A wallet that renews its own coins (Settings → Spending: self or exit) pays a Lightning invoice from the coins nearest expiry first, so fewer of them come up for a paid renewal (Stacker News request, 2026-10-29). Lightning sends only: the ASP takes those coins, whereas an Ark-to-Ark send would hand the recipient your short timelocks. The custodial default keeps the smallest coin that covers the payment (expiry costs nothing there), a coin past its timelock still goes last, and a pile of old crumbs that would breach the input cap falls back to largest-first. The closed-app NWC worker follows the mirrored tier the same way

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01VMan6VLgQdujavxPsfU7A9

1 files changed, 21 insertions, 0 deletions

diff --git a/tools/ark/custody-test.js b/tools/ark/custody-test.js
index 214ab45..68e7191 100644
--- a/tools/ark/custody-test.js
+++ b/tools/ark/custody-test.js
@@ -127,4 +127,25 @@ const coin = (id, amountSat, expiryHeight, extra = {}) => ({ id, amountSat, expi
   console.log('✓ deep coins: no base fee for a refresh of deep coins alone, a capped coin is never spent, the worker orders them flattened');
 }
 
+// Lightning sends: a wallet that renews its own coins spends the nearest
+// expiry first; the custodial default keeps the smallest coin that covers it
+{
+  const m = mk(true);
+  m.info.lnSendFees = { baseFeeSat: 0, minFeeSat: 0, ppmExpiryTable: [] };
+  m.state.vtxos = [coin('young', 3000, 2000), coin('old', 9000, 1100), coin('older', 2000, 1050), coin('past', 8000, 900)];
+  const ids = (amt) => m._selectLnInputs(m.state.vtxos, 1000, amt, 0).inputs.map((v) => v.id);
+  assert.deepEqual(ids(2500), ['young'], 'custodial: the smallest coin that covers it');
+  assert.deepEqual(ids(12000), ['old', 'young'], 'custodial: largest first');
+  m.lnOldestFirst = () => true;
+  assert.deepEqual(ids(1500), ['older'], 'self: the nearest expiry that covers it');
+  assert.deepEqual(ids(2500), ['old'], '…skipping one too small');
+  assert.deepEqual(ids(10000), ['older', 'old'], 'self: gathers nearest expiry first');
+  assert.deepEqual(ids(13000), ['older', 'old', 'young'], 'coins inside their timelock carry it alone when they can');
+  // a pile of old crumbs that would breach the input cap: largest-first instead
+  m.state.vtxos = [...Array.from({ length: MAX_SEND_INPUTS + 2 }, (_, i) => coin('crumb' + i, 100, 1010)), coin('big', 6000, 3000)];
+  assert.deepEqual(ids(6050).slice(0, 1), ['big'], 'too many old crumbs for one payment: largest first');
+  assert.equal(ids(6050).length, 2);
+  console.log('✓ Lightning sends: nearest expiry first when renewing your own coins, smallest-that-covers otherwise');
+}
+
 console.log('\n✅ custody tiers behave');