diff --git a/browser/archive.go b/browser/archive.go
new file mode 100644
index 0000000..28e3d34
--- /dev/null
+++ b/browser/archive.go
@@ -0,0 +1,68 @@
+package browser
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/moond4rk/hackbrowserdata/browser/chromium"
+	"github.com/moond4rk/hackbrowserdata/filemanager"
+	"github.com/moond4rk/hackbrowserdata/log"
+	"github.com/moond4rk/hackbrowserdata/types"
+	"github.com/moond4rk/hackbrowserdata/utils/fileutil"
+)
+
+// Archivable is implemented by installations that can enumerate their decryption-relevant files for
+// cross-host transport (Chromium only).
+type Archivable interface {
+	BrowserKey() string
+	ArchiveSources(categories []types.Category) []chromium.ArchiveSource
+}
+
+// WriteArchive packs each browser's decryption-relevant files into a zip whose internal layout is
+// <browser-key>/<User Data layout>, so a restore can re-expand it and decrypt with a keys.json. Files
+// are staged through a locked-file session first because Windows holds exclusive SQLite locks. Returns
+// the number of source entries staged (a directory source counts once).
+func WriteArchive(browsers []Browser, categories []types.Category, outPath string) (int, error) {
+	session, err := filemanager.NewSession()
+	if err != nil {
+		return 0, err
+	}
+	defer session.Cleanup()
+
+	staging := session.TempDir()
+	seen := make(map[string]bool)
+	count := 0
+	for _, b := range browsers {
+		archivable, ok := b.(Archivable)
+		if !ok {
+			continue
+		}
+		key := archivable.BrowserKey()
+		for _, src := range archivable.ArchiveSources(categories) {
+			entry := key + "/" + src.LayoutRel
+			if seen[entry] {
+				continue
+			}
+			seen[entry] = true
+
+			dst := filepath.Join(staging, key, filepath.FromSlash(src.LayoutRel))
+			if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
+				log.Warnf("archive: %s: %v", entry, err)
+				continue
+			}
+			if err := session.Acquire(src.AbsPath, dst, src.IsDir); err != nil {
+				log.Warnf("archive: acquire %s: %v", entry, err)
+				continue
+			}
+			count++
+		}
+	}
+	if count == 0 {
+		return 0, fmt.Errorf("no decryption-relevant files found to archive")
+	}
+	if err := fileutil.ZipDir(outPath, staging); err != nil {
+		return 0, fmt.Errorf("write archive %s: %w", outPath, err)
+	}
+	return count, nil
+}
diff --git a/browser/archive_test.go b/browser/archive_test.go
new file mode 100644
index 0000000..17af7f6
--- /dev/null
+++ b/browser/archive_test.go
@@ -0,0 +1,58 @@
+package browser
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/moond4rk/hackbrowserdata/browser/chromium"
+	"github.com/moond4rk/hackbrowserdata/types"
+	"github.com/moond4rk/hackbrowserdata/utils/fileutil"
+)
+
+// TestWriteArchive_RoundTrip exercises the archive path: ArchiveSources -> WriteArchive (stage+zip)
+// -> Unzip, asserting the archive's internal layout is <key>/<User Data layout>.
+func TestWriteArchive_RoundTrip(t *testing.T) {
+	origin := t.TempDir()
+	def := filepath.Join(origin, "Default")
+	if err := os.MkdirAll(def, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(def, "Preferences"), []byte("{}"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(def, "History"), []byte("hist"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(origin, "Local State"), []byte("{}"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	b, err := chromium.NewBrowser(types.BrowserConfig{Key: "chrome", Name: "chrome", Kind: types.Chromium, UserDataDir: origin})
+	if err != nil || b == nil {
+		t.Fatalf("NewBrowser: b=%v err=%v", b, err)
+	}
+
+	zipPath := filepath.Join(t.TempDir(), "data.zip")
+	n, err := WriteArchive([]Browser{b}, []types.Category{types.History}, zipPath)
+	if err != nil {
+		t.Fatalf("WriteArchive: %v", err)
+	}
+	if n == 0 {
+		t.Fatal("WriteArchive captured 0 entries")
+	}
+
+	extracted := t.TempDir()
+	if err := fileutil.Unzip(zipPath, extracted); err != nil {
+		t.Fatalf("Unzip: %v", err)
+	}
+	for _, rel := range []string{
+		filepath.Join("chrome", "Default", "History"),
+		filepath.Join("chrome", "Default", "Preferences"),
+		filepath.Join("chrome", "Local State"),
+	} {
+		if _, err := os.Stat(filepath.Join(extracted, rel)); err != nil {
+			t.Errorf("expected %s in archive layout: %v", rel, err)
+		}
+	}
+}
diff --git a/browser/chromium/archive.go b/browser/chromium/archive.go
new file mode 100644
index 0000000..ae1f93c
--- /dev/null
+++ b/browser/chromium/archive.go
@@ -0,0 +1,64 @@
+package chromium
+
+import (
+	"path"
+	"path/filepath"
+
+	"github.com/moond4rk/hackbrowserdata/types"
+	"github.com/moond4rk/hackbrowserdata/utils/fileutil"
+)
+
+// ArchiveSource is one decryption-relevant file or directory plus its path inside the browser's
+// User Data tree (forward-slash), so an archive can be re-expanded into a working profile layout.
+type ArchiveSource struct {
+	AbsPath   string
+	LayoutRel string
+	IsDir     bool
+}
+
+// installationFiles live at the User Data root (shared across profiles); archived for fidelity even
+// though keys.json-based restore does not read them.
+var installationFiles = []string{"Local State"}
+
+// ArchiveSources lists the files an archive must capture for the given categories: the User Data root
+// files (Local State), every resolved category source per profile, plus each profile's Preferences
+// marker so a restore can rediscover the profile. LayoutRel is forward-slash, relative to the root.
+func (b *Browser) ArchiveSources(categories []types.Category) []ArchiveSource {
+	var out []ArchiveSource
+	for _, name := range installationFiles {
+		abs := filepath.Join(b.cfg.UserDataDir, name)
+		if fileutil.FileExists(abs) {
+			out = append(out, ArchiveSource{AbsPath: abs, LayoutRel: name, IsDir: false})
+		}
+	}
+	for _, p := range b.profiles {
+		// Flat-layout installs hold data directly under UserDataDir (profileDir == root); skip the
+		// basename so the archive matches the real layout instead of inserting a phantom level.
+		profileRel := ""
+		if p.profileDir != b.cfg.UserDataDir {
+			profileRel = filepath.Base(p.profileDir)
+		}
+		for _, marker := range profileMarkers {
+			abs := filepath.Join(p.profileDir, marker)
+			if fileutil.FileExists(abs) {
+				out = append(out, ArchiveSource{
+					AbsPath:   abs,
+					LayoutRel: path.Join(profileRel, marker),
+					IsDir:     false,
+				})
+			}
+		}
+		for _, cat := range categories {
+			rp, ok := p.sourcePaths[cat]
+			if !ok {
+				continue
+			}
+			out = append(out, ArchiveSource{
+				AbsPath:   rp.absPath,
+				LayoutRel: path.Join(profileRel, rp.rel),
+				IsDir:     rp.isDir,
+			})
+		}
+	}
+	return out
+}
diff --git a/browser/chromium/archive_test.go b/browser/chromium/archive_test.go
new file mode 100644
index 0000000..ecc13c7
--- /dev/null
+++ b/browser/chromium/archive_test.go
@@ -0,0 +1,88 @@
+package chromium
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/moond4rk/hackbrowserdata/types"
+)
+
+func TestArchiveSources_ForwardSlashLayout(t *testing.T) {
+	udd := t.TempDir()
+	networkDir := filepath.Join(udd, "Default", "Network")
+	if err := os.MkdirAll(networkDir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(udd, "Default", "Preferences"), []byte("{}"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(networkDir, "Cookies"), []byte("x"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(udd, "Local State"), []byte("{}"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	b, err := NewBrowser(types.BrowserConfig{Key: "chrome", Name: "chrome", Kind: types.Chromium, UserDataDir: udd})
+	if err != nil || b == nil {
+		t.Fatalf("NewBrowser: b=%v err=%v", b, err)
+	}
+
+	srcs := b.ArchiveSources([]types.Category{types.Cookie})
+
+	var gotCookie, gotMarker, gotLocalState bool
+	for _, s := range srcs {
+		if strings.Contains(s.LayoutRel, `\`) {
+			t.Errorf("LayoutRel must be forward-slash, got %q", s.LayoutRel)
+		}
+		switch s.LayoutRel {
+		case "Default/Network/Cookies":
+			gotCookie = true
+		case "Default/Preferences":
+			gotMarker = true
+		case "Local State":
+			gotLocalState = true
+		}
+	}
+	if !gotCookie {
+		t.Errorf("missing Cookies entry with layout path, got %+v", srcs)
+	}
+	if !gotMarker {
+		t.Errorf("missing Preferences marker entry (needed for restore profile discovery), got %+v", srcs)
+	}
+	if !gotLocalState {
+		t.Errorf("missing Local State entry (User Data root file), got %+v", srcs)
+	}
+}
+
+func TestArchiveSources_FlatLayoutNoExtraLevel(t *testing.T) {
+	// Flat-layout install: data lives directly under UserDataDir with no Default/ subdir, so
+	// discoverProfiles falls back to UserDataDir itself as the profile (profileDir == root).
+	udd := t.TempDir()
+	if err := os.WriteFile(filepath.Join(udd, "History"), []byte("x"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	b, err := NewBrowser(types.BrowserConfig{Key: "opera", Name: "opera", Kind: types.Chromium, UserDataDir: udd})
+	if err != nil || b == nil {
+		t.Fatalf("NewBrowser: b=%v err=%v", b, err)
+	}
+
+	srcs := b.ArchiveSources([]types.Category{types.History})
+
+	phantom := filepath.Base(udd) + "/"
+	var gotHistory bool
+	for _, s := range srcs {
+		if strings.HasPrefix(s.LayoutRel, phantom) {
+			t.Errorf("flat layout must not insert a %q level, got %q", phantom, s.LayoutRel)
+		}
+		if s.LayoutRel == "History" {
+			gotHistory = true
+		}
+	}
+	if !gotHistory {
+		t.Errorf("expected History at archive root, got %+v", srcs)
+	}
+}
diff --git a/browser/chromium/chromium.go b/browser/chromium/chromium.go
index 2848915..7527fee 100644
--- a/browser/chromium/chromium.go
+++ b/browser/chromium/chromium.go
@@ -55,6 +55,7 @@ func NewBrowser(cfg types.BrowserConfig) (*Browser, error) {
 func (b *Browser) SetRetrievers(r masterkey.Retrievers) { b.retrievers = r }
 
 func (b *Browser) BrowserName() string { return b.cfg.Name }
+func (b *Browser) BrowserKey() string  { return b.cfg.Key }
 func (b *Browser) UserDataDir() string { return b.cfg.UserDataDir }
 
 // Profiles returns the identity of every profile in this installation.
@@ -204,9 +205,11 @@ func hasAnySource(sources map[types.Category][]sourcePath, dir string) bool {
 	return false
 }
 
-// resolvedPath holds the absolute path and type for a discovered source.
+// resolvedPath holds the absolute path, the slash-relative source path, and the type of a discovered
+// source. rel is retained (not just absPath) so archive can reproduce the User Data layout.
 type resolvedPath struct {
 	absPath string
+	rel     string
 	isDir   bool
 }
 
@@ -222,7 +225,7 @@ func resolveSourcePaths(sources map[types.Category][]sourcePath, profileDir stri
 				continue
 			}
 			if sp.isDir == info.IsDir() {
-				resolved[cat] = resolvedPath{abs, sp.isDir}
+				resolved[cat] = resolvedPath{absPath: abs, rel: sp.rel, isDir: sp.isDir}
 				break
 			}
 		}
diff --git a/browser/chromium/source.go b/browser/chromium/source.go
index 5c5baff..dada72c 100644
--- a/browser/chromium/source.go
+++ b/browser/chromium/source.go
@@ -1,8 +1,6 @@
 package chromium
 
 import (
-	"path/filepath"
-
 	"github.com/moond4rk/hackbrowserdata/masterkey"
 	"github.com/moond4rk/hackbrowserdata/types"
 )
@@ -14,8 +12,10 @@ type sourcePath struct {
 	isDir bool   // true for directory targets (LevelDB, Session Storage)
 }
 
-func file(rel string) sourcePath { return sourcePath{rel: filepath.FromSlash(rel), isDir: false} }
-func dir(rel string) sourcePath  { return sourcePath{rel: filepath.FromSlash(rel), isDir: true} }
+// rel stays slash-canonical (e.g. "Network/Cookies"); filepath.Join converts at resolve time, and
+// archive reuses it verbatim as a forward-slash zip entry name.
+func file(rel string) sourcePath { return sourcePath{rel: rel, isDir: false} }
+func dir(rel string) sourcePath  { return sourcePath{rel: rel, isDir: true} }
 
 // chromiumSources defines the standard Chromium file layout.
 // Each category maps to one or more candidate paths tried in priority order;
diff --git a/cmd/hack-browser-data/archive.go b/cmd/hack-browser-data/archive.go
new file mode 100644
index 0000000..8ca7012
--- /dev/null
+++ b/cmd/hack-browser-data/archive.go
@@ -0,0 +1,49 @@
+package main
+
+import (
+	"github.com/spf13/cobra"
+
+	"github.com/moond4rk/hackbrowserdata/browser"
+	"github.com/moond4rk/hackbrowserdata/log"
+)
+
+func archiveCmd() *cobra.Command {
+	var (
+		browserName string
+		category    string
+		outputPath  string
+	)
+
+	cmd := &cobra.Command{
+		Use:   "archive",
+		Short: "Pack decryption-relevant profile files into a zip for cross-host restore",
+		Example: `  hack-browser-data archive
+  hack-browser-data archive -b chrome -c cookie -o chrome-cookies.zip`,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			browsers, err := browser.DiscoverBrowsers(browser.DiscoverOptions{Name: browserName})
+			if err != nil {
+				return err
+			}
+			if len(browsers) == 0 {
+				log.Warnf("no browsers found")
+				return nil
+			}
+			categories, err := parseCategories(category)
+			if err != nil {
+				return err
+			}
+			n, err := browser.WriteArchive(browsers, categories, outputPath)
+			if err != nil {
+				return err
+			}
+			log.Infof("Archived %d entries to %s", n, outputPath)
+			return nil
+		},
+	}
+
+	cmd.Flags().StringVarP(&browserName, "browser", "b", "all", "target browser: all|"+browser.Names())
+	cmd.Flags().StringVarP(&category, "category", "c", "all", "data categories (comma-separated): all|"+categoryNames())
+	cmd.Flags().StringVarP(&outputPath, "output", "o", "browser-data.zip", "output archive of decryption-relevant browser files")
+
+	return cmd
+}
diff --git a/cmd/hack-browser-data/main.go b/cmd/hack-browser-data/main.go
index d8c9c5e..a632f1f 100644
--- a/cmd/hack-browser-data/main.go
+++ b/cmd/hack-browser-data/main.go
@@ -31,7 +31,7 @@ GitHub: https://github.com/moonD4rk/HackBrowserData`,
 	root.PersistentFlags().BoolVarP(&verbose, "verbose", "v", false, "enable debug logging")
 
 	dump := dumpCmd()
-	root.AddCommand(dump, dumpKeysCmd(), restoreCmd(), listCmd(), versionCmd())
+	root.AddCommand(dump, dumpKeysCmd(), archiveCmd(), restoreCmd(), listCmd(), versionCmd())
 
 	// Default to dump when no subcommand is given.
 	// Copy dump flags to root so that `hack-browser-data -b chrome`
diff --git a/rfcs/013-cli-redesign-cross-host.md b/rfcs/013-cli-redesign-cross-host.md
index d8c7000..da54fb6 100644
--- a/rfcs/013-cli-redesign-cross-host.md
+++ b/rfcs/013-cli-redesign-cross-host.md
@@ -1,8 +1,9 @@
 # RFC-013: CLI Redesign — Flat-Verb Surface & Cross-Host Restore
 
 **Author**: moonD4rk
-**Status**: Accepted — implementation pending
+**Status**: Accepted — `archive` (#607) implemented; cross-platform `restore` (#606) pending
 **Created**: 2026-06-03
+**Revised**: 2026-06-06 (subdir-convention archive, dual-mode restore, Local State, delivery order)
 
 ## 1. Summary
 
@@ -41,8 +42,8 @@ Workflows:
 ```
 local     : hbd dump -b chrome -c cookie,password
 cross-host: origin>   hbd dumpkeys -o keys.json
-            origin>   hbd archive  -b chrome -o data.zip
-            analyst>  hbd restore --keys keys.json --data-zip data.zip -c cookie
+            origin>   hbd archive  -b chrome -o browser-data.zip
+            analyst>  hbd restore --keys keys.json --data-zip browser-data.zip -c cookie
 ```
 
 The `keys` parent command is removed: `keys export` becomes `dumpkeys`, `keys import` becomes `restore`, and a new `archive` fills the missing data-transport step. `dump` / `list` / `version` keep their current behavior; `dump` stays the default when no subcommand is given (which also covers the Windows double-click case).
@@ -63,8 +64,8 @@ The resolution to §2.3 is a single rule: **the set of browsers a command may ac
 The cross-host producer emits two independent, composable artifacts; the consumer takes both.
 
 - `dumpkeys` writes `keys.json` — the portable master keys (stdout by default for `ssh origin hbd dumpkeys | …` pipelines; `-o` for a 0600 file).
-- `archive` writes `data.zip` — only the decryption-relevant files for the requested `-c` categories (`Login Data`, `Cookies`, `Web Data`, `History`, … plus `Local State` and `Preferences`), read through the existing locked-file bypass, preserving the relative `User Data` layout so the zip's internal root *is* the `User Data` dir.
-- `restore` takes `--keys keys.json` and the data via two explicit flags, `--data-dir <dir>` or `--data-zip <zip>` (mutually exclusive, exactly one required). A zip is extracted to a temporary directory; a directory is used as-is. Because the archive preserves layout, `unzip data.zip -d X && restore --data-dir X` equals `restore --data-zip data.zip`.
+- `archive` writes `browser-data.zip` — the decryption-relevant files for the requested `-c` categories (`Login Data`, `Cookies`, `Web Data`, `History`, …), read through the existing locked-file bypass. To carry more than one browser and to keep restore unambiguous, the zip is laid out as `<browser-key>/<User Data layout>` (e.g. `chrome/Default/Network/Cookies`) — one subdir per installation, each subdir being that browser's `User Data` root. Two things are always included regardless of `-c`: each profile's `Preferences`/`Preferences_02` (so restore can rediscover the profile — the marker is no extraction source) and the installation's `Local State` (carried for fidelity only; restore decrypts with the keys in `keys.json` and never reads it). Zip entry names are always forward-slash, so a Windows-produced archive restores on macOS/Linux.
+- `restore` takes `--keys keys.json` and the data via two explicit flags, `--data-dir <dir>` or `--data-zip <zip>` (mutually exclusive, exactly one required). A zip is extracted to a temporary directory; a directory is used as-is, so `unzip browser-data.zip -d X && restore --data-dir X` equals `restore --data-zip browser-data.zip`. The data resolves two ways: when it holds `<browser-key>/` subdirs (the `archive` layout) each vault is rooted at its own subdir and several browsers restore at once; otherwise `--data-dir` is a single browser's hand-copied `User Data` root, which is unambiguous only for one vault — so `-b` must select it. This preserves the pre-redesign "point at a copied profile folder" workflow.
 
 `restore` is a **separate verb**, not a `dump --keys` mode. Folding it into `dump` would force one command to carry two mutually-exclusive input modes (`-b` for local discovery xor `--keys/--data` for transported artifacts) and dead flags (a `--keychain-pw` that silently does nothing once keys are supplied — a friction the earlier `dump --keys` design already hit). One verb, one job keeps each command's flags and help self-contained. `restore -b` is an **optional filter** over the dump's vaults, not a required selector, because the dump self-describes what each vault is (§4, §6).
 
@@ -90,9 +91,9 @@ This crystallizes the principle that lets cross-platform decryption and the curr
 
 Working backwards from the chosen surface:
 
-- **keydump struct** (`masterkey/dump.go`): the vault carries the engine kind so restore can construct without the local table. The `Browser` field becomes the canonical key (it was the display name), a `Kind` string field is added (values `chromium` / `chromium-yandex` / `chromium-opera`), and `DumpVersion` goes "1"→"2". `UserDataDir` and `Profiles` remain as informational fields. The keys stay `V10` / `V11` / `V20` (Chromium-only; Firefox keys are out of scope, §9).
-- **`browser/keydump.go`**: `BuildDump` records the kind; the overlay `ApplyDump` (which mutates locally-discovered browsers) is replaced by a construct-from-dump path that synthesizes a `BrowserConfig` from each vault and builds the engine directly — no `platformBrowsers()` dependency. This is the mechanical form of §4.
-- **`archive`** reuses the per-category source-path resolution already used by extraction, plus the existing locked-file session and the zip helper.
+- **keydump struct** (`masterkey/dump.go`): the vault carries the engine kind so restore can construct without the local table. The `Browser` field becomes the canonical key (it was the display name), a `Kind` string field is added (values `chromium` / `chromium-yandex` / `chromium-opera`, mapped to/from the internal enum by an explicit bijection so a reordered enum can't silently corrupt), and `DumpVersion` is bumped to "2". The format is designed fresh — `ReadJSON` rejects other versions and there are no backward-compat shims for pre-redesign dumps. `UserDataDir` and `Profiles` remain informational. The keys stay `V10` / `V11` / `V20` (Chromium-only; Firefox keys are out of scope, §9).
+- **`browser/keydump.go`**: `BuildDump` records the key and kind; the overlay `ApplyDump` (which mutates locally-discovered browsers) is replaced by `BuildFromDump`, which synthesizes a `BrowserConfig` per vault and builds the engine directly — no `platformBrowsers()` dependency. It resolves the data via the subdir convention or, for a hand-copied folder, the supplied dir as a single browser's root (§5). This is the mechanical form of §4.
+- **`archive`** reuses the engine's per-category source resolution through a new `ArchiveSources` accessor — each source path is kept slash-canonical so the forward-slash zip entry name falls out directly — plus the existing locked-file session. The flattening `CompressDir` helper is unfit (it drops the layout and deletes the source), so `archive` uses a new layout-preserving `ZipDir`, and `restore --data-zip` a Zip-Slip-safe `Unzip`.
 - **cmd layer**: drop the `keys` parent; add `dumpkeys`, `archive`, `restore` as siblings of `dump` / `list` / `version`.
 - **Cross-cutting (orthogonal to the taxonomy)**: a Chromium-import password CSV format (`name,url,username,password,note`, #602) and category-aware credential prompting so a no-decryption request never asks for a password (#570).
 
@@ -103,6 +104,13 @@ Working backwards from the chosen surface:
 3. keydump vault identity: **option 1A** — `Browser` becomes the canonical key and a `Kind` field is added (§7).
 4. Verb names are final: `archive` and `restore`.
 
+### Refinements (2026-06-06)
+
+5. Archive layout is the subdir convention `<browser-key>/<User Data layout>` (multi-browser); `restore` is dual-mode — that layout, or a single hand-copied `User Data` root selected by `-b` (§5).
+6. `archive` always includes each profile's `Preferences` marker (required for restore's profile discovery) and the installation's `Local State` (fidelity only — restore decrypts from `keys.json` and never reads it; §5).
+7. No backward compatibility: the dump format is designed fresh, with no shims for pre-redesign artifacts.
+8. Delivery order: `archive` (#607) lands first as an independent PR (it stands alone — its output also feeds the current overlay `restore` for same-OS browsers); the self-describing cross-platform `restore` (#606) follows.
+
 ## 9. Non-goals / deferred
 
 - Firefox / Safari key export (Firefox keys are per-profile NSS; Safari has no portable key).
diff --git a/utils/fileutil/fileutil.go b/utils/fileutil/fileutil.go
index f21ab5a..46b5ce0 100644
--- a/utils/fileutil/fileutil.go
+++ b/utils/fileutil/fileutil.go
@@ -3,9 +3,12 @@ package fileutil
 import (
 	"archive/zip"
 	"bytes"
+	"errors"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
+	"strings"
 )
 
 // FileExists checks if the file exists in the provided path.
@@ -88,3 +91,102 @@ func writeFile(buffer *bytes.Buffer, filename string) error {
 
 	return nil
 }
+
+// ZipDir writes every file under srcDir into a new zip at zipPath, preserving the relative directory
+// layout with forward-slash entry names. Unlike CompressDir it neither flattens names nor deletes the
+// source — it is the producer side of cross-host archive transport.
+func ZipDir(zipPath, srcDir string) error {
+	out, err := os.Create(zipPath)
+	if err != nil {
+		return fmt.Errorf("create %s: %w", zipPath, err)
+	}
+	defer func() { _ = out.Close() }()
+
+	zw := zip.NewWriter(out)
+	walkErr := filepath.WalkDir(srcDir, func(p string, d os.DirEntry, walkErr error) error {
+		if walkErr != nil {
+			return walkErr
+		}
+		if d.IsDir() {
+			return nil
+		}
+		rel, err := filepath.Rel(srcDir, p)
+		if err != nil {
+			return err
+		}
+		w, err := zw.Create(filepath.ToSlash(rel))
+		if err != nil {
+			return err
+		}
+		src, err := os.Open(p) //nolint:gosec // G122: staging tree is created and populated by us
+		if err != nil {
+			return err
+		}
+		defer func() { _ = src.Close() }()
+		_, err = io.Copy(w, src)
+		return err
+	})
+	if walkErr != nil {
+		_ = zw.Close()
+		return fmt.Errorf("zip %s: %w", srcDir, walkErr)
+	}
+	if err := zw.Close(); err != nil {
+		return fmt.Errorf("close zip %s: %w", zipPath, err)
+	}
+	return nil
+}
+
+// Unzip extracts zipPath into destDir, rejecting any entry whose path would escape destDir (Zip-Slip)
+// since a transported archive is not fully trusted.
+func Unzip(zipPath, destDir string) error {
+	r, err := zip.OpenReader(zipPath)
+	if err != nil {
+		return fmt.Errorf("open zip %s: %w", zipPath, err)
+	}
+	defer func() { _ = r.Close() }()
+
+	root := filepath.Clean(destDir)
+	for _, f := range r.File {
+		target := filepath.Join(root, filepath.FromSlash(f.Name))
+		if target != root && !strings.HasPrefix(target, root+string(os.PathSeparator)) {
+			return fmt.Errorf("zip entry %q escapes destination", f.Name)
+		}
+		if f.FileInfo().IsDir() {
+			if err := os.MkdirAll(target, 0o755); err != nil {
+				return err
+			}
+			continue
+		}
+		if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil {
+			return err
+		}
+		if err := writeZipEntry(f, target); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func writeZipEntry(f *zip.File, target string) error {
+	rc, err := f.Open()
+	if err != nil {
+		return err
+	}
+	defer func() { _ = rc.Close() }()
+
+	out, err := os.OpenFile(target, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0o600)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = out.Close() }()
+
+	for {
+		_, err := io.CopyN(out, rc, 1<<20)
+		if errors.Is(err, io.EOF) {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+	}
+}
diff --git a/utils/fileutil/fileutil_zip_test.go b/utils/fileutil/fileutil_zip_test.go
new file mode 100644
index 0000000..9d144af
--- /dev/null
+++ b/utils/fileutil/fileutil_zip_test.go
@@ -0,0 +1,88 @@
+package fileutil
+
+import (
+	"archive/zip"
+	"bytes"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestZipDirUnzip_RoundTrip(t *testing.T) {
+	src := t.TempDir()
+	files := map[string][]byte{
+		"empty.txt":               {},
+		"small.txt":               []byte("hello"),
+		"Default/Network/Cookies": []byte("cookie-bytes"),
+		"sub/big.bin":             bytes.Repeat([]byte("A"), 3<<20), // 3 MiB: exercises the chunked copy loop
+	}
+	for rel, data := range files {
+		p := filepath.Join(src, filepath.FromSlash(rel))
+		if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(p, data, 0o600); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	zipPath := filepath.Join(t.TempDir(), "out.zip")
+	if err := ZipDir(zipPath, src); err != nil {
+		t.Fatalf("ZipDir: %v", err)
+	}
+
+	zr, err := zip.OpenReader(zipPath)
+	if err != nil {
+		t.Fatalf("open zip: %v", err)
+	}
+	for _, f := range zr.File {
+		if strings.Contains(f.Name, `\`) {
+			t.Errorf("zip entry name must be forward-slash, got %q", f.Name)
+		}
+	}
+	if err := zr.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	dst := t.TempDir()
+	if err := Unzip(zipPath, dst); err != nil {
+		t.Fatalf("Unzip: %v", err)
+	}
+	for rel, want := range files {
+		got, err := os.ReadFile(filepath.Join(dst, filepath.FromSlash(rel)))
+		if err != nil {
+			t.Errorf("missing %s after Unzip: %v", rel, err)
+			continue
+		}
+		if !bytes.Equal(got, want) {
+			t.Errorf("%s: content mismatch (got %d bytes, want %d)", rel, len(got), len(want))
+		}
+	}
+}
+
+func TestUnzip_RejectsZipSlip(t *testing.T) {
+	zipPath := filepath.Join(t.TempDir(), "evil.zip")
+	f, err := os.Create(zipPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	zw := zip.NewWriter(f)
+	w, err := zw.Create("../escape.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := w.Write([]byte("pwned")); err != nil {
+		t.Fatal(err)
+	}
+	if err := zw.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := Unzip(zipPath, t.TempDir()); err == nil {
+		t.Fatal("Unzip must reject an entry that escapes the destination")
+	}
+}