v32.0 Release Notes Draft

New RPCs

• A new exportwatchonlywallet RPC creates a watchonly wallet file from an existing descriptor wallet. The exported file contains the wallet's public descriptors (with derived key caches where needed), transactions, and address book data, but no private keys. It can be imported on another node using the existing restorewallet RPC. (32489)
• A new exportasmap RPC writes the ASMap data embedded at build time to a file. (33920)

Performance Improvements

• Block validation can now prefetch input prevouts from the chainstate database in parallel while connecting blocks, speeding up validation when prevouts need to be read from disk. A new -prevoutfetchthreads=<n> option controls the number of prefetch worker threads. The default is 8 threads, up to a maximum of 16; set it to 0 to disable parallel prefetching. (#35295)

Updated RPCs

• createpsbt, walletcreatepsbt, converttopsbt, and psbtbumpfee will now default to creating version 2 PSBTs. An optional psbt_version argument is added to these RPCs which allows specifying the version of PSBT to create. (#21283)

• 'taproot' has been removed from 'getdeploymentinfo' because its historical activation height is no longer used anywhere in the codebase. Applications that rely on deployments.taproot to detect Taproot support should either assume Taproot to be always active (since Bitcoin Core v24.0), or check for TAPROOT in the script_flags array returned by getdeploymentinfo (since Bitcoin Core v31.0). (26201)

• Bitcoin Core now reports a debug message explaining why transaction inputs are non-standard. This information is now returned in the responses of the transaction-sending RPCs submitpackage, sendrawtransaction, and testmempoolaccept, and is also logged to debug.log (if mempoolrej + debug category is enabled) when such transactions are received over the P2P network. This does not change the existing error code bad-txns-nonstandard-inputs, but instead adds additional debug information to it. (29060)

• The dumptxoutset RPC now supports writing to a named pipe on UNIX-like systems (see mkfifo(1) and mkfifo(3) man pages). This allows the raw UTXO set data to be consumed directly by another process (e.g., the contrib/utxo-tools/utxo_to_sqlite.py conversion script) without first writing it to disk. (31560)

• Mempool RPCs (getrawmempool, getmempoolentry, testmempoolaccept, submitpackage) now include an additional field vsize_adjusted (which is the sigop-adjusted virtual size used for policy) and vsize_bip141 (which represents the raw BIP141 virtual size). While vsize is marked as DEPRECATED, it was previously erroneously described as the BIP 141 vsize, but is actually sigops-adjusted vsize. Use vsize_bip141 to actually get that behavior or switch to the explicit vsize_adjusted for retained behavior. (32800)

• getrawtransaction RPC now includes an additional field vsize_adjusted, which is the sigop-adjusted virtual size if the transaction is in the mempool. (32800)

• The getblockchaininfo RPC now exposes progress for background validation if the assumeutxo feature is used. Once a node has synced from snapshot to tip, verificationprogress returns 1.0 and initialblockdownload false even though the node may still be validating blocks in the background. A new object, backgroundvalidation, provides details about the snapshot being validated, including snapshot height, number of blocks processed, best block hash, chainwork, median time, and verification progress. (33259)

• getbalances now includes a nonmempool field under mine, reporting the net balance of wallet transactions that are not in the mempool (e.g. due to too low a feerate, too many unconfirmed ancestors, or a too-large OP_RETURN output). This value is always negative, and is typically an over-estimate since it accounts for coins being spent but not for change outputs returning to the wallet (which are also outside the mempool). Without this field, funds involved in non-mempool transactions could appear to go missing from the wallet balance. (#33671)

• The estimatesmartfee RPC now combines two fee rate estimators: the existing block policy fee rate estimator and a new mempool fee rate estimator. (#34075)

• The new mempool fee rate estimator produces conservative and economical fee rate estimates from the current contents of the mempool. It only produces a fee rate estimate when recent blocks indicate a healthy mempool, and falls back to the higher of the minimum relay fee rate and the current mempool minimum fee rate when the mempool is too sparse. Its statistics are persisted to fees/mempool_policy_estimator.dat and reloaded on startup. estimatesmartfee returns the lower of the two fee rate estimators' results, so the mempool fee rate estimator can only lower the block policy fee rate estimate. (#34075)

• The combined estimate requires both estimators to succeed. If the mempool fee rate estimator cannot produce an estimate, for example, while the mempool is still loading, when too few recent blocks have been observed, or when the mempool is suspected to be unhealthy, an error is returned. (#34075)

• estimatesmartfee accepts an options object with fee_rate_estimator. Recognized values are "none" (the default, combined behavior described above), "block_policy" (use only the block policy fee rate estimator), and "mempool_policy" (use only the mempool fee rate estimator). All unknown values are treated as "none". Users who want the previous behavior can select the block policy fee rate estimator explicitly. (#34075)

• The options object also accepts verbosity. A verbosity of 2 or higher also returns mempool_health_statistics. (#34075)

• When fee_rate_estimator is "none" and the estimate succeeds, the response also includes an estimator field identifying which fee rate estimator produced the result. (#34075)

• Block policy fee estimator data is now stored in fees/block_policy_estimates.dat. If the new file does not exist, the legacy fee_estimates.dat file is moved to the new path during startup. If both files exist, the legacy file is removed. (#34075)

• Wallet fee rate estimation uses the default combined estimate. (#34075)

• The -deprecatedrpc=startingheight configuration option has been removed. The getpeerinfo RPC no longer returns the startingheight field, which was previously deprecated in v31.0. (#34796)

• The migratewallet RPC now gives the option to not load the descriptor wallet after migrating it from a legacy wallet. This will now allow pruned nodes to migrate a wallet out of sync below the pruning height. Note that to use the new wallet it must be loaded to a full node anyway. (#35266)

• The getprivatebroadcastinfo and abortprivatebroadcast RPCs now return an error -32601, "Method not found", when -privatebroadcast is not enabled at startup. (#35267)

• gettransaction, listtransactions, and listsinceblock now have an alternate_wtxids field which lists the wtxids of all transactions that have the same txid. When there is only one known witness variant the field is an empty array, analogous to walletconflicts and mempoolconflicts. (#35501)

• getprivatebroadcastinfo now reports an attempts_remaining field for each transaction. (#35680)

Tools and Utilities

• CLI -addrinfo now returns the full set of known addresses. In previous versions (v22.0 - v30.0) the set of returned addresses was filtered for quality and recency. This was changed since it does not match the logic for selecting peers to connect to, which does not filter. Note: CLI -addrinfo now requires bitcoind v26.0 or later, as it uses the getaddrmaninfo RPC internally. Users querying older, unmaintained node versions would need to use an older bitcoin-cli version. (#26988)
• A new bitcoin-util getchainparams command returns hardcoded details about the selected chain. (#35610)

Wallet

• A new RPC addhdkey is added which allows a BIP 32 extended key to be added to the wallet without needing to import it as part of a separate descriptor. This key will not be used to produce any output scripts unless it is explicitly imported as part of a separate descriptor independent of the addhdkey RPC. (29136)
• The Offline Signing Tutorial has been updated to use exportwatchonlywallet for setting up the online watch-only wallet, replacing the previous manual descriptor import workflow. (32489)
• A new derivehdkey RPC is available to obtain an xpub or xprv for a derivation path with at least one hardened step from an HD key known to the wallet. This can be used to coordinate a multisig setup, where each signer shares an xpub using a different derivation path than the default single-signature descriptors. The example in doc/multisig-tutorial.md is updated to use this RPC. (32784)
• The fee_reason field returned by wallet transaction creation RPCs now reports the reason the wallet selected the fee rate (fee rate estimator, mempool minimum, fallback, or minimum required) instead of the block policy fee rate estimator's internal threshold details. Those details remain available in the block policy fee rate estimator debug log. (#34075)
• Wallets names that are relative paths including .. and . elements, and wallets named / are no longer allowed. Any users that depended on this behavior can instead use absolute paths to their wallet or move their wallet to a safer path. (#34544)
• The send and sendall RPCs are no longer marked as experimental. (#35601)
• The fundrawtransaction RPC no longer accepts a boolean as the second positional argument. This silent no-op fallback was removed and the argument is now fully type checked. Passing a boolean will raise an error. (#35836)
• On non-Windows systems, an authenticated RPC caller allowed to create wallets could execute arbitrary commands as the node process account when -walletnotify was configured, by crafting a wallet name with regex replacement characters. Wallet notification placeholder replacement now treats wallet names literally. (#36048)
• The removeprunedfunds RPC has been deprecated and will be removed in the next major release. In order to continue using it, bitcoind must be started with the -deprecatedrpc=removeprunedfunds option. (#35605)

Build System

• The undocumented BITCOIN_GENBUILD_NO_GIT environment variable is no longer required and has been removed. The build system now automatically detects when it is being built from a source archive or as a subproject of a git-aware parent project and skips git metadata fetching. Users who need to disable git execution explicitly can still do so by configuring with -DCMAKE_DISABLE_FIND_PACKAGE_Git=ON. (#32220)

P2P and network changes

• Tor hidden services that are created automatically by Bitcoin Core will have PoW defenses enabled if the Tor daemon supports that. (#33414)

• To reduce memory and CPU usage during periods of high transaction volume, rate-limiting of outgoing transaction relay has been changed to use a global backlog instead of being done on a per-peer basis. The default rate-limit remains as 14 tx/s (boosted by 2.5x for outbound peers), though this can be changed via the -txsendrate configuration option. An additional bandwidth rate-limit has also been introduced at 12MB of transactions per 10 minutes, with a high burst rate. The size of the global backlog and the token bucket values for the rate limits can be queried via the getnetworkinfo RPC. (#34628)

• Fix a possible leak of the originator's IP address for transactions sent with sendrawtransaction RPC when -privatebroadcast=1. When Bitcoin Core connects to a peer, if that peer has been advertised to support P2P protocol v2, then Bitcoin Core tries to use the v2 protocol and if that fails it retries the connection using the v1 protocol. When the private broadcast is about to send a transaction to an IPv4 or IPv6 peer it overrides the normal proxy selection and forces the connection through the Tor proxy (and thus through the Tor network, protecting the sender's IP address). However if v2 protocol is tried and it fails, then the v1 retry connection would be made disregarding the "override proxy" request, possibly making an IPv4 or IPv6 direct connection. In other words, for this to happen the following must be true:

  1. An IPv4 or IPv6 address has been advertised to the sender, indicating v2 support.
  2. The sender must have Tor configured.
  3. The sender's configuration must be such that connections to IPv4 or IPv6 are made directly (no -proxy= is used for IPv4 or IPv6).
  4. The recipient does not support v2 (the flags from 1. are bogus). (#35319)

• The private-broadcast queue (transactions submitted via sendrawtransaction when -privatebroadcast is enabled and not yet echoed back from the network) is now capped at 10,000 entries. When full, new submissions are rejected. It is up to the caller to inspect the queue via getprivatebroadcastinfo and free up space when stuck via abortprivatebroadcast. (#35406)

• Each transaction sent via private broadcast (-privatebroadcast) is limited to 1,000 send attempts. After reaching the limit, broadcasting stops; call sendrawtransaction again to retry. Transactions that reach the limit remain available through getprivatebroadcastinfo and abortprivatebroadcast. (#35680)

• Support for the legacy ElGamal (type 0) encryption type when creating I2P sessions is being sunset by the I2P network and will be removed from bitcoind on or before v34. Nodes using I2P with versions of Bitcoin Core earlier than v26.1 (PRs #29200, #29209) will soon only be able to connect to other legacy ElGamal I2P peers and will be increasingly isolated from the rest of the network, with a reduced anonymity set. See #35696 for details. (#35696)

• The project is currently considering whether to drop support for CJDNS (see discussion in #36041). Since its introduction in v23.0, it has not gained substantial adoption amongst nodes, and there is some concern about supporting a network with such a low number of peers. (#36202)

• The CJDNS documentation was updated in #34811 to simplify the setup / peer discovery process. (#36202)

Mining

• The IPC mining interface now rejects out-of-range block template options instead of silently clamping them, such as oversized reserved block weight or coinbase sigops limits. (#33966)

• The -blockmaxweight startup option is now rejected when it is lower than -blockreservedweight, instead of being silently clamped. (#33966)

IPC Interface

• BlockTemplate.submitSolution now returns reason and debug rejection details in addition to the boolean result. Clients must regenerate IPC bindings from the updated mining.capnp schema to use the new method. The previous @7 method now returns an error directing clients to update. (#34672)

• BlockTemplate.submitSolution now reports duplicate blocks as failures with reason="duplicate", matching Mining.submitBlock, instead of returning success for duplicate submissions. (#34672)

Logging

• BIP 9 bits 5 to 28 inclusive are now ignored for soft fork signaling, as per BIP 323. We won't warn about unknown deployments when receiving blocks that set any of those bits in their version. (#34779)

REST API

• REST responses now include Cache-Control headers to guide intermediary caches. Immutable responses such as block binary and hex data, block parts, block filters, spent transaction outputs, and block-specific deployment info are marked cacheable for one day. Responses that can change with active chain or node state, as well as errors, are marked no-store. (#34794)

The HTTP server has been rewritten from scratch to replace libevent. (#35182)

The libevent logging category has been removed. Configurations like -debug=libevent or -debugexclude=libevent will log a deprecation warning and be ignored. These configurations will result in an error in a future release.

Certain HTTP edge cases will observe different behavior to be more RFC-compliant:

• Stricter enforcement of maximum headers size (8192 bytes)
• Reject requests with whitespace in header field-names
• "Line Folding" is rejected (whitespace at start of a header line)
• Tolerate % at the end of requested URLs
• Multiple "Content-Length" headers with different values are rejected

A new configuration option -rpcmaxconnections (default 16) limits the number of simultaneously connected HTTP clients to the server. The application will now attempt to reserve file descriptors for the HTTP server sockets. If your system has limited resources, consider using a lower setting.

• Clients attempting to connect from addresses not allowed by the -rpcallowip option (or its default, localhost) will now be immediately disconnected instead of receiving a 403 Forbidden. (#35592)

Mempool

• mempoolfullrbf=1 behaviour has been the default since v28 and the argument has been removed since v29 subsequently. The getmempoolinfo RPC stops returning the deprecated fullrbf key in the response unless the user requests it via the -deprecatedrpc=fullrbf node argument. Also, the bip125-replaceable key is removed from the mempool RPCs responses (because it, too, has been deprecated since v29) unless the user requests it via -deprecatedrpc=bip125 node argument. Affected mempool RPCs are getrawmempool, getmempoolancestors, getmempooldescendants, and getmempoolentry. (#34911)

RPC and Startup Option

• The bip125-replaceable key in the wallet transaction RPCs such as listtransactions, listsinceblock, and gettransaction is marked as deprecated. Users still have the option to retrieve this key by passing the -deprecatedrpc=bip125 startup option. Also, the -walletrbf startup option has been marked as deprecated and will be fully removed in the next release. Using this option emits a warning in the logs. (#34917)

Index

• The transaction index (-txindex) now stores less data on disk; a fully rebuilt index takes less than half the space. The index is backwards compatible, so existing users will not see the space saving unless the index is recreated. To do so, stop the node, delete the <datadir>/indexes/txindex directory, and restart; rebuilding can take up to a few hours depending on hardware. Progress can be monitored using the getindexinfo RPC. Once rebuilt, the index can no longer be read by previous releases, so downgrading will rebuild it again in the old format. When downgrading permanently, delete the <datadir>/indexes/txindex directory first, since previous releases do not reclaim the space used by entries in the new format. (#35531)
• The transaction output spender index (-txospenderindex) now uses less disk space. Existing indexes remain compatible and no action is required. To reclaim the space for data indexed before upgrading, stop the node, delete the <datadir>/indexes/txospenderindex/ directory, and restart with -txospenderindex enabled to rebuild it. (#35634, #35568)

GUI Changes

• The migrate wallet option now allows to disable wallet loading after migrating. It is useful in case the node is pruned and the wallet was created before the pruned height. (#gui/953)
• A menu action has been added to allow creating a watchonly wallet file from an existing descriptor wallet. This option mirrors the exportwatchonlywallet RPC - the exported file can be imported to another node using the Restore Wallet menu action. (872)