Ark key derivation gets memoized — the boot CPU hog. A profile of the first 9s after refresh showed ~800ms of secp256k1 (q0/mul/TJ) dominating the main thread; the source was _key(index) recomputing a BIP32 derive + a getPublicKey point-mul on every call, and reconcile() calls it for every spendable coin (56 here), with decode/send/exit/fee-math hitting it again. A key for an index is constant per wallet, so it's cached by index now (mailbox key too) — dozens of EC muls per boot collapse to one each

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

1 files changed, 13 insertions, 2 deletions

diff --git a/src/ark/manager.js b/src/ark/manager.js
index 59f9f09..4e9a62c 100644
--- a/src/ark/manager.js
+++ b/src/ark/manager.js
@@ -82,16 +82,27 @@ export class ArkManager {
     this.state = null;
     this.info = null;
     this._lnDriving = new Set(); // re-entrancy guard: sync poll vs UI fast-poll vs mailbox push
+    // A derived key for an index never changes for this wallet, but computing
+    // it costs a BIP32 derive + a secp256k1 getPublicKey (a full point mul).
+    // reconcile() alone calls _keyForVtxo for every spendable coin, and decode/
+    // send/exit/fee-math hit it again — dozens of EC muls per boot burst, the
+    // dominant main-thread cost in a CPU profile. Memoize by index.
+    this._keyCache = new Map();
   }
 
   // ---- keys ----
   _key(index) {
+    let k = this._keyCache.get(index);
+    if (k) return k;
     const node = this.account.deriveChild(3).deriveChild(index);
-    return { privkey: node.privateKey, pubkey: secp256k1.getPublicKey(node.privateKey, true) };
+    k = { privkey: node.privateKey, pubkey: secp256k1.getPublicKey(node.privateKey, true) };
+    this._keyCache.set(index, k);
+    return k;
   }
   _mailboxKey() {
+    if (this._mbKey) return this._mbKey;
     const node = this.account.deriveChild(4).deriveChild(0);
-    return { privkey: node.privateKey, pubkey: secp256k1.getPublicKey(node.privateKey, true) };
+    return (this._mbKey = { privkey: node.privateKey, pubkey: secp256k1.getPublicKey(node.privateKey, true) });
   }
   _keyForVtxo(v) { return this._key(v.keyIndex); }