diff --git a/modules/clipmenu/README.md b/modules/clipmenu/README.md
new file mode 100644
index 0000000..6243582
--- /dev/null
+++ b/modules/clipmenu/README.md
@@ -0,0 +1,69 @@
+# clipmenu
+
+The clipboard manager as a module (novox/hq ADR 0208, research 026/04).
+
+- Installs `clipmenu` from the official repositories. It brings `clipnotify`, `xsel`, `xdotool` and
+  `dmenu` as its own dependencies.
+- Claims the mesh's `node-clipboard` seat and serves its verbs `history` and `copy`. Requires
+  `x11-display` on its own machine.
+- **Declares `rofi-greenclip` absent** (ADR 0180). This module replaces it.
+- Starts `clipmenud` **once per session**, from the session's start (the `xinitrc` slot `normal`).
+  It is not a user unit as well. Its packaged unit needs user-scoped units (mesh-host #72, not
+  merged), and the session start alone is one starter.
+- Binds `$mod+period` to `clipmenu`, as its own i3 drop-in (`50-clipmenu.conf`). clipmenu shows the
+  history through `dmenu`, the seat command of `node-launcher`, so it looks like every other menu.
+- Its settings are environment contributions (ADR 0203), read by the daemon, the menu and the tools
+  alike:
+  - `CM_SELECTIONS=clipboard`: what was copied, not every highlighted word. The found greenclip did
+    the same.
+  - `CM_MAX_CLIPS=500`: how many clips are kept.
+  - `CM_HISTLENGTH=15`: how many lines the menu shows.
+
+## Tools
+
+| tool | does |
+|---|---|
+| `node-clipboard.history` | the history, newest first, each entry once with its id, first line, time, size and text (cut) |
+| `node-clipboard.copy` | put text on the clipboard; it enters the history like any copy |
+| `clipmenu_paste` | what the clipboard holds now |
+| `clipmenu_clear` | forget the history; the daemon's locks stay |
+| `clipmenu_delete` | forget one entry, by id or first line |
+
+The history is read from clipmenu's own store, in the account's runtime directory, under clipmenu's
+own lock, so a copy arriving meanwhile is neither lost nor half-written. `copy` hands the text to an
+owner (`xsel`) under the account's service manager. As a child of the tools runtime, the clipboard
+would empty whenever the runtime restarted.
+
+## What it improves on what was found
+
+- **No AUR package.** greenclip came from the user repository. clipmenu is in the official one.
+- **Started once.** greenclip was started by the window manager on both workstations, and on the
+  desktop by an enabled user unit as well.
+- **No absolute home path** in any configuration. greenclip's named one.
+- **The history does not outlive a reboot.** greenclip kept it in `~/.cache`, so every password ever
+  copied stayed on disk. clipmenu keeps it in the runtime directory, which is memory.
+- **One menu.** The history appears in the launcher's own menu, through the seat's `dmenu` command,
+  instead of a theme from a cloned theme repository.
+
+## What it leaves as found
+
+- `~/.config/greenclip.toml` and greenclip's history, `~/.cache/greenclip.history`.
+- On the desktop: greenclip's enabled user unit link
+  (`~/.config/systemd/user/default.target.wants/greenclip.service`). It dangles once the package is
+  gone.
+
+## Migration (ADR 0182)
+
+1. After the first push, delete `~/.config/greenclip.toml` and `~/.cache/greenclip.history`.
+2. On the desktop: `systemctl --user disable greenclip.service`, before the push if you can. The
+   package's removal takes the unit file with it.
+3. Until the `i3` module carries the main configuration, the found `exec --no-startup-id greenclip
+   daemon` and `$mod+period` lines stay in `~/.config/i3/config`. i3 reports `$mod+period` as bound
+   twice. The `i3` module's configuration carries neither.
+
+## Blockers
+
+- `node-clipboard`, `x11-display` and the `xinitrc` slot are ADR 0208's. Until the controller knows
+  them, `mctl` reads them as unknown.
+- `CM_*` reach the session through `node-env` (ADR 0203), so the account's environment module must
+  be assigned too. Without it clipmenu runs on its defaults: both selections, 1000 clips, 8 lines.
diff --git a/modules/clipmenu/cmd/clipmenu-tools/args.go b/modules/clipmenu/cmd/clipmenu-tools/args.go
new file mode 100644
index 0000000..9b5dfcf
--- /dev/null
+++ b/modules/clipmenu/cmd/clipmenu-tools/args.go
@@ -0,0 +1,97 @@
+// Reading a tool's arguments: JSON numbers arrive as float64, and a missing argument is its default.
+// The same in every desktop module that carries it.
+package main
+
+import (
+	"fmt"
+	"math"
+	"strings"
+	"time"
+)
+
+// text is a string argument, trimmed; required says an empty one is refused.
+func text(args map[string]any, key string, required bool) (string, error) {
+	v, present := args[key]
+	if !present || v == nil {
+		if required {
+			return "", fmt.Errorf("%s is required", key)
+		}
+		return "", nil
+	}
+	s, ok := v.(string)
+	if !ok {
+		return "", fmt.Errorf("%s is a string, not %T", key, v)
+	}
+	s = strings.TrimSpace(s)
+	if s == "" && required {
+		return "", fmt.Errorf("%s is required", key)
+	}
+	return s, nil
+}
+
+// whole is a whole-number argument within [least, most], or def when absent.
+func whole(args map[string]any, key string, def, least, most int) (int, error) {
+	v, present := args[key]
+	if !present || v == nil {
+		return def, nil
+	}
+	f, ok := v.(float64)
+	if !ok {
+		if i, isInt := v.(int); isInt {
+			f = float64(i)
+		} else {
+			return 0, fmt.Errorf("%s is a number, not %T", key, v)
+		}
+	}
+	if f != math.Trunc(f) {
+		return 0, fmt.Errorf("%s is a whole number, not %v", key, f)
+	}
+	n := int(f)
+	if n < least || n > most {
+		return 0, fmt.Errorf("%s is %d; it is between %d and %d", key, n, least, most)
+	}
+	return n, nil
+}
+
+// flag is a boolean argument, or def when absent.
+func flag(args map[string]any, key string, def bool) (bool, error) {
+	v, present := args[key]
+	if !present || v == nil {
+		return def, nil
+	}
+	b, ok := v.(bool)
+	if !ok {
+		return false, fmt.Errorf("%s is true or false, not %T", key, v)
+	}
+	return b, nil
+}
+
+// texts is a list-of-strings argument.
+func texts(args map[string]any, key string) ([]string, error) {
+	v, present := args[key]
+	if !present || v == nil {
+		return nil, nil
+	}
+	list, ok := v.([]any)
+	if !ok {
+		if ss, isStrings := v.([]string); isStrings {
+			return ss, nil
+		}
+		return nil, fmt.Errorf("%s is a list of strings, not %T", key, v)
+	}
+	out := make([]string, 0, len(list))
+	for i, item := range list {
+		s, ok := item.(string)
+		if !ok {
+			return nil, fmt.Errorf("%s[%d] is a string, not %T", key, i, item)
+		}
+		out = append(out, s)
+	}
+	return out, nil
+}
+
+// seconds is a timeout argument in seconds, defaulted and bounded below the runtime's call limit.
+func seconds(args map[string]any, key string, def, most int) (time.Duration, error) {
+	n, err := whole(args, key, def, 1, most)
+	return time.Duration(n) * time.Second, err
+}
diff --git a/modules/clipmenu/cmd/clipmenu-tools/clipboard.go b/modules/clipmenu/cmd/clipmenu-tools/clipboard.go
new file mode 100644
index 0000000..b025030
--- /dev/null
+++ b/modules/clipmenu/cmd/clipmenu-tools/clipboard.go
@@ -0,0 +1,348 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"os"
+	"os/user"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"syscall"
+	"time"
+)
+
+const (
+	mostCopy  = 1 << 20
+	mostPaste = 64 << 10
+	// majorVersion is clipmenu's store layout: <dir>/clipmenu.<major>.<user>/.
+	majorVersion = 6
+)
+
+// account is the user clipmenu's store is named for.
+func account() string {
+	for _, k := range []string{"USER", "MESH_OPERATOR_ACCOUNT", "LOGNAME"} {
+		if v := strings.TrimSpace(os.Getenv(k)); v != "" {
+			return v
+		}
+	}
+	if u, err := user.Current(); err == nil {
+		return u.Username
+	}
+	return ""
+}
+
+// storeDir is where clipmenud keeps the history: CM_DIR, else the account's runtime directory.
+func storeDir(s Session) (string, error) {
+	base := os.Getenv("CM_DIR")
+	if base == "" {
+		base = s.RuntimeDir
+	}
+	if base == "" {
+		return "", fmt.Errorf("%w: the account's runtime directory, where the clipboard history lives, is missing (the account is not logged in)", ErrNoBus)
+	}
+	return filepath.Join(base, fmt.Sprintf("clipmenu.%d.%s", majorVersion, account())), nil
+}
+
+// cksum is POSIX cksum(1) of data: clipmenu names each entry's file by the cksum of its first line
+// followed by a newline, as "<crc> <length>".
+func cksum(data []byte) string {
+	var crc uint32
+	step := func(b byte) {
+		crc ^= uint32(b) << 24
+		for i := 0; i < 8; i++ {
+			if crc&0x80000000 != 0 {
+				crc = crc<<1 ^ 0x04C11DB7
+			} else {
+				crc <<= 1
+			}
+		}
+	}
+	for _, b := range data {
+		step(b)
+	}
+	for n := len(data); n != 0; n >>= 8 {
+		step(byte(n))
+	}
+	return fmt.Sprintf("%d %d", ^crc, len(data))
+}
+
+func entryID(line string) string { return cksum([]byte(line + "\n")) }
+
+// Entry is one clip in the history.
+type Entry struct {
+	ID        string `json:"id"`
+	Line      string `json:"line"`
+	At        string `json:"at"`
+	Bytes     int    `json:"bytes"`
+	Text      string `json:"text,omitempty"`
+	Truncated bool   `json:"truncated,omitempty"`
+	at        int64
+}
+
+// HistoryResult is what node-clipboard.history answers.
+type HistoryResult struct {
+	Collecting bool    `json:"collecting"`
+	Store      string  `json:"store"`
+	Total      int     `json:"total"`
+	Entries    []Entry `json:"entries"`
+}
+
+// readStore reads clipmenu's line cache: one "<nanoseconds> <first line>" per copy, oldest first, a
+// line repeated when the same thing was copied again. The newest copy of each line wins.
+func readStore(dir string) ([]Entry, error) {
+	f, err := os.Open(filepath.Join(dir, "line_cache"))
+	if errors.Is(err, os.ErrNotExist) {
+		return []Entry{}, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	latest := map[string]int64{}
+	scan := bufio.NewScanner(f)
+	scan.Buffer(make([]byte, 64<<10), 1<<20)
+	for scan.Scan() {
+		stamp, line, ok := strings.Cut(scan.Text(), " ")
+		if !ok {
+			continue
+		}
+		ns, err := strconv.ParseInt(stamp, 10, 64)
+		if err != nil {
+			continue
+		}
+		if ns >= latest[line] {
+			latest[line] = ns
+		}
+	}
+	out := make([]Entry, 0, len(latest))
+	for line, ns := range latest {
+		out = append(out, Entry{ID: entryID(line), Line: line, at: ns, At: time.Unix(0, ns).Format(time.RFC3339)})
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].at > out[j].at })
+	return out, scan.Err()
+}
+
+// History is the clipboard's history, newest first.
+func History(limit, maxBytes int) (HistoryResult, error) {
+	dir, err := storeDir(findEnvironment())
+	if err != nil {
+		return HistoryResult{}, err
+	}
+	entries, err := readStore(dir)
+	if err != nil {
+		return HistoryResult{}, err
+	}
+	out := HistoryResult{Collecting: len(processesOf("clipmenud")) > 0, Store: dir, Total: len(entries), Entries: []Entry{}}
+	for i, e := range entries {
+		if i == limit {
+			break
+		}
+		if info, err := os.Stat(filepath.Join(dir, e.ID)); err == nil {
+			e.Bytes = int(info.Size())
+			if maxBytes > 0 {
+				raw, _ := os.ReadFile(filepath.Join(dir, e.ID))
+				if len(raw) > maxBytes {
+					raw, e.Truncated = raw[:maxBytes], true
+				}
+				e.Text = string(raw)
+			}
+		}
+		out.Entries = append(out.Entries, e)
+	}
+	return out, nil
+}
+
+// CopyResult is what node-clipboard.copy answers.
+type CopyResult struct {
+	Bytes int    `json:"bytes"`
+	Unit  string `json:"unit"`
+}
+
+// Copy puts text on the clipboard. The clipboard is owned by a process until another copies, so the
+// owner (xsel) runs under the account's service manager, not as a child of this tool.
+func Copy(text string) (CopyResult, error) {
+	if len(text) == 0 {
+		return CopyResult{}, errors.New("text is empty; to empty the clipboard's history, clipmenu_clear")
+	}
+	if len(text) > mostCopy {
+		return CopyResult{}, fmt.Errorf("%d bytes; the clipboard takes at most %d here", len(text), mostCopy)
+	}
+	s, err := findSession()
+	if err != nil {
+		return CopyResult{}, err
+	}
+	if s.RuntimeDir == "" {
+		return CopyResult{}, fmt.Errorf("%w: no runtime directory to hand the text over in", ErrNoBus)
+	}
+	// Handed over in a file only the account can read, which the owner reads and removes.
+	f, err := os.CreateTemp(s.RuntimeDir, "clipmenu-copy-")
+	if err != nil {
+		return CopyResult{}, err
+	}
+	if _, err := f.WriteString(text); err != nil {
+		f.Close()
+		os.Remove(f.Name())
+		return CopyResult{}, err
+	}
+	f.Close()
+	unit := uniqueUnit("clipmenu-copy")
+	script := `xsel --nodetach --input --clipboard < "$0" & sleep 1; rm -f "$0"; wait`
+	if err := s.detach(unit, "/bin/sh", "-c", script, f.Name()); err != nil {
+		os.Remove(f.Name())
+		return CopyResult{}, err
+	}
+	return CopyResult{Bytes: len(text), Unit: unit + ".service"}, nil
+}
+
+// PasteResult is what clipmenu_paste answers.
+type PasteResult struct {
+	Text      string `json:"text"`
+	Bytes     int    `json:"bytes"`
+	Truncated bool   `json:"truncated,omitempty"`
+}
+
+// Paste reads the clipboard now.
+func Paste() (PasteResult, error) {
+	s, err := findSession()
+	if err != nil {
+		return PasteResult{}, err
+	}
+	r, err := s.run(5*time.Second, "", "xsel", "--output", "--clipboard")
+	if err != nil {
+		return PasteResult{}, err
+	}
+	if r.Code != 0 {
+		return PasteResult{}, fmt.Errorf("xsel: %s", strings.TrimSpace(r.Stderr))
+	}
+	out := PasteResult{Text: r.Stdout, Bytes: len(r.Stdout), Truncated: r.Truncated}
+	if len(out.Text) > mostPaste {
+		out.Text, out.Truncated = out.Text[:mostPaste], true
+	}
+	return out, nil
+}
+
+// ChangeResult is what clear and delete answer.
+type ChangeResult struct {
+	Removed   int `json:"removed"`
+	Remaining int `json:"remaining"`
+}
+
+// withStoreLock holds clipmenu's own lock on its store, the one clipmenud and clipdel take, while
+// change runs, so a copy arriving meanwhile is neither lost nor half-written.
+func withStoreLock(dir string, change func() error) error {
+	lock, err := os.OpenFile(filepath.Join(dir, "lock"), os.O_CREATE|os.O_WRONLY, 0o600)
+	if err != nil {
+		return err
+	}
+	defer lock.Close()
+	deadline := time.Now().Add(2 * time.Second)
+	for {
+		err := syscall.Flock(int(lock.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
+		if err == nil {
+			break
+		}
+		if time.Now().After(deadline) {
+			return fmt.Errorf("the clipboard store is locked by clipmenud and did not come free within 2s")
+		}
+		time.Sleep(50 * time.Millisecond)
+	}
+	defer syscall.Flock(int(lock.Fd()), syscall.LOCK_UN)
+	return change()
+}
+
+func storeOf() (string, error) {
+	dir, err := storeDir(findEnvironment())
+	if err != nil {
+		return "", err
+	}
+	if _, err := os.Stat(dir); errors.Is(err, os.ErrNotExist) {
+		return "", fmt.Errorf("there is no clipboard history at %s: clipmenud has not run in this login", dir)
+	}
+	return dir, nil
+}
+
+// Clear forgets every entry and its text, keeping the store and its locks (clipdel's own clear
+// removes the directory, the daemon's lock with it).
+func Clear() (ChangeResult, error) {
+	dir, err := storeOf()
+	if err != nil {
+		return ChangeResult{}, err
+	}
+	var out ChangeResult
+	err = withStoreLock(dir, func() error {
+		entries, err := readStore(dir)
+		if err != nil {
+			return err
+		}
+		out.Removed = len(entries)
+		files, err := os.ReadDir(dir)
+		if err != nil {
+			return err
+		}
+		for _, f := range files {
+			switch f.Name() {
+			case "lock", "session_lock", "line_cache":
+				continue
+			}
+			if f.Type().IsRegular() {
+				if err := os.Remove(filepath.Join(dir, f.Name())); err != nil {
+					return err
+				}
+			}
+		}
+		return os.WriteFile(filepath.Join(dir, "line_cache"), nil, 0o600)
+	})
+	return out, err
+}
+
+// Delete forgets one entry, by id or by its first line.
+func Delete(id, line string) (ChangeResult, error) {
+	if (id == "") == (line == "") {
+		return ChangeResult{}, errors.New("give the entry's id or its line, one of the two")
+	}
+	dir, err := storeOf()
+	if err != nil {
+		return ChangeResult{}, err
+	}
+	var out ChangeResult
+	err = withStoreLock(dir, func() error {
+		raw, err := os.ReadFile(filepath.Join(dir, "line_cache"))
+		if err != nil && !errors.Is(err, os.ErrNotExist) {
+			return err
+		}
+		var kept []string
+		for _, l := range strings.Split(strings.TrimRight(string(raw), "\n"), "\n") {
+			if l == "" {
+				continue
+			}
+			_, text, _ := strings.Cut(l, " ")
+			if text == line || (id != "" && entryID(text) == id) {
+				out.Removed++
+				_ = os.Remove(filepath.Join(dir, entryID(text)))
+				continue
+			}
+			kept = append(kept, l)
+		}
+		if out.Removed == 0 {
+			return fmt.Errorf("no entry %s%s in the clipboard history", id, line)
+		}
+		content := strings.Join(kept, "\n")
+		if content != "" {
+			content += "\n"
+		}
+		tmp := filepath.Join(dir, ".line_cache.mesh")
+		if err := os.WriteFile(tmp, []byte(content), 0o600); err != nil {
+			return err
+		}
+		return os.Rename(tmp, filepath.Join(dir, "line_cache"))
+	})
+	if err != nil {
+		return ChangeResult{}, err
+	}
+	entries, _ := readStore(dir)
+	out.Remaining = len(entries)
+	return out, nil
+}
diff --git a/modules/clipmenu/cmd/clipmenu-tools/clipboard_test.go b/modules/clipmenu/cmd/clipmenu-tools/clipboard_test.go
new file mode 100644
index 0000000..058b8ae
--- /dev/null
+++ b/modules/clipmenu/cmd/clipmenu-tools/clipboard_test.go
@@ -0,0 +1,163 @@
+package main
+
+import (
+	"errors"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+const nobody = 4194400
+
+func TestEntryIdsAreWhatClipmenuNamesItsFiles(t *testing.T) {
+	for _, line := range []string{"hello", "", "two words (3 lines)", "ünïcode ✓", strings.Repeat("x", 300)} {
+		out, err := exec.Command("bash", "-c", `cksum <<< "$1"`, "_", line).Output()
+		if err != nil {
+			t.Skip("bash or cksum is missing here")
+		}
+		if got, want := entryID(line), strings.TrimSpace(string(out)); got != want {
+			t.Errorf("%q: %s, cksum says %s", line, got, want)
+		}
+	}
+}
+
+// store makes clipmenu's store as clipmenud leaves it, for the account the tools run as.
+func store(t *testing.T, clips map[string]string, order ...string) string {
+	t.Helper()
+	fakeMachine(t)
+	runtime := filepath.Join(runUserDir, strconv.Itoa(os.Getuid()))
+	t.Setenv("USER", "op")
+	t.Setenv("CM_DIR", "")
+	dir := filepath.Join(runtime, "clipmenu.6.op")
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(runtime, "bus"), nil, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	var cache strings.Builder
+	for i, line := range order {
+		cache.WriteString(strconv.FormatInt(1_700_000_000_000_000_000+int64(i)*1_000_000_000, 10) + " " + line + "\n")
+		if err := os.WriteFile(filepath.Join(dir, entryID(line)), []byte(clips[line]), 0o600); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := os.WriteFile(filepath.Join(dir, "line_cache"), []byte(cache.String()), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	return dir
+}
+
+func TestTheHistoryIsNewestFirstOnceEachWithItsText(t *testing.T) {
+	store(t, map[string]string{"first": "first", "second (2 lines)": "second\nline two"}, "first", "second (2 lines)", "first")
+	fakeProcess(t, nobody, "clipmenud")
+	h, err := History(10, 4096)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !h.Collecting || h.Total != 2 || h.Entries[0].Line != "first" || h.Entries[1].Text != "second\nline two" || h.Entries[1].Bytes != 15 {
+		t.Fatalf("%+v", h)
+	}
+	if h, _ := History(1, 3); len(h.Entries) != 1 || h.Entries[0].Text != "fir" || !h.Entries[0].Truncated {
+		t.Fatalf("limited and cut: %+v", h)
+	}
+	if h, _ := History(10, 0); h.Entries[0].Text != "" || h.Entries[0].Bytes != 5 {
+		t.Fatalf("without text: %+v", h)
+	}
+}
+
+func TestAnEntryIsDeletedByIdOrLineWithItsText(t *testing.T) {
+	dir := store(t, map[string]string{"a": "a", "b": "b", "c": "c"}, "a", "b", "c", "a")
+	r, err := Delete(entryID("a"), "")
+	if err != nil || r.Removed != 2 || r.Remaining != 2 {
+		t.Fatalf("by id, both copies: %+v, %v", r, err)
+	}
+	if _, err := os.Stat(filepath.Join(dir, entryID("a"))); !errors.Is(err, os.ErrNotExist) {
+		t.Fatal("the text stayed")
+	}
+	if r, err := Delete("", "b"); err != nil || r.Removed != 1 || r.Remaining != 1 {
+		t.Fatalf("by line: %+v, %v", r, err)
+	}
+	if _, err := Delete("", "zzz"); err == nil {
+		t.Fatal("a missing entry was reported deleted")
+	}
+	if _, err := Delete("x", "y"); err == nil {
+		t.Fatal("both an id and a line were accepted")
+	}
+	cache, _ := os.ReadFile(filepath.Join(dir, "line_cache"))
+	if !strings.HasSuffix(string(cache), " c\n") || strings.Count(string(cache), "\n") != 1 {
+		t.Fatalf("line cache: %q", cache)
+	}
+}
+
+func TestClearForgetsEverythingButKeepsTheDaemonsLocks(t *testing.T) {
+	dir := store(t, map[string]string{"a": "a", "b": "b"}, "a", "b")
+	if err := os.WriteFile(filepath.Join(dir, "session_lock"), nil, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	r, err := Clear()
+	if err != nil || r.Removed != 2 {
+		t.Fatalf("%+v, %v", r, err)
+	}
+	left, _ := os.ReadDir(dir)
+	var names []string
+	for _, f := range left {
+		names = append(names, f.Name())
+	}
+	if strings.Join(names, ",") != "line_cache,lock,session_lock" {
+		t.Fatalf("left: %v", names)
+	}
+}
+
+func TestCopyHandsTheTextToAnOwnerUnderTheAccountsServiceManager(t *testing.T) {
+	store(t, nil)
+	fakeProcess(t, nobody, "i3", "DISPLAY=:1")
+	bin := fakeBinaries(t, map[string]string{"systemctl": "true", "systemd-run": `echo "$*" > "$LOG"; for last; do :; done; cat "$last" > "$LOG.text"`})
+	t.Setenv("LOG", filepath.Join(bin, "log"))
+	r, err := Copy("secret-free text")
+	if err != nil || r.Bytes != 16 || !strings.HasPrefix(r.Unit, "clipmenu-copy-") {
+		t.Fatalf("%+v, %v", r, err)
+	}
+	asked, _ := os.ReadFile(filepath.Join(bin, "log"))
+	if !strings.Contains(string(asked), "--setenv=DISPLAY=:1 -- /bin/sh -c xsel --nodetach --input --clipboard") {
+		t.Fatalf("asked: %s", asked)
+	}
+	handed, _ := os.ReadFile(filepath.Join(bin, "log.text"))
+	if string(handed) != "secret-free text" {
+		t.Fatalf("handed over: %q", handed)
+	}
+	if _, err := Copy(""); err == nil {
+		t.Fatal("empty text was accepted")
+	}
+}
+
+func TestPasteReadsTheClipboardOrSaysThereIsNoSession(t *testing.T) {
+	fakeMachine(t)
+	if _, err := Paste(); !errors.Is(err, ErrNoSession) {
+		t.Fatal(err)
+	}
+	fakeProcess(t, nobody, "i3", "DISPLAY=:1")
+	fakeBinaries(t, map[string]string{"xsel": `[ "$*" = "--output --clipboard" ] && printf 'on the clipboard'`})
+	p, err := Paste()
+	if err != nil || p.Text != "on the clipboard" || p.Bytes != 16 {
+		t.Fatalf("%+v, %v", p, err)
+	}
+}
+
+func TestWithoutAStoreTheChangesSayWhy(t *testing.T) {
+	fakeMachine(t)
+	runtime := filepath.Join(runUserDir, strconv.Itoa(os.Getuid()))
+	if err := os.MkdirAll(runtime, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("USER", "op")
+	if _, err := Clear(); err == nil || !strings.Contains(err.Error(), "clipmenud has not run") {
+		t.Fatal(err)
+	}
+	if h, err := History(5, 0); err != nil || h.Total != 0 || h.Collecting {
+		t.Fatalf("an empty history: %+v, %v", h, err)
+	}
+}
diff --git a/modules/clipmenu/cmd/clipmenu-tools/main.go b/modules/clipmenu/cmd/clipmenu-tools/main.go
new file mode 100644
index 0000000..e8e9212
--- /dev/null
+++ b/modules/clipmenu/cmd/clipmenu-tools/main.go
@@ -0,0 +1,90 @@
+// clipmenu's Go tools bundle (novox/hq ADR 0188, ADR 0193, ADR 0208): its implementation of
+// node-clipboard's verbs `history` and `copy`, and its own tools, served by the node's runtime as the
+// operator account. The history is read from clipmenu's own store in the account's runtime directory;
+// the clipboard itself is the X session's.
+package main
+
+import (
+	"fmt"
+	"os"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+func main() {
+	if err := stdio.Serve("", tools()); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+func tools() []stdio.Tool {
+	return []stdio.Tool{
+		{
+			Name: "node-clipboard.history",
+			Description: "What the operator copied, newest first: each entry's id, its first line, when, its size " +
+				"and its text (each cut at max_bytes). Whether the clipboard daemon is collecting.",
+			Input: map[string]any{
+				"limit":     map[string]any{"type": "integer", "description": "at most this many entries (default 20, at most 500)"},
+				"max_bytes": map[string]any{"type": "integer", "description": "cut each entry's text at this many bytes; 0 leaves the text out (default 4096, at most 65536)"},
+			},
+			Run: func(args map[string]any) (any, error) {
+				limit, err := whole(args, "limit", 20, 1, 500)
+				if err != nil {
+					return nil, err
+				}
+				most, err := whole(args, "max_bytes", 4096, 0, 65536)
+				if err != nil {
+					return nil, err
+				}
+				return History(limit, most)
+			},
+		},
+		{
+			Name: "node-clipboard.copy",
+			Description: "Put text on the operator's clipboard, as if they had copied it; it enters the history " +
+				"like any copy. Answers how many bytes.",
+			Input: map[string]any{
+				"type": "object",
+				"properties": map[string]any{
+					"text": map[string]any{"type": "string", "description": fmt.Sprintf("the text (at most %d bytes)", mostCopy)},
+				},
+				"required": []string{"text"},
+			},
+			Run: func(args map[string]any) (any, error) {
+				t, ok := args["text"].(string)
+				if !ok {
+					return nil, fmt.Errorf("text is required, as a string")
+				}
+				return Copy(t)
+			},
+		},
+		{
+			Name:        "clipmenu_paste",
+			Description: "What the operator's clipboard holds right now, as text (cut at 64 KiB, said in truncated).",
+			Run:         func(map[string]any) (any, error) { return Paste() },
+		},
+		{
+			Name:        "clipmenu_clear",
+			Description: "Forget the whole clipboard history. What is on the clipboard now stays there.",
+			Run:         func(map[string]any) (any, error) { return Clear() },
+		},
+		{
+			Name: "clipmenu_delete",
+			Description: "Forget one entry of the clipboard history, by its id as the history answers it, or by " +
+				"its first line exactly.",
+			Input: map[string]any{
+				"id":   map[string]any{"type": "string", "description": "the entry's id"},
+				"line": map[string]any{"type": "string", "description": "the entry's first line, exactly"},
+			},
+			Run: func(args map[string]any) (any, error) {
+				id, err := text(args, "id", false)
+				if err != nil {
+					return nil, err
+				}
+				line, _ := args["line"].(string)
+				return Delete(id, line)
+			},
+		},
+	}
+}
diff --git a/modules/clipmenu/cmd/clipmenu-tools/manifest_helpers_test.go b/modules/clipmenu/cmd/clipmenu-tools/manifest_helpers_test.go
new file mode 100644
index 0000000..d4fb76d
--- /dev/null
+++ b/modules/clipmenu/cmd/clipmenu-tools/manifest_helpers_test.go
@@ -0,0 +1,175 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// The module's manifest, read the way the catalogue reads it, for the manifest tests. The same in
+// every desktop module that carries it.
+
+type manifest struct {
+	Module       string           `json:"module"`
+	Version      string           `json:"version"`
+	Capabilities []string         `json:"capabilities"`
+	Requires     []string         `json:"requires"`
+	Claims       []claim          `json:"claims"`
+	Seats        []any            `json:"seats"`
+	Tools        []string         `json:"tools"`
+	Environment  *environment     `json:"environment"`
+	Shell        []shellCode      `json:"shell"`
+	Resources    []map[string]any `json:"resources"`
+	Build        struct {
+		Artifacts []map[string]any `json:"artifacts"`
+	} `json:"build"`
+}
+
+type claim struct {
+	Name   string   `json:"name"`
+	Scope  string   `json:"scope"`
+	Serves []string `json:"serves"`
+}
+
+type environment struct {
+	Variables map[string]string `json:"variables"`
+	Path      []map[string]any  `json:"path"`
+}
+
+type shellCode struct {
+	For  string `json:"for"`
+	Slot string `json:"slot"`
+	Code string `json:"code"`
+}
+
+func readManifest(t *testing.T) manifest {
+	t.Helper()
+	raw, err := os.ReadFile(filepath.Join("..", "..", "module.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	dec := json.NewDecoder(strings.NewReader(string(raw)))
+	dec.DisallowUnknownFields()
+	var m manifest
+	if err := dec.Decode(&m); err != nil {
+		t.Fatalf("module.json: %v", err)
+	}
+	return m
+}
+
+func (m manifest) resource(t *testing.T, id string) map[string]any {
+	t.Helper()
+	for _, r := range m.Resources {
+		if r["id"] == id {
+			return r
+		}
+	}
+	t.Fatalf("no resource %q", id)
+	return nil
+}
+
+func (m manifest) packages() (present, absent []string) {
+	for _, r := range m.Resources {
+		if r["type"] == "package" {
+			if r["absent"] == true {
+				absent = append(absent, r["package"].(string))
+			} else {
+				present = append(present, r["package"].(string))
+			}
+		}
+	}
+	return present, absent
+}
+
+// sameAsSource checks that a file resource's content is byte for byte the module's source file, so
+// the readable file in the repository is what the machine gets.
+func (m manifest) sameAsSource(t *testing.T, id, source string) {
+	t.Helper()
+	want, err := os.ReadFile(filepath.Join("..", "..", source))
+	if err != nil {
+		t.Fatal(err)
+	}
+	r := m.resource(t, id)
+	if r["type"] != "file" {
+		t.Fatalf("%s is a %v, not a file", id, r["type"])
+	}
+	if got, _ := r["content"].(string); got != string(want) {
+		t.Fatalf("resource %s's content is not %s: edit the source and copy it into module.json", id, source)
+	}
+	if r["owner"] != "${machine:account}" && !strings.HasPrefix(r["path"].(string), "/etc/") {
+		t.Fatalf("%s under the home is the account's", id)
+	}
+}
+
+// checkTheToolsAgree checks that the manifest lists the module's own tools exactly, that the bundle
+// serves each seat verb the claims promise as <seat>.<verb>, and that the Go bundle is declared.
+func checkTheToolsAgree(t *testing.T, m manifest) {
+	t.Helper()
+	own, seat := map[string]bool{}, map[string]bool{}
+	for _, tool := range tools() {
+		if strings.Contains(tool.Name, ".") {
+			seat[tool.Name] = true
+		} else {
+			own[tool.Name] = true
+		}
+		if strings.TrimSpace(tool.Description) == "" {
+			t.Errorf("%s has no description", tool.Name)
+		}
+	}
+	listed := map[string]bool{}
+	for _, name := range m.Tools {
+		listed[name] = true
+		if !own[name] {
+			t.Errorf("module.json lists %s, which the bundle does not serve", name)
+		}
+	}
+	for name := range own {
+		if !listed[name] {
+			t.Errorf("the bundle serves %s, which module.json does not list", name)
+		}
+		if !strings.HasPrefix(name, strings.ReplaceAll(m.Module, "-", "_")+"_") {
+			t.Errorf("%s is not prefixed with the module's name", name)
+		}
+	}
+	promised := map[string]bool{}
+	for _, c := range m.Claims {
+		for _, verb := range c.Serves {
+			promised[c.Name+"."+verb] = true
+			if !seat[c.Name+"."+verb] {
+				t.Errorf("the claim on %s promises %s, which the bundle does not serve", c.Name, verb)
+			}
+		}
+	}
+	for name := range seat {
+		if !promised[name] {
+			t.Errorf("the bundle serves %s, which no claim promises", name)
+		}
+	}
+	var bundle map[string]any
+	for _, a := range m.Build.Artifacts {
+		if a["kind"] == "bundle" {
+			bundle = a
+		}
+	}
+	if bundle == nil || bundle["language"] != "go" || bundle["system"] != "arch" ||
+		bundle["from"] != "cmd/"+m.Module+"-tools" || bundle["binary"] != m.Module+"-tools" {
+		t.Errorf("the Go tools bundle: %v", bundle)
+	}
+}
+
+// checkNoSecretsOrInstallationNames refuses what a catalogue manifest must never carry.
+func checkNoSecretsOrInstallationNames(t *testing.T) {
+	t.Helper()
+	raw, err := os.ReadFile(filepath.Join("..", "..", "module.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	s := strings.ToLower(string(raw))
+	for _, never := range []string{"/home/", "jochen", "g14", "shanks", "novox.be", "api_key", ".hal/", "greenclip daemon"} {
+		if strings.Contains(s, never) {
+			t.Errorf("module.json names %q", never)
+		}
+	}
+}
diff --git a/modules/clipmenu/cmd/clipmenu-tools/manifest_test.go b/modules/clipmenu/cmd/clipmenu-tools/manifest_test.go
new file mode 100644
index 0000000..e0adb4c
--- /dev/null
+++ b/modules/clipmenu/cmd/clipmenu-tools/manifest_test.go
@@ -0,0 +1,64 @@
+package main
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// clipmenu's shape (novox/hq ADR 0208, research 026/04): it claims node-clipboard serving history
+// and copy, requires the X display on its own machine, replaces greenclip, starts its daemon once
+// from the session's start, and binds its menu as an i3 drop-in through the launcher's dmenu command.
+
+func TestItClaimsTheClipboardSeatServingHistoryAndCopy(t *testing.T) {
+	m := readManifest(t)
+	if m.Module != "clipmenu" || m.Seats != nil {
+		t.Fatalf("module %q declares seats %v", m.Module, m.Seats)
+	}
+	if !reflect.DeepEqual(m.Claims, []claim{{Name: "node-clipboard", Scope: "node", Serves: []string{"history", "copy"}}}) {
+		t.Fatalf("claims: %+v", m.Claims)
+	}
+	if !reflect.DeepEqual(m.Requires, []string{"x11-display"}) {
+		t.Fatalf("requires: %v", m.Requires)
+	}
+	present, absent := m.packages()
+	if !reflect.DeepEqual(present, []string{"clipmenu"}) || !reflect.DeepEqual(absent, []string{"rofi-greenclip"}) {
+		t.Fatalf("packages: %v, absent %v", present, absent)
+	}
+}
+
+func TestTheDaemonStartsOnceFromTheSessionsStart(t *testing.T) {
+	m := readManifest(t)
+	if len(m.Shell) != 1 || m.Shell[0].For != "xinitrc" || m.Shell[0].Slot != "normal" {
+		t.Fatalf("%+v", m.Shell)
+	}
+	code := m.Shell[0].Code
+	if strings.Count(code, "\nclipmenud &\n") != 1 || strings.Contains(code, "greenclip") {
+		t.Fatalf("%q", code)
+	}
+	for _, r := range m.Resources {
+		if r["type"] == "service" || r["type"] == "process" {
+			t.Fatalf("a second start: %v", r)
+		}
+	}
+}
+
+func TestItsSettingsAreEnvironmentAndItsMenuIsTheLaunchersDmenu(t *testing.T) {
+	m := readManifest(t)
+	if !reflect.DeepEqual(m.Environment.Variables, map[string]string{"CM_SELECTIONS": "clipboard", "CM_MAX_CLIPS": "500", "CM_HISTLENGTH": "15"}) {
+		t.Fatalf("%v", m.Environment.Variables)
+	}
+	if _, set := m.Environment.Variables["CM_LAUNCHER"]; set {
+		t.Fatal("the launcher is clipmenu's default, dmenu: the seat's command")
+	}
+	m.sameAsSource(t, "i3-bindings", "files/i3/50-clipmenu.conf")
+	if c := m.resource(t, "i3-bindings")["content"].(string); !strings.Contains(c, "bindsym $mod+period exec --no-startup-id clipmenu") {
+		t.Fatalf("%s", c)
+	}
+}
+
+func TestTheToolsAgreeWithTheManifest(t *testing.T) {
+	m := readManifest(t)
+	checkTheToolsAgree(t, m)
+	checkNoSecretsOrInstallationNames(t)
+}
diff --git a/modules/clipmenu/cmd/clipmenu-tools/session.go b/modules/clipmenu/cmd/clipmenu-tools/session.go
new file mode 100644
index 0000000..dc21774
--- /dev/null
+++ b/modules/clipmenu/cmd/clipmenu-tools/session.go
@@ -0,0 +1,423 @@
+// The operator's graphical session, as a tool the node's runtime runs finds it (novox/hq ADR 0208).
+//
+// The runtime is a system service running as the operator account (ADR 0175): it has the account's
+// uid and none of the session's environment — no DISPLAY, no XAUTHORITY, no session bus. A tool that
+// draws on the screen or talks to the desktop's D-Bus must find them. It reads them from a process of
+// the account that is part of the session (the window manager first), the same thing `loginctl` and
+// a person's own shell would point at, and says where it found them.
+//
+// Long-lived programs a tool starts go to the account's own service manager through `systemd-run
+// --user`, never as children of the tool: the runtime's unit is a cgroup the service manager empties
+// whenever the runtime restarts, and a compositor or a clipboard owner started from inside it would
+// die with it.
+//
+// This file is the same in every desktop module that carries it; it moves into the Go SDK once a
+// second consumer outside the desktop wants it.
+package main
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"syscall"
+	"time"
+)
+
+// Where the session is looked for. Variables so a test can point them at a fake tree.
+var (
+	procRoot   = "/proc"
+	runUserDir = "/run/user"
+	x11Sockets = "/tmp/.X11-unix"
+)
+
+// sessionHolders are the processes whose environment is the session's, best first: the window
+// manager is the session, the rest are its children. Anything else carrying DISPLAY ranks after them.
+var sessionHolders = []string{"i3", "sway", "i3bar", "picom", "xss-lock", "dunst", "clipmenud", "xterm"}
+
+// sessionKeys are the variables a session carries that a tool hands on to what it runs.
+var sessionKeys = []string{"DISPLAY", "XAUTHORITY", "WAYLAND_DISPLAY", "DBUS_SESSION_BUS_ADDRESS",
+	"XDG_RUNTIME_DIR", "XDG_SESSION_ID", "I3SOCK"}
+
+// Session is what a tool needs to reach the operator's desktop.
+type Session struct {
+	UID        int    `json:"uid"`
+	Display    string `json:"display,omitempty"`
+	XAuthority string `json:"xauthority,omitempty"`
+	Wayland    string `json:"wayland_display,omitempty"`
+	Bus        string `json:"bus,omitempty"`
+	RuntimeDir string `json:"runtime_dir,omitempty"`
+	SessionID  string `json:"session_id,omitempty"`
+	I3Sock     string `json:"i3sock,omitempty"`
+	// From says where the values were found: the tool's own environment, a process, or the socket.
+	From string `json:"from"`
+}
+
+// ErrNoSession is answered by a tool that needs the desktop when nobody is logged in to it.
+var ErrNoSession = errors.New("no graphical session")
+
+// ErrTimedOut is what run answers for a command ended because it ran past its time.
+var ErrTimedOut = errors.New("timed out")
+
+// ErrNoBus is answered by a tool that needs the session bus when the account has none.
+var ErrNoBus = errors.New("no session bus")
+
+// operatorHome is the account's home: what the runtime was told, else the process's own.
+func operatorHome() string {
+	if h := strings.TrimSpace(os.Getenv("MESH_OPERATOR_HOME")); h != "" {
+		return h
+	}
+	h, _ := os.UserHomeDir()
+	return h
+}
+
+// findSession finds the graphical session of the account this tool runs as, or answers
+// ErrNoSession with what it looked at.
+func findSession() (Session, error) {
+	s := findEnvironment()
+	if s.Display == "" && s.Wayland == "" {
+		return s, fmt.Errorf("%w for uid %d on this machine: no process of the account carries DISPLAY "+
+			"or WAYLAND_DISPLAY, and no X server socket in %s has an authority file to go with it. "+
+			"Is anyone logged in to the desktop?", ErrNoSession, s.UID, x11Sockets)
+	}
+	return s, nil
+}
+
+// findBus finds the account's session bus, which a logged-in account has whether or not a desktop
+// is running.
+func findBus() (Session, error) {
+	s := findEnvironment()
+	if s.Bus == "" {
+		return s, fmt.Errorf("%w for uid %d: DBUS_SESSION_BUS_ADDRESS is not set and %s does not exist "+
+			"(the account is not logged in)", ErrNoBus, s.UID, filepath.Join(runUserDir, strconv.Itoa(s.UID), "bus"))
+	}
+	return s, nil
+}
+
+func findEnvironment() Session {
+	uid := os.Getuid()
+	s := Session{UID: uid}
+	own := map[string]string{}
+	for _, k := range sessionKeys {
+		own[k] = os.Getenv(k)
+	}
+	if own["DISPLAY"] != "" || own["WAYLAND_DISPLAY"] != "" {
+		s.fill(own)
+		s.From = "the tool's own environment"
+	} else if pid, comm, env, ok := sessionProcess(uid); ok {
+		s.fill(env)
+		s.From = fmt.Sprintf("process %s (pid %d)", comm, pid)
+	} else if display, ok := lonelyX11Socket(); ok {
+		if a := filepath.Join(operatorHome(), ".Xauthority"); exists(a) {
+			s.Display, s.XAuthority = display, a
+			s.From = "the X server socket and the account's ~/.Xauthority"
+		}
+		s.fill(own)
+	} else {
+		s.fill(own)
+		s.From = "nothing: no session found"
+	}
+	// The bus and the runtime directory are the account's, whether or not the process named them.
+	runtime := filepath.Join(runUserDir, strconv.Itoa(uid))
+	if s.RuntimeDir == "" && exists(runtime) {
+		s.RuntimeDir = runtime
+	}
+	if s.Bus == "" && s.RuntimeDir != "" && exists(filepath.Join(s.RuntimeDir, "bus")) {
+		s.Bus = "unix:path=" + filepath.Join(s.RuntimeDir, "bus")
+	}
+	return s
+}
+
+func (s *Session) fill(env map[string]string) {
+	set := func(dst *string, key string) {
+		if *dst == "" {
+			*dst = env[key]
+		}
+	}
+	set(&s.Display, "DISPLAY")
+	set(&s.XAuthority, "XAUTHORITY")
+	set(&s.Wayland, "WAYLAND_DISPLAY")
+	set(&s.Bus, "DBUS_SESSION_BUS_ADDRESS")
+	set(&s.RuntimeDir, "XDG_RUNTIME_DIR")
+	set(&s.SessionID, "XDG_SESSION_ID")
+	set(&s.I3Sock, "I3SOCK")
+}
+
+// sessionProcess is the best process of this uid whose environment names a display.
+func sessionProcess(uid int) (int, string, map[string]string, bool) {
+	entries, err := os.ReadDir(procRoot)
+	if err != nil {
+		return 0, "", nil, false
+	}
+	type candidate struct {
+		pid  int
+		comm string
+		env  map[string]string
+		rank int
+	}
+	var found []candidate
+	for _, e := range entries {
+		pid, err := strconv.Atoi(e.Name())
+		if err != nil {
+			continue
+		}
+		dir := filepath.Join(procRoot, e.Name())
+		if owner, ok := ownerOf(dir); !ok || owner != uid {
+			continue
+		}
+		raw, err := os.ReadFile(filepath.Join(dir, "environ"))
+		if err != nil {
+			continue
+		}
+		env := parseEnviron(raw)
+		if env["DISPLAY"] == "" && env["WAYLAND_DISPLAY"] == "" {
+			continue
+		}
+		comm := readTrimmed(filepath.Join(dir, "comm"))
+		rank := len(sessionHolders)
+		for i, h := range sessionHolders {
+			if h == comm {
+				rank = i
+				break
+			}
+		}
+		found = append(found, candidate{pid, comm, env, rank})
+	}
+	if len(found) == 0 {
+		return 0, "", nil, false
+	}
+	sort.Slice(found, func(i, j int) bool {
+		if found[i].rank != found[j].rank {
+			return found[i].rank < found[j].rank
+		}
+		return found[i].pid > found[j].pid // the newer of two equals
+	})
+	best := found[0]
+	return best.pid, best.comm, best.env, true
+}
+
+func parseEnviron(raw []byte) map[string]string {
+	env := map[string]string{}
+	for _, kv := range bytes.Split(raw, []byte{0}) {
+		if i := bytes.IndexByte(kv, '='); i > 0 {
+			env[string(kv[:i])] = string(kv[i+1:])
+		}
+	}
+	return env
+}
+
+func ownerOf(path string) (int, bool) {
+	info, err := os.Stat(path)
+	if err != nil {
+		return 0, false
+	}
+	st, ok := info.Sys().(*syscall.Stat_t)
+	if !ok {
+		return 0, false
+	}
+	return int(st.Uid), true
+}
+
+// lonelyX11Socket is the display of the one X server socket there is, when there is exactly one.
+func lonelyX11Socket() (string, bool) {
+	entries, err := os.ReadDir(x11Sockets)
+	if err != nil {
+		return "", false
+	}
+	var displays []string
+	for _, e := range entries {
+		if n := strings.TrimPrefix(e.Name(), "X"); n != e.Name() {
+			if _, err := strconv.Atoi(n); err == nil {
+				displays = append(displays, ":"+n)
+			}
+		}
+	}
+	if len(displays) != 1 {
+		return "", false
+	}
+	return displays[0], true
+}
+
+func readTrimmed(path string) string {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(string(b))
+}
+
+func exists(path string) bool {
+	_, err := os.Stat(path)
+	return err == nil
+}
+
+// Env is this process's environment with the session's variables in place of its own.
+func (s Session) Env() []string {
+	drop := map[string]bool{}
+	for _, k := range sessionKeys {
+		drop[k] = true
+	}
+	var env []string
+	for _, kv := range os.Environ() {
+		if i := strings.IndexByte(kv, '='); i > 0 && drop[kv[:i]] {
+			continue
+		}
+		env = append(env, kv)
+	}
+	add := func(k, v string) {
+		if v != "" {
+			env = append(env, k+"="+v)
+		}
+	}
+	add("DISPLAY", s.Display)
+	add("XAUTHORITY", s.XAuthority)
+	add("WAYLAND_DISPLAY", s.Wayland)
+	add("DBUS_SESSION_BUS_ADDRESS", s.Bus)
+	add("XDG_RUNTIME_DIR", s.RuntimeDir)
+	add("XDG_SESSION_ID", s.SessionID)
+	add("I3SOCK", s.I3Sock)
+	return env
+}
+
+// mostOutput bounds what a command may answer with, per stream.
+const mostOutput = 256 << 10
+
+// Result is what a command did.
+type Result struct {
+	Stdout    string `json:"stdout"`
+	Stderr    string `json:"stderr,omitempty"`
+	Code      int    `json:"code"`
+	Truncated bool   `json:"truncated,omitempty"`
+}
+
+// run runs a command in the session's environment, its input given, ended with everything it
+// started after timeout. A command that is not installed is an error naming it; one that exits
+// non-zero is a Result with its code, for the caller to judge.
+func (s Session) run(timeout time.Duration, stdin string, name string, args ...string) (Result, error) {
+	path, err := exec.LookPath(name)
+	if err != nil {
+		return Result{}, fmt.Errorf("%s is not installed on this machine", name)
+	}
+	cmd := exec.Command(path, args...)
+	cmd.Env = s.Env()
+	if home := operatorHome(); exists(home) {
+		cmd.Dir = home
+	}
+	if stdin != "" {
+		cmd.Stdin = strings.NewReader(stdin)
+	}
+	var out, errOut capped
+	cmd.Stdout, cmd.Stderr = &out, &errOut
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	if err := cmd.Start(); err != nil {
+		return Result{}, fmt.Errorf("%s: %w", name, err)
+	}
+	done := make(chan error, 1)
+	go func() { done <- cmd.Wait() }()
+	select {
+	case err = <-done:
+	case <-time.After(timeout):
+		_ = syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
+		<-done
+		return Result{Stdout: out.String(), Stderr: errOut.String()},
+			fmt.Errorf("%s did not finish within %s and was ended: %w", name, timeout, ErrTimedOut)
+	}
+	r := Result{Stdout: out.String(), Stderr: errOut.String(), Truncated: out.cut || errOut.cut}
+	var exit *exec.ExitError
+	if errors.As(err, &exit) {
+		r.Code = exit.ExitCode()
+	} else if err != nil {
+		return r, fmt.Errorf("%s: %w", name, err)
+	}
+	return r, nil
+}
+
+// detach starts a long-lived program under the account's own service manager, as a transient unit
+// that carries the session's display, so it outlives the runtime that asked for it. A unit already
+// running under the same name is stopped first, so a fixed name means "at most one".
+func (s Session) detach(unit string, args ...string) error {
+	if s.RuntimeDir == "" {
+		return fmt.Errorf("%w: the account's runtime directory is missing, so its service manager "+
+			"cannot be reached", ErrNoBus)
+	}
+	_, _ = s.run(5*time.Second, "", "systemctl", "--user", "stop", unit+".service")
+	call := []string{"--user", "--collect", "--quiet", "--unit=" + unit}
+	for _, kv := range [][2]string{{"DISPLAY", s.Display}, {"XAUTHORITY", s.XAuthority},
+		{"WAYLAND_DISPLAY", s.Wayland}, {"XDG_SESSION_ID", s.SessionID}, {"I3SOCK", s.I3Sock}} {
+		if kv[1] != "" {
+			call = append(call, "--setenv="+kv[0]+"="+kv[1])
+		}
+	}
+	call = append(call, "--")
+	call = append(call, args...)
+	r, err := s.run(10*time.Second, "", "systemd-run", call...)
+	if err != nil {
+		return err
+	}
+	if r.Code != 0 {
+		return fmt.Errorf("systemd-run %s: %s", unit, strings.TrimSpace(r.Stderr))
+	}
+	return nil
+}
+
+// uniqueUnit is a transient unit name that will not collide with an earlier one.
+func uniqueUnit(prefix string) string {
+	return fmt.Sprintf("%s-%d", prefix, time.Now().UnixNano())
+}
+
+type capped struct {
+	bytes.Buffer
+	cut bool
+}
+
+func (c *capped) Write(p []byte) (int, error) {
+	if room := mostOutput - c.Len(); room < len(p) {
+		if room > 0 {
+			c.Buffer.Write(p[:room])
+		}
+		c.cut = true
+		return len(p), nil
+	}
+	return c.Buffer.Write(p)
+}
+
+// processesOf are the pids of this uid's processes whose command name is comm, oldest first.
+func processesOf(comm string) []int {
+	entries, err := os.ReadDir(procRoot)
+	if err != nil {
+		return nil
+	}
+	uid := os.Getuid()
+	var pids []int
+	for _, e := range entries {
+		pid, err := strconv.Atoi(e.Name())
+		if err != nil {
+			continue
+		}
+		dir := filepath.Join(procRoot, e.Name())
+		if owner, ok := ownerOf(dir); !ok || owner != uid {
+			continue
+		}
+		if readTrimmed(filepath.Join(dir, "comm")) == comm {
+			pids = append(pids, pid)
+		}
+	}
+	sort.Ints(pids)
+	return pids
+}
+
+// signalAll sends sig to every process of this uid named comm, and answers the pids it reached.
+func signalAll(comm string, sig syscall.Signal) []int {
+	var reached []int
+	for _, pid := range processesOf(comm) {
+		if syscall.Kill(pid, sig) == nil {
+			reached = append(reached, pid)
+		}
+	}
+	return reached
+}
diff --git a/modules/clipmenu/cmd/clipmenu-tools/session_test.go b/modules/clipmenu/cmd/clipmenu-tools/session_test.go
new file mode 100644
index 0000000..800cc6d
--- /dev/null
+++ b/modules/clipmenu/cmd/clipmenu-tools/session_test.go
@@ -0,0 +1,174 @@
+package main
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+// fakeMachine points the session finder at a temporary /proc, /run/user and X socket directory, with
+// none of the test process's own session variables, and gives back the root.
+func fakeMachine(t *testing.T) string {
+	t.Helper()
+	root := t.TempDir()
+	procRoot, runUserDir, x11Sockets = filepath.Join(root, "proc"), filepath.Join(root, "run-user"), filepath.Join(root, "x11")
+	for _, d := range []string{procRoot, runUserDir, x11Sockets} {
+		if err := os.MkdirAll(d, 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	for _, k := range sessionKeys {
+		t.Setenv(k, "")
+	}
+	t.Setenv("MESH_OPERATOR_HOME", filepath.Join(root, "home"))
+	t.Cleanup(func() { procRoot, runUserDir, x11Sockets = "/proc", "/run/user", "/tmp/.X11-unix" })
+	return root
+}
+
+func fakeProcess(t *testing.T, pid int, comm string, env ...string) {
+	t.Helper()
+	dir := filepath.Join(procRoot, strconv.Itoa(pid))
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "comm"), []byte(comm+"\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "environ"), []byte(strings.Join(env, "\x00")+"\x00"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestTheSessionIsReadFromTheWindowManagerBeforeAnyOtherProcess(t *testing.T) {
+	fakeMachine(t)
+	fakeProcess(t, 900, "xterm", "DISPLAY=:9", "XAUTHORITY=/elsewhere")
+	fakeProcess(t, 100, "i3", "DISPLAY=:1", "XAUTHORITY=/home/op/.Xauthority",
+		"DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus", "XDG_SESSION_ID=3", "SECRET_TOKEN=never-copied")
+	fakeProcess(t, 50, "bash", "PATH=/usr/bin")
+	s, err := findSession()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if s.Display != ":1" || s.XAuthority != "/home/op/.Xauthority" || s.SessionID != "3" || !strings.Contains(s.From, "i3 (pid 100)") {
+		t.Fatalf("the window manager's environment: %+v", s)
+	}
+	for _, kv := range s.Env() {
+		if strings.HasPrefix(kv, "SECRET_TOKEN=") {
+			t.Fatal("a variable of the session process that is not a session variable was handed on")
+		}
+	}
+}
+
+func TestAnyProcessCarryingADisplayServesWhenTheWindowManagerIsNotFound(t *testing.T) {
+	fakeMachine(t)
+	fakeProcess(t, 10, "firefox", "DISPLAY=:0")
+	fakeProcess(t, 20, "firefox", "DISPLAY=:2")
+	s, err := findSession()
+	if err != nil || s.Display != ":2" {
+		t.Fatalf("the newest of two equals: %+v, %v", s, err)
+	}
+}
+
+func TestNoSessionIsAClearAnswerNotAGuess(t *testing.T) {
+	fakeMachine(t)
+	fakeProcess(t, 10, "sshd", "PATH=/usr/bin")
+	_, err := findSession()
+	if !errors.Is(err, ErrNoSession) || !strings.Contains(err.Error(), "logged in to the desktop") {
+		t.Fatalf("no session: %v", err)
+	}
+}
+
+func TestOneXSocketAndTheAccountsAuthorityFileAreASession(t *testing.T) {
+	root := fakeMachine(t)
+	if err := os.WriteFile(filepath.Join(x11Sockets, "X0"), nil, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(filepath.Join(root, "home"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(root, "home", ".Xauthority"), nil, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	s, err := findSession()
+	if err != nil || s.Display != ":0" || !strings.HasSuffix(s.XAuthority, "/home/.Xauthority") {
+		t.Fatalf("socket and authority: %+v, %v", s, err)
+	}
+}
+
+func TestTheBusIsTheAccountsRuntimeDirectoryWhenNoProcessNamesIt(t *testing.T) {
+	fakeMachine(t)
+	runtime := filepath.Join(runUserDir, strconv.Itoa(os.Getuid()))
+	if _, err := findBus(); !errors.Is(err, ErrNoBus) {
+		t.Fatalf("no runtime directory is no bus: %v", err)
+	}
+	if err := os.MkdirAll(runtime, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(runtime, "bus"), nil, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	s, err := findBus()
+	if err != nil || s.Bus != "unix:path="+filepath.Join(runtime, "bus") || s.RuntimeDir != runtime {
+		t.Fatalf("bus: %+v, %v", s, err)
+	}
+	env := strings.Join(s.Env(), "\n")
+	if !strings.Contains(env, "XDG_RUNTIME_DIR="+runtime) || !strings.Contains(env, "DBUS_SESSION_BUS_ADDRESS=unix:path=") {
+		t.Fatalf("the bus is handed on: %s", env)
+	}
+}
+
+func TestACommandIsBoundedAndANonZeroExitIsAResult(t *testing.T) {
+	fakeMachine(t)
+	s := Session{}
+	r, err := s.run(5*time.Second, "in", "sh", "-c", "cat; echo err >&2; exit 3")
+	if err != nil || r.Stdout != "in" || r.Code != 3 || strings.TrimSpace(r.Stderr) != "err" {
+		t.Fatalf("result: %+v, %v", r, err)
+	}
+	start := time.Now()
+	if _, err := s.run(200*time.Millisecond, "", "sh", "-c", "sleep 30 & sleep 30"); err == nil || time.Since(start) > 5*time.Second {
+		t.Fatalf("a command past its time is ended with what it started: %v after %s", err, time.Since(start))
+	}
+	if _, err := s.run(time.Second, "", "no-such-program-here"); err == nil || !strings.Contains(err.Error(), "not installed") {
+		t.Fatalf("a missing program: %v", err)
+	}
+}
+
+func TestDetachAsksTheAccountsServiceManagerWithTheSessionsDisplay(t *testing.T) {
+	fakeMachine(t)
+	bin := fakeBinaries(t, map[string]string{
+		"systemctl":   `echo "systemctl $*" >> "$LOG"`,
+		"systemd-run": `echo "systemd-run $*" >> "$LOG"`,
+	})
+	log := filepath.Join(bin, "log")
+	t.Setenv("LOG", log)
+	s := Session{Display: ":1", XAuthority: "/x", RuntimeDir: "/run/user/1"}
+	if err := s.detach("picom-session", "picom", "--config", "/c"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := os.ReadFile(log)
+	want := "systemctl --user stop picom-session.service\n" +
+		"systemd-run --user --collect --quiet --unit=picom-session --setenv=DISPLAY=:1 --setenv=XAUTHORITY=/x -- picom --config /c\n"
+	if string(got) != want {
+		t.Fatalf("detach ran:\n%s\nwant:\n%s", got, want)
+	}
+	if err := (Session{}).detach("x", "y"); !errors.Is(err, ErrNoBus) {
+		t.Fatalf("no runtime directory: %v", err)
+	}
+}
+
+// fakeBinaries puts shell scripts named for programs first on PATH, and answers their directory.
+func fakeBinaries(t *testing.T, scripts map[string]string) string {
+	t.Helper()
+	dir := t.TempDir()
+	for name, body := range scripts {
+		if err := os.WriteFile(filepath.Join(dir, name), []byte("#!/bin/sh\n"+body+"\n"), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	t.Setenv("PATH", dir+string(os.PathListSeparator)+os.Getenv("PATH"))
+	return dir
+}
diff --git a/modules/clipmenu/files/i3/50-clipmenu.conf b/modules/clipmenu/files/i3/50-clipmenu.conf
new file mode 100644
index 0000000..41835e6
--- /dev/null
+++ b/modules/clipmenu/files/i3/50-clipmenu.conf
@@ -0,0 +1,5 @@
+# The clipboard's history key (module clipmenu, novox/hq ADR 0208). Owned by the mesh: replaced at
+# every push. clipmenu shows the history through `dmenu`, the node's dmenu-compatible command, which
+# the holder of node-launcher answers (rofi on the workstations); the chosen entry is put back on the
+# clipboard.
+bindsym $mod+period exec --no-startup-id clipmenu -p Clipboard
diff --git a/modules/clipmenu/go.mod b/modules/clipmenu/go.mod
new file mode 100644
index 0000000..f6c083d
--- /dev/null
+++ b/modules/clipmenu/go.mod
@@ -0,0 +1,5 @@
+module clipmenu
+
+go 1.22
+
+require git.novox.be/novox/mesh-sdk/go v0.1.7
diff --git a/modules/clipmenu/go.sum b/modules/clipmenu/go.sum
new file mode 100644
index 0000000..b474419
--- /dev/null
+++ b/modules/clipmenu/go.sum
@@ -0,0 +1,2 @@
+git.novox.be/novox/mesh-sdk/go v0.1.7 h1:C0sTQmtTiyYH7bnqZb7PusXnqA37gKuT7Nqjn9gG47w=
+git.novox.be/novox/mesh-sdk/go v0.1.7/go.mod h1:GFuZUElBZ9A++mxgIKo97aXXo+kV0uJ/UkbhQPPIbrY=
diff --git a/modules/clipmenu/module.json b/modules/clipmenu/module.json
new file mode 100644
index 0000000..1cb1991
--- /dev/null
+++ b/modules/clipmenu/module.json
@@ -0,0 +1,75 @@
+{
+  "module": "clipmenu",
+  "version": "1",
+  "capabilities": [
+    "package-manager"
+  ],
+  "requires": [
+    "x11-display"
+  ],
+  "claims": [
+    {
+      "name": "node-clipboard",
+      "scope": "node",
+      "serves": [
+        "history",
+        "copy"
+      ]
+    }
+  ],
+  "tools": [
+    "clipmenu_paste",
+    "clipmenu_clear",
+    "clipmenu_delete"
+  ],
+  "environment": {
+    "variables": {
+      "CM_SELECTIONS": "clipboard",
+      "CM_MAX_CLIPS": "500",
+      "CM_HISTLENGTH": "15"
+    }
+  },
+  "shell": [
+    {
+      "for": "xinitrc",
+      "slot": "normal",
+      "code": "# The clipboard's history (module clipmenu, novox/hq ADR 0208): clipmenud collects every copy from\n# here on, once per session. It keeps the history in the account's runtime directory, so a reboot\n# forgets it, and with it every password that was ever copied.\nclipmenud &\n"
+    }
+  ],
+  "resources": [
+    {
+      "id": "package",
+      "type": "package",
+      "package": "clipmenu"
+    },
+    {
+      "id": "greenclip",
+      "type": "package",
+      "package": "rofi-greenclip",
+      "absent": true
+    },
+    {
+      "id": "i3-bindings",
+      "type": "file",
+      "path": "${machine:account-home}/.config/i3/config.d/50-clipmenu.conf",
+      "owner": "${machine:account}",
+      "mode": "0644",
+      "content": "# The clipboard's history key (module clipmenu, novox/hq ADR 0208). Owned by the mesh: replaced at\n# every push. clipmenu shows the history through `dmenu`, the node's dmenu-compatible command, which\n# the holder of node-launcher answers (rofi on the workstations); the chosen entry is put back on the\n# clipboard.\nbindsym $mod+period exec --no-startup-id clipmenu -p Clipboard\n"
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "tools",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/clipmenu-tools",
+        "binary": "clipmenu-tools",
+        "loads": [
+          "clipmenu-tools"
+        ]
+      }
+    ]
+  }
+}