Files: Move… opens a folder picker, and a move across filesystems copies then removes

The picker walks the machine like the tab does — back, forward, up, breadcrumbs, a path
box, a new folder — and "Move here" puts the file or folder in the folder being looked
at; it says why it can't when it can't (already here, into itself, a name clash). POST
/api/files/move is a rename when the two ends share a filesystem and otherwise a task:
on a NAS every move between datasets is a different filesystem, and a rename there is
EXDEV. The copy is built under a hidden temporary name beside its destination, renamed
into place once complete, and only then is the original removed, so a failure or a
cancel leaves the original as it was. Modes, times, symlinks and, as root, owners are kept.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

internal/api/server.go

@@ -80,6 +80,7 @@ type Server struct {
 	fsLocal     files.FS
 	fsSudo      files.FS // nil without passwordless sudo
 	thumbs      *thumbSvc
+	self        string // this binary, for helpers run as tasks
 	nodes       *nodes.Manager
 	fingerprint string
 	version     string
@@ -99,6 +100,7 @@ func New(cfg *config.Config, sessions *auth.Sessions, mgr *term.Manager, col *me
 	if err != nil {
 		self = "hamlab"
 	}
+	s.self = self
 	s.space = space.New(self, filepath.Join(cfg.DataDir(), "space"))
 	s.thumbs = newThumbSvc(cfg.DataDir(), self)
 	s.hostName() // read it once now so the first request doesn't have to
@@ -301,6 +303,7 @@ func (s *Server) routes() *http.ServeMux {
 	m.HandleFunc("POST /api/files/mkdir", s.auth(s.filesMkdir))
 	m.HandleFunc("POST /api/files/touch", s.auth(s.filesTouch))
 	m.HandleFunc("POST /api/files/rename", s.auth(s.filesRename))
+	m.HandleFunc("POST /api/files/move", s.auth(s.filesMove))
 	m.HandleFunc("POST /api/files/delete", s.auth(s.filesDelete))
 	m.HandleFunc("POST /api/files/chmod", s.auth(s.filesChmod))
 	m.HandleFunc("GET /api/files/thumb", s.auth(s.filesThumb))
@@ -2054,6 +2057,57 @@ func (s *Server) filesRename(w http.ResponseWriter, r *http.Request) {
 	})
 }
 
+// filesMove: POST {path, to} — to is the full destination path. A rename when the two
+// ends share a filesystem (204); otherwise the copy-and-remove runs as a task (202 with the
+// task), since a folder between datasets can take as long as it takes.
+func (s *Server) filesMove(w http.ResponseWriter, r *http.Request) {
+	fsys, ok := s.fsFor(w, r)
+	if !ok {
+		return
+	}
+	var body struct{ Path, To string }
+	if err := json.NewDecoder(io.LimitReader(r.Body, 64<<10)).Decode(&body); err != nil {
+		jsonErr(w, 400, "bad request")
+		return
+	}
+	from, err := files.Clean(body.Path)
+	if err != nil {
+		jsonErr(w, 400, err.Error())
+		return
+	}
+	to, err := files.Clean(body.To)
+	if err != nil {
+		jsonErr(w, 400, err.Error())
+		return
+	}
+	if from == to {
+		jsonErr(w, 400, "it is already there")
+		return
+	}
+	if files.Inside(from, to) {
+		jsonErr(w, 400, "a folder can't be moved into itself")
+		return
+	}
+	err = fsys.Rename(r.Context(), from, to)
+	if err == nil {
+		log.Printf("files: move %s -> %s (from %s)", from, to, clientIP(r))
+		w.WriteHeader(204)
+		return
+	}
+	if !files.IsCrossDevice(err) {
+		fsErr(w, err)
+		return
+	}
+	cmd := files.MoveCmd(context.Background(), fsys, s.self, from, to)
+	t, err := s.tasks.Start("files:move", "move "+filepath.Base(from)+" to "+filepath.Dir(to), cmd)
+	if err != nil {
+		jsonErr(w, 500, err.Error())
+		return
+	}
+	log.Printf("files: move %s -> %s across filesystems as task %s (from %s)", from, to, t.ID, clientIP(r))
+	jsonOK(w, 202, t.Snapshot(false))
+}
+
 func (s *Server) filesDelete(w http.ResponseWriter, r *http.Request) {
 	s.filesOp(w, r, func(fsys files.FS, body map[string]any, p string) error {
 		rec, _ := body["recursive"].(bool)

internal/files/files.go

@@ -15,6 +15,7 @@ import (
 	"io"
 	"os"
 	"os/exec"
+	"os/signal"
 	"os/user"
 	"path/filepath"
 	"sort"
@@ -62,6 +63,7 @@ type FS interface {
 	Mkdir(ctx context.Context, path string) error
 	Touch(ctx context.Context, path string) error
 	Rename(ctx context.Context, from, to string) error
+	Move(ctx context.Context, from, to string, progress io.Writer) error // Rename, or across filesystems a copy and a removal; long, so callers run it as a task
 	Delete(ctx context.Context, path string, recursive bool) error
 	Chmod(ctx context.Context, path string, perm os.FileMode) error
 }
@@ -385,6 +387,30 @@ func (s Sudo) Touch(ctx context.Context, path string) error {
 func (s Sudo) Rename(ctx context.Context, from, to string) error {
 	return s.runJSON(ctx, nil, "rename", from, to)
 }
+
+// Move as root: the helper does the copying and talks on stdout.
+func (s Sudo) Move(ctx context.Context, from, to string, progress io.Writer) error {
+	c := s.cmd(ctx, "move", from, to)
+	c.Stdout = progress
+	var errb strings.Builder
+	c.Stderr = &errb
+	if err := c.Run(); err != nil {
+		if msg := strings.TrimSpace(errb.String()); msg != "" {
+			return errors.New(msg)
+		}
+		return err
+	}
+	return nil
+}
+
+// MoveCmd is the command a task runs for a long move: this binary's helper, as root when
+// the backend is.
+func MoveCmd(ctx context.Context, fsys FS, self, from, to string) *exec.Cmd {
+	if s, ok := fsys.(Sudo); ok {
+		return s.cmd(ctx, "move", from, to)
+	}
+	return exec.CommandContext(ctx, self, "fs", "move", from, to)
+}
 func (s Sudo) Delete(ctx context.Context, path string, recursive bool) error {
 	if recursive {
 		return s.runJSON(ctx, nil, "delete", "-r", path)
@@ -399,7 +425,7 @@ func (s Sudo) Chmod(ctx context.Context, path string, perm os.FileMode) error {
 func Helper(args []string, stdin io.Reader, stdout io.Writer, stderr io.Writer) int {
 	fail := func(err error) int { fmt.Fprintln(stderr, err.Error()); return 1 }
 	if len(args) < 2 {
-		return fail(errors.New("usage: hamlab fs <list|stat|read|write|mkdir|touch|rename|delete|chmod> …"))
+		return fail(errors.New("usage: hamlab fs <list|stat|read|write|mkdir|touch|rename|move|delete|chmod> …"))
 	}
 	ctx := context.Background()
 	var l Local
@@ -452,7 +478,7 @@ func Helper(args []string, stdin io.Reader, stdout io.Writer, stderr io.Writer)
 				return fail(err)
 			}
 		}
-	case "rename":
+	case "rename", "move":
 		from, err := clean(1)
 		if err != nil {
 			return fail(err)
@@ -461,6 +487,15 @@ func Helper(args []string, stdin io.Reader, stdout io.Writer, stderr io.Writer)
 		if err != nil {
 			return fail(err)
 		}
+		if op == "move" {
+			// A cancelled task is a SIGTERM: stop copying and take the partial copy away.
+			mctx, stop := signal.NotifyContext(ctx, syscall.SIGTERM, syscall.SIGINT)
+			defer stop()
+			if err := l.Move(mctx, from, to, stdout); err != nil {
+				return fail(err)
+			}
+			return 0
+		}
 		if err := l.Rename(ctx, from, to); err != nil {
 			return fail(err)
 		}

internal/files/move.go

@@ -0,0 +1,198 @@
+package files
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"syscall"
+)
+
+// IsCrossDevice reports a rename refused because the two ends are on different
+// filesystems — on a NAS that is every move between datasets. The Sudo backend only has
+// the helper's words for it.
+func IsCrossDevice(err error) bool {
+	return errors.Is(err, syscall.EXDEV) || (err != nil && strings.Contains(err.Error(), "cross-device"))
+}
+
+// Inside reports whether to lies within from — a folder cannot be moved into itself.
+func Inside(from, to string) bool {
+	return to == from || strings.HasPrefix(to, strings.TrimSuffix(from, "/")+"/")
+}
+
+// Move is Rename, and across filesystems a copy and a removal. The copy is built under a
+// hidden temporary name beside where it will land and renamed into place only once it is
+// complete, and the source is removed only after that: a failure part-way, or a cancel,
+// leaves the source exactly as it was. Progress goes to w, a line at a time, for the task
+// output that a long move is watched through.
+func (Local) Move(ctx context.Context, from, to string, w io.Writer) error {
+	if protected[from] {
+		return errors.New("refusing to move " + from)
+	}
+	if Inside(from, to) {
+		return errors.New("a folder can't be moved into itself")
+	}
+	if _, err := os.Lstat(to); err == nil {
+		return errors.New("destination exists")
+	}
+	err := os.Rename(from, to)
+	if err == nil || !IsCrossDevice(err) {
+		return err
+	}
+	return moveByCopy(ctx, from, to, w)
+}
+
+// moveByCopy is the slow path: copy, rename into place, remove the original.
+func moveByCopy(ctx context.Context, from, to string, w io.Writer) error {
+	st, err := os.Lstat(from)
+	if err != nil {
+		return err
+	}
+	tmp := filepath.Join(filepath.Dir(to), "."+filepath.Base(to)+".hamlab-moving")
+	_ = os.RemoveAll(tmp) // a previous attempt that died
+	fmt.Fprintf(w, "%s is on another filesystem: copying, then removing the original\n", filepath.Dir(to))
+	p := &progress{w: w}
+	if err := copyPath(ctx, from, tmp, st, p); err != nil {
+		fmt.Fprintln(w, "copy failed; removing the partial copy, the original is untouched")
+		_ = os.RemoveAll(tmp)
+		return err
+	}
+	if err := os.Rename(tmp, to); err != nil {
+		_ = os.RemoveAll(tmp)
+		return err
+	}
+	fmt.Fprintf(w, "copied %s; removing the original\n", p.String())
+	if err := os.RemoveAll(from); err != nil {
+		return fmt.Errorf("copied to %s, but the original could not be removed: %w", to, err)
+	}
+	fmt.Fprintf(w, "moved %s to %s\n", from, to)
+	return nil
+}
+
+type progress struct {
+	w           io.Writer
+	files       int64
+	bytes       int64
+	shownFiles  int64
+	shownBytes  int64
+	lastPrinted bool
+}
+
+func (p *progress) add(files, bytes int64) {
+	p.files += files
+	p.bytes += bytes
+	if p.files-p.shownFiles >= 500 || p.bytes-p.shownBytes >= 512<<20 {
+		fmt.Fprintf(p.w, "copying… %s\n", p.String())
+		p.shownFiles, p.shownBytes = p.files, p.bytes
+	}
+}
+
+func (p *progress) String() string {
+	return fmt.Sprintf("%d files, %s", p.files, fmtSize(p.bytes))
+}
+
+func fmtSize(b int64) string {
+	const unit = 1024
+	if b < unit {
+		return fmt.Sprintf("%d B", b)
+	}
+	div, exp := int64(unit), 0
+	for n := b / unit; n >= unit && exp < 4; n /= unit {
+		div *= unit
+		exp++
+	}
+	return fmt.Sprintf("%.1f %ciB", float64(b)/float64(div), "KMGTP"[exp])
+}
+
+// copyPath copies one entry of any kind, recursively for a directory, keeping mode, times
+// and — when running as root — ownership. Devices, pipes and sockets are refused: a copy
+// of one is not the thing itself.
+func copyPath(ctx context.Context, src, dst string, st os.FileInfo, p *progress) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	mode := st.Mode()
+	switch {
+	case mode&os.ModeSymlink != 0:
+		target, err := os.Readlink(src)
+		if err != nil {
+			return err
+		}
+		if err := os.Symlink(target, dst); err != nil {
+			return err
+		}
+		chown(dst, st)
+		p.add(1, 0)
+		return nil
+	case mode.IsDir():
+		if err := os.Mkdir(dst, mode.Perm()|0o700); err != nil { // writable while it fills, exact mode after
+			return err
+		}
+		ents, err := os.ReadDir(src)
+		if err != nil {
+			return err
+		}
+		for _, e := range ents {
+			lst, err := e.Info()
+			if err != nil {
+				return err
+			}
+			if err := copyPath(ctx, filepath.Join(src, e.Name()), filepath.Join(dst, e.Name()), lst, p); err != nil {
+				return err
+			}
+		}
+		chown(dst, st)
+		if err := os.Chmod(dst, mode.Perm()); err != nil {
+			return err
+		}
+		return os.Chtimes(dst, st.ModTime(), st.ModTime())
+	case mode.IsRegular():
+		n, err := copyFile(src, dst, st)
+		if err != nil {
+			return err
+		}
+		p.add(1, n)
+		return nil
+	default:
+		return fmt.Errorf("%s: can't copy a device, pipe or socket", src)
+	}
+}
+
+func copyFile(src, dst string, st os.FileInfo) (int64, error) {
+	in, err := os.Open(src)
+	if err != nil {
+		return 0, err
+	}
+	defer in.Close()
+	out, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_EXCL, st.Mode().Perm())
+	if err != nil {
+		return 0, err
+	}
+	n, err := io.Copy(out, in)
+	if err != nil {
+		out.Close()
+		return n, err
+	}
+	if err := out.Close(); err != nil {
+		return n, err
+	}
+	chown(dst, st)
+	if err := os.Chmod(dst, st.Mode().Perm()); err != nil { // umask has no say
+		return n, err
+	}
+	return n, os.Chtimes(dst, st.ModTime(), st.ModTime())
+}
+
+// chown keeps the owner when this process may set one; an ordinary user's copy is the
+// user's, which is what a rename would have left anyway.
+func chown(dst string, st os.FileInfo) {
+	if os.Geteuid() != 0 {
+		return
+	}
+	if sys, ok := st.Sys().(*syscall.Stat_t); ok {
+		_ = os.Lchown(dst, int(sys.Uid), int(sys.Gid))
+	}
+}

internal/files/move_test.go

@@ -0,0 +1,168 @@
+package files
+
+import (
+	"context"
+	"errors"
+	"os"
+	"path/filepath"
+	"strings"
+	"syscall"
+	"testing"
+	"time"
+)
+
+func TestInside(t *testing.T) {
+	for _, c := range []struct {
+		from, to string
+		want     bool
+	}{
+		{"/a/b", "/a/b", true}, {"/a/b", "/a/b/c", true}, {"/a/b", "/a/bc", false}, {"/a/b", "/a", false}, {"/", "/x", true},
+	} {
+		if got := Inside(c.from, c.to); got != c.want {
+			t.Errorf("Inside(%q, %q) = %v, want %v", c.from, c.to, got, c.want)
+		}
+	}
+}
+
+func TestIsCrossDevice(t *testing.T) {
+	if !IsCrossDevice(&os.LinkError{Op: "rename", Old: "/a", New: "/b", Err: syscall.EXDEV}) {
+		t.Fatal("the kernel's EXDEV")
+	}
+	if !IsCrossDevice(errors.New("rename /a /b: invalid cross-device link")) {
+		t.Fatal("the helper's words for it")
+	}
+	if IsCrossDevice(errors.New("permission denied")) || IsCrossDevice(nil) {
+		t.Fatal("anything else is not")
+	}
+}
+
+// The copy path, exercised directly: a tree with nested folders, a symlink, an odd mode
+// and old mtimes lands whole under the new name, and the original is gone only then.
+func TestMoveByCopy(t *testing.T) {
+	root := t.TempDir()
+	src := filepath.Join(root, "src", "album")
+	if err := os.MkdirAll(filepath.Join(src, "sub", "deep"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	old := time.Date(2020, 1, 2, 3, 4, 5, 0, time.UTC)
+	write := func(p, s string, mode os.FileMode) {
+		if err := os.WriteFile(p, []byte(s), mode); err != nil {
+			t.Fatal(err)
+		}
+		_ = os.Chmod(p, mode)
+		_ = os.Chtimes(p, old, old)
+	}
+	write(filepath.Join(src, "a.txt"), "hello", 0o644)
+	write(filepath.Join(src, "sub", "deep", "b.bin"), strings.Repeat("x", 100000), 0o600)
+	write(filepath.Join(src, "run.sh"), "#!/bin/sh\n", 0o755)
+	if err := os.Symlink("a.txt", filepath.Join(src, "link")); err != nil {
+		t.Fatal(err)
+	}
+	_ = os.Chtimes(filepath.Join(src, "sub"), old, old)
+
+	dst := filepath.Join(root, "dst", "moved")
+	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	var out strings.Builder
+	if err := moveByCopy(context.Background(), src, dst, &out); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Lstat(src); !os.IsNotExist(err) {
+		t.Fatal("the original is still there")
+	}
+	if b, _ := os.ReadFile(filepath.Join(dst, "a.txt")); string(b) != "hello" {
+		t.Fatal("a.txt")
+	}
+	if st, err := os.Stat(filepath.Join(dst, "sub", "deep", "b.bin")); err != nil || st.Size() != 100000 || st.Mode().Perm() != 0o600 || !st.ModTime().Equal(old) {
+		t.Fatalf("b.bin: %v %v", st, err)
+	}
+	if st, _ := os.Stat(filepath.Join(dst, "run.sh")); st.Mode().Perm() != 0o755 {
+		t.Fatal("mode lost")
+	}
+	if target, err := os.Readlink(filepath.Join(dst, "link")); err != nil || target != "a.txt" {
+		t.Fatal("symlink not copied as a symlink")
+	}
+	if st, _ := os.Stat(filepath.Join(dst, "sub")); !st.ModTime().Equal(old) {
+		t.Fatal("folder mtime lost")
+	}
+	if left, _ := filepath.Glob(filepath.Join(root, "dst", ".*hamlab-moving*")); len(left) != 0 {
+		t.Fatal("temporary copy left behind")
+	}
+	if !strings.Contains(out.String(), "moved ") || !strings.Contains(out.String(), "4 files") {
+		t.Fatalf("progress said: %q", out.String())
+	}
+}
+
+// A failure part-way leaves the original as it was and no partial copy.
+func TestMoveByCopyFailsClean(t *testing.T) {
+	root := t.TempDir()
+	src := filepath.Join(root, "src")
+	if err := os.MkdirAll(src, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(src, "a"), []byte("a"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := syscall.Mkfifo(filepath.Join(src, "pipe"), 0o644); err != nil {
+		t.Skip("no fifos here")
+	}
+	dst := filepath.Join(root, "dst")
+	err := moveByCopy(context.Background(), src, dst, &strings.Builder{})
+	if err == nil || !strings.Contains(err.Error(), "pipe") {
+		t.Fatalf("expected the pipe to be refused, got %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(src, "a")); err != nil {
+		t.Fatal("the original was touched")
+	}
+	if _, err := os.Lstat(dst); !os.IsNotExist(err) {
+		t.Fatal("a partial copy was left")
+	}
+	if left, _ := filepath.Glob(filepath.Join(root, ".*hamlab-moving*")); len(left) != 0 {
+		t.Fatal("temporary copy left behind")
+	}
+	// a cancel is the same story
+	if err := os.Remove(filepath.Join(src, "pipe")); err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	if err := moveByCopy(ctx, src, dst, &strings.Builder{}); err == nil {
+		t.Fatal("a cancelled move must fail")
+	}
+	if _, err := os.Stat(filepath.Join(src, "a")); err != nil {
+		t.Fatal("the original was touched by a cancel")
+	}
+}
+
+// Move on one filesystem is a rename: nothing is copied, and the guards hold.
+func TestMoveSameFilesystem(t *testing.T) {
+	root := t.TempDir()
+	src := filepath.Join(root, "f")
+	if err := os.WriteFile(src, []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	var l Local
+	var out strings.Builder
+	if err := l.Move(context.Background(), src, filepath.Join(root, "g"), &out); err != nil {
+		t.Fatal(err)
+	}
+	if out.Len() != 0 {
+		t.Fatal("a rename has nothing to say")
+	}
+	if _, err := os.Stat(filepath.Join(root, "g")); err != nil {
+		t.Fatal("not renamed")
+	}
+	if err := l.Move(context.Background(), root, filepath.Join(root, "inside"), &out); err == nil {
+		t.Fatal("into itself")
+	}
+	if err := l.Move(context.Background(), filepath.Join(root, "g"), filepath.Join(root, "g"), &out); err == nil {
+		t.Fatal("onto itself")
+	}
+	if err := os.WriteFile(filepath.Join(root, "h"), nil, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := l.Move(context.Background(), filepath.Join(root, "g"), filepath.Join(root, "h"), &out); err == nil || !strings.Contains(err.Error(), "exists") {
+		t.Fatalf("onto an existing file: %v", err)
+	}
+}

web/src/Files.tsx

@@ -1,5 +1,5 @@
 import { DragEvent, useCallback, useEffect, useMemo, useRef, useState } from 'react'
-import { api, FileEntry, FileInfo, ThumbStatus } from './api'
+import { api, FileEntry, FileInfo, TaskInfo, ThumbStatus } from './api'
 import { fmtBytes } from './fmt'
 import { Btn, Loading, Spinner, askText, askYes, setUnsaved, toast, useEscape } from './ui'
 import { useHashSel } from './hashsel'
@@ -25,6 +25,95 @@ function icon(e: FileEntry): string {
 
 type Sort = 'name' | 'size' | 'mtime'
 const PREVIEWS_KEY = 'hamlab.files.previews'
+const byName = (a: FileEntry, b: FileEntry) => a.name.localeCompare(b.name, undefined, { numeric: true, sensitivity: 'base' })
+// A name is one path segment. ("../x" and "a/b" would quietly act somewhere else.)
+const okName = (n?: string | null): n is string => { const t = n?.trim(); if (!t) return false; if (t.includes('/') || t === '.' || t === '..') { toast('a name can\'t contain / or be . or .. — use Move… to put it elsewhere', 'err'); return false } return true }
+
+// ---- move: walk to the destination, then "Move here" ----
+function MovePicker({ item, from, sudo, hidden, onClose, onMoved }: { item: FileEntry; from: string; sudo: boolean; hidden: boolean; onClose: () => void; onMoved: (task?: TaskInfo) => void }) {
+  const src = join(from, item.name)
+  const isFolder = item.type === 'dir' && !item.target
+  const [hist, setHist] = useState<string[]>([from]) // where the picker has been, for back and forward
+  const [at, setAt] = useState(0)
+  const dir = hist[at]
+  const [entries, setEntries] = useState<FileEntry[] | null>(null)
+  const [err, setErr] = useState('')
+  const [pathInput, setPathInput] = useState(from)
+  const [busy, setBusy] = useState(false)
+  const load = useCallback(async (p: string) => {
+    setEntries(null); setErr('')
+    try { const l = await api.files(p, sudo); setEntries(l.entries) } catch (e) { setErr(e instanceof Error ? e.message : 'failed'); setEntries([]) }
+  }, [sudo])
+  useEffect(() => { setPathInput(dir); load(dir) }, [dir, load])
+  useEscape(onClose)
+  const go = (p: string) => {
+    p = p.trim().replace(/\/+$/, '') || '/'
+    if (!p.startsWith('/') || p === dir) return
+    setHist((h) => [...h.slice(0, at + 1), p]); setAt(at + 1)
+  }
+  const up = () => { if (dir !== '/') go(dir.slice(0, dir.lastIndexOf('/')) || '/') }
+  const folders = (entries ?? []).filter((e) => e.type === 'dir' && (hidden || !e.name.startsWith('.'))).sort(byName)
+  const crumbs = dir === '/' ? [] : dir.slice(1).split('/')
+  const dest = join(dir, item.name)
+  const why = dir === from ? 'it is already here'
+    : isFolder && (dir === src || dir.startsWith(src + '/')) ? 'a folder can\'t move into itself'
+    : (entries ?? []).some((e) => e.name === item.name) ? `something called ${item.name} is already there` : ''
+  const move = async () => {
+    setBusy(true)
+    try {
+      const t = await api.fileMove(src, dest, sudo)
+      if (t) toast(`${dir} is on another filesystem — copying ${item.name} there, then removing it here`, 'info')
+      else toast(`moved ${item.name} to ${dir}`)
+      onMoved(t)
+    } catch (e) { toast(`move — ${e instanceof Error ? e.message : 'failed'}`, 'err'); setBusy(false) }
+  }
+  const mkdir = async () => {
+    const n = await askText('New folder name')
+    if (!okName(n)) return
+    try { await api.fileMkdir(join(dir, n.trim()), sudo); go(join(dir, n.trim())) } catch (e) { toast(`create folder — ${e instanceof Error ? e.message : 'failed'}`, 'err') }
+  }
+  return (
+    <div className="modal-back" onClick={onClose}>
+      <div className="modal mover" onClick={(e) => e.stopPropagation()}>
+        <h3>Move {isFolder ? 'folder ' : ''}<span className="mono">{item.name}</span></h3>
+        <div className="mover-nav">
+          <button className="icon-btn" title="back" disabled={at === 0} onClick={() => setAt(at - 1)}>‹</button>
+          <button className="icon-btn" title="forward" disabled={at >= hist.length - 1} onClick={() => setAt(at + 1)}>›</button>
+          <button className="icon-btn" title="up one level" disabled={dir === '/'} onClick={up}>↑</button>
+          <form className="crumbs" onSubmit={(e) => { e.preventDefault(); go(pathInput) }}>
+            <button type="button" className="crumb" onClick={() => go('/')}>/</button>
+            {crumbs.map((c, i) => <button type="button" key={i} className="crumb" onClick={() => go('/' + crumbs.slice(0, i + 1).join('/'))}>{c}</button>)}
+            <input className="path-input" value={pathInput} onChange={(e) => setPathInput(e.target.value)} onBlur={() => setPathInput(dir)} spellCheck={false} autoCapitalize="off" autoCorrect="off" />
+          </form>
+        </div>
+        <div className="mover-list">
+          {entries === null && <Loading label="Listing…" />}
+          {err && <div className="error" style={{ margin: 10 }}>{err}</div>}
+          {folders.map((e) => {
+            const self = dir === from && e.name === item.name
+            return (
+              <div key={e.name} className={'mover-row' + (self ? ' self' : '')} onClick={() => { if (!self) go(join(dir, e.name)) }}>
+                <span className="ficon">{e.target ? '🔗' : '📁'}</span>
+                <span className="fname">{e.name}</span>
+                {self && <span className="muted small">this is what's moving</span>}
+              </div>
+            )
+          })}
+          {entries !== null && folders.length === 0 && !err && <div className="muted small" style={{ padding: 12 }}>No folders here — “Move here” puts it in this one.</div>}
+        </div>
+        <div className="modal-foot">
+          <div className="svc-actions">
+            <button className="btn" onClick={mkdir}>+ folder</button>
+            <span className="spacer" />
+            <button className="btn" onClick={onClose}>Cancel</button>
+            <Btn className="btn on" disabled={!!why || entries === null} busy={busy} onClick={move}>Move here</Btn>
+          </div>
+          <div className="muted small mono mover-dest">{why || `→ ${dest}`}</div>
+        </div>
+      </div>
+    </div>
+  )
+}
 
 // ---- previews ----
 
@@ -184,6 +273,8 @@ export default function Files({ onOpenInTerminal }: { onOpenInTerminal?: (cmd: s
   const [pathInput, setPathInput] = useState(path)
   const [open, setOpen] = useState<string | null>(null)
   const [menu, setMenu] = useState<string | null>(null)
+  const [moving, setMoving] = useState<FileEntry | null>(null)
+  const [moveTask, setMoveTask] = useState<TaskInfo | null>(null)
   const [upload, setUpload] = useState<{ name: string; pct: number; n: number; of: number } | null>(null)
   const [drag, setDrag] = useState(false)
   const fileInput = useRef<HTMLInputElement>(null)
@@ -227,12 +318,10 @@ export default function Files({ onOpenInTerminal }: { onOpenInTerminal?: (cmd: s
   const act = async (label: string, fn: () => Promise<unknown>): Promise<boolean> => {
     try { await fn(); toast(label); await load(); return true } catch (e) { toast(`${label} — ${e instanceof Error ? e.message : 'failed'}`, 'err'); return false }
   }
-  // A name is one path segment. ("../x" and "a/b" would quietly act somewhere else.)
-  const okName = (n?: string | null): n is string => { const t = n?.trim(); if (!t) return false; if (t.includes('/') || t === '.' || t === '..') { toast('a name can\'t contain / or be . or .. — use Move… to put it elsewhere', 'err'); return false } return true }
   const mkdir = async () => { const n = await askText('New folder name'); if (okName(n)) act(`created ${n.trim()}`, () => api.fileMkdir(join(path, n.trim()), sudo)) }
   const touch = async () => { const n = await askText('New file name'); if (okName(n) && await act(`created ${n.trim()}`, () => api.fileTouch(join(path, n.trim()), sudo))) setOpen(join(path, n.trim())) } // opened only once it exists
   const rename = async (e: FileEntry) => { const n = await askText('Rename to', e.name); if (okName(n) && n.trim() !== e.name) act(`renamed to ${n.trim()}`, () => api.fileRename(join(path, e.name), join(path, n.trim()), sudo)) }
-  const move = async (e: FileEntry) => { const n = await askText('Move to (absolute path)', join(path, e.name)); if (n?.trim() && n.trim() !== join(path, e.name)) act(`moved to ${n.trim()}`, () => api.fileRename(join(path, e.name), n.trim(), sudo)) }
+  const move = (e: FileEntry) => setMoving(e)
   const chmod = async (e: FileEntry) => { const n = await askText(`Permissions for ${e.name} (octal)`, e.perm); if (n?.trim() && n.trim() !== e.perm) act(`chmod ${n.trim()} ${e.name}`, () => api.fileChmod(join(path, e.name), n.trim(), sudo)) }
   const del = async (e: FileEntry) => {
     const full = join(path, e.name)
@@ -292,6 +381,8 @@ export default function Files({ onOpenInTerminal }: { onOpenInTerminal?: (cmd: s
       </div>
 
       {previews && <ThumbNote st={thumbs} sudo={sudo} onChanged={() => readThumbs(true)} />}
+      {moveTask && <TaskOutput id={moveTask.id} onDone={(t) => { load(); if (t.exit_code === 0 && !t.error) toast(`${moveTask.title}: done`); else toast(`${moveTask.title}: failed`, 'err') }} />}
+      {moveTask && <div className="thumb-note"><button className="btn" onClick={() => setMoveTask(null)}>Hide output</button></div>}
       {upload && <div className="upload-bar"><Spinner /> {upload.of > 1 ? `${upload.n}/${upload.of} · ` : ''}{upload.name} · {upload.pct}%<div className="meter"><div className="fill" style={{ width: `${upload.pct}%` }} /></div></div>}
       {err && <div className="error" style={{ padding: '6px 12px' }}>{err}{/permission denied/i.test(err) && !sudo && <> · <button className="link" onClick={() => setSudo(true)}>retry as root</button></>}</div>}
 
@@ -330,6 +421,7 @@ export default function Files({ onOpenInTerminal }: { onOpenInTerminal?: (cmd: s
         {entries !== null && shown.length === 0 && !err && <div className="muted" style={{ padding: 12 }}>{q ? 'Nothing matches.' : 'Empty folder.'}{!hidden && entries.some((e) => e.name.startsWith('.')) ? ' (hidden files not shown)' : ''}</div>}
       </div>
       {drag && <div className="drop-hint">Drop to upload into {path}</div>}
+      {moving && <MovePicker item={moving} from={path} sudo={sudo} hidden={hidden} onClose={() => setMoving(null)} onMoved={(t) => { setMoving(null); if (t) setMoveTask(t); load() }} />}
     </div>
   )
 }

web/src/api.ts

@@ -316,6 +316,8 @@ export const api = {
   fileMkdir: (path: string, sudo: boolean) => req<void>('POST', `/api/files/mkdir${sudo ? '?sudo=1' : ''}`, { path }),
   fileTouch: (path: string, sudo: boolean) => req<void>('POST', `/api/files/touch${sudo ? '?sudo=1' : ''}`, { path }),
   fileRename: (path: string, to: string, sudo: boolean) => req<void>('POST', `/api/files/rename${sudo ? '?sudo=1' : ''}`, { path, to }),
+  // a rename when the ends share a filesystem (nothing back), otherwise the copy-and-remove runs as a task (the task back)
+  fileMove: (path: string, to: string, sudo: boolean) => req<TaskInfo | undefined>('POST', `/api/files/move${sudo ? '?sudo=1' : ''}`, { path, to }),
   fileDelete: (path: string, recursive: boolean, sudo: boolean) => req<void>('POST', `/api/files/delete${sudo ? '?sudo=1' : ''}`, { path, recursive }),
   fileChmod: (path: string, mode: string, sudo: boolean) => req<void>('POST', `/api/files/chmod${sudo ? '?sudo=1' : ''}`, { path, mode }),
   storage: () => req<{ devices: StorageDevice[]; zfs: ZFSInfo; smartctl: boolean }>('GET', '/api/storage'),

web/src/styles.css

@@ -371,6 +371,18 @@ h2.section { margin: 0; font-size: 13px; font-weight: 600; color: var(--muted);
 .fthumb.video::after { content: '▶'; position: absolute; right: 2px; bottom: 2px; font-size: 9px; line-height: 1; padding: 2px 3px; border-radius: 3px; background: rgba(0,0,0,.6); color: #fff; }
 .fthumb .ficon { font-size: 18px; }
 .thumb-note { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; margin: 6px 10px 0; }
+/* move: the folder picker */
+.modal.mover { width: min(560px, 100%); height: min(76vh, 100%); overflow: hidden; }
+.mover-nav { display: flex; align-items: center; gap: 2px; }
+.mover-nav .icon-btn { font-size: 18px; min-width: 30px; line-height: 1; }
+.mover-nav .icon-btn:disabled { opacity: .3; }
+.mover-nav .crumbs { flex: 1; min-width: 0; margin-left: 4px; }
+.modal.mover > .mover-list { flex: 1 1 auto; min-height: 80px; overflow-y: auto; margin: 0 -16px; border-top: 1px solid var(--border); }
+.mover-row { display: flex; align-items: center; gap: 8px; padding: 9px 16px; cursor: pointer; border-bottom: 1px solid var(--border); min-height: 38px; }
+.mover-row:hover { background: var(--bg3); }
+.mover-row.self { opacity: .5; cursor: default; }
+.mover-row .fname { flex: 1; }
+.mover-dest { overflow-wrap: anywhere; }
 .thumb-note .btn { padding-top: 3px; padding-bottom: 3px; }
 .files-bar .task-out { margin: 6px 10px 0; max-height: 160px; }
 @media (max-width: 800px) {