diff --git a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/bridge_test.go b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/bridge_test.go
index b3e2c98b4..fb246c590 100644
--- a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/bridge_test.go
+++ b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/bridge_test.go
@@ -137,6 +137,17 @@ func (s *fakeSource) Move(update func(prev *Source) (Source, bool)) error {
 	return nil
 }
 
+// Read is source.main as held, and its revision: the number of writes.
+func (s *fakeSource) Read() (*Source, uint64, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.main == nil {
+		return nil, 0, nil
+	}
+	held := *s.main
+	return &held, uint64(len(s.moves)), nil
+}
+
 func sortStrings(s []string) { sort.Strings(s) }
 func itoa(n int) string      { return strconv.Itoa(n) }
 
diff --git a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/bus_test.go b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/bus_test.go
index 7eaeaa47d..a33421423 100644
--- a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/bus_test.go
+++ b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/bus_test.go
@@ -631,6 +631,11 @@ func TestAPassingVerdictAsksTheApproveAndItsApproveMergesWithinSecondsOverARealB
 		src, err := mdc.DecodeSource(e.Value())
 		return err == nil && src.Group == "fix/x" && src.Heads["novox/app"] == strings.Repeat("b", 40)
 	})
+	// The seat's verb source answers it from the bucket, with its revision on the bus.
+	said := strings.ReplaceAll(rt.call(t, Seat+".source", map[string]any{}), `\"`, `"`)
+	if !strings.Contains(said, `{"head":"`+strings.Repeat("b", 40)+`","repository":"novox/app","trunk":"main"}`) || !strings.Contains(said, `"revision":`) {
+		t.Fatalf("source answers %s", said)
+	}
 	// The delivery ends merged (ADR 0539 §17), and the gate asked the controller nothing (R6-C3).
 	rt.until("the delivery to be merged", eventWithin, func() bool {
 		e, err := b.kvs["deliveries"].Get(ctx, kvKey(IDOf("novox/app", head)))
diff --git a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/issue888_test.go b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/issue888_test.go
index 68cd6b853..ab6b42d94 100644
--- a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/issue888_test.go
+++ b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/issue888_test.go
@@ -5,6 +5,7 @@ import (
 	"time"
 
 	mdc "git.novox.be/novox/mesh-delivery/contracts/go/clients/meshdeliveryclient"
+	seat "git.novox.be/novox/mesh-delivery/contracts/go/seats/meshdelivery"
 )
 
 // Issue 888: the checker judges on the trunk source.main names (mesh-delivery modules/mesh-delivery-checker main.go), and the
@@ -38,6 +39,12 @@ func TestAMergeHeardOnlyFromTheForgeMovesSourceMain(t *testing.T) {
 	if w.source.main == nil || w.source.main.Heads[i888App] != i888Merge1 || w.source.main.Heads[i888Other] != i888OtherH {
 		t.Fatalf("source.main is %+v; wanted %s at %s and %s kept", w.source.main, i888App, i888Merge1, i888Other)
 	}
+	// The seat's verb source answers each repository's trunk branch and head, and the revision, from the same key.
+	if a := w.h.SourceRevision(); a.Error != "" || a.Revision != 1 || len(a.Repositories) != 2 ||
+		a.Repositories[0] != (seat.SourceHead{Repository: i888App, Trunk: MergeBranch, Head: i888Merge1}) ||
+		a.Repositories[1].Repository != i888Other || a.Repositories[1].Head != i888OtherH {
+		t.Fatalf("source answers %+v", a)
+	}
 	n := len(w.source.moves)
 	w.settleAll()
 	w.h.PullMerged(i888MergedAt(i888App, 3, i888Head1, i888Merge1, w.now.Add(-time.Minute))) // heard again
diff --git a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/main.go b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/main.go
index 50a28b098..f6841d265 100644
--- a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/main.go
+++ b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/main.go
@@ -354,6 +354,12 @@ func tools(h *Holder, l *listening) []stdio.Tool {
 			Input: map[string]any{"type": "object", "properties": map[string]any{
 				"all": map[string]any{"type": "string", "enum": []string{"true", "false"}}}},
 			Run: func(a map[string]any) (any, error) { return h.Groups(boolArg(a, "all")), nil }},
+		{Name: seat + "source",
+			Description: "The source revision the gate holds: every repository it names, its trunk branch and that trunk's head, the " +
+				"group that moved it last and its revision. Read, never written: a node-engine reads the repositories here to call a " +
+				"reverted build's catch-up tool once per repository, never the gate's state.",
+			Input: map[string]any{"type": "object", "properties": map[string]any{}},
+			Run:   func(map[string]any) (any, error) { return h.SourceRevision(), nil }},
 		{Name: seat + "checks",
 			Description: "What the mesh's checks said of a pull request's head or of one commit: each of the commit's " +
 				"statuses (mesh/check, mesh/delivery, …) with its state, description and when it " +
diff --git a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/manifest_test.go b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/manifest_test.go
index 28891258d..e61ec7458 100644
--- a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/manifest_test.go
+++ b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/manifest_test.go
@@ -75,7 +75,7 @@ func TestItClaimsTheDeliverySeatAndFollowsWhatItHandles(t *testing.T) {
 	}
 	// The eight verbs the seat keeps (ADR 0539 §17): times, what-if, release, stop and retire-history went with the plans; and
 	// settle, a person's ask to settle merges held without a passing check (ADR 0556 clause 5).
-	if want := []string{"deliveries", "show", "groups", "checks", "table", "stalled", "recheck", "close", "settle"}; !reflect.DeepEqual(m.Claims[0].Serves, want) {
+	if want := []string{"deliveries", "show", "groups", "source", "checks", "table", "stalled", "recheck", "close", "settle"}; !reflect.DeepEqual(m.Claims[0].Serves, want) {
 		t.Fatalf("serves %v, wanted %v", m.Claims[0].Serves, want)
 	}
 	// The forge messages' layout is the bridge's published package forgemsg, taken by its series (ADR 0634 §3, design 32).
diff --git a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/merges.go b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/merges.go
index 2cbf862af..1fd3797f7 100644
--- a/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/merges.go
+++ b/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/merges.go
@@ -11,6 +11,7 @@ import (
 	"time"
 
 	mdc "git.novox.be/novox/mesh-delivery/contracts/go/clients/meshdeliveryclient"
+	seat "git.novox.be/novox/mesh-delivery/contracts/go/seats/meshdelivery"
 	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-forge-bridge/forgemsg"
 	stdio "git.novox.be/novox/mesh-sdk/go"
 )
@@ -32,6 +33,8 @@ type SourceStore interface {
 	// Move reads source.main and writes what update makes of it, unless update says nothing is to be written; a write
 	// another writer won is read again and tried again.
 	Move(update func(prev *Source) (Source, bool)) error
+	// Read is source.main as held and its revision on the bus; nil and 0 before it is first written.
+	Read() (*Source, uint64, error)
 }
 
 // kvMerges is merges over the runtime.
@@ -107,6 +110,40 @@ func (kvSource) Move(update func(prev *Source) (Source, bool)) error {
 	return fmt.Errorf("source.main was written by another writer first %d times: %w", changeAttempts, stdio.ErrChanged)
 }
 
+func (kvSource) Read() (*Source, uint64, error) {
+	e, err := stdio.State("source").Get(mdc.SourceMainKey)
+	if err != nil || e == nil {
+		return nil, 0, err
+	}
+	held, err := mdc.DecodeSource(e.Value)
+	if err != nil {
+		return nil, 0, fmt.Errorf("source.main is not readable: %w", err)
+	}
+	return &held, e.Revision, nil
+}
+
+// SourceRevision is the seat's verb source: every repository source.main names, its trunk branch and head, the group that
+// moved it last and its revision, or why it cannot be read. source.main names each repository's main only (MergeBranch).
+// Outside the lock.
+func (h *Holder) SourceRevision() seat.SourceAnswer {
+	if h.Source == nil {
+		return seat.SourceAnswer{Error: "no source bucket"}
+	}
+	held, revision, err := h.Source.Read()
+	if err != nil {
+		return seat.SourceAnswer{Error: err.Error()}
+	}
+	if held == nil {
+		return seat.SourceAnswer{}
+	}
+	out := seat.SourceAnswer{Group: held.Group, Revision: int64(revision)}
+	for repository, head := range held.Heads {
+		out.Repositories = append(out.Repositories, seat.SourceHead{Repository: repository, Trunk: MergeBranch, Head: head})
+	}
+	sort.Slice(out.Repositories, func(i, j int) bool { return out.Repositories[i].Repository < out.Repositories[j].Repository })
+	return out
+}
+
 // SourceMain is source.main as the bucket source holds it, read and never written: its group and each repository's trunk
 // head, or why it cannot be read. Outside the lock.
 func (h *Holder) SourceMain() map[string]any {
diff --git a/modules/mesh-delivery-gate/module.json b/modules/mesh-delivery-gate/module.json
index 190578972..cf20565ca 100644
--- a/modules/mesh-delivery-gate/module.json
+++ b/modules/mesh-delivery-gate/module.json
@@ -10,6 +10,7 @@
         "deliveries",
         "show",
         "groups",
+        "source",
         "checks",
         "table",
         "stalled",