The 200ms of secp256k1 hiding in every repaint: the depth advisory priced a full uncooperative exit — every hop of every coin, an EC tweak per hop — on each wallet render; the estimate now memoizes on coin set + feerate, and decoded vtxos cache by id (bytes are immutable). Profiled on a real phone: point add/double/wNAF was 1.3s of a 4.3s six-tab-switch trace

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01MrkLsNScXe9b6BviUSdmMr

2 files changed, 21 insertions, 2 deletions

diff --git a/src/ark/manager.js b/src/ark/manager.js
index 9731dd6..a190480 100644
--- a/src/ark/manager.js
+++ b/src/ark/manager.js
@@ -187,7 +187,16 @@ export class ArkManager {
     });
     return true;
   }
-  _decoded(v) { return decodeVtxo(hex.decode(v.bytes)); }
+  _decoded(v) {
+    // vtxo bytes are immutable per id — parse once. The depth advisory and
+    // fee estimates decode every coin on every render without this.
+    const hit = this._decodeCache && this._decodeCache.get(v.id);
+    if (hit) return hit;
+    const d = decodeVtxo(hex.decode(v.bytes));
+    (this._decodeCache ||= new Map()).set(v.id, d);
+    if (this._decodeCache.size > 200) this._decodeCache.delete(this._decodeCache.keys().next().value);
+    return d;
+  }
 
   // ---- chain adapter (esplora REST, same API the wallet already speaks) ----
   //
diff --git a/src/features/ark.js b/src/features/ark.js
index 72624b4..140eeb0 100644
--- a/src/features/ark.js
+++ b/src/features/ark.js
@@ -1929,16 +1929,26 @@ export function arkFeature(ctx) {
   // What a unilateral exit will need from Savings, BEFORE it starts: every
   // chain hop is a zero-fee tx bumped by a ~130 vB CPFP child, plus the
   // final claim. Priced at today's feerate — the driver reprices per hop.
+  // Memoized on the coin set + feerate: signedExitTxs rebuilds every hop of
+  // every coin's exit chain with an elliptic-curve tweak per hop — profiled
+  // at ~200ms of secp256k1 per call on a phone with depth-13 coins — and
+  // the depth advisory asked for it on EVERY wallet render. Same coins at
+  // the same feerate price the same, so pay once per change instead.
+  let _exitFeeMemo = { key: null, val: 0 };
   function estimateExitFeeSat(mgr) {
     const feeRate = Math.max(1, (wallet.feeRates && wallet.feeRates.halfHourFee) || 2);
+    const coins = mgr.vtxos().filter((x) => x.state === 'spendable');
+    const key = feeRate + '|' + coins.map((v) => v.id).join(',');
+    if (_exitFeeMemo.key === key) return _exitFeeMemo.val;
     let total = 0;
-    for (const v of mgr.vtxos().filter((x) => x.state === 'spendable')) {
+    for (const v of coins) {
       try {
         for (const txi of signedExitTxs(mgr._decoded(v), mgr.serverPub))
           total += Math.ceil((txi.vsize + 130) * feeRate);
         total += Math.ceil(150 * feeRate); // the claim tx
       } catch {}
     }
+    _exitFeeMemo = { key, val: total };
     return total;
   }