diff --git a/cmd/mesh-controller/build.go b/cmd/mesh-controller/build.go
index 26684d6..5ec6bca 100644
--- a/cmd/mesh-controller/build.go
+++ b/cmd/mesh-controller/build.go
@@ -558,6 +558,10 @@ func takeIn(ctx context.Context, inv *inventory.Inventory, result link.BuildResu
 		}
 		return manifest, kept, err
 	}
+	// The keep set just moved, and new bytes just landed (novox/hq ADR 0189). Asked here rather
+	// than on a timer of its own: this is the only moment either is true. Never fatal — the build
+	// worked and the module is registered.
+	collect(ctx, inv)
 	return manifest, kept, nil
 }
 
diff --git a/cmd/mesh-controller/collect.go b/cmd/mesh-controller/collect.go
new file mode 100644
index 0000000..5464800
--- /dev/null
+++ b/cmd/mesh-controller/collect.go
@@ -0,0 +1,108 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/novox/mesh-controller/internal/artifacts"
+	"github.com/novox/mesh-controller/internal/inventory"
+)
+
+// Letting the artifact store go of what the mesh no longer keeps (novox/hq ADR 0189, issue 108).
+//
+// **Run where the records change.** A build is the moment new bytes landed in the store and the
+// moment the keep set moved, so it is the moment to say what may go — and it needs no timer of
+// its own. Reclaiming the bytes is the store's own nightly step; this only decides.
+//
+// Never fatal to a build. The build succeeded, the module is registered, and a store that could
+// not be reached is a thing to say rather than a reason to undo any of that. The next build asks
+// again, and the references it could not collect are still uncollected, so nothing is lost by
+// having failed.
+
+// collect asks the store to let go of everything the mesh made and no longer keeps, and records
+// what it let go of. Says what it did and what it could not; returns nothing, because nothing
+// upstream should branch on it.
+func collect(ctx context.Context, inv *inventory.Inventory) {
+	references, err := inv.ToCollect(ctx)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "could not work out what the artifact store may let go of: %v\n", err)
+		return
+	}
+	if len(references) == 0 {
+		return
+	}
+	shelf, err := inv.Catalogue(ctx)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "could not read the catalogue to find the artifact store: %v\n", err)
+		return
+	}
+	// As the mesh reaches it from the network. Empty means the store is not on the network — on a
+	// mesh being raised it is not yet, and there the store holds one build of anything and has
+	// nothing to collect.
+	address, err := artifactStoreAddress(ctx, inv, shelf, "")
+	if err != nil || address == "" {
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "could not find the artifact store to collect from: %v\n", err)
+		}
+		return
+	}
+
+	// **Bounded, because this runs inside somebody's build.** The first sweep of a mesh that has
+	// never collected has the whole history to get through, and a person waiting on `build` should
+	// not pay for it. Two bounds, and what is left over is simply offered again next time —
+	// builds are frequent, and the point is that the store stops growing, not that it empties
+	// tonight.
+	within, stop := context.WithTimeout(ctx, sweepBudget)
+	defer stop()
+	store := artifacts.Store{Address: address}
+
+	var done []string
+	var left int
+	for i, reference := range references {
+		if i >= mostPerSweep || within.Err() != nil {
+			left = len(references) - i
+			break
+		}
+		err := store.LetGo(within, reference)
+		if err == nil || errors.Is(err, artifacts.Gone) {
+			// Gone is the outcome wanted, already true. Recorded so the next sweep does not ask
+			// again for ever.
+			done = append(done, reference)
+			continue
+		}
+		// **Stopped at the first refusal, not pushed through.** A store that refuses one refuses
+		// all of them — deletion disabled, the store down, the network gone — so going on would
+		// be a hundred identical failures and a hundred identical log lines in front of whoever
+		// was building something.
+		fmt.Fprintf(os.Stderr, "the artifact store kept %s, so nothing more was asked of it: %v\n",
+			reference, err)
+		left = len(references) - i
+		break
+	}
+
+	if len(done) > 0 {
+		// Recorded outside `within`: the deletions happened, and losing the record of them because
+		// the sweep ran out of budget would mean asking about them again for ever.
+		if err := inv.MarkCollected(ctx, done); err != nil {
+			fmt.Fprintf(os.Stderr, "the store let go of %d artifact(s) and the record of it did not keep: %v\n",
+				len(done), err)
+			return
+		}
+		fmt.Fprintf(os.Stderr, "the artifact store let go of %d artifact(s) the mesh no longer keeps\n",
+			len(done))
+	}
+	if left > 0 {
+		fmt.Fprintf(os.Stderr, "%d more to collect; the next build asks again\n", left)
+	}
+}
+
+// mostPerSweep is how many artifacts one sweep will ask about. Enough that a mesh building
+// several times a day converges within days of this landing; small enough that no single build
+// waits on the whole backlog.
+const mostPerSweep = 200
+
+// sweepBudget is the longest a sweep will keep a build waiting.
+const sweepBudget = 60 * time.Second
diff --git a/internal/artifacts/store.go b/internal/artifacts/store.go
new file mode 100644
index 0000000..02b79d8
--- /dev/null
+++ b/internal/artifacts/store.go
@@ -0,0 +1,99 @@
+// Package artifacts speaks to the mesh's artifact store over its own door.
+//
+// Only what the mesh needs that nothing else does: letting go of something it put there
+// (novox/hq ADR 0189, issue 108). Pushing is the builder's, through the container runtime; reading
+// is every machine's, through its runtime. This is the one operation that belongs to the thing
+// holding the records, because it is the only one that is a decision rather than a transfer.
+package artifacts
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// Store is the artifact store at an address, as this machine reaches it.
+type Store struct {
+	// Address is `host:port` — the store as the caller reaches it now, composed and never
+	// recorded (novox/hq 04-ISSUES/102).
+	Address string
+	// HTTP is the client used; nil is a client with a modest timeout.
+	HTTP *http.Client
+}
+
+// Gone is the answer when the store does not hold it: the outcome wanted, already true.
+var Gone = fmt.Errorf("the store does not hold it")
+
+// LetGo asks the store to drop one artifact the mesh recorded making.
+//
+// Takes a reference as the mesh records it — `artifact-store://<module>/<artifact>@sha256:…` for
+// an image, `…/blobs/sha256:…` for an archive — because that is the identity every record uses,
+// and composes the address here at the moment of use.
+//
+// Returns Gone when the store answers that it does not have it. That is not a failure: the sweep
+// wants the artifact absent, and it is. It is distinguished from success only so a caller can say
+// which of the two happened.
+func (s Store) LetGo(ctx context.Context, reference string) error {
+	path, kept := catalogue.InArtifactStore(reference)
+	if !kept {
+		// Nothing the mesh put in its own store. Refused rather than attempted: composing a
+		// delete for a reference of unknown shape is how a sweep reaches something that is not
+		// the mesh's.
+		return fmt.Errorf("%s is not a reference into the mesh's artifact store", reference)
+	}
+	if s.Address == "" {
+		return fmt.Errorf("this mesh has no artifact store on its network to ask about %s", reference)
+	}
+	repository, kind, digest, err := split(path)
+	if err != nil {
+		return err
+	}
+	url := "http://" + s.Address + "/v2/" + repository + "/" + kind + "/" + digest
+
+	request, err := http.NewRequestWithContext(ctx, http.MethodDelete, url, nil)
+	if err != nil {
+		return err
+	}
+	client := s.HTTP
+	if client == nil {
+		client = &http.Client{Timeout: 30 * time.Second}
+	}
+	response, err := client.Do(request)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+	switch response.StatusCode {
+	case http.StatusAccepted, http.StatusOK, http.StatusNoContent:
+		return nil
+	case http.StatusNotFound:
+		return Gone
+	case http.StatusMethodNotAllowed:
+		// The registry was started without deletion enabled. Said plainly, because the remedy is
+		// a setting on the store's module and not anything about this artifact.
+		return fmt.Errorf(
+			"the artifact store refuses deletion: its server was started without it enabled "+
+				"(REGISTRY_STORAGE_DELETE_ENABLED), so nothing can be collected until the store "+
+				"module is applied again (novox/hq ADR 0189). Asking about %s", reference)
+	default:
+		return fmt.Errorf("the artifact store answered %s for %s", response.Status, reference)
+	}
+}
+
+// split reads a recorded path into the repository, which endpoint names the thing, and the digest.
+//
+// Two shapes, which are the two the mesh records: `<repository>@sha256:<hex>` is a manifest, and
+// `<repository>/blobs/sha256:<hex>` is a blob.
+func split(path string) (repository, kind, digest string, err error) {
+	if before, after, ok := strings.Cut(path, "@sha256:"); ok {
+		return before, "manifests", "sha256:" + after, nil
+	}
+	if before, after, ok := strings.Cut(path, "/blobs/sha256:"); ok {
+		return before, "blobs", "sha256:" + after, nil
+	}
+	return "", "", "", fmt.Errorf("%q names nothing the store holds by digest", path)
+}
diff --git a/internal/artifacts/store_test.go b/internal/artifacts/store_test.go
new file mode 100644
index 0000000..3b433c8
--- /dev/null
+++ b/internal/artifacts/store_test.go
@@ -0,0 +1,94 @@
+package artifacts
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// Asking the store to let go of what the mesh no longer keeps (novox/hq ADR 0189, issue 108).
+//
+// A fake store records what it was asked to delete, so what is asserted is the mesh's decision
+// and the shape of the request — not the registry's behaviour, which is the registry's to test.
+
+func fakeStore(t *testing.T, answer int) (Store, *[]string) {
+	t.Helper()
+	var asked []string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodDelete {
+			t.Errorf("the store was asked %s %s; collecting is a delete", r.Method, r.URL.Path)
+		}
+		asked = append(asked, r.URL.Path)
+		w.WriteHeader(answer)
+	}))
+	t.Cleanup(server.Close)
+	return Store{Address: strings.TrimPrefix(server.URL, "http://")}, &asked
+}
+
+func TestAnImageAndAnArchiveAreAskedForAtTheirOwnEndpoints(t *testing.T) {
+	// The two shapes the mesh records: a manifest by digest, and a blob by digest. They are
+	// different endpoints, and asking at the wrong one answers 404 — which this would then
+	// record as collected, leaving the bytes on disk for ever while the record says otherwise.
+	store, asked := fakeStore(t, http.StatusAccepted)
+	ctx := context.Background()
+
+	image := catalogue.ArtifactStoreScheme + "web/app@sha256:abc123"
+	archive := catalogue.ArtifactStoreScheme + "web/config/blobs/sha256:def456"
+	if err := store.LetGo(ctx, image); err != nil {
+		t.Fatal(err)
+	}
+	if err := store.LetGo(ctx, archive); err != nil {
+		t.Fatal(err)
+	}
+	want := []string{"/v2/web/app/manifests/sha256:abc123", "/v2/web/config/blobs/sha256:def456"}
+	if len(*asked) != 2 || (*asked)[0] != want[0] || (*asked)[1] != want[1] {
+		t.Fatalf("the store was asked %v; want %v", *asked, want)
+	}
+}
+
+func TestAStoreThatDoesNotHaveItAnswersGone(t *testing.T) {
+	// The outcome wanted, already true. Told apart from success only so the sweep can say which
+	// happened; both are recorded, because retrying for ever is the thing to avoid.
+	store, _ := fakeStore(t, http.StatusNotFound)
+	err := store.LetGo(context.Background(), catalogue.ArtifactStoreScheme+"web/app@sha256:abc123")
+	if !errors.Is(err, Gone) {
+		t.Fatalf("a store that does not hold it answered %v, want Gone", err)
+	}
+}
+
+func TestAStoreWithDeletionOffSaysSoAndNamesTheRemedy(t *testing.T) {
+	// The registry answers 405 when it was started without deletion enabled. The remedy is a
+	// setting on the store's module, and saying "405" would send somebody to the wrong place.
+	store, _ := fakeStore(t, http.StatusMethodNotAllowed)
+	err := store.LetGo(context.Background(), catalogue.ArtifactStoreScheme+"web/app@sha256:abc123")
+	if err == nil {
+		t.Fatal("a store that refuses deletion was read as success")
+	}
+	if !strings.Contains(err.Error(), "REGISTRY_STORAGE_DELETE_ENABLED") {
+		t.Fatalf("the refusal does not name the remedy: %v", err)
+	}
+}
+
+func TestAReferenceThatIsNotTheMeshsOwnIsNeverAsked(t *testing.T) {
+	// The whole safety of the sweep is that it names only what the mesh recorded putting there.
+	// A reference of another shape — a vendor's image, a package version — is refused rather
+	// than composed into a delete somewhere that is not the mesh's store.
+	store, asked := fakeStore(t, http.StatusAccepted)
+	for _, reference := range []string{
+		"docker.io/library/registry@sha256:abc123",
+		"registry@sha256:abc123",
+		"1.4.2",
+	} {
+		if err := store.LetGo(context.Background(), reference); err == nil {
+			t.Errorf("%s was asked about; it is not a reference into the mesh's store", reference)
+		}
+	}
+	if len(*asked) != 0 {
+		t.Fatalf("the store was asked about %v", *asked)
+	}
+}
diff --git a/internal/catalogue/bound_into_files.go b/internal/catalogue/bound_into_files.go
index cf4ef56..b9729f3 100644
--- a/internal/catalogue/bound_into_files.go
+++ b/internal/catalogue/bound_into_files.go
@@ -46,7 +46,7 @@ func boundUsed(content string) [][2]string {
 // Three facts the mesh states about any provision, plus whatever the provider said it serves. A
 // module may not reach a binding it does not have — the same boundary as a secret, for the same
 // reason.
-func knownFor(m Manifest, needs []Needed, node string) map[string]map[string]string {
+func knownFor(m Manifest, needs []Needed, node string) (map[string]map[string]string, error) {
 	out := map[string]map[string]string{}
 	for _, want := range m.Wants() {
 		for i := range needs {
@@ -54,12 +54,20 @@ func knownFor(m Manifest, needs []Needed, node string) map[string]map[string]str
 			if n.Name != want || n.For != m.Module {
 				continue
 			}
+			as := ConsumerIdentity(node, IdentitySource(m.Slug, m.Module))
 			values := map[string]string{
 				"at":   n.At,
 				"from": n.From,
-				"as":   ConsumerIdentity(node, IdentitySource(m.Slug, m.Module)),
+				"as":   as,
 			}
-			for key, value := range n.Serves {
+			// What the provider derives for this consumer rather than for all of them
+			// (novox/hq ADR 0201). Filled here, the one place a provision and the module
+			// requiring it are both in hand.
+			served, err := ServedTo(n.Serves, as)
+			if err != nil {
+				return nil, fmt.Errorf("%s requires %s: %w", m.Module, want, err)
+			}
+			for key, value := range served {
 				// The provider's own vocabulary. Rendered plainly: a port is 5432, not 5432.000000,
 				// which is what a float would write and what a connection string would refuse.
 				values[key] = plainly(value)
@@ -67,7 +75,7 @@ func knownFor(m Manifest, needs []Needed, node string) map[string]map[string]str
 			out[want] = values
 		}
 	}
-	return out
+	return out, nil
 }
 
 // withOwnNames adds a module's own composed names to what it may name from one binding:
diff --git a/internal/catalogue/consumer_into_serves.go b/internal/catalogue/consumer_into_serves.go
new file mode 100644
index 0000000..897411d
--- /dev/null
+++ b/internal/catalogue/consumer_into_serves.go
@@ -0,0 +1,311 @@
+package catalogue
+
+import (
+	"fmt"
+	"regexp"
+	"sort"
+	"strings"
+)
+
+// What a provider derives for one consumer, said once in the provider's definition and delivered
+// to both ends (novox/hq ADR 0201, issue 124).
+//
+// A `serves` block is otherwise literal: the same values for every consumer. Where the provider
+// *names the resource* — a bucket, a database, a vhost — the name is derived from who is asking,
+// and before this the mesh had no channel for it. The provider recomputed it in its own code and
+// every consumer transcribed it into its own definition by hand, which is a copy of somebody
+// else's rule kept in agreement by nobody. One of three transcriptions was wrong for months.
+//
+// **The mesh learns no protocol here; it spells its own name in an alphabet it already knows.**
+// The only fact a served value may name is the identity the mesh itself minted for the consumer,
+// in one of two alphabets: as it was minted, and as a DNS label. Everything a provider wants
+// around it — a prefix, a suffix, a separator — it writes around the placeholder, because a
+// served value is a string.
+
+// consumerFact is `${consumer:<fact>}` or `${consumer:<fact>:<alphabet>}`.
+var consumerFact = regexp.MustCompile(`\$\{consumer:([a-z][a-z0-9-]*)(?::([a-z][a-z0-9-]*))?\}`)
+
+// consumerFacts are what a served value may name about the consumer it is being derived for.
+// One entry, deliberately: the identity is the one thing about a consumer the mesh itself chose,
+// so it is the one thing the mesh can hand to a provider without either end guessing.
+var consumerFacts = []string{"as"}
+
+// consumerAlphabets are the ways the mesh will write that identity. `dns` is the mesh's own
+// identifier with its separator written `-` instead of `_` — the whole of the difference between
+// the alphabet the mesh mints in and the one buckets, vhosts and hostnames accept.
+var consumerAlphabets = []string{"dns"}
+
+// ServedTo fills a provider's served values for one consumer.
+//
+// `as` is the identity the mesh minted for that consumer — the same string it is told to present
+// as a login. Values with no placeholder are returned exactly as they were, and a block with no
+// placeholder at all is returned unchanged, so this costs nothing for the providers that derive
+// nothing.
+//
+// Only strings carry placeholders. A number, a boolean or a nested object is a value the provider
+// stated outright, and is left alone.
+func ServedTo(serves map[string]any, as string) (map[string]any, error) {
+	if len(serves) == 0 {
+		return serves, nil
+	}
+	var out map[string]any
+	for _, key := range sortedAnyKeys(serves) {
+		text, ok := serves[key].(string)
+		if !ok || !strings.Contains(text, "${consumer:") {
+			continue
+		}
+		filled, err := consumerInto(text, as)
+		if err != nil {
+			return nil, fmt.Errorf("the value served as %q: %w", key, err)
+		}
+		if out == nil {
+			// Copied only once something actually changes: the caller's map is the manifest's,
+			// and a provider that derives nothing must not have it rewritten underneath it.
+			out = make(map[string]any, len(serves))
+			for k, v := range serves {
+				out[k] = v
+			}
+		}
+		out[key] = filled
+	}
+	if out == nil {
+		return serves, nil
+	}
+	return out, nil
+}
+
+// consumerInto replaces every `${consumer:…}` in one value.
+//
+// **A fact or an alphabet the mesh does not have is refused, not left standing.** Written through,
+// the literal `${consumer:as}` would reach a configuration file and be read as a bucket name,
+// failing somewhere that names neither the module nor the mesh — the same reasoning `${bound:…}`
+// is refused by (boundInto).
+func consumerInto(value, as string) (string, error) {
+	var failed error
+	out := consumerFact.ReplaceAllStringFunc(value, func(match string) string {
+		parts := consumerFact.FindStringSubmatch(match)
+		fact, alphabet := parts[1], parts[2]
+		if fact != "as" {
+			if failed == nil {
+				failed = fmt.Errorf(
+					"says %s, and the mesh states %s about a consumer", match, orNothing(consumerFacts))
+			}
+			return match
+		}
+		switch alphabet {
+		case "":
+			return as
+		case "dns":
+			return asDNSLabel(as)
+		default:
+			if failed == nil {
+				failed = fmt.Errorf(
+					"says %s, and the mesh writes an identity as %s", match, orNothing(consumerAlphabets))
+			}
+			return match
+		}
+	})
+	if failed != nil {
+		return "", failed
+	}
+	return out, nil
+}
+
+// asDNSLabel writes a minted identity as a DNS label.
+//
+// The mesh's identities are already lower-case letters, digits and `_` (ConsumerIdentity), and
+// already short enough for the tightest backend they reach (CheckIdentity, twenty characters). So
+// this is the separator and nothing else — no lower-casing of what is already lower case, no
+// truncation to a limit the identity is already inside, no padding of a name that is already long
+// enough. Each of those would be the mesh guessing at a rule it has not been given.
+func asDNSLabel(as string) string {
+	return strings.ReplaceAll(as, "_", "-")
+}
+
+// CheckServes refuses a `serves` block that names a consumer fact or an alphabet the mesh does not
+// have, when the definition is parsed rather than when a consumer is resolved.
+//
+// A provision nobody consumes yet still has its rule read: a definition that would be refused the
+// first time somebody required it is a definition that is wrong now.
+func CheckServes(m Manifest) []string {
+	var problems []string
+	for _, provision := range sortedServes(m.Serves) {
+		for _, key := range sortedAnyKeys(m.Serves[provision]) {
+			text, ok := m.Serves[provision][key].(string)
+			if !ok {
+				continue
+			}
+			// A probe identity, because what is checked is the shape of the statement and not
+			// what any consumer is called.
+			if _, err := consumerInto(text, "mesh_node_module"); err != nil {
+				problems = append(problems, fmt.Sprintf(
+					"%s serves %s, and the value it serves as %q %s", m.Module, provision, key, err))
+			}
+		}
+	}
+	return problems
+}
+
+func sortedServes(serves map[string]map[string]any) []string {
+	out := make([]string, 0, len(serves))
+	for k := range serves {
+		out = append(out, k)
+	}
+	sort.Strings(out)
+	return out
+}
+
+func sortedAnyKeys(values map[string]any) []string {
+	out := make([]string, 0, len(values))
+	for k := range values {
+		out = append(out, k)
+	}
+	sort.Strings(out)
+	return out
+}
+
+// derivedFor is what the provider on this machine derives for one consumer of one provision
+// (novox/hq ADR 0201).
+//
+// Settled first, then derived: an operator may set a prefix on what the provider serves and the
+// mesh still fills the consumer's half of it ([ADR 0174]). Only the keys that actually name the
+// consumer are returned — the rest of a `serves` block is the same for every consumer and is
+// already in the provider's own definition, so repeating it here would be a second copy to go
+// stale.
+//
+// The first module in the resolved order that says it serves the provision answers, which is the
+// choice servedOnThisMachine makes for the consumer's half. Nothing serving it on this machine is
+// not an error: a contribution can reach a machine whose provider is a record or an adapter, and
+// then there is nothing derived to tell.
+func (r Resolution) derivedFor(provision, as, consumer, local string, settings SettingsBy) (map[string]any, error) {
+	for _, m := range r.Modules {
+		serves, said := m.Serves[provision]
+		if !said {
+			continue
+		}
+		var names map[string]any
+		for key, value := range serves {
+			if text, ok := value.(string); ok && strings.Contains(text, "${consumer:") {
+				if names == nil {
+					names = map[string]any{}
+				}
+				names[key] = value
+			}
+		}
+		if names == nil {
+			return nil, nil
+		}
+		// **A consumer that keeps several holders of this provision is refused** — this is issue
+		// 124's own failure one case to the side, and it would be just as quiet.
+		//
+		// Each holder gets its own login, `…_<local>` (ADR 0094), and a provider derives from the
+		// login, so it would make one resource per holder. The consumer's side has no such
+		// dimension: one binding file per provision, one `${bound:<provision>:<key>}`, both
+		// derived from the un-suffixed identity. So the provider would create the holder's
+		// resource and the consumer would be configured against a name nothing made — it would
+		// authenticate successfully and be refused on every object, which reads like a credential
+		// fault and is not one.
+		//
+		// Lifting this means giving the consumer's side a local dimension. That is a decision,
+		// not an omission, and until it is taken the mesh says so rather than guessing.
+		if local != "" {
+			return nil, fmt.Errorf(
+				"%s keeps several holders of %s (this one is %q), and %s derives %s for each "+
+					"consumer from the login the mesh minted. Each holder has its own login, and a "+
+					"consumer is told one value per requirement — so the two ends would name "+
+					"different things and nothing would compare them (novox/hq ADR 0201)",
+				consumer, local, provision, m.Module, orNothing(sortedAnyKeys(names)))
+		}
+		settled, err := Settle(names, settings[m.Module])
+		if err != nil {
+			return nil, fmt.Errorf("%s serving %s: %w", m.Module, provision, err)
+		}
+		derived, err := ServedTo(settled, as)
+		if err != nil {
+			return nil, fmt.Errorf("%s serving %s to %s: %w", m.Module, provision, as, err)
+		}
+		return derived, nil
+	}
+	return nil, nil
+}
+
+// notTranscribed refuses a consumer's file that writes out the value its provider derives for it,
+// instead of asking for it (novox/hq ADR 0201, issue 124).
+//
+// **What would have caught the one wrong instance.** The object store's three consumers each wrote
+// their bucket into their own configuration by hand. One of them named a predecessor's bucket, and
+// nothing compared it to what the provider would actually create: the module would have
+// authenticated successfully and been refused on every object, which reads like a credential fault
+// and is not one. It looked authoritative for months.
+//
+// The test is exact and costs one string search: a definition whose file already contains the
+// value the mesh is about to derive for it has written down somebody else's rule. It cannot be a
+// coincidence — a derived value carries the identity the mesh minted for this very consumer on
+// this very machine, which nothing else would spell out — and it cannot be checked afterwards,
+// because after substitution every consumer's file contains it legitimately.
+//
+// Only values that actually name the consumer are judged. A provider that serves a constant under
+// the same key serves the same constant to everyone, and a consumer repeating it is redundant
+// rather than wrong.
+func notTranscribed(resource map[string]any, known map[string]map[string]string, module string) error {
+	if fmt.Sprint(resource["type"]) != "file" {
+		return nil
+	}
+	content, ok := resource["content"].(string)
+	if !ok || content == "" {
+		return nil
+	}
+	for _, provision := range sortedKnown(known) {
+		values := known[provision]
+		identity := values["as"]
+		if identity == "" {
+			continue
+		}
+		for _, key := range sortedStringKeys(values) {
+			if key == "as" {
+				// The login is not derived from itself, and a consumer that must present it in a
+				// connection string legitimately has it from `${bound:…}` — which is what it will
+				// be after substitution, so this would judge the substitution, not the module.
+				continue
+			}
+			value := values[key]
+			if value == "" || !namesTheConsumer(value, identity) {
+				continue
+			}
+			if !strings.Contains(content, value) {
+				continue
+			}
+			return fmt.Errorf(
+				"%s writes %q into %v, and that is exactly what %s derives for it — a definition "+
+					"keeping its own copy of somebody else's naming rule is one that can disagree "+
+					"with it, silently. Say ${bound:%s:%s} and be told",
+				module, value, resource["id"], provision, provision, key)
+		}
+	}
+	return nil
+}
+
+// namesTheConsumer is whether a derived value was built from this consumer's identity — in the
+// alphabet it was minted in, or as a DNS label. A value that does not contain it was not derived
+// from it, whatever else it may be.
+func namesTheConsumer(value, identity string) bool {
+	return strings.Contains(value, identity) || strings.Contains(value, asDNSLabel(identity))
+}
+
+func sortedKnown(known map[string]map[string]string) []string {
+	out := make([]string, 0, len(known))
+	for k := range known {
+		out = append(out, k)
+	}
+	sort.Strings(out)
+	return out
+}
+
+func sortedStringKeys(values map[string]string) []string {
+	out := make([]string, 0, len(values))
+	for k := range values {
+		out = append(out, k)
+	}
+	sort.Strings(out)
+	return out
+}
diff --git a/internal/catalogue/declaration.go b/internal/catalogue/declaration.go
index d69eb7a..b2f651b 100644
--- a/internal/catalogue/declaration.go
+++ b/internal/catalogue/declaration.go
@@ -645,7 +645,16 @@ func (r Resolution) compose(with Rendering, owner map[string]string,
 			if err != nil {
 				return nil, err
 			}
-			file, err := boundFile(*found, m.Binds[to], ConsumerIdentity(r.Node, IdentitySource(m.Slug, m.Module)), own)
+			as := ConsumerIdentity(r.Node, IdentitySource(m.Slug, m.Module))
+			// What the provider derives for THIS consumer, filled here where the consumer is
+			// known (novox/hq ADR 0201). The same fill knownFor does below, so the binding file
+			// and the module's `${bound:…}` substitutions cannot say different things.
+			told := *found
+			told.Serves, err = ServedTo(told.Serves, as)
+			if err != nil {
+				return nil, fmt.Errorf("%s is told about %s: %w", m.Module, to, err)
+			}
+			file, err := boundFile(told, m.Binds[to], as, own)
 			if err != nil {
 				return nil, err
 			}
@@ -719,7 +728,10 @@ func (r Resolution) compose(with Rendering, owner map[string]string,
 			return nil, err
 		}
 		// And what its bindings say, for the half of a connection that is not secret.
-		known := knownFor(m, r.Needs, r.Node)
+		known, err := knownFor(m, r.Needs, r.Node)
+		if err != nil {
+			return nil, err
+		}
 		// A requirement answered on this same machine is not in r.Needs — its binding file is
 		// written from `here` (above) — and so `${bound:…}` could not name it, though the file
 		// beside it said the same facts. Filled from the same answer, so the two cannot disagree.
@@ -736,7 +748,11 @@ func (r Resolution) compose(with Rendering, owner map[string]string,
 			}
 			local := *answered
 			local.For = m.Module
-			for provision, values := range knownFor(m, []Needed{local}, r.Node) {
+			here, err := knownFor(m, []Needed{local}, r.Node)
+			if err != nil {
+				return nil, err
+			}
+			for provision, values := range here {
 				known[provision] = values
 			}
 		}
@@ -761,6 +777,17 @@ func (r Resolution) compose(with Rendering, owner map[string]string,
 		// And the machine underneath, which no binding of its own can tell it.
 		thisMachine := machineFacts(r, with.Names, with.MeshRange)
 
+		// **A definition that already holds the answer transcribed it** (novox/hq ADR 0201).
+		// Judged over what the module itself declares, and before anything is substituted: the
+		// mesh's own generated files — the binding, the contributions — legitimately carry the
+		// derived value, and after substitution so does every consumer's file, so this is the one
+		// moment the two can be told apart.
+		for _, own := range m.Resources {
+			if err := notTranscribed(own, known, m.Module); err != nil {
+				return nil, err
+			}
+		}
+
 		// Which of this module's files carry a secret, for the rule that a container may not read
 		// one of them as its environment without saying so (ADR 0086, issue 041).
 		secretFiles := secretFilesOf(resources)
@@ -1175,6 +1202,19 @@ type Contribution struct {
 	// requirement's name — everything providing `reverse-proxy` understands the same shape, which
 	// is what makes swapping one for another cost nothing.
 	Values map[string]any `json:"values"`
+	// Derived is what this provider's own definition said it derives for this consumer, already
+	// derived (novox/hq ADR 0201).
+	//
+	// **The provider is told, rather than recomputing it.** A served value may name the consumer's
+	// identity — a bucket named for who is asking, a database prefixed with it — and before this
+	// the rule lived twice: once in the provisioner's code, once transcribed into every consumer's
+	// definition. The mesh fills the provider's own statement here and delivers the same filled
+	// value to the consumer, so the two cannot disagree: there is no second computation to
+	// disagree with.
+	//
+	// Only the keys that are per-consumer. The rest of what the provider serves is the same for
+	// everyone and is in its own definition, where it already is.
+	Derived map[string]any `json:"derived,omitempty"`
 }
 
 // grantPath is where one consumer's sealed credential lands on the providing machine.
@@ -1266,12 +1306,17 @@ func (r Resolution) contributions(settings SettingsBy, grants []Grant,
 			// told about it and withdraws the login on its next pass.
 			continue
 		}
+		as := holderAs(ConsumerIdentity(g.Consumer, IdentitySource(g.Slug, g.From)), g.Local)
+		derived, err := r.derivedFor(g.Provision, as, g.From, g.Local, settings)
+		if err != nil {
+			return nil, err
+		}
 		out[g.Provision] = append(out[g.Provision], Contribution{
-			From: g.From, Node: g.Consumer, At: g.At, Values: g.Values,
+			From: g.From, Node: g.Consumer, At: g.At, Values: g.Values, Derived: derived,
 			// One holder per local name: the identity the consumer is known by, and the local name
 			// after it where the module keeps several (ADR 0094). Not a login any backend checks —
 			// a secret is not a login — so the identity limit does not apply to the suffix.
-			As:     holderAs(ConsumerIdentity(g.Consumer, IdentitySource(g.Slug, g.From)), g.Local),
+			As:     as,
 			Secret: grantPath(directories[g.Provision], g.Consumer, holderAs(g.From, g.Local)),
 		})
 		if granted[g.Provision] == nil {
diff --git a/internal/catalogue/derived_for_consumer_test.go b/internal/catalogue/derived_for_consumer_test.go
new file mode 100644
index 0000000..5d85206
--- /dev/null
+++ b/internal/catalogue/derived_for_consumer_test.go
@@ -0,0 +1,343 @@
+package catalogue
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+// What a provider derives for each consumer, said once and delivered to both ends
+// (novox/hq ADR 0201, issue 124).
+//
+// The failure these are written against: the object store's provisioner derived each consumer's
+// bucket from the login the mesh minted, in its own code, and the mesh had no channel to tell the
+// consumer which bucket that was — so all three consumers wrote the answer into their own
+// definitions by hand. Two were right. One named a predecessor's bucket and would have
+// authenticated successfully and been refused on every object. Each of them also named the
+// machine the module happens to run on, which a definition may not do.
+
+// store is an object store in the shape minio has: it serves a region and a port to everyone, and
+// a bucket named for whoever is asking.
+func store() Manifest {
+	return Manifest{
+		Module: "store", Version: "1",
+		Provides: FromAnywhere("s3-bucket"),
+		Listens:  []Listening{{Port: 9000, Protocol: "tcp", From: FromMesh}},
+		Serves: map[string]map[string]any{"s3-bucket": {
+			"region": "eu-west",
+			"bucket": "${consumer:as:dns}",
+		}},
+		Receives: map[string]string{"s3-bucket": "/var/lib/store/grants/mesh.json"},
+		Grants:   map[string]string{"s3-bucket": "/var/lib/store/grants"},
+		Resources: []map[string]any{{
+			"id": "server", "type": "container", "name": "store", "ports": []any{"9000"},
+		}},
+	}
+}
+
+// files is a consumer that writes the bucket into its own configuration — which is the thing it
+// could not do before, and had to transcribe.
+func files() Manifest {
+	return Manifest{
+		Module: "files", Version: "1", Slug: "files",
+		Requires: []string{"s3-bucket"},
+		Binds:    map[string]string{"s3-bucket": "/var/lib/files/store.json"},
+		Secrets:  map[string]string{"s3-bucket": "/var/lib/files/store.secret"},
+		Resources: []map[string]any{{
+			"id": "env", "type": "file", "path": "/var/lib/files/env", "mode": "0600",
+			"content": "BUCKET=${bound:s3-bucket:bucket}\nREGION=${bound:s3-bucket:region}\n",
+		}},
+	}
+}
+
+// pics is a second consumer of the same provider on the same machine: two derivations, neither
+// the other's.
+func pics() Manifest {
+	return Manifest{
+		Module: "pics", Version: "1", Slug: "pics",
+		Requires: []string{"s3-bucket"},
+		Binds:    map[string]string{"s3-bucket": "/var/lib/pics/store.json"},
+		Secrets:  map[string]string{"s3-bucket": "/var/lib/pics/store.secret"},
+		Resources: []map[string]any{{
+			"id": "env", "type": "file", "path": "/var/lib/pics/env", "mode": "0600",
+			"content": "BUCKET=${bound:s3-bucket:bucket}\n",
+		}},
+	}
+}
+
+// The three places the derived value lands must agree, because agreeing is the whole point: the
+// consumer's own file, the binding it reads as JSON, and the provider's contributions entry.
+func TestADerivedValueReachesBothEndsAndAgrees(t *testing.T) {
+	r, err := Resolve(shelf(store(), files()), []string{"store", "files"}, reachable(), World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := r.Declaration(Rendering{Grants: []Grant{{
+		Provision: "s3-bucket", Consumer: "workstation", From: "files", Slug: "files",
+		Values: map[string]any{}, Sealed: "c2VhbGVk",
+	}}})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// The mesh minted this identity for the consumer; the bucket is that identity as a DNS label.
+	// Derived here with the mesh's own function, so the test cannot agree with a wrong rule.
+	as := ConsumerIdentity("workstation", IdentitySource("files", "files"))
+	want := strings.ReplaceAll(as, "_", "-")
+	if want == as || !strings.Contains(as, "_") {
+		t.Fatalf("the mesh's identity %q has no separator to rewrite; this test proves nothing", as)
+	}
+
+	env := fileNamed(out, "files.env")
+	if env == nil {
+		t.Fatalf("the consumer was given no file: %v", out)
+	}
+	if got := env["content"].(string); !strings.Contains(got, "BUCKET="+want+"\n") {
+		t.Errorf("the consumer's own file was not told the bucket:\n%s\nwant BUCKET=%s", got, want)
+	}
+
+	binding := fileNamed(out, "files.bound-s3-bucket")
+	if binding == nil {
+		t.Fatalf("the consumer was given no binding: %v", out)
+	}
+	var said struct {
+		Serves map[string]any `json:"serves"`
+	}
+	if err := json.Unmarshal([]byte(binding["content"].(string)), &said); err != nil {
+		t.Fatal(err)
+	}
+	if said.Serves["bucket"] != want {
+		t.Errorf("the binding says the bucket is %q, want %q", said.Serves["bucket"], want)
+	}
+	// And what is the same for everybody is still the same for everybody.
+	if said.Serves["region"] != "eu-west" {
+		t.Errorf("the binding lost what the provider serves to all: %v", said.Serves)
+	}
+
+	given := storeGrants(t, out)
+	if len(given) != 1 {
+		t.Fatalf("the provider was told about %d consumer(s): %v", len(given), given)
+	}
+	if given[0].Derived["bucket"] != want {
+		t.Errorf("the provider was told the bucket is %v, and the consumer was told %q — "+
+			"the two ends disagree, which is the whole failure", given[0].Derived["bucket"], want)
+	}
+	// Only the per-consumer half. The region is the same for everyone and is already in the
+	// provider's own definition; repeating it here would be a copy to go stale.
+	if _, carried := given[0].Derived["region"]; carried {
+		t.Errorf("the provider was handed back what it already says for everyone: %v", given[0].Derived)
+	}
+}
+
+// Two consumers of one provider on one machine get two buckets, and neither gets the other's.
+func TestTwoConsumersOfOneProviderGetTheirOwnDerivation(t *testing.T) {
+	r, err := Resolve(shelf(store(), files(), pics()),
+		[]string{"store", "files", "pics"}, reachable(), World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := r.Declaration(Rendering{Grants: []Grant{
+		{Provision: "s3-bucket", Consumer: "workstation", From: "files", Slug: "files",
+			Values: map[string]any{}, Sealed: "c2VhbGVk"},
+		{Provision: "s3-bucket", Consumer: "workstation", From: "pics", Slug: "pics",
+			Values: map[string]any{}, Sealed: "c2VhbGVk"},
+	}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	forFiles := strings.ReplaceAll(ConsumerIdentity("workstation", IdentitySource("files", "files")), "_", "-")
+	forPics := strings.ReplaceAll(ConsumerIdentity("workstation", IdentitySource("pics", "pics")), "_", "-")
+	if forFiles == forPics {
+		t.Fatal("the two consumers were given the same identity; this test proves nothing")
+	}
+	if got := fileNamed(out, "files.env")["content"].(string); !strings.Contains(got, "BUCKET="+forFiles+"\n") {
+		t.Errorf("files was not given its own bucket:\n%s", got)
+	}
+	if got := fileNamed(out, "pics.env")["content"].(string); !strings.Contains(got, "BUCKET="+forPics+"\n") {
+		t.Errorf("pics was not given its own bucket:\n%s", got)
+	}
+	var buckets []any
+	for _, g := range storeGrants(t, out) {
+		buckets = append(buckets, g.Derived["bucket"])
+	}
+	if len(buckets) != 2 || buckets[0] == buckets[1] {
+		t.Errorf("the provider was told %v; it must be told one bucket per consumer", buckets)
+	}
+}
+
+// An operator may still set what the provider serves, and the mesh still derives the rest: the
+// setting is laid on first, then the consumer's half is filled.
+func TestASettingComposesWithADerivedValue(t *testing.T) {
+	r, err := Resolve(shelf(store(), files()), []string{"store", "files"}, reachable(), World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := r.Declaration(Rendering{
+		Settings: SettingsBy{"store": {{From: "the operator",
+			Values: map[string]any{"bucket": "team-${consumer:as:dns}"}}}},
+		Grants: []Grant{{Provision: "s3-bucket", Consumer: "workstation", From: "files", Slug: "files",
+			Values: map[string]any{}, Sealed: "c2VhbGVk"}},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "team-" + strings.ReplaceAll(ConsumerIdentity("workstation", IdentitySource("files", "files")), "_", "-")
+	if got := fileNamed(out, "files.env")["content"].(string); !strings.Contains(got, "BUCKET="+want+"\n") {
+		t.Errorf("the operator's prefix did not survive the derivation:\n%s\nwant BUCKET=%s", got, want)
+	}
+	if given := storeGrants(t, out); given[0].Derived["bucket"] != want {
+		t.Errorf("the provider was told %v, the consumer %q", given[0].Derived["bucket"], want)
+	}
+}
+
+// A fact or an alphabet the mesh does not have is refused where the definition is, not where a
+// consumer happens to be resolved — and the refusal says what may be said instead.
+func TestAServedValueNamingSomethingTheMeshDoesNotHaveIsRefused(t *testing.T) {
+	for _, c := range []struct{ value, says string }{
+		{"${consumer:node}", "as"},
+		{"${consumer:as:punycode}", "dns"},
+	} {
+		m := store()
+		m.Serves["s3-bucket"]["bucket"] = c.value
+		raw, err := json.Marshal(m)
+		if err != nil {
+			t.Fatal(err)
+		}
+		_, err = ParseManifest(raw)
+		if err == nil {
+			t.Fatalf("%s was accepted", c.value)
+		}
+		if !strings.Contains(err.Error(), c.value) {
+			t.Errorf("the refusal of %s does not quote it: %v", c.value, err)
+		}
+		if !strings.Contains(err.Error(), c.says) {
+			t.Errorf("the refusal of %s does not say what may be said (%q): %v", c.value, c.says, err)
+		}
+	}
+}
+
+// `dns` is checked against an identity the mesh actually mints, not an invented string.
+func TestTheDNSAlphabetIsTheMintedIdentityWithItsSeparatorRewritten(t *testing.T) {
+	as := ConsumerIdentity("anchor", IdentitySource("ncloud", "nextcloud"))
+	if err := CheckIdentity("anchor", IdentitySource("ncloud", "nextcloud")); err != nil {
+		t.Fatalf("the mesh would not mint this identity at all: %v", err)
+	}
+	label := asDNSLabel(as)
+	if strings.Contains(label, "_") {
+		t.Errorf("%q is not a DNS label", label)
+	}
+	if strings.ReplaceAll(label, "-", "_") != as {
+		t.Errorf("%q is not %q with its separator rewritten", label, as)
+	}
+}
+
+// The check that would have caught the one wrong instance: a consumer that writes the derived
+// value into its own definition instead of asking for it is refused, whether it transcribed the
+// right answer or a predecessor's.
+func TestAConsumerThatTranscribesWhatItsProviderDerivesIsRefused(t *testing.T) {
+	as := ConsumerIdentity("workstation", IdentitySource("files", "files"))
+	transcribed := strings.ReplaceAll(as, "_", "-")
+
+	m := files()
+	m.Resources = []map[string]any{{
+		"id": "env", "type": "file", "path": "/var/lib/files/env", "mode": "0600",
+		// Exactly what the provider will create — correct today, and a copy of a rule that is
+		// not this module's.
+		"content": "BUCKET=" + transcribed + "\n",
+	}}
+	r, err := Resolve(shelf(store(), m), []string{"store", "files"}, reachable(), World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = r.Declaration(Rendering{Grants: []Grant{{
+		Provision: "s3-bucket", Consumer: "workstation", From: "files", Slug: "files",
+		Values: map[string]any{}, Sealed: "c2VhbGVk",
+	}}})
+	if err == nil {
+		t.Fatal("a definition holding its own copy of the provider's naming rule was accepted")
+	}
+	if !strings.Contains(err.Error(), "${bound:s3-bucket:bucket}") {
+		t.Errorf("the refusal does not say what to write instead: %v", err)
+	}
+
+	// And a constant the provider serves to everyone is not a transcription: repeating it is
+	// redundant, not wrong, and refusing it would be the mesh policing style.
+	m.Resources = []map[string]any{{
+		"id": "env", "type": "file", "path": "/var/lib/files/env", "mode": "0600",
+		"content": "REGION=eu-west\n",
+	}}
+	r, err = Resolve(shelf(store(), m), []string{"store", "files"}, reachable(), World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := r.Declaration(Rendering{Grants: []Grant{{
+		Provision: "s3-bucket", Consumer: "workstation", From: "files", Slug: "files",
+		Values: map[string]any{}, Sealed: "c2VhbGVk",
+	}}}); err != nil {
+		t.Errorf("a value the provider serves to everyone was judged a transcription: %v", err)
+	}
+}
+
+func storeGrants(t *testing.T, out []map[string]any) []Contribution {
+	t.Helper()
+	for _, r := range out {
+		if r["path"] != "/var/lib/store/grants/mesh.json" {
+			continue
+		}
+		var parsed struct {
+			Given []Contribution `json:"given"`
+		}
+		if err := json.Unmarshal([]byte(r["content"].(string)), &parsed); err != nil {
+			t.Fatal(err)
+		}
+		return parsed.Given
+	}
+	t.Fatalf("the provider was given no contributions file: %v", out)
+	return nil
+}
+
+// A consumer that keeps SEVERAL holders of one provision is refused, rather than told one thing
+// while its provider is told another.
+//
+// **This is issue 124's own failure, one case to the side.** The mesh gives each holder its own
+// login — `mesh_node_mod_<local>` (ADR 0094) — and the provider derives from the login, so it
+// would make one resource per holder. The consumer's side has no such dimension: there is one
+// binding file per provision and one `${bound:<provision>:<key>}`, both derived from the
+// un-suffixed identity. So the provider would create `…-mod-cold` and the consumer would be
+// configured against `…-mod`: it would authenticate successfully and be refused on every object,
+// which is exactly the fault this whole record exists to end.
+//
+// Refused, loudly, at the one place that can see both halves. Lifting it means giving the
+// consumer's side a local dimension, which is a decision and not an omission.
+func TestAConsumerWithSeveralHoldersOfADerivingProviderIsRefused(t *testing.T) {
+	m := files()
+	// Two holders of the one provision, the shape ADR 0094 gives a module that keeps several.
+	m.Secrets = nil
+	m.SecretsMany = map[string]map[string]string{"s3-bucket": {
+		"hot":  "/var/lib/files/hot.secret",
+		"cold": "/var/lib/files/cold.secret",
+	}}
+	m.Resources = []map[string]any{{
+		"id": "env", "type": "file", "path": "/var/lib/files/env", "mode": "0600",
+		"content": "BUCKET=${bound:s3-bucket:bucket}\n",
+	}}
+	r, err := Resolve(shelf(store(), m), []string{"store", "files"}, reachable(), World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = r.Declaration(Rendering{Grants: []Grant{
+		{Provision: "s3-bucket", Consumer: "workstation", From: "files", Slug: "files",
+			Local: "hot", Values: map[string]any{}, Sealed: "c2VhbGVk"},
+		{Provision: "s3-bucket", Consumer: "workstation", From: "files", Slug: "files",
+			Local: "cold", Values: map[string]any{}, Sealed: "c2VhbGVk"},
+	}})
+	if err == nil {
+		t.Fatal("a consumer with several holders of a deriving provider was accepted; " +
+			"its two ends would have disagreed in silence")
+	}
+	for _, want := range []string{"files", "s3-bucket", "bucket"} {
+		if !strings.Contains(err.Error(), want) {
+			t.Errorf("the refusal does not name %q: %v", want, err)
+		}
+	}
+}
diff --git a/internal/catalogue/manifest.go b/internal/catalogue/manifest.go
index 8528c9f..9dd482e 100644
--- a/internal/catalogue/manifest.go
+++ b/internal/catalogue/manifest.go
@@ -1428,6 +1428,10 @@ func ParseManifest(raw []byte) (Manifest, error) {
 				"%s serves %q to whoever requires it, and does not provide it", m.Module, to))
 		}
 	}
+	// A served value may be derived for the consumer it is served to (novox/hq ADR 0201). Read
+	// here, where the definition is, rather than when somebody first requires it: a rule that
+	// would be refused at the first consumer is wrong from the moment it is written.
+	problems = append(problems, CheckServes(m)...)
 	for to, where := range m.Binds {
 		if !placedOrAbsolute(where) {
 			problems = append(problems, fmt.Sprintf(
@@ -1622,6 +1626,13 @@ func ParseManifest(raw []byte) (Manifest, error) {
 				}
 			}
 		}
+		// **A scheduled step may hold this module's own containers still while it runs**
+		// (novox/hq ADR 0189). What the host judges is the declaration it receives — whether each
+		// id is a container placed on that machine; what belongs here is what only the definition
+		// shows: that the ids are this module's, that they are containers, and that the step is
+		// scheduled. A module naming a neighbour's container would be a module that can stop the
+		// mesh, and the manifest is where that is visible.
+		problems = append(problems, whileStoppedProblems(m, r, hasSchedule(r))...)
 	}
 	for name, own := range m.OwnSecrets {
 		if !placedOrAbsolute(own.Path) {
@@ -2153,3 +2164,71 @@ func (o OwnSecrets) Paths() map[string]string {
 // InstancesInterchangeable is the one value of a definition's `instances`: the module is the same
 // on every machine, so any instance may answer for the module.
 const InstancesInterchangeable = "interchangeable"
+
+// WhileStopped is the resource key naming the containers a scheduled step holds still while it
+// runs (novox/hq ADR 0189). Carried to the host unchanged, like `schedule`.
+const WhileStopped = "while-stopped"
+
+// hasSchedule is whether a resource declares a cadence, as a string.
+func hasSchedule(r map[string]any) bool {
+	s, _ := r["schedule"].(string)
+	return s != ""
+}
+
+// whileStoppedProblems judges one container's maintenance window against its own definition
+// (novox/hq ADR 0189).
+//
+// Three things the manifest is the only place to see: that the step is scheduled (a one-time
+// offline job says *before* rather than *instead of* — at apply the host already has a window,
+// because the declaration is applied in order and a run-once step gates what follows); that every
+// id it names is **this module's own** container; and that it does not name itself.
+//
+// The host checks the fourth — that the container is actually placed on that machine — because
+// that is a fact about the declaration and not about the definition.
+func whileStoppedProblems(m Manifest, r map[string]any, scheduled bool) []string {
+	raw, present := r[WhileStopped]
+	if !present {
+		return nil
+	}
+	ids, ok := raw.([]any)
+	if !ok {
+		return []string{fmt.Sprintf(
+			"%s declares %s on %v as a %T; it is a list of this module's container ids",
+			m.Module, WhileStopped, r["id"], raw)}
+	}
+	var problems []string
+	if len(ids) > 0 && !scheduled {
+		problems = append(problems, fmt.Sprintf(
+			"%s declares %s on %v, which has no schedule. A maintenance window is for a recurring "+
+				"step: at apply the mesh already has one, because a run-once step gates what is "+
+				"declared after it (novox/hq ADR 0189)", m.Module, WhileStopped, r["id"]))
+	}
+	containers := map[string]bool{}
+	for _, own := range m.Resources {
+		if fmt.Sprint(own["type"]) == "container" {
+			containers[fmt.Sprint(own["id"])] = true
+		}
+	}
+	for _, each := range ids {
+		id, ok := each.(string)
+		if !ok {
+			problems = append(problems, fmt.Sprintf(
+				"%s declares %s on %v naming a %T; each entry is a container's id",
+				m.Module, WhileStopped, r["id"], each))
+			continue
+		}
+		if id == fmt.Sprint(r["id"]) {
+			problems = append(problems, fmt.Sprintf(
+				"%s declares %s on %v naming itself", m.Module, WhileStopped, r["id"]))
+			continue
+		}
+		if !containers[id] {
+			problems = append(problems, fmt.Sprintf(
+				"%s declares %s on %v naming %q, which is not a container this module declares. "+
+					"A step may hold still its own module's containers and nobody else's — one "+
+					"that could quiesce a neighbour could stop the mesh",
+				m.Module, WhileStopped, r["id"], id))
+		}
+	}
+	return problems
+}
diff --git a/internal/catalogue/while_stopped_test.go b/internal/catalogue/while_stopped_test.go
new file mode 100644
index 0000000..39442a8
--- /dev/null
+++ b/internal/catalogue/while_stopped_test.go
@@ -0,0 +1,89 @@
+package catalogue
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+// A scheduled step may hold its module's own containers still while it runs (novox/hq ADR 0189).
+//
+// The host judges what it receives — whether each id is a container on that machine. What the
+// definition is the only place to see is judged here, near whoever wrote it.
+
+func aStoreManifest(step map[string]any) []byte {
+	m := map[string]any{
+		"module": "distribution", "version": "1",
+		"resources": []any{
+			map[string]any{"id": "store", "type": "container", "name": "mesh-registry",
+				"image": "registry@sha256:" + strings.Repeat("a", 64)},
+			step,
+		},
+	}
+	raw, _ := json.Marshal(m)
+	return raw
+}
+
+func TestAMaintenanceWindowOnItsOwnModulesContainerIsAccepted(t *testing.T) {
+	raw := aStoreManifest(map[string]any{
+		"id": "collect", "type": "container", "name": "mesh-registry-collect",
+		"image":    "registry@sha256:" + strings.Repeat("a", 64),
+		"schedule": "30 3 * * *", "while-stopped": []any{"store"},
+	})
+	if _, err := ParseManifest(raw); err != nil {
+		t.Fatalf("a step holding its own module's container still was refused: %v", err)
+	}
+}
+
+func TestAMaintenanceWindowIsRefusedWhereTheDefinitionShowsItCannotMean(t *testing.T) {
+	for _, c := range []struct {
+		name string
+		step map[string]any
+		says string
+	}{
+		{
+			"on a step with no schedule",
+			map[string]any{"id": "collect", "type": "container", "name": "c",
+				"image":         "registry@sha256:" + strings.Repeat("a", 64),
+				"while-stopped": []any{"store"}},
+			"gates what is declared after it",
+		},
+		{
+			"on a run-once step, which already has order",
+			map[string]any{"id": "collect", "type": "container", "name": "c",
+				"image":    "registry@sha256:" + strings.Repeat("a", 64),
+				"run-once": true, "while-stopped": []any{"store"}},
+			"A maintenance window is for a recurring step",
+		},
+		{
+			"naming a container this module does not declare",
+			map[string]any{"id": "collect", "type": "container", "name": "c",
+				"image":    "registry@sha256:" + strings.Repeat("a", 64),
+				"schedule": "30 3 * * *", "while-stopped": []any{"the-broker"}},
+			"could quiesce a neighbour could stop the mesh",
+		},
+		{
+			"naming itself",
+			map[string]any{"id": "collect", "type": "container", "name": "c",
+				"image":    "registry@sha256:" + strings.Repeat("a", 64),
+				"schedule": "30 3 * * *", "while-stopped": []any{"collect"}},
+			"naming itself",
+		},
+		{
+			"written as something that is not a list",
+			map[string]any{"id": "collect", "type": "container", "name": "c",
+				"image":    "registry@sha256:" + strings.Repeat("a", 64),
+				"schedule": "30 3 * * *", "while-stopped": "store"},
+			"a list of this module's container ids",
+		},
+	} {
+		_, err := ParseManifest(aStoreManifest(c.step))
+		if err == nil {
+			t.Errorf("%s was accepted", c.name)
+			continue
+		}
+		if !strings.Contains(err.Error(), c.says) {
+			t.Errorf("%s: the refusal does not say %q:\n%v", c.name, c.says, err)
+		}
+	}
+}
diff --git a/internal/inventory/collection.go b/internal/inventory/collection.go
new file mode 100644
index 0000000..4b5bf67
--- /dev/null
+++ b/internal/inventory/collection.go
@@ -0,0 +1,242 @@
+package inventory
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+)
+
+// What the artifact store keeps, and what it may let go (novox/hq ADR 0189, issue 108).
+//
+// The store has never collected anything: every build pushes another layer set and nothing has
+// ever removed one. The registry's own answer — collect what no tag names — is wrong here, because
+// the mesh pushes each artifact under one moving tag and pins machines by digest, so every build
+// but the newest is untagged and some machine may still be running it.
+//
+// **So the mesh decides, from its own records, and it never has to look in the store to do it.**
+// It has never put anything there it did not record, which means every digest it could remove is
+// already in a build row. A digest the mesh did not record making is therefore never named here —
+// not as a safety margin but as the rule restated, and it is what keeps the sweep away from the
+// images genesis pushed before any record existed (04-ISSUES/102, F4).
+
+// KeptBuilds is how many successful builds of each module keep their artifacts, counting the
+// newest. The newest is what the mesh hands a machine now; the four behind it are how far back a
+// release that turns out wrong can be taken.
+const KeptBuilds = 5
+
+// ToCollect is every artifact the mesh made, no longer keeps, and has not already collected.
+//
+// Three reasons an artifact stays, and nothing else is a reason:
+//
+//   - **a definition names it** — the reference appears in a module's recorded manifest, which is
+//     what the mesh would hand a machine now. No age limit: this is the floor;
+//   - **the mesh can still go back to it** — it is an artifact of one of the KeptBuilds most
+//     recent successful builds of its module;
+//   - it was already collected, in which case there is nothing left to do.
+//
+// Returned in a stated order so two runs over the same records ask for the same things in the
+// same sequence, which is what makes a failed sweep safe to simply run again.
+func (i *Inventory) ToCollect(ctx context.Context) ([]string, error) {
+	keep, err := i.keptReferences(ctx)
+	if err != nil {
+		return nil, err
+	}
+	rows, err := i.store.Pool().Query(ctx,
+		// Every artifact of every successful build, oldest first, minus what has already been
+		// collected. A failed build published nothing, so it names nothing to remove.
+		`select b.made
+		   from build b
+		  where b.failed = '' and b.module is not null and b.module <> ''
+		  order by b.at asc, b.id asc`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	collected, err := i.alreadyCollected(ctx)
+	if err != nil {
+		return nil, err
+	}
+	seen := map[string]bool{}
+	var out []string
+	for rows.Next() {
+		var raw []byte
+		if err := rows.Scan(&raw); err != nil {
+			return nil, err
+		}
+		var made []Artifact
+		if err := json.Unmarshal(raw, &made); err != nil {
+			// One unreadable record must not stop the rest being collected — and an artifact this
+			// row named is simply not offered, which errs toward keeping.
+			continue
+		}
+		for _, a := range made {
+			if a.Reference == "" || keep[a.Reference] || collected[a.Reference] || seen[a.Reference] {
+				continue
+			}
+			seen[a.Reference] = true
+			out = append(out, a.Reference)
+		}
+	}
+	return out, rows.Err()
+}
+
+// keptReferences is every artifact reference the mesh still keeps, for either of the two reasons.
+func (i *Inventory) keptReferences(ctx context.Context) (map[string]bool, error) {
+	keep := map[string]bool{}
+
+	// **Whatever a definition the mesh holds names.** Read as text rather than by walking the
+	// resource shapes: a reference may be a container's image, a bundle's source, or a field some
+	// later kind of resource grows, and what matters is only whether the mesh could hand this
+	// string to a machine. A manifest that mentions it is a manifest that might.
+	manifests, err := i.store.Pool().Query(ctx, `select manifest::text from module where manifest is not null`)
+	if err != nil {
+		return nil, err
+	}
+	defer manifests.Close()
+	var named []string
+	for manifests.Next() {
+		var text string
+		if err := manifests.Scan(&text); err != nil {
+			return nil, err
+		}
+		named = append(named, text)
+	}
+	if err := manifests.Err(); err != nil {
+		return nil, err
+	}
+
+	// The KeptBuilds most recent successful builds of each module, whole.
+	recent, err := i.store.Pool().Query(ctx,
+		`select made from (
+		    select made, row_number() over (partition by module order by at desc, id desc) as back
+		      from build
+		     where failed = '' and module is not null and module <> ''
+		 ) ranked where back <= $1`, KeptBuilds)
+	if err != nil {
+		return nil, err
+	}
+	defer recent.Close()
+	for recent.Next() {
+		var raw []byte
+		if err := recent.Scan(&raw); err != nil {
+			return nil, err
+		}
+		var made []Artifact
+		if err := json.Unmarshal(raw, &made); err != nil {
+			continue
+		}
+		for _, a := range made {
+			if a.Reference != "" {
+				keep[a.Reference] = true
+			}
+		}
+	}
+	if err := recent.Err(); err != nil {
+		return nil, err
+	}
+
+	// And anything a manifest mentions. Done after the recent set so the scan runs over the
+	// candidates rather than over every reference ever recorded: a manifest holds a reference
+	// composed with the store's address or kept bare, so the search is for the digest within it.
+	if len(named) > 0 {
+		all, err := i.everyReferenceMade(ctx)
+		if err != nil {
+			return nil, err
+		}
+		for _, reference := range all {
+			if keep[reference] {
+				continue
+			}
+			digest := digestIn(reference)
+			if digest == "" {
+				// Not something the store holds by digest; nothing here can speak for it, so it
+				// is kept rather than guessed about.
+				keep[reference] = true
+				continue
+			}
+			for _, text := range named {
+				if strings.Contains(text, digest) {
+					keep[reference] = true
+					break
+				}
+			}
+		}
+	}
+	return keep, nil
+}
+
+// everyReferenceMade is every artifact reference any successful build recorded.
+func (i *Inventory) everyReferenceMade(ctx context.Context) ([]string, error) {
+	rows, err := i.store.Pool().Query(ctx,
+		`select made from build where failed = '' and module is not null and module <> ''`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	seen := map[string]bool{}
+	var out []string
+	for rows.Next() {
+		var raw []byte
+		if err := rows.Scan(&raw); err != nil {
+			return nil, err
+		}
+		var made []Artifact
+		if err := json.Unmarshal(raw, &made); err != nil {
+			continue
+		}
+		for _, a := range made {
+			if a.Reference == "" || seen[a.Reference] {
+				continue
+			}
+			seen[a.Reference] = true
+			out = append(out, a.Reference)
+		}
+	}
+	return out, rows.Err()
+}
+
+// digestIn is the `sha256:<hex>` a reference names, empty when it names none.
+func digestIn(reference string) string {
+	for _, marker := range []string{"@sha256:", "/sha256:"} {
+		if _, after, ok := strings.Cut(reference, marker); ok {
+			return "sha256:" + after
+		}
+	}
+	return ""
+}
+
+// alreadyCollected is what the store has already been asked to let go.
+func (i *Inventory) alreadyCollected(ctx context.Context) (map[string]bool, error) {
+	rows, err := i.store.Pool().Query(ctx, `select reference from artifact_collected`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := map[string]bool{}
+	for rows.Next() {
+		var reference string
+		if err := rows.Scan(&reference); err != nil {
+			return nil, err
+		}
+		out[reference] = true
+	}
+	return out, rows.Err()
+}
+
+// MarkCollected records that the store no longer holds these.
+//
+// **A store that answered "not found" is recorded too.** The outcome wanted is that the artifact
+// is gone, and it is; retrying it every sweep for ever is the failure this table exists to
+// prevent. Only a store that could not be reached, or refused, leaves a reference unmarked — and
+// then the next sweep asks again, which is what should happen.
+func (i *Inventory) MarkCollected(ctx context.Context, references []string) error {
+	for _, reference := range references {
+		if _, err := i.store.Pool().Exec(ctx,
+			`insert into artifact_collected (reference) values ($1) on conflict (reference) do nothing`,
+			reference); err != nil {
+			return err
+		}
+	}
+	return nil
+}
diff --git a/internal/inventory/collection_test.go b/internal/inventory/collection_test.go
new file mode 100644
index 0000000..b28c3ec
--- /dev/null
+++ b/internal/inventory/collection_test.go
@@ -0,0 +1,147 @@
+package inventory
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// What the store keeps, and what it may let go (novox/hq ADR 0189, issue 108).
+//
+// The store has collected nothing since it was raised, and the registry's own answer — collect
+// what no tag names — would delete images machines are running, because the mesh pushes under one
+// moving tag and pins by digest. So the rule is the mesh's, read from its own records, and these
+// are the three reasons an artifact stays and the one reason it goes.
+
+// ref is an artifact reference as the mesh records one.
+func ref(module, artifact string, n int) string {
+	return fmt.Sprintf("%s%s/%s@sha256:%064x", catalogue.ArtifactStoreScheme, module, artifact, n)
+}
+
+// built records one successful build of a module publishing one image.
+func built(t *testing.T, inv *Inventory, id, module string, n int) string {
+	t.Helper()
+	reference := ref(module, "app", n)
+	b := aBuild(id, module, "")
+	b.Made = []Artifact{{Name: "app", Kind: "image", Reference: reference}}
+	if err := inv.RecordBuild(context.Background(), b); err != nil {
+		t.Fatal(err)
+	}
+	return reference
+}
+
+func TestTheStoreKeepsTheRecentBuildsAndLetsGoOfTheRest(t *testing.T) {
+	inv := fresh(t)
+	ctx := context.Background()
+
+	// Eight builds of one module, oldest first. Five are kept — the newest, and the four a
+	// release that turns out wrong can be taken back to.
+	var made []string
+	for i := 1; i <= 8; i++ {
+		made = append(made, built(t, inv, fmt.Sprintf("b%02d", i), "web", i))
+	}
+
+	go_, err := inv.ToCollect(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := made[:3] // the three oldest
+	if len(go_) != len(want) {
+		t.Fatalf("offered %v to collect; want the %d oldest of %d", go_, len(want), len(made))
+	}
+	for i := range want {
+		if go_[i] != want[i] {
+			t.Fatalf("offered %v; want %v — and in that order, so a failed sweep is safe to run again",
+				go_, want)
+		}
+	}
+}
+
+func TestADefinitionNamingAnArtifactKeepsItHoweverOldItIs(t *testing.T) {
+	// The floor: no age limit. A module recorded at an older commit still names what the mesh
+	// would hand a machine now, and that is what must not be collected out from under it.
+	inv := fresh(t)
+	ctx := context.Background()
+
+	var made []string
+	for i := 1; i <= 8; i++ {
+		made = append(made, built(t, inv, fmt.Sprintf("b%02d", i), "web", i))
+	}
+	oldest := made[0]
+
+	// A definition the mesh holds, whose container runs that oldest image.
+	m := catalogue.Manifest{Module: "web", Version: "1", Resources: []map[string]any{{
+		"id": "app", "type": "container", "name": "web", "image": oldest,
+	}}}
+	if err := inv.RegisterModule(ctx, m, Source{Repository: "https://forge.invalid/web.git"}); err != nil {
+		t.Fatal(err)
+	}
+
+	go_, err := inv.ToCollect(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, reference := range go_ {
+		if reference == oldest {
+			t.Fatalf("the mesh offered to collect %s, which a definition it holds names", oldest)
+		}
+	}
+	if len(go_) != 2 {
+		t.Fatalf("offered %v; want the two oldest that nothing names", go_)
+	}
+}
+
+func TestWhatHasBeenCollectedIsNotOfferedAgain(t *testing.T) {
+	// Without this the sweep reissues a delete for every artifact it has ever collected, every
+	// time it runs, for ever — a number of requests that grows with the mesh's whole history.
+	inv := fresh(t)
+	ctx := context.Background()
+	for i := 1; i <= 7; i++ {
+		built(t, inv, fmt.Sprintf("b%02d", i), "web", i)
+	}
+	first, err := inv.ToCollect(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(first) != 2 {
+		t.Fatalf("offered %v, want two", first)
+	}
+	if err := inv.MarkCollected(ctx, first); err != nil {
+		t.Fatal(err)
+	}
+	again, err := inv.ToCollect(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(again) != 0 {
+		t.Fatalf("offered %v again after collecting it", again)
+	}
+}
+
+func TestAFailedBuildNamesNothingToCollectAndEachModuleIsCountedOnItsOwn(t *testing.T) {
+	inv := fresh(t)
+	ctx := context.Background()
+
+	// A failed build published nothing, so it is neither kept nor collected — and it must not
+	// count against the module's five.
+	for i := 1; i <= 6; i++ {
+		built(t, inv, fmt.Sprintf("w%02d", i), "web", i)
+	}
+	if err := inv.RecordBuild(ctx, aBuild("w99", "web", "the recipe would not build")); err != nil {
+		t.Fatal(err)
+	}
+	// And a second module with three builds keeps all three: five each, not five between them.
+	for i := 1; i <= 3; i++ {
+		built(t, inv, fmt.Sprintf("d%02d", i), "db", 100+i)
+	}
+
+	go_, err := inv.ToCollect(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(go_) != 1 || go_[0] != ref("web", "app", 1) {
+		t.Fatalf("offered %v; want only web's oldest — db's three are all within its five", go_)
+	}
+}
diff --git a/internal/inventory/migrations/0056-what-the-store-no-longer-keeps.sql b/internal/inventory/migrations/0056-what-the-store-no-longer-keeps.sql
new file mode 100644
index 0000000..28f16d7
--- /dev/null
+++ b/internal/inventory/migrations/0056-what-the-store-no-longer-keeps.sql
@@ -0,0 +1,23 @@
+-- What the artifact store no longer keeps (novox/hq ADR 0189, issue 108).
+--
+-- The mesh removes from its store only what it put there and can account for: every digest it
+-- could remove is already in a build record, so the sweep reads its own records rather than
+-- enumerating the store. What it does not get from those records is whether it has already
+-- removed something -- `build.made` says what that build published, for ever, which is history
+-- and not an index of what is on disk.
+--
+-- Without this the sweep would reissue a delete for every artifact it has ever collected, every
+-- time it runs, and each one would answer 404 -- a number of requests that grows with the mesh's
+-- whole history and never shrinks.
+--
+-- Keyed by the reference as the mesh records it (`artifact-store://<module>/<artifact>@sha256:…`),
+-- because that is the identity the record uses everywhere else. Not a foreign key to build: two
+-- builds can publish the same digest (the same source built twice produces the same bytes), and
+-- what is collected is the artifact, not the attempt that made it.
+create table artifact_collected (
+    reference text        primary key,
+
+    -- When the store answered. Kept so a reader of an old build record can tell "this artifact is
+    -- gone" from "this artifact was never there", which are different kinds of surprise.
+    at        timestamptz not null default now()
+);