diff --git a/cmd/mesh-controller/plan.go b/cmd/mesh-controller/plan.go
index b228ed6..46d269b 100644
--- a/cmd/mesh-controller/plan.go
+++ b/cmd/mesh-controller/plan.go
@@ -163,7 +163,14 @@ func planFor(ctx context.Context, open *stores, nodeName string) (catalogue.Reso
 			}
 			continue
 		}
-		secret, err := inv.SecretFor(ctx, n.Name, nodeName, n.For, n.From, n.Local)
+		var secret inventory.Secret
+		var err error
+		if n.SharedOwn != "" {
+			// The provider's one credential, sealed to this consumer too (novox/hq ADR 0158).
+			secret, err = inv.SharedSecretFor(ctx, n.Name, nodeName, n.For, n.From, providerModuleOf(resolved, open, ctx, n), n.Local, n.SharedOwn)
+		} else {
+			secret, err = inv.SecretFor(ctx, n.Name, nodeName, n.For, n.From, n.Local)
+		}
 		if err != nil {
 			// Said rather than skipped. A machine that resolves cleanly and receives no
 			// credential is one that will fail to authenticate at some later, less obvious
@@ -1338,3 +1345,23 @@ func foundationPortsFor(brokerPort int, modules []catalogue.Manifest) []int {
 	}
 	return nil
 }
+
+// providerModuleOf is which module answers a need on the providing node: the one in this node's
+// own set when the provider is here, else the one the catalogue says offers it.
+func providerModuleOf(resolved catalogue.Resolution, open *stores, ctx context.Context, n catalogue.Needed) string {
+	for _, m := range resolved.Modules {
+		if _, shared := m.SharedCredentialOf(n.Name); shared {
+			return m.Module
+		}
+	}
+	shelf, err := open.inventory.Catalogue(ctx)
+	if err != nil {
+		return ""
+	}
+	for name, m := range shelf {
+		if _, shared := m.SharedCredentialOf(n.Name); shared {
+			return name
+		}
+	}
+	return ""
+}
diff --git a/cmd/mesh-controller/secret.go b/cmd/mesh-controller/secret.go
index d7f3064..3f5c6de 100644
--- a/cmd/mesh-controller/secret.go
+++ b/cmd/mesh-controller/secret.go
@@ -387,10 +387,23 @@ func secretRotate(ctx context.Context, args []string) error {
 	}
 	fmt.Printf("rotated %q of %s on %s at %s, asked by %s; the value is sealed and not shown\n",
 		name, module, node, time.Now().UTC().Format(time.RFC3339), whoAsked())
-	fmt.Printf("sending %s, so %s starts again on the new value:\n", node, module)
-	if err := sendTo(ctx, open, []string{node}); err != nil {
+	// A shared credential (ADR 0158) has as many holders as the provision has consumers, and all
+	// of them are sent in one act, so no machine is left reading a value the provider no longer takes.
+	machines, err := open.inventory.SharedHolders(ctx, node, module, name)
+	if err != nil {
+		return err
+	}
+	if len(machines) == 0 {
+		machines = []string{node}
+	}
+	if len(machines) == 1 {
+		fmt.Printf("sending %s, so %s starts again on the new value:\n", node, module)
+	} else {
+		fmt.Printf("shared with every consumer; sending %s together:\n", strings.Join(machines, ", "))
+	}
+	if err := sendTo(ctx, open, machines); err != nil {
 		return fmt.Errorf("%w\n\nThe new value is sealed and not yet delivered; what runs keeps the old "+
-			"one until the machine next applies. Fix the cause and run `push %s`", err, node)
+			"one until the machines next apply. Fix the cause and run `push --behind`", err)
 	}
 	return nil
 }
diff --git a/internal/catalogue/manifest.go b/internal/catalogue/manifest.go
index a14c453..60e926f 100644
--- a/internal/catalogue/manifest.go
+++ b/internal/catalogue/manifest.go
@@ -127,6 +127,38 @@ type Offer struct {
 	Name string `json:"name"`
 	// Scope defaults to the node, which is where most things must be to be usable.
 	Scope string `json:"scope,omitempty"`
+	// Credential, when set, says this provision's credential is one of the provider's own secrets,
+	// shared by every consumer (novox/hq ADR 0158): software that holds one password or one key
+	// cannot give each consumer a login of its own. The named secret must say how it is taken.
+	Credential *OfferCredential `json:"credential,omitempty"`
+}
+
+// OfferCredential names which of the provider's own secrets a provision's consumers receive.
+type OfferCredential struct {
+	Own string `json:"own"`
+}
+
+// SharedCredentialOf is the own secret an offer of this module names as the provision's credential,
+// and whether it names one.
+func (m Manifest) SharedCredentialOf(provision string) (string, bool) {
+	for _, o := range m.Provides {
+		if o.Name == provision && o.Credential != nil && o.Credential.Own != "" {
+			return o.Credential.Own, true
+		}
+	}
+	return "", false
+}
+
+// ProvisionsSharing is every provision of this module whose credential is the named own secret.
+func (m Manifest) ProvisionsSharing(own string) []string {
+	var out []string
+	for _, o := range m.Provides {
+		if o.Credential != nil && o.Credential.Own == own {
+			out = append(out, o.Name)
+		}
+	}
+	sort.Strings(out)
+	return out
 }
 
 // At is this offer's scope, with the default applied.
@@ -145,26 +177,30 @@ func (o *Offer) UnmarshalJSON(raw []byte) error {
 		return nil
 	}
 	var full struct {
-		Name  string `json:"name"`
-		Scope string `json:"scope,omitempty"`
+		Name       string           `json:"name"`
+		Scope      string           `json:"scope,omitempty"`
+		Credential *OfferCredential `json:"credential,omitempty"`
 	}
-	if err := json.Unmarshal(raw, &full); err != nil {
-		return fmt.Errorf("a provided name is either a string or {name, scope}: %w", err)
+	dec := json.NewDecoder(bytes.NewReader(raw))
+	dec.DisallowUnknownFields()
+	if err := dec.Decode(&full); err != nil {
+		return fmt.Errorf("a provided name is either a string or {name, scope, credential}: %w", err)
 	}
-	o.Name, o.Scope = full.Name, full.Scope
+	o.Name, o.Scope, o.Credential = full.Name, full.Scope, full.Credential
 	return nil
 }
 
 // MarshalJSON writes back the short form when there is nothing else to say, so a manifest that
 // went through the mesh comes out looking like the one that went in.
 func (o Offer) MarshalJSON() ([]byte, error) {
-	if o.Scope == "" {
+	if o.Scope == "" && o.Credential == nil {
 		return json.Marshal(o.Name)
 	}
 	return json.Marshal(struct {
-		Name  string `json:"name"`
-		Scope string `json:"scope"`
-	}{o.Name, o.Scope})
+		Name       string           `json:"name"`
+		Scope      string           `json:"scope,omitempty"`
+		Credential *OfferCredential `json:"credential,omitempty"`
+	}{o.Name, o.Scope, o.Credential})
 }
 
 // Manifest is everything a module says about itself.
@@ -1142,6 +1178,23 @@ func ParseManifest(raw []byte) (Manifest, error) {
 		if !name.MatchString(p) {
 			problems = append(problems, fmt.Sprintf("%q is not a usable name to provide", p))
 		}
+		if offer.Credential != nil {
+			own, declared := m.OwnSecrets[offer.Credential.Own]
+			switch {
+			case offer.Credential.Own == "":
+				problems = append(problems, fmt.Sprintf(
+					"%s provides %q with a credential that names no own secret", m.Module, p))
+			case !declared:
+				problems = append(problems, fmt.Sprintf(
+					"%s provides %q with its own secret %q as the credential, and declares no such secret",
+					m.Module, p, offer.Credential.Own))
+			case own.Taken == "":
+				problems = append(problems, fmt.Sprintf(
+					"%s provides %q with its own secret %q as the credential every consumer receives, so "+
+						"the secret must say how the module takes it: \"taken\": \"at-start\" or \"applied\" (ADR 0158)",
+					m.Module, p, offer.Credential.Own))
+			}
+		}
 		if instead, generic := engineGeneric[p]; generic {
 			// A consumer is written against an engine, not a role (novox/hq ADR 0027). Providing
 			// the role means a requirement for it matches any engine, resolves as satisfied, and
diff --git a/internal/catalogue/resolve.go b/internal/catalogue/resolve.go
index 6bda01f..db82d16 100644
--- a/internal/catalogue/resolve.go
+++ b/internal/catalogue/resolve.go
@@ -179,6 +179,10 @@ type Needed struct {
 	// for one requirement (ADR 0094); empty for the ordinary one. Part of what identifies the pair
 	// credential, so two secrets from one provider to one module are two secrets.
 	Local string
+	// SharedOwn is set when the provision's credential is one of the provider's own secrets, shared
+	// by every consumer (novox/hq ADR 0158): the name of that secret in the provider's definition.
+	// The plan mints the pair's copy from the provider's value rather than a value of its own.
+	SharedOwn string
 	// Manager is set when this holder is a refreshable-grant licence's MANAGER, delivered the refresh
 	// token rather than an access token (novox/hq ADR 0050). It changes one thing downstream: an empty
 	// Sealed is tolerated — the manager has not adopted a refresh token yet, which is a real waiting
@@ -322,7 +326,8 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 				}
 				needs = append(needs, Needed{
 					Name: want, From: node.Name, At: at,
-					Serves: servedHere(catalogue, chosen, want), For: because[want]})
+					Serves: servedHere(catalogue, chosen, want), For: because[want],
+					SharedOwn: sharedHere(catalogue, chosen, want)})
 			} else if served := servedHere(catalogue, chosen, want); len(served) > 0 {
 				// Answered here with no credential to mint, but the provider serves facts the
 				// consumer cannot guess — a port, a model name — and so still needs a binding.
@@ -369,8 +374,12 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 						node.Name, want, p.Node, meshNetwork))
 					return
 				}
+				shared := ""
+				if pm, known := catalogue[p.Module]; known {
+					shared, _ = pm.SharedCredentialOf(want)
+				}
 				needs = append(needs, Needed{Name: want, From: p.Node, At: p.At,
-					Serves: p.Serves, For: because[want]})
+					Serves: p.Serves, For: because[want], SharedOwn: shared})
 			}
 			switch {
 			case world.Unchecked:
@@ -588,6 +597,20 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 // need that is never created is a binding the consumer never gets. It is right about that from the
 // manifest alone, which is why walking the catalogue mid-resolution is enough here and is not
 // enough for the values.
+// sharedHere is the own secret the provider of a provision on this same machine names as its
+// credential (ADR 0158), or "" when the provider gives each consumer its own.
+func sharedHere(catalogue map[string]Manifest, chosen map[string]bool, want string) string {
+	for name, m := range catalogue {
+		if !chosen[name] {
+			continue
+		}
+		if own, shared := m.SharedCredentialOf(want); shared {
+			return own
+		}
+	}
+	return ""
+}
+
 func servedHere(catalogue map[string]Manifest, chosen map[string]bool, want string) map[string]any {
 	for name, m := range catalogue {
 		if !chosen[name] {
diff --git a/internal/catalogue/shared_credential_test.go b/internal/catalogue/shared_credential_test.go
new file mode 100644
index 0000000..1965fd9
--- /dev/null
+++ b/internal/catalogue/shared_credential_test.go
@@ -0,0 +1,79 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+// A provider with one credential shares it (novox/hq ADR 0158): the offer names the own secret, the
+// secret says how it is taken, and a consumer's need carries the name so the plan mints its copy
+// from the provider's value.
+func TestAnOfferMayNameAnOwnSecretAsItsCredential(t *testing.T) {
+	m, err := ParseManifest([]byte(`{"module":"downloader","version":"1",
+		"own-secrets":{"password":{"path":"/var/lib/mesh/downloader/password","taken":"at-start"}},
+		"provides":[{"name":"downloader-api","credential":{"own":"password"}}],
+		"serves":{"downloader-api":{"port":8080,"username":"admin"}}}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if own, shared := m.SharedCredentialOf("downloader-api"); !shared || own != "password" {
+		t.Fatalf("the offer's credential was not read: %v %v", own, shared)
+	}
+	if got := m.ProvisionsSharing("password"); len(got) != 1 || got[0] != "downloader-api" {
+		t.Fatalf("the provisions sharing the secret: %v", got)
+	}
+
+	for want, raw := range map[string]string{
+		"declares no such secret": `{"module":"d","version":"1","provides":[{"name":"d-api","credential":{"own":"password"}}]}`,
+		"must say how the module takes it": `{"module":"d","version":"1","own-secrets":{"password":"/p"},
+			"provides":[{"name":"d-api","credential":{"own":"password"}}]}`,
+		"names no own secret": `{"module":"d","version":"1","provides":[{"name":"d-api","credential":{"own":""}}]}`,
+	} {
+		if _, err := ParseManifest([]byte(raw)); err == nil || !strings.Contains(err.Error(), want) {
+			t.Errorf("expected a refusal saying %q, got %v", want, err)
+		}
+	}
+}
+
+func sharingShelf() map[string]Manifest {
+	return shelf(
+		Manifest{Module: "downloader", Version: "1",
+			Provides:   []Offer{{Name: "downloader-api", Scope: ScopeMesh, Credential: &OfferCredential{Own: "password"}}},
+			OwnSecrets: OwnSecrets{"password": {Path: "/var/lib/mesh/downloader/password", Taken: TakenAtStart}},
+			Serves:     map[string]map[string]any{"downloader-api": {"port": 8080, "username": "admin"}}},
+		Manifest{Module: "manager", Version: "1", Requires: []string{"downloader-api"}},
+	)
+}
+
+func TestAConsumersNeedCarriesTheSharedSecretsName(t *testing.T) {
+	// On the same machine.
+	together, err := Resolve(sharingShelf(), []string{"downloader", "manager"}, workstation(), World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	found := false
+	for _, n := range together.Needs {
+		if n.Name == "downloader-api" && n.For == "manager" {
+			found = true
+			if n.SharedOwn != "password" {
+				t.Fatalf("the need on one machine does not name the shared secret: %+v", n)
+			}
+		}
+	}
+	if !found {
+		t.Fatalf("the manager's need was not resolved: %+v", together.Needs)
+	}
+	// Across machines, the provider known by its module.
+	apart, err := Resolve(sharingShelf(), []string{"manager"}, onBoth("example.tld"), World{
+		Offered: map[string][]Provider{"downloader-api": {{Node: "home-server", At: "home-server.internal",
+			Module: "downloader", Serves: map[string]any{"port": 8080}}}},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, n := range apart.Needs {
+		if n.Name == "downloader-api" && n.SharedOwn != "password" {
+			t.Fatalf("the need across machines does not name the shared secret: %+v", n)
+		}
+	}
+}
diff --git a/internal/inventory/migrations/0049-a-shared-credential-is-one-value-sealed-many-times.sql b/internal/inventory/migrations/0049-a-shared-credential-is-one-value-sealed-many-times.sql
new file mode 100644
index 0000000..c0a5cac
--- /dev/null
+++ b/internal/inventory/migrations/0049-a-shared-credential-is-one-value-sealed-many-times.sql
@@ -0,0 +1,8 @@
+-- A provider with one credential shares it with every consumer (novox/hq ADR 0158).
+--
+-- The provider's own secret and every consumer's pair row then carry one value, sealed once per
+-- holder. The mesh keeps no plaintext, so it cannot tell by reading that they agree; it stamps the
+-- act that made them instead. A pair row whose stamp is the own secret's was sealed from the same
+-- value; one whose stamp differs, or is missing, is remade for every holder at once.
+alter table module_secret add column generation text;
+alter table secret add column generation text;
diff --git a/internal/inventory/secrets.go b/internal/inventory/secrets.go
index 56834df..e30f380 100644
--- a/internal/inventory/secrets.go
+++ b/internal/inventory/secrets.go
@@ -592,6 +592,10 @@ func (i *Inventory) RotateModuleSecret(ctx context.Context, node, module, name s
 				"%s %s %s` with the new value",
 			module, node, name, node, module, name)}
 	}
+	if len(m.ProvisionsSharing(name)) > 0 {
+		// Shared with every consumer of those provisions (ADR 0158): one new value, sealed to all.
+		return i.remakeShared(ctx, record.ID, key, module, name, "", nil, "", "", "")
+	}
 	operator, err := i.OperatorKey(ctx)
 	if err != nil {
 		return err
@@ -608,3 +612,211 @@ func (i *Inventory) RotateModuleSecret(ctx context.Context, node, module, name s
 		record.ID, module, name, made.ForConsumer, key, forOperator, operatorKey)
 	return err
 }
+
+// SharedSecretFor is a consumer's copy of a provider's one credential (novox/hq ADR 0158): the
+// provider's own secret, sealed to this consumer as a pair credential would be.
+//
+// **One value, many seals, made in one act.** The mesh keeps no plaintext, so a value cannot be
+// sealed to a consumer that binds later; when a consumer's copy is missing or was made in a
+// different act than the provider's own secret, a fresh value is made and sealed to the provider,
+// to every consumer that holds the provision from this provider, to this consumer and to the
+// operator — one generation, stamped on every row. Every holding machine must then be sent, which
+// the plan's caller does by sending the node it was composing and `secret rotate` does for all.
+//
+// An accepted value is sealed to the consumers of the moment it was accepted and never remade: a
+// consumer that binds later is refused with the way out, as ADR 0113 says.
+func (i *Inventory) SharedSecretFor(ctx context.Context, provision, consumer, consumerModule,
+	provider, providerModule, local, own string) (Secret, error) {
+	consumerKey, err := i.SealingKeyOf(ctx, consumer)
+	if err != nil {
+		return Secret{}, err
+	}
+	consumerNode, err := i.NodeByName(ctx, consumer)
+	if err != nil {
+		return Secret{}, err
+	}
+	providerNode, err := i.NodeByName(ctx, provider)
+	if err != nil {
+		return Secret{}, err
+	}
+	providerKey, err := i.SealingKeyOf(ctx, provider)
+	if err != nil {
+		return Secret{}, err
+	}
+	if consumerKey == "" || providerKey == "" {
+		return Secret{}, fmt.Errorf("%s and %s both need a sealing key before %s can be shared", consumer, provider, provision)
+	}
+
+	var ownGeneration, ownOrigin, ownKey *string
+	err = i.store.Pool().QueryRow(ctx,
+		`select generation, origin, node_key from module_secret where node = $1 and module = $2 and name = $3`,
+		providerNode.ID, providerModule, own).Scan(&ownGeneration, &ownOrigin, &ownKey)
+	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
+		return Secret{}, err
+	}
+	var held Secret
+	var pairGeneration *string
+	err = i.store.Pool().QueryRow(ctx,
+		`select for_consumer, for_provider, consumer_key, provider_key, origin, generation from secret
+		 where name = $1 and consumer = $2 and consumer_module = $3 and provider = $4 and local = $5`,
+		provision, consumerNode.ID, consumerModule, providerNode.ID, local).
+		Scan(&held.ForConsumer, &held.ForProvider, &held.ConsumerKey, &held.ProviderKey, &held.Origin, &pairGeneration)
+	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
+		return Secret{}, err
+	}
+	current := ownGeneration != nil && pairGeneration != nil && *ownGeneration == *pairGeneration &&
+		held.ConsumerKey == consumerKey && held.ProviderKey == providerKey && ownKey != nil && *ownKey == providerKey
+	if current {
+		held.Name, held.Consumer, held.Provider = provision, consumer, provider
+		held.ConsumerModule, held.Local = consumerModule, local
+		return held, nil
+	}
+	if ownOrigin != nil && *ownOrigin == OriginAccepted {
+		return Secret{}, fmt.Errorf(
+			"%s on %s needs %s from %s, whose credential is %s's own secret %q — a value given to the "+
+				"mesh, which cannot seal it to a consumer that binds later (ADR 0158): `secret accept %s %s %s` "+
+				"again, which seals it to every current consumer",
+			consumerModule, consumer, provision, provider, providerModule, own, provider, providerModule, own)
+	}
+	if err := i.remakeShared(ctx, providerNode.ID, providerKey, providerModule, own, provision, consumerNode.ID, consumerKey, consumerModule, local); err != nil {
+		return Secret{}, err
+	}
+	return i.SharedSecretFor(ctx, provision, consumer, consumerModule, provider, providerModule, local, own)
+}
+
+// remakeShared makes one fresh value and seals it to the provider's own secret, to every pair row
+// of the provisions sharing it, to the one consumer being added (when there is one), and to the
+// operator, all under one generation.
+func (i *Inventory) remakeShared(ctx context.Context, providerID any, providerKey, providerModule, own,
+	provision string, addConsumerID any, addConsumerKey, addConsumerModule, addLocal string) error {
+	m, err := i.declared(ctx, providerModule)
+	if err != nil {
+		return err
+	}
+	provisions := m.ProvisionsSharing(own)
+	if len(provisions) == 0 {
+		return fmt.Errorf("%s names no provision whose credential is its own secret %q", providerModule, own)
+	}
+	operator, err := i.OperatorKey(ctx)
+	if err != nil {
+		return err
+	}
+	value := secrets.Fresh()
+	generation := secrets.Stamp()
+	ownSealed, err := secrets.Seal(providerKey, []byte(value))
+	if err != nil {
+		return err
+	}
+	forOperator, operatorKey := "", ""
+	if operator != "" {
+		if forOperator, err = secrets.Seal(operator, []byte(value)); err != nil {
+			return err
+		}
+		operatorKey = operator
+	}
+	tx, err := i.store.Pool().Begin(ctx)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = tx.Rollback(ctx) }()
+	if _, err := tx.Exec(ctx,
+		`insert into module_secret (node, module, name, sealed, node_key, origin, operator_sealed, operator_key, generation)
+		 values ($1, $2, $3, $4, $5, 'made', nullif($6,''), nullif($7,''), $8)
+		 on conflict (node, module, name) do update set
+		   sealed = excluded.sealed, node_key = excluded.node_key, origin = 'made', made_at = now(),
+		   operator_sealed = excluded.operator_sealed, operator_key = excluded.operator_key,
+		   generation = excluded.generation`,
+		providerID, providerModule, own, ownSealed, providerKey, forOperator, operatorKey, generation); err != nil {
+		return err
+	}
+	// Every consumer that already holds one of the sharing provisions from this provider.
+	rows, err := tx.Query(ctx,
+		`select s.consumer, s.consumer_module, s.local, s.name, n.sealing_key
+		   from secret s join node n on n.id = s.consumer
+		  where s.provider = $1 and s.name = any($2)`, providerID, provisions)
+	if err != nil {
+		return err
+	}
+	type holder struct {
+		consumer                         any
+		consumerModule, local, name, key string
+	}
+	var holders []holder
+	for rows.Next() {
+		var h holder
+		var key *string
+		if err := rows.Scan(&h.consumer, &h.consumerModule, &h.local, &h.name, &key); err != nil {
+			rows.Close()
+			return err
+		}
+		if key != nil {
+			h.key = *key
+		}
+		holders = append(holders, h)
+	}
+	rows.Close()
+	if addConsumerID != nil {
+		holders = append(holders, holder{consumer: addConsumerID, consumerModule: addConsumerModule,
+			local: addLocal, name: provision, key: addConsumerKey})
+	}
+	for _, h := range holders {
+		if h.key == "" {
+			continue // a consumer whose key is gone cannot be sealed to; it is remade when it reports one
+		}
+		sealed, err := secrets.Accept(value, h.key, providerKey)
+		if err != nil {
+			return err
+		}
+		if _, err := tx.Exec(ctx,
+			`insert into secret (name, consumer, consumer_module, provider, for_consumer, for_provider,
+			                     consumer_key, provider_key, origin, local, generation)
+			 values ($1, $2, $3, $4, $5, $6, $7, $8, 'made', $9, $10)
+			 on conflict (name, local, consumer, consumer_module, provider) do update set
+			   for_consumer = excluded.for_consumer, for_provider = excluded.for_provider,
+			   consumer_key = excluded.consumer_key, provider_key = excluded.provider_key,
+			   origin = 'made', generation = excluded.generation`,
+			h.name, h.consumer, h.consumerModule, providerID, sealed.ForConsumer, sealed.ForProvider,
+			h.key, providerKey, h.local, generation); err != nil {
+			return err
+		}
+	}
+	return tx.Commit(ctx)
+}
+
+// SharedHolders is every machine holding a copy of a provider's shared credential: the provider's
+// and every consumer's, for the send that follows a rotation.
+func (i *Inventory) SharedHolders(ctx context.Context, provider, providerModule, own string) ([]string, error) {
+	m, err := i.declared(ctx, providerModule)
+	if err != nil {
+		return nil, err
+	}
+	provisions := m.ProvisionsSharing(own)
+	if len(provisions) == 0 {
+		return nil, nil
+	}
+	providerNode, err := i.NodeByName(ctx, provider)
+	if err != nil {
+		return nil, err
+	}
+	rows, err := i.store.Pool().Query(ctx,
+		`select distinct n.name from secret s join node n on n.id = s.consumer
+		  where s.provider = $1 and s.name = any($2)`, providerNode.ID, provisions)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	seen := map[string]bool{provider: true}
+	out := []string{provider}
+	for rows.Next() {
+		var name string
+		if err := rows.Scan(&name); err != nil {
+			return nil, err
+		}
+		if !seen[name] {
+			seen[name] = true
+			out = append(out, name)
+		}
+	}
+	sort.Strings(out)
+	return out, nil
+}
diff --git a/internal/inventory/secrets_test.go b/internal/inventory/secrets_test.go
index 0eb967f..d29b91c 100644
--- a/internal/inventory/secrets_test.go
+++ b/internal/inventory/secrets_test.go
@@ -8,6 +8,7 @@ import (
 	"errors"
 	"github.com/novox/mesh-controller/internal/catalogue"
 	"github.com/novox/mesh-controller/internal/secrets"
+	"reflect"
 	"strings"
 	"testing"
 
@@ -843,3 +844,93 @@ func TestAnOwnSecretRotatesOnlyWhenTheModuleReadsItAtStart(t *testing.T) {
 		t.Fatalf("an undeclared secret: %v", err)
 	}
 }
+
+// A provider's one credential is one value sealed to every holder, remade for all at once when a
+// consumer binds or a rotation is asked (novox/hq ADR 0158).
+func TestASharedCredentialIsOneValueSealedToEveryHolder(t *testing.T) {
+	inv, ctx := twoNodesWithKeys(t)
+	provider := catalogue.Manifest{Module: "downloader", Version: "1",
+		Provides:   []catalogue.Offer{{Name: "downloader-api", Scope: catalogue.ScopeMesh, Credential: &catalogue.OfferCredential{Own: "password"}}},
+		OwnSecrets: catalogue.OwnSecrets{"password": {Path: "/var/lib/mesh/downloader/password", Taken: catalogue.TakenAtStart}}}
+	if err := inv.RegisterModule(ctx, provider, Source{}); err != nil {
+		t.Fatal(err)
+	}
+	for _, m := range []string{"manager", "indexer"} {
+		if err := inv.RegisterModule(ctx, catalogue.Manifest{Module: m, Version: "1", Requires: []string{"downloader-api"}}, Source{}); err != nil {
+			t.Fatal(err)
+		}
+	}
+	generationOf := func() string {
+		var g *string
+		node, _ := inv.NodeByName(ctx, "provider")
+		if err := inv.store.Pool().QueryRow(ctx, `select generation from module_secret where node = $1 and module = 'downloader' and name = 'password'`, node.ID).Scan(&g); err != nil {
+			t.Fatal(err)
+		}
+		if g == nil {
+			t.Fatal("the provider's own secret carries no generation")
+		}
+		return *g
+	}
+	pairGeneration := func(module string) string {
+		var g *string
+		cn, _ := inv.NodeByName(ctx, "consumer")
+		pn, _ := inv.NodeByName(ctx, "provider")
+		if err := inv.store.Pool().QueryRow(ctx, `select generation from secret where name = 'downloader-api' and consumer = $1 and consumer_module = $2 and provider = $3`, cn.ID, module, pn.ID).Scan(&g); err != nil {
+			t.Fatal(err)
+		}
+		if g == nil {
+			return ""
+		}
+		return *g
+	}
+
+	first, err := inv.SharedSecretFor(ctx, "downloader-api", "consumer", "manager", "provider", "downloader", "", "password")
+	if err != nil {
+		t.Fatal(err)
+	}
+	g1 := generationOf()
+	if pairGeneration("manager") != g1 {
+		t.Fatal("the consumer's copy was not sealed in the same act as the provider's own secret")
+	}
+	again, err := inv.SharedSecretFor(ctx, "downloader-api", "consumer", "manager", "provider", "downloader", "", "password")
+	if err != nil || again.ForConsumer != first.ForConsumer {
+		t.Fatalf("asking twice remade the value: %v", err)
+	}
+
+	// A second consumer binding remakes the value for everyone, in one generation.
+	if _, err := inv.SharedSecretFor(ctx, "downloader-api", "consumer", "indexer", "provider", "downloader", "", "password"); err != nil {
+		t.Fatal(err)
+	}
+	g2 := generationOf()
+	if g2 == g1 {
+		t.Fatal("a new consumer did not remake the shared value")
+	}
+	if pairGeneration("manager") != g2 || pairGeneration("indexer") != g2 {
+		t.Fatalf("not every holder was sealed in the new act: %s %s %s", g2, pairGeneration("manager"), pairGeneration("indexer"))
+	}
+	holders, err := inv.SharedHolders(ctx, "provider", "downloader", "password")
+	if err != nil || !reflect.DeepEqual(holders, []string{"consumer", "provider"}) {
+		t.Fatalf("the holders: %v %v", holders, err)
+	}
+
+	// Rotation remakes every copy.
+	if err := inv.RotateModuleSecret(ctx, "provider", "downloader", "password"); err != nil {
+		t.Fatal(err)
+	}
+	g3 := generationOf()
+	if g3 == g2 || pairGeneration("manager") != g3 || pairGeneration("indexer") != g3 {
+		t.Fatal("rotation did not remake every holder's copy")
+	}
+
+	// An accepted value: sealed to the consumers of the moment, and a later consumer is refused.
+	if err := inv.AcceptSecretForModule(ctx, "provider", "downloader", "password", "the-real-one"); err != nil {
+		t.Fatal(err)
+	}
+	if err := inv.RegisterModule(ctx, catalogue.Manifest{Module: "late", Version: "1", Requires: []string{"downloader-api"}}, Source{}); err != nil {
+		t.Fatal(err)
+	}
+	_, err = inv.SharedSecretFor(ctx, "downloader-api", "consumer", "late", "provider", "downloader", "", "password")
+	if err == nil || !strings.Contains(err.Error(), "given to the mesh") {
+		t.Fatalf("a consumer binding after an acceptance must be refused with the way out: %v", err)
+	}
+}
diff --git a/internal/secrets/seal.go b/internal/secrets/seal.go
index a26f3f5..ecdf5e7 100644
--- a/internal/secrets/seal.go
+++ b/internal/secrets/seal.go
@@ -45,6 +45,26 @@ type Sealed struct {
 	ProviderKey string
 }
 
+// Fresh is a new secret value, the shape Make seals: for the one caller that must seal one value
+// to many holders at once (novox/hq ADR 0158) and discards it the same way.
+func Fresh() string {
+	value := make([]byte, 30)
+	if _, err := rand.Read(value); err != nil {
+		panic("the system's random source failed: " + err.Error())
+	}
+	return base64.RawURLEncoding.EncodeToString(value)
+}
+
+// Stamp is a random mark for one act of sealing a value to several holders: rows carrying the same
+// stamp were sealed from the same value, which the mesh cannot otherwise tell, holding no plaintext.
+func Stamp() string {
+	mark := make([]byte, 16)
+	if _, err := rand.Read(mark); err != nil {
+		panic("the system's random source failed: " + err.Error())
+	}
+	return hex.EncodeToString(mark)
+}
+
 // Make generates a secret and seals it to both ends, keeping no readable copy.
 //
 // The plaintext exists for the length of this call. Rotation is therefore generating a new one