diff --git a/src/Core/Wallet/CoinAmount.cs b/src/Core/Wallet/CoinAmount.cs
new file mode 100644
index 0000000..35f7006
--- /dev/null
+++ b/src/Core/Wallet/CoinAmount.cs
@@ -0,0 +1,35 @@
+using System.Globalization;
+
+namespace PalladiumWallet.Core.Wallet;
+
+/// <summary>
+/// Conversione satoshi ↔ unità coin (8 decimali) per visualizzazione e input.
+/// Si lavora sempre in satoshi internamente; la stringa è solo presentazione.
+/// </summary>
+public static class CoinAmount
+{
+    public const long SatsPerCoin = 100_000_000;
+
+    public static string Format(long sats, string unit = "") =>
+        (sats / (decimal)SatsPerCoin).ToString("0.00000000", CultureInfo.InvariantCulture)
+        + (unit.Length > 0 ? " " + unit : "");
+
+    /// <summary>Parsa un importo in coin (punto o virgola decimale) in satoshi.</summary>
+    public static bool TryParseCoins(string text, out long sats)
+    {
+        sats = 0;
+        text = text.Trim().Replace(',', '.');
+        if (!decimal.TryParse(text, NumberStyles.Number, CultureInfo.InvariantCulture, out var coins)
+            || coins < 0)
+            return false;
+        try
+        {
+            sats = (long)(coins * SatsPerCoin);
+        }
+        catch (OverflowException)
+        {
+            return false;
+        }
+        return true;
+    }
+}
diff --git a/src/Core/Wallet/TransactionFactory.cs b/src/Core/Wallet/TransactionFactory.cs
new file mode 100644
index 0000000..a5ac913
--- /dev/null
+++ b/src/Core/Wallet/TransactionFactory.cs
@@ -0,0 +1,119 @@
+using NBitcoin;
+using NBitcoin.Policy;
+using PalladiumWallet.Core.Chain;
+using PalladiumWallet.Core.Crypto;
+using PalladiumWallet.Core.Storage;
+
+namespace PalladiumWallet.Core.Wallet;
+
+/// <summary>Esito della costruzione di una transazione.</summary>
+public sealed class BuiltTransaction
+{
+    public required Transaction Transaction { get; init; }
+    public required Money Fee { get; init; }
+    public required FeeRate FeeRate { get; init; }
+    public required bool Signed { get; init; }
+
+    /// <summary>PSBT per i flussi watch-only/air-gapped/multisig (§6.5).</summary>
+    public required PSBT Psbt { get; init; }
+
+    public string ToHex() => Transaction.ToHex();
+    public string Txid => Transaction.GetHash().ToString();
+}
+
+/// <summary>
+/// Costruzione e firma delle transazioni (blueprint §6) sopra le primitive
+/// NBitcoin: selezione monete (manuale o automatica), fee a rate fisso,
+/// invia-tutto con fee sottratta, change sulla catena interna, RBF di default.
+/// Con un account watch-only produce la PSBT non firmata (§6.5).
+/// </summary>
+public sealed class TransactionFactory(HdAccount account)
+{
+    private Network Network => PalladiumNetworks.For(account.Profile.Kind);
+
+    /// <summary>
+    /// Costruisce (e se possibile firma) una transazione.
+    /// </summary>
+    /// <param name="utxos">UTXO selezionati (coin control §6.2) o tutti quelli spendibili.</param>
+    /// <param name="transactions">Tx di provenienza degli UTXO (txid → tx), dalla sincronizzazione.</param>
+    /// <param name="destination">Indirizzo destinatario.</param>
+    /// <param name="amountSats">Importo; ignorato se <paramref name="sendAll"/>.</param>
+    /// <param name="feeRateSatPerVByte">Fee rate fisso in sat/vByte (§6.4).</param>
+    /// <param name="changeIndex">Indice del prossimo indirizzo di change (catena interna).</param>
+    /// <param name="sendAll">Invia tutto: fee sottratta dall'importo (§6.1).</param>
+    public BuiltTransaction Build(
+        IReadOnlyList<CachedUtxo> utxos,
+        IReadOnlyDictionary<string, Transaction> transactions,
+        BitcoinAddress destination,
+        long amountSats,
+        decimal feeRateSatPerVByte,
+        int changeIndex,
+        bool sendAll = false)
+    {
+        var spendable = utxos.Where(u => !u.Frozen).ToList();
+        if (spendable.Count == 0)
+            throw new WalletSpendException("Nessun UTXO spendibile selezionato.");
+
+        var coins = spendable.Select(u => new Coin(
+            new OutPoint(uint256.Parse(u.Txid), (uint)u.Vout),
+            transactions[u.Txid].Outputs[u.Vout])).ToList();
+
+        var feeRate = new FeeRate(Money.Satoshis(feeRateSatPerVByte * 1000m), 1000);
+        var builder = Network.CreateTransactionBuilder();
+        builder.SetVersion(2);
+        // Sequence RBF per consentire il bump della fee (§6.6).
+        builder.OptInRBF = true;
+        builder.AddCoins(coins);
+        builder.SetChange(account.GetChangeAddress(changeIndex));
+        builder.SendEstimatedFees(feeRate);
+
+        if (sendAll)
+            builder.Send(destination, coins.Sum(c => (Money)c.Amount)).SubtractFees();
+        else
+            builder.Send(destination, Money.Satoshis(amountSats));
+
+        if (!account.IsWatchOnly)
+        {
+            builder.AddKeys(spendable
+                .Select(u => account.GetExtPrivateKey(u.IsChange, u.AddressIndex))
+                .ToArray());
+        }
+
+        Transaction tx;
+        try
+        {
+            tx = builder.BuildTransaction(sign: !account.IsWatchOnly);
+        }
+        catch (NotEnoughFundsException ex)
+        {
+            throw new WalletSpendException($"Fondi insufficienti: {ex.Message}");
+        }
+
+        if (!account.IsWatchOnly)
+        {
+            if (!builder.Verify(tx, out TransactionPolicyError[] errors))
+                throw new WalletSpendException(
+                    "Transazione non valida: " + string.Join("; ", errors.Select(e => e.ToString())));
+        }
+
+        return new BuiltTransaction
+        {
+            Transaction = tx,
+            Fee = GetFee(tx, coins),
+            FeeRate = feeRate,
+            Signed = !account.IsWatchOnly,
+            Psbt = builder.BuildPSBT(sign: !account.IsWatchOnly),
+        };
+    }
+
+    private static Money GetFee(Transaction tx, IReadOnlyList<Coin> coins)
+    {
+        var spentOutpoints = tx.Inputs.Select(i => i.PrevOut).ToHashSet();
+        var inputSum = coins.Where(c => spentOutpoints.Contains(c.Outpoint))
+            .Sum(c => (Money)c.Amount);
+        return inputSum - tx.Outputs.Sum(o => o.Value);
+    }
+}
+
+/// <summary>Errore di costruzione/firma della spesa (fondi, policy, parametri).</summary>
+public sealed class WalletSpendException(string message) : Exception(message);
diff --git a/src/Core/Wallet/WalletLoader.cs b/src/Core/Wallet/WalletLoader.cs
new file mode 100644
index 0000000..2395b83
--- /dev/null
+++ b/src/Core/Wallet/WalletLoader.cs
@@ -0,0 +1,59 @@
+using NBitcoin;
+using PalladiumWallet.Core.Chain;
+using PalladiumWallet.Core.Crypto;
+using PalladiumWallet.Core.Storage;
+
+namespace PalladiumWallet.Core.Wallet;
+
+/// <summary>
+/// Ponte documento wallet ↔ dominio (blueprint §4.5): dal file ricostruisce
+/// l'HdAccount giusto (da seed o watch-only da xpub). È l'embrione della
+/// factory dei tipi di wallet; crescerà con multisig e importati.
+/// </summary>
+public static class WalletLoader
+{
+    public static ChainProfile ProfileOf(WalletDocument doc) =>
+        ChainProfiles.For(Enum.Parse<NetKind>(doc.Network, ignoreCase: true));
+
+    public static HdAccount ToAccount(WalletDocument doc)
+    {
+        var profile = ProfileOf(doc);
+        var kind = Enum.Parse<ScriptKind>(doc.ScriptKind);
+        var path = KeyPath.Parse(doc.AccountPath);
+
+        if (doc.Mnemonic is { } words)
+        {
+            if (!Bip39.TryParse(words, out var mnemonic))
+                throw new InvalidDataException("Mnemonica del file wallet non valida.");
+            return HdAccount.FromSeed(Bip39.ToSeed(mnemonic!, doc.Passphrase), kind, profile, path);
+        }
+
+        if (!Slip132.TryDecodePublic(doc.AccountXpub, profile, out var xpub, out _))
+            throw new InvalidDataException("Xpub del file wallet non valida per questa rete.");
+        return HdAccount.FromAccountXpub(xpub!, kind, profile, path);
+    }
+
+    /// <summary>Crea il documento per un nuovo wallet da seed.</summary>
+    public static (WalletDocument Doc, HdAccount Account) NewFromMnemonic(
+        string words, string? passphrase, ScriptKind kind, ChainProfile profile, KeyPath? customPath = null)
+    {
+        if (!Bip39.TryParse(words, out var mnemonic))
+            throw new InvalidDataException("Mnemonica non valida (parole o checksum errati).");
+
+        var account = customPath is null
+            ? HdAccount.FromMnemonic(mnemonic!, passphrase, kind, profile)
+            : HdAccount.FromSeed(Bip39.ToSeed(mnemonic!, passphrase), kind, profile, customPath);
+
+        var doc = new WalletDocument
+        {
+            Network = profile.NetName,
+            ScriptKind = kind.ToString(),
+            Mnemonic = words.Trim(),
+            Passphrase = passphrase,
+            AccountPath = account.AccountPath.ToString(),
+            AccountXpub = account.ToSlip132(),
+            MasterFingerprint = Convert.ToHexString(account.MasterFingerprint.ToBytes()).ToLowerInvariant(),
+        };
+        return (doc, account);
+    }
+}