rpc: add prev_txs param to utxoupdatepsbt

bittoby commented at 9:47 pm on April 2, 2026: none

Summary

Add an optional prev_txs parameter to utxoupdatepsbt, allowing callers to provide raw parent transactions whose outputs are not yet in the UTXO set, txindex, or mempool.

Motivation

When constructing presigned transaction chains (e.g. a Lightning commitment transaction at zero fee paired with an anchor spend), the child PSBT cannot be populated because the parent has not been broadcast yet. The existing signrawtransactionwithwallet supports this via its prevtxs parameter, but no equivalent exists in the PSBT workflow. Users are forced to either fall back to legacy raw transaction signing or manually edit the PSBT binary with external tools.

This closes the gap so that utxoupdatepsbt can handle the same use case natively, which is increasingly relevant with submitpackage and TRUC/anchor adoption.

Changes

Add ParsePrevTxs() helper to decode an array of raw transaction hex into a txid-indexed map
Extend ProcessPSBT() to accept caller-provided transactions and check them before falling through to txindex/mempool/UTXO set lookup
Register the new prev_txs array parameter on utxoupdatepsbt
Add functional test covering the happy path, named parameter form, and invalid hex error handling

refs #30873

Test plan

test/functional/rpc_psbt.py passes, including new test_utxoupdatepsbt_prev_txs covering:
- Input NOT populated when parent is unavailable
- Input populated correctly via prev_txs
- Correct txid in the resulting non_witness_utxo
- Error on invalid hex
- Named parameter form works

DrahtBot added the label RPC/REST/ZMQ on Apr 2, 2026

DrahtBot commented at 9:47 pm on April 2, 2026: contributor

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Concept ACK	achow101

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Conflicts

Reviewers, this pull request conflicts with the following ones:

#33014 (rpc: Fix internal bug in descriptorprocesspsbt when encountering invalid signatures by b-l-u-e)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

LLM Linter (✨ experimental)

Possible places where named args for integral literals may be used (e.g. func(x, /*named_arg=*/0) in C++, and func(x, named_arg=0) in Python):

node.descriptorprocesspsbt(child_psbt, [desc], “DEFAULT”, True, True, [parent_hex]) in test/functional/rpc_psbt.py

2026-04-07 21:18:09

bittoby commented at 11:14 am on April 6, 2026: none

@achow101 Sorry to ping you. I haven’t gotten any messages yet. Could you please review this PR? Welcome to any feedback.

instagibbs commented at 12:14 pm on April 6, 2026: member

my prior attempt hit a lack of interest in reviewing: #30886 (comment)

in src/rpc/rawtransaction.cpp:137 in 9bff773567

132+        if (!DecodeHexTx(mtx, prev_txs[i].get_str())) {
133+            throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
134+                               strprintf("TX decode failed for prev_tx %u", i));
135+        }
136+        CTransactionRef tx{MakeTransactionRef(std::move(mtx))};
137+        result.emplace(tx->GetHash(), std::move(tx));

achow101 commented at 8:09 pm on April 6, 2026:

This could check if the tx was actually inserted and error if not as that means a tx was specified multiple times.

in src/rpc/rawtransaction.cpp:2079 in 9bff773567

2074@@ -2044,7 +2075,8 @@ RPCMethod descriptorprocesspsbt()
2075         request.context,
2076         HidingSigningProvider(&provider, /*hide_secret=*/false, !bip32derivs),
2077         sighash_type,
2078-        finalize);
2079+        finalize,
2080+        /*prev_txs=*/{});

achow101 commented at 8:09 pm on April 6, 2026:

Any reason to not implement this for descriptorprocesspsbt?

achow101 commented at 8:09 pm on April 6, 2026: member

Concept ACK

bittoby commented at 8:23 pm on April 6, 2026: none

Thanks for your feedback. Updated! please review again

achow101 commented at 10:24 pm on April 6, 2026: member

Please rebase your changes in accordance with https://github.com/bitcoin/bitcoin/blob/master/CONTRIBUTING.md#rebasing-changes. PRs should not have merge commits, and each commit needs to compile and pass the tests individually.

bittoby force-pushed on Apr 6, 2026

bittoby commented at 11:17 pm on April 6, 2026: none

@achow101 I rebased my changes following the contribution guideline.

bittoby requested review from achow101 on Apr 7, 2026

bittoby commented at 8:08 pm on April 7, 2026: none

Pls let me know what else should I need to update.

rpc: add prev_txs param to utxoupdatepsbt 71fa3d1ffb

rpc: add prev_txs parameter to descriptorprocesspsbt ab8c690549

in src/rpc/rawtransaction.cpp:141 in 84a8a26d4e outdated

133@@ -134,7 +134,11 @@ static std::map<Txid, CTransactionRef> ParsePrevTxs(const UniValue& prev_txs)
134                                strprintf("TX decode failed for prev_tx %u", i));
135         }
136         CTransactionRef tx{MakeTransactionRef(std::move(mtx))};
137-        result.emplace(tx->GetHash(), std::move(tx));
138+        auto [it, inserted] = result.emplace(tx->GetHash(), std::move(tx));
139+        if (!inserted) {
140+            throw JSONRPCError(RPC_INVALID_PARAMETER,
141+                               strprintf("Duplicate prev_tx %s at index %u", it->first.ToString(), i));
142+        }

achow101 commented at 8:54 pm on April 7, 2026:

In 84a8a26d4e11ae43fc5663c614baa4f36d01dd69 “rpc: error on duplicate prev_txs entries and add prev_txs parameter to descriptorprocesspsbt”

This should be done in the previous commit when this function is introduced.

bittoby force-pushed on Apr 7, 2026

bittoby commented at 9:18 pm on April 7, 2026: none

@achow101 I have updated. Pls review again. Thanks for your feedback. 👍

bittoby requested review from achow101 on Apr 7, 2026

bittoby commented at 1:06 pm on April 10, 2026: none

Hi @achow101, could you approve this pr or pls let me know what else should I need to update?

maflcko commented at 1:20 pm on April 10, 2026: member

@bittoby Please stop spamming! Every ping is sent to 4000 notifications and continuing to ping will likely get you blocked by people or even banned by the project for violating the documented review process.

in src/rpc/rawtransaction.cpp:1769 in ab8c690549

1765@@ -1750,12 +1766,16 @@ static RPCMethod utxoupdatepsbt()
1766                          {"range", RPCArg::Type::RANGE, RPCArg::Default{1000}, "Up to what index HD chains should be explored (either end or [begin,end])"},
1767                     }},
1768                 }},
1769+                {"prev_txs", RPCArg::Type::ARR, RPCArg::Optional::OMITTED, "An array of raw transaction hex strings for previous transactions whose outputs are being spent in this PSBT but may not be available in the UTXO set, txindex, or the mempool", {

luke-jr commented at 5:53 pm on April 11, 2026:

0                {"prevtxs", RPCArg::Type::ARR, RPCArg::Optional::OMITTED, "An array of raw transaction hex strings for previous transactions whose outputs are being spent in this PSBT but may not be available in the UTXO set, txindex, or the mempool", {

luke-jr changes_requested