Merge pull request 'The runtime hears on its own inbox' (#17) from fix/the-runtime-hears-on-its-own-inbox into main

Every user's inbox is private to it and the grant names it; a reply space the client invented was
refused, and with it every pull for the next message and every answer to a tool call.

src/broker-nats.ts

@@ -19,7 +19,7 @@
 import { createHash } from "node:crypto";
 import net from "node:net";
 import tls from "node:tls";
-import { connect as natsConnect, headers as natsHeaders, StringCodec, type JsMsg, type Subscription } from "nats";
+import { connect as natsConnect, headers as natsHeaders, StringCodec, type JsMsg, type Subscription, type TlsOptions } from "nats";
 import type { Broker, Envelope, EventHeaders } from "@novox/mesh-sdk/messaging";
 
 const sc = StringCodec();
@@ -85,6 +85,10 @@ export async function connectNats(
     pass: cred.password,
     name: `${cred.node ?? "?"}.${self}`,
     tls: cred.fingerprint ? await pinnedTls(cred.url, cred.fingerprint) : undefined,
+    // Its own inbox, not a random one: every user's inbox is private to it (design 25 §4), and the
+    // grant names `_INBOX.<user>.>` — a reply space the client invented would be refused, and with
+    // it every pull for the next message and every answer to a tool call.
+    inboxPrefix: cred.user ? `_INBOX.${cred.user}` : undefined,
     // Reconnect forever: the bus being restarted is an upgrade, not a reason for every module on
     // the mesh to exit. `close()` stays the only thing that ends the connection.
     maxReconnectAttempts: -1,
@@ -298,14 +302,15 @@ function normalizeFingerprint(fingerprint: string): string {
  * A certificate authority is not consulted: the mesh issued this and knows its fingerprint,
  * which is stronger than trusting whoever a machine's trust store happens to contain.
  *
- * **A constraint on the mesh, not a detail of this file.** Pinning the exact certificate makes
- * hostname verification redundant in principle, but the NATS client exposes no hook to replace
- * it — its TLS options are file paths and PEM strings, with no verify callback. So the
- * certificate the mesh issues the bus **must carry a subject-alternative name matching the
- * address nodes dial it by**. The fingerprint check below still happens and is still the real
- * guarantee; what cannot be switched off is the check *beside* it.
+ * **The pin is the only check.** What comes back is handed to the client as its TLS options, and
+ * the client's transport spreads them into Node's own `tls.connect` — so the pinned certificate
+ * is the one authority the handshake accepts, and the hostname check beside it is replaced with
+ * one that always passes. Pinning the exact certificate makes verifying its name redundant, and
+ * the bus's certificate names the seat (`mesh-broker`), not the address a machine happens to
+ * dial it by: every module on the mesh met "does not match certificate's altnames" the first time
+ * it reached the handshake (2026-09-28).
  */
-async function pinnedTls(rawUrl: string, fingerprint: string): Promise<{ ca: string }> {
+async function pinnedTls(rawUrl: string, fingerprint: string): Promise<TlsOptions> {
   const url = new URL(rawUrl.includes("://") ? rawUrl : `nats://${rawUrl}`);
   const port = url.port ? Number(url.port) : 4222;
   // **The bus speaks first, in the clear.** A NATS server sends its INFO line before TLS begins,
@@ -342,7 +347,9 @@ async function pinnedTls(rawUrl: string, fingerprint: string): Promise<{ ca: str
     );
   }
   const pem = `-----BEGIN CERTIFICATE-----\n${certificate.raw.toString("base64").replace(/(.{64})/g, "$1\n")}\n-----END CERTIFICATE-----\n`;
-  return { ca: pem };
+  // Node's option, not the client's: the transport passes the whole object on. `undefined` from
+  // checkServerIdentity is "the name is fine"; the pin above already decided the rest.
+  return { ca: pem, checkServerIdentity: () => undefined } as TlsOptions;
 }
 
 /** The mesh's topic matching: `*` is one token, `#` the rest. This is the module's vocabulary —