input-output-hk · mchappell · Jul 1, 2025 · Jun 27, 2025
@@ -148,3 +148,6 @@ E2E_FORCE_TREZOR_PICKED=false
 
 # ADA handle cache lifetime
 HANDLE_RESOLUTION_CACHE_LIFETIME=600000
+
+# mempool.space api
+MEMPOOLSPACE_URL=https://mempool.lw.iog.io
@@ -99,3 +99,6 @@ LACE_EXTENSION_UNINSTALL_REDIRECT_URL=
 
 # Midnight
 MIDNIGHT_EVENT_BANNER_REMINDER_TIME=129600000
+
+# mempool.space api
+MEMPOOLSPACE_URL=https://mempool.lw.iog.io
@@ -117,3 +117,6 @@ MIN_NUMBER_OF_COSIGNERS=2
 
 # POLLING PAUSE AFTER INACTIVITY
 SESSION_TIMEOUT=300000
+
+# mempool.space api
+MEMPOOLSPACE_URL=https://mempool.lw.iog.io
@@ -18,7 +18,7 @@
   "permissions": ["webRequest", "storage", "tabs", "unlimitedStorage"],
   "host_permissions": ["<all_urls>"],
   "content_security_policy": {
-    "extension_pages": "default-src 'self' $LOCALHOST_DEFAULT_SRC; frame-src https://connect.trezor.io/ https://www.youtube-nocookie.com; script-src 'self' 'wasm-unsafe-eval'; font-src 'self' data: https://use.typekit.net; object-src 'self'; connect-src $BLOCKFROST_URLS $MAESTRO_URLS $CARDANO_SERVICES_URLS $CARDANO_WS_SERVER_URLS $SENTRY_URL $DAPP_RADAR_APPI_URL https://coingecko.live-mainnet.eks.lw.iog.io https://coingecko.live-mainnet.eks.lw.iog.io https://muesliswap.live-mainnet.eks.lw.iog.io $LOCALHOST_CONNECT_SRC $POSTHOG_HOST https://use.typekit.net https://api.handle.me/ https://*.api.handle.me/ data:; style-src * 'unsafe-inline'; img-src * data: blob:;"
+    "extension_pages": "default-src 'self' $LOCALHOST_DEFAULT_SRC; frame-src https://connect.trezor.io/ https://www.youtube-nocookie.com; script-src 'self' 'wasm-unsafe-eval'; font-src 'self' data: https://use.typekit.net; object-src 'self'; connect-src $MEMPOOLSPACE_URL $BLOCKFROST_URLS $MAESTRO_URLS $CARDANO_SERVICES_URLS $CARDANO_WS_SERVER_URLS $SENTRY_URL $DAPP_RADAR_APPI_URL https://coingecko.live-mainnet.eks.lw.iog.io https://coingecko.live-mainnet.eks.lw.iog.io https://muesliswap.live-mainnet.eks.lw.iog.io $LOCALHOST_CONNECT_SRC $POSTHOG_HOST https://use.typekit.net https://api.handle.me/ https://*.api.handle.me/ data:; style-src * 'unsafe-inline'; img-src * data: blob:;"
   },
   "content_scripts": [
     {

@@ -254,6 +254,15 @@ const bitcoinWalletFactory: BitcoinWalletFactory<Wallet.WalletMetadata, Wallet.A
             Bitcoin.Network.Mainnet
           );
 
+    const featureFlags = await getFeatureFlags(
+      network === Bitcoin.Network.Testnet ? Cardano.NetworkMagics.Preprod : Cardano.NetworkMagics.Mainnet
+    );
+    const useMempoolSpaceFeeMarket = isExperimentEnabled(featureFlags, ExperimentName.MEMPOOLSPACE_FEE_MARKET);
+
+    const feeMarketProvider = useMempoolSpaceFeeMarket
+      ? new Bitcoin.MempoolSpaceMarketProvider(process.env.MEMPOOLSPACE_URL, logger, network)
+      : new Bitcoin.MaestroFeeMarketProvider(provider, logger, network);
+
     if (!walletAccount.metadata.bitcoin) {
       throw new Error('Bitcoin metadata not found');
     }
@@ -278,6 +287,7 @@ const bitcoinWalletFactory: BitcoinWalletFactory<Wallet.WalletMetadata, Wallet.A
     currentBitcoinWalletProvider$.next(provider);
     return new Bitcoin.BitcoinWallet(
       provider,
+      feeMarketProvider,
       localPollingIntervalConfig,
       20,
       walletInfo,

@@ -14,7 +14,8 @@ export enum ExperimentName {
   SEND_CONSOLE_ERRORS_TO_SENTRY = 'send-console-errors-to-sentry',
   BITCOIN_WALLETS = 'bitcoin-wallets',
   NFTPRINTLAB = 'nftprintlab',
-  GLACIER_DROP = 'glacier-drop'
+  GLACIER_DROP = 'glacier-drop',
+  MEMPOOLSPACE_FEE_MARKET = 'bitcoin-mempool-space-fee-market'
 }
 
 export type FeatureFlag = `${ExperimentName}`;

@@ -38,7 +38,8 @@ const defaultFeatureFlags: FeatureFlags = {
   [ExperimentName.SEND_CONSOLE_ERRORS_TO_SENTRY]: false,
   [ExperimentName.BITCOIN_WALLETS]: false,
   [ExperimentName.NFTPRINTLAB]: false,
-  [ExperimentName.GLACIER_DROP]: false
+  [ExperimentName.GLACIER_DROP]: false,
+  [ExperimentName.MEMPOOLSPACE_FEE_MARKET]: false
 };
 
 export const featureFlagsByNetworkInitialValue: FeatureFlagsByNetwork = {

@@ -54,6 +54,7 @@ const transformManifest = (content, mode, jsAssets = []) => {
           : 'http://localhost:* http://127.0.0.1:*'
       )
       .replace('$POSTHOG_HOST', process.env.POSTHOG_HOST)
+      .replace('$MEMPOOLSPACE_URL', process.env.MEMPOOLSPACE_URL)
       .replace('$SENTRY_URL', constructSentryConnectSrc(process.env.SENTRY_DSN))
       .replace('$DAPP_RADAR_APPI_URL', process.env.DAPP_RADAR_API_URL);
 

@@ -10,46 +10,44 @@ It exposes RxJS streams (balance$, utxos$, transactionHistory$) so front-ends ca
 
 The package is organized in 5 modules:
 
-
 <p align="center">
   <img align="middle" src="./assets/modules_chart.png"/>
 </p>
 
 ### **Modules Description**
 
-| Module                                     | Purpose                                                                                                   |
-|--------------------------------------------|-----------------------------------------------------------------------------------------------------------|
-| **common/**                                | Pure, stateless helpers that can be reused by every other module. No network or side-effects.             |
-| `common/address.ts`                        | Convert compressed pubkeys to P2PKH, P2SH-P2WPKH, P2WPKH and P2TR addresses; validate addresses.          |
-| `common/constants.ts`                      | Shared byte-sizes (input/output/overhead), dust threshold, etc.                                           |
-| `common/info.ts`                           | Type that groups the five account-level XPUBs produced for each address type.                             |
-| `common/keyDerivation.ts`                  | BIP-39/BIP-32/Electrum seed derivation, account & child key derivation, Taproot tweaks.                  |
-| `common/network.ts`                        | Enum for Mainnet / Testnet and related helpers.                                                           |
-| `common/taproot.ts`                        | Low-level functions to compute BIP-341 tagged hashes and tweak x-only pub/priv keys.                     |
-| `common/transaction.ts`                    | UnsignedTransaction / SignedTransaction type definitions.                                                 |
-| **input-selection/**                       | Pluggable coin-selection strategies.                                                                      |
-| `input-selection/InputSelector.ts`         | Interface describing the contract for any selector implementation.                                        |
-| `input-selection/GreedyInputSelector.ts`   | Deterministic greedy algorithm that selects largest UTXOs until target + fee is met.                      |
-| **providers/**                             | Abstract access to the Bitcoin network and on-chain data.                                                 |
-| `providers/BlockchainDataProvider.ts`      | Interface for reading chain state, mempool, fee rates, and broadcasting TXs.                             |
-| `providers/MaestroBitcoinDataProvider.ts`  | Concrete HTTP client against Maestro’s REST API.                                                          |
-| `providers/StubBitcoinDataProvider.ts`     | In-memory mock that returns deterministic data for unit tests.                                            |
-| `providers/BlockchainInputResolver.ts`     | Helper that maps a (txid, vout) pair to a full UTxO by calling the provider.                              |
-| **tx-builder/**                            | Everything needed to construct a PSBT ready for signing.                                                 |
-| `tx-builder/TransactionBuilder.ts`         | Accepts outputs, change address, selector, builds PSBT, estimates vBytes & fee.                          |
-| `tx-builder/utils.ts`                      | Constants & helpers specific to size/fee calculation inside the builder.                                  |
-| **wallet/**                                | Stateful, observable wallet core and signer.                                                              |
-| `wallet/BitcoinWallet.ts`                  | Polls provider, maintains `balance$`, `utxos$`, history & pending TXs via RxJS.                            |
-| `wallet/BitcoinSigner.ts`                  | Thin wrapper around `@bitcoinerlab/secp256k1` for PSBT input signing + key zeroisation.                  |
-| `index.ts`                                 | Package entry point.                                                                                      |
+| Module                                    | Purpose                                                                                          |
+| ----------------------------------------- | ------------------------------------------------------------------------------------------------ |
+| **common/**                               | Pure, stateless helpers that can be reused by every other module. No network or side-effects.    |
+| `common/address.ts`                       | Convert compressed pubkeys to P2PKH, P2SH-P2WPKH, P2WPKH and P2TR addresses; validate addresses. |
+| `common/constants.ts`                     | Shared byte-sizes (input/output/overhead), dust threshold, etc.                                  |
+| `common/info.ts`                          | Type that groups the five account-level XPUBs produced for each address type.                    |
+| `common/keyDerivation.ts`                 | BIP-39/BIP-32/Electrum seed derivation, account & child key derivation, Taproot tweaks.          |
+| `common/network.ts`                       | Enum for Mainnet / Testnet and related helpers.                                                  |
+| `common/taproot.ts`                       | Low-level functions to compute BIP-341 tagged hashes and tweak x-only pub/priv keys.             |
+| `common/transaction.ts`                   | UnsignedTransaction / SignedTransaction type definitions.                                        |
+| **input-selection/**                      | Pluggable coin-selection strategies.                                                             |
+| `input-selection/InputSelector.ts`        | Interface describing the contract for any selector implementation.                               |
+| `input-selection/GreedyInputSelector.ts`  | Deterministic greedy algorithm that selects largest UTXOs until target + fee is met.             |
+| **providers/**                            | Abstract access to the Bitcoin network and on-chain data.                                        |
+| `providers/BlockchainDataProvider.ts`     | Interface for reading chain state, mempool, fee rates, and broadcasting TXs.                     |
+| `providers/MaestroBitcoinDataProvider.ts` | Concrete HTTP client against Maestro’s REST API.                                                 |
+| `providers/StubBitcoinDataProvider.ts`    | In-memory mock that returns deterministic data for unit tests.                                   |
+| `providers/BlockchainInputResolver.ts`    | Helper that maps a (txid, vout) pair to a full UTxO by calling the provider.                     |
+| **tx-builder/**                           | Everything needed to construct a PSBT ready for signing.                                         |
+| `tx-builder/TransactionBuilder.ts`        | Accepts outputs, change address, selector, builds PSBT, estimates vBytes & fee.                  |
+| `tx-builder/utils.ts`                     | Constants & helpers specific to size/fee calculation inside the builder.                         |
+| **wallet/**                               | Stateful, observable wallet core and signer.                                                     |
+| `wallet/BitcoinWallet.ts`                 | Polls provider, maintains `balance$`, `utxos$`, history & pending TXs via RxJS.                  |
+| `wallet/BitcoinSigner.ts`                 | Thin wrapper around `@bitcoinerlab/secp256k1` for PSBT input signing + key zeroisation.          |
+| `index.ts`                                | Package entry point.                                                                             |
 
 ## **High Level Overview**
 
 ### Common
 
 Handles all deterministic key derivation (BIP-32, Electrum), address transformation, and Taproot tweaking. It is strictly pure code with no network or disk I/O. It contains some common types shared across all other modules.
 
-
 ### Provider
 
 A thin abstraction (BlockchainDataProvider) encodes everything the wallet needs from a chain service: block tip, UTXOs, mempool, fee estimates, and broadcast. The provider isolates all network I/O and normalises raw REST/RPC responses into the package’s own types (BlockInfo, UTxO, TransactionHistoryEntry, …).
@@ -75,5 +73,3 @@ This module provides:
 - **Input** selection Extension point for input selection, comes with a GreedyInputSelector that implements a simple, deterministic algorithm.
 - **Builder** TransactionBuilder composes PSBTs, computes vBytes, and enforces dust rules.
 - **Signer** BitcoinSigner wraps @bitcoinerlab/secp256k1, signs each PSBT input, and scrubs the private key from memory.
-
-
@@ -1,4 +1,4 @@
 export const INPUT_SIZE = 68;
-export const OUTPUT_SIZE = 34;
+export const OUTPUT_SIZE = 31;
 export const TRANSACTION_OVERHEAD = 10;
 export const DUST_THRESHOLD = 546;
@@ -6,16 +6,15 @@ import {
   validateBitcoinAddress,
   AddressValidationResult,
   UnsignedTransaction,
-  isP2trAddress
+  isP2trAddress,
+  INPUT_SIZE,
+  OUTPUT_SIZE,
+  TRANSACTION_OVERHEAD
 } from '../common';
 import { UTxO } from '../providers';
 import { payments, script, Psbt } from 'bitcoinjs-lib';
 import * as bitcoin from 'bitcoinjs-lib';
 
-const INPUT_SIZE = 68;
-const OUTPUT_SIZE = 34;
-const TRANSACTION_OVERHEAD = 10;
-
 /**
  * A class to build Bitcoin transactions using a flexible input and output management system.
  */

@@ -3,7 +3,6 @@ import {
   BlockchainDataProvider,
   BlockchainInputResolver,
   BlockInfo,
-  FeeEstimationMode,
   InputResolver,
   TransactionHistoryEntry,
   UTxO
@@ -25,6 +24,7 @@ import * as bitcoin from 'bitcoinjs-lib';
 import * as ecc from '@bitcoinerlab/secp256k1';
 import isEqual from 'lodash/isEqual';
 import { historyEntryFromRawTx } from '../tx-builder/utils';
+import { FeeMarketProvider } from './FeeMarketProvider';
 
 bitcoin.initEccLib(ecc);
 
@@ -91,6 +91,7 @@ export class BitcoinWallet {
   private pollController$: Observable<boolean>;
   private logger: Logger;
   private inputResolver: InputResolver;
+  private readonly feeMarketProvider: FeeMarketProvider;
 
   public syncStatus: SyncStatus;
 
@@ -107,6 +108,7 @@ export class BitcoinWallet {
   // eslint-disable-next-line max-params
   constructor(
     provider: BlockchainDataProvider,
+    feeMarketProvider: FeeMarketProvider,
     pollInterval = 30_000,
     historyDepth = 20,
     info: BitcoinWalletInfo,
@@ -133,6 +135,7 @@ export class BitcoinWallet {
 
     // TODO: Allow this to be injected.
     this.inputResolver = new BlockchainInputResolver(provider);
+    this.feeMarketProvider = feeMarketProvider;
 
     const networkKeys = getNetworkKeys(info, network);
     const extendedAccountPubKey = networkKeys.nativeSegWit;
@@ -175,46 +178,7 @@ export class BitcoinWallet {
    * Fetches the current fee market for estimating transaction fees.
    */
   public async getCurrentFeeMarket(): Promise<EstimatedFees> {
-    try {
-      if (this.network === Network.Testnet) {
-        return {
-          fast: {
-            feeRate: 0.000_025,
-            targetConfirmationTime: 1
-          },
-          standard: {
-            feeRate: 0.000_015,
-            targetConfirmationTime: 3
-          },
-          slow: {
-            feeRate: 0.000_01,
-            targetConfirmationTime: 6
-          }
-        };
-      }
-
-      const fastEstimate = await this.provider.estimateFee(1, FeeEstimationMode.Conservative);
-      const standardEstimate = await this.provider.estimateFee(3, FeeEstimationMode.Conservative);
-      const slowEstimate = await this.provider.estimateFee(6, FeeEstimationMode.Conservative);
-
-      return {
-        fast: {
-          feeRate: fastEstimate.feeRate,
-          targetConfirmationTime: fastEstimate.blocks * 10 * 60
-        },
-        standard: {
-          feeRate: standardEstimate.feeRate,
-          targetConfirmationTime: standardEstimate.blocks * 10 * 60
-        },
-        slow: {
-          feeRate: slowEstimate.feeRate,
-          targetConfirmationTime: slowEstimate.blocks * 10 * 60
-        }
-      };
-    } catch (error) {
-      this.logger.error('Failed to fetch fee market:', error);
-      throw error;
-    }
+    return this.feeMarketProvider.getFeeMarket();
   }
 
   /**

@@ -0,0 +1,16 @@
+import { EstimatedFees } from '../wallet/BitcoinWallet';
+
+/**
+ * Interface for providing a fee estimation strategy.
+ *
+ * Implementations of this interface are responsible for retrieving
+ * current fee market data from a source and returning a normalized fee structure.
+ */
+export interface FeeMarketProvider {
+  /**
+   * Retrieves current fee estimates.
+   *
+   * @returns A promise resolving to the latest fee estimates.
+   */
+  getFeeMarket(): Promise<EstimatedFees>;
+}
@@ -0,0 +1,47 @@
+/* eslint-disable no-magic-numbers */
+import { EstimatedFees } from './BitcoinWallet';
+import { FeeEstimationMode } from '../providers/BitcoinDataProvider';
+import { MaestroBitcoinDataProvider } from '../providers/MaestroBitcoinDataProvider';
+import { Network } from '../common/network';
+import { Logger } from 'ts-log';
+import { FeeMarketProvider } from './FeeMarketProvider';
+import { DEFAULT_MARKETS } from './constants';
+
+export class MaestroFeeMarketProvider implements FeeMarketProvider {
+  constructor(
+    private readonly provider: MaestroBitcoinDataProvider,
+    private readonly logger: Logger,
+    private readonly network: Network = Network.Mainnet
+  ) {}
+
+  async getFeeMarket(): Promise<EstimatedFees> {
+    try {
+      if (this.network === Network.Testnet) {
+        return DEFAULT_MARKETS;
+      }
+
+      const fastEstimate = await this.provider.estimateFee(1, FeeEstimationMode.Economical);
+      const standardEstimate = await this.provider.estimateFee(3, FeeEstimationMode.Economical);
+      const slowEstimate = await this.provider.estimateFee(6, FeeEstimationMode.Economical);
+
+      return {
+        fast: {
+          feeRate: fastEstimate.feeRate,
+          targetConfirmationTime: fastEstimate.blocks * 10 * 60
+        },
+        standard: {
+          feeRate: standardEstimate.feeRate,
+          targetConfirmationTime: standardEstimate.blocks * 10 * 60
+        },
+        slow: {
+          feeRate: slowEstimate.feeRate,
+          targetConfirmationTime: slowEstimate.blocks * 10 * 60
+        }
+      };
+    } catch (error) {
+      this.logger.error('Failed to fetch fee market:', error);
+    }
+
+    return DEFAULT_MARKETS;
+  }
+}