diff --git a/src/main.ts b/src/main.ts
index 035ff6b..21f609f 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -22,7 +22,8 @@
 
 import { readFileSync } from "node:fs";
 import { pathToFileURL } from "node:url";
-import { connectAmqp, fatalBrokerReason } from "./broker-amqp.js";
+import { connectAmqp, fatalBrokerReason as fatalAmqpReason } from "./broker-amqp.js";
+import { connectNats, fatalBrokerReason as fatalNatsReason } from "./broker-nats.js";
 import type { Credential } from "./broker-amqp.js";
 import { runTools } from "./runtime.js";
 import { invokeTool } from "@novox/mesh-sdk/tools";
@@ -35,6 +36,12 @@ import { emit } from "@novox/mesh-sdk/events";
  * over the plain bootstrap URL otherwise. A scoped module assumes the foundation's exchanges exist —
  * its account may not declare them (ADR 0043).
  */
+// fatalBrokerReasonFor is the reason a connection failure is final rather than "not yet", for
+// whichever bus this runtime is on — each transport knows its own refusals.
+function fatalBrokerReasonFor(err: unknown): string | null {
+  return fatalNatsReason(err) ?? fatalAmqpReason(err);
+}
+
 async function connectBroker(): Promise<Broker> {
   const file = process.env.MESH_BROKER_FILE;
   if (file) {
@@ -54,6 +61,14 @@ async function connectBroker(): Promise<Broker> {
     // what the environment says.
     if (credential.node) process.env.MESH_NODE = credential.node;
     if (credential.module) process.env.MESH_MODULE = credential.module;
+    // **The credential names the bus.** A module moved to the bus being built was handed a
+    // credential for it — `nats://…` with user, password and fingerprint beside the address — and
+    // nothing else in its environment changed (design 25; novox/hq design 28 task 5.2). The scheme
+    // is enough to know which bus to speak; a runtime that always dialled the old one would keep
+    // serving and answer nobody.
+    if (credential.url.startsWith("nats://")) {
+      return connectNats(credential);
+    }
     return connectAmqp(credential, { assumeExchanges: true });
   }
   const url = process.env.MESH_BROKER_URL;
@@ -83,7 +98,7 @@ async function connectBrokerPatiently(): Promise<Broker> {
     try {
       return await connectBroker();
     } catch (err) {
-      const fatal = fatalBrokerReason(err);
+      const fatal = fatalBrokerReasonFor(err);
       if (fatal !== null) {
         console.error(`mesh-tools: ${fatal} — waiting will not fix this; giving up`);
         throw err;