A taken tunnel's found configuration is retired once the take is proven (hq ADR 0119)

Kept on disk it was the take's fallback; once the mesh's interface is up in its place and a peer
has handshaken with it, it is an unmaintained way back onto the network, held for ever. It is now
removed from where its unit reads it, its kept original verified first and left as it is, and the
hold ends. Until proven — no handshake, or wg not answering — it is kept and the report says why.
The retirement is recorded apart from holds, so later applies, an undeclare, and a reassignment
find it retired rather than missing, and nothing writes it back.

internal/apply/apply.go

@@ -364,6 +364,7 @@ func ApplyKeeping(
 		// flushed. A failure here fails the service too — the mesh's interface is not started on a
 		// port the found one still holds.
 		stoppedFound := false
+		tookAt := -1
 		if svc, ok := resource.(*declaration.Service); ok && svc.TakesOver != nil {
 			var outcome Outcome
 			var facts TakenTunnel
@@ -388,8 +389,11 @@ func ApplyKeeping(
 				log(fmt.Sprintf("  failed %s (%s): %v", svc.Identity(), svc.Unit, err))
 				continue
 			}
+			tookAt = len(report.Outcomes)
 			report.Outcomes = append(report.Outcomes, outcome)
-			log(fmt.Sprintf("  held %s (%s): %s", outcome.ID, outcome.Target, outcome.Detail))
+			if outcome.Action == "held" {
+				log(fmt.Sprintf("  held %s (%s): %s", outcome.ID, outcome.Target, outcome.Detail))
+			}
 		}
 
 		was, _ := known.Find(resource.Identity())
@@ -510,6 +514,16 @@ func ApplyKeeping(
 			// The found interface is down and the mesh's is up in its place: the tunnel changed
 			// hands (novox/hq ADR 0105). Read from the machine, not assumed.
 			report.Tunnel.State = tunnelState(ctx, sys, svc.TakesOver.Unit, svc.Unit, run)
+			// And once a peer has handshaken with it, the take is proven and the found
+			// configuration is retired — here, after the mesh's service applied, so in the apply
+			// of the take itself only if a peer is already through; otherwise a later apply
+			// retires it (novox/hq ADR 0119). What it did replaces what the take said of the file.
+			if o, did := retireFound(ctx, svc, &known, run, keep, report.Tunnel, time.Now().UTC()); did {
+				if tookAt >= 0 {
+					report.Outcomes[tookAt] = o
+				}
+				log(fmt.Sprintf("  %s %s (%s): %s", o.Action, o.ID, o.Target, o.Detail))
+			}
 		}
 		report.Outcomes = append(report.Outcomes, outcome)
 		if outcome.Action != "unchanged" {

internal/apply/hold_test.go

@@ -21,6 +21,10 @@ type machine struct {
 	asked      []string
 	// wgUp is what `wg show interfaces` answers: the tunnels up on the machine.
 	wgUp string
+	// handshakes is what `wg show <interface> latest-handshakes` answers, and handshakesFail the
+	// error it fails with instead — a machine with no `wg`, say (novox/hq ADR 0119).
+	handshakes     string
+	handshakesFail error
 
 	// units are service units by name, as systemd would report them; volumes are the runtime's
 	// named volumes.
@@ -101,6 +105,9 @@ func (m *machine) run(_ context.Context, name string, args ...string) (string, e
 		return m.systemctl(args)
 	}
 	if name == "wg" {
+		if len(args) > 0 && args[len(args)-1] == "latest-handshakes" {
+			return m.handshakes, m.handshakesFail
+		}
 		return m.wgUp, nil
 	}
 	if name == "getent" {

internal/apply/plan.go

@@ -56,6 +56,12 @@ func Plan(d *declaration.Declaration, known store.State, origin string) []Step {
 	for _, r := range d.Resources {
 		declared[r.Identity()] = true
 	}
+	// The found tunnel's configuration is held under an id of its own, declared for as long as the
+	// service taking it over is — as ApplyKeeping counts it, or a plan would forget a hold the
+	// apply keeps (novox/hq ADR 0105).
+	if svc := takesOver(d); svc != nil {
+		declared[takeOverID(svc)] = true
+	}
 	rec := known.Firewall
 	ufw := rec != nil && rec.Kind == string(firewall.UFW)
 
@@ -136,7 +142,12 @@ func Plan(d *declaration.Declaration, known store.State, origin string) []Step {
 	}
 	steps = append(steps, orphans...)
 	for _, r := range rest {
-		steps = append(steps, planned(r, d, known))
+		step := planned(r, d, known)
+		if svc, ok := r.(*declaration.Service); ok && svc.TakesOver != nil && d.Adoption != nil && step.Verb != "hold" {
+			// The take comes before the service that replaces the tunnel, as it does in the apply.
+			steps = append(steps, plannedTake(svc, known))
+		}
+		steps = append(steps, step)
 	}
 
 	// Only a declaration from the mesh converges a node; a bundle or a file never retires the
@@ -239,6 +250,31 @@ func planned(r declaration.Resource, d *declaration.Declaration, known store.Sta
 	return step
 }
 
+// plannedTake is what the take of a found tunnel would do to its configuration (novox/hq ADR 0105,
+// ADR 0119): kept as found while the take is not proven, and retired — removed from where its unit
+// reads it, its original staying kept — by the first apply that finds the mesh's interface up in
+// its place with a peer handshaken. Whether that is this apply is read from the machine, which a
+// plan does not do, so it says when rather than whether. One the mesh retired already is said as
+// retired: nothing brings it back.
+func plannedTake(svc *declaration.Service, known store.State) Step {
+	t := svc.TakesOver
+	step := Step{Verb: "hold", Type: string(declaration.TypeFile), ID: takeOverID(svc), Target: t.Config}
+	if r, ok := known.RetiredAt(t.Config); ok {
+		step.Verb = "check"
+		step.Why = "retired once the take of " + t.Interface + " was proven; its original stays at " + r.Kept +
+			" and the mesh never brings it back"
+		return step
+	}
+	step.Why = "the configuration of the tunnel " + t.Interface + ", kept as found while " + svc.Unit +
+		" takes it over (" + t.Unit + " stopped and disabled, never flushed); retired — removed from " +
+		t.Config + ", its original staying kept — once the take is proven by a peer handshaking on " +
+		strings.TrimPrefix(svc.Unit, "wg-quick@")
+	if h, ok := known.HeldAt(takeOverID(svc)); ok && h.Kept != "" {
+		step.Why += "; the original is at " + h.Kept
+	}
+	return step
+}
+
 // readsChanged is which of the files a container was created reading the apply will hand it
 // changed — the same comparison applyContainer makes (novox/hq 04-ISSUES/103), settled from the
 // declaration and the record alone.

internal/apply/takeover.go

@@ -27,6 +27,16 @@ import (
 // Every apply, not once: a found unit somebody starts again would take the port back from the
 // mesh's interface, so it is stopped again and said so. That is the one place an adopted node
 // undoes something done by hand, and it is because the tunnel is the mesh's now.
+//
+// **Until the take is proven, and then the found configuration is retired** (novox/hq ADR 0119).
+// Keeping it on disk was the caution the take needed: if the mesh's interface does not come up,
+// the found unit is started again and the peers never notice. That caution is spent once the
+// tunnel is taken — the found unit down and disabled, the mesh's interface up — and a peer has
+// handshaken with the mesh's interface. From then on a configuration nothing maintains, one
+// command away from raising a second way onto the network, is not a rollback path but a door
+// nobody watches. So it is removed from where its unit reads it; its original, kept before
+// anything happened to it (ADR 0100), stays kept; and the hold on it ends. A take never proven
+// keeps it, and says so — a broken take is visible, not silently retired.
 
 // TakenTunnel is what an apply says about a tunnel it took over, for the node's report.
 type TakenTunnel struct {
@@ -36,7 +46,9 @@ type TakenTunnel struct {
 	Peers     int
 	// State is "not-taken" (the found interface still up, the mesh's not), "taken" (the found one
 	// down and disabled, the mesh's up with its key) or "down" (the found one down and the mesh's
-	// not up: the peers reach nothing). Note is what this apply did about it.
+	// not up: the peers reach nothing). Note is what this apply did about it — and, for a taken
+	// tunnel, whether the take is proven and its found configuration retired (novox/hq ADR 0119).
+	// Kept is where the found configuration's original is, retired or not.
 	State string
 	Note  string
 	Kept  string
@@ -84,14 +96,35 @@ func takeOver(ctx context.Context, sys system.System, svc *declaration.Service,
 
 	// 1. The configuration, kept like any held file. A synthetic file resource stands for it, so
 	//    the same code keeps its original, digests it and notices it changing.
+	//
+	//    **Unless it was retired** (novox/hq ADR 0119): the take was proven and the mesh removed
+	//    it, so there is nothing to hold and nothing missing — only where its original is, which
+	//    the retirement recorded. A hold still standing is let go: that is what retiring it meant.
+	//    One put back at its path by a person is on the machine again, with no hold, and is found
+	//    and kept afresh — the same content kept once, as any original is — and retired again by
+	//    the first apply that finds the take still proven.
 	file := &declaration.File{ID: id, Type: declaration.TypeFile, Path: t.Config}
-	was, already := known.HeldAt(id)
-	out, held, err := hold(ctx, sys, file, module, was, already,
-		"the configuration of the tunnel "+t.Interface+", taken over by "+svc.Unit, run, keep, now)
-	if err != nil {
-		return begin(file), facts, false, fmt.Errorf("keeping the found tunnel's configuration: %w", err)
+	var held store.Held
+	retired, wasRetired := known.RetiredAt(t.Config)
+	if wasRetired && !present(t.Config) {
+		known.Release(id)
+		held = store.Held{Kept: retired.Kept}
+		out = begin(file)
+		out.Action = "unchanged"
+		facts.Note = "the found configuration " + t.Config + " was retired once the take was proven; " +
+			"its original is kept at " + retired.Kept + " and the mesh never brings it back"
+	} else {
+		if wasRetired {
+			known.Unretire(t.Config)
+		}
+		was, already := known.HeldAt(id)
+		out, held, err = hold(ctx, sys, file, module, was, already,
+			"the configuration of the tunnel "+t.Interface+", taken over by "+svc.Unit, run, keep, now)
+		if err != nil {
+			return begin(file), facts, false, fmt.Errorf("keeping the found tunnel's configuration: %w", err)
+		}
+		known.RecordHeld(held)
 	}
-	known.RecordHeld(held)
 	facts.Kept = held.Kept
 	// What the file says, for the report: from the machine, or from the kept original when the
 	// machine's copy is gone. The private key stays in the file; nothing here keeps it.
@@ -185,6 +218,9 @@ func takeOver(ctx context.Context, sys system.System, svc *declaration.Service,
 	}
 
 	out.Detail = "the tunnel " + t.Interface + "'s configuration, kept as found"
+	if wasRetired && out.Action == "unchanged" {
+		out.Detail = "the tunnel " + t.Interface + "'s configuration, retired once the take was proven"
+	}
 	if held.Kept != "" {
 		out.Detail += " (original at " + held.Kept + ")"
 	}
@@ -335,6 +371,124 @@ func restoreFound(ctx context.Context, sys system.System, unit string, run Runne
 	facts.Note += "; " + unit + " was started again, so the machine has the tunnel it had"
 }
 
+// retireFound removes the found tunnel's configuration from where its unit reads it, once the take
+// is proven, and ends the hold on it (novox/hq ADR 0119). Asked after the mesh's service applied
+// and the tunnel reads as taken; retired says whether this apply retired it, and out is then what
+// replaces the take's outcome for the configuration.
+//
+// **Proven is taken and a handshake.** Taken alone — the found unit down and disabled, the mesh's
+// interface up — says the mesh's interface exists, not that any peer reaches it: an interface up
+// with the wrong key is taken and carries nothing. A peer that has completed a handshake with it
+// has checked its key, so that is the proof, asked of the kernel through `wg`. Anything short of
+// one — no peer yet, every time zero, `wg` missing or failing — keeps the file, and the account
+// says which: a take that never proves itself is visible rather than silently retired.
+//
+// **The original must still be kept.** It is the record of what the predecessor was and a
+// person's only way back (ADR 0100); a kept copy that has gone missing is said, and the file is
+// not removed, since removing it then would lose the only copy. What is on disk now, if something
+// other than the mesh rewrote it since it was found, is kept too before it goes — by content, so
+// the first original is never overwritten.
+//
+// The found unit is left disabled; without its configuration it cannot raise the interface, so
+// every later apply's check of it finds nothing to do. Nothing here ever writes the file back.
+func retireFound(ctx context.Context, svc *declaration.Service, known *store.State, run Runner, keep Keep,
+	facts *TakenTunnel, now time.Time) (out Outcome, retired bool) {
+	t := svc.TakesOver
+	id := takeOverID(svc)
+	if facts.State != Taken {
+		return out, false
+	}
+	held, isHeld := known.HeldAt(id)
+	if !isHeld {
+		// Retired already (takeOver let any hold go and said so), or never held: nothing to do.
+		return out, false
+	}
+	say := func(note string) {
+		if facts.Note != "" {
+			facts.Note += "; "
+		}
+		facts.Note += note
+	}
+	mesh := strings.TrimPrefix(svc.Unit, "wg-quick@")
+	peers, err := tunnel.Handshaken(ctx, tunnel.Runner(run), mesh)
+	if err != nil {
+		say("taken, not yet proven: " + err.Error() + "; the found configuration " + t.Config + " is kept")
+		return out, false
+	}
+	if peers == 0 {
+		say("taken, not yet proven: no peer has handshaken on " + mesh + "; the found configuration " +
+			t.Config + " is kept")
+		return out, false
+	}
+	proven := fmt.Sprintf("proven: %d peer(s) handshaken on %s", peers, mesh)
+
+	// The kept original, read back — not just named in a record.
+	if held.Kept == "" {
+		say(proven + ", and the found configuration " + t.Config + " is not retired: no original of it " +
+			"was kept, so removing it would leave no record of what the predecessor was")
+		return out, false
+	}
+	original, err := os.ReadFile(held.Kept)
+	if err != nil || (held.Digest != "" && digestOf(string(original)) != held.Digest) {
+		why := "is missing"
+		if err == nil {
+			why = "no longer holds what was found"
+		} else if !errors.Is(err, os.ErrNotExist) {
+			why = "cannot be read (" + err.Error() + ")"
+		}
+		say(proven + ", and the found configuration " + t.Config + " is not retired: its kept original " +
+			held.Kept + " " + why + ", so removing it would lose the only copy")
+		return out, false
+	}
+
+	gone := !present(t.Config)
+	if !gone {
+		current, err := os.ReadFile(t.Config)
+		if err != nil {
+			say(proven + ", and the found configuration " + t.Config + " is not retired: it cannot be read (" +
+				err.Error() + ")")
+			return out, false
+		}
+		if held.Digest != "" && digestOf(string(current)) != held.Digest {
+			if keep == nil {
+				say(proven + ", and the found configuration " + t.Config + " is not retired: it was rewritten " +
+					"since it was found and this host has nowhere to keep what it holds now")
+				return out, false
+			}
+			if _, err := keep(t.Config, current, 0o600); err != nil {
+				say(proven + ", and the found configuration " + t.Config + " is not retired: keeping what it " +
+					"holds now failed (" + err.Error() + ")")
+				return out, false
+			}
+		}
+		if err := os.Remove(t.Config); err != nil && !errors.Is(err, os.ErrNotExist) {
+			say(proven + ", and the found configuration " + t.Config + " could not be removed (" + err.Error() + ")")
+			return out, false
+		}
+		if present(t.Config) {
+			say(proven + ", and the found configuration " + t.Config + " is still there after it was removed")
+			return out, false
+		}
+	}
+
+	known.RecordRetired(store.Retired{ID: id, Path: t.Config, Kept: held.Kept, At: now})
+	known.Release(id)
+	facts.Kept = held.Kept
+	say(proven + "; the found configuration " + t.Config + " is retired — its original kept at " +
+		held.Kept + ", " + t.Unit + " left disabled, and the mesh never brings it back")
+
+	out = Outcome{ID: id, Type: string(declaration.TypeFile), Target: t.Config, Action: "removed",
+		Detail: "retired: the take of " + t.Interface + " is " + proven + "; original kept at " + held.Kept}
+	if gone {
+		// Already gone — removed by something other than the mesh, or by an apply whose record was
+		// never saved. Nothing removed here; the hold ends all the same.
+		out.Action = "unchanged"
+		out.Detail = "retired: the take of " + t.Interface + " is " + proven + " and " + t.Config +
+			" was already gone; original kept at " + held.Kept
+	}
+	return out, true
+}
+
 // takesOver is the service in a declaration that takes over a tunnel, if any: one per node, since
 // a machine has one private network.
 func takesOver(d *declaration.Declaration) *declaration.Service {

internal/apply/takeover_test.go

@@ -4,6 +4,7 @@ import (
 	"crypto/ecdh"
 	"crypto/rand"
 	"encoding/base64"
+	"errors"
 	"os"
 	"path/filepath"
 	"strings"
@@ -77,7 +78,10 @@ func TestTheFoundTunnelIsStoppedNeverFlushedAndItsConfigurationKept(t *testing.T
 		t.Fatalf("the found unit was not stopped and disabled: %+v", u)
 	}
 	for _, asked := range m.asked {
-		if strings.HasPrefix(asked, "wg ") && !strings.HasPrefix(asked, "wg show interfaces") {
+		// Only ever asked about: which interfaces are up, and whether a peer has handshaken with
+		// the mesh's own (novox/hq ADR 0119).
+		if strings.HasPrefix(asked, "wg ") && !strings.HasPrefix(asked, "wg show interfaces") &&
+			asked != "wg show mesh0 latest-handshakes" {
 			t.Errorf("the found interface was touched with %q; it is stopped, never flushed", asked)
 		}
 		if strings.HasPrefix(asked, "wg-quick") || strings.Contains(asked, "peer remove") {
@@ -254,3 +258,254 @@ func TestATakeoverIsRefusedOnAConvergedDeclaration(t *testing.T) {
 		t.Fatalf("a takeover on a converged node was accepted: %v", err)
 	}
 }
+
+// novox/hq ADR 0119: once the take is proven — taken, and a peer handshaken on the mesh's
+// interface — the found configuration is removed from where its unit reads it, its original stays
+// kept and the hold on it ends. Never before, and never brought back.
+
+const takesOverID = "mesh-wireguard.overlay-up.takes-over"
+
+// handshaken is `wg show mesh0 latest-handshakes` with one of the two peers through.
+const handshaken = "PEER-A=\t1790000000\nPEER-B=\t0\n"
+
+func TestAProvenTakeRetiresTheFoundConfiguration(t *testing.T) {
+	dir, config, mesh, keyFile, m := aHubInUse(t)
+	m.handshakes = handshaken
+	report, state := applyAdopted(t, aTakeover(t, config, mesh, keyFile, "51900", "192.0.2.1"), store.State{}, m, dir)
+
+	if _, err := os.Lstat(config); !os.IsNotExist(err) {
+		t.Fatalf("a proven take left the found configuration where its unit reads it: %v", err)
+	}
+	retired, ok := state.RetiredAt(config)
+	if !ok || retired.Kept == "" || retired.ID != takesOverID {
+		t.Fatalf("the retirement was not recorded: %+v", state.Retired)
+	}
+	if kept, _ := os.ReadFile(retired.Kept); string(kept) != foundConf {
+		t.Fatalf("the kept original did not survive the retirement: %q", kept)
+	}
+	if _, held := state.HeldAt(takesOverID); held {
+		t.Error("the hold on the found configuration did not end with its retirement")
+	}
+	if u := m.units["wg-quick@wg0"]; u.active != "inactive" || u.enabled != "disabled" {
+		t.Errorf("the found unit is not left down and disabled: %+v", u)
+	}
+	if report.Tunnel == nil || report.Tunnel.State != Taken || report.Tunnel.Kept != retired.Kept ||
+		!strings.Contains(report.Tunnel.Note, "proven: 1 peer(s) handshaken on mesh0") ||
+		!strings.Contains(report.Tunnel.Note, "is retired") {
+		t.Fatalf("the account does not say the take is proven and the configuration retired: %+v", report.Tunnel)
+	}
+	if o := outcomeOf(report, takesOverID); o.Action != "removed" || !strings.Contains(o.Detail, "retired") {
+		t.Errorf("the retirement is not what the apply says it did to the file: %+v", o)
+	}
+	// And the account still carries what was found, read from the kept original.
+	if report.Tunnel.Port != 51900 || report.Tunnel.Peers != 2 {
+		t.Errorf("the account lost what the tunnel was: %+v", report.Tunnel)
+	}
+}
+
+func TestATakeNotProvenKeepsTheFoundConfigurationAndSaysSo(t *testing.T) {
+	cases := map[string]struct {
+		handshakes string
+		fail       error
+		says       string
+	}{
+		"no peer at all":          {"", nil, "no peer has handshaken on mesh0"},
+		"every handshake at zero": {"PEER-A=\t0\nPEER-B=\t0\n", nil, "no peer has handshaken on mesh0"},
+		"wg is not there":         {"", errors.New(`exec: "wg": executable file not found in $PATH`), "executable file not found"},
+		"the answer is nonsense":  {"unable to access interface\n", nil, "not a peer and a time"},
+	}
+	for name, c := range cases {
+		dir, config, mesh, keyFile, m := aHubInUse(t)
+		m.handshakes, m.handshakesFail = c.handshakes, c.fail
+		d := aTakeover(t, config, mesh, keyFile, "51900", "192.0.2.1")
+		report, state := applyAdopted(t, d, store.State{}, m, dir)
+
+		if got, _ := os.ReadFile(config); string(got) != foundConf {
+			t.Fatalf("%s: a take not proven lost the found configuration", name)
+		}
+		if _, held := state.HeldAt(takesOverID); !held {
+			t.Errorf("%s: the hold ended although the take is not proven", name)
+		}
+		if _, retired := state.RetiredAt(config); retired {
+			t.Errorf("%s: recorded as retired", name)
+		}
+		if report.Tunnel == nil || report.Tunnel.State != Taken ||
+			!strings.Contains(report.Tunnel.Note, "taken, not yet proven") ||
+			!strings.Contains(report.Tunnel.Note, c.says) || !strings.Contains(report.Tunnel.Note, "is kept") {
+			t.Errorf("%s: the account does not say the take is not proven and why: %+v", name, report.Tunnel)
+		}
+
+		// A later apply that finds a peer through retires it: the take itself need not be the one.
+		m.handshakes, m.handshakesFail = handshaken, nil
+		_, state = applyAdopted(t, d, state, m, dir)
+		if _, err := os.Lstat(config); !os.IsNotExist(err) {
+			t.Errorf("%s: the apply after the take was proven kept the found configuration", name)
+		}
+		if _, retired := state.RetiredAt(config); !retired {
+			t.Errorf("%s: the later retirement was not recorded", name)
+		}
+	}
+}
+
+func TestAFoundConfigurationWhoseKeptOriginalIsMissingIsNotRetired(t *testing.T) {
+	dir, config, mesh, keyFile, m := aHubInUse(t)
+	d := aTakeover(t, config, mesh, keyFile, "51900", "192.0.2.1")
+	_, state := applyAdopted(t, d, store.State{}, m, dir)
+	held, _ := state.HeldAt(takesOverID)
+	if err := os.Remove(held.Kept); err != nil {
+		t.Fatal(err)
+	}
+
+	m.handshakes = handshaken
+	report, state := applyAdopted(t, d, state, m, dir)
+	if got, _ := os.ReadFile(config); string(got) != foundConf {
+		t.Fatal("the found configuration was removed with no kept original left of it")
+	}
+	if _, still := state.HeldAt(takesOverID); !still {
+		t.Error("the hold ended although nothing was retired")
+	}
+	if _, retired := state.RetiredAt(config); retired {
+		t.Error("recorded as retired")
+	}
+	if report.Tunnel == nil || !strings.Contains(report.Tunnel.Note, "is not retired") ||
+		!strings.Contains(report.Tunnel.Note, held.Kept+" is missing") {
+		t.Errorf("the account does not say the kept original is missing: %+v", report.Tunnel)
+	}
+}
+
+func TestAFoundConfigurationRewrittenSinceItWasFoundIsKeptAgainBeforeItGoes(t *testing.T) {
+	dir, config, mesh, keyFile, m := aHubInUse(t)
+	d := aTakeover(t, config, mesh, keyFile, "51900", "192.0.2.1")
+	_, state := applyAdopted(t, d, store.State{}, m, dir)
+	rewritten := foundConf + "\n[Peer]\nPublicKey = PEER-C=\nAllowedIPs = 192.0.2.4/32\n"
+	if err := os.WriteFile(config, []byte(rewritten), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	m.handshakes = handshaken
+	_, state = applyAdopted(t, d, state, m, dir)
+	if _, err := os.Lstat(config); !os.IsNotExist(err) {
+		t.Fatal("a proven take kept a rewritten configuration")
+	}
+	retired, _ := state.RetiredAt(config)
+	if first, _ := os.ReadFile(retired.Kept); string(first) != foundConf {
+		t.Errorf("the first original was overwritten: %q", first)
+	}
+	kept, _ := filepath.Glob(filepath.Join(dir, "kept", "*-wg0.conf"))
+	var found bool
+	for _, k := range kept {
+		if got, _ := os.ReadFile(k); string(got) == rewritten {
+			found = true
+		}
+	}
+	if !found {
+		t.Errorf("what the file held when it was retired was not kept: %v", kept)
+	}
+}
+
+func TestARetiredTakeIsSteadyAndItsFoundUnitFindsNothingToDo(t *testing.T) {
+	dir, config, mesh, keyFile, m := aHubInUse(t)
+	m.handshakes = handshaken
+	d := aTakeover(t, config, mesh, keyFile, "51900", "192.0.2.1")
+	_, state := applyAdopted(t, d, store.State{}, m, dir)
+	retired, _ := state.RetiredAt(config)
+
+	// wg-quick@wg0 with no configuration: inactive, and disabled — the check of it every apply
+	// makes must find nothing to do and fail on nothing.
+	m.asked = nil
+	report, again := applyAdopted(t, d, state, m, dir)
+	if report.Changed() {
+		t.Errorf("an apply after the retirement moved the machine: %+v", report.Outcomes)
+	}
+	if m.did("systemctl stop wg-quick@wg0") || m.did("systemctl start wg-quick@wg0") {
+		t.Errorf("the retired tunnel's unit was acted on: %v", m.asked)
+	}
+	if _, err := os.Lstat(config); !os.IsNotExist(err) {
+		t.Error("the found configuration came back")
+	}
+	if _, held := again.HeldAt(takesOverID); held {
+		t.Error("a retired configuration is held again")
+	}
+	if r, ok := again.RetiredAt(config); !ok || r != retired {
+		t.Errorf("the retirement was not kept as it was: %+v", again.Retired)
+	}
+	if o := outcomeOf(report, takesOverID); o.Action != "unchanged" || !strings.Contains(o.Detail, "retired") {
+		t.Errorf("the retired configuration is not said as retired: %+v", o)
+	}
+	if report.Tunnel == nil || report.Tunnel.State != Taken || report.Tunnel.Kept != retired.Kept ||
+		!strings.Contains(report.Tunnel.Note, "retired") || report.Tunnel.Port != 51900 {
+		t.Errorf("the account of a retired take does not say so: %+v", report.Tunnel)
+	}
+
+	// Enabled at boot again by a person: disabled again, as any take does, and still no error.
+	m.units["wg-quick@wg0"].enabled = "enabled"
+	_, _ = applyAdopted(t, d, again, m, dir)
+	if m.units["wg-quick@wg0"].enabled != "disabled" {
+		t.Error("the found unit enabled again by hand was left to start at boot")
+	}
+}
+
+func TestUndeclaringThePrivateNetworkAfterRetirementBringsNothingBack(t *testing.T) {
+	dir, config, mesh, keyFile, m := aHubInUse(t)
+	m.handshakes = handshaken
+	d := aTakeover(t, config, mesh, keyFile, "51900", "192.0.2.1")
+	_, state := applyAdopted(t, d, store.State{}, m, dir)
+
+	// The private network unassigned: only something else is declared.
+	other := adopted(t, `{"taken":[],"untaken":{}}`,
+		`{"id":"other.file","type":"file","path":"`+filepath.Join(dir, "other.conf")+`","content":"x\n"}`)
+	m.asked = nil
+	_, after := applyAdopted(t, other, state, m, dir)
+	if _, err := os.Lstat(config); !os.IsNotExist(err) {
+		t.Fatal("undeclaring the private network brought the found configuration back")
+	}
+	if m.did("systemctl start wg-quick@wg0") || m.did("systemctl enable wg-quick@wg0") {
+		t.Errorf("undeclaring the private network started the found tunnel: %v", m.asked)
+	}
+	if _, ok := after.RetiredAt(config); !ok {
+		t.Error("the retirement was forgotten with the private network")
+	}
+
+	// Assigned again, it finds the configuration retired rather than missing, and raises the
+	// mesh's interface.
+	report, _ := applyAdopted(t, d, after, m, dir)
+	if report.Tunnel == nil || report.Tunnel.State != Taken {
+		t.Errorf("the private network assigned again did not take the tunnel: %+v", report.Tunnel)
+	}
+	if _, err := os.Lstat(config); !os.IsNotExist(err) {
+		t.Error("assigning the private network again brought the found configuration back")
+	}
+}
+
+func TestAPlanSaysTheFoundConfigurationIsRetiredWhenTheTakeIsProven(t *testing.T) {
+	dir, config, mesh, keyFile, m := aHubInUse(t)
+	d := aTakeover(t, config, mesh, keyFile, "51900", "192.0.2.1")
+
+	plan := Plan(d, store.State{}, store.OriginDeclared)
+	report, state := applyAdopted(t, d, store.State{}, m, dir)
+	if got, want := strings.Join(ids(plan), " "), strings.Join(outcomeIDs(report), " "); got != want {
+		t.Errorf("the plan said %q and the apply did %q", got, want)
+	}
+	var take Step
+	for _, s := range plan {
+		if s.ID == takesOverID {
+			take = s
+		}
+	}
+	if take.Verb != "hold" || take.Target != config || !strings.Contains(take.Why, "retired — removed from "+config) ||
+		!strings.Contains(take.Why, "handshaking on mesh0") {
+		t.Errorf("the plan does not say the found configuration is retired once proven: %+v", take)
+	}
+	// Held and still declared: never planned as forgotten.
+	if strings.Contains(verbs(Plan(d, state, store.OriginDeclared)), "forget "+takesOverID) {
+		t.Error("the plan forgets a hold the apply keeps")
+	}
+
+	m.handshakes = handshaken
+	_, state = applyAdopted(t, d, state, m, dir)
+	for _, s := range Plan(d, state, store.OriginDeclared) {
+		if s.ID == takesOverID && (s.Verb != "check" || !strings.Contains(s.Why, "retired once the take")) {
+			t.Errorf("a retired configuration is planned as %+v", s)
+		}
+	}
+}