The node composes again only when what it composes from changed, so a want, placement, module or value written again asks the vault nothing (issue 774)

Every put under want.<node>.>, every module's take-in and every placement write
made a pass, and each pass asked the vault for the node's own secrets. The
shadow's change check moves onto the composer, gains the want (by its
fingerprint, the only part composed) and serves both loops.

internal/selfcompose/selfcompose_test.go

@@ -546,6 +546,40 @@ func TestTheNodeComposesItsWantsFromTheBus(t *testing.T) {
 			t.Errorf("%s: a pass made %v, want %v", row.name, got, row.pass)
 		}
 	}
+	// Issue 774, 2026-10-31: every put under want.n1.> made a pass, and each pass asked the vault for the node's own
+	// secrets. A key written again with what it held, or a want whose words moved and not its build, makes none.
+	worded, _ := delivery.EncodeWant(delivery.Want{FP: fp, Self: true, Words: "lemurs is held at aaaaaaaaaaaa"})
+	elsewhere, _ := delivery.EncodeWant(delivery.Want{FP: delivery.SourcePrefix2 + strings.Repeat("e", 64), Self: true})
+	for _, row := range []struct {
+		name, bucket, key string
+		value             []byte
+		pass              bool
+	}{
+		{"lemurs's want again", delivery.AssignerWantsBucket, "want.n1.lemurs", want, false},
+		{"the node's own want again", delivery.AssignerWantsBucket, "want.n1.node", nodeWant, false},
+		{"lemurs's want with other words", delivery.AssignerWantsBucket, "want.n1.lemurs", worded, false},
+		{"the placement again", delivery.PlacementBucket, "placement.n1", place, false},
+		{"lemurs's module again", delivery.ModulesBucket, "lemurs", mod, false},
+		{"lemurs's want at another build", delivery.AssignerWantsBucket, "want.n1.lemurs", elsewhere, true},
+		{"lemurs's want back at its build", delivery.AssignerWantsBucket, "want.n1.lemurs", want, true},
+	} {
+		before := passes()
+		b.put(t, row.bucket, row.key, row.value)
+		if !row.pass {
+			quiet(t, out)
+		} else {
+			for done := false; !done; {
+				select {
+				case <-out:
+				case <-time.After(200 * time.Millisecond):
+					done = true
+				}
+			}
+		}
+		if got := passes() > before; got != row.pass {
+			t.Errorf("%s: a pass made %v, want %v", row.name, got, row.pass)
+		}
+	}
 	// And today's sequence whole: tool runs at its old build; its want and the trunk move to a build not yet done, and
 	// the node holds tool, keeping what runs, naming why; the build lands, and with no other change tool is handed at it.
 	{
@@ -629,7 +663,7 @@ func TestTheNodeComposesItsWantsFromTheBus(t *testing.T) {
 	b.mu.Lock()
 	n := 0
 	for _, s := range b.said {
-		if strings.Contains(s, "lemurs is wanted at") {
+		if strings.Contains(s, "lemurs is wanted at "+gone) {
 			n++
 		}
 	}