Features phase 2: gift/swap/ark primitives leave the core wallet

wallet.js drops from 2,762 to 2,374 lines and now exposes two generic
seams instead of feature code:
- registerCoinLock()/lockedCoinIds(): features contribute coin ids that
  spending and the balance treat as unavailable (gift reservations).
- loadFeatureState()/saveFeatureState(): namespaced per-wallet persisted
  state.

src/features/gifts-wallet.js takes the whole gift engine — reservation
sets, gift records, coin selection, the SIGHASH_SINGLE/NONE PSBT
builder, the compact codec, claim building, nostr-locked gifts — as an
installGiftWallet(wallet) instance install plus standalone exports.
Swap storage/key helpers (loadSwaps/saveSwaps/swapNode/nextSwapIndex)
install from swap.js; ark state storage installs from the ark feature.
The silent-payment scan worker only embeds when the sp feature ships
(wallet.js already tolerated its absence).

Minimal profile: 412KB, down from 476KB (full: 578KB). All suites pass:
ark UI e2e, ArkManager crash-resume, gift lifecycle, minimal smoke.

SP's engine (scanning, BIP-352 signing) stays in wallet.js — extracting
it safely wants an SP e2e harness on this stack first.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01QFAcD4V284DvYZZHP7Rxxy

1 files changed, 24 insertions, 426 deletions

diff --git a/src/wallet.js b/src/wallet.js
index 56e3726..403bcd8 100644
--- a/src/wallet.js
+++ b/src/wallet.js
@@ -23,7 +23,7 @@ import { concatBytes } from '@scure/btc-signer/utils.js';
 
 import { Api, pool, getBackend, explorerWeb, electrumCandidates, spIndexerUrl } from './api.js';
 import { ElectrumApi } from './electrum.js';
-import { NostrSync, getSyncConfig, encryptGiftPayload, npubOf } from './nostr.js';
+import { NostrSync, getSyncConfig, npubOf } from './nostr.js';
 import { isSilentPaymentAddress, decodeSilentPaymentAddress, silentPaymentScripts, silentPaymentPlaceholder, deriveSilentPaymentKeys, encodeSilentPaymentAddress, silentPaymentScan, silentPaymentOutputPrivKey, silentPaymentCandidate, bloomHas } from './silentpay.js';
 import { schnorr } from '@noble/curves/secp256k1';
 
@@ -105,6 +105,9 @@ export class Wallet {
     this.mnemonic = '';
     this.passphrase = '';
     this.netName = 'mainnet';
+    // Feature-registered providers of coin ids to exclude from spending and
+    // the spendable balance (e.g. coins reserved behind unclaimed gift links).
+    this._coinLocks = [];
 
     this.api = new Api('mainnet');
     this.offline = false;
@@ -1134,20 +1137,12 @@ export class Wallet {
     return this.confirmed + this.pending;
   }
 
-  // Confirmed coins locked behind unclaimed gift links. The whole source coin is
-  // committed until the gift is claimed (our change only comes back in the
-  // claimer's tx), so it's already excluded from spending — and from the
-  // spendable balance below.
-  get lockedValue() {
-    const res = this.reservedSet();
-    return this.utxos.reduce((s, u) => s + (res.has(utxoId(u)) ? u.value : 0), 0);
-  }
   // The spendable headline: confirmed coins plus our own unconfirmed change (the
   // remainder of a spend we just made, so the spend debits immediately), minus
   // anything locked in gifts. Unconfirmed *incoming* receives are NOT counted
   // here — they show as pending until they confirm.
   get spendable() {
-    const res = this.reservedSet();
+    const res = this.lockedCoinIds();
     return this.utxos.reduce((s, u) => {
       if (res.has(utxoId(u))) return s;
       if (u.confirmed || u.chain === 1) return s + u.value;
@@ -1158,7 +1153,7 @@ export class Wallet {
   // separate pending line, kept out of the spendable headline. Includes pending
   // (mempool) silent-payment receipts.
   get pendingIncoming() {
-    const res = this.reservedSet();
+    const res = this.lockedCoinIds();
     return this.utxos.reduce((s, u) => s + ((!u.confirmed && u.chain === 0 && !res.has(utxoId(u))) ? u.value : 0), 0) + this.spBalance().pending;
   }
 
@@ -1194,7 +1189,7 @@ export class Wallet {
   buildTx({ recipients, feeRate, coinIds = null, sendMax = false, noSort = false }) {
     const pool_ = coinIds
       ? this.utxos.filter((u) => coinIds.includes(utxoId(u)))
-      : this.utxos.filter((u) => !this.isReserved(utxoId(u))); // skip coins set aside for gifts
+      : (() => { const locked = this.lockedCoinIds(); return this.utxos.filter((u) => !locked.has(utxoId(u))); })(); // skip locked coins (gift reservations, ...)
     // Received silent-payment outputs are spendable too — one-time taproot keys,
     // signed by sign() with the per-output key. Excluded when paying an sp1…
     // recipient (funding an SP send from a taproot input needs BIP-352 even-Y
@@ -1501,16 +1496,6 @@ export class Wallet {
     return { hex: t.hex, txid: t.id, fee: pl.fee, oldFee: prep.oldFee, feeRate: pl.rate, outputs, replaces: prep.txid };
   }
 
-  // --- gift links (coins backing claimable presigned transactions) ---------
-  // A gift coin is either RESERVED (set aside, skipped by coin selection) or
-  // RECLAIMED (freed for spending, but its link stays live until the coin is
-  // actually spent). Both are "outstanding"; both are persisted per-wallet.
-  _giftKey() {
-    return this._cacheKey() + ':gift';
-  }
-  _reclaimedKey() {
-    return this._cacheKey() + ':giftfree';
-  }
   _loadSet(key) {
     try {
       return new Set(JSON.parse(localStorage.getItem(key) || '[]'));
@@ -1518,179 +1503,37 @@ export class Wallet {
       return new Set();
     }
   }
-  reservedSet() {
-    if (!this._reserved) this._reserved = this._loadSet(this._giftKey());
-    return this._reserved;
-  }
-  reclaimedSet() {
-    if (!this._reclaimed) this._reclaimed = this._loadSet(this._reclaimedKey());
-    return this._reclaimed;
-  }
-  isReserved(id) {
-    return this.reservedSet().has(id);
+
+  // ---- optional-feature seams ---------------------------------------------
+  // Coin locks: features contribute sets of coin ids that spending and the
+  // balance treat as unavailable.
+  registerCoinLock(fn) { this._coinLocks.push(fn); }
+  lockedCoinIds() {
+    const all = new Set();
+    for (const fn of this._coinLocks) { try { for (const id of fn()) all.add(id); } catch {} }
+    return all;
   }
-  _saveReserved() {
-    try { localStorage.setItem(this._giftKey(), JSON.stringify([...this.reservedSet()])); } catch {}
+  // Namespaced per-wallet persisted state for features (swaps, ark, ...).
+  featureStateKey(name) { return this._cacheKey() + ':' + name; }
+  loadFeatureState(name, fallback = null) {
+    try { const v = JSON.parse(localStorage.getItem(this.featureStateKey(name)) || 'null'); return v == null ? fallback : v; } catch { return fallback; }
   }
-  _saveReclaimed() {
-    try { localStorage.setItem(this._reclaimedKey(), JSON.stringify([...this.reclaimedSet()])); } catch {}
+  saveFeatureState(name, value) {
+    try { localStorage.setItem(this.featureStateKey(name), JSON.stringify(value)); } catch {}
   }
 
-  // ---- Ark support -------------------------------------------------------
-  // Persisted ArkManager state (vtxos, in-flight action checkpoints, movement
-  // history — no secrets: vtxo keys are re-derived from the seed).
-  _arkKey() { return this._cacheKey() + ':ark'; }
-  loadArkState() {
-    try { return JSON.parse(localStorage.getItem(this._arkKey()) || 'null'); } catch { return null; }
-  }
-  saveArkState(state) {
-    try { localStorage.setItem(this._arkKey(), JSON.stringify(state)); } catch {}
-  }
 
-  // ---- Boltz swap support ----------------------------------------------
-  // Persisted swap records (public metadata only — keys/preimage are re-derived
-  // deterministically from the seed via swapNode, so nothing secret is stored).
-  _swapKey() { return this._cacheKey() + ':swaps'; }
-  loadSwaps() {
-    try { return JSON.parse(localStorage.getItem(this._swapKey()) || '[]'); } catch { return []; }
-  }
-  saveSwaps(list) {
-    try { localStorage.setItem(this._swapKey(), JSON.stringify(list)); } catch {}
-  }
-  _swapIdxKey() { return this._cacheKey() + ':swapidx'; }
-  // Reserve the next swap index: monotonic + persisted on every call. A reverse/
-  // submarine attempt that fails AFTER Boltz created the swap (a later validation
-  // throw, a dropped response) still burns its index, so a retry can't reuse the
-  // same deterministic preimage (Boltz rejects "swap with this preimage exists").
-  // Seeded from saved swaps so existing wallets don't regress.
-  nextSwapIndex() {
-    const fromSaved = this.loadSwaps().reduce((m, s) => Math.max(m, (s.swapIndex ?? -1) + 1), 0);
-    let stored = 0;
-    try { stored = parseInt(localStorage.getItem(this._swapIdxKey()) || '0', 10) || 0; } catch {}
-    const idx = Math.max(fromSaved, stored);
-    try { localStorage.setItem(this._swapIdxKey(), String(idx + 1)); } catch {}
-    return idx;
-  }
-  // Deterministic swap keypair on a dedicated chain (2) so swap keys never
-  // collide with receive (0) / change (1). Returns the HDKey node (has
-  // privateKey + publicKey, 33-byte compressed).
-  swapNode(index) {
-    return this.account().deriveChild(2).deriveChild(index);
-  }
-  // Passive reclaim: free the coin for spending but keep tracking the live link
-  // so it can still be revoked later (until the coin is spent).
-  unreserve(id) {
-    this.reservedSet().delete(id);
-    this.reclaimedSet().add(id);
-    this._saveReserved();
-    this._saveReclaimed();
-  }
 
-  // Truly revoke an unclaimed gift: spend its coin back into our own wallet,
-  // which double-spends the gift's presigned input so the link can't be claimed
-  // once this confirms. Uses a high fee to win any race with a claimer.
-  async revokeGift(id, feeRate) {
-    const draft = this.buildTx({ recipients: [{ address: this.freshChange().address }], feeRate, coinIds: [id], sendMax: true });
-    const hexTx = this.sign(draft.tx);
-    const txid = await this.broadcast(hexTx);
-    this.reservedSet().delete(id);
-    this.reclaimedSet().delete(id);
-    this._saveReserved();
-    this._saveReclaimed();
-    return txid;
-  }
-  // Outstanding gifts (reserved + reclaimed) whose coin is still unspent; prunes
-  // any whose coin has since been claimed/spent. { id, reserved, value }.
-  outstandingGifts() {
-    const live = new Set(this.utxos.map((u) => utxoId(u)));
-    const res = this.reservedSet();
-    const rec = this.reclaimedSet();
-    let changed = false;
-    for (const id of [...res]) if (!live.has(id)) { res.delete(id); changed = true; }
-    for (const id of [...rec]) if (!live.has(id)) { rec.delete(id); changed = true; }
-    if (changed) { this._saveReserved(); this._saveReclaimed(); }
-    return [...new Set([...res, ...rec])].map((id) => ({
-      id,
-      reserved: res.has(id),
-      value: (this.utxos.find((u) => utxoId(u) === id) || {}).value,
-    }));
-  }
 
-  // Persistent gift records (per account): the shareable link/code + amount, so a
-  // gift's link/QR can be re-viewed later and a claimed one identified in history.
-  _giftRecordsKey() { return this._cacheKey() + ':giftrec'; }
-  giftRecords() {
-    if (!this._giftRecords) { try { this._giftRecords = JSON.parse(localStorage.getItem(this._giftRecordsKey()) || '{}'); } catch { this._giftRecords = {}; } }
-    return this._giftRecords;
-  }
-  _saveGiftRecords() { try { localStorage.setItem(this._giftRecordsKey(), JSON.stringify(this.giftRecords())); } catch {} }
-  recordGift({ code, locked, amount, claimCode, outpoints }) {
-    if (!outpoints || !outpoints.length) return;
-    this.giftRecords()[outpoints[0]] = { id: outpoints[0], code, locked: !!locked, amount, claimCode: claimCode || null, outpoints, created: Date.now(), revoked: false };
-    this._saveGiftRecords();
-  }
-  giftLink(id) { return this.giftRecords()[id] || null; }
-  markGiftRevoked(id) { const r = this.giftRecords()[id]; if (r) { r.revoked = true; this._saveGiftRecords(); } }
-  // Gifts whose coin has been spent and weren't revoked by us → claimed. (Only
-  // once scanned, so an un-synced wallet doesn't mislabel everything as claimed.)
-  claimedGifts() {
-    if (!this.loaded) return [];
-    const live = new Set(this.utxos.map((u) => utxoId(u)));
-    return Object.values(this.giftRecords())
-      .filter((r) => !r.revoked && r.outpoints && !r.outpoints.some((o) => live.has(o)))
-      .map((r) => ({ id: r.id, amount: r.amount, locked: r.locked, created: r.created, claimTxid: r.claimTxid || null, outpoints: r.outpoints }))
-      .sort((a, b) => (b.created || 0) - (a.created || 0));
-  }
 
-  // Remember which tx claimed a gift (resolved lazily via outspend) so the
-  // history can merge the gift row with its claim transaction.
-  setGiftClaimTx(id, txid) {
-    const recs = this.giftRecords();
-    if (recs[id] && recs[id].claimTxid !== txid) {
-      recs[id].claimTxid = txid;
-      this._saveGiftRecords();
-    }
-  }
 
-  // Best-fit coin selection for a gift of `gift` sats (needs gift + a dust
-  // change): the smallest single confirmed coin that covers it — one input and
-  // the least value locked until claim — else the fewest large coins. Returns
-  // the selected UTXOs, or null if confirmed funds are insufficient.
-  _selectGiftCoins(gift) {
-    const DUST = 294n;
-    const need = gift + DUST;
-    const avail = this.utxos.filter((u) => !this.isReserved(utxoId(u)) && (u.confirmed || u.chain === 1));
-    const single = avail.filter((u) => BigInt(u.value) >= need).sort((a, b) => a.value - b.value)[0];
-    if (single) return [single];
-    const sel = [];
-    let sum = 0n;
-    for (const u of [...avail].sort((a, b) => b.value - a.value)) {
-      sel.push(u);
-      sum += BigInt(u.value);
-      if (sum >= need) return sel;
-    }
-    return null; // insufficient confirmed funds
-  }
 
-  // Sats that creating this gift right now would lock (the selected coins'
-  // total), or null if confirmed funds are insufficient. Lets the UI warn when
-  // the lock would dwarf the gift and offer to split a coin first.
-  giftLockPreview(amountSats) {
-    const sel = this._selectGiftCoins(BigInt(Math.round(amountSats)));
-    return sel ? sel.reduce((s, u) => s + u.value, 0) : null;
-  }
 
-  // The coins a gift of this amount would lock: total value + how many inputs.
-  // A high input count means a costly-to-claim gift (each input adds to the
-  // claimer's fee) — the UI uses it to recommend splitting/consolidating first.
-  giftCoinSummary(amountSats) {
-    const sel = this._selectGiftCoins(BigInt(Math.round(amountSats)));
-    return sel ? { lock: sel.reduce((s, u) => s + u.value, 0), count: sel.length } : null;
-  }
 
   // Number of unreserved spendable coins (for the consolidate prompt/action).
   spendableCoinCount() {
-    return this.utxos.filter((u) => !this.isReserved(utxoId(u)) && (u.confirmed || u.chain === 1)).length;
+    const locked = this.lockedCoinIds();
+    return this.utxos.filter((u) => !locked.has(utxoId(u)) && (u.confirmed || u.chain === 1)).length;
   }
 
   // Merge all unreserved spendable coins into one, via a max self-send. Leaves
@@ -1703,56 +1546,8 @@ export class Wallet {
     return { txid: draft.tx.id, inputs: draft.inputsCount };
   }
 
-  // Build a signed gift from already-chosen coins. If the gift leaves a viable
-  // (>= dust) change, output0 is that change back to us, cryptographically fixed
-  // by signing input0 SIGHASH_SINGLE (the rest SIGHASH_NONE) — so our change is
-  // locked while the claimer is free to add their own output. If there's no
-  // viable change (a whole-balance gift), there's no output at all and every
-  // input is SIGHASH_NONE, so the claimer sweeps the entire amount. Reserves the
-  // coins; returns { code, amount, reserved } where amount is what the claimer
-  // receives before their fee (the gift, or the whole swept sum).
-  _buildGiftPsbt(sel, gift) {
-    const DUST = 294n;
-    const sum = sel.reduce((s, u) => s + BigInt(u.value), 0n);
-    const change = sum - gift;
-    const keepChange = change >= DUST;
-    const sigOf = (i) => (keepChange && i === 0 ? btc.SigHash.SINGLE : btc.SigHash.NONE);
-    const t = new btc.Transaction({ allowUnknownOutputs: true });
-    sel.forEach((u, i) => {
-      const pay = p2wpkh(this.derive(u.chain, u.index).pubkey, this.netCfg.net);
-      t.addInput({ ...pay, txid: u.txid, index: u.vout, sighashType: sigOf(i), witnessUtxo: { script: pay.script, amount: BigInt(u.value) } });
-    });
-    if (keepChange) t.addOutputAddress(this.freshChange().address, change, this.netCfg.net);
-    sel.forEach((u, i) => t.signIdx(this.node(u.chain, u.index).privateKey, i, [sigOf(i)]));
-
-    for (const u of sel) this.reservedSet().add(utxoId(u));
-    this._saveReserved();
-    return { code: base32nopad.encode(_encodeCompactGift(t)), amount: Number(keepChange ? gift : sum), reserved: sel.map(utxoId) };
-  }
 
-  // Gift the entire spendable balance: a no-change sweep of all unreserved
-  // spendable coins (confirmed, plus our own unconfirmed change). The claimer
-  // receives the whole amount minus their claim fee.
-  createGiftAll(feeRate) {
-    const rate = Math.max(1, Math.round(feeRate));
-    const sel = this.utxos.filter((u) => !this.isReserved(utxoId(u)) && (u.confirmed || u.chain === 1));
-    if (!sel.length) throw new Error('No coins available to gift.');
-    const sum = sel.reduce((s, u) => s + BigInt(u.value), 0n);
-    if (sum < BigInt(giftMinimum(rate))) throw new Error('Gift amount is too small.');
-    return this._buildGiftPsbt(sel, sum); // change = 0 → no-change sweep
-  }
 
-  // Build a gift link from a best-fit coin, locking the least value. No fee is
-  // reserved here: the claimer's wallet looks up the fee rate at claim time and
-  // subtracts it from the amount.
-  createGift(amountSats, feeRate) {
-    const gift = BigInt(Math.round(amountSats));
-    const rate = Math.max(1, Math.round(feeRate));
-    if (gift < BigInt(giftMinimum(rate))) throw new Error('Gift amount is too small.');
-    const sel = this._selectGiftCoins(gift);
-    if (!sel) throw new Error('Not enough confirmed funds for that gift amount.');
-    return this._buildGiftPsbt(sel, gift);
-  }
 
   // Our nostr identity (used to DM a locked gift's claim code to the recipient).
   nostrPubkey() { return (this.nostr && this.nostr.pk) || null; }
@@ -1762,63 +1557,6 @@ export class Wallet {
     return this.nostr && this.nostr.sk ? this.nostr.sendDM(recipientPkHex, text) : false;
   }
 
-  // Split + gift in one shot, with no confirmation wait: broadcast a self-send
-  // that carves out a gift+dust coin, then build the gift spending that
-  // still-unconfirmed carve-out. The funding and the claim form a chain that
-  // confirms together; the recipient just sees a pending balance until the
-  // split confirms. Lets the sender lock only ~the gift amount (instead of a
-  // whole large coin) without waiting for the split to confirm first.
-  async createGiftFromSplit(amountSats, feeRate) {
-    const gift = Math.round(amountSats);
-    const rate = Math.max(1, Math.round(feeRate));
-    if (BigInt(gift) < BigInt(giftMinimum(rate))) throw new Error('Gift amount is too small.');
-    const DUST = 294;
-    const recvIndex = this.nextReceiveIndex;
-    const carveAddr = this.derive(0, recvIndex).address;
-    const changeIndex = this.nextChangeIndex;
-
-    // Carve out exactly gift + dust to one of our own addresses; the rest comes
-    // back as change. buildTx already spends confirmed coins largest-first.
-    const draft = this.buildTx({ recipients: [{ address: carveAddr, amount: gift + DUST }], feeRate: rate });
-    const carveIdx = draft.outputs.findIndex((o) => o.address === carveAddr);
-    if (carveIdx < 0) throw new Error('Could not size the split output.');
-    const hexTx = this.sign(draft.tx);
-    const splitTxid = draft.tx.id;
-    await this.broadcast(hexTx);
-
-    // Wait until the carve-out is actually visible in the mempool before we
-    // build the gift on top of it and reserve it. Otherwise a background refresh
-    // could rebuild the address from a not-yet-indexed API response, transiently
-    // drop the coin, and prune the reservation — risking a double-spend.
-    let seen = false;
-    for (let i = 0; i < 8 && !seen; i++) {
-      await sleep(i === 0 ? 400 : 900);
-      try {
-        const us = await this.api.addressUtxos(carveAddr);
-        seen = us.some((u) => u.txid === splitTxid && u.vout === carveIdx);
-      } catch {}
-    }
-    if (!seen) throw new Error('The split is taking a while to propagate. Once it confirms, create the gift from the new coin.');
-
-    // Reflect the split in our coin set — drop the spent inputs, add the
-    // (now mempool-visible) carve-out and change — so balances and gift tracking
-    // are correct immediately; a background scan reconciles the rest.
-    const spent = new Set();
-    for (let i = 0; i < draft.tx.inputsLength; i++) {
-      const inp = draft.tx.getInput(i);
-      spent.add(`${hex.encode(inp.txid)}:${inp.index}`);
-    }
-    this.utxos = this.utxos.filter((u) => !spent.has(utxoId(u)));
-    this.utxos.push({ txid: splitTxid, vout: carveIdx, value: gift + DUST, address: carveAddr, chain: 0, index: recvIndex, confirmed: false });
-    const changeIdx = draft.outputs.findIndex((o, i) => i !== carveIdx);
-    if (changeIdx >= 0) {
-      const co = draft.outputs[changeIdx];
-      this.utxos.push({ txid: splitTxid, vout: changeIdx, value: co.amount, address: co.address, chain: 1, index: changeIndex, confirmed: false });
-    }
-    this._recomputeBalanceFromUtxos();
-
-    return this._buildGiftPsbt([{ txid: splitTxid, vout: carveIdx, value: gift + DUST, chain: 0, index: recvIndex }], BigInt(gift));
-  }
 
   // --- realtime (mempool.space WebSocket) ---------------------------------
   // Pushes us new mempool/confirmed transactions for our addresses so history
@@ -2612,147 +2350,7 @@ export function xpubToZpub(xpub) {
   return _b58c.encode(data);
 }
 
-// Gift-link claiming (sender side is Wallet.createGift). A gift code is a
-// base64url PSBT: one SIGHASH_SINGLE-signed input + the sender's change output.
-// previewGift reports the room available to the claimer (before their fee);
-// buildClaimTx adds the claimer's output and finalizes a broadcastable tx.
-// Smallest sensible gift at a given fee rate: dust + one claim fee of headroom
-// (floored at 546 sats), so the recipient clears dust even if fees climb.
-export function giftMinimum(feeRate) {
-  const rate = Math.max(1, Math.round(feeRate));
-  const claimFee = Math.ceil((11 + 68 + 31 * 2) * rate);
-  return Math.max(546, 294 + claimFee);
-}
-
-// ---- compact gift codec ----------------------------------------------------
-// A gift link used to carry a full PSBT (verbose). The claimer only needs the
-// presigned inputs (outpoint, amount, pubkey, signature) and the sender's
-// committed change output, so we serialize just those — ~25% smaller, and (via
-// base32 + an uppercase /g/ URL) it scans in the QR's denser alphanumeric mode.
-// Legacy base64url-PSBT links still claim; _giftTx auto-detects the format.
-const GIFT_MAGIC = 0x01;
-const _u8 = (n) => Uint8Array.of(n & 0xff);
-const _le32 = (n) => { const b = new Uint8Array(4); new DataView(b.buffer).setUint32(0, n >>> 0, true); return b; };
-const _le64 = (n) => { const b = new Uint8Array(8); new DataView(b.buffer).setBigUint64(0, BigInt(n), true); return b; };
 
-function _encodeCompactGift(tx) {
-  const hasChange = tx.outputsLength > 0;
-  const parts = [_u8(GIFT_MAGIC), _u8(hasChange ? 1 : 0), _u8(tx.inputsLength)];
-  for (let i = 0; i < tx.inputsLength; i++) {
-    const inp = tx.getInput(i);
-    const [pubkey, sig] = inp.partialSig[0]; // pubkey(33), sig = DER + sighash byte
-    parts.push(inp.txid, _le32(inp.index), _le64(inp.witnessUtxo.amount), pubkey, _u8(sig.length), sig);
-  }
-  if (hasChange) {
-    const o = tx.getOutput(0); // p2wpkh change: script = [00 14 <20-byte hash>]
-    parts.push(_le64(o.amount), o.script.slice(2));
-  }
-  return concatBytes(...parts);
-}
-
-function _decodeCompactGift(bytes) {
-  let p = 0;
-  const rd = (n) => bytes.slice(p, (p += n));
-  const r32 = () => { const v = new DataView(bytes.buffer, bytes.byteOffset + p, 4).getUint32(0, true); p += 4; return v; };
-  const r64 = () => { const v = new DataView(bytes.buffer, bytes.byteOffset + p, 8).getBigUint64(0, true); p += 8; return v; };
-  p++; // magic
-  const hasChange = !!(bytes[p++] & 1);
-  const n = bytes[p++];
-  const t = new btc.Transaction({ allowUnknownOutputs: true });
-  for (let i = 0; i < n; i++) {
-    const txid = rd(32), vout = r32(), amount = r64(), pubkey = rd(33), sigLen = bytes[p++], sig = rd(sigLen);
-    const pay = p2wpkh(pubkey, btc.NETWORK); // witness-program .script is network-independent
-    // second arg true: re-add an already-signed input without tripping the sign-status guard
-    t.addInput({ txid, index: vout, witnessUtxo: { script: pay.script, amount }, sighashType: sig[sig.length - 1], partialSig: [[pubkey, sig]] }, true);
-  }
-  if (hasChange) {
-    const amount = r64();
-    const hash = rd(20);
-    t.addOutput({ script: concatBytes(_u8(0x00), _u8(0x14), hash), amount }, true);
-  }
-  return t;
-}
-
-// Parse a gift code to a Transaction. New format: base32(compact). Legacy:
-// base64url(PSBT). Auto-detected via the compact magic byte.
-function _giftTx(code) {
-  try {
-    const b = base32nopad.decode(code.toUpperCase());
-    if (b[0] === GIFT_MAGIC) return _decodeCompactGift(b);
-  } catch {}
-  return btc.Transaction.fromPSBT(base64urlnopad.decode(code));
-}
-
-function _sumInputs(tx) {
-  let inAmt = 0n;
-  for (let i = 0; i < tx.inputsLength; i++) inAmt += tx.getInput(i).witnessUtxo.amount;
-  return inAmt;
-}
-// The sender's change committed in a gift PSBT, or 0 for a no-change (whole-
-// balance) gift that has no outputs at all.
-function _giftChange(tx) {
-  return tx.outputsLength > 0 ? tx.getOutput(0).amount : 0n;
-}
-// The gift's funding outpoints (the coins its presigned inputs spend). If any is
-// already spent — even by an unconfirmed claim — the gift has been taken and
-// re-claiming would be a doomed double-spend. Used to gate the claim screen.
-export function giftOutpoints(code) {
-  try {
-    const tx = _giftTx(code);
-    const out = [];
-    for (let i = 0; i < tx.inputsLength; i++) {
-      const inp = tx.getInput(i);
-      out.push({ txid: hex.encode(inp.txid), vout: inp.index });
-    }
-    return out;
-  } catch {
-    return [];
-  }
-}
-export function previewGift(code) {
-  try {
-    const tx = _giftTx(code);
-    // room is the full amount the claimer receives (inputs minus our change);
-    // the claim fee is subtracted from it at claim time, so report inputs too
-    // so the caller can size that fee for this PSBT.
-    return { room: Number(_sumInputs(tx) - _giftChange(tx)), inputs: tx.inputsLength };
-  } catch {
-    return null;
-  }
-}
-
-export function buildClaimTx(code, toAddress, feeRate, net) {
-  const tx = _giftTx(code);
-  const room = _sumInputs(tx) - _giftChange(tx);
-  const fee = BigInt(Math.max(1, Math.ceil((11 + 68 * tx.inputsLength + 31 * 2) * Math.max(1, Math.round(feeRate)))));
-  const out = room - fee;
-  if (out < 294n) throw new Error('Gift is too small to claim at this fee rate.');
-  tx.addOutputAddress(toAddress, out, net);
-  tx.finalize();
-  return { hex: tx.hex, txid: tx.id, amount: Number(out), fee: Number(fee) };
-}
-
-// A gift locked to a recipient's nostr key. The amount + recipient pubkey are
-// public (anyone can see what it is and who it's for), but the claim payload (the
-// gift code) is NIP-44-encrypted to the recipient via an ephemeral key — so the
-// link can be shared openly yet only the recipient's nostr key can claim it.
-const LOCKED_GIFT_VERSION = 1;
-// Encrypt the gift's claim payload under a one-time code. The code is delivered
-// to the recipient via a nostr DM; the public link carries only the ciphertext.
-// Returns { blob (for the /lg/ link), claimCode (to DM) }.
-export function lockGift(code, amount, recipientPkHex) {
-  const { code: claimCode, ctCode, eph, ctKey } = encryptGiftPayload(code, recipientPkHex);
-  const blob = base64urlnopad.encode(new TextEncoder().encode(JSON.stringify({ v: LOCKED_GIFT_VERSION, amount, to: recipientPkHex, ct: ctCode, eph, ctKey })));
-  return { blob, claimCode };
-}
-// The public fields of a locked-gift blob (or null). Decryption needs the code.
-export function previewLockedGift(blob) {
-  try {
-    const o = JSON.parse(new TextDecoder().decode(base64urlnopad.decode(blob)));
-    if (o.v === LOCKED_GIFT_VERSION && typeof o.amount === 'number' && o.to && o.ct) return o;
-  } catch {}
-  return null;
-}
 
 function firstUnused(chain) {
   const u = chain.find((a) => !a.used);