diff --git a/modules/artifact-store-tools/cmd/artifact-store-tools/gone.go b/modules/artifact-store-tools/cmd/artifact-store-tools/gone.go
index e9804f483..cca4a96df 100644
--- a/modules/artifact-store-tools/cmd/artifact-store-tools/gone.go
+++ b/modules/artifact-store-tools/cmd/artifact-store-tools/gone.go
@@ -4,7 +4,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"sort"
-	"time"
+
+	sweep "git.novox.be/novox/mesh-delivery/contracts/go/seats/meshartifactsweep"
 )
 
 // The holders whose states this module reads, one constant each (a reader names its holder once; ADR 0634 §4).
@@ -13,38 +14,26 @@ const (
 	indexerModule  = "mesh-delivery-indexer"
 )
 
-// ArtifactsGoneEvent is the event the seat mesh-artifact-sweep says when the store does not hold an artifact a
-// builder's key names. The seat is a seat-list seat, which has no generated types, so its two bodies are the holder's
-// own: this module is the one that says the event and answers the verb held.
-const ArtifactsGoneEvent = "artifacts-gone"
+// The seat mesh-artifact-sweep types the answer of its verb held and the body of its event artifacts-gone; this module
+// holds the seat, so it answers and says them in those types.
+type (
+	// HeldAnswer is the answer of the seat's verb held.
+	HeldAnswer = sweep.HeldAnswer
+	// ArtifactsGone is the body of the seat's event artifacts-gone.
+	ArtifactsGone = sweep.ArtifactsGone
+)
 
-// HeldAnswer is the answer of the seat's verb held: the references the store holds, and those it answered 404 for. A
-// reference the store could not be asked about is in neither, and named in Unknown with why.
-type HeldAnswer struct {
-	Store   string            `json:"store,omitempty"`
-	Held    []string          `json:"held"`
-	Gone    []string          `json:"gone"`
-	Unknown map[string]string `json:"unknown,omitempty"`
-}
+// GoneSubject is where the seat says artifacts-gone.
+const GoneSubject = sweep.SubjectArtifactsGone
 
-// ArtifactsGone is the body of ArtifactsGoneEvent: the module whose builder's key names a gone artifact, the key and
-// its fingerprint, and every reference of it the store does not hold.
-type ArtifactsGone struct {
-	Event       string    `json:"event"`
-	Module      string    `json:"module"`
-	Key         string    `json:"key"`
-	Fingerprint string    `json:"fingerprint"`
-	Gone        []string  `json:"gone"`
-	At          time.Time `json:"at"`
-}
-
-// EncodeArtifactsGone is the event's body, the references sorted.
+// EncodeArtifactsGone is the event's body, the references sorted; it refuses one naming no module, no fingerprint or no
+// gone reference.
 func EncodeArtifactsGone(e ArtifactsGone) ([]byte, error) {
-	e.Event = ArtifactsGoneEvent
+	e.Event = sweep.EventArtifactsGone
 	e.Gone = append([]string(nil), e.Gone...)
 	sort.Strings(e.Gone)
 	if e.Module == "" || e.Fingerprint == "" || len(e.Gone) == 0 {
-		return nil, fmt.Errorf("%s names a module, a fingerprint and at least one gone reference", ArtifactsGoneEvent)
+		return nil, fmt.Errorf("%s names a module, a fingerprint and at least one gone reference", sweep.EventArtifactsGone)
 	}
 	return json.Marshal(e)
 }
diff --git a/modules/artifact-store-tools/cmd/artifact-store-tools/holder.go b/modules/artifact-store-tools/cmd/artifact-store-tools/holder.go
index 1d46218cc..1f3d8f09b 100644
--- a/modules/artifact-store-tools/cmd/artifact-store-tools/holder.go
+++ b/modules/artifact-store-tools/cmd/artifact-store-tools/holder.go
@@ -49,8 +49,6 @@ const (
 	FindingsState = meshconditions.StateFindings
 	// Module is this module, the observer its findings name.
 	Module = "artifact-store-tools"
-	// GoneSubject is where the seat says artifacts-gone.
-	GoneSubject = "mesh.seat." + catalogue.ArtifactSweepSeat + ".event." + ArtifactsGoneEvent
 )
 
 // The sweep's bounds, the controller's (cmd/mesh-controller/collect.go mostPerSweep, sweepBudget).
@@ -628,7 +626,8 @@ func (h *Holder) sayGone(j *judged, refs []string, how string) {
 		for _, b := range ref.Builds {
 			g := byKey[b.Key]
 			if g == nil {
-				g = &ArtifactsGone{Module: b.Module, Key: b.Key, Fingerprint: b.FP, At: h.now().UTC()}
+				at := h.now().UTC()
+				g = &ArtifactsGone{Module: b.Module, Key: b.Key, Fingerprint: b.FP, At: &at}
 				byKey[b.Key] = g
 				keys = append(keys, b.Key)
 			}
diff --git a/modules/artifact-store-tools/go.mod b/modules/artifact-store-tools/go.mod
index 66c3b9f23..adcd679f0 100644
--- a/modules/artifact-store-tools/go.mod
+++ b/modules/artifact-store-tools/go.mod
@@ -3,6 +3,7 @@ module artifactstoretools
 go 1.26.0
 
 require (
+	git.novox.be/novox/mesh-delivery/contracts/go/seats/meshartifactsweep v0.0.0-00010101000000-000000000000
 	git.novox.be/novox/mesh-contracts/placement/go/seats/meshwants v0.0.0-00010101000000-000000000000
 	git.novox.be/novox/mesh-contracts/go/seats/nodeengine v0.0.0-00010101000000-000000000000
 	git.novox.be/novox/mesh-contracts/go/clients/nodeengineclient v0.0.0-00010101000000-000000000000
@@ -22,6 +23,7 @@ require (
 require git.novox.be/novox/mesh-contracts/go v0.0.0-20261104174344-ae5266e77639 // indirect
 
 require (
+	git.novox.be/novox/mesh-delivery/contracts/go/seats/meshartifactsweep v0.0.0-00010101000000-000000000000
 	github.com/antithesishq/antithesis-sdk-go v0.8.0-default-no-op // indirect
 	github.com/google/go-tpm v0.9.8 // indirect
 	github.com/klauspost/compress v1.20.1 // indirect