diff --git a/modules/mesh-grants/cmd/mesh-grants/tools.go b/modules/mesh-grants/cmd/mesh-grants/tools.go
index beefe2b..8977fe2 100644
--- a/modules/mesh-grants/cmd/mesh-grants/tools.go
+++ b/modules/mesh-grants/cmd/mesh-grants/tools.go
@@ -159,6 +159,18 @@ func toolsOf(p *grants.Part) []stdio.Tool {
 			"every act with what became of it (asked, switched, declined, expired, refused and why).",
 			Input: schema(nil),
 			Run:   func(map[string]any) (any, error) { return p.TakeOverState() }},
+		{Name: grants.ToolLeaseCheck, Description: "The controller's lease and the controller's hand-over, in one call from bus state (issue 774, " +
+			"design 47 L3; novox/hq ADR 0547 §11, ADR 0561 §3, ADR 0571 §13): who holds the controller lease now, since when, and what " +
+			"the holder and the parts watching the lease do because of it; what still depends on the controller: every module whose " +
+			"manifest at the indexer's trunk reads a mesh-controller state, invokes a mesh-controller verb or tool, consumes or waits on " +
+			"its events, with which one and the record that keeps it until the lease write (the named keep list), the unkept ones by module; " +
+			"the controller's remaining live duties as the bus shows them: each of its streams and buckets someone consumes (with the " +
+			"durable consumers by name), and its standing assignments; and a dry run of the lease write's check (the take-over check that " +
+			"hands the lease to a holder that is no controller): whether it would pass now, at the write with only the three kept to the " +
+			"write and before the write's delivery with the whole list, each with its exact reasons, and the write's other conditions " +
+			"with the tool that answers each. Asks the controller nothing; writes nothing. Read-only.",
+			Input: schema(nil),
+			Run:   func(map[string]any) (any, error) { return p.LeaseCheck() }},
 	}
 }
 
diff --git a/modules/mesh-grants/internal/grants/leasecheck.go b/modules/mesh-grants/internal/grants/leasecheck.go
new file mode 100644
index 0000000..d88bfc5
--- /dev/null
+++ b/modules/mesh-grants/internal/grants/leasecheck.go
@@ -0,0 +1,438 @@
+package grants
+
+import (
+	"encoding/json"
+	"fmt"
+	"slices"
+	"sort"
+	"strings"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/buscompose"
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+)
+
+// **The controller's lease, what still depends on the controller, and a dry run of the lease write's check** (issue 774,
+// design 47 L3; novox/hq ADR 0547 §11, ADR 0561 §3, ADR 0571 §13). One read-only answer from bus state: the lease key,
+// every manifest the indexer holds, and the bus module's streams. It writes nothing, and asks the controller nothing.
+//
+// It lives on the grants part because the part is where the lease write takes most of its effect and already reads all
+// it needs: the lease (buscompose.NamedReaders names it), every manifest at the indexer's trunk, placement, and the bus's
+// streams through the bus module's read tools. No record names the home of the lease write's check; ADR 0571 §13 names
+// its test in three repositories, and this is the same judgement over the manifests the mesh holds now.
+
+// ToolLeaseCheck is the tool's name.
+const ToolLeaseCheck = "grants_lease_check"
+
+// Controller is the module and the seat the check is about.
+const Controller = "mesh-controller"
+
+// The kinds of a dependency on the controller, as a manifest declares them.
+const (
+	DependsRead    = "read"
+	DependsInvoke  = "invoke"
+	DependsConsume = "consume"
+	DependsUses    = "uses"
+	DependsWaits   = "waits"
+)
+
+// The phases of the lease write's check (ADR 0571 §13): before the lease write's own delivery the whole named list is
+// allowed; that delivery drops every entry but the three kept to the write itself, and its check runs with those alone.
+const (
+	PhaseBefore = "before-delivery"
+	PhaseWrite  = "write"
+)
+
+// Dependency is one declaration of a manifest other than the controller's on the controller: a read of one of its
+// states, an invoke of one of its verbs or tools, a consume or a wait on one of its events, or a send to its seat.
+type Dependency struct {
+	Module string `json:"module"`
+	// By is the account declaring it when it is not the module's own: `process <id>` or `tools <binary>`.
+	By   string `json:"by,omitempty"`
+	Kind string `json:"kind"`
+	What string `json:"what"`
+	// Kept is the record that keeps it until the lease write, from the named list; empty when none does.
+	Kept string `json:"kept,omitempty"`
+	// ToTheWrite says it is one of the three kept to the write itself, which the lease write's own delivery keeps.
+	ToTheWrite bool `json:"to_the_write,omitempty"`
+}
+
+// Kept is one entry of the named, temporary list ADR 0571 §13 allows: a read, invoke or consume another accepted record
+// keeps until the lease write, with that record. ToTheWrite marks the three kept to the write itself.
+type Kept struct {
+	Module, Kind, What, Record string
+	ToTheWrite                 bool
+}
+
+// KeepList is the named list. Each entry names the clause that keeps it; a dependency not on it fails the check. The
+// third entry kept to the write, the bus node agent's following of the controller's user list (ADR 0571 §8, ADR 0547
+// §8), is no manifest's declaration but the node-engine's own, so no manifest matches it; it stays named here so the
+// list reads as the record has it.
+var KeepList = []Kept{
+	// Kept to the write itself (ADR 0571 §4, §8, §13).
+	{Module: "mesh-delivery-builder", Kind: DependsConsume, What: "mesh-controller.artifacts-gone", Record: "ADR 0571 §4, §13", ToTheWrite: true},
+	{Module: "artifact-store-tools", Kind: DependsInvoke, What: "seat:mesh-controller.collect", Record: "ADR 0571 §4, §13", ToTheWrite: true},
+	{Module: "node-engine", Kind: DependsRead, What: "the controller's user list of the bus module's composition", Record: "ADR 0571 §8, §13; ADR 0547 §8", ToTheWrite: true},
+	// Kept until the lease write's own delivery.
+	{Module: "mesh-delivery-assigner", Kind: DependsInvoke, What: "seat:mesh-controller.placement-export", Record: "ADR 0567 §7"},
+	{Module: "mesh-delivery-assigner", Kind: DependsInvoke, What: "seat:mesh-controller.assign", Record: "ADR 0567 §8"},
+	{Module: "mesh-delivery-assigner", Kind: DependsInvoke, What: "seat:mesh-controller.unassign", Record: "ADR 0567 §8"},
+	{Module: "mesh-delivery-assigner", Kind: DependsInvoke, What: "seat:mesh-controller.pin", Record: "ADR 0567 §8"},
+	{Module: "mesh-delivery-assigner", Kind: DependsInvoke, What: "seat:mesh-controller.unpin", Record: "ADR 0567 §8"},
+	{Module: "mesh-delivery-assigner", Kind: DependsRead, What: "mesh-controller.assignments", Record: "ADR 0567 §8"},
+	{Module: "mesh-delivery-assigner", Kind: DependsRead, What: "mesh-controller.composed", Record: "ADR 0571 §8"},
+	{Module: "mesh-delivery-assigner", Kind: DependsRead, What: "mesh-controller.grants", Record: "ADR 0567 §10"},
+	{Module: "mesh-grants", Kind: DependsRead, What: "mesh-controller.assignments", Record: "ADR 0549 §5"},
+	{Module: "mesh-grants", Kind: DependsRead, What: "mesh-controller.grants", Record: "ADR 0547 §5"},
+	{Module: "mesh-grants", Kind: DependsConsume, What: "mesh-controller.condition-raised", Record: "ADR 0564 §9"},
+	{Module: "mesh-grants", Kind: DependsConsume, What: "mesh-controller.condition-cleared", Record: "ADR 0564 §9"},
+	{Module: "messenger", Kind: DependsConsume, What: "mesh-controller.condition-raised", Record: "ADR 0564 §9"},
+	{Module: "messenger", Kind: DependsConsume, What: "mesh-controller.condition-cleared", Record: "ADR 0564 §9"},
+	{Module: "messenger", Kind: DependsConsume, What: "mesh-controller.condition-changed", Record: "ADR 0564 §9"},
+	{Module: "messenger", Kind: DependsInvoke, What: "seat:mesh-controller.conditions", Record: "ADR 0564 §9"},
+	{Module: "mesh-watcher", Kind: DependsConsume, What: "mesh-controller.doctor-heartbeat", Record: "ADR 0564 §9"},
+	{Module: "mesh-conditions", Kind: DependsRead, What: "mesh-controller.conditions", Record: "ADR 0564 §9"},
+	{Module: "mesh-config", Kind: DependsRead, What: "mesh-controller.declared-config", Record: "ADR 0565 §4"},
+	{Module: "mesh-config", Kind: DependsRead, What: "mesh-controller.predefined", Record: "ADR 0565 §4"},
+	{Module: "mesh-healers", Kind: DependsRead, What: "mesh-controller.hand-acts", Record: "ADR 0565 §11"},
+	{Module: "mesh-hand-acts", Kind: DependsRead, What: "mesh-controller.hand-acts", Record: "ADR 0565 §11"},
+}
+
+// keptFor is the list's entry for one dependency, or nil.
+func keptFor(d Dependency) *Kept {
+	for i, k := range KeepList {
+		if k.Module == d.Module && k.Kind == d.Kind && k.What == d.What {
+			return &KeepList[i]
+		}
+	}
+	return nil
+}
+
+// onController says whether a name `<owner>.<rest>` is the controller's.
+func onController(name string) bool { return strings.HasPrefix(name, Controller+".") }
+
+// invokesController says whether an invoke names a verb of the controller's seat or a tool of its module. `*` names none:
+// it is the console's grant to every tool, judged by no record as a dependency.
+func invokesController(invoke string) bool {
+	if seat, _, ok := catalogue.SeatInvoke(invoke); ok {
+		return seat == Controller
+	}
+	return onController(invoke)
+}
+
+// Dependencies are every declaration on the controller in the manifests given, by module, each with the list's entry
+// that keeps it. The controller's own manifest is not judged, nor a read of its lease key: it names the lease's holder,
+// whoever that is, and parts read it to learn that the write happened (ADR 0571 §13).
+func Dependencies(manifests map[string]catalogue.Manifest) []Dependency {
+	var out []Dependency
+	add := func(module, by, kind, what string) {
+		d := Dependency{Module: module, By: by, Kind: kind, What: what}
+		if k := keptFor(d); k != nil {
+			d.Kept, d.ToTheWrite = k.Record, k.ToTheWrite
+		}
+		if !slices.Contains(out, d) {
+			out = append(out, d)
+		}
+	}
+	for name, m := range manifests {
+		if name == Controller || m.Module == Controller {
+			continue
+		}
+		for _, r := range m.Reads {
+			if onController(r) && r != buscompose.ControllerLease {
+				add(name, "", DependsRead, r)
+			}
+		}
+		for _, i := range m.Invokes {
+			if invokesController(i) {
+				add(name, "", DependsInvoke, i)
+			}
+		}
+		for _, c := range m.Consumes {
+			if onController(c) {
+				add(name, "", DependsConsume, c)
+			}
+		}
+		for _, w := range m.Waits {
+			if onController(w) {
+				add(name, "", DependsWaits, w)
+			}
+		}
+		for _, u := range m.Uses {
+			if u == Controller {
+				add(name, "", DependsUses, u)
+			}
+		}
+		for _, a := range m.BusAccounts() {
+			by := "process " + a.ID
+			if a.Tools {
+				by = "tools " + a.ID
+			}
+			for _, i := range a.Bus.Invokes {
+				if invokesController(i) {
+					add(name, by, DependsInvoke, i)
+				}
+			}
+		}
+	}
+	sort.Slice(out, func(i, j int) bool {
+		a, b := out[i], out[j]
+		if a.Module != b.Module {
+			return a.Module < b.Module
+		}
+		if a.Kind != b.Kind {
+			return a.Kind < b.Kind
+		}
+		if a.What != b.What {
+			return a.What < b.What
+		}
+		return a.By < b.By
+	})
+	return out
+}
+
+// Verdict is the lease write's check in one phase.
+type Verdict struct {
+	Phase   string   `json:"phase"`
+	Passes  bool     `json:"passes"`
+	Reasons []string `json:"reasons"`
+}
+
+// Judge runs the lease write's check over the dependencies (ADR 0571 §13) in one phase: before the lease write's own
+// delivery, every dependency must be on the named list; at the write, only the three kept to the write itself may stay.
+// A manifest that could not be read fails it too, since it could hide a dependency; and a lease already handed away
+// leaves nothing to write.
+func Judge(deps []Dependency, phase string, unread []Gap, handedAway bool, leaseSays string) Verdict {
+	v := Verdict{Phase: phase, Reasons: []string{}}
+	if handedAway {
+		v.Reasons = append(v.Reasons, "there is nothing to write: "+leaseSays)
+	}
+	for _, d := range deps {
+		who := d.Module
+		if d.By != "" {
+			who += " (" + d.By + ")"
+		}
+		switch {
+		case d.Kept == "":
+			v.Reasons = append(v.Reasons, fmt.Sprintf("%s declares %s %s, which no record keeps until the lease write (ADR 0571 §13)", who, d.Kind, d.What))
+		case phase == PhaseWrite && !d.ToTheWrite:
+			v.Reasons = append(v.Reasons, fmt.Sprintf("%s declares %s %s, kept by %s only until the lease write's own delivery, which drops it", who, d.Kind, d.What, d.Kept))
+		}
+	}
+	for _, g := range unread {
+		v.Reasons = append(v.Reasons, fmt.Sprintf("%s could not be read (%s), so what it declares on the controller is not known", g.Input, g.Why))
+	}
+	v.Passes = len(v.Reasons) == 0
+	return v
+}
+
+// LeaseNow is who holds the lease and what follows from it.
+type LeaseNow struct {
+	HandedAway bool                    `json:"handed_away"`
+	Says       string                  `json:"says"`
+	Holder     *buscompose.LeaseHolder `json:"holder,omitempty"`
+	Since      *time.Time              `json:"since,omitempty"`
+	Does       []string                `json:"does"`
+}
+
+// While the controller holds the lease, and once it is handed away: what the holder and the parts watching the key do
+// because of it, by the records that say so.
+var (
+	DoesWhileController = []string{
+		"the controller mints every new bus account; the vault mints none and says what it holds back (ADR 0561 §3)",
+		"the grants part creates no durable consumer an account needs, and only compares them (ADR 0561 §6)",
+		"the grants part publishes memberships on the controller's assignments stream beside its own state (ADR 0571 §10)",
+		"mesh-healers writes each act it would take in `would`, and acts on none (ADR 0564 §8)",
+		"the artifact sweep lets go of nothing; the controller's take-in sweeps and says `artifacts-gone` (ADR 0571 §4)",
+		"the watchman only lists dead letters; the controller keeps DEAD_LETTERS through its consumer of DEAD_LETTER_NOTICES (ADR 0564 §5)",
+		"placement proposals take only assignments, pins and config values, and the assigner keeps the controller's assignments in step (ADR 0567 §8, §9)",
+		"the controller keeps composing for the bus node, whose agent follows its user list, so the hand-backs of config, conditions, placement and the user list still answer (ADR 0547 §8, ADR 0564 §9, ADR 0565 §4, ADR 0567 §11)",
+	}
+	DoesHandedAway = []string{
+		"the vault mints every new bus account (ADR 0561 §1)",
+		"the grants part creates the durable consumers an account needs, and stops publishing on the assignments stream (ADR 0561 §6, ADR 0571 §10)",
+		"mesh-healers acts (ADR 0564 §8)",
+		"the artifact sweep sweeps and records every deletion in the hand-act log (ADR 0571 §4)",
+		"the watchman keeps the dead letters (ADR 0564 §5)",
+		"every hand-back is answered as gone (ADR 0547 §11, ADR 0564 §9, ADR 0565 §4, ADR 0567 §11)",
+	}
+)
+
+// Lease reads the lease key and says who holds it, since when, and what follows.
+func Lease(r Reader) LeaseNow {
+	raw, found, err := r.Get(ReadLease, LeaseKey)
+	away, says := buscompose.LeaseHandedAway(raw, found, err)
+	out := LeaseNow{HandedAway: away, Says: says, Does: DoesWhileController}
+	if away {
+		out.Does = DoesHandedAway
+	}
+	if err == nil && found && len(raw) > 0 {
+		var h buscompose.LeaseHolder
+		if json.Unmarshal(raw, &h) == nil {
+			out.Holder = &h
+			if !h.Taken.IsZero() {
+				t := h.Taken
+				out.Since = &t
+			}
+		}
+	}
+	return out
+}
+
+// StreamUse is one of the controller's streams (its buckets, the assignments stream, the dead-letter notices) as the bus
+// module answers it: who consumes it now, and what it last carried.
+type StreamUse struct {
+	Stream    string   `json:"stream"`
+	Consumers int      `json:"consumers"`
+	Durable   []string `json:"durable,omitempty"`
+	Messages  int64    `json:"messages"`
+	Subjects  int64    `json:"subjects_held,omitempty"`
+	Last      string   `json:"last,omitempty"`
+}
+
+// The streams of the controller's that are not its buckets: the assignments stream it publishes memberships on, and the
+// notices its consumer `controller` turns into dead letters until the lease write (ADR 0564 §5).
+const (
+	StreamAssignments       = "ASSIGNMENTS"
+	StreamDeadLetterNotices = "DEAD_LETTER_NOTICES"
+)
+
+// controllerStream says whether a stream is the controller's.
+func controllerStream(name string) bool {
+	return strings.HasPrefix(name, "KV_"+Controller+"_") || name == StreamAssignments || name == StreamDeadLetterNotices
+}
+
+// Duties reads, from the bus module's streams, every stream of the controller's someone consumes, with its durable
+// consumers by name (a watcher of a bucket is ephemeral and names nobody). Streams with no consumer are counted apart.
+func Duties(c Caller) (used []StreamUse, idle []string, err error) {
+	raw, err := c.Call(CallStreams, map[string]any{})
+	if err != nil {
+		return nil, nil, fmt.Errorf("%s: %w", CallStreams, err)
+	}
+	type consumer struct {
+		Name string `json:"name"`
+		Kind string `json:"kind"`
+		Max  int    `json:"max_deliver"`
+		Ack  string `json:"ack_policy"`
+	}
+	type stream struct {
+		Name      string     `json:"name"`
+		Consumers int        `json:"consumers"`
+		Messages  int64      `json:"messages"`
+		Held      int64      `json:"subjects_held"`
+		Last      string     `json:"last"`
+		Detail    []consumer `json:"consumer_detail"`
+	}
+	var got struct {
+		Detail []stream `json:"detail"`
+	}
+	if err := json.Unmarshal(unwrap(raw), &got); err != nil {
+		return nil, nil, fmt.Errorf("%s answered no streams: %w", CallStreams, err)
+	}
+	for _, s := range got.Detail {
+		if !controllerStream(s.Name) {
+			continue
+		}
+		if s.Consumers == 0 {
+			idle = append(idle, s.Name)
+			continue
+		}
+		u := StreamUse{Stream: s.Name, Consumers: s.Consumers, Messages: s.Messages, Subjects: s.Held, Last: s.Last}
+		if one, err := c.Call(CallStreams, map[string]any{"stream": s.Name}); err == nil {
+			var d struct {
+				Detail []stream `json:"detail"`
+			}
+			if json.Unmarshal(unwrap(one), &d) == nil && len(d.Detail) > 0 {
+				for _, cs := range d.Detail[0].Detail {
+					if durable(cs.Name) {
+						u.Durable = append(u.Durable, cs.Name)
+					}
+				}
+			}
+		}
+		used = append(used, u)
+	}
+	sort.Slice(used, func(i, j int) bool { return used[i].Stream < used[j].Stream })
+	sort.Strings(idle)
+	return used, idle, nil
+}
+
+// durable says whether a consumer's name is one a part gave it: the bus names an ephemeral watcher with eight random
+// letters and digits, which no part of the mesh uses.
+func durable(name string) bool {
+	if len(name) != 8 {
+		return true
+	}
+	for _, r := range name {
+		if !(r >= 'a' && r <= 'z' || r >= 'A' && r <= 'Z' || r >= '0' && r <= '9') {
+			return true
+		}
+	}
+	return false
+}
+
+// LeaseAnswer is the tool's answer.
+type LeaseAnswer struct {
+	Lease        LeaseNow     `json:"lease"`
+	Dependencies []Dependency `json:"dependencies"`
+	// Unkept are the dependencies no record keeps, by module: what the check refuses in every phase.
+	Unkept    map[string][]string `json:"unkept"`
+	Manifests int                 `json:"manifests_read"`
+	Unread    []Gap               `json:"manifests_unread,omitempty"`
+	// Streams are the controller's streams someone consumes now; Idle those no one does.
+	Streams      []StreamUse `json:"streams,omitempty"`
+	Idle         []string    `json:"streams_idle,omitempty"`
+	StreamsError string      `json:"streams_unread,omitempty"`
+	// Assignments is how many of the controller's assignments stand, which it publishes memberships and grants for.
+	Assignments int `json:"assignments_standing"`
+	// Check is the dry run at the write (the three alone), Before the same over the whole list before the write's
+	// delivery.
+	Check  Verdict  `json:"check"`
+	Before Verdict  `json:"check_before_delivery"`
+	Beside []string `json:"not_judged_here"`
+}
+
+// NotJudgedHere are the lease write's other conditions, each with the tool that answers it (design 47 L3, ADR 0547 §11).
+var NotJudgedHere = []string{
+	"L4 to L7 delivered: the issue tracker's milestones 1952, 1953, 1954 and 1955",
+	"every node's record trusts the vault's key: mesh-delivery-view.node_trusts (ADR 0550 §2)",
+	"mesh-config's compare empty and its take-over done, and mesh-wants.upgrade compare empty: mesh-config.compare, mesh-wants.upgrade (ADR 0565 §14)",
+	"the condition keeper's take-over done: mesh-conditions.compare (ADR 0564 §9)",
+}
+
+// LeaseCheck answers the tool: who holds the lease and what follows, every dependency on the controller with what keeps
+// it, the controller's streams in use, and the lease write's check run dry. Read-only.
+func (p *Part) LeaseCheck() (any, error) {
+	in := ReadInputs(p.Read, &p.cache)
+	out := LeaseAnswer{Lease: Lease(p.Read), Unkept: map[string][]string{}, Manifests: len(in.Manifests), Unread: in.Refused,
+		Beside: NotJudgedHere}
+	for _, g := range in.Gaps {
+		if g.Failed && strings.HasPrefix(g.Input, ReadModules) {
+			out.Unread = append(out.Unread, g)
+		}
+	}
+	out.Dependencies = Dependencies(in.Manifests)
+	if out.Dependencies == nil {
+		out.Dependencies = []Dependency{}
+	}
+	for _, d := range out.Dependencies {
+		if d.Kept == "" {
+			out.Unkept[d.Module] = append(out.Unkept[d.Module], d.Kind+" "+d.What)
+		}
+	}
+	var gaps []Gap
+	for _, raw := range each(p.Read, ReadAssignments, &gaps) {
+		var a assignment
+		if json.Unmarshal(raw, &a) == nil && a.stands() {
+			out.Assignments++
+		}
+	}
+	if used, idle, err := Duties(p.Call); err != nil {
+		out.StreamsError = err.Error()
+	} else {
+		out.Streams, out.Idle = used, idle
+	}
+	out.Check = Judge(out.Dependencies, PhaseWrite, out.Unread, out.Lease.HandedAway, out.Lease.Says)
+	out.Before = Judge(out.Dependencies, PhaseBefore, out.Unread, out.Lease.HandedAway, out.Lease.Says)
+	return out, nil
+}
diff --git a/modules/mesh-grants/internal/grants/tools.go b/modules/mesh-grants/internal/grants/tools.go
index 3c0bb57..dcc3911 100644
--- a/modules/mesh-grants/internal/grants/tools.go
+++ b/modules/mesh-grants/internal/grants/tools.go
@@ -29,7 +29,7 @@ const (
 
 // Tools is every tool, in the manifest's order.
 var Tools = []string{ToolGrants, ToolMembership, ToolUserList, ToolComposeNow, ToolAssert, ToolTakeOver, ToolHandBack, ToolTakeOverState,
-	ToolAccounts, ToolConsumerMatch, ToolAcceptHashes}
+	ToolAccounts, ToolConsumerMatch, ToolAcceptHashes, ToolLeaseCheck}
 
 // WritesGrants is what grants says of the part's own grants in this milestone: written, and read by nobody until the
 // controller's lease is handed away (delivery.GrantSource).
diff --git a/modules/mesh-grants/leasecheck_test.go b/modules/mesh-grants/leasecheck_test.go
new file mode 100644
index 0000000..e6cdd12
--- /dev/null
+++ b/modules/mesh-grants/leasecheck_test.go
@@ -0,0 +1,134 @@
+package manifest
+
+import (
+	"encoding/json"
+	"slices"
+	"strings"
+	"testing"
+
+	"mesh-grants/internal/grants"
+)
+
+// Issue 774, design 47 L3 (ADR 0547 §11, ADR 0561 §3, ADR 0571 §13): grants_lease_check answers from bus state who holds
+// the controller's lease, every manifest's dependency on the controller with what keeps it, the controller's streams in
+// use, and the lease write's check run dry, at the write (the three kept to it alone) and before its delivery.
+func TestTheLeaseCheckJudgesEveryDependencyOnTheController(t *testing.T) {
+	controllerHolds := map[string]any{"instance": "controller@novox-be pid 1 since 2026-10-30T14:52:10Z", "epoch": 60,
+		"taken": "2026-10-30T14:52:10Z", "renewed": "2026-10-30T22:00:00Z"}
+	handedAway := map[string]any{"handed-to": "the operator's hand-over", "handed-by": "operator"}
+	type want struct {
+		deps         []string // "<module> <kind> <what> <kept?>" with kept as "kept" or "unkept"
+		writePasses  bool
+		beforePasses bool
+		reason       string // a reason the check at the write must name, or ""
+		handedAway   bool
+		durable      []string // durable consumers of KV_mesh-controller_assignments
+	}
+	for _, row := range []struct {
+		name      string
+		manifests map[string]string
+		lease     map[string]any
+		want      want
+	}{
+		{"a read of the lease alone is no dependency, and the controller's own manifest is not judged",
+			map[string]string{"mod-l": `{"module":"mod-l","version":"1","reads":["mesh-controller.lease"]}`,
+				"mesh-controller": `{"module":"mesh-controller","version":"1","invokes":["seat:mesh-controller.status"]}`},
+			controllerHolds, want{writePasses: true, beforePasses: true}},
+		{"the builder's consume of artifacts-gone is kept to the write itself",
+			map[string]string{"mesh-delivery-builder": `{"module":"mesh-delivery-builder","version":"1","consumes":["mesh-controller.artifacts-gone"]}`},
+			controllerHolds, want{deps: []string{"mesh-delivery-builder consume mesh-controller.artifacts-gone kept"}, writePasses: true, beforePasses: true}},
+		{"the assigner's read of composed is kept until the write's delivery, which drops it",
+			map[string]string{"mesh-delivery-assigner": `{"module":"mesh-delivery-assigner","version":"1","reads":["mesh-controller.composed","mesh-controller.lease"]}`},
+			controllerHolds, want{deps: []string{"mesh-delivery-assigner read mesh-controller.composed kept"}, beforePasses: true,
+				reason: "mesh-delivery-assigner declares read mesh-controller.composed, kept by ADR 0571 §8 only until the lease write's own delivery"}},
+		{"a read no record keeps fails both phases, named",
+			map[string]string{"pacman": `{"module":"pacman","version":"1","reads":["mesh-controller.declared-packages"]}`},
+			controllerHolds, want{deps: []string{"pacman read mesh-controller.declared-packages unkept"},
+				reason: "pacman declares read mesh-controller.declared-packages, which no record keeps until the lease write"}},
+		{"a seat verb and a module tool of the controller's, a consume and a wait are each one; every tool (*) is none",
+			map[string]string{"mod-i": `{"module":"mod-i","version":"1","invokes":["seat:mesh-controller.root-free","mesh-controller.status","*","nats.nats_users"],` +
+				`"consumes":["mesh-controller.checked","mod-x.thing"],"uses":["mesh-controller"]}`,
+				"node-tools": `{"module":"node-tools","version":"1","waits":["mesh-controller.checked"]}`},
+			controllerHolds, want{deps: []string{"mod-i consume mesh-controller.checked unkept", "mod-i invoke mesh-controller.status unkept",
+				"mod-i invoke seat:mesh-controller.root-free unkept", "mod-i uses mesh-controller unkept", "node-tools waits mesh-controller.checked unkept"},
+				reason: "mod-i declares invoke seat:mesh-controller.root-free, which no record keeps"}},
+		{"a process's own invoke of the controller is its module's dependency, named by the process",
+			map[string]string{"mod-p": `{"module":"mod-p","version":"1","resources":[{"id":"account","type":"user","name":"mod-p"},{"id":"worker","type":"process","run":["./w"],"user":"mod-p",` +
+				`"bus":{"invokes":["seat:mesh-controller.held"]}}]}`},
+			controllerHolds, want{deps: []string{"mod-p invoke seat:mesh-controller.held unkept"},
+				reason: "mod-p (process worker) declares invoke seat:mesh-controller.held"}},
+		{"a lease already handed away leaves nothing to write",
+			map[string]string{},
+			handedAway, want{handedAway: true, reason: "there is nothing to write: the lease is handed to the operator's hand-over"}},
+	} {
+		t.Run(row.name, func(t *testing.T) {
+			b := newFakeBus()
+			for m, raw := range row.manifests {
+				b.manifestOf(m, raw)
+			}
+			b.put(grants.ReadLease, grants.LeaseKey, row.lease)
+			b.streams = []map[string]any{
+				{"name": "KV_mesh-controller_assignments", "consumers": 3, "messages": 2991, "subjects_held": 40, "last": "2026-10-30T12:55:13Z"},
+				{"name": "KV_mesh-controller_rollouts", "consumers": 0, "messages": 6652},
+				{"name": "KV_mesh-grants_memberships", "consumers": 243, "messages": 1573},
+			}
+			b.consumers = map[string][]map[string]any{"KV_mesh-controller_assignments": {{"name": "0AYfjxta"}, {"name": "1g9XJFUX"}, {"name": "grants-assignments"}}}
+			raw, err := partOn(b).LeaseCheck()
+			if err != nil {
+				t.Fatal(err)
+			}
+			var got grants.LeaseAnswer
+			data, _ := json.Marshal(raw)
+			if err := json.Unmarshal(data, &got); err != nil {
+				t.Fatal(err)
+			}
+			var deps []string
+			for _, d := range got.Dependencies {
+				kept := "unkept"
+				if d.Kept != "" {
+					kept = "kept"
+				}
+				deps = append(deps, d.Module+" "+d.Kind+" "+d.What+" "+kept)
+			}
+			if !slices.Equal(deps, row.want.deps) {
+				t.Errorf("dependencies %q, want %q", deps, row.want.deps)
+			}
+			if got.Check.Phase != grants.PhaseWrite || got.Check.Passes != row.want.writePasses {
+				t.Errorf("check at the write passes=%v (%v), want %v", got.Check.Passes, got.Check.Reasons, row.want.writePasses)
+			}
+			if got.Before.Phase != grants.PhaseBefore || got.Before.Passes != row.want.beforePasses {
+				t.Errorf("check before the delivery passes=%v (%v), want %v", got.Before.Passes, got.Before.Reasons, row.want.beforePasses)
+			}
+			if row.want.reason != "" && !slices.ContainsFunc(got.Check.Reasons, func(r string) bool { return strings.Contains(r, row.want.reason) }) {
+				t.Errorf("reasons %q name nothing like %q", got.Check.Reasons, row.want.reason)
+			}
+			if got.Lease.HandedAway != row.want.handedAway {
+				t.Errorf("lease handed away %v (%s), want %v", got.Lease.HandedAway, got.Lease.Says, row.want.handedAway)
+			}
+			if !row.want.handedAway && (got.Lease.Since == nil || got.Lease.Since.Format("15:04") != "14:52" ||
+				!strings.Contains(got.Lease.Says, "the controller holds the lease") || !slices.Equal(got.Lease.Does, grants.DoesWhileController)) {
+				t.Errorf("lease %+v: the controller's instance since 14:52, and what it does while it holds it", got.Lease)
+			}
+			if len(got.Streams) != 1 || got.Streams[0].Stream != "KV_mesh-controller_assignments" || got.Streams[0].Consumers != 3 ||
+				!slices.Equal(got.Streams[0].Durable, []string{"grants-assignments"}) || !slices.Equal(got.Idle, []string{"KV_mesh-controller_rollouts"}) {
+				t.Errorf("streams %+v idle %v: the controller's assignments bucket with its one durable consumer, the rollouts idle, no other module's", got.Streams, got.Idle)
+			}
+		})
+	}
+}
+
+// Every entry of the keep list names the record that keeps it, and exactly three are kept to the write itself (ADR 0571 §13).
+func TestTheKeepListNamesItsRecordsAndThreeToTheWrite(t *testing.T) {
+	toTheWrite := 0
+	for _, k := range grants.KeepList {
+		if !strings.HasPrefix(k.Record, "ADR ") || k.Module == "" || k.What == "" {
+			t.Errorf("entry %+v names no record, module or declaration", k)
+		}
+		if k.ToTheWrite {
+			toTheWrite++
+		}
+	}
+	if toTheWrite != 3 {
+		t.Errorf("%d entries kept to the write itself, ADR 0571 §13 names three", toTheWrite)
+	}
+}
diff --git a/modules/mesh-grants/module.json b/modules/mesh-grants/module.json
index 822b9e3..cc7ecc5 100644
--- a/modules/mesh-grants/module.json
+++ b/modules/mesh-grants/module.json
@@ -52,7 +52,8 @@
     "grants_hand_back",
     "grants_accounts",
     "grants_consumer_match",
-    "grants_accept_hashes"
+    "grants_accept_hashes",
+    "grants_lease_check"
   ],
   "state": [
     {