A zap answered over NWC waits on far fewer round trips, and a phone with Coinos behind another app answers from its worker. "I'm on V3 … I find nwc zaps a lot more slower than usual" (398ja, 2026-11-10). Measured from the notifier's wakes and the ASP's log over four days: a closed app took about six seconds from the push to its cosign (the Lightning part after that is one and a half), an Android phone fifteen at the median, up to thirty. Where it went: every call to the ASP and the notifier was two round trips (no Access-Control-Max-Age, so Chrome re-asked the CORS preflight after five seconds; a Cloudflare response-header rule now sets 7200 on OPTIONS for ark.coinos.io, ark-staging and nwcpush), and the worker made them one after another: answered?, GetArkInfo, Handshake, claim, a save, the chain tip, then the payment, then status ("pending"), the tip again, the held status call, and status once more for the preimage it had just been handed. Now: what the mirror alone decides (invoice, network, budgets, coins, keys) comes first with no network; the claim (which now also says "already answered", coinosv3-server 3c5e9c3) goes out beside the manager's start, whose info call, handshake and tip run together (init, warmTip/_tipFresh); a send just initiated returns to its caller instead of asking at once, and awaitLnPay settles from the held call's own answer. A worker-style send on regtest: eight calls, six in sequence, where there were thirteen. The app's own answer no longer waits a second on a phone that is on screen (only one behind another app holds back for a computer).

Android freezes an app behind another one, and the worker's nudge to it sat unread until it was opened: on a phone the worker now hands a request only to a window on screen (as it already did on iOS), nudges a hidden one in case it is awake, and answers itself; the request's lock decides between them. For that the mirror is no longer written over the worker's hand: the worker stamps its writes (workerAt), the app writes under the worker's own lock (nwc-bg-work) and folds the worker's state in first (never mid-payment), carries the stamp, absorbs it when it comes back on screen (arkBgAbsorb), and refreshes the mirror as it goes behind another app.
Tests: ln-pay-double-wake (the one held call settles; a failed or mismatched answer doesn't), sw-push-quota (an Android phone's hidden window), nwc-sw-test's notifier stand-in answers /claim as the real one; tools/ark/ln-e2e-test's pay half against regtest captaind 0.8 + CLN

Co-Authored-By: Claude Fable 5.2 <[email protected]>

1 files changed, 12 insertions, 2 deletions

diff --git a/src/features/nwc.js b/src/features/nwc.js
index dc87388..9768740 100644
--- a/src/features/nwc.js
+++ b/src/features/nwc.js
@@ -388,7 +388,10 @@ export function nwcFeature(ctx) {
         return !!(prior && prior.length);
       };
       if (age > 5 && await lookBack()) return dlog('nwc: skip — request already answered elsewhere', ev.id.slice(0, 8));
-      if (mobile && age <= 5) await new Promise((r) => setTimeout(r, 1000));
+      // (a phone with this app on screen is as awake as any computer: only
+      // one behind another app holds back — every zap answered by an open
+      // phone used to wait this second for nobody)
+      if (mobile && age <= 5 && typeof document !== 'undefined' && document.hidden) await new Promise((r) => setTimeout(r, 1000));
       claimed = await claim(ev.id);
       if (claimed === false) return dlog('nwc: standing down — another device claimed', ev.id.slice(0, 8));
       if (claimed === null && age <= 5) {
@@ -981,7 +984,14 @@ export function nwcFeature(ctx) {
     if (typeof window !== 'undefined') {
       window.addEventListener('online', () => listen());
       document.addEventListener('visibilitychange', () => {
-        if (document.visibilityState === 'visible' && conns().length) { listen(); refreshRegistration(); }
+        if (document.visibilityState === 'visible' && conns().length) {
+          listen(); refreshRegistration();
+          // the worker may have paid while this app sat behind another one
+          Promise.resolve(hook('arkBgAbsorb')).then((had) => { if (had) return reconcileBg(); }).catch(() => {});
+        }
+        // going behind another app: the worker answers from the mirror now, so
+        // it gets this moment's coins, not the last minute-and-a-half's
+        if (document.visibilityState === 'hidden' && conns().length) writeBg();
       });
     }
   }