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29.0 Release Notes draft

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Hennadii Stepanov edited this page Mar 12, 2025 · 27 revisions

Release Notes Draft for v29.0

FIXME Normal sections: How to Upgrade, Compatibility

Notable Changes

P2P and Network Changes

  • Support for UPnP was dropped. If you want to open a port automatically, consider using the -natpmp option instead, which uses PCP or NAT-PMP depending on router support. (#31130)

  • libnatpmp was replaced with a built-in implementation of PCP and NAT-PMP (still enabled using the -natpmp option). This supports automatic IPv4 port forwarding as well as IPv6 pinholing. (#30043)

  • When the -port configuration option is used, the default onion listening port will now be derived to be that port + 1 instead of being set to a fixed value (8334 on mainnet). This re-allows setups with multiple local nodes using different -port and not using -bind, which would lead to a startup failure in v28.0 due to a port collision. Note that a HiddenServicePort manually configured in torrc may need adjustment if used in connection with the -port option. For example, if you are using -port=5555 with a non-standard value and not using -bind=...=onion, previously Bitcoin Core would listen for incoming Tor connections on 127.0.0.1:8334. Now it would listen on 127.0.0.1:5556 (-port plus one). If you configured the hidden service manually in torrc now you have to change it from HiddenServicePort 8333 127.0.0.1:8334 to HiddenServicePort 8333 127.0.0.1:5556, or configure bitcoind with -bind=127.0.0.1:8334=onion to get the previous behavior. (#31223)

  • Upon receiving an orphan transaction (an unconfirmed transaction that spends unknown inputs), the node will attempt to download missing parents from all peers who announced the orphan. This change may increase bandwidth usage but make orphan-handling more reliable. (#31397)

Mempool Policy and Mining Changes

  • Ephemeral dust is a new concept that allows a single dust output in a transaction, provided the transaction is zero fee. In order to spend any unconfirmed outputs from this transaction, the spender must also spend this dust in addition to any other desired outputs. In other words, this type of transaction should be created in a transaction package where the dust is both created and spent simultaneously. (#30239)

  • Due to a bug, the default block reserved weight (4,000 WU) for fixed-size block header, transactions count, and coinbase transaction was reserved twice and could not be lowered. As a result the total reserved weight was always 8,000 WU, meaning that even when specifying a -blockmaxweight higher than the default (even to the max of 4,000,000 WU), the actual block size will never exceed 3,992,000 WU.
    The fix consolidates the reservation into a single place and introduces a new startup option, -blockreservedweight which specifies the reserved weight directly. The default value of -blockreservedweight is set to 8,000 WU to ensure backward compatibility for users who relied on the previous behavior of -blockmaxweight. The minimum value of -blockreservedweight is set to 2,000 WU. Users setting -blockreservedweight below the default should ensure that the total weight of their block header, transaction count, and coinbase transaction does not exceed the reduced value or they may risk mining an invalid block. (#31384)

Updated RPCs

  • The RPC testmempoolaccept response now includes a reject-details field in some cases, similar to the complete error messages returned by sendrawtransaction (#28121)

  • Duplicate blocks submitted with submitblock will now persist their block data even if it was previously pruned. If pruning is activated, the data will be pruned again eventually once the block file it is persisted in is selected for pruning. This is consistent with the behaviour of getblockfrompeer where the block is persisted as well even when pruning. (#31175)

  • getmininginfo now returns nBits and the current target in the target field. It also returns a next object which specifies the height, nBits, difficulty, and target for the next block. (#31583)

  • getblock and getblockheader now return the current target in the target field (#31583)

  • getblockchaininfo and getchainstates now return nBits and the current target in the target field (#31583)

  • the getblocktemplate RPC curtime (BIP22) and mintime (BIP23) fields now account for the timewarp fix proposed in BIP94 on all networks. This ensures that, in the event a timewarp fix softfork activates on mainnet, un-upgraded miners will not accidentally violate the timewarp rule. (#31376, #31600) As a reminder, it's important that any software which uses the getblocktemplate RPC takes these values into account (either curtime or mintime is fine). Relying only on a clock can lead to invalid blocks under some circumstances, especially once a timewarp fix is deployed. (#31600)

New RPCs

  • getdescriptoractivity can be used to find all spend/receive activity relevant to a given set of descriptors within a set of specified blocks. This call can be used with scanblocks to lessen the need for additional indexing programs. (#30708)

Updated REST APIs

  • GET /rest/block/<BLOCK-HASH>.json and GET /rest/headers/<BLOCK-HASH>.json now return the current target in the target field

Updated Settings

  • The maximum allowed value for the -dbcache configuration option has been dropped due to recent UTXO set growth. Note that before this change, large -dbcache values were automatically reduced to 16 GiB (1 GiB on 32 bit systems). (#28358)

  • Handling of negated -noseednode, -nobind, -nowhitebind, -norpcbind, -norpcallowip, -norpcwhitelist, -notest, -noasmap, -norpcwallet, -noonlynet, and -noexternalip options has changed. Previously negating these options had various confusing and undocumented side effects. Now negating them just resets the settings and restores default behaviors, as if the options were not specified.

  • Starting with v28.0, the -mempoolfullrbf startup option was set to default to 1. With widespread adoption of this policy, users no longer benefit from disabling it, so the option has been removed, making full replace-by-fee the standard behavior. (#30592)

  • Setting -upnp will now log a warning and be interpreted as -natpmp. Consider using -natpmp directly instead. (#31130, #31916)

  • As a safety check, Bitcoin core will fail to start when -blockreservedweight init parameter value is lower than 2000 weight units. Bitcoin Core will also fail to start if the -blockmaxweight or -blockreservedweight init parameter exceeds consensus limit of 4,000,000 WU.

  • Passing -debug=0 or -debug=none now behaves like -nodebug: previously set debug categories will be cleared, but subsequent -debug options will still be applied.

  • The default for -rpcthreads has been changed from 4 to 16, and the default for -rpcworkqueue has been changed from 16 to 64. (#31215).

Wallet

GUI Changes

Build System

The build system has been migrated from Autotools to CMake:

  1. The minimum required CMake version is 3.22.
  2. In-source builds are not allowed. When using a subdirectory within the root source tree as a build directory, it is recommended that its name includes the substring "build".
  3. CMake variables may be used to configure the build system. See Autotools to CMake Options Mapping for details.
  4. For single-configuration generators, the default build configuration (CMAKE_BUILD_TYPE) is "RelWithDebInfo". However, for the "Release" configuration, CMake defaults to the compiler optimization flag -O3, which has not been extensively tested with Bitcoin Core. Therefore, the build system replaces it with -O2.
  5. By default, the built executables and libraries are located in the bin/ and lib/ subdirectories of the build directory.
  6. The build system supports component‐based installation. The names of the installable components coincide with the build target names. For example:
cmake -B build
cmake --build build --target bitcoind
cmake --install build --component bitcoind
  1. If any of the CPPFLAGS, CFLAGS, CXXFLAGS or LDFLAGS environment variables were used in your Autotools-based build process, you should instead use the corresponding CMake variables (APPEND_CPPFLAGS, APPEND_CFLAGS, APPEND_CXXFLAGS and APPEND_LDFLAGS). Alternatively, if you opt to use the dedicated CMAKE_<...>_FLAGS variables, you must ensure that the resulting compiler or linker invocations are as expected.

For more detailed guidance on configuring and using CMake, please refer to the official CMake documentation and CMake’s User Interaction Guide. Additionally, consult platform-specific doc/build-*.md build guides for instructions tailored to your operating system.

Low-Level Changes

Tools and Utilities

  • A new tool utxo_to_sqlite.py converts a compact-serialized UTXO snapshot (as created with the dumptxoutset RPC) to a SQLite3 database. Refer to the script's --help output for more details. (#27432)

Tests

  • The BIP94 timewarp attack mitigation (designed for testnet4) is no longer active on the regtest network. (#31156)

Dependencies

  • MiniUPnPc and libnatpmp have been removed as dependencies (#31130, #30043).

Credits

  • 0xb10c
  • Adlai Chandrasekhar
  • Afanti
  • Alfonso Roman Zubeldia
  • am-sq
  • Andre
  • Andre Alves
  • Anthony Towns
  • Antoine Poinsot
  • Ash Manning
  • Ava Chow
  • Boris Nagaev
  • Brandon Odiwuor
  • brunoerg
  • Chris Stewart
  • Cory Fields
  • costcould
  • Daniel Pfeifer
  • Daniela Brozzoni
  • David Gumberg
  • dergoegge
  • epysqyli
  • espi3
  • Eval EXEC
  • Fabian Jahr
  • fanquake
  • furszy
  • Gabriele Bocchi
  • glozow
  • Greg Sanders
  • Gutflo
  • Hennadii Stepanov
  • Hodlinator
  • i-am-yuvi
  • ion-
  • ismaelsadeeq
  • Jadi
  • James O'Beirne
  • Jeremy Rand
  • Jon Atack
  • jurraca
  • Kay
  • kevkevinpal
  • l0rinc
  • laanwj
  • Larry Ruane
  • Lőrinc
  • Maciej S. Szmigiero
  • Mackain
  • MarcoFalke
  • marcofleon
  • Marnix
  • Martin Leitner-Ankerl
  • Martin Saposnic
  • Martin Zumsande
  • Matthew Zipkin
  • Max Edwards
  • Michael Dietz
  • naiyoma
  • Nicola Leonardo Susca
  • omahs
  • pablomartin4btc
  • Pieter Wuille
  • Randall Naar
  • RiceChuan
  • rkrux
  • Roman Zeyde
  • Ryan Ofsky
  • Sebastian Falbesoner
  • secp512k2
  • Sergi Delgado Segura
  • Simon
  • Sjors Provoost
  • stickies-v
  • Suhas Daftuar
  • tdb3
  • TheCharlatan
  • tianzedavid
  • Torkel Rogstad
  • Vasil Dimov
  • wgyt
  • willcl-ark
  • yancy

As well as to everyone that helped with translations on Transifex.

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