chainparams.cpp

// Copyright (c) 2010 Satoshi Nakamoto
// Copyright (c) 2009-present The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <kernel/chainparams.h>

#include <chainparamsseeds.h>
#include <consensus/amount.h>
#include <consensus/merkle.h>
#include <consensus/params.h>
#include <crypto/hex_base.h>
#include <hash.h>
#include <kernel/messagestartchars.h>
#include <primitives/block.h>
#include <primitives/transaction.h>
#include <script/interpreter.h>
#include <script/script.h>
#include <script/verify_flags.h>
#include <uint256.h>
#include <util/chaintype.h>
#include <util/log.h>
#include <util/strencodings.h>

#include <algorithm>
#include <array>
#include <cassert>
#include <cstdint>
#include <cstring>
#include <iterator>
#include <map>
#include <span>
#include <utility>

using namespace util::hex_literals;

static CBlock CreateGenesisBlock(const char* pszTimestamp, const CScript& genesisOutputScript, uint32_t nTime, uint32_t nNonce, uint32_t nBits, int32_t nVersion, const CAmount& genesisReward)
{
    CMutableTransaction txNew;
    txNew.version = 1;
    txNew.vin.resize(1);
    txNew.vout.resize(1);
    txNew.vin[0].scriptSig = CScript() << 486604799 << CScriptNum(4) << std::vector<unsigned char>((const unsigned char*)pszTimestamp, (const unsigned char*)pszTimestamp + strlen(pszTimestamp));
    txNew.vout[0].nValue = genesisReward;
    txNew.vout[0].scriptPubKey = genesisOutputScript;

    CBlock genesis;
    genesis.nTime    = nTime;
    genesis.nBits    = nBits;
    genesis.nNonce   = nNonce;
    genesis.nVersion = nVersion;
    genesis.vtx.push_back(MakeTransactionRef(std::move(txNew)));
    genesis.hashPrevBlock.SetNull();
    genesis.hashMerkleRoot = BlockMerkleRoot(genesis);
    return genesis;
}

/**
 * Build the genesis block. Note that the output of its generation
 * transaction cannot be spent since it did not originally exist in the
 * database.
 *
 * CBlock(hash=000000000019d6, ver=1, hashPrevBlock=00000000000000, hashMerkleRoot=4a5e1e, nTime=1231006505, nBits=1d00ffff, nNonce=2083236893, vtx=1)
 *   CTransaction(hash=4a5e1e, ver=1, vin.size=1, vout.size=1, nLockTime=0)
 *     CTxIn(COutPoint(000000, -1), coinbase 04ffff001d0104455468652054696d65732030332f4a616e2f32303039204368616e63656c6c6f72206f6e206272696e6b206f66207365636f6e64206261696c6f757420666f722062616e6b73)
 *     CTxOut(nValue=50.00000000, scriptPubKey=0x5F1DF16B2B704C8A578D0B)
 *   vMerkleTree: 4a5e1e
 */
static CBlock CreateGenesisBlock(uint32_t nTime, uint32_t nNonce, uint32_t nBits, int32_t nVersion, const CAmount& genesisReward)
{
    const char* pszTimestamp = "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks";
    const CScript genesisOutputScript = CScript() << "04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f"_hex << OP_CHECKSIG;
    return CreateGenesisBlock(pszTimestamp, genesisOutputScript, nTime, nNonce, nBits, nVersion, genesisReward);
}

void CChainParams::ApplyDeploymentOptions(const DeploymentOptions& opts)
{
    for (const auto& [dep, height] : opts.activation_heights) {
        switch (dep) {
        case Consensus::BuriedDeployment::DEPLOYMENT_SEGWIT:
            consensus.SegwitHeight = int{height};
            break;
        case Consensus::BuriedDeployment::DEPLOYMENT_HEIGHTINCB:
            consensus.BIP34Height = int{height};
            break;
        case Consensus::BuriedDeployment::DEPLOYMENT_DERSIG:
            consensus.BIP66Height = int{height};
            break;
        case Consensus::BuriedDeployment::DEPLOYMENT_CLTV:
            consensus.BIP65Height = int{height};
            break;
        case Consensus::BuriedDeployment::DEPLOYMENT_CSV:
            consensus.CSVHeight = int{height};
            break;
        }
    }

    for (const auto& [deployment_pos, version_bits_params] : opts.version_bits_parameters) {
        consensus.vDeployments[deployment_pos].nStartTime = version_bits_params.start_time;
        consensus.vDeployments[deployment_pos].nTimeout = version_bits_params.timeout;
        consensus.vDeployments[deployment_pos].min_activation_height = version_bits_params.min_activation_height;
    }
}

/**
 * Main network on which people trade goods and services.
 */
class CMainParams : public CChainParams {
public:
    CMainParams(const MainNetOptions& opts) {
        m_chain_type = ChainType::MAIN;
        consensus.signet_blocks = false;
        consensus.signet_challenge.clear();
        consensus.nSubsidyHalvingInterval = 210000;
        consensus.script_flag_exceptions.emplace( // BIP16 exception
            uint256{"00000000000002dc756eebf4f49723ed8d30cc28a5f108eb94b1ba88ac4f9c22"}, SCRIPT_VERIFY_NONE);
        consensus.script_flag_exceptions.emplace( // Taproot exception
            uint256{"0000000000000000000f14c35b2d841e986ab5441de8c585d5ffe55ea1e395ad"}, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS);
        consensus.BIP34Height = 227931;
        consensus.BIP34Hash = uint256{"000000000000024b89b42a942fe0d9fea3bb44ab7bd1b19115dd6a759c0808b8"};
        consensus.BIP65Height = 388381; // 000000000000000004c2b624ed5d7756c508d90fd0da2c7c679febfa6c4735f0
        consensus.BIP66Height = 363725; // 00000000000000000379eaa19dce8c9b722d46ae6a57c2f1a988119488b50931
        consensus.CSVHeight = 419328; // 000000000000000004a1b34462cb8aeebd5799177f7a29cf28f2d1961716b5b5
        consensus.SegwitHeight = 481824; // 0000000000000000001c8018d9cb3b742ef25114f27563e3fc4a1902167f9893
        consensus.MinBIP9WarningHeight = 711648; // taproot activation height + miner confirmation window
        consensus.powLimit = uint256{"00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff"};
        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
        consensus.nPowTargetSpacing = 10 * 60;
        consensus.fPowAllowMinDifficultyBlocks = false;
        consensus.enforce_BIP94 = false;
        consensus.fPowNoRetargeting = false;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].threshold = 1815; // 90%
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].period = 2016;

        ApplyDeploymentOptions(opts.dep_opts);

        consensus.nMinimumChainWork = uint256{"0000000000000000000000000000000000000001128750f82f4c366153a3a030"};
        consensus.defaultAssumeValid = uint256{"00000000000000000000ccebd6d74d9194d8dcdc1d177c478e094bfad51ba5ac"}; // 938343

        /**
         * The message start string is designed to be unlikely to occur in normal data.
         * The characters are rarely used upper ASCII, not valid as UTF-8, and produce
         * a large 32-bit integer with any alignment.
         */
        pchMessageStart[0] = 0xf9;
        pchMessageStart[1] = 0xbe;
        pchMessageStart[2] = 0xb4;
        pchMessageStart[3] = 0xd9;
        nDefaultPort = 8333;
        nPruneAfterHeight = 100000;
        m_assumed_blockchain_size = 856;
        m_assumed_chain_state_size = 14;

        genesis = CreateGenesisBlock(1231006505, 2083236893, 0x1d00ffff, 1, 50 * COIN);
        consensus.hashGenesisBlock = genesis.GetHash();
        assert(consensus.hashGenesisBlock == uint256{"000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"});
        assert(genesis.hashMerkleRoot == uint256{"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"});

        // Note that of those which support the service bits prefix, most only support a subset of
        // possible options.
        // This is fine at runtime as we'll fall back to using them as an addrfetch if they don't support the
        // service bits we want, but we should get them updated to support all service bits wanted by any
        // release ASAP to avoid it where possible.
        vSeeds.emplace_back("dnsseed.bluematt.me."); // Matt Corallo, only supports x9
        vSeeds.emplace_back("seed.bitcoin.jonasschnelli.ch."); // Jonas Schnelli, only supports x1, x5, x9, and xd
        vSeeds.emplace_back("seed.btc.petertodd.net."); // Peter Todd, only supports x1, x5, x9, and xd
        vSeeds.emplace_back("seed.bitcoin.sprovoost.nl."); // Sjors Provoost
        vSeeds.emplace_back("dnsseed.emzy.de."); // Stephan Oeste
        vSeeds.emplace_back("seed.bitcoin.wiz.biz."); // Jason Maurice
        vSeeds.emplace_back("seed.mainnet.achownodes.xyz."); // Ava Chow, only supports x1, x5, x9, x49, x809, x849, xd, x400, x404, x408, x448, xc08, xc48, x40c

        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,0);
        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,5);
        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,128);
        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x88, 0xB2, 0x1E};
        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x88, 0xAD, 0xE4};

        bech32_hrp = "bc";

        vFixedSeeds = std::vector<uint8_t>(std::begin(chainparams_seed_main), std::end(chainparams_seed_main));

        fDefaultConsistencyChecks = false;
        m_is_mockable_chain = false;

        m_assumeutxo_data = {
            {
                .height = 840'000,
                .hash_serialized = AssumeutxoHash{uint256{"a2a5521b1b5ab65f67818e5e8eccabb7171a517f9e2382208f77687310768f96"}},
                .m_chain_tx_count = 991032194,
                .blockhash = uint256{"0000000000000000000320283a032748cef8227873ff4872689bf23f1cda83a5"},
            },
            {
                .height = 880'000,
                .hash_serialized = AssumeutxoHash{uint256{"dbd190983eaf433ef7c15f78a278ae42c00ef52e0fd2a54953782175fbadcea9"}},
                .m_chain_tx_count = 1145604538,
                .blockhash = uint256{"000000000000000000010b17283c3c400507969a9c2afd1dcf2082ec5cca2880"},
            },
            {
                .height = 910'000,
                .hash_serialized = AssumeutxoHash{uint256{"4daf8a17b4902498c5787966a2b51c613acdab5df5db73f196fa59a4da2f1568"}},
                .m_chain_tx_count = 1226586151,
                .blockhash = uint256{"0000000000000000000108970acb9522ffd516eae17acddcb1bd16469194a821"},
            },
            {
                .height = 935'000,
                .hash_serialized = AssumeutxoHash{uint256{"e4b90ef9eae834f56c4b64d2d50143cee10ad87994c614d7d04125e2a6025050"}},
                .m_chain_tx_count = 1305397408,
                .blockhash = uint256{"0000000000000000000147034958af1652b2b91bba607beacc5e72a56f0fb5ee"},
            }
        };

        chainTxData = ChainTxData{
            // Data from RPC: getchaintxstats 4096 00000000000000000000ccebd6d74d9194d8dcdc1d177c478e094bfad51ba5ac
            .nTime    = 1772055173,
            .tx_count = 1315805869,
            .dTxRate  = 5.40111006496122,
        };

        // Generated by headerssync-params.py on 2026-02-25.
        m_headers_sync_params = HeadersSyncParams{
            .commitment_period = 641,
            .redownload_buffer_size = 15218, // 15218/641 = ~23.7 commitments
        };
    }
};

/**
 * Testnet (v3): public test network which is reset from time to time.
 */
class CTestNetParams : public CChainParams {
public:
    CTestNetParams(const TestNetOptions& opts) {
        m_chain_type = ChainType::TESTNET;
        consensus.signet_blocks = false;
        consensus.signet_challenge.clear();
        consensus.nSubsidyHalvingInterval = 210000;
        consensus.script_flag_exceptions.emplace( // BIP16 exception
            uint256{"00000000dd30457c001f4095d208cc1296b0eed002427aa599874af7a432b105"}, SCRIPT_VERIFY_NONE);
        consensus.BIP34Height = 21111;
        consensus.BIP34Hash = uint256{"0000000023b3a96d3484e5abb3755c413e7d41500f8e2a5c3f0dd01299cd8ef8"};
        consensus.BIP65Height = 581885; // 00000000007f6655f22f98e72ed80d8b06dc761d5da09df0fa1dc4be4f861eb6
        consensus.BIP66Height = 330776; // 000000002104c8c45e99a8853285a3b592602a3ccde2b832481da85e9e4ba182
        consensus.CSVHeight = 770112; // 00000000025e930139bac5c6c31a403776da130831ab85be56578f3fa75369bb
        consensus.SegwitHeight = 834624; // 00000000002b980fcd729daaa248fd9316a5200e9b367f4ff2c42453e84201ca
        consensus.MinBIP9WarningHeight = 2013984; // taproot activation height + miner confirmation window
        consensus.powLimit = uint256{"00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff"};
        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
        consensus.nPowTargetSpacing = 10 * 60;
        consensus.fPowAllowMinDifficultyBlocks = true;
        consensus.enforce_BIP94 = false;
        consensus.fPowNoRetargeting = false;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].threshold = 1512; // 75%
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].period = 2016;

        ApplyDeploymentOptions(opts.dep_opts);

        consensus.nMinimumChainWork = uint256{"0000000000000000000000000000000000000000000017dde1c649f3708d14b6"};
        consensus.defaultAssumeValid = uint256{"000000007a61e4230b28ac5cb6b5e5a0130de37ac1faf2f8987d2fa6505b67f4"}; // 4842348

        pchMessageStart[0] = 0x0b;
        pchMessageStart[1] = 0x11;
        pchMessageStart[2] = 0x09;
        pchMessageStart[3] = 0x07;
        nDefaultPort = 18333;
        nPruneAfterHeight = 1000;
        m_assumed_blockchain_size = 245;
        m_assumed_chain_state_size = 19;

        genesis = CreateGenesisBlock(1296688602, 414098458, 0x1d00ffff, 1, 50 * COIN);
        consensus.hashGenesisBlock = genesis.GetHash();
        assert(consensus.hashGenesisBlock == uint256{"000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943"});
        assert(genesis.hashMerkleRoot == uint256{"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"});

        vFixedSeeds.clear();
        vSeeds.clear();
        // nodes with support for servicebits filtering should be at the top
        vSeeds.emplace_back("testnet-seed.bitcoin.jonasschnelli.ch.");
        vSeeds.emplace_back("seed.tbtc.petertodd.net.");
        vSeeds.emplace_back("testnet-seed.bluematt.me."); // Just a static list of stable node(s), only supports x9
        vSeeds.emplace_back("seed.testnet.achownodes.xyz."); // Ava Chow, only supports x1, x5, x9, x49, x809, x849, xd, x400, x404, x408, x448, xc08, xc48, x40c

        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);
        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);
        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,239);
        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};
        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};

        bech32_hrp = "tb";

        vFixedSeeds = std::vector<uint8_t>(std::begin(chainparams_seed_test), std::end(chainparams_seed_test));

        fDefaultConsistencyChecks = false;
        m_is_mockable_chain = false;

        m_assumeutxo_data = {
            {
                .height = 2'500'000,
                .hash_serialized = AssumeutxoHash{uint256{"f841584909f68e47897952345234e37fcd9128cd818f41ee6c3ca68db8071be7"}},
                .m_chain_tx_count = 66484552,
                .blockhash = uint256{"0000000000000093bcb68c03a9a168ae252572d348a2eaeba2cdf9231d73206f"},
            },
            {
                .height = 4'840'000,
                .hash_serialized = AssumeutxoHash{uint256{"ce6bb677bb2ee9789c4a1c9d73e6683c53fc20e8fdbedbdaaf468982a0c8db2a"}},
                .m_chain_tx_count = 536078574,
                .blockhash = uint256{"00000000000000f4971a7fb37fbdff89315b69a2e1920c467654a382f0d64786"},
            }
        };

        chainTxData = ChainTxData{
            // Data from RPC: getchaintxstats 4096 000000007a61e4230b28ac5cb6b5e5a0130de37ac1faf2f8987d2fa6505b67f4
            .nTime    = 1772051651,
            .tx_count = 536108416,
            .dTxRate  = 0.02691479016257117,
        };

        // Generated by headerssync-params.py on 2026-02-25.
        m_headers_sync_params = HeadersSyncParams{
            .commitment_period = 673,
            .redownload_buffer_size = 14460, // 14460/673 = ~21.5 commitments
        };
    }
};

/**
 * Testnet (v4): public test network which is reset from time to time.
 */
class CTestNet4Params : public CChainParams {
public:
    CTestNet4Params(const TestNetOptions& opts) {
        m_chain_type = ChainType::TESTNET4;
        consensus.signet_blocks = false;
        consensus.signet_challenge.clear();
        consensus.nSubsidyHalvingInterval = 210000;
        consensus.BIP34Height = 1;
        consensus.BIP34Hash = uint256{};
        consensus.BIP65Height = 1;
        consensus.BIP66Height = 1;
        consensus.CSVHeight = 1;
        consensus.SegwitHeight = 1;
        consensus.MinBIP9WarningHeight = 0;
        consensus.powLimit = uint256{"00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff"};
        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
        consensus.nPowTargetSpacing = 10 * 60;
        consensus.fPowAllowMinDifficultyBlocks = true;
        consensus.enforce_BIP94 = true;
        consensus.fPowNoRetargeting = false;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].threshold = 1512; // 75%
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].period = 2016;

        ApplyDeploymentOptions(opts.dep_opts);

        consensus.nMinimumChainWork = uint256{"0000000000000000000000000000000000000000000009a0fe15d0177d086304"};
        consensus.defaultAssumeValid = uint256{"0000000002368b1e4ee27e2e85676ae6f9f9e69579b29093e9a82c170bf7cf8a"}; // 123613

        pchMessageStart[0] = 0x1c;
        pchMessageStart[1] = 0x16;
        pchMessageStart[2] = 0x3f;
        pchMessageStart[3] = 0x28;
        nDefaultPort = 48333;
        nPruneAfterHeight = 1000;
        m_assumed_blockchain_size = 31;
        m_assumed_chain_state_size = 2;

        const char* testnet4_genesis_msg = "03/May/2024 000000000000000000001ebd58c244970b3aa9d783bb001011fbe8ea8e98e00e";
        const CScript testnet4_genesis_script = CScript() << "000000000000000000000000000000000000000000000000000000000000000000"_hex << OP_CHECKSIG;
        genesis = CreateGenesisBlock(testnet4_genesis_msg,
                testnet4_genesis_script,
                1714777860,
                393743547,
                0x1d00ffff,
                1,
                50 * COIN);
        consensus.hashGenesisBlock = genesis.GetHash();
        assert(consensus.hashGenesisBlock == uint256{"00000000da84f2bafbbc53dee25a72ae507ff4914b867c565be350b0da8bf043"});
        assert(genesis.hashMerkleRoot == uint256{"7aa0a7ae1e223414cb807e40cd57e667b718e42aaf9306db9102fe28912b7b4e"});

        vFixedSeeds.clear();
        vSeeds.clear();
        // nodes with support for servicebits filtering should be at the top
        vSeeds.emplace_back("seed.testnet4.bitcoin.sprovoost.nl."); // Sjors Provoost
        vSeeds.emplace_back("seed.testnet4.wiz.biz."); // Jason Maurice

        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);
        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);
        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,239);
        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};
        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};

        bech32_hrp = "tb";

        vFixedSeeds = std::vector<uint8_t>(std::begin(chainparams_seed_testnet4), std::end(chainparams_seed_testnet4));

        fDefaultConsistencyChecks = false;
        m_is_mockable_chain = false;

        m_assumeutxo_data = {
            {
                .height = 90'000,
                .hash_serialized = AssumeutxoHash{uint256{"784fb5e98241de66fdd429f4392155c9e7db5c017148e66e8fdbc95746f8b9b5"}},
                .m_chain_tx_count = 11347043,
                .blockhash = uint256{"0000000002ebe8bcda020e0dd6ccfbdfac531d2f6a81457191b99fc2df2dbe3b"},
            },
            {
                .height = 120'000,
                .hash_serialized = AssumeutxoHash{uint256{"10b05d05ad468d0971162e1b222a4aa66caca89da2bb2a93f8f37fb29c4794b0"}},
                .m_chain_tx_count = 14141057,
                .blockhash = uint256{"000000000bd2317e51b3c5794981c35ba894ce27d3e772d5c39ecd9cbce01dc8"},
            }
        };

        chainTxData = ChainTxData{
            // Data from RPC: getchaintxstats 4096 0000000002368b1e4ee27e2e85676ae6f9f9e69579b29093e9a82c170bf7cf8a
            .nTime    = 1772013387,
            .tx_count = 14191421,
            .dTxRate  = 0.01848579579528412,
        };

        // Generated by headerssync-params.py on 2026-02-25.
        m_headers_sync_params = HeadersSyncParams{
            .commitment_period = 606,
            .redownload_buffer_size = 16092, // 16092/606 = ~26.6 commitments
        };
    }
};

/**
 * Signet: test network with an additional consensus parameter (see BIP325).
 */
class SigNetParams : public CChainParams {
public:
    explicit SigNetParams(const SigNetOptions& options)
    {
        std::vector<uint8_t> bin;
        vFixedSeeds.clear();
        vSeeds.clear();

        if (!options.challenge) {
            bin = "512103ad5e0edad18cb1f0fc0d28a3d4f1f3e445640337489abb10404f2d1e086be430210359ef5021964fe22d6f8e05b2463c9540ce96883fe3b278760f048f5189f2e6c452ae"_hex_v_u8;
            vFixedSeeds = std::vector<uint8_t>(std::begin(chainparams_seed_signet), std::end(chainparams_seed_signet));
            vSeeds.emplace_back("seed.signet.bitcoin.sprovoost.nl.");
            vSeeds.emplace_back("seed.signet.achownodes.xyz."); // Ava Chow, only supports x1, x5, x9, x49, x809, x849, xd, x400, x404, x408, x448, xc08, xc48, x40c

            consensus.nMinimumChainWork = uint256{"00000000000000000000000000000000000000000000000000000b463ea0a4b8"};
            consensus.defaultAssumeValid = uint256{"00000008414aab61092ef93f1aacc54cf9e9f16af29ddad493b908a01ff5c329"}; // 293175
            m_assumed_blockchain_size = 24;
            m_assumed_chain_state_size = 4;
            chainTxData = ChainTxData{
                // Data from RPC: getchaintxstats 4096 00000008414aab61092ef93f1aacc54cf9e9f16af29ddad493b908a01ff5c329
                .nTime    = 1772055248,
                .tx_count = 28676833,
                .dTxRate  = 0.06736623436338929,
            };
        } else {
            bin = *options.challenge;
            consensus.nMinimumChainWork = uint256{};
            consensus.defaultAssumeValid = uint256{};
            m_assumed_blockchain_size = 0;
            m_assumed_chain_state_size = 0;
            chainTxData = ChainTxData{
                0,
                0,
                0,
            };
            LogInfo("Signet with challenge %s", HexStr(bin));
        }

        if (options.seeds) {
            vSeeds = *options.seeds;
        }

        m_chain_type = ChainType::SIGNET;
        consensus.signet_blocks = true;
        consensus.signet_challenge.assign(bin.begin(), bin.end());
        consensus.nSubsidyHalvingInterval = 210000;
        consensus.BIP34Height = 1;
        consensus.BIP34Hash = uint256{};
        consensus.BIP65Height = 1;
        consensus.BIP66Height = 1;
        consensus.CSVHeight = 1;
        consensus.SegwitHeight = 1;
        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
        consensus.nPowTargetSpacing = 10 * 60;
        consensus.fPowAllowMinDifficultyBlocks = false;
        consensus.enforce_BIP94 = false;
        consensus.fPowNoRetargeting = false;
        consensus.MinBIP9WarningHeight = 0;
        consensus.powLimit = uint256{"00000377ae000000000000000000000000000000000000000000000000000000"};
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].threshold = 1815; // 90%
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].period = 2016;

        ApplyDeploymentOptions(options.dep_opts);

        // message start is defined as the first 4 bytes of the sha256d of the block script
        HashWriter h{};
        h << consensus.signet_challenge;
        uint256 hash = h.GetHash();
        std::copy_n(hash.begin(), 4, pchMessageStart.begin());

        nDefaultPort = 38333;
        nPruneAfterHeight = 1000;

        genesis = CreateGenesisBlock(1598918400, 52613770, 0x1e0377ae, 1, 50 * COIN);
        consensus.hashGenesisBlock = genesis.GetHash();
        assert(consensus.hashGenesisBlock == uint256{"00000008819873e925422c1ff0f99f7cc9bbb232af63a077a480a3633bee1ef6"});
        assert(genesis.hashMerkleRoot == uint256{"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"});

        m_assumeutxo_data = {
            {
                .height = 160'000,
                .hash_serialized = AssumeutxoHash{uint256{"fe0a44309b74d6b5883d246cb419c6221bcccf0b308c9b59b7d70783dbdf928a"}},
                .m_chain_tx_count = 2289496,
                .blockhash = uint256{"0000003ca3c99aff040f2563c2ad8f8ec88bd0fd6b8f0895cfaf1ef90353a62c"},
            },
            {
                .height = 290'000,
                .hash_serialized = AssumeutxoHash{uint256{"97267e000b4b876800167e71b9123f1529d13b14308abec2888bbd2160d14545"}},
                .m_chain_tx_count = 28547497,
                .blockhash = uint256{"0000000577f2741bb30cd9d39d6d71b023afbeb9764f6260786a97969d5c9ac0"},
            }
        };

        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);
        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);
        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,239);
        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};
        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};

        bech32_hrp = "tb";

        fDefaultConsistencyChecks = false;
        m_is_mockable_chain = false;

        // Generated by headerssync-params.py on 2026-02-25.
        m_headers_sync_params = HeadersSyncParams{
            .commitment_period = 620,
            .redownload_buffer_size = 15724, // 15724/620 = ~25.4 commitments
        };
    }
};

/**
 * Regression test: intended for private networks only. Has minimal difficulty to ensure that
 * blocks can be found instantly.
 */
class CRegTestParams : public CChainParams
{
public:
    explicit CRegTestParams(const RegTestOptions& opts)
    {
        m_chain_type = ChainType::REGTEST;
        consensus.signet_blocks = false;
        consensus.signet_challenge.clear();
        consensus.nSubsidyHalvingInterval = 150;
        consensus.BIP34Height = 1; // Always active unless overridden
        consensus.BIP34Hash = uint256();
        consensus.BIP65Height = 1;  // Always active unless overridden
        consensus.BIP66Height = 1;  // Always active unless overridden
        consensus.CSVHeight = 1;    // Always active unless overridden
        consensus.SegwitHeight = 0; // Always active unless overridden
        consensus.MinBIP9WarningHeight = 0;
        consensus.powLimit = uint256{"7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"};
        consensus.nPowTargetTimespan = 24 * 60 * 60; // one day
        consensus.nPowTargetSpacing = 10 * 60;
        consensus.fPowAllowMinDifficultyBlocks = true;
        consensus.enforce_BIP94 = opts.enforce_bip94;
        consensus.fPowNoRetargeting = true;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 0;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].threshold = 108; // 75%
        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].period = 144; // Faster than normal for regtest (144 instead of 2016)

        consensus.nMinimumChainWork = uint256{};
        consensus.defaultAssumeValid = uint256{};

        pchMessageStart[0] = 0xfa;
        pchMessageStart[1] = 0xbf;
        pchMessageStart[2] = 0xb5;
        pchMessageStart[3] = 0xda;
        nDefaultPort = 18444;
        nPruneAfterHeight = opts.fastprune ? 100 : 1000;
        m_assumed_blockchain_size = 0;
        m_assumed_chain_state_size = 0;

        ApplyDeploymentOptions(opts.dep_opts);

        genesis = CreateGenesisBlock(1296688602, 2, 0x207fffff, 1, 50 * COIN);
        consensus.hashGenesisBlock = genesis.GetHash();
        assert(consensus.hashGenesisBlock == uint256{"0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206"});
        assert(genesis.hashMerkleRoot == uint256{"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"});

        vFixedSeeds.clear(); //!< Regtest mode doesn't have any fixed seeds.
        vSeeds.clear();
        vSeeds.emplace_back("dummySeed.invalid.");

        fDefaultConsistencyChecks = true;
        m_is_mockable_chain = true;

        m_assumeutxo_data = {
            {   // For use by unit tests
                .height = 110,
                .hash_serialized = AssumeutxoHash{uint256{"86e9a1205b418b16dde3a18a78c730e30137e28466bda5dbf6b33ab8fc05447c"}},
                .m_chain_tx_count = 111,
                .blockhash = uint256{"135eec25a6fb277884e5824e7aa7d052c4868161c99a5122170b5266f86c273d"},
            },
            {
                // For use by fuzz target src/test/fuzz/utxo_snapshot.cpp
                .height = 200,
                .hash_serialized = AssumeutxoHash{uint256{"17dcc016d188d16068907cdeb38b75691a118d43053b8cd6a25969419381d13a"}},
                .m_chain_tx_count = 201,
                .blockhash = uint256{"385901ccbd69dff6bbd00065d01fb8a9e464dede7cfe0372443884f9b1dcf6b9"},
            },
            {
                // For use by test/functional/feature_assumeutxo.py and test/functional/tool_bitcoin_chainstate.py
                .height = 299,
                .hash_serialized = AssumeutxoHash{uint256{"106b2c56233e378a824cf0d5ff2be42ed32c72f1605c9be288d00942908a40ac"}},
                .m_chain_tx_count = 334,
                .blockhash = uint256{"0c552ced4721c249a389eb9b08cb8da261cd46f0e7b5f9d064d48f3113406853"},
            },
        };

        chainTxData = ChainTxData{
            .nTime = 0,
            .tx_count = 0,
            .dTxRate = 0.001, // Set a non-zero rate to make it testable
        };

        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);
        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);
        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,239);
        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};
        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};

        bech32_hrp = "bcrt";

        // Copied from Testnet4.
        m_headers_sync_params = HeadersSyncParams{
            .commitment_period = 275,
            .redownload_buffer_size = 7017, // 7017/275 = ~25.5 commitments
        };
    }
};

std::unique_ptr<const CChainParams> CChainParams::SigNet(const SigNetOptions& options)
{
    return std::make_unique<const SigNetParams>(options);
}

std::unique_ptr<const CChainParams> CChainParams::RegTest(const RegTestOptions& options)
{
    return std::make_unique<const CRegTestParams>(options);
}

std::unique_ptr<const CChainParams> CChainParams::Main(const MainNetOptions& options)
{
    return std::make_unique<const CMainParams>(options);
}

std::unique_ptr<const CChainParams> CChainParams::TestNet(const TestNetOptions& options)
{
    return std::make_unique<const CTestNetParams>(options);
}

std::unique_ptr<const CChainParams> CChainParams::TestNet4(const TestNetOptions& options)
{
    return std::make_unique<const CTestNet4Params>(options);
}

std::vector<int> CChainParams::GetAvailableSnapshotHeights() const
{
    std::vector<int> heights;
    heights.reserve(m_assumeutxo_data.size());

    for (const auto& data : m_assumeutxo_data) {
        heights.emplace_back(data.height);
    }
    return heights;
}

std::optional<ChainType> GetNetworkForMagic(const MessageStartChars& message)
{
    const auto mainnet_msg = CChainParams::Main()->MessageStart();
    const auto testnet_msg = CChainParams::TestNet()->MessageStart();
    const auto testnet4_msg = CChainParams::TestNet4()->MessageStart();
    const auto regtest_msg = CChainParams::RegTest()->MessageStart();
    const auto signet_msg = CChainParams::SigNet()->MessageStart();

    if (std::ranges::equal(message, mainnet_msg)) {
        return ChainType::MAIN;
    } else if (std::ranges::equal(message, testnet_msg)) {
        return ChainType::TESTNET;
    } else if (std::ranges::equal(message, testnet4_msg)) {
        return ChainType::TESTNET4;
    } else if (std::ranges::equal(message, regtest_msg)) {
        return ChainType::REGTEST;
    } else if (std::ranges::equal(message, signet_msg)) {
        return ChainType::SIGNET;
    }
    return std::nullopt;
}