGED: ${{ needs.lint.outputs.changelog_changed }}
           CHANGELOG_ONLY: ${{ needs.lint.outputs.changelog_only }}
-          PR_BASE_SHA: ${{ github.event.pull_request.base.sha }}
         run: |
           set -eu
           merge_changelog_changed=false
           if git diff --no-ext-diff --find-renames --name-status \
-            "$PR_BASE_SHA" HEAD |
+            "$POLICY_BASE_SHA" HEAD |
             awk -F '\t' '
               {
                 for (field = 2; field <= NF; field++) {
@@ -1299,7 +1301,7 @@ jobs:
             mode=--fast-path
           fi
           ./scripts/policy/check-changelog-pr.sh \
-            "$mode" "$PR_BASE_SHA" HEAD
+            "$mode" "$POLICY_BASE_SHA" HEAD
 
       - name: Validate trusted main CHANGELOG-only push
         if: github.event_name == 'push' && needs.lint.outputs.changelog_only == 'true'
@@ -1324,13 +1326,12 @@ jobs:
       - name: Validate scoped policy
         if: ${{ needs.lint.outputs.changelog_only != 'true' && (needs.lint.outputs.docs_only == 'true' || (needs.lint.outputs.full_suite != 'true' && needs.lint.outputs.interface_sensitive != 'true')) }}
         env:
-          PR_BASE_SHA: ${{ github.event.pull_request.base.sha }}
           PUSH_BEFORE_SHA: ${{ github.event.before }}
         run: |
           set -eu
           base_ref="$PUSH_BEFORE_SHA"
           if [ "$GITHUB_EVENT_NAME" = "pull_request" ]; then
-            base_ref="$PR_BASE_SHA"
+            base_ref="$POLICY_BASE_SHA"
           fi
           git rev-parse --verify "${base_ref}^{commit}" >/dev/null
           git diff --check "$base_ref" HEAD
diff --git a/README.md b/README.md
index 1ae82893..b861cd07 100644
--- a/README.md
+++ b/README.md
@@ -432,7 +432,7 @@ DWS_SKILL_SOURCE=/path/to/skills dws skill setup --mode multi
 | `--source` | path | Local source directory (overrides bundled skills) |
 | `--yes` | — | Scripting-only: skip the confirmation prompt. Removals are still backed up to `~/.dws/skill-backups/` first |
 
-> The setup command can remove the opposite-mode layout (`dws/` for multi, `dingtalk-*` for mono) and stale skills not in the bundle. Every removal is previewed before confirmation and preserved under `~/.dws/skill-backups/<timestamp>/`; a directory that cannot be backed up is never removed.
+> The setup command can remove the opposite-mode layout (`dws/` for multi, `dingtalk-*` for mono) and stale skills not in the bundle. Every removal is previewed before confirmation and preserved under `~/.dws/skill-backups/<timestamp>/`; a directory that cannot be backed up is never removed. In a non-interactive shell, setup refuses to migrate directories unless `--yes` is explicitly supplied after reviewing `--dry-run` output.
 
 Env vars: `DWS_SKILL_MODE=mono|multi` (also honored by `install.sh` / `install.ps1`), `DWS_SKILL_SOURCE=<path>`.
 
diff --git a/README_zh.md b/README_zh.md
index 5a906b19..fe2e92e9 100644
--- a/README_zh.md
+++ b/README_zh.md
@@ -426,7 +426,7 @@ DWS_SKILL_SOURCE=/path/to/skills dws skill setup --mode multi
 | `--source` | 路径 | 本地源目录（覆盖内置 skills） |
 | `--yes` | — | 仅供脚本使用：跳过确认提示。删除操作仍会先备份到 `~/.dws/skill-backups/` |
 
-> setup 命令可能移除对面模式残留（装 multi 删 `dws/`，装 mono 删 `dingtalk-*`）以及不在 bundle 内的过期 skill。所有删除都会先列入确认预览，并备份到 `~/.dws/skill-backups/<时间戳>/`；备份失败的目录会保留原样、绝不删除。
+> setup 命令可能移除对面模式残留（装 multi 删 `dws/`，装 mono 删 `dingtalk-*`）以及不在 bundle 内的过期 skill。所有删除都会先列入确认预览，并备份到 `~/.dws/skill-backups/<时间戳>/`；备份失败的目录会保留原样、绝不删除。非交互环境默认拒绝迁移目录；请先用 `--dry-run` 核对，再显式传入 `--yes`。
 
 环境变量：`DWS_SKILL_MODE=mono|multi`（`install.sh` / `install.ps1` 也认）、`DWS_SKILL_SOURCE=<路径>`。
 
diff --git a/build/npm/install.js b/build/npm/install.js
index 2e411130..2af4db9b 100755
--- a/build/npm/install.js
+++ b/build/npm/install.js
@@ -169,6 +169,7 @@ function copyChildren(srcDir, destDir) {
 function installSkillsToHomes(skillRoot) {
   const homeDir = os.homedir();
   let installed = 0;
+  let attempted = 0;
 
   AGENT_DIRS.forEach((agentDir, index) => {
     const baseDir = path.join(homeDir, agentDir);
@@ -176,6 +177,7 @@ function installSkillsToHomes(skillRoot) {
     if (index > 0 && !fs.existsSync(parentGate)) {
       return;
     }
+    attempted += 1;
     // Mutual exclusion: back up + remove multi leftovers before laying down
     // mono. Directories only — a stray file named dingtalk-x.md must survive.
     // Non-interactive installs cannot confirm, so removals stay reversible via
@@ -183,7 +185,10 @@ function installSkillsToHomes(skillRoot) {
     if (fs.existsSync(baseDir)) {
       for (const entry of fs.readdirSync(baseDir, { withFileTypes: true })) {
         if (entry.isDirectory() && (entry.name.startsWith("dingtalk-") || entry.name === "dws-shared")) {
-          backupAndRemoveSkillDir(homeDir, path.join(baseDir, entry.name));
+          if (!backupAndRemoveSkillDir(homeDir, path.join(baseDir, entry.name))) {
+            console.warn(`⚠️  跳过 ${baseDir}（multi 残留备份失败，未安装 mono）`);
+            return;
+          }
         }
       }
     }
@@ -192,15 +197,18 @@ function installSkillsToHomes(skillRoot) {
       // Refreshing an existing skill: on backup failure keep the user's
       // copy and skip this target.
       console.warn(`⚠️  跳过 ${destDir}（保留原目录）`);
-      installed += 1;
       return;
     }
     copyChildren(skillRoot, destDir);
     installed += 1;
   });
 
-  if (installed === 0) {
+  if (attempted === 0) {
     copyChildren(skillRoot, path.join(homeDir, ".agents", "skills", "dws"));
+    installed += 1;
+  }
+  if (installed === 0) {
+    console.warn("⚠️  未安装任何 mono Skill：所有检测到的 Agent 目标均失败");
   }
 }
 
@@ -234,31 +242,43 @@ function installMultiSkillsToHomes(multiRoot) {
   }
   const skillSet = new Set(skills);
   let installed = 0;
+  let attempted = 0;
 
   const installToBase = (baseDir) => {
     fs.mkdirSync(baseDir, { recursive: true });
     // Mutual exclusion: back up + remove the mono leftover, then stale multi
     // skills (dingtalk-* or dws-shared) not in the new bundle.
-    backupAndRemoveSkillDir(homeDir, path.join(baseDir, "dws"));
+    if (!backupAndRemoveSkillDir(homeDir, path.join(baseDir, "dws"))) {
+      console.warn(`⚠️  跳过 ${baseDir}（mono 残留备份失败，未安装 multi）`);
+      return false;
+    }
     for (const entry of fs.readdirSync(baseDir, { withFileTypes: true })) {
       if (
         entry.isDirectory() &&
         (entry.name.startsWith("dingtalk-") || entry.name === "dws-shared") &&
         !skillSet.has(entry.name)
       ) {
-        backupAndRemoveSkillDir(homeDir, path.join(baseDir, entry.name));
+        if (!backupAndRemoveSkillDir(homeDir, path.join(baseDir, entry.name))) {
+          console.warn(`⚠️  跳过 ${baseDir}（过期 Skill 备份失败，未安装 multi）`);
+          return false;
+        }
+      }
+    }
+    // Finish every potentially failing backup before copying the first new
+    // skill. This prevents a later backup failure from leaving a partial
+    // bundle in this Agent target.
+    for (const name of skills) {
+      const destDir = path.join(baseDir, name);
+      if (!backupAndRemoveSkillDir(homeDir, destDir)) {
+        console.warn(`⚠️  跳过 ${baseDir}（${name} 备份失败，未安装 multi）`);
+        return false;
       }
     }
     for (const name of skills) {
       const destDir = path.join(baseDir, name);
-      if (!backupAndRemoveSkillDir(homeDir, destDir)) {
-        // Refreshing an existing skill: on backup failure keep the user's
-        // copy and skip this skill.
-        console.warn(`⚠️  跳过 ${destDir}（保留原目录）`);
-        continue;
-      }
       copyChildren(path.join(multiRoot, name), destDir);
     }
+    return true;
   };
 
   AGENT_DIRS.forEach((agentDir, index) => {
@@ -267,12 +287,17 @@ function installMultiSkillsToHomes(multiRoot) {
     if (index > 0 && !fs.existsSync(parentGate)) {
       return;
     }
-    installToBase(baseDir);
-    installed += 1;
+    attempted += 1;
+    if (installToBase(baseDir)) {
+      installed += 1;
+    }
   });
 
+  if (attempted === 0 && installToBase(path.join(homeDir, ".agents", "skills"))) {
+    installed += 1;
+  }
   if (installed === 0) {
-    installToBase(path.join(homeDir, ".agents", "skills"));
+    console.warn("⚠️  未安装任何 multi Skill：所有检测到的 Agent 目标均失败");
   }
 }
 
diff --git a/internal/app/skill_setup.go b/internal/app/skill_setup.go
index 0b0e4efa..71593d16 100644
--- a/internal/app/skill_setup.go
+++ b/internal/app/skill_setup.go
@@ -587,7 +587,7 @@ func confirmSkillSetup(out io.Writer, mode, src string, dests []string, multiSki
 	}
 
 	if !skillSetupInteractive() {
-		return true, nil
+		return false, fmt.Errorf("非交互环境无法确认目录迁移；请先用 --dry-run 预览，确认后显式传入 --yes")
 	}
 
 	var confirm bool
@@ -646,35 +646,37 @@ func mutualExclusionVictims(dest, mode string) ([]string, error) {
 	return nil, nil
 }
 
-// cleanupMutualExclusion best-effort backs up + removes the opposite-mode
+// cleanupMutualExclusion backs up + removes the opposite-mode
 // leftovers. Removals are reversible: each victim is moved to
 // ~/.dws/skill-backups/<stamp>/ first (skillSetupBackupAndRemove), and a
 // victim whose backup fails is left in place with a warning instead of being
-// destroyed. Failures — including a failed victim scan — emit a warning to
-// errOut but never abort the install.
-func cleanupMutualExclusion(dest, mode string, out, errOut io.Writer) {
+// destroyed. A failure is returned so the caller skips the complete Agent
+// target and never installs both layouts together.
+func cleanupMutualExclusion(dest, mode string, out, errOut io.Writer) error {
 	victims, scanErr := mutualExclusionVictims(dest, mode)
 	if scanErr != nil {
-		fmt.Fprintf(errOut, "  ⚠️  互斥清理扫描失败（继续安装） %s: %v\n", dest, scanErr)
+		fmt.Fprintf(errOut, "  ⚠️  互斥清理扫描失败（跳过整个 Agent 目标） %s: %v\n", dest, scanErr)
+		return scanErr
 	}
 	if len(victims) == 0 {
-		return
+		return nil
 	}
 	home, homeErr := skillSetupUserHomeDir()
 	if homeErr != nil {
 		for _, victim := range victims {
 			fmt.Fprintf(errOut, "  ⚠️  无法解析 HOME，跳过删除（保留） %s: %v\n", victim, homeErr)
 		}
-		return
+		return homeErr
 	}
 	for _, victim := range victims {
 		backup, err := skillSetupBackupAndRemove(home, victim)
 		if err != nil {
-			fmt.Fprintf(errOut, "  ⚠️  互斥清理失败（保留原目录，继续安装） %s: %v\n", victim, err)
-			continue
+			fmt.Fprintf(errOut, "  ⚠️  互斥清理失败（保留原目录，跳过整个 Agent 目标） %s: %v\n", victim, err)
+			return err
 		}
 		fmt.Fprintf(out, "  × 已备份并清理对面模式残留 %s → %s\n", victim, backup)
 	}
+	return nil
 }
 
 func installSkillToHomes(src string, dests []string, out, errOut io.Writer) (installed, skipped int, err error) {
@@ -682,7 +684,11 @@ func installSkillToHomes(src string, dests []string, out, errOut io.Writer) (ins
 	sort.Strings(dests)
 	for _, dest := range dests {
 		// 先做互斥清理：装 mono 前先把同级 dingtalk-* 子目录全部备份移除
-		cleanupMutualExclusion(dest, skillSetupModeMono, out, errOut)
+		if cleanupErr := cleanupMutualExclusion(dest, skillSetupModeMono, out, errOut); cleanupErr != nil {
+			fmt.Fprintf(errOut, "  ✗ 互斥清理失败，跳过整个 Agent 目标 %s: %v\n", dest, cleanupErr)
+			skipped++
+			continue
+		}
 
 		// 刷新同名 dest 前先备份：已存在的 dws/ 可能带有用户修改，
 		// 直接 RemoveAll 会不可恢复。备份失败（含 HOME 解析失败）则保留
@@ -727,7 +733,11 @@ func installMultiSkillToHomes(src string, skillNames []string, dests []string, o
 	sort.Strings(dests)
 	for _, dest := range dests {
 		// 互斥清理：装 multi 前先把 dest/dws/ 整个备份移除（mono 残留）
-		cleanupMutualExclusion(dest, skillSetupModeMulti, out, errOut)
+		if cleanupErr := cleanupMutualExclusion(dest, skillSetupModeMulti, out, errOut); cleanupErr != nil {
+			fmt.Fprintf(errOut, "  ✗ 互斥清理失败，跳过整个 Agent 目标 %s: %v\n", dest, cleanupErr)
+			skipped += len(skillNames)
+			continue
+		}
 
 		if err := skillSetupMkdirAll(dest, 0o755); err != nil {
 			fmt.Fprintf(errOut, "  ✗ Agent 目录创建失败 %s: %v\n", dest, err)
@@ -736,24 +746,37 @@ func installMultiSkillToHomes(src string, skillNames []string, dests []string, o
 		}
 
 		if !filtered {
-			removeStaleMultiSkills(dest, skillNames, out, errOut)
+			if cleanupErr := removeStaleMultiSkills(dest, skillNames, out, errOut); cleanupErr != nil {
+				fmt.Fprintf(errOut, "  ✗ 过期 Skill 备份失败，跳过整个 Agent 目标 %s: %v\n", dest, cleanupErr)
+				skipped += len(skillNames)
+				continue
+			}
+		}
+
+		// Finish every destination backup before copying the first new Skill.
+		// Otherwise a later backup failure could leave a partial bundle.
+		backupFailed := false
+		for _, name := range skillNames {
+			subDest := filepath.Join(dest, name)
+			if homeErr != nil {
+				fmt.Fprintf(errOut, "  ✗ 无法解析 HOME，跳过整个 Agent 目标 %s: %v\n", dest, homeErr)
+				backupFailed = true
+				break
+			}
+			if _, backupErr := skillSetupBackupAndRemove(home, subDest); backupErr != nil {
+				fmt.Fprintf(errOut, "  ✗ 备份旧 Skill 失败，跳过整个 Agent 目标 %s: %v\n", dest, backupErr)
+				backupFailed = true
+				break
+			}
+		}
+		if backupFailed {
+			skipped += len(skillNames)
+			continue
 		}
 
 		for _, name := range skillNames {
 			subSrc := filepath.Join(src, name)
 			subDest := filepath.Join(dest, name)
-			// 刷新同名子 skill 前先备份（与 mono 路径一致），备份失败保留
-			// 原目录并跳过。
-			if homeErr != nil {
-				fmt.Fprintf(errOut, "  ✗ 无法解析 HOME，跳过刷新（保留原目录） %s: %v\n", subDest, homeErr)
-				skipped++
-				continue
-			}
-			if _, backupErr := skillSetupBackupAndRemove(home, subDest); backupErr != nil {
-				fmt.Fprintf(errOut, "  ✗ 备份旧 skill 失败（保留原目录） %s: %v\n", subDest, backupErr)
-				skipped++
-				continue
-			}
 			if err := skillSetupCopyDir(subSrc, subDest); err != nil {
 				fmt.Fprintf(errOut, "  ✗ 拷贝失败 %s: %v\n", subDest, err)
 				skipped++
@@ -798,15 +821,16 @@ func staleMultiSkillVictims(dest string, keep []string) []string {
 // directories under dest that are not part of the current bundle. Removal is
 // reversible: each stale directory is moved to ~/.dws/skill-backups/<stamp>/
 // first, and a backup failure keeps the directory in place with a warning.
-// Best-effort: scan/removal failures warn on errOut and never abort the
-// install.
-func removeStaleMultiSkills(dest string, keep []string, out, errOut io.Writer) {
+// A scan or backup failure is returned so callers do not write a new bundle
+// into a partially reconciled Agent target.
+func removeStaleMultiSkills(dest string, keep []string, out, errOut io.Writer) error {
 	entries, err := skillSetupReadDir(dest)
 	if err != nil {
-		if !errors.Is(err, os.ErrNotExist) {
-			fmt.Fprintf(errOut, "  ⚠️  过期 skill 扫描失败（继续安装） %s: %v\n", dest, err)
+		if errors.Is(err, os.ErrNotExist) {
+			return nil
 		}
-		return
+		fmt.Fprintf(errOut, "  ⚠️  过期 skill 扫描失败（跳过整个 Agent 目标） %s: %v\n", dest, err)
+		return err
 	}
 	keepSet := make(map[string]bool, len(keep))
 	for _, n := range keep {
@@ -823,23 +847,24 @@ func removeStaleMultiSkills(dest string, keep []string, out, errOut io.Writer) {
 		stales = append(stales, filepath.Join(dest, e.Name()))
 	}
 	if len(stales) == 0 {
-		return
+		return nil
 	}
 	home, homeErr := skillSetupUserHomeDir()
 	if homeErr != nil {
 		for _, stale := range stales {
 			fmt.Fprintf(errOut, "  ⚠️  无法解析 HOME，跳过删除（保留） %s: %v\n", stale, homeErr)
 		}
-		return
+		return homeErr
 	}
 	for _, stale := range stales {
 		backup, err := skillSetupBackupAndRemove(home, stale)
 		if err != nil {
-			fmt.Fprintf(errOut, "  ⚠️  过期 skill 清理失败（保留原目录，继续安装） %s: %v\n", stale, err)
-			continue
+			fmt.Fprintf(errOut, "  ⚠️  过期 skill 清理失败（保留原目录，跳过整个 Agent 目标） %s: %v\n", stale, err)
+			return err
 		}
 		fmt.Fprintf(out, "  × 已备份并清理过期 skill %s → %s\n", stale, backup)
 	}
+	return nil
 }
 
 func copyDir(src, dst string) error {
diff --git a/internal/app/skill_setup_cleanup_coverage_test.go b/internal/app/skill_setup_cleanup_coverage_test.go
index e2048823..e78802af 100644
--- a/internal/app/skill_setup_cleanup_coverage_test.go
+++ b/internal/app/skill_setup_cleanup_coverage_test.go
@@ -32,8 +32,8 @@ func TestCrossPlatformCoverageSkillSetupConfirmPreviewsStaleSkills(t *testing.T)
 
 	var out bytes.Buffer
 	ok, err := confirmSkillSetup(&out, skillSetupModeMulti, "src", []string{dest}, []string{"dingtalk-chat"}, false)
-	if err != nil || !ok {
-		t.Fatalf("confirmSkillSetup = (%v, %v), want (true, nil)", ok, err)
+	if err == nil || ok || !strings.Contains(err.Error(), "--yes") {
+		t.Fatalf("confirmSkillSetup = (%v, %v), want non-interactive confirmation error", ok, err)
 	}
 	if !strings.Contains(out.String(), "将备份并移除过期 skill") {
 		t.Fatalf("full install preview must list stale skills, got %q", out.String())
@@ -44,8 +44,8 @@ func TestCrossPlatformCoverageSkillSetupConfirmPreviewsStaleSkills(t *testing.T)
 
 	out.Reset()
 	ok, err = confirmSkillSetup(&out, skillSetupModeMulti, "src", []string{dest}, []string{"dingtalk-chat"}, true)
-	if err != nil || !ok {
-		t.Fatalf("filtered confirmSkillSetup = (%v, %v), want (true, nil)", ok, err)
+	if err == nil || ok {
+		t.Fatalf("filtered confirmSkillSetup = (%v, %v), want non-interactive confirmation error", ok, err)
 	}
 	if strings.Contains(out.String(), "将备份并移除过期 skill") {
 		t.Fatalf("filtered install must stay additive in the preview, got %q", out.String())
@@ -77,6 +77,75 @@ func TestCrossPlatformCoverageSkillSetupCleanupHomeFailure(t *testing.T) {
 	}
 }
 
+func TestCrossPlatformCoverageSkillSetupBackupFailureSkipsWholeTarget(t *testing.T) {
+	home := t.TempDir()
+	testseam.Swap(t, &skillSetupUserHomeDir, func() (string, error) { return home, nil })
+	copyCalls := 0
+	testseam.Swap(t, &skillSetupCopyDir, func(string, string) error {
+		copyCalls++
+		return nil
+	})
+	failure := errors.New("backup boom")
+	testseam.Swap(t, &skillSetupBackupAndRemove, func(_ string, dir string) (string, error) {
+		if filepath.Base(dir) == "dws" {
+			return "", failure
+		}
+		return "", nil
+	})
+
+	dest := filepath.Join(home, ".agents", "skills")
+	if err := os.MkdirAll(filepath.Join(dest, "dws"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	src := writeMultiSkillSource(t, []string{"dingtalk-a", "dingtalk-shared"})
+	var out, errOut bytes.Buffer
+	installed, skipped, err := installMultiSkillToHomes(src, []string{"dingtalk-a", "dingtalk-shared"}, []string{dest}, &out, &errOut, false)
+	if err != nil || installed != 0 || skipped != 2 {
+		t.Fatalf("install = (%d, %d, %v), want (0, 2, nil)", installed, skipped, err)
+	}
+	if copyCalls != 0 {
+		t.Fatalf("backup failure copied %d new Skills", copyCalls)
+	}
+	if !strings.Contains(errOut.String(), "跳过整个 Agent 目标") {
+		t.Fatalf("missing whole-target warning: %q", errOut.String())
+	}
+}
+
+func TestCrossPlatformCoverageSkillSetupStaleBackupFailureSkipsWholeTarget(t *testing.T) {
+	home := t.TempDir()
+	testseam.Swap(t, &skillSetupUserHomeDir, func() (string, error) { return home, nil })
+	copyCalls := 0
+	testseam.Swap(t, &skillSetupCopyDir, func(string, string) error {
+		copyCalls++
+		return nil
+	})
+	failure := errors.New("stale backup boom")
+	testseam.Swap(t, &skillSetupBackupAndRemove, func(_ string, dir string) (string, error) {
+		if filepath.Base(dir) == "dingtalk-stale" {
+			return "", failure
+		}
+		return "", nil
+	})
+
+	dest := filepath.Join(home, ".agents", "skills")
+	stale := filepath.Join(dest, "dingtalk-stale")
+	if err := os.MkdirAll(stale, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	src := writeMultiSkillSource(t, []string{"dingtalk-a", "dingtalk-shared"})
+	var out, errOut bytes.Buffer
+	installed, skipped, err := installMultiSkillToHomes(src, []string{"dingtalk-a", "dingtalk-shared"}, []string{dest}, &out, &errOut, false)
+	if err != nil || installed != 0 || skipped != 2 {
+		t.Fatalf("install = (%d, %d, %v), want (0, 2, nil)", installed, skipped, err)
+	}
+	if copyCalls != 0 {
+		t.Fatalf("stale backup failure copied %d new Skills", copyCalls)
+	}
+	if !strings.Contains(errOut.String(), "过期 Skill 备份失败，跳过整个 Agent 目标") {
+		t.Fatalf("missing stale whole-target warning: %q", errOut.String())
+	}
+}
+
 // TestCrossPlatformCoverageSkillSetupInstallHomeFailureSkips verifies both
 // install paths skip (never destroy) every target when $HOME cannot be
 // resolved for the pre-refresh backup.
@@ -117,7 +186,7 @@ func TestCrossPlatformCoverageSkillSetupInstallHomeFailureSkips(t *testing.T) {
 	if err != nil || installed != 0 || skipped != 1 {
 		t.Fatalf("multi install = (%d, %d, %v), want (0, 1, nil)", installed, skipped, err)
 	}
-	if !strings.Contains(errOut.String(), "无法解析 HOME，跳过刷新") {
+	if !strings.Contains(errOut.String(), "无法解析 HOME，跳过整个 Agent 目标") {
 		t.Fatalf("expected multi HOME skip warning, got %q", errOut.String())
 	}
 	if _, err := os.Stat(filepath.Join(multiDest, "dingtalk-a")); err != nil {
diff --git a/internal/app/skill_setup_test.go b/internal/app/skill_setup_test.go
index ba099b7c..08343b68 100644
--- a/internal/app/skill_setup_test.go
+++ b/internal/app/skill_setup_test.go
@@ -117,6 +117,72 @@ func TestCrossPlatformCoverageSkillSetupDeclinedConfirmationNeverRemoves(t *test
 	}
 }
 
+// TestCrossPlatformCoverageSkillSetupNonInteractiveRequiresYes pins the real
+// non-TTY safety boundary: an explicit mode alone is not consent to move
+// directories. The same command with --yes performs the previewed backup and
+// installation.
+func TestCrossPlatformCoverageSkillSetupNonInteractiveRequiresYes(t *testing.T) {
+	home := t.TempDir()
+	setTestHome(t, home)
+	oldInteractive := skillSetupInteractive
+	skillSetupInteractive = func() bool { return false }
+	t.Cleanup(func() { skillSetupInteractive = oldInteractive })
+
+	multiSrc := writeMultiSkillSource(t, []string{"dingtalk-aitable"})
+	agentHome := filepath.Join(home, ".claude", "skills")
+	mono := filepath.Join(agentHome, "dws")
+	if err := os.MkdirAll(mono, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(mono, "SKILL.md"), []byte("keep-me"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	run := func(extra ...string) error {
+		cmd := newSkillSetupCommand()
+		cmd.SetOut(io.Discard)
+		cmd.SetErr(io.Discard)
+		args := []string{"--mode", "multi", "--target", "claude", "--source", multiSrc}
+		cmd.SetArgs(append(args, extra...))
+		return cmd.Execute()
+	}
+
+	if err := run(); err == nil || !strings.Contains(err.Error(), "--yes") {
+		t.Fatalf("non-interactive setup error = %v, want explicit --yes requirement", err)
+	}
+	if data, err := os.ReadFile(filepath.Join(mono, "SKILL.md")); err != nil || string(data) != "keep-me" {
+		t.Fatalf("unconfirmed setup changed mono (data=%q, err=%v)", string(data), err)
+	}
+	if _, err := os.Stat(filepath.Join(agentHome, "dingtalk-aitable")); !os.IsNotExist(err) {
+		t.Fatalf("unconfirmed setup installed multi, stat err=%v", err)
+	}
+	if _, err := os.Stat(filepath.Join(home, ".dws", "skill-backups")); !os.IsNotExist(err) {
+		t.Fatalf("unconfirmed setup created backup state, stat err=%v", err)
+	}
+
+	if err := run("--yes"); err != nil {
+		t.Fatalf("explicitly confirmed setup failed: %v", err)
+	}
+	if _, err := os.Stat(mono); !os.IsNotExist(err) {
+		t.Fatalf("confirmed setup kept mono, stat err=%v", err)
+	}
+	if _, err := os.Stat(filepath.Join(agentHome, "dingtalk-aitable", "SKILL.md")); err != nil {
+		t.Fatalf("confirmed setup did not install multi: %v", err)
+	}
+	backupFound := false
+	_ = filepath.Walk(filepath.Join(home, ".dws", "skill-backups"), func(path string, info os.FileInfo, walkErr error) error {
+		if walkErr == nil && info != nil && !info.IsDir() && info.Name() == "SKILL.md" {
+			if data, readErr := os.ReadFile(path); readErr == nil && string(data) == "keep-me" {
+				backupFound = true
+			}
+		}
+		return nil
+	})
+	if !backupFound {
+		t.Fatal("confirmed setup did not back up mono")
+	}
+}
+
 func TestResolveSkillSetupModeFlagDirect(t *testing.T) {
 	got, err := resolveSkillSetupMode("mono", true, &bytes.Buffer{})
 	if err != nil || got != skillSetupModeMono {
diff --git a/internal/upgrade/paths.go b/internal/upgrade/paths.go
index 045470ab..f75cf2bd 100644
--- a/internal/upgrade/paths.go
+++ b/internal/upgrade/paths.go
@@ -413,6 +413,12 @@ func upgradeMultiSkillLocations(homeDir, multiRoot string, skills []string) (*Sk
 				failed = true
 				break
 			}
+		}
+		if failed {
+			continue
+		}
+		for _, name := range skills {
+			subDest := filepath.Join(destBase, name)
 			if err := upgradeCopyDir(filepath.Join(multiRoot, name), subDest); err != nil {
 				result.Results = append(result.Results, SkillDirResult{Dir: destBase, Status: SkillDirFailed, Err: err})
 				failed = true
@@ -437,6 +443,9 @@ func upgradeMultiSkillLocations(homeDir, multiRoot string, skills []string) (*Sk
 			if _, err := backupAndRemoveSkillDir(homeDir, subDest); err != nil {
 				return result, fmt.Errorf("所有技能目录安装失败，回退到主目录备份残留也失败: %w", err)
 			}
+		}
+		for _, name := range skills {
+			subDest := filepath.Join(destBase, name)
 			if err := upgradeCopyDir(filepath.Join(multiRoot, name), subDest); err != nil {
 				return result, fmt.Errorf("所有技能目录安装失败，回退到主目录也失败: %w", err)
 			}
diff --git a/scripts/install-skills.sh b/scripts/install-skills.sh
index 29e4d079..f524a370 100755
--- a/scripts/install-skills.sh
+++ b/scripts/install-skills.sh
@@ -156,7 +156,7 @@ _copy_skill_summary() {
   if [ -d "$_dest" ]; then
     backup_and_remove_skill_dir "$_dest" || {
       printf '  ⚠️  跳过 %s（保留原目录）\n' "$_dest"
-      return 0
+      return 1
     }
   fi
 
@@ -176,7 +176,7 @@ _copy_skill() {
   if [ -d "$_dest" ]; then
     backup_and_remove_skill_dir "$_dest" || {
       printf '  ⚠️  跳过 %s（保留原目录）\n' "$_dest"
-      return 0
+      return 1
     }
   fi
 
@@ -218,6 +218,7 @@ install_multi_skills_to_root() {
   multi_src="$1"
   root="$2"
   installed=0
+  attempted=0
   idx=0
   for agent_dir in \
     ".agents/skills" \
@@ -243,12 +244,19 @@ install_multi_skills_to_root() {
       idx=$((idx + 1))
       continue
     fi
-    _install_multi_to_base "$multi_src" "$base_dir" "$root" "$agent_dir"
-    installed=$((installed + 1))
+    attempted=$((attempted + 1))
+    if _install_multi_to_base "$multi_src" "$base_dir" "$root" "$agent_dir"; then
+      installed=$((installed + 1))
+    else
+      printf '  ⚠️  跳过 %s（备份失败，未安装 multi）\n' "$base_dir"
+    fi
     idx=$((idx + 1))
   done
+  if [ "$attempted" -eq 0 ] && _install_multi_to_base "$multi_src" "$root/.agents/skills" "$root" ".agents/skills"; then
+    installed=$((installed + 1))
+  fi
   if [ "$installed" -eq 0 ]; then
-    _install_multi_to_base "$multi_src" "$root/.agents/skills" "$root" ".agents/skills"
+    printf '  ⚠️  未安装任何 multi Skill：所有检测到的 Agent 目标均失败\n'
   fi
 }
 
@@ -258,10 +266,10 @@ _install_multi_to_base() {
   _root="$3"
   _agent_dir="$4"
 
-  mkdir -p "$_base"
+  mkdir -p "$_base" || return 1
 
   # Mutual exclusion: back up + remove the mono leftover.
-  backup_and_remove_skill_dir "$_base/$SKILL_NAME" || true
+  backup_and_remove_skill_dir "$_base/$SKILL_NAME" || return 1
 
   # Back up + remove stale multi skills (dingtalk-* or dws-shared) not in the
   # new bundle.
@@ -269,24 +277,28 @@ _install_multi_to_base() {
     [ -d "$existing" ] || continue
     _name="$(basename "$existing")"
     if [ ! -f "$_msrc/$_name/SKILL.md" ]; then
-      backup_and_remove_skill_dir "$existing" || true
+      backup_and_remove_skill_dir "$existing" || return 1
     fi
   done
   if [ -d "$_base/dws-shared" ] && [ ! -f "$_msrc/dws-shared/SKILL.md" ]; then
-    backup_and_remove_skill_dir "$_base/dws-shared" || true
+    backup_and_remove_skill_dir "$_base/dws-shared" || return 1
   fi
 
+  # Complete all backups before copying the first new skill so a later
+  # failure cannot leave a partial multi bundle in this Agent target.
+  for skill_dir in "$_msrc"/*/; do
+    [ -f "${skill_dir}SKILL.md" ] || continue
+    _name="$(basename "$skill_dir")"
+    _dest="$_base/$_name"
+    backup_and_remove_skill_dir "$_dest" || return 1
+  done
+
   _count=0
   for skill_dir in "$_msrc"/*/; do
     [ -f "${skill_dir}SKILL.md" ] || continue
     _name="$(basename "$skill_dir")"
     _dest="$_base/$_name"
-    if [ -d "$_dest" ]; then
-      # Refreshing an existing skill: back it up first; on backup failure
-      # keep the user's copy and skip this skill.
-      backup_and_remove_skill_dir "$_dest" || continue
-    fi
-    mkdir -p "$_dest"
+    mkdir -p "$_dest" || return 1
     cp -R "${skill_dir}." "$_dest/" 2>/dev/null || cp -r "${skill_dir}." "$_dest/"
     _count=$((_count + 1))
   done
@@ -304,6 +316,7 @@ install_skills_to_root() {
   skill_src="$1"
   root="$2"
   installed=0
+  attempted=0
   idx=0
   for agent_dir in \
     ".agents/skills" \
@@ -329,14 +342,29 @@ install_skills_to_root() {
       idx=$((idx + 1))
       continue
     fi
+    attempted=$((attempted + 1))
     # Mutual exclusion: back up + remove multi leftovers before laying down
     # mono. Non-interactive installs cannot confirm, so removals stay
     # reversible via ~/.dws/skill-backups/ (backup failure keeps the dir).
-    backup_and_remove_skill_dir "$base_dir/dws-shared" || true
+    cleanup_ok=1
+    backup_and_remove_skill_dir "$base_dir/dws-shared" || cleanup_ok=0
+    if [ "$cleanup_ok" -ne 1 ]; then
+      printf '  ⚠️  跳过 %s（multi 残留备份失败，未安装 mono）\n' "$base_dir"
+      idx=$((idx + 1))
+      continue
+    fi
     for existing in "$base_dir"/dingtalk-*/; do
       [ -d "$existing" ] || continue
-      backup_and_remove_skill_dir "$existing" || true
+      backup_and_remove_skill_dir "$existing" || {
+        cleanup_ok=0
+        break
+      }
     done
+    if [ "$cleanup_ok" -ne 1 ]; then
+      printf '  ⚠️  跳过 %s（multi 残留备份失败，未安装 mono）\n' "$base_dir"
+      idx=$((idx + 1))
+      continue
+    fi
     dest="$base_dir/$SKILL_NAME"
     if [ "$root" = "$HOME" ]; then
       label="~/$agent_dir/$SKILL_NAME"
@@ -344,20 +372,26 @@ install_skills_to_root() {
       label="$root/$agent_dir/$SKILL_NAME"
     fi
     if [ "$installed" -eq 0 ]; then
-      _copy_skill "$skill_src" "$dest" "$label"
-    else
-      _copy_skill_summary "$skill_src" "$dest" "$label"
+      if _copy_skill "$skill_src" "$dest" "$label"; then
+        installed=$((installed + 1))
+      fi
+    elif _copy_skill_summary "$skill_src" "$dest" "$label"; then
+      installed=$((installed + 1))
     fi
-    installed=$((installed + 1))
     idx=$((idx + 1))
   done
-  if [ "$installed" -eq 0 ]; then
+  if [ "$attempted" -eq 0 ]; then
     if [ "$root" = "$HOME" ]; then
       flabel="~/.agents/skills/$SKILL_NAME"
     else
       flabel="$root/.agents/skills/$SKILL_NAME"
     fi
-    _copy_skill "$skill_src" "$root/.agents/skills/$SKILL_NAME" "$flabel"
+    if _copy_skill "$skill_src" "$root/.agents/skills/$SKILL_NAME" "$flabel"; then
+      installed=$((installed + 1))
+    fi
+  fi
+  if [ "$installed" -eq 0 ]; then
+    printf '  ⚠️  未安装任何 mono Skill：所有检测到的 Agent 目标均失败\n'
   fi
 }
 
diff --git a/scripts/install.ps1 b/scripts/install.ps1
index c1021681..79064121 100644
--- a/scripts/install.ps1
+++ b/scripts/install.ps1
@@ -269,7 +269,7 @@ function Copy-SkillToDir {
     # the user's copy and skip this target.
     if (!(Backup-SkillDir -Dir $Dest)) {
         Write-Say "⚠️  跳过 $Dest（保留原目录）"
-        return
+        return $false
     }
 
     $fileCount = Copy-DirRecursive -Source $SkillSrc -Destination $Dest
@@ -284,6 +284,7 @@ function Copy-SkillToDir {
             Write-Say "   📄 $($_.Name)"
         }
     }
+    return $true
 }
 
 function Copy-SkillToDirSummary {
@@ -291,11 +292,12 @@ function Copy-SkillToDirSummary {
 
     if (!(Backup-SkillDir -Dir $Dest)) {
         Write-Say "⚠️  跳过 $Dest（保留原目录）"
-        return
+        return $false
     }
 
     $fileCount = Copy-DirRecursive -Source $SkillSrc -Destination $Dest
     Write-Say "✅ Skills → $Label ($fileCount files)"
+    return $true
 }
 
 function Resolve-SourceRoot {
@@ -515,6 +517,7 @@ function Install-SkillsToHomes {
     )
 
     $installed = 0
+    $attempted = 0
     for ($i = 0; $i -lt $AgentDirs.Count; $i++) {
         $agentDir = $AgentDirs[$i]
         $baseDir = Join-Path $Root $agentDir
@@ -522,13 +525,24 @@ function Install-SkillsToHomes {
         if ($i -gt 0 -and !(Test-Path $parentGate)) {
             continue
         }
+        $attempted++
         # Mutual exclusion: back up + remove multi leftovers before laying
         # down mono. Non-interactive installs cannot confirm, so removals
         # stay reversible via ~\.dws\skill-backups\ (backup failure keeps
         # the dir).
-        Backup-SkillDir -Dir (Join-Path $baseDir "dws-shared") | Out-Null
-        Get-ChildItem -Path $baseDir -Directory -Filter "dingtalk-*" -ErrorAction SilentlyContinue |
-            ForEach-Object { Backup-SkillDir -Dir $_.FullName | Out-Null }
+        $cleanupOK = Backup-SkillDir -Dir (Join-Path $baseDir "dws-shared")
+        if ($cleanupOK) {
+            foreach ($existing in Get-ChildItem -Path $baseDir -Directory -Filter "dingtalk-*" -ErrorAction SilentlyContinue) {
+                if (!(Backup-SkillDir -Dir $existing.FullName)) {
+                    $cleanupOK = $false
+                    break
+                }
+            }
+        }
+        if (!$cleanupOK) {
+            Write-Say "⚠️  跳过 $baseDir（multi 残留备份失败，未安装 mono）"
+            continue
+        }
         $dest = Join-Path $baseDir $SkillName
         if ($Root -eq $HOME) {
             $label = "~\$agentDir\$SkillName"
@@ -536,20 +550,27 @@ function Install-SkillsToHomes {
             $label = Join-Path $Root (Join-Path $agentDir $SkillName)
         }
         if ($installed -eq 0) {
-            Copy-SkillToDir -SkillSrc $SkillSrc -Dest $dest -Label $label
+            $copied = Copy-SkillToDir -SkillSrc $SkillSrc -Dest $dest -Label $label
         } else {
-            Copy-SkillToDirSummary -SkillSrc $SkillSrc -Dest $dest -Label $label
+            $copied = Copy-SkillToDirSummary -SkillSrc $SkillSrc -Dest $dest -Label $label
+        }
+        if ($copied) {
+            $installed++
         }
-        $installed++
     }
-    if ($installed -eq 0) {
+    if ($attempted -eq 0) {
         $fallback = Join-Path (Join-Path $Root ".agents\skills") $SkillName
         if ($Root -eq $HOME) {
             $flabel = "~\.agents\skills\$SkillName"
         } else {
             $flabel = Join-Path $Root (Join-Path ".agents\skills" $SkillName)
         }
-        Copy-SkillToDir -SkillSrc $SkillSrc -Dest $fallback -Label $flabel
+        if (Copy-SkillToDir -SkillSrc $SkillSrc -Dest $fallback -Label $flabel) {
+            $installed++
+        }
+    }
+    if ($installed -eq 0) {
+        Write-Say "⚠️  未安装任何 mono Skill：所有检测到的 Agent 目标均失败"
     }
 }
 
@@ -577,6 +598,7 @@ function Install-MultiSkillsToHomes {
     )
 
     $installed = 0
+    $attempted = 0
     for ($i = 0; $i -lt $AgentDirs.Count; $i++) {
         $agentDir = $AgentDirs[$i]
         $baseDir = Join-Path $Root $agentDir
@@ -584,11 +606,18 @@ function Install-MultiSkillsToHomes {
         if ($i -gt 0 -and !(Test-Path $parentGate)) {
             continue
         }
-        Install-MultiToBase -MultiSrc $MultiSrc -BaseDir $baseDir -Root $Root -AgentDir $agentDir
+        $attempted++
+        if (Install-MultiToBase -MultiSrc $MultiSrc -BaseDir $baseDir -Root $Root -AgentDir $agentDir) {
+            $installed++
+        } else {
+            Write-Say "⚠️  跳过 $baseDir（备份失败，未安装 multi）"
+        }
+    }
+    if ($attempted -eq 0 -and (Install-MultiToBase -MultiSrc $MultiSrc -BaseDir (Join-Path $Root ".agents\skills") -Root $Root -AgentDir ".agents\skills")) {
         $installed++
     }
     if ($installed -eq 0) {
-        Install-MultiToBase -MultiSrc $MultiSrc -BaseDir (Join-Path $Root ".agents\skills") -Root $Root -AgentDir ".agents\skills"
+        Write-Say "⚠️  未安装任何 multi Skill：所有检测到的 Agent 目标均失败"
     }
 }
 
@@ -605,30 +634,41 @@ function Install-MultiToBase {
     }
 
     # Mutual exclusion: back up + remove the mono leftover.
-    Backup-SkillDir -Dir (Join-Path $BaseDir $SkillName) | Out-Null
+    if (!(Backup-SkillDir -Dir (Join-Path $BaseDir $SkillName))) {
+        return $false
+    }
 
     # Back up + remove stale multi skills (dingtalk-* or dws-shared) not in
     # the new bundle.
-    Get-ChildItem -Path $BaseDir -Directory -Filter "dingtalk-*" -ErrorAction SilentlyContinue |
-        Where-Object { !(Test-Path (Join-Path (Join-Path $MultiSrc $_.Name) "SKILL.md")) } |
-        ForEach-Object { Backup-SkillDir -Dir $_.FullName | Out-Null }
+    foreach ($existing in Get-ChildItem -Path $BaseDir -Directory -Filter "dingtalk-*" -ErrorAction SilentlyContinue) {
+        if (!(Test-Path (Join-Path (Join-Path $MultiSrc $existing.Name) "SKILL.md")) -and
+            !(Backup-SkillDir -Dir $existing.FullName)) {
+            return $false
+        }
+    }
     if (!(Test-Path (Join-Path (Join-Path $MultiSrc "dws-shared") "SKILL.md"))) {
-        Backup-SkillDir -Dir (Join-Path $BaseDir "dws-shared") | Out-Null
+        if (!(Backup-SkillDir -Dir (Join-Path $BaseDir "dws-shared"))) {
+            return $false
+        }
+    }
+
+    $skillDirs = @(Get-ChildItem -Path $MultiSrc -Directory | Where-Object {
+        Test-Path (Join-Path $_.FullName "SKILL.md")
+    })
+    # Complete all backups before copying the first new skill, preventing a
+    # later failure from leaving a partial multi bundle in this Agent target.
+    foreach ($skillDir in $skillDirs) {
+        if (!(Backup-SkillDir -Dir (Join-Path $BaseDir $skillDir.Name))) {
+            return $false
+        }
     }
 
     $count = 0
-    Get-ChildItem -Path $MultiSrc -Directory | ForEach-Object {
-        $name = $_.Name
-        if (!(Test-Path (Join-Path $_.FullName "SKILL.md"))) { return }
+    foreach ($skillDir in $skillDirs) {
+        $name = $skillDir.Name
         $dest = Join-Path $BaseDir $name
-        if (!(Backup-SkillDir -Dir $dest)) {
-            # Refreshing an existing skill: on backup failure keep the
-            # user's copy and skip this skill.
-            Write-Say "⚠️  跳过 $dest（保留原目录）"
-            return
-        }
         New-Item -ItemType Directory -Path $dest -Force | Out-Null
-        Copy-DirRecursive -Source $_.FullName -Destination $dest | Out-Null
+        Copy-DirRecursive -Source $skillDir.FullName -Destination $dest | Out-Null
         $count++
     }
 
@@ -638,6 +678,7 @@ function Install-MultiToBase {
         $label = Join-Path $Root $AgentDir
     }
     Write-Say "✅ Skills → $label ($count product skills)"
+    return $true
 }
 
 # ── Install Binary from Source ───────────────────────────────────────────────
diff --git a/scripts/install.sh b/scripts/install.sh
index 61cabd5d..adfe0065 100755
--- a/scripts/install.sh
+++ b/scripts/install.sh
@@ -401,6 +401,7 @@ install_skills_to_homes() {
   skill_src="$1"
   root="${HOME}"
   installed=0
+  attempted=0
   idx=0
   for agent_dir in \
     ".agents/skills" \
@@ -426,14 +427,29 @@ install_skills_to_homes() {
       idx=$((idx + 1))
       continue
     fi
+    attempted=$((attempted + 1))
     # Mutual exclusion: back up + remove multi leftovers before laying down
     # mono. Non-interactive installs cannot confirm, so removals stay
     # reversible via ~/.dws/skill-backups/ (backup failure keeps the dir).
-    backup_and_remove_skill_dir "$base_dir/dws-shared" || true
+    cleanup_ok=1
+    backup_and_remove_skill_dir "$base_dir/dws-shared" || cleanup_ok=0
+    if [ "$cleanup_ok" -ne 1 ]; then
+      say "  ⚠️  跳过 ${base_dir}（multi 残留备份失败，未安装 mono）"
+      idx=$((idx + 1))
+      continue
+    fi
     for existing in "$base_dir"/dingtalk-*/; do
       [ -d "$existing" ] || continue
-      backup_and_remove_skill_dir "$existing" || true
+      backup_and_remove_skill_dir "$existing" || {
+        cleanup_ok=0
+        break
+      }
     done
+    if [ "$cleanup_ok" -ne 1 ]; then
+      say "  ⚠️  跳过 ${base_dir}（multi 残留备份失败，未安装 mono）"
+      idx=$((idx + 1))
+      continue
+    fi
     dest="$base_dir/$SKILL_NAME"
     case "$root" in
       "$HOME")
@@ -444,14 +460,15 @@ install_skills_to_homes() {
         ;;
     esac
     if [ "$installed" -eq 0 ]; then
-      _copy_skill "$skill_src" "$dest" "$label"
-    else
-      _copy_skill_summary "$skill_src" "$dest" "$label"
+      if _copy_skill "$skill_src" "$dest" "$label"; then
+        installed=$((installed + 1))
+      fi
+    elif _copy_skill_summary "$skill_src" "$dest" "$label"; then
+      installed=$((installed + 1))
     fi
-    installed=$((installed + 1))
     idx=$((idx + 1))
   done
-  if [ "$installed" -eq 0 ]; then
+  if [ "$attempted" -eq 0 ]; then
     case "$root" in
       "$HOME")
         flabel="~/.agents/skills/$SKILL_NAME"
@@ -460,7 +477,12 @@ install_skills_to_homes() {
         flabel="$root/.agents/skills/$SKILL_NAME"
         ;;
     esac
-    _copy_skill "$skill_src" "$root/.agents/skills/$SKILL_NAME" "$flabel"
+    if _copy_skill "$skill_src" "$root/.agents/skills/$SKILL_NAME" "$flabel"; then
+      installed=$((installed + 1))
+    fi
+  fi
+  if [ "$installed" -eq 0 ]; then
+    say "  ⚠️  未安装任何 mono Skill：所有检测到的 Agent 目标均失败"
   fi
 }
 
@@ -488,6 +510,7 @@ install_multi_skills_to_homes() {
   multi_src="$1"
   root="${HOME}"
   installed=0
+  attempted=0
   idx=0
   for agent_dir in \
     ".agents/skills" \
@@ -513,12 +536,19 @@ install_multi_skills_to_homes() {
       idx=$((idx + 1))
       continue
     fi
-    _install_multi_to_base "$multi_src" "$base_dir" "$root" "$agent_dir"
-    installed=$((installed + 1))
+    attempted=$((attempted + 1))
+    if _install_multi_to_base "$multi_src" "$base_dir" "$root" "$agent_dir"; then
+      installed=$((installed + 1))
+    else
+      say "  ⚠️  跳过 ${base_dir}（备份失败，未安装 multi）"
+    fi
     idx=$((idx + 1))
   done
+  if [ "$attempted" -eq 0 ] && _install_multi_to_base "$multi_src" "$root/.agents/skills" "$root" ".agents/skills"; then
+    installed=$((installed + 1))
+  fi
   if [ "$installed" -eq 0 ]; then
-    _install_multi_to_base "$multi_src" "$root/.agents/skills" "$root" ".agents/skills"
+    say "  ⚠️  未安装任何 multi Skill：所有检测到的 Agent 目标均失败"
   fi
 }
 
@@ -528,10 +558,10 @@ _install_multi_to_base() {
   _root="$3"
   _agent_dir="$4"
 
-  mkdir -p "$_base"
+  mkdir -p "$_base" || return 1
 
   # Mutual exclusion: back up + remove the mono leftover.
-  backup_and_remove_skill_dir "$_base/$SKILL_NAME" || true
+  backup_and_remove_skill_dir "$_base/$SKILL_NAME" || return 1
 
   # Back up + remove stale multi skills (dingtalk-* or dws-shared) not in the
   # new bundle.
@@ -539,24 +569,28 @@ _install_multi_to_base() {
     [ -d "$existing" ] || continue
     _name="$(basename "$existing")"
     if [ ! -f "$_msrc/$_name/SKILL.md" ]; then
-      backup_and_remove_skill_dir "$existing" || true
+      backup_and_remove_skill_dir "$existing" || return 1
     fi
   done
   if [ -d "$_base/dws-shared" ] && [ ! -f "$_msrc/dws-shared/SKILL.md" ]; then
-    backup_and_remove_skill_dir "$_base/dws-shared" || true
+    backup_and_remove_skill_dir "$_base/dws-shared" || return 1
   fi
 
+  # Complete all backups before copying the first new skill so a later
+  # failure cannot leave a partial multi bundle in this Agent target.
+  for skill_dir in "$_msrc"/*/; do
+    [ -f "${skill_dir}SKILL.md" ] || continue
+    _name="$(basename "$skill_dir")"
+    _dest="$_base/$_name"
+    backup_and_remove_skill_dir "$_dest" || return 1
+  done
+
   _count=0
   for skill_dir in "$_msrc"/*/; do
     [ -f "${skill_dir}SKILL.md" ] || continue
     _name="$(basename "$skill_dir")"
     _dest="$_base/$_name"
-    if [ -d "$_dest" ]; then
-      # Refreshing an existing skill: back it up first; on backup failure
-      # keep the user's copy and skip this skill.
-      backup_and_remove_skill_dir "$_dest" || continue
-    fi
-    mkdir -p "$_dest"
+    mkdir -p "$_dest" || return 1
     cp -R "${skill_dir}." "$_dest/" 2>/dev/null || cp -r "${skill_dir}." "$_dest/"
     _count=$((_count + 1))
   done
@@ -577,7 +611,7 @@ _copy_skill_summary() {
   if [ -d "$_dest" ]; then
     backup_and_remove_skill_dir "$_dest" || {
       say "  ⚠️  跳过 ${_dest}（保留原目录）"
-      return 0
+      return 1
     }
   fi
 
@@ -597,7 +631,7 @@ _copy_skill() {
   if [ -d "$_dest" ]; then
     backup_and_remove_skill_dir "$_dest" || {
       say "  ⚠️  跳过 ${_dest}（保留原目录）"
-      return 0
+      return 1
     }
   fi
 
diff --git a/test/scripts/changelog_pr_gate_test.go b/test/scripts/changelog_pr_gate_test.go
index d85a9d83..5335e57e 100644
--- a/test/scripts/changelog_pr_gate_test.go
+++ b/test/scripts/changelog_pr_gate_test.go
@@ -477,12 +477,13 @@ func TestChangelogPRFastPathWorkflowContract(t *testing.T) {
 		"comparison.total_commits === comparison.ahead_by",
 		"run.app?.slug !== 'github-actions'",
 		"predecessor Code Admission is not fully successful",
-		`test "$(git rev-parse HEAD^1)" = "$PR_BASE_SHA"`,
 		`test "$(git rev-parse HEAD^2)" = "$PR_HEAD_SHA"`,
+		`git merge-base --is-ancestor "$PR_BASE_SHA" "$merge_base_sha"`,
+		`echo "POLICY_BASE_SHA=$merge_base_sha"`,
 		"Files API and synthetic merge tree disagree on CHANGELOG scope",
 		"mode=--content-only",
 		"mode=--fast-path",
-		`"$mode" "$PR_BASE_SHA" HEAD`,
+		`"$mode" "$POLICY_BASE_SHA" HEAD`,
 		`test "$(git rev-parse HEAD)" = "$PUSH_AFTER_SHA"`,
 		`--fast-path "$PUSH_BEFORE_SHA" "$PUSH_AFTER_SHA"`,
 		"needs.lint.outputs.platform_sensitive == 'true'",
@@ -515,8 +516,8 @@ func TestChangelogPRFastPathWorkflowContract(t *testing.T) {
 		"name: Test (changed packages)",
 		"changed-test-packages.sh",
 		"Verify authoritative synthetic merge",
-		`test "$(git rev-parse HEAD^1)" = "$PR_BASE_SHA"`,
 		`test "$(git rev-parse HEAD^2)" = "$PR_HEAD_SHA"`,
+		`echo "TEST_BASE_REF=$merge_base_sha"`,
 		`echo "TEST_HEAD_REF=$(git rev-parse HEAD)"`,
 		"list \"$TEST_BASE_REF\" \"$TEST_HEAD_REF\"",
 		"needs.lint.outputs.full_suite != 'true'",
diff --git a/test/scripts/install_js_smoke.mjs b/test/scripts/install_js_smoke.mjs
index c8f76e76..c5746d17 100644
--- a/test/scripts/install_js_smoke.mjs
+++ b/test/scripts/install_js_smoke.mjs
@@ -23,6 +23,8 @@
  *                             "invalid DWS_SKILL_MODE" error.
  *   4. multi-only zip, mono — mono install is skipped with a warning; the
  *                             staging root is NOT copied into a dws/ dir.
+ *   5. backup failure       — preserves mono and writes no multi skill into
+ *                             the failed Agent target.
  *
  * Requirements: unix host with tar/zip/unzip on PATH (the same tools
  * install.js itself shells out to). Skips cleanly on win32.
@@ -213,6 +215,29 @@ scenario("multi-only zip in mono mode skips skill install instead of copying sta
   }
 });
 
+scenario("backup failure preserves mono and writes no multi skills", () => {
+  const { tmp, pkg, home } = stagePkg({
+    "mono/SKILL.md": "# mono fixture\n",
+    "multi/dingtalk-test/SKILL.md": "# dingtalk-test\n",
+    "multi/dws-shared/SKILL.md": "# dws-shared\n",
+  });
+  try {
+    const base = path.join(home, ".agents", "skills");
+    writeFile(path.join(base, "dws", "SKILL.md"), "old mono\n");
+    // Poison the backup root: mkdirSync(<file>/<stamp>) must fail.
+    writeFile(path.join(home, ".dws", "skill-backups"), "not a directory\n");
+
+    const res = runInstall(pkg, home, "multi");
+    assert.equal(res.status, 0, `exit=${res.status}\nstdout=${res.stdout}\nstderr=${res.stderr}`);
+    assert.match(res.stderr, /未安装 multi/);
+    assert.equal(fs.readFileSync(path.join(base, "dws", "SKILL.md"), "utf8"), "old mono\n");
+    assert.ok(!fs.existsSync(path.join(base, "dingtalk-test")), "product skill not installed after cleanup failure");
+    assert.ok(!fs.existsSync(path.join(base, "dws-shared")), "shared skill not installed after cleanup failure");
+  } finally {
+    fs.rmSync(tmp, { recursive: true, force: true });
+  }
+});
+
 for (const [name, fn] of scenarios) {
   process.stdout.write(`• ${name} ... `);
   fn();
diff --git a/test/scripts/install_script_test.go b/test/scripts/install_script_test.go
index 08bae23b..b3d9498d 100644
--- a/test/scripts/install_script_test.go
+++ b/test/scripts/install_script_test.go
@@ -967,8 +967,8 @@ func findSkillBackup(fakeHome, name, content string) string {
 // TestInstallScriptBackupFailureKeepsOriginalDir pins the fail-safe contract:
 // when the backup destination cannot be created (skill-backups pre-created as
 // a regular file), the installer must keep every pre-existing skill directory
-// untouched and still complete the install overall — a backup failure must
-// never degrade into a hard delete or abort the run.
+// untouched and skip the affected Agent target — a backup failure must never
+// degrade into a hard delete or leave a mixed mono + multi layout.
 func TestInstallScriptBackupFailureKeepsOriginalDir(t *testing.T) {
 	t.Parallel()
 
@@ -1003,6 +1003,111 @@ func TestInstallScriptBackupFailureKeepsOriginalDir(t *testing.T) {
 	if err != nil || string(data) != "old mono\n" {
 		t.Fatalf("multi run must keep the mono leftover dws/ untouched on backup failure (data=%q, err=%v)\noutput:\n%s", string(data), err, out)
 	}
+	for _, name := range []string{"dingtalk-test", "dws-shared"} {
+		if _, err := os.Stat(filepath.Join(base, name)); !os.IsNotExist(err) {
+			t.Fatalf("multi run must not install %s after cleanup backup failure, stat err=%v\noutput:\n%s", name, err, out)
+		}
+	}
+}
+
+func TestInstallSkillsShellBackupFailureWritesNoMultiSkills(t *testing.T) {
+	scriptPath, err := filepath.Abs(filepath.Join("..", "..", "scripts", "install-skills.sh"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	data, err := os.ReadFile(scriptPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cut := strings.LastIndex(string(data), "\nmain\n")
+	if cut < 0 {
+		t.Fatal("install-skills.sh final main invocation not found")
+	}
+	library := filepath.Join(t.TempDir(), "install-skills-lib.sh")
+	mustWriteFile(t, library, data[:cut], 0o755)
+
+	home := t.TempDir()
+	root := filepath.Join(t.TempDir(), "project")
+	base := filepath.Join(root, ".agents", "skills")
+	multi := filepath.Join(t.TempDir(), "multi")
+	mustWriteFile(t, filepath.Join(base, "dws", "SKILL.md"), []byte("old mono\n"), 0o644)
+	mustWriteFile(t, filepath.Join(multi, "dingtalk-test", "SKILL.md"), []byte("new multi\n"), 0o644)
+	mustWriteFile(t, filepath.Join(home, ".dws", "skill-backups"), []byte("not a directory\n"), 0o644)
+
+	harness := `. "$DWS_TEST_LIBRARY"
+install_multi_skills_to_root "$DWS_TEST_MULTI" "$DWS_TEST_ROOT"
+`
+	cmd := exec.Command("sh", "-c", harness)
+	cmd.Env = append(os.Environ(),
+		"HOME="+home,
+		"DWS_TEST_LIBRARY="+library,
+		"DWS_TEST_MULTI="+multi,
+		"DWS_TEST_ROOT="+root,
+	)
+	if output, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("install-skills harness failed: %v\n%s", err, output)
+	}
+	if data, err := os.ReadFile(filepath.Join(base, "dws", "SKILL.md")); err != nil || string(data) != "old mono\n" {
+		t.Fatalf("mono changed after backup failure (data=%q, err=%v)", string(data), err)
+	}
+	if _, err := os.Stat(filepath.Join(base, "dingtalk-test")); !os.IsNotExist(err) {
+		t.Fatalf("multi installed after backup failure, stat err=%v", err)
+	}
+}
+
+func TestInstallPowerShellBackupFailureWritesNoMultiSkills(t *testing.T) {
+	pwsh, err := exec.LookPath("pwsh")
+	if err != nil {
+		if runtime.GOOS == "windows" {
+			pwsh, err = exec.LookPath("powershell")
+		}
+		if err != nil {
+			t.Skip("PowerShell is not available")
+		}
+	}
+	scriptPath, err := filepath.Abs(filepath.Join("..", "..", "scripts", "install.ps1"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	data, err := os.ReadFile(scriptPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cut := strings.LastIndex(string(data), "# ── Main")
+	if cut < 0 {
+		t.Fatal("install.ps1 main section not found")
+	}
+	prefix := strings.ReplaceAll(string(data[:cut]), "$HOME", "$env:DWS_TEST_HOME")
+	prefix += `
+$ok = Install-MultiToBase -MultiSrc $env:DWS_TEST_MULTI -BaseDir $env:DWS_TEST_BASE -Root $env:DWS_TEST_HOME -AgentDir ".agents\skills"
+if ($ok) { exit 2 }
+exit 0
+`
+	harnessPath := filepath.Join(t.TempDir(), "install-harness.ps1")
+	mustWriteFile(t, harnessPath, []byte(prefix), 0o644)
+
+	home := t.TempDir()
+	base := filepath.Join(home, ".agents", "skills")
+	multi := filepath.Join(t.TempDir(), "multi")
+	mustWriteFile(t, filepath.Join(base, "dws", "SKILL.md"), []byte("old mono\n"), 0o644)
+	mustWriteFile(t, filepath.Join(multi, "dingtalk-test", "SKILL.md"), []byte("new multi\n"), 0o644)
+	mustWriteFile(t, filepath.Join(home, ".dws", "skill-backups"), []byte("not a directory\n"), 0o644)
+
+	cmd := exec.Command(pwsh, "-NoProfile", "-NonInteractive", "-File", harnessPath)
+	cmd.Env = append(os.Environ(),
+		"DWS_TEST_HOME="+home,
+		"DWS_TEST_MULTI="+multi,
+		"DWS_TEST_BASE="+base,
+	)
+	if output, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("PowerShell harness failed: %v\n%s", err, output)
+	}
+	if data, err := os.ReadFile(filepath.Join(base, "dws", "SKILL.md")); err != nil || string(data) != "old mono\n" {
+		t.Fatalf("mono changed after PowerShell backup failure (data=%q, err=%v)", string(data), err)
+	}
+	if _, err := os.Stat(filepath.Join(base, "dingtalk-test")); !os.IsNotExist(err) {
+		t.Fatalf("PowerShell installed multi after backup failure, stat err=%v", err)
+	}
 }
 
 func writeTarGz(t *testing.T, path string, files map[string]string) {