Repository: bitcoin/bitcoin
File: src/kernel/chainparams.cpp (C++)

Code before:
            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

            // Hardcoded nodes can be removed once there are more DNS seeds
            vSeeds.emplace_back("178.128.221.177");
            vSeeds.emplace_back("v7ajjeirttkbnt32wpy3c6w3emwnfr3fkla7hpxcfokr3ysd3kqtzmqd.onion:38333");

            consensus.nMinimumChainWork = uint256{"00000000000000000000000000000000000000000000000000000206e86f08e8"};
            consensus.defaultAssumeValid = uint256{"0000000870f15246ba23c16e370a7ffb1fc8a3dcf8cb4492882ed4b0e3d4cd26"}; // 180000
            m_assumed_blockchain_size = 1;
            m_assumed_chain_state_size = 0;
            chainTxData = ChainTxData{
                // Data from RPC: getchaintxstats 4096 0000000870f15246ba23c16e370a7ffb1fc8a3dcf8cb4492882ed4b0e3d4cd26
                .nTime    = 1706331472,
                .tx_count = 2425380,
                .dTxRate  = 0.008277759863833788,
            };
        } 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,
            };
            LogPrintf("Signet with challenge %s\n", 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.fPowNoRetargeting = false;
        consensus.nRuleChangeActivationThreshold = 1815; // 90% of 2016
        consensus.nMinerConfirmationWindow = 2016; // nPowTargetTimespan / nPowTargetSpacing
        consensus.MinBIP9WarningHeight = 0;

Review comment (suggestion):
e40f06acfd090797f14abdc1768d7b96ae4eeed8: one advantage of having already had some mining is that we can set `nMinimumChainWork` shortly before the release (if only so people can test the headers pre-sync behavior).

Code after:
        consensus.BIP34Hash = uint256{};
        consensus.BIP65Height = 1;
        consensus.BIP66Height = 1;
        consensus.CSVHeight = 1;
        consensus.SegwitHeight = 1;
        consensus.MinBIP9WarningHeight = 0;
        consensus.powLimit = uint256S("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
        consensus.nPowTargetSpacing = 10 * 60;
        consensus.fPowAllowMinDifficultyBlocks = true;
        consensus.enforce_BIP94 = true;
        consensus.fPowNoRetargeting = false;
        consensus.nRuleChangeActivationThreshold = 1512; // 75% for testchains
        consensus.nMinerConfirmationWindow = 2016; // nPowTargetTimespan / nPowTargetSpacing
        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

        // Deployment of Taproot (BIPs 340-342)
        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].bit = 2;
        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nStartTime = Consensus::BIP9Deployment::ALWAYS_ACTIVE;
        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].min_activation_height = 0; // No activation delay

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

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

        const char* testnet4_genesis_msg = "03/May/2024 000000000000000000001ebd58c244970b3aa9d783bb001011fbe8ea8e98e00e";
        const CScript testnet4_genesis_script = CScript() << ParseHex("000000000000000000000000000000000000000000000000000000000000000000") << OP_CHECKSIG;
        genesis = CreateGenesisBlock(testnet4_genesis_msg,
                testnet4_genesis_script,
                1714777860,
                393743547,
                0x1d00ffff,
                1,
                50 * COIN);
        consensus.hashGenesisBlock = genesis.GetHash();
        assert(consensus.hashGenesisBlock == uint256S("0x00000000da84f2bafbbc53dee25a72ae507ff4914b867c565be350b0da8bf043"));
        assert(genesis.hashMerkleRoot == uint256S("0x7aa0a7ae1e223414cb807e40cd57e667b718e42aaf9306db9102fe28912b7b4e"));

        vFixedSeeds.clear();