mining: add coinbase locktime and sequence fields to getblocktemplate RPC #34419

1. 
   Sjors commented at 2:17 pm on January 27, 2026: member

   BIP54 proposes contraining the cointbase transaction nLockTime and nSequence fields. Our internal mining code has been doing this since #32155, but currently the fields are only communicated to IPC clients (see e.g. #33819).

   This PR extends the getblocktemplate RPC to provide these fields.

   Accompanying proposed extension to BIP54: https://github.com/bitcoin/bips/pull/2097

   Even if BIP54 never activates, it makes sense to serve these new fields.

2. refactor: use CoinbaseTx for coinbasevalue a73c41a1dc
3. DrahtBot added the label Mining on Jan 27, 2026
4. 
   DrahtBot commented at 2:17 pm on January 27, 2026: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/34419.

   Reviews

   See the guideline for information on the review process. A summary of reviews will appear here.

5. Sjors force-pushed on Jan 27, 2026
6. DrahtBot added the label CI failed on Jan 27, 2026
7. 
   Sjors commented at 3:03 pm on January 27, 2026: member

   Added the coinbase nVersion.
8. Sjors renamed this:
   mining: add coinbase locktime and sequence fields to getblocktemplate RPC
   mining: add coinbase locktime, sequence and version fields to getblocktemplate RPC
   on Jan 27, 2026
9. DrahtBot removed the label CI failed on Jan 27, 2026
10. Sjors marked this as ready for review on Feb 9, 2026
11. mining: add coinbase locktime and sequence fields

    Expand the getblocktemplate RPC result with two fields to prepare
    for a possible BIP54 deployment in the future.

    e3d4f3f7fe
12. Sjors force-pushed on Mar 4, 2026
13. 
    Sjors commented at 1:33 pm on March 4, 2026: member

    I dropped nVersion from the proposal, see https://github.com/bitcoin/bips/pull/2097#issuecomment-3997488850.

    Although it’s harmless to add, I also dropped it from the implementation here for clarity. It can be added in a followup.

14. Sjors renamed this:
    mining: add coinbase locktime, sequence and version fields to getblocktemplate RPC
    mining: add coinbase locktime and sequence fields to getblocktemplate RPC
    on Mar 4, 2026
15. DrahtBot added the label CI failed on Mar 4, 2026
16. DrahtBot removed the label CI failed on Mar 5, 2026

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