NWC: own the relay set instead of borrowing the sync feature's

The connection URI advertised up to four relays (sync relays + profile
relays) while the subscription only ever listened on the sync relay, so a
client could publish its request somewhere hal wasn't and spin forever
waiting for a reply. Amethyst did exactly that.

NWC now has its own relay list used for all three things that must agree:
the URI, the subscription, and the replies. It no longer depends on device
sync being enabled, which would otherwise have made the whole wallet service
a silent no-op.

Also republish the kind 13194 capability event on every start — a client that
can't find it just spins, and a single publish at creation time is easy for a
relay to miss.

The relay transport is now injectable so the protocol can be exercised
without a live relay (tools/nwc-test.js).

Co-Authored-By: Claude Fable 5 <[email protected]>

3 files changed, 39 insertions, 11 deletions

diff --git a/src/features/nwc.js b/src/features/nwc.js
index b582ed9..61bfc60 100644
--- a/src/features/nwc.js
+++ b/src/features/nwc.js
@@ -25,6 +25,7 @@ import { hex } from '@scure/base';
 import { sha256 } from '@noble/hashes/sha256';
 import {
   nip04, nip44, getPublicKey, finalizeEvent, generateSecretKey,
+  subscribeOn, publishOn,
 } from '../nostr.js';
 import { t } from '../i18n.js';
 import { qrSvg } from '../qr.js';
@@ -47,6 +48,9 @@ const errRes = (code, message) => ({ error: { code, message } });
 
 export function nwcFeature(ctx) {
   const { h, ui, render, wallet, hook, fmtAmount, unitLabel, copyBtn, toast } = ctx;
+  // Relay transport, injectable so the protocol can be driven in tests
+  // without a live relay.
+  const { subscribe = subscribeOn, publish = publishOn } = ctx.nwcTransport || {};
 
   // ---- persisted connections -------------------------------------------
   // { id, name, secret (client sk hex), clientPk, servicePk, serviceSk,
@@ -75,10 +79,11 @@ export function nwcFeature(ctx) {
     updateConn(c.id, { spentDate: today, spentToday: spent + sat, lastUsed: Date.now() });
   }
 
-  function relays() {
-    const r = wallet.nostrRelays ? wallet.nostrRelays() : [];
-    return r.length ? r.slice(0, 4) : ['wss://relay.coinos.io'];
-  }
+  // The relays advertised in the URI MUST be the ones we listen on, or a
+  // client will publish its request somewhere we aren't and wait forever.
+  // Deliberately independent of the device-sync relay setting.
+  const NWC_RELAYS = ['wss://relay.coinos.io', 'wss://relay.damus.io', 'wss://nos.lol'];
+  const relays = () => NWC_RELAYS;
 
   // The string the user pastes into another app.
   function uriFor(c) {
@@ -124,7 +129,7 @@ export function nwcFeature(ctx) {
       tags: [['p', c.clientPk], ['encryption', 'nip44_v2 nip04']],
       content: METHODS.join(' '),
     }, sk);
-    return wallet.nostrPublishSigned ? wallet.nostrPublishSigned(evt) : null;
+    return publish(NWC_RELAYS, evt);
   }
 
   const decrypt = (scheme, sk, pk, ct) => (scheme === 'nip44_v2'
@@ -146,7 +151,7 @@ export function nwcFeature(ctx) {
         tags: [['p', ev.pubkey], ['e', ev.id], ['encryption', scheme]],
         content,
       }, sk);
-      await wallet.nostrPublishSigned(evt);
+      await publish(NWC_RELAYS, evt);
     } catch (e) {
       console.warn('nwc: could not reply', e.message);
     }
@@ -262,15 +267,19 @@ export function nwcFeature(ctx) {
   }
   function listen() {
     stop();
-    if (!wallet.nostrSubscribe || wallet.watchOnly) return;
+    if (wallet.watchOnly) return;
     const list = conns();
     if (!list.length) return;
     for (const c of list) {
-      const un = wallet.nostrSubscribe(
+      unsubs.push(subscribe(
+        NWC_RELAYS,
         { kinds: [REQ_KIND], '#p': [c.servicePk], since: nowSec() - MAX_AGE_SEC },
         (ev) => { onRequest(c, ev).catch(() => {}); },
-      );
-      unsubs.push(un);
+      ));
+      // Republish the capability event on every start: a client that can't
+      // find kind 13194 just spins, and a single publish at creation time can
+      // easily have been missed by a relay.
+      publishInfo(c).catch(() => {});
     }
   }
 
diff --git a/src/nostr.js b/src/nostr.js
index 652c579..1a86499 100644
--- a/src/nostr.js
+++ b/src/nostr.js
@@ -23,6 +23,20 @@ import { base64urlnopad } from '@scure/base';
 // CLOSE-after-EOSE handshake) cleanly, so we never send on a half-closed socket.
 const pool = new SimplePool();
 
+// Subscribe / publish on an explicit relay set, independent of the sync
+// feature's configuration. NWC needs this: the relays it advertises in a
+// connection URI must be exactly the ones it listens on, or a client's
+// request lands somewhere the wallet isn't and it waits forever.
+export function subscribeOn(relays, filter, onEvent) {
+  try {
+    const sub = pool.subscribeMany(relays, [filter], { onevent: onEvent });
+    return () => { try { sub.close(); } catch {} };
+  } catch { return () => {}; }
+}
+export async function publishOn(relays, evt) {
+  try { await Promise.allSettled(pool.publish(relays, evt)); return true; } catch { return false; }
+}
+
 // --- locking a gift to a recipient's Nostr key ---------------------------
 // An npub or 64-hex nostr pubkey → hex, or null if it isn't one.
 // NIP-47 wallet services sign with their own per-connection key and must
diff --git a/tools/nwc-test.js b/tools/nwc-test.js
index e22c5d2..3df0f28 100644
--- a/tools/nwc-test.js
+++ b/tools/nwc-test.js
@@ -14,6 +14,11 @@ globalThis.localStorage = { getItem:k=>k in store?store[k]:null, setItem:(k,v)=>
 
 let subHandler = null;
 const published = [];
+// fake relay transport: capture the subscription handler and any replies
+const nwcTransport = {
+  subscribe: (relays, filter, on) => { subHandler = on; return () => { subHandler = null; }; },
+  publish: async (relays, evt) => { published.push(evt); return true; },
+};
 let paid = [];
 const wallet = {
   watchOnly: false,
@@ -31,7 +36,7 @@ const hooks = {
   arkMovements: () => ([{ type:'ln-send', status:'complete', amountSat: 25, ts: Date.now(), invoice:'lnbc250n1', preimage:'ef'.repeat(32) }]),
 };
 const ctx = { h:()=>null, ui:{}, render:()=>{}, wallet, hook:(n,...a)=>hooks[n]?hooks[n](...a):null,
-  fmtAmount:(n)=>String(n), unitLabel:()=>'sats', copyBtn:()=>null, toast:()=>{} };
+  fmtAmount:(n)=>String(n), unitLabel:()=>'sats', copyBtn:()=>null, toast:()=>{}, nwcTransport };
 
 const f = nwcFeature(ctx);
 f.init();