Bitcoin Core v26.0: P2P/Network Improvements, Pruning Updates, New RPCs & More

• "This release includes new features, various bug fixes and performance improvements, as well as updated translations."
• "Please report bugs using the issue tracker at GitHub."

What's new

P2P and network changes

• Experimental support for the v2 transport protocol defined in
  BIP324 was added.
  • It is off by default, but when enabled using -v2transport- it will
    be negotiated on a per-connection basis with other peers that support it too. The existing v1 transport protocol remains fully supported.
• Nodes with multiple reachable networks will actively try to have at least one outbound connection to each network. This improves individual resistance to eclipse attacks and network level resistance to partition attacks. Users no longer need to perform active measures to ensure being connected to multiple enabled networks.

Pruning

• When using assumeutxo with -prune, the prune budget may be
  exceeded if it is set lower than 1100MB (i.e. MIN_DISK_SPACE_FOR_BLOCK_FILES * 2). Prune
  budget is normally split evenly across each chainstate, unless the resulting prune budget per chainstate is beneath MIN_DISK_SPACE_FOR_BLOCK_FILES in which case that value will be used.

Updated RPCs

• Setting -rpcserialversion=0 is deprecated and will be removed in a future release. It can currently still be used by also adding the -deprecatedrpc=serialversion option.
• The hash_serialized_2 value has been removed from
  gettxoutsetinfo since the value it calculated contained a bug and did not take all data into account. It is superseded by hash_serialized_3 which provides the same functionality but serves the correctly calculated hash.
• New fields transport_protocol_type and session_id were added to
  the getpeerinfo RPC to indicate whether the v2 transport protocol is in use, and if so, what the session id is.
• A new argument v2transport was added to the addnode RPC to
  indicate whether a v2 transaction connection is to be attempted with the peer.
• Miniscript expressions can now be used in Taproot descriptors for all RPCs working with descriptors.
• finalizepsbt is now able to finalize a PSBT with inputs spending Miniscript-compatible Taproot leaves.

New RPCs

• loadtxoutset has been added, which allows loading a UTXO snapshot
  of the format generated by dumptxoutset. Once this snapshot is loaded, its contents will be deserialized into a second chainstate data structure, which is then used to sync to the network's tip.
  • Meanwhile, the original chainstate will complete the initial block
    download process in the background, eventually validating up to the block that the snapshot is based upon.
  • The result is a usable bitcoind instance that is current with the
    network tip in a matter of minutes rather than hours. UTXO snapshot are typically obtained via third-party sources (HTTP, torrent, etc.) which is reasonable since their contents are always checked by hash.
  • You can find more information on this process in the assumeutxo design document.
  • getchainstates has been added to aid in monitoring the assumeutxo
    sync process.
• A new getprioritisedtransactions RPC has been added. It returns a
  map of all fee deltas created by the user with prioritisetransaction, indexed by txid. The map also indicates whether each transaction is present in the mempool.
• A new RPC, submitpackage, has been added. It can be used to submit
  a list of raw hex transactions to the mempool to be evaluated as a package using consensus and mempool policy rules.
  • These policies include package CPFP, allowing a child with high fees
    to bump a parent below the mempool minimum feerate (but not minimum relay feerate).
  • Warning: successful submission does not mean the transactions will
    propagate throughout the network, as package relay is not supported.
  • Not all features are available. The package is limited to a child
    with all of its unconfirmed parents, and no parent may spend the output of another parent. Also, package RBF is not supported. Refer to doc/policy/packages.md for more details on package policies and limitations.
  • This RPC is experimental. Its interface may change.
• A new RPC getaddrmaninfo has been added to view the distribution
  of addresses in the new and tried table of the node's address manager across different networks(ipv4, ipv6, onion, i2p, cjdns). The RPC returns count of addresses in new and tried table as well as their sum for all networks.
• A new importmempool RPC has been added. It loads a valid
  mempool.dat file and attempts to add its contents to the mempool. This can be useful to import mempool data from another node without having to modify the datadir contents and without having to restart the node.
  • Warning: Importing untrusted files is dangerous, especially if
    metadata from the file is taken over.
  • If you want to apply fee deltas, it is recommended to use the
    getprioritisedtransactions and prioritisetransaction RPCs instead of theapply_fee_delta_priority option to avoid double-prioritising any already-prioritised transactions in the mempool.

Updated settings

• bitcoind and bitcoin-qt will now raise an error on startup
  if a datadir that is being used contains a bitcoin.conf file that
  will be ignored, which can happen when a datadir= line is used in
  a bitcoin.conf file. The error message is just a diagnostic intended
  to prevent accidental misconfiguration, and it can be disabled to
  restore the previous behavior of using the datadir while ignoring
  the bitcoin.conf contained in it.
• Passing an invalid -debug, -debugexclude, or -loglevel logging
  configuration option now raises an error, rather than logging an easily missed warning.

Tools and Utilities

• A new bitcoinconsensus_verify_script_with_spent_outputs function
  is available in libconsensus which optionally accepts the spent
  outputs of the transaction being verified.
• A new bitcoinconsensus_SCRIPT_FLAGS_VERIFY_TAPROOT flag is
  available in libconsensus that will verify scripts with the Taproot
  spending rules.

Wallet

• Wallet loading has changed in this release. Wallets with some
  corrupted records that could be previously loaded (with warnings) may no longer load. For example, wallets with corrupted address book entries may no longer load. If this happens, it is recommended load the wallet in a previous version of Bitcoin Core and import the data into a new wallet.
  • Please also report an issue to help improve the software and make
    wallet loading more robust in these cases.
• The gettransaction, listtransactions, listsinceblock RPCs now return the abandoned field for all transactions. Previously, the "abandoned" field was only returned for sent transactions.
• The listdescriptors, decodepsbt and similar RPC methods now show
  h rather than apostrophe (`'`) to indicate hardened derivation. This does not apply when using the private
  parameter, which matches the marker used when descriptor was generated or imported.
• Newly created wallets use h. This change makes it easier to handle descriptor strings manually.
  • E.g. the importdescriptors RPC call is easiest to use h as the
    marker: '["desc": ".../0h/..."]'. With this change listdescriptors will use h, so you can copy-paste the result, without having to add escape characters or switch `'` to 'h' manually.
  • Note that this changes the descriptor checksum.
  • For legacy wallets the hdkeypath field in getaddressinfo is unchanged, nor is the serialization format of wallet dumps.
• The getbalances RPC now returns a lastprocessedblock JSON object
  which contains the wallet's last processed block hash and height at the time the balances were calculated. This result shouldn't be cached because importing new keys could invalidate it.
• The gettransaction RPC now returns a lastprocessedblock JSON
  object which contains the wallet's last processed block hash and height at the time the transaction information was generated.
• The getwalletinfo RPC now returns a lastprocessedblock JSON
  object which contains the wallet's last processed block hash and height at the time the wallet information was generated.
• Coin selection and transaction building now accounts for unconfirmed
  low-feerate ancestor transactions. When it is necessary to spend
  unconfirmed outputs, the wallet will add fees to ensure that the new
  transaction with its ancestors will achieve a mining score equal to
  the feerate requested by the user.
• For RPC methods which accept `options` parameters ((importmulti,
  listunspent, fundrawtransaction, bumpfee, send, sendall, walletcreatefundedpsbt,simulaterawtransaction), it is now possible to pass the options as named parameters without the need for a nested object.
• The deprecatedrpc=walletwarningfield configuration option has been removed. The createwallet, loadwallet, restorewallet and unloadwallet RPCs no longer return the "warning" string field. The same information is provided through the "warnings" field added in v25.0, which returns a JSON array of strings. The "warning" string field was deprecated also in v25.0.
• The signrawtransactionwithkey, signrawtransactionwithwallet, walletprocesspsbt and descriptorprocesspsbt calls now return the more specific RPC_INVALID_PARAMETER error instead of RPC_MISC_ERROR if their sighashtype argument is malformed.
• RPC walletprocesspsbt, and descriptorprocesspsbt return object now includes field hex (if the transaction is complete) containing the serialized transaction suitable for RPC sendrawtransaction.
• It's now possible to use Miniscript inside Taproot leaves for descriptor wallets.

GUI changes

• The transaction list in the GUI no longer provides a special
  category for "payment to yourself". Now transactions that have both
  inputs and outputs that affect the wallet are displayed on separate
  lines for spending and receiving.
• A new menu option allows migrating a legacy wallet based on keys and
  implied output script types stored in BerkeleyDB (BDB) to a modern
  wallet that uses descriptors stored in SQLite.
• The PSBT operations dialog marks outputs paying your own wallet with "own address".
• The ability to create legacy wallets is being removed.

Tests

• Non-standard transactions are now disabled by default on testnet for relay and mempool acceptance. The previous behaviour can be re-enabled by setting -acceptnonstdtxn=1.

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