diff --git a/scripts/install-devapp.sh b/scripts/install-devapp.sh
index 0a21c72e..30cbdeda 100755
--- a/scripts/install-devapp.sh
+++ b/scripts/install-devapp.sh
@@ -95,8 +95,8 @@ refresh_cache_tree() {
 backup_skill_dir() {
   victim="$1"
   [ -e "$victim" ] || [ -L "$victim" ] || { printf '\n'; return 0; }
-  # Prune before creating this run's archive, so the backup the caller is about
-  # to depend on for rollback can never be a prune candidate.
+  # Prune before creating this run's archive; every stamp this run has already
+  # created is registered, so pruning can only remove earlier-run batches.
   prune_skill_backups
   stamp="$(date -u +%Y%m%d-%H%M%S)"
   name="$(printf '%s' "$victim" | sed 's#[/\\]#-#g; s#^-##')"
@@ -110,18 +110,34 @@ backup_skill_dir() {
       return 1
     fi
   done
+  record_current_run_backup_stamp "$backup_root"
   mkdir -p "$backup_root" || return 1
   mv "$victim" "$backup" || return 1
   printf '%s\n' "$backup"
 }
 
 # prune_skill_backups keeps only the newest SKILL_BACKUP_KEEP stamped backup
-# directories under $HOME/.dws/skill-backups, matching Go's skillBackupKeep /
-# pruneSkillBackups. Glob order is lexicographic and the stamps are UTC
-# YYYYmmdd-HHMMSS, so the oldest sort first. Best-effort: a removal failure is
-# reported and never fatal.
+# directories from earlier runs under $HOME/.dws/skill-backups, matching Go's
+# skillBackupKeep / pruneSkillBackups. Stamp directories created by the
+# current process are never pruned (mirroring Go's run-root registry and
+# install.js's currentRunBackupRoots), so a migration that retires more than
+# SKILL_BACKUP_KEEP batches stays reversible. Glob order is lexicographic and
+# the stamps are UTC YYYYmmdd-HHMMSS, so the oldest sort first. Best-effort:
+# a removal failure is reported and never fatal.
 SKILL_BACKUP_KEEP=5
 
+# Stamp directories created by this run, recorded by backup_skill_dir so
+# pruning can never delete a backup the running migration may still need to
+# roll back to.
+CURRENT_RUN_BACKUP_STAMPS=""
+
+record_current_run_backup_stamp() {
+  case " $CURRENT_RUN_BACKUP_STAMPS " in
+    *" $1 "*) return 0 ;;
+  esac
+  CURRENT_RUN_BACKUP_STAMPS="${CURRENT_RUN_BACKUP_STAMPS} $1"
+}
+
 # is_skill_backup_stamp accepts only directory names DWS itself writes: UTC
 # YYYYmmdd-HHMMSS, with an optional -N collision suffix. Any other entry in
 # the backup root is foreign (user data, unrelated tooling) and is preserved
@@ -153,13 +169,15 @@ prune_skill_backups() {
   done
   [ "$prune_total" -gt "$SKILL_BACKUP_KEEP" ] || return 0
   prune_drop=$((prune_total - SKILL_BACKUP_KEEP))
-  prune_seen=0
   for prune_entry in "$prune_root"/*; do
+    [ "$prune_drop" -gt 0 ] || break
     [ -d "$prune_entry" ] || continue
     is_skill_backup_stamp "${prune_entry##*/}" || continue
-    prune_seen=$((prune_seen + 1))
-    [ "$prune_seen" -le "$prune_drop" ] || break
+    case " $CURRENT_RUN_BACKUP_STAMPS " in
+      *" $prune_entry "*) continue ;;
+    esac
     rm -rf "$prune_entry" || printf '  ⚠️  旧 Skill 备份清理失败: %s\n' "$prune_entry" >&2
+    prune_drop=$((prune_drop - 1))
   done
 }
 
diff --git a/scripts/install-event.sh b/scripts/install-event.sh
index 93a3d392..bca8bb25 100755
--- a/scripts/install-event.sh
+++ b/scripts/install-event.sh
@@ -162,8 +162,8 @@ refresh_cache_tree() {
 backup_skill_dir() {
   victim="$1"
   [ -e "$victim" ] || [ -L "$victim" ] || { printf '\n'; return 0; }
-  # Prune before creating this run's archive, so the backup the caller is about
-  # to depend on for rollback can never be a prune candidate.
+  # Prune before creating this run's archive; every stamp this run has already
+  # created is registered, so pruning can only remove earlier-run batches.
   prune_skill_backups
   stamp="$(date -u +%Y%m%d-%H%M%S)"
   name="$(printf '%s' "$victim" | sed 's#[/\\]#-#g; s#^-##')"
@@ -179,18 +179,34 @@ backup_skill_dir() {
       return 1
     fi
   done
+  record_current_run_backup_stamp "$backup_root"
   mkdir -p "$backup_root" || return 1
   mv "$victim" "$backup" || return 1
   printf '%s\n' "$backup"
 }
 
 # prune_skill_backups keeps only the newest SKILL_BACKUP_KEEP stamped backup
-# directories under $HOME/.dws/skill-backups, matching Go's skillBackupKeep /
-# pruneSkillBackups. Glob order is lexicographic and the stamps are UTC
-# YYYYmmdd-HHMMSS, so the oldest sort first. Best-effort: a removal failure is
-# reported and never fatal.
+# directories from earlier runs under $HOME/.dws/skill-backups, matching Go's
+# skillBackupKeep / pruneSkillBackups. Stamp directories created by the
+# current process are never pruned (mirroring Go's run-root registry and
+# install.js's currentRunBackupRoots), so a migration that retires more than
+# SKILL_BACKUP_KEEP batches stays reversible. Glob order is lexicographic and
+# the stamps are UTC YYYYmmdd-HHMMSS, so the oldest sort first. Best-effort:
+# a removal failure is reported and never fatal.
 SKILL_BACKUP_KEEP=5
 
+# Stamp directories created by this run, recorded by backup_skill_dir so
+# pruning can never delete a backup the running migration may still need to
+# roll back to.
+CURRENT_RUN_BACKUP_STAMPS=""
+
+record_current_run_backup_stamp() {
+  case " $CURRENT_RUN_BACKUP_STAMPS " in
+    *" $1 "*) return 0 ;;
+  esac
+  CURRENT_RUN_BACKUP_STAMPS="${CURRENT_RUN_BACKUP_STAMPS} $1"
+}
+
 # is_skill_backup_stamp accepts only directory names DWS itself writes: UTC
 # YYYYmmdd-HHMMSS, with an optional -N collision suffix. Any other entry in
 # the backup root is foreign (user data, unrelated tooling) and is preserved
@@ -222,13 +238,15 @@ prune_skill_backups() {
   done
   [ "$prune_total" -gt "$SKILL_BACKUP_KEEP" ] || return 0
   prune_drop=$((prune_total - SKILL_BACKUP_KEEP))
-  prune_seen=0
   for prune_entry in "$prune_root"/*; do
+    [ "$prune_drop" -gt 0 ] || break
     [ -d "$prune_entry" ] || continue
     is_skill_backup_stamp "${prune_entry##*/}" || continue
-    prune_seen=$((prune_seen + 1))
-    [ "$prune_seen" -le "$prune_drop" ] || break
+    case " $CURRENT_RUN_BACKUP_STAMPS " in
+      *" $prune_entry "*) continue ;;
+    esac
     rm -rf "$prune_entry" || printf '  ⚠️  旧 Skill 备份清理失败: %s\n' "$prune_entry" >&2
+    prune_drop=$((prune_drop - 1))
   done
 }
 
diff --git a/scripts/install-skills.sh b/scripts/install-skills.sh
index bd48c7a3..88c58ad4 100755
--- a/scripts/install-skills.sh
+++ b/scripts/install-skills.sh
@@ -67,6 +67,7 @@ backup_and_remove_skill_dir() {
       return 1
     fi
   done
+  record_current_run_backup_stamp "$(dirname "$_bed_target")"
   mkdir -p "$(dirname "$_bed_target")" 2>/dev/null || {
     printf '  ⚠️  无法创建备份目录，保留原目录 %s\n' "$_bed_dir"
     return 1
@@ -80,13 +81,27 @@ backup_and_remove_skill_dir() {
   return 1
 }
 
-# prune_skill_backups keeps only the newest DWS_SKILL_BACKUP_KEEP stamped backup
-# directories under $HOME/.dws/skill-backups, matching Go's skillBackupKeep /
-# pruneSkillBackups. Best-effort: a removal failure is reported, never fatal.
-# Only safe to call once every backup manifest of this run has been consumed,
-# because a single transaction can span more than one timestamp.
+# prune_skill_backups keeps only the newest DWS_SKILL_BACKUP_KEEP stamped
+# backup directories from earlier runs under $HOME/.dws/skill-backups,
+# matching Go's skillBackupKeep / pruneSkillBackups. Stamp directories created
+# by the current process are never pruned (mirroring Go's run-root registry
+# and install.js's currentRunBackupRoots), so a migration that retires more
+# than DWS_SKILL_BACKUP_KEEP batches stays reversible. Best-effort: a removal
+# failure is reported, never fatal.
 DWS_SKILL_BACKUP_KEEP=5
 
+# Stamp directories created by this run, recorded by
+# backup_and_remove_skill_dir so pruning can never delete a backup the
+# running migration may still need to roll back to.
+DWS_CURRENT_RUN_BACKUP_STAMPS=""
+
+record_current_run_backup_stamp() {
+  case " $DWS_CURRENT_RUN_BACKUP_STAMPS " in
+    *" $1 "*) return 0 ;;
+  esac
+  DWS_CURRENT_RUN_BACKUP_STAMPS="${DWS_CURRENT_RUN_BACKUP_STAMPS} $1"
+}
+
 # is_skill_backup_stamp accepts only directory names DWS itself writes: UTC
 # YYYYmmdd-HHMMSS, with an optional -N collision suffix. Any other entry in
 # the backup root is foreign (user data, unrelated tooling) and is preserved
@@ -118,13 +133,15 @@ prune_skill_backups() {
   done
   [ "$_psb_total" -gt "$DWS_SKILL_BACKUP_KEEP" ] || return 0
   _psb_drop=$((_psb_total - DWS_SKILL_BACKUP_KEEP))
-  _psb_seen=0
   for _psb_entry in "$_psb_root"/*; do
+    [ "$_psb_drop" -gt 0 ] || break
     [ -d "$_psb_entry" ] || continue
     is_skill_backup_stamp "${_psb_entry##*/}" || continue
-    _psb_seen=$((_psb_seen + 1))
-    [ "$_psb_seen" -le "$_psb_drop" ] || break
+    case " $DWS_CURRENT_RUN_BACKUP_STAMPS " in
+      *" $_psb_entry "*) continue ;;
+    esac
     rm -rf "$_psb_entry" || printf '  ⚠️  旧 Skill 备份清理失败: %s\n' "$_psb_entry"
+    _psb_drop=$((_psb_drop - 1))
   done
 }
 
diff --git a/scripts/install.sh b/scripts/install.sh
index 0ca489e4..62d23fbd 100755
--- a/scripts/install.sh
+++ b/scripts/install.sh
@@ -85,6 +85,7 @@ backup_and_remove_skill_dir() {
       return 1
     fi
   done
+  record_current_run_backup_stamp "$(dirname "$_bed_target")"
   mkdir -p "$(dirname "$_bed_target")" 2>/dev/null || {
     say "  ⚠️  无法创建备份目录，保留原目录 $_bed_dir"
     return 1
@@ -98,13 +99,27 @@ backup_and_remove_skill_dir() {
   return 1
 }
 
-# prune_skill_backups keeps only the newest DWS_SKILL_BACKUP_KEEP stamped backup
-# directories under $HOME/.dws/skill-backups, matching Go's skillBackupKeep /
-# pruneSkillBackups. Best-effort: a removal failure is reported, never fatal.
-# Only safe to call once every backup manifest of this run has been consumed,
-# because a single transaction can span more than one timestamp.
+# prune_skill_backups keeps only the newest DWS_SKILL_BACKUP_KEEP stamped
+# backup directories from earlier runs under $HOME/.dws/skill-backups,
+# matching Go's skillBackupKeep / pruneSkillBackups. Stamp directories created
+# by the current process are never pruned (mirroring Go's run-root registry
+# and install.js's currentRunBackupRoots), so a migration that retires more
+# than DWS_SKILL_BACKUP_KEEP batches stays reversible. Best-effort: a removal
+# failure is reported, never fatal.
 DWS_SKILL_BACKUP_KEEP=5
 
+# Stamp directories created by this run, recorded by
+# backup_and_remove_skill_dir so pruning can never delete a backup the
+# running migration may still need to roll back to.
+DWS_CURRENT_RUN_BACKUP_STAMPS=""
+
+record_current_run_backup_stamp() {
+  case " $DWS_CURRENT_RUN_BACKUP_STAMPS " in
+    *" $1 "*) return 0 ;;
+  esac
+  DWS_CURRENT_RUN_BACKUP_STAMPS="${DWS_CURRENT_RUN_BACKUP_STAMPS} $1"
+}
+
 # is_skill_backup_stamp accepts only directory names DWS itself writes: UTC
 # YYYYmmdd-HHMMSS, with an optional -N collision suffix. Any other entry in
 # the backup root is foreign (user data, unrelated tooling) and is preserved
@@ -136,13 +151,15 @@ prune_skill_backups() {
   done
   [ "$_psb_total" -gt "$DWS_SKILL_BACKUP_KEEP" ] || return 0
   _psb_drop=$((_psb_total - DWS_SKILL_BACKUP_KEEP))
-  _psb_seen=0
   for _psb_entry in "$_psb_root"/*; do
+    [ "$_psb_drop" -gt 0 ] || break
     [ -d "$_psb_entry" ] || continue
     is_skill_backup_stamp "${_psb_entry##*/}" || continue
-    _psb_seen=$((_psb_seen + 1))
-    [ "$_psb_seen" -le "$_psb_drop" ] || break
+    case " $DWS_CURRENT_RUN_BACKUP_STAMPS " in
+      *" $_psb_entry "*) continue ;;
+    esac
     rm -rf "$_psb_entry" || say "  ⚠️  旧 Skill 备份清理失败: $_psb_entry"
+    _psb_drop=$((_psb_drop - 1))
   done
 }
 
diff --git a/test/scripts/skill_backup_prune_test.go b/test/scripts/skill_backup_prune_test.go
new file mode 100644
index 00000000..6defc75b
--- /dev/null
+++ b/test/scripts/skill_backup_prune_test.go
@@ -0,0 +1,199 @@
+// Copyright 2026 Alibaba Group
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package scripts_test
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+// shellPruneScriptTargets are the standalone installers that embed their own
+// copy of prune_skill_backups. Each must keep every backup stamp the running
+// process created, mirroring Go's run-root registry and install.js's
+// currentRunBackupRoots, so a migration retiring more than the keep limit
+// stays reversible.
+var shellPruneScriptTargets = []string{
+	"install.sh",
+	"install-skills.sh",
+	"install-event.sh",
+	"install-devapp.sh",
+}
+
+// extractShellFunction pulls a top-level `name() { ... }` definition out of a
+// script so the shipped logic — not a copy — is what the test exercises.
+func extractShellFunction(t *testing.T, scriptPath, name string) string {
+	t.Helper()
+	data, err := os.ReadFile(scriptPath)
+	if err != nil {
+		t.Fatalf("read %s: %v", scriptPath, err)
+	}
+	text := string(data)
+	start := strings.Index(text, "\n"+name+"() {")
+	if start < 0 {
+		t.Fatalf("function %s not found in %s", name, scriptPath)
+	}
+	start++
+	end := strings.Index(text[start:], "\n}\n")
+	if end < 0 {
+		t.Fatalf("function %s has no top-level closing brace in %s", name, scriptPath)
+	}
+	return text[start : start+end+3]
+}
+
+// runShellPruneScenario builds a sandbox HOME with the given pre-existing
+// (foreign) stamps, registers the given stamps as created by the current run,
+// runs the script's own prune_skill_backups, and returns the surviving stamp
+// directories.
+func runShellPruneScenario(t *testing.T, scriptPath string, foreignStamps, runStamps []string) []string {
+	t.Helper()
+	home := t.TempDir()
+	backupRoot := filepath.Join(home, ".dws", "skill-backups")
+	for _, stamp := range foreignStamps {
+		if err := os.MkdirAll(filepath.Join(backupRoot, stamp), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	var driver strings.Builder
+	driver.WriteString("#!/bin/sh\n")
+	driver.WriteString("say() { :; }\n")
+	// The keep limit is a script-level variable outside the extracted
+	// functions; set both spellings the four installers use.
+	driver.WriteString("DWS_SKILL_BACKUP_KEEP=5\n")
+	driver.WriteString("SKILL_BACKUP_KEEP=5\n")
+	driver.WriteString(extractShellFunction(t, scriptPath, "is_skill_backup_stamp"))
+	driver.WriteString("\n")
+	driver.WriteString(extractShellFunction(t, scriptPath, "record_current_run_backup_stamp"))
+	driver.WriteString("\n")
+	driver.WriteString(extractShellFunction(t, scriptPath, "prune_skill_backups"))
+	driver.WriteString("\n")
+	for _, stamp := range runStamps {
+		if err := os.MkdirAll(filepath.Join(backupRoot, stamp), 0o755); err != nil {
+			t.Fatal(err)
+		}
+		driver.WriteString("record_current_run_backup_stamp \"$HOME/.dws/skill-backups/" + stamp + "\"\n")
+	}
+	driver.WriteString("prune_skill_backups\n")
+
+	driverPath := filepath.Join(t.TempDir(), "prune-driver.sh")
+	if err := os.WriteFile(driverPath, []byte(driver.String()), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	cmd := exec.Command("sh", driverPath)
+	cmd.Env = append(os.Environ(), "HOME="+home)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("prune driver failed: %v\n%s", err, out)
+	}
+
+	entries, err := os.ReadDir(backupRoot)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var surviving []string
+	for _, entry := range entries {
+		if entry.IsDir() {
+			surviving = append(surviving, entry.Name())
+		}
+	}
+	return surviving
+}
+
+func assertStampsSurvive(t *testing.T, surviving []string, want ...string) {
+	t.Helper()
+	left := make(map[string]bool)
+	for _, stamp := range surviving {
+		left[stamp] = true
+	}
+	for _, stamp := range want {
+		if !left[stamp] {
+			t.Fatalf("stamp %s must survive pruning, surviving=%v", stamp, surviving)
+		}
+		delete(left, stamp)
+	}
+	for stamp := range left {
+		t.Fatalf("stamp %s must have been pruned, surviving=%v", stamp, surviving)
+	}
+}
+
+// TestInstallShellPruneKeepsCurrentRunBackups pins the reversibility contract
+// the changelog states for every install surface: pruning may only remove
+// batches from earlier runs. The old shell logic deleted the oldest excess
+// stamps regardless of origin, so a single migration retiring more than five
+// batches silently destroyed its own rollback material.
+func TestInstallShellPruneKeepsCurrentRunBackups(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skipf("shell installer tests do not run on %s", runtime.GOOS)
+	}
+	for _, name := range shellPruneScriptTargets {
+		t.Run(name, func(t *testing.T) {
+			scriptPath := filepath.Join("..", "..", "scripts", name)
+			if _, err := os.Stat(scriptPath); err != nil {
+				t.Fatalf("stat %s: %v", scriptPath, err)
+			}
+
+			t.Run("run that exceeds the keep limit loses nothing", func(t *testing.T) {
+				var runStamps []string
+				for i := 1; i <= 8; i++ {
+					runStamps = append(runStamps, stampName(i))
+				}
+				surviving := runShellPruneScenario(t, scriptPath, nil, runStamps)
+				assertStampsSurvive(t, surviving, runStamps...)
+			})
+
+			t.Run("only earlier-run batches are pruned", func(t *testing.T) {
+				var foreignStamps []string
+				for i := 1; i <= 6; i++ {
+					foreignStamps = append(foreignStamps, oldStampName(i))
+				}
+				runStamps := []string{stampName(1), stampName(2)}
+				surviving := runShellPruneScenario(t, scriptPath, foreignStamps, runStamps)
+				// Total 8, keep 5: three oldest foreign batches go, the
+				// current run keeps both of its own.
+				assertStampsSurvive(t, surviving,
+					oldStampName(4), oldStampName(5), oldStampName(6),
+					stampName(1), stampName(2))
+			})
+
+			t.Run("foreign-only history still prunes to the keep limit", func(t *testing.T) {
+				var foreignStamps []string
+				for i := 1; i <= 7; i++ {
+					foreignStamps = append(foreignStamps, oldStampName(i))
+				}
+				surviving := runShellPruneScenario(t, scriptPath, foreignStamps, nil)
+				assertStampsSurvive(t, surviving,
+					oldStampName(3), oldStampName(4), oldStampName(5),
+					oldStampName(6), oldStampName(7))
+			})
+		})
+	}
+}
+
+func stampName(i int) string {
+	return "20260817-0000" + twoDigits(i)
+}
+
+func oldStampName(i int) string {
+	return "20200101-0000" + twoDigits(i)
+}
+
+func twoDigits(i int) string {
+	if i < 10 {
+		return "0" + string(rune('0'+i))
+	}
+	return string(rune('0'+i/10)) + string(rune('0'+i%10))
+}