Bitcoin Core 32 can stall multisig signing on older nodes as fix slips to next patch

Bitcoin Core 32.0’s graphical wallet can interrupt co-signing with older Core wallets by creating transaction files those versions cannot import, according to a user report. The compatibility issue has moved to the 32.1 milestone, while a proposed GUI fix remains open.

In the Oct. 14 report, user mjdietzx described an unsupported-version decoding error when loading a file created by the new graphical wallet into pre-32 Core. The GUI offered no version selector. That can stop a workflow in which a newer Core wallet prepares a transaction and an older Core wallet supplies another signature.

The mismatch concerns the Partially Signed Bitcoin Transaction, or PSBT, format used to exchange transaction data during signing. The new GUI creates PSBT v2. BIP 370 allows v2 to add inputs and outputs after creation when its modification flags permit, but deliberately makes it incompatible with software that only handles v0.

The report also describes v2 output being rejected by joinpsbts, an RPC that accepts only v0 files. External signing software may face similar trouble if it lacks v2 support.

GitHub shows a verified, signed v32.0 final source tag dated Oct. 21. The official download page still advertised 31.1 when checked Oct. 22, so the tag alone should not be read as confirmation that 32.0 binaries are available.

Maintainer fanquake moved the compatibility issue to 32.1 on Oct. 21, saying 32.0 was overdue and there was not yet a fix ready to backport. Pull request 36539 proposes restoring GUI-created PSBTs to v0 and remained open at the Oct. 22 check. CryptoSlate’s September release-candidate coverage had flagged the RPC format-default changes; the GUI fix’s deferral is the later development.

How to avoid the PSBT format mismatch

Mixed-version co-signers can choose v0 when creating the file through Core 32’s RPC interface, using psbt_version=0 with walletcreatefundedpsbt or createpsbt. The v32.0 functional tests cover both format versions and check that the decoded output matches the requested version.

BIP 370 also permits converting an existing v2 PSBT to v0 by reconstructing its unsigned transaction, but does not itself provide an operator command.