Merge pull request 'The mesh says what it applied, and the replay has an address it may use' (#129) from feat/the-mesh-says-what-it-applied into main

The pipeline was observable from a merge to an artifact and went dark where it touched a machine: a
node's report is control traffic only the control plane reads, so nothing said which version a
machine runs, or that it refused to (novox/hq ADR 0134). The control plane now states both under the
seat it holds — a role's events belong to the role and keep their address when the holder is
replaced — and only when the report is news, because a machine reconciles every minute and a fact per
report would be a fact per minute per machine.

Whether a report is news is the store's answer: it holds the previous one, so the listener returns it
and the server states the fact. That also gives the catch-up replay a subject the controller may
publish: it was published as a module's event from a module called "control-plane", which does not
exist, so the controller's own account refused it and every catalogue that asked what it missed was
answered with nothing.

cmd/mesh-controller/adopting_test.go

@@ -88,7 +88,7 @@ func reportsReaching(t *testing.T, open *stores, reachable []link.Reach, held ..
 	if err := open.inventory.RecordSent(ctx, record.ID, digestOf(body)); err != nil {
 		t.Fatal(err)
 	}
-	if err := (link.Enrolment{Inventory: open.inventory}).Heard(ctx, link.Report{
+	if _, err := (link.Enrolment{Inventory: open.inventory}).Heard(ctx, link.Report{
 		Node: "anchor", Applied: []string{"hello-web.x"}, Declared: digestOf(body),
 		Firewall: "ufw", Held: held, Reachable: reachable,
 	}); err != nil {

internal/broker/nats.go

@@ -181,6 +181,14 @@ func PermissionsFor(p Principal) (Permissions, error) {
 		for _, seat := range meshSeatsTheControllerUses {
 			pub = append(pub, "mesh.seat."+seat+".accept.>")
 		}
+		// **And what the mesh says it did** (novox/hq ADR 0134). The control plane states its own
+		// facts under the seat it holds, because a role's events belong to the role and keep their
+		// address while the holder is replaced. Named one by one rather than as a whole namespace:
+		// least authority, and a fact nothing states is authority nobody uses.
+		for _, event := range ControllerStates {
+			pub = append(pub, seatEventSubject(ControllerSeat, event))
+		}
+
 		// Every module's tools: **the control plane is the way in** (novox/hq ADR 0095). A person
 		// or an agent asks through it and every question passes one process where an audit
 		// belongs — so it, alone among principals, may call any tool by name. The first `ask` on

internal/broker/states_agreement_test.go

@@ -0,0 +1,30 @@
+package broker_test
+
+import (
+	"slices"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/broker"
+	"github.com/novox/mesh-controller/internal/link"
+)
+
+// The facts the control plane states are named twice — in the grant that permits them and in the code
+// that states them — because `link` imports `broker` and the dependency cannot go the other way. So a
+// test keeps them agreeing: a subject the grant omits is refused at the moment the mesh has something
+// to say, and one the grant adds that nothing states is authority nobody uses.
+//
+// An external test package, because it may import both while neither imports the other.
+func TestTheFactsTheGrantPermitsAreTheFactsTheMeshStates(t *testing.T) {
+	if broker.ControllerSeat != link.MeshControllerSeat {
+		t.Fatalf("the grant is written for the %q seat and the mesh states its facts under %q",
+			broker.ControllerSeat, link.MeshControllerSeat)
+	}
+	for _, event := range []string{link.KeyApplied, link.KeyRefused, link.KeyBuiltBefore} {
+		if !slices.Contains(broker.ControllerStates, event) {
+			t.Errorf("the mesh states %q and its account may not publish it", event)
+		}
+	}
+	if len(broker.ControllerStates) != 3 {
+		t.Errorf("the grant permits %v, which is more than the mesh states", broker.ControllerStates)
+	}
+}

internal/broker/streams.go

@@ -160,6 +160,17 @@ func Overlaps() []string {
 // ack subject is derived from (nats.go: `$JS.ACK.<stream>.controller.>`).
 const ControllerName = "controller"
 
+// ControllerSeat is the role the control plane holds, and ControllerStates are the facts it states
+// under it (novox/hq ADR 0134).
+//
+// **Written here as well as in `link`, and a test keeps them agreeing.** `link` imports `broker`, so
+// `broker` cannot import `link`; a grant naming a subject the controller never publishes is authority
+// nobody uses, and a controller publishing one the grant omits is refused at the moment it has
+// something to say.
+const ControllerSeat = "mesh-controller"
+
+var ControllerStates = []string{"applied", "refused", "built-before"}
+
 // ControllerFollows are the events the controller reacts to: the catalogue saying a module's
 // current version moved, and a catalogue that has just started saying it may have missed builds.
 //

internal/broker/testdata/composed.conf

@@ -24,7 +24,7 @@ accounts {
     jetstream: enabled
     users = [
       { user: "controller", password: "$2a$11$cccccccccccccccccccccc", permissions: {
-        publish: { allow: ["$JS.ACK.CONTROL.controller.>", "$JS.ACK.EVENTS.controller.>", "$JS.API.>", "_INBOX.enrol.>", "mesh.control.>", "mesh.mod.*.tool.>", "mesh.node.>", "mesh.seat.mesh-build-machine.accept.>"] }
+        publish: { allow: ["$JS.ACK.CONTROL.controller.>", "$JS.ACK.EVENTS.controller.>", "$JS.API.>", "_INBOX.enrol.>", "mesh.control.>", "mesh.mod.*.tool.>", "mesh.node.>", "mesh.seat.mesh-build-machine.accept.>", "mesh.seat.mesh-controller.event.applied", "mesh.seat.mesh-controller.event.built-before", "mesh.seat.mesh-controller.event.refused"] }
         subscribe: { allow: ["$JS.API.>", "_DELIVER.controller", "_DELIVER.controller.>", "_INBOX.controller.>", "mesh.control.>", "mesh.mod.gitea.event.pull.merged", "mesh.mod.mesh-catalog.event.catching-up", "mesh.mod.mesh-catalog.event.upgraded", "mesh.seat.mesh-build-machine.event.built"] }
         allow_responses: { max: 1, ttl: "1m" }
       } }

internal/inventory/doing_test.go

@@ -30,12 +30,12 @@ func TestRefusedAndFailedAreDifferentSituations(t *testing.T) {
 	refuser := nodeNamed(t, inv, "refuser")
 	failer := nodeNamed(t, inv, "failer")
 
-	if err := inv.RecordDoing(ctx, refuser, Doing{
+	if _, err := inv.RecordDoing(ctx, refuser, Doing{
 		Outcome: OutcomeRefused, Refused: "resource \"x\": a file needs a path",
 	}); err != nil {
 		t.Fatal(err)
 	}
-	if err := inv.RecordDoing(ctx, failer, Doing{
+	if _, err := inv.RecordDoing(ctx, failer, Doing{
 		Outcome: OutcomeFailed,
 		Failed:  []FailedResource{{ID: "svc", Error: "unit not found"}},
 		Applied: 4,
@@ -70,7 +70,7 @@ func TestAMachineDoingWhatItWasToldIsNotOnTheList(t *testing.T) {
 	inv := fresh(t)
 	ctx := context.Background()
 	id := nodeNamed(t, inv, "fine")
-	if err := inv.RecordDoing(ctx, id, Doing{Outcome: OutcomeApplied, Applied: 6}); err != nil {
+	if _, err := inv.RecordDoing(ctx, id, Doing{Outcome: OutcomeApplied, Applied: 6}); err != nil {
 		t.Fatal(err)
 	}
 	wrong, err := inv.NotDoingWhatTheyWereTold(ctx)
@@ -97,12 +97,12 @@ func TestTheLastReportReplacesTheOneBefore(t *testing.T) {
 	inv := fresh(t)
 	ctx := context.Background()
 	id := nodeNamed(t, inv, "recovered")
-	if err := inv.RecordDoing(ctx, id, Doing{
+	if _, err := inv.RecordDoing(ctx, id, Doing{
 		Outcome: OutcomeFailed, Failed: []FailedResource{{ID: "a", Error: "no"}},
 	}); err != nil {
 		t.Fatal(err)
 	}
-	if err := inv.RecordDoing(ctx, id, Doing{Outcome: OutcomeApplied, Applied: 3}); err != nil {
+	if _, err := inv.RecordDoing(ctx, id, Doing{Outcome: OutcomeApplied, Applied: 3}); err != nil {
 		t.Fatal(err)
 	}
 	wrong, err := inv.NotDoingWhatTheyWereTold(ctx)
@@ -141,7 +141,7 @@ func TestWhatANodeSaidGoesWhenTheNodeDoes(t *testing.T) {
 	inv := fresh(t)
 	ctx := context.Background()
 	id := nodeNamed(t, inv, "leaving")
-	if err := inv.RecordDoing(ctx, id, Doing{Outcome: OutcomeFailed}); err != nil {
+	if _, err := inv.RecordDoing(ctx, id, Doing{Outcome: OutcomeFailed}); err != nil {
 		t.Fatal(err)
 	}
 	if _, err := inv.store.Pool().Exec(ctx, `delete from node where name = 'leaving'`); err != nil {
@@ -257,7 +257,7 @@ func TestTheSameFailureReportedAgainIsCountedNotRestarted(t *testing.T) {
 	id := nodeNamed(t, inv, "looping")
 	same := Doing{Outcome: OutcomeFailed, Failed: []FailedResource{{ID: "img", Error: "no such image"}}}
 
-	if err := inv.RecordDoing(ctx, id, same); err != nil {
+	if _, err := inv.RecordDoing(ctx, id, same); err != nil {
 		t.Fatal(err)
 	}
 	first, _, err := inv.DoingOf(ctx, "looping")
@@ -269,7 +269,7 @@ func TestTheSameFailureReportedAgainIsCountedNotRestarted(t *testing.T) {
 	}
 
 	for range StuckAfter - 1 {
-		if err := inv.RecordDoing(ctx, id, same); err != nil {
+		if _, err := inv.RecordDoing(ctx, id, same); err != nil {
 			t.Fatal(err)
 		}
 	}
@@ -287,7 +287,7 @@ func TestTheSameFailureReportedAgainIsCountedNotRestarted(t *testing.T) {
 	// The same resource failing with different words — a duration, a counter — is still the same
 	// failure: it is the resource that loops, not the sentence.
 	reworded := Doing{Outcome: OutcomeFailed, Failed: []FailedResource{{ID: "img", Error: "no such image (after 31s)"}}}
-	if err := inv.RecordDoing(ctx, id, reworded); err != nil {
+	if _, err := inv.RecordDoing(ctx, id, reworded); err != nil {
 		t.Fatal(err)
 	}
 	still, _, err := inv.DoingOf(ctx, "looping")
@@ -300,7 +300,7 @@ func TestTheSameFailureReportedAgainIsCountedNotRestarted(t *testing.T) {
 
 	// A different failure is a new situation, not a longer one.
 	other := Doing{Outcome: OutcomeFailed, Failed: []FailedResource{{ID: "svc", Error: "unit not found"}}}
-	if err := inv.RecordDoing(ctx, id, other); err != nil {
+	if _, err := inv.RecordDoing(ctx, id, other); err != nil {
 		t.Fatal(err)
 	}
 	changed, _, err := inv.DoingOf(ctx, "looping")
@@ -312,7 +312,7 @@ func TestTheSameFailureReportedAgainIsCountedNotRestarted(t *testing.T) {
 	}
 
 	// And a clean apply clears it: the machine is doing what it was told, since nothing.
-	if err := inv.RecordDoing(ctx, id, Doing{Outcome: OutcomeApplied, Applied: 2}); err != nil {
+	if _, err := inv.RecordDoing(ctx, id, Doing{Outcome: OutcomeApplied, Applied: 2}); err != nil {
 		t.Fatal(err)
 	}
 	fine, _, err := inv.DoingOf(ctx, "looping")
@@ -324,7 +324,7 @@ func TestTheSameFailureReportedAgainIsCountedNotRestarted(t *testing.T) {
 	}
 
 	// The list of what is wrong carries the count, so `status` can say it.
-	if err := inv.RecordDoing(ctx, id, same); err != nil {
+	if _, err := inv.RecordDoing(ctx, id, same); err != nil {
 		t.Fatal(err)
 	}
 	wrong, err := inv.NotDoingWhatTheyWereTold(ctx)

internal/inventory/nodes.go

@@ -670,31 +670,39 @@ func sameFailure(a, b Doing) bool {
 // a clean apply clears both (novox/hq 04-ISSUES/065). The previous row is read first and the
 // comparison made here, so "the same" is a rule this package states rather than a jsonb equality
 // that would restart the count on a changed word in an error.
-func (i *Inventory) RecordDoing(ctx context.Context, node string, d Doing) error {
+// **And whether this report was news**, which is what makes a fact about it worth stating (novox/hq
+// ADR 0134). A machine reconciles continuously and reports each time; the same outcome about the same
+// declaration is the same state said again, and a fact per report would be a fact per minute per
+// machine that tells nobody anything. Read here because the previous row is read here anyway.
+func (i *Inventory) RecordDoing(ctx context.Context, node string, d Doing) (news bool, err error) {
 	failed, err := json.Marshal(d.Failed)
 	if err != nil {
-		return err
+		return false, err
+	}
+	var before Doing
+	var beforeFailed []byte
+	found := i.store.Pool().QueryRow(ctx,
+		`select outcome, refused, failed, failing_since, failures, coalesce(declared,'')
+		   from node_report where node = $1`,
+		node).Scan(&before.Outcome, &before.Refused, &beforeFailed, &before.Since, &before.Times,
+		&before.Declared)
+	switch {
+	case errors.Is(found, pgx.ErrNoRows):
+		news = true
+	case found != nil:
+		return false, found
+	default:
+		if err := json.Unmarshal(beforeFailed, &before.Failed); err != nil {
+			return false, err
+		}
+		news = before.Outcome != d.Outcome || before.Declared != d.Declared || !sameFailure(before, d)
 	}
 	var since *time.Time
 	times := 0
 	if d.Outcome != OutcomeApplied {
-		var before Doing
-		var beforeFailed []byte
-		err := i.store.Pool().QueryRow(ctx,
-			`select outcome, refused, failed, failing_since, failures from node_report where node = $1`,
-			node).Scan(&before.Outcome, &before.Refused, &beforeFailed, &before.Since, &before.Times)
-		switch {
-		case errors.Is(err, pgx.ErrNoRows):
-		case err != nil:
-			return err
-		default:
-			if err := json.Unmarshal(beforeFailed, &before.Failed); err != nil {
-				return err
-			}
-		}
 		now := time.Now()
 		since, times = &now, 1
-		if err == nil && sameFailure(before, d) && before.Since != nil {
+		if found == nil && sameFailure(before, d) && before.Since != nil {
 			since, times = before.Since, before.Times+1
 		}
 	}
@@ -707,7 +715,10 @@ func (i *Inventory) RecordDoing(ctx context.Context, node string, d Doing) error
 		   declared = excluded.declared,
 		   failing_since = excluded.failing_since, failures = excluded.failures`,
 		node, d.Outcome, d.Refused, failed, d.Applied, d.Declared, since, times)
-	return err
+	if err != nil {
+		return false, err
+	}
+	return news, nil
 }
 
 // NotDoingWhatTheyWereTold is every machine whose last report was not a clean apply.

internal/link/bus.go

@@ -30,6 +30,11 @@ type Bus interface {
 	// (design 29 §4, the *state* shape).
 	PublishDeclaration(ctx context.Context, node string, body []byte) error
 
+	// PublishSeatEvent states a fact under a role's own name, for the holder of that role. A
+	// module's event is addressed to the module; a role's is addressed to the role, so it keeps
+	// meaning when the holder changes (novox/hq ADR 0121, ADR 0129).
+	PublishSeatEvent(ctx context.Context, seat, event string, body []byte) error
+
 	// AskTool sends one question to a module's tool and awaits one answer. A tool nobody serves
 	// must say so **at once** rather than after the whole wait: the difference between "that
 	// module is down" and "that tool is slow" is the first thing a person asking wants.
@@ -81,6 +86,13 @@ func EventSubject(source, key string) string {
 	return "mesh.mod." + source + ".event." + key
 }
 
+// SeatEventSubject is where a role's own event lands. Derived from the role, never from its holder:
+// a fact about the build machine or about the control plane keeps its address when the module holding
+// that role is replaced (novox/hq ADR 0121, ADR 0129).
+func SeatEventSubject(seat, event string) string {
+	return "mesh.seat." + seat + ".event." + event
+}
+
 // DeclareSubject is where one node's declaration lands. Last-per-subject on the NODES stream, so
 // a node that was away gets exactly the current one and a replayed older one is refused by
 // sequence — the wire-level answer to novox/hq issue 107.
@@ -112,6 +124,27 @@ func (b OverNATS) PublishEvent(ctx context.Context, key, source, node string, bo
 	return nil
 }
 
+// PublishSeatEvent states a role's own fact. Same envelope as a module's event and a different
+// address: the source header is the role, because that is what the fact is about.
+func (b OverNATS) PublishSeatEvent(ctx context.Context, seat, event string, body []byte) error {
+	id, err := eventID()
+	if err != nil {
+		return err
+	}
+	h := nats.Header{}
+	h.Set("x-event-id", id)
+	h.Set("x-source", seat)
+	_, err = b.JS.PublishMsg(&nats.Msg{
+		Subject: SeatEventSubject(seat, event),
+		Header:  h,
+		Data:    body,
+	}, nats.MsgId(id), nats.Context(ctx))
+	if err != nil {
+		return fmt.Errorf("stating %s of the %s seat: %w", event, seat, err)
+	}
+	return nil
+}
+
 func (b OverNATS) PublishDeclaration(ctx context.Context, node string, body []byte) error {
 	_, err := b.JS.Publish(DeclareSubject(node), body, nats.Context(ctx))
 	if err != nil {

internal/link/enrolment.go

@@ -265,7 +265,7 @@ func (e Enrolment) Outstanding(ctx context.Context, node string) (string, error)
 	return e.Inventory.Outstanding(ctx, node)
 }
 
-func (e Enrolment) Heard(ctx context.Context, report Report) (err error) {
+func (e Enrolment) Heard(ctx context.Context, report Report) (news bool, err error) {
 	// A store that could not be asked right now is said as such, so the report is kept for
 	// another attempt rather than acknowledged and lost (novox/hq issue 082).
 	defer func() {
@@ -274,11 +274,11 @@ func (e Enrolment) Heard(ctx context.Context, report Report) (err error) {
 		}
 	}()
 	if report.Node == "" {
-		return errors.New("a report named no node")
+		return false, errors.New("a report named no node")
 	}
 	node, err := e.Inventory.NodeByName(ctx, report.Node)
 	if err != nil {
-		return err
+		return false, err
 	}
 
 	// What an adopted node holds, which firewall it found, and what is reachable on it (novox/hq
@@ -298,7 +298,7 @@ func (e Enrolment) Heard(ctx context.Context, report Report) (err error) {
 				Port: r.Port, By: r.By, Published: r.Published, ContainerPort: r.ContainerPort})
 		}
 		if err := e.Inventory.RecordAdoption(ctx, node.ID, held, report.Firewall, reachable); err != nil {
-			return err
+			return false, err
 		}
 	}
 	// What it says about the tunnel it carried (novox/hq ADR 0105), whenever it says it.
@@ -308,7 +308,7 @@ func (e Enrolment) Heard(ctx context.Context, report Report) (err error) {
 			Peers: report.Tunnel.Peers, State: report.Tunnel.State, Note: report.Tunnel.Note,
 			Kept: report.Tunnel.Kept,
 		}); err != nil {
-			return err
+			return false, err
 		}
 	}
 	// A node taking a found tunnel's key after enrolment (novox/hq ADR 0105). Verified against the
@@ -317,9 +317,9 @@ func (e Enrolment) Heard(ctx context.Context, report Report) (err error) {
 	// does not verify or is stale — a refusal, not "not now", so the node hears why.
 	if report.Rekey != nil {
 		if err := e.rekey(ctx, node, *report.Rekey); err != nil {
-			return err
+			return false, err
 		}
-		return e.Inventory.Seen(ctx, node.ID)
+		return false, e.Inventory.Seen(ctx, node.ID)
 	}
 
 	// A bare word that a node is there is not an account of what the machine did or holds: it
@@ -334,7 +334,7 @@ func (e Enrolment) Heard(ctx context.Context, report Report) (err error) {
 		if report.Superseded != "" {
 			log.Printf("%s set aside declaration %s for the newer %s", report.Node, report.Declared, report.Superseded)
 		}
-		return e.Inventory.Seen(ctx, node.ID)
+		return false, e.Inventory.Seen(ctx, node.ID)
 	}
 	// What it did is kept whichever way it went. Until this, a refusal or a failure moved
 	// last_seen and the reason went to a log line, so "which machine is not doing what it was
@@ -361,17 +361,20 @@ func (e Enrolment) Heard(ctx context.Context, report Report) (err error) {
 	// on top of it (novox/hq ADR 0038). Kept even when the declaration was refused: what the
 	// machine carries is true regardless of what it thought of the last thing it was sent.
 	if err := e.Inventory.RecordCarried(ctx, report.Node, report.Carried); err != nil {
-		return err
+		return false, err
 	}
-	if err := e.Inventory.RecordDoing(ctx, node.ID, doing); err != nil {
-		return err
+	// **Whether this is news** is the store's answer: it holds the previous report, and a machine
+	// that reconciles every minute says the same thing until something changes (novox/hq ADR 0134).
+	news, err = e.Inventory.RecordDoing(ctx, node.ID, doing)
+	if err != nil {
+		return false, err
 	}
 
 	// A refusal, a failure, or a bare word that the node is there — none of them is an account of
 	// what the machine holds, so each moves last_seen and nothing else. Recording a partial list
 	// as though it were the whole would tell a rebuilding node to remove what it still has.
 	if report.Refused != "" || len(report.Failed) > 0 || report.Applied == nil {
-		return e.Inventory.Seen(ctx, node.ID)
+		return news, e.Inventory.Seen(ctx, node.ID)
 	}
-	return e.Inventory.RecordOwned(ctx, node.ID, report.Applied)
+	return news, e.Inventory.RecordOwned(ctx, node.ID, report.Applied)
 }

internal/link/events.go

@@ -49,6 +49,39 @@ func eventID() (string, error) {
 	return hex.EncodeToString(raw), nil
 }
 
+// MeshControllerSeat is the role the control plane holds, and therefore where its own facts live: a
+// role's events belong to the role, not to whichever container is holding it today (novox/hq ADR 0121,
+// ADR 0129). It is what makes them addressable while the control plane itself is being replaced.
+const MeshControllerSeat = "mesh-controller"
+
+// The facts the mesh states about its own work (novox/hq ADR 0134).
+const (
+	// KeyApplied: a machine now runs what it was sent.
+	KeyApplied = "applied"
+	// KeyRefused: a machine did not take what it was sent, and why.
+	KeyRefused = "refused"
+	// KeyBuiltBefore: a build the mesh already held, for a catalogue that asked what it missed. Not
+	// `built` — that is the build machine's, said as it happens, and a replay is neither.
+	KeyBuiltBefore = "built-before"
+)
+
+// Applied is what a machine now runs, as the mesh states it.
+type Applied struct {
+	Node     string `json:"node"`
+	Declared string `json:"declared,omitempty"`
+	// Resources is how many the machine applied, not which: the list is the machine's own account
+	// of itself and belongs in the records, not in a fact every listener has to read past.
+	Resources int `json:"resources"`
+}
+
+// Refused is a machine that would not take what it was sent.
+type Refused struct {
+	Node     string            `json:"node"`
+	Declared string            `json:"declared,omitempty"`
+	Refused  string            `json:"refused,omitempty"`
+	Failed   map[string]string `json:"failed,omitempty"`
+}
+
 // KeyModuleBuilt is what the builder announces when it has built something. The catalogue places
 // it in the module graph; nothing else need care.
 const KeyModuleBuilt = "module.builder.built"

internal/link/heard_test.go

@@ -22,7 +22,7 @@ func heardFrom(t *testing.T, report link.Report) (*inventory.Inventory, inventor
 	if _, err := inv.AddNode(ctx, report.Node); err != nil {
 		t.Fatal(err)
 	}
-	if err := (link.Enrolment{Inventory: inv}).Heard(ctx, report); err != nil {
+	if _, err := (link.Enrolment{Inventory: inv}).Heard(ctx, report); err != nil {
 		t.Fatal(err)
 	}
 	doing, said, err := inv.DoingOf(ctx, report.Node)
@@ -103,7 +103,7 @@ func TestABareAliveDoesNotWipeTheDeclarationThatSaysANodeIsCurrent(t *testing.T)
 	if err := inv.RecordSent(ctx, node.ID, digest); err != nil {
 		t.Fatal(err)
 	}
-	if err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{
+	if _, err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{
 		Node: "anchor", Applied: []string{"a", "b"}, Declared: digest, Carried: []int{5432},
 	}); err != nil {
 		t.Fatal(err)
@@ -126,7 +126,7 @@ func TestABareAliveDoesNotWipeTheDeclarationThatSaysANodeIsCurrent(t *testing.T)
 	}
 
 	// Now the node says only that it is there, as it does every minute.
-	if err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{Node: "anchor"}); err != nil {
+	if _, err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{Node: "anchor"}); err != nil {
 		t.Fatal(err)
 	}
 	if !currentOf("anchor") {
@@ -162,7 +162,7 @@ func TestAFailureDoesNotBecomeTheAccountOfWhatTheMachineHolds(t *testing.T) {
 	if err := inv.RecordOwned(ctx, node.ID, []string{"one", "two", "three"}); err != nil {
 		t.Fatal(err)
 	}
-	if err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{
+	if _, err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{
 		Node: "workstation", Applied: []string{"one"}, Failed: map[string]string{"two": "no"},
 	}); err != nil {
 		t.Fatal(err)
@@ -200,13 +200,13 @@ func TestWhatAnAdoptedNodeHoldsIsKeptAndAnAliveWordDoesNotWipeIt(t *testing.T) {
 	}
 	check("after the report")
 
-	if err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{Node: "anchor"}); err != nil {
+	if _, err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{Node: "anchor"}); err != nil {
 		t.Fatal(err)
 	}
 	check("after an alive word")
 
 	// A reconcile report carrying only adoption is recorded, though it applied nothing.
-	if err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{Node: "anchor",
+	if _, err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{Node: "anchor",
 		Firewall: "ufw"}); err != nil {
 		t.Fatal(err)
 	}

internal/link/receive_nats_test.go

@@ -86,14 +86,15 @@ type counted struct {
 	heard []Report
 }
 
-func (c *counted) Heard(_ context.Context, r Report) error {
+func (c *counted) Heard(_ context.Context, r Report) (bool, error) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	if c.err != nil {
-		return c.err
+		return false, c.err
 	}
 	c.heard = append(c.heard, r)
-	return nil
+	// News, so what the mesh states about a report is exercised wherever a report is.
+	return true, nil
 }
 
 func (c *counted) refusing(err error) {
@@ -207,11 +208,11 @@ type sentAndHeardSafely struct {
 	heard []Report
 }
 
-func (s *sentAndHeardSafely) Heard(_ context.Context, r Report) error {
+func (s *sentAndHeardSafely) Heard(_ context.Context, r Report) (bool, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	s.heard = append(s.heard, r)
-	return nil
+	return true, nil
 }
 
 func (s *sentAndHeardSafely) Outstanding(context.Context, string) (string, error) {
@@ -451,4 +452,108 @@ func TestNatsWorkSlowerThanTheWindowIsNotHandedOverAgain(t *testing.T) {
 // slowly is a listener that runs whatever it was given.
 type slowly struct{ work func() }
 
-func (s slowly) Heard(context.Context, Report) error { s.work(); return nil }
+func (s slowly) Heard(context.Context, Report) (bool, error) { s.work(); return true, nil }
+
+// **The mesh says what it applied** (novox/hq ADR 0134), under the seat the control plane holds — and
+// says nothing when a report is the same state said again, which is what a machine reconciling every
+// minute sends.
+func TestNatsTheMeshSaysWhatAMachineApplied(t *testing.T) {
+	js := aBus(t)
+	heard := make(chan *nats.Msg, 4)
+	sub, err := js.Conn().Subscribe(SeatEventSubject(MeshControllerSeat, ">"), func(m *nats.Msg) {
+		heard <- m
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer sub.Unsubscribe() //nolint:errcheck // the subscription dies with the connection
+
+	_, stop := servingOn(t, js, &counted{})
+	defer stop()
+
+	// A report that changed something: the store says it was news.
+	body, err := json.Marshal(Report{Node: "anchor", Declared: "d1", Applied: []string{"store", "broker"}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := js.Context().Publish(ReportSubject("anchor"), body); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case m := <-heard:
+		if m.Subject != SeatEventSubject(MeshControllerSeat, KeyApplied) {
+			t.Fatalf("the mesh stated %q", m.Subject)
+		}
+		var said Applied
+		if err := json.Unmarshal(m.Data, &said); err != nil {
+			t.Fatal(err)
+		}
+		if said.Node != "anchor" || said.Declared != "d1" || said.Resources != 2 {
+			t.Fatalf("it said %+v", said)
+		}
+	case <-time.After(10 * time.Second):
+		t.Fatal("the mesh said nothing about a machine that now runs something else")
+	}
+
+	// A refusal is its own fact, with the reason in it rather than only in a log.
+	refusal, err := json.Marshal(Report{Node: "anchor", Declared: "d2",
+		Failed: map[string]string{"gitea.server": "no such image"}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := js.Context().Publish(ReportSubject("anchor"), refusal); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case m := <-heard:
+		if m.Subject != SeatEventSubject(MeshControllerSeat, KeyRefused) {
+			t.Fatalf("a refusal was stated as %q", m.Subject)
+		}
+		var said Refused
+		if err := json.Unmarshal(m.Data, &said); err != nil {
+			t.Fatal(err)
+		}
+		if said.Failed["gitea.server"] == "" {
+			t.Fatalf("the refusal does not say which resource or why: %+v", said)
+		}
+	case <-time.After(10 * time.Second):
+		t.Fatal("the mesh said nothing about a machine that refused what it was sent")
+	}
+}
+
+// And a report that is not news is not a fact. A machine reconciles every minute; a fact per report
+// would be a fact per minute per machine, which is a stream nobody reads.
+func TestNatsAReportThatIsNotNewsIsNotStated(t *testing.T) {
+	js := aBus(t)
+	heard := make(chan *nats.Msg, 4)
+	sub, err := js.Conn().Subscribe(SeatEventSubject(MeshControllerSeat, ">"), func(m *nats.Msg) {
+		heard <- m
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer sub.Unsubscribe() //nolint:errcheck // the subscription dies with the connection
+
+	// A store that records the report and says it was nothing new — which is what the mesh's own
+	// store says about a machine repeating itself.
+	_, stop := servingOn(t, js, sameAgain{})
+	defer stop()
+
+	body, err := json.Marshal(Report{Node: "anchor", Declared: "d1", Applied: []string{"store"}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := js.Context().Publish(ReportSubject("anchor"), body); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case m := <-heard:
+		t.Fatalf("the mesh stated %q about a machine that changed nothing", m.Subject)
+	case <-time.After(3 * time.Second):
+	}
+}
+
+// sameAgain records a report and says it was the same state said again.
+type sameAgain struct{}
+
+func (sameAgain) Heard(context.Context, Report) (bool, error) { return false, nil }

internal/link/rekey_test.go

@@ -60,7 +60,7 @@ func TestASignedRekeyMovesTheHubOntoItsTunnel(t *testing.T) {
 	rekey := &link.Rekey{Previous: ownKey, OverlayKey: tunnelKey, Tunnel: theTunnel()}
 	rekey.Proof = ed25519.Sign(private, link.RekeyProof("anchor", ownKey, tunnelKey, theTunnel()))
 
-	if err := e.Heard(ctx, link.Report{Node: "anchor", Rekey: rekey}); err != nil {
+	if _, err := e.Heard(ctx, link.Report{Node: "anchor", Rekey: rekey}); err != nil {
 		t.Fatal(err)
 	}
 	placed, err := e.Inventory.Overlays(ctx)
@@ -77,7 +77,7 @@ func TestASignedRekeyMovesTheHubOntoItsTunnel(t *testing.T) {
 	_ = hub
 
 	// Replayed, it is stale: the previous key it names is no longer the node's.
-	err = e.Heard(ctx, link.Report{Node: "anchor", Rekey: rekey})
+	_, err = e.Heard(ctx, link.Report{Node: "anchor", Rekey: rekey})
 	if err == nil || !strings.Contains(err.Error(), "previous overlay key") {
 		t.Fatalf("a replayed rekey was accepted: %v", err)
 	}
@@ -93,7 +93,7 @@ func TestARekeySignedByAnotherKeyIsRefusedAndChangesNothing(t *testing.T) {
 	rekey := &link.Rekey{Previous: ownKey, OverlayKey: tunnelKey, Tunnel: theTunnel()}
 	rekey.Proof = ed25519.Sign(stranger, link.RekeyProof("anchor", ownKey, tunnelKey, theTunnel()))
 
-	err = e.Heard(ctx, link.Report{Node: "anchor", Rekey: rekey})
+	_, err = e.Heard(ctx, link.Report{Node: "anchor", Rekey: rekey})
 	if err == nil || !strings.Contains(err.Error(), "not signed by anchor's identity key") {
 		t.Fatalf("a rekey signed by a stranger was accepted: %v", err)
 	}
@@ -111,7 +111,7 @@ func TestARekeySignedByAnotherKeyIsRefusedAndChangesNothing(t *testing.T) {
 	other := theTunnel()
 	other.Port = 51820
 	moved.Proof = ed25519.Sign(mustPrivate(t, e, "anchor"), link.RekeyProof("anchor", ownKey, tunnelKey, other))
-	if err := e.Heard(ctx, link.Report{Node: "anchor", Rekey: moved}); err == nil {
+	if _, err := e.Heard(ctx, link.Report{Node: "anchor", Rekey: moved}); err == nil {
 		t.Fatal("a proof over another tunnel was accepted")
 	}
 }

internal/link/report_retry_test.go

@@ -9,12 +9,12 @@ import (
 
 type heardWith struct{ err error }
 
-func (h heardWith) Heard(context.Context, Report) error { return h.err }
+func (h heardWith) Heard(context.Context, Report) (bool, error) { return h.err == nil, h.err }
 
 // switchable answers with whatever it is set to — the store away, then back.
 type switchable struct{ err error }
 
-func (h *switchable) Heard(context.Context, Report) error { return h.err }
+func (h *switchable) Heard(context.Context, Report) (bool, error) { return h.err == nil, h.err }
 
 func aReport(node, declared string) Report {
 	return Report{Node: node, Declared: declared, Applied: []string{"store"}}

internal/link/serve.go

@@ -29,7 +29,12 @@ type Enroller interface {
 // Listener is what the controller does with a report. Separate from Enroller so the two can be
 // given independently, and so a server that only sends declarations needs neither.
 type Listener interface {
-	Heard(ctx context.Context, report Report) error
+	// Heard records what a node said, and says whether it was **news** — a machine that now runs
+	// something else, or refuses something it did not refuse before. A machine reconciles
+	// continuously and reports each time, so what is news is the store's answer rather than the
+	// bus's: only this side has the previous report to compare with. What the mesh states about it
+	// is the server's (novox/hq ADR 0134).
+	Heard(ctx context.Context, report Report) (news bool, err error)
 }
 
 // Recorder keeps what builders say.
@@ -257,7 +262,7 @@ func (s *Server) heartbeat(m Control) {
 		return
 	}
 	if s.listener != nil {
-		if err := s.listener.Heard(context.Background(), Report{Node: alive.Node}); err != nil {
+		if _, err := s.listener.Heard(context.Background(), Report{Node: alive.Node}); err != nil {
 			s.log.Printf("could not record that %s is here: %v", alive.Node, err)
 		}
 	}
@@ -291,7 +296,7 @@ func (s *Server) reported(ctx context.Context, m Control) {
 			return
 		}
 
-		err := s.listener.Heard(context.Background(), report)
+		news, err := s.listener.Heard(context.Background(), report)
 		switch s.decide(ctx, m, what, declaredIn, outstanding, err) {
 		case Hold:
 			// Held, not settled, while the store cannot take it: the node reports an apply once,
@@ -307,6 +312,13 @@ func (s *Server) reported(ctx context.Context, m Control) {
 			// node whose recovery copy is silently older than it looks.
 			s.log.Printf("could not record %s's report: %v", report.Node, err)
 		}
+		// **And the mesh says what it did** (novox/hq ADR 0134). Only when the report was news: a
+		// machine reports every convergence, and a fact per report would be a fact per minute per
+		// machine saying nothing. Stated after it is recorded, so nothing is announced that the
+		// mesh does not hold.
+		if err == nil && news {
+			s.saysWhatItDid(ctx, report)
+		}
 	}
 
 	switch {
@@ -460,7 +472,11 @@ func (s *Server) catchingUp(ctx context.Context, m Control) {
 	sent := 0
 	for _, a := range announcements {
 		a.Replay = true
-		if err := EmitEvent(ctx, s.bus, KeyModuleBuilt, "control-plane", "", a); err != nil {
+		// Under the control plane's own seat (novox/hq ADR 0134). It used to be published as a
+		// module's event from a module called "control-plane", which does not exist — so the
+		// controller's own account refused it, every catalogue that asked what it missed was
+		// answered with nothing, and its graph kept the gap (found 2026-09-28).
+		if err := s.bus.PublishSeatEvent(ctx, MeshControllerSeat, KeyBuiltBefore, replayed(a)); err != nil {
 			// Said and abandoned rather than retried: the catalogue asks again every time it
 			// starts, and half a graph delivered twice is no better than half delivered once.
 			s.log.Printf("replaying %s at %s failed, and the rest is abandoned: %v",
@@ -551,3 +567,49 @@ func (s *Server) sourceMoved(ctx context.Context, m Control) {
 	}
 	_ = m.Took()
 }
+
+// saysWhatItDid states what a machine now runs, or what it would not take, as a fact on the bus
+// (novox/hq ADR 0134).
+//
+// **The control plane speaks, as the holder of its seat.** A node's report is control traffic only
+// this process may read, so the chain from a merge to a machine went dark exactly where it touched
+// one: nothing said which version a machine runs, or that it refused to. The facts are second-hand
+// on purpose — one emitter, one ordering — and a machine that cannot reach the bus produces none, so
+// absence is not health.
+//
+// A failure to state a fact is logged and nothing else: the report is recorded, which is the part
+// that must not be lost, and the next change says the same thing again.
+func (s *Server) saysWhatItDid(ctx context.Context, report Report) {
+	if s.bus == nil {
+		return
+	}
+	event, body := KeyApplied, any(Applied{
+		Node: report.Node, Declared: report.Declared, Resources: len(report.Applied),
+	})
+	if report.Refused != "" || len(report.Failed) > 0 {
+		event, body = KeyRefused, Refused{
+			Node: report.Node, Declared: report.Declared,
+			Refused: report.Refused, Failed: report.Failed,
+		}
+	}
+	raw, err := json.Marshal(body)
+	if err != nil {
+		s.log.Printf("could not say what %s did: %v", report.Node, err)
+		return
+	}
+	if err := s.bus.PublishSeatEvent(ctx, MeshControllerSeat, event, raw); err != nil {
+		s.log.Printf("could not say that %s %s: %v", report.Node, event, err)
+	}
+}
+
+// replayed is one announcement as the control plane states it. The same body the build machine's
+// outcome carries, because what the catalogue does with it is the same.
+func replayed(a Announcement) []byte {
+	raw, err := json.Marshal(a)
+	if err != nil {
+		// A body that cannot be marshalled is a programming error, not a bus failure, and an empty
+		// one is refused by the reader rather than silently taken as an announcement of nothing.
+		return nil
+	}
+	return raw
+}

internal/link/stale_report_test.go

@@ -23,12 +23,12 @@ type sentAndHeard struct {
 	err   error
 }
 
-func (s *sentAndHeard) Heard(_ context.Context, r Report) error {
+func (s *sentAndHeard) Heard(_ context.Context, r Report) (bool, error) {
 	if s.err != nil {
-		return s.err
+		return false, s.err
 	}
 	s.heard = append(s.heard, r)
-	return nil
+	return true, nil
 }
 
 func (s *sentAndHeard) Outstanding(context.Context, string) (string, error) { return s.sent, nil }