diff --git a/go/catalogue/bus_snapshot_test.go b/go/catalogue/bus_snapshot_test.go
index 69bd737..789733f 100644
--- a/go/catalogue/bus_snapshot_test.go
+++ b/go/catalogue/bus_snapshot_test.go
@@ -43,4 +43,49 @@ func TestTheCataloguesBusIsBackedUpBySnapshot(t *testing.T) {
 	if !found {
 		t.Fatal("the bus declares no item for its streams")
 	}
+	// 774/S3 (ADR 0594 §7): the one list of what is the bus server names the bus's container and every resource that
+	// restarts it, read from the catalogue's nats manifest at mesh-catalog 0b2d393b; a module not providing the bus
+	// has none.
+	t.Run("the bus server's list", func(t *testing.T) {
+		raw, err := os.ReadFile("testdata/catalogue-0b2d393b-nats.module.json")
+		if err != nil {
+			t.Fatal(err)
+		}
+		nats, err := decodeForTest(raw)
+		if err != nil {
+			t.Fatal(err)
+		}
+		server := BusServerOf(nats)
+		var containers int
+		for _, r := range nats.Resources {
+			if r["type"] != "container" {
+				continue
+			}
+			containers++
+			restarts, _ := r["restart-on"].([]any)
+			if !server[r["id"].(string)] || len(restarts) == 0 {
+				t.Errorf("the bus's container %v (restarted on %v) is not all in the server's list %v", r["id"], restarts, server)
+			}
+			for _, id := range restarts {
+				if !server[id.(string)] {
+					t.Errorf("%v restarts the bus server and is not in its list %v", id, server)
+				}
+			}
+		}
+		if containers != 1 || len(server) != len(BusServer) {
+			t.Errorf("the bus has %d containers and its server is %v of %v", containers, server, BusServer)
+		}
+		xterm, err := os.ReadFile("testdata/catalogue-835bf22b-xterm.module.json")
+		if err != nil {
+			t.Fatal(err)
+		}
+		other, err := decodeForTest(xterm)
+		if err != nil {
+			t.Fatal(err)
+		}
+		other.Resources = append(other.Resources, map[string]any{"id": "server", "type": "container"})
+		if got := BusServerOf(other); len(got) != 0 {
+			t.Errorf("a module not providing the bus has a bus server %v", got)
+		}
+	})
 }
diff --git a/go/catalogue/testdata/catalogue-0b2d393b-nats.module.json b/go/catalogue/testdata/catalogue-0b2d393b-nats.module.json
new file mode 100644
index 0000000..01f3679
--- /dev/null
+++ b/go/catalogue/testdata/catalogue-0b2d393b-nats.module.json
@@ -0,0 +1,236 @@
+{
+  "module": "nats",
+  "version": "1",
+  "upgrade": {
+    "policy": "record",
+    "why": "the bus: replaced only as a planned step a person starts (`bus upgrade`), its streams snapshotted first and checked after (hq ADR 0236); the controller holds this whatever is said here"
+  },
+  "provides": [
+    {
+      "name": "mesh-bus",
+      "scope": "mesh",
+      "credential": {
+        "form": "none"
+      }
+    }
+  ],
+  "claims": [
+    {
+      "name": "mesh-broker",
+      "scope": "mesh"
+    }
+  ],
+  "bus-users": "/var/lib/nats-module/conf/accounts.conf",
+  "own-secrets": {
+    "broker": "${dir:mesh-state}/broker",
+    "broker-nats-tools": "${dir:tools-secret}/broker-nats-tools"
+  },
+  "capabilities": [
+    "container-runtime"
+  ],
+  "emits": [
+    "consumer-removed",
+    "bucket-keys-removed",
+    "stream-removed",
+    "bucket-expiry-set"
+  ],
+  "invokes": [
+    "seat:mesh-hand-acts.hand-act"
+  ],
+  "consumes": [],
+  "listens": [
+    {
+      "name": "bus",
+      "port": 4222,
+      "protocol": "tcp",
+      "from": "mesh",
+      "why": "the mesh bus — every link the mesh has, over TLS, reached across the overlay"
+    }
+  ],
+  "tools": [
+    "nats_server",
+    "nats_connections",
+    "nats_closed_connections",
+    "nats_subscriptions",
+    "nats_streams",
+    "nats_backlog",
+    "nats_buckets",
+    "nats_users",
+    "nats_user_can",
+    "nats_snapshot_verify",
+    "nats_consumer_remove",
+    "nats_bucket_remove",
+    "nats_stream_remove",
+    "nats_bucket_expiry"
+  ],
+  "guards": [
+    8222
+  ],
+  "data": {
+    "own": [
+      {
+        "id": "jetstream",
+        "path": "${dir:jetstream-data}",
+        "class": "valuable",
+        "active": "1d",
+        "backup": {
+          "dump": "docker exec -i mesh-broker-nats /opt/mesh/mesh-nats-snapshot snapshot < ${dir:mesh-state}/broker > ${dir:snapshots}/bus.tar.partial && mv ${dir:snapshots}/bus.tar.partial ${dir:snapshots}/bus.tar || { rm -f ${dir:snapshots}/bus.tar.partial; exit 1; }",
+          "into": "snapshots"
+        },
+        "why": "the bus's streams and key-value buckets: the hand-act log, conditions, every module's state; written all the time, so copied by the server's own snapshot of each stream (novox/hq ADR 0235), never as live files"
+      },
+      {
+        "id": "snapshots",
+        "path": "${dir:snapshots}",
+        "class": "rebuildable",
+        "why": "last night's snapshot of every stream with its manifest, made again every night"
+      }
+    ]
+  },
+  "resources": [
+    {
+      "id": "jetstream-data",
+      "type": "directory",
+      "path": "/var/lib/mesh-broker-nats",
+      "mode": "0700",
+      "unknown": "program"
+    },
+    {
+      "id": "conf-dir",
+      "type": "directory",
+      "path": "/var/lib/nats-module/conf",
+      "mode": "0700",
+      "unknown": "program"
+    },
+    {
+      "id": "tools-secret",
+      "type": "directory",
+      "path": "/var/lib/mesh/nats-tools",
+      "mode": "0711",
+      "unknown": "program"
+    },
+    {
+      "id": "snapshots",
+      "type": "directory",
+      "mode": "0700",
+      "unknown": "program"
+    },
+    {
+      "id": "mesh-state",
+      "type": "directory",
+      "mode": "0700",
+      "place": "mesh",
+      "unknown": "program"
+    },
+    {
+      "id": "server-conf",
+      "type": "file",
+      "path": "/var/lib/nats-module/conf/nats.conf",
+      "template": "files/nats.conf",
+      "mode": "0644"
+    },
+    {
+      "id": "state",
+      "type": "directory",
+      "mode": "0700",
+      "place": ".",
+      "unknown": "program"
+    },
+    {
+      "id": "program-snapshot",
+      "type": "archive",
+      "path": "${dir:state}/snapshot",
+      "artifact": "snapshot",
+      "unknown": "program"
+    },
+    {
+      "id": "program-entrypoint",
+      "type": "archive",
+      "path": "${dir:state}/entrypoint",
+      "artifact": "entrypoint",
+      "unknown": "program"
+    },
+    {
+      "id": "server",
+      "type": "container",
+      "name": "mesh-broker-nats",
+      "ports": [
+        "4222:4222",
+        "127.0.0.1:8222:8222"
+      ],
+      "volumes": [
+        "/var/lib/mesh-broker-nats:/data",
+        "/var/lib/nats-module/conf:/etc/nats:ro",
+        "${access:tls}:/tls:ro",
+        "${dir:state}/snapshot:/opt/mesh:ro",
+        "${dir:state}/entrypoint:/opt/mesh-entrypoint:ro"
+      ],
+      "args": [
+        "sh",
+        "/opt/mesh-entrypoint/entrypoint.sh"
+      ],
+      "artifact": "server",
+      "restart-on": [
+        "program-snapshot",
+        "program-entrypoint"
+      ]
+    }
+  ],
+  "accesses": [
+    {
+      "id": "tls",
+      "path": "/var/lib/mesh-broker-tls",
+      "mode": "read"
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "server",
+        "kind": "upstream",
+        "from": "nats:2.11.17-alpine@sha256:e4bf19f15fd3218814a4e3c9e0064e1334bd8aa20d5984b9f1a0afd084f8cc00"
+      },
+      {
+        "name": "snapshot",
+        "kind": "bundle",
+        "language": "go",
+        "system": "alpine",
+        "from": "cmd/mesh-nats-snapshot",
+        "binary": "mesh-nats-snapshot"
+      },
+      {
+        "name": "entrypoint",
+        "kind": "archive",
+        "from": "program"
+      },
+      {
+        "name": "tools",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/nats-tools",
+        "binary": "nats-tools",
+        "loads": [
+          "nats-tools"
+        ],
+        "bus": {
+          "removes": [
+            "controller-leftovers"
+          ]
+        },
+        "env": {
+          "MESH_NATS_MONITOR": "http://127.0.0.1:8222",
+          "MESH_NATS_CONTAINER": "mesh-broker-nats",
+          "MESH_NATS_USERS_FILE": "/etc/nats/accounts.conf",
+          "MESH_NATS_SNAPSHOTS_DIR": "${dir:snapshots}",
+          "NATS_TOOLS_CREDENTIAL": "${dir:tools-secret}/broker-nats-tools"
+        }
+      },
+      {
+        "name": "files",
+        "kind": "archive",
+        "from": "files"
+      }
+    ]
+  }
+}
diff --git a/go/catalogue/upgrade.go b/go/catalogue/upgrade.go
index a89e994..c22c5e1 100644
--- a/go/catalogue/upgrade.go
+++ b/go/catalogue/upgrade.go
@@ -2,6 +2,7 @@ package catalogue
 
 import (
 	"fmt"
+	"slices"
 	"strings"
 	"time"
 )
@@ -69,6 +70,26 @@ func ProvidesBus(m Manifest) bool {
 	return false
 }
 
+// BusServer names the resources of a module that provides the mesh's bus which are its server (novox/hq ADR 0594 §7):
+// the server's container and what restarts it. A node agent applying the bus module's want without the warrant's mark
+// leaves these as they run (§2), and the assigner says which resources wait for the warrant from this list; neither
+// keeps a copy of it. The ids are the catalogue's nats module's (modules/nats/module.json).
+var BusServer = []string{"server", "program-snapshot", "program-entrypoint"}
+
+// BusServerOf is the ids of BusServer that m declares as resources, empty unless m provides the mesh's bus.
+func BusServerOf(m Manifest) map[string]bool {
+	if !ProvidesBus(m) {
+		return nil
+	}
+	of := map[string]bool{}
+	for _, r := range m.Resources {
+		if id, _ := r["id"].(string); slices.Contains(BusServer, id) {
+			of[id] = true
+		}
+	}
+	return of
+}
+
 // irreplaceable names the first irreplaceable data the module keeps, its own or its consumers', or
 // nothing.
 func (m Manifest) irreplaceable() string {