ln/lightning: watchdog recycles zombie receive-listener socket

On 2026-06-04 cl restarted (autoheal, after its 15s healthcheck timed out),
and the app's waitanyinvoice long-poll hung on the now-dead listen socket.
listenerActive stayed true forever, so ensureListenerAlive never restarted
it, and incoming lightning payments stopped crediting for ~2h until a manual
app restart. The per-call RPC timeout in ln.ts can't catch this: waitanyinvoice
is intentionally in NO_TIMEOUT (it's meant to block).

Fix: ensureListenerAlive (runs every 120s) now also detects a stalled listener
— active but blocked in waitanyinvoice for >5min. It probes cl via the main
ln socket (getinfo); only if cl is actually alive does it treat the listen
socket as a zombie, call lnListen.reset() (new: drops the proxy's socket so the
next call reconnects), and re-arm. A listenerEpoch guard makes the wedged
invocation bow out when its waitanyinvoice finally rejects, so we never run two
listeners concurrently and never double-credit. Verified with a state-machine
test covering normal receive, quiet-but-healthy (left alone), stall+cl-alive
(recycled), stall+cl-down (left alone), and the no-double-listener race.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

1 files changed, 16 insertions, 0 deletions

diff --git a/lib/ln.ts b/lib/ln.ts
index de01ea81..4215731e 100644
--- a/lib/ln.ts
+++ b/lib/ln.ts
@@ -144,6 +144,22 @@ function lightningProxy(rpcPath: string) {
         if (prop === "toString") return () => "[LightningProxy]";
         if (prop === Symbol.toStringTag) return "LightningProxy";
 
+        // Force the underlying socket to be dropped so the next call reconnects.
+        // Used by the lightning-listener watchdog to recover a zombie long-poll
+        // (waitanyinvoice blocked on a dead socket while cl is actually alive —
+        // the per-call timeout can't catch it because long-polls are exempt).
+        if (prop === "reset") {
+          return () => {
+            const had = !!client;
+            try {
+              client?.removeAllListeners?.();
+              client?.destroy?.();
+            } catch (_) {}
+            client = null;
+            return had;
+          };
+        }
+
         return async (...args: any[]) => {
           const c = ensure();
           const v = c[prop as any];