diff --git a/modules/claude-licence-manager/cmd/claude-licence-manager/manager.go b/modules/claude-licence-manager/cmd/claude-licence-manager/manager.go
index 12e7d2f2a..81828085f 100644
--- a/modules/claude-licence-manager/cmd/claude-licence-manager/manager.go
+++ b/modules/claude-licence-manager/cmd/claude-licence-manager/manager.go
@@ -686,11 +686,26 @@ func (m *Manager) ReadUsageOf(ctx context.Context, licence string, dry bool) ([]
 		if l.Kind != "subscription" || l.Generation == 0 || (licence != "" && l.Name != licence) {
 			continue
 		}
-		g, err := m.grantOf(ctx, l)
+		// The reading takes the licence's grant under its lease, so it never reads a grant a refresh is replacing (§4,
+		// §16); a grant the vault does not answer is a failed reading like a vendor's refusal (§31).
+		key := "licence." + KeyFor(l.Name)
+		leased, err := m.Store.Lease(ctx, key, m.Holder, leaseFor)
 		if err != nil {
 			return out, err
 		}
-		raw, err := m.Vendor.Usage(ctx, g.AccessToken)
+		if !leased {
+			out = append(out, Read{Licence: l.Name, Error: "another run holds its lease", Switches: []Switch{}})
+			continue
+		}
+		unlease := func() { _ = m.Store.Unlease(ctx, key, m.Holder) }
+		if fresh, err := m.Store.Licence(ctx, l.Name); err == nil && fresh != nil {
+			l = *fresh
+		}
+		var raw map[string]any
+		g, err := m.grantOf(ctx, l)
+		if err == nil {
+			raw, err = m.Vendor.Usage(ctx, g.AccessToken)
+		}
 		g = FullGrant{}
 		if err == nil && raw == nil {
 			err = errors.New("the usage endpoint answered nothing")
@@ -703,7 +718,9 @@ func (m *Manager) ReadUsageOf(ctx context.Context, licence string, dry bool) ([]
 			}
 			kept.ReadError = err.Error()
 			l.Usage = &kept
-			if err := m.Store.SaveLicence(ctx, l); err != nil {
+			err := m.Store.SaveLicence(ctx, l)
+			unlease()
+			if err != nil {
 				return out, err
 			}
 			m.Log("reading the usage of %s failed: %v", l.Name, err)
@@ -712,13 +729,16 @@ func (m *Manager) ReadUsageOf(ctx context.Context, licence string, dry bool) ([]
 		}
 		reading := FlattenUsage(raw)
 		if err := m.Store.RecordUsage(ctx, l.Name, m.Now().UnixMilli(), reading, raw); err != nil {
+			unlease()
 			return out, err
 		}
 		// The latest reading beside its licence, so licences answers from one key (§2).
 		latest := reading
 		latest.ReadAt = m.Now().UTC().Format(time.RFC3339Nano)
 		l.Usage = &latest
-		if err := m.Store.SaveLicence(ctx, l); err != nil {
+		err = m.Store.SaveLicence(ctx, l)
+		unlease()
+		if err != nil {
 			return out, err
 		}
 		_ = m.Emit("usage.read", map[string]any{"licence": l.Name, "sessionPct": reading.SessionPct,
diff --git a/modules/claude-licence-manager/cmd/claude-licence-manager/room_test.go b/modules/claude-licence-manager/cmd/claude-licence-manager/room_test.go
index 9f8f5b5b8..aeafc0005 100644
--- a/modules/claude-licence-manager/cmd/claude-licence-manager/room_test.go
+++ b/modules/claude-licence-manager/cmd/claude-licence-manager/room_test.go
@@ -64,6 +64,29 @@ func TestAFailedReadingKeepsThePercentages(t *testing.T) {
 	if n := len(mm.usage.entries); n != 1 {
 		t.Fatalf("a failed reading appended: %d entries", n)
 	}
+	// §16, §31: a grant the vault does not answer is a failed reading, written and gone past, never the end of the round.
+	mm.vendor.usageErr = nil
+	mm.grants.mu.Lock()
+	delete(mm.grants.held, SecretName(KeyFor(licence1), PartGrant))
+	mm.grants.mu.Unlock()
+	if err := mm.m.ReadUsage(ctx); err != nil {
+		t.Fatalf("a grant the vault did not answer ended the round: %v", err)
+	}
+	l, _ = mm.store.Licence(ctx, licence1)
+	if !strings.Contains(l.Usage.ReadError, "cannot be read from the vault") || *l.Usage.WeeklyPct != 97 {
+		t.Fatalf("after the vault's refusal the reading is %+v", l.Usage)
+	}
+	// §4, §16: a reading is taken under the licence's lease; with another run holding it, nothing is read or written.
+	if ok, _ := mm.store.Lease(ctx, "licence."+KeyFor(licence1), "another run", time.Minute); !ok {
+		t.Fatal("the lease was not taken")
+	}
+	reads, err := mm.m.ReadUsageOf(ctx, licence1, true)
+	if err != nil || len(reads) != 1 || reads[0].Error != "another run holds its lease" {
+		t.Fatalf("a reading under another's lease answered %+v, %v", reads, err)
+	}
+	if again, _ := mm.store.Licence(ctx, licence1); again.Usage.ReadError != l.Usage.ReadError {
+		t.Fatalf("a reading under another's lease wrote %+v", again.Usage)
+	}
 }
 
 // design 39 bus-and-switch §25/AC1, §48: a table of readings, ages and healths and the room each gives.