diff --git a/src/lib/hermes-derive.js b/src/lib/hermes-derive.js
new file mode 100644
index 0000000..345374d
--- /dev/null
+++ b/src/lib/hermes-derive.js
@@ -0,0 +1,42 @@
+// Self-contained Nostr-key derivation from a BIP-39 mnemonic.
+//
+// This mirrors TheseusNavigator/lib/hermes.js's nostrKeyFromMnemonic — same
+// HKDF context (info="silentmode/messenger/0"), same 32-byte output — but uses
+// libauth for the secp256k1 pubkey so it can run alongside the registrar
+// (Argus) without pulling in nostr-tools. Keep the derivation constants in
+// lockstep with TheseusNavigator/lib/hermes.js.
+
+import { webcrypto as wc } from "node:crypto";
+import { secp256k1, binToHex, hexToBin } from "@bitauth/libauth";
+
+const enc = new TextEncoder();
+
+export async function bip39ToSeed(mnemonic, passphrase = "") {
+  const km = await wc.subtle.importKey("raw",
+    enc.encode(String(mnemonic).normalize("NFKD").trim()),
+    "PBKDF2", false, ["deriveBits"]);
+  const salt = enc.encode(("mnemonic" + String(passphrase || "")).normalize("NFKD"));
+  return new Uint8Array(await wc.subtle.deriveBits(
+    { name: "PBKDF2", salt, iterations: 2048, hash: "SHA-512" }, km, 512));
+}
+
+export async function seedToPurposeRoot(seedBytes, purpose) {
+  const key = await wc.subtle.importKey("raw", seedBytes, "HKDF", false, ["deriveBits"]);
+  const info = enc.encode(`silentmode/${purpose}`);
+  return new Uint8Array(await wc.subtle.deriveBits(
+    { name: "HKDF", hash: "SHA-256", salt: new Uint8Array(0), info }, key, 256));
+}
+
+/** Mnemonic → { skHex, pkHex } where pkHex is the 32-byte x-only Nostr pubkey.
+ *  For a given mnemonic this must equal TheseusNavigator/lib/hermes.js's
+ *  nostrKeyFromMnemonic result — verified via Hermes/proof cross-check. */
+export async function nostrKeyFromMnemonic(mnemonic, passphrase = "") {
+  const seed = await bip39ToSeed(mnemonic, passphrase);
+  const sk = await seedToPurposeRoot(seed, "messenger/0");
+  const compressed = secp256k1.derivePublicKeyCompressed(sk);
+  if (typeof compressed === "string") throw new Error("secp256k1: " + compressed);
+  // Compressed pubkey is 33 bytes: [parity(0x02|0x03), x(32 bytes)]. Nostr's
+  // x-only is just the x coordinate.
+  const xonly = compressed.slice(1);
+  return { skHex: binToHex(sk), pkHex: binToHex(xonly) };
+}
diff --git a/src/register-hermes-chipnet.mjs b/src/register-hermes-chipnet.mjs
new file mode 100644
index 0000000..02fe8a1
--- /dev/null
+++ b/src/register-hermes-chipnet.mjs
@@ -0,0 +1,42 @@
+// One-off: register (or update) a chipnet .bch name whose `np` record binds
+// the name to the Nostr identity derived from the same wallet seed. Publishes
+// `nr` too so send-by-name has a relay to publish to.
+//
+//   node src/register-hermes-chipnet.mjs                       # defaults: hermes / wss://nos.lol
+//   node src/register-hermes-chipnet.mjs hermes-test wss://nos.lol,wss://relay.damus.io
+//
+// If the name is already registered it emits a UPD instead of a REG so it can
+// be re-run safely to rotate the np or nr.
+
+import { loadWallet } from "./lib/wallet.js";
+import { buildIndex, registerName, updateName } from "./lib/bns.js";
+import { nostrKeyFromMnemonic } from "./lib/hermes-derive.js";
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import { WALLET_FILE } from "./config.js";
+
+const [nameArg, nrArg] = process.argv.slice(2);
+const name = (nameArg || "hermes").toLowerCase();
+const nr = nrArg || "wss://nos.lol";
+
+const walletStore = JSON.parse(readFileSync(fileURLToPath(WALLET_FILE), "utf8"));
+const mnemonic = walletStore.main.seed;
+
+const { pkHex } = await nostrKeyFromMnemonic(mnemonic);
+console.log(`wallet nostr pubkey (np): ${pkHex}`);
+console.log(`relays (nr):              ${nr}`);
+console.log(`target name:              ${name}.bch`);
+
+const wallet = await loadWallet();
+console.log(`from wallet:              ${wallet.cashaddr}`);
+
+const idx = await buildIndex(wallet.provider);
+const exists = idx.has(name + ".bch") || idx.has(name);
+
+const records = { np: pkHex, nr };
+console.log(`operation:                ${exists ? "UPD" : "REG"}`);
+
+const fn = exists ? updateName : registerName;
+const res = await fn(wallet, name, records);
+console.log("result:", JSON.stringify(res, null, 2));
+process.exit(0);