rpc: add bestblockhash to getmininginfo #36081

1. 
   jakubtrnka commented at 4:04 PM on August 25, 2026: none

   I'm working with pool side mining software.

   I noticed there is a race condition between obtaining bestblockhash and next block nbits. The chaintips may change.

   I thought it might be useful to include bestblockhash in getmininginfo rpc response.

2. DrahtBot added the label RPC/REST/ZMQ on Aug 25, 2026
3. 
   DrahtBot commented at 4:04 PM on August 25, 2026: contributor

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   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/36081.

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4. 
   Sjors commented at 5:19 PM on August 25, 2026: member

   Concept ACK

   We use the tip hash in a few other places to deal with race conditions, e.g. waitfornewblock takes the current tip as an argument.

   utACK 6522d443e8d0326552ac89550313578dbb3bd208 if CI passes

5. 
   jakubtrnka commented at 5:27 PM on August 25, 2026: none

   CI needs a maintainer to approve the workflow run, I believe.

6. in doc/release-notes-36081.md:1 in 6522d443e8 outdated

   ---

   ---

   

   pablomartin4btc commented at 2:57 AM on August 26, 2026:

   minor nit (if you have to retouch): the release notes filename doesn't follow the naming convention — every other file under doc/ is release-notes-<PR#>.md (so it would be release-notes-36081.md here).

   ---

   

   jakubtrnka commented at 8:17 AM on August 26, 2026:

   ok, good point. I renamed the file.

7. in src/rpc/mining.cpp:457 in 6522d443e8 outdated

    453 | @@ -454,6 +454,7 @@ static RPCMethod getmininginfo()
    454 |                      RPCResult::Type::OBJ, "", "",
    455 |                      {
    456 |                          {RPCResult::Type::NUM, "blocks", "The current block"},
    457 | +                        {RPCResult::Type::STR_HEX, "bestblockhash", "The hash of the current best block"},
   

   ---

   ---

   

   pablomartin4btc commented at 3:04 AM on August 26, 2026:

   On src/rpc/mining.cpp:457: getblockchaininfo's bestblockhash is declared RPCResult::Type::STR, while this one is STR_HEX, which I think is more correct (matches how other hash fields in this file are typed), but worth noting the two now don't match for a field with the same name and meaning.

   ---

   

   Sjors commented at 7:16 AM on August 26, 2026:

   STR_HEX indeed seems better. It might be ok to add refactor commit to switch getblockchaininfo over.

8. 
   pablomartin4btc commented at 3:05 AM on August 26, 2026: member

   Concept ACK, and utACK at 6522d443e8d0326552ac89550313578dbb3bd208 on the mechanism — nice fix.

   Left a couple of comments (none blocker).

9. rpc: add bestblockhash to getmininginfo

   Mining software building a block template from getmininginfo's `next`
   object (next height, nBits, target) also needs the hash of the tip that
   `next` was derived from. Today that requires a second call
   (getblockchaininfo or getbestblockhash), which can race with a tip
   change - notably a same-height reorg at a retarget boundary, where the
   two competing tips imply different next nBits.
   
   Return the tip hash from getmininginfo itself so all values come from
   the same tip under a single cs_main lock.

   74e1cd38f2
10. jakubtrnka force-pushed on Aug 26, 2026
11. DrahtBot added the label CI failed on Aug 26, 2026
12. 
    DrahtBot commented at 10:13 AM on August 26, 2026: contributor

    <!--85328a0da195eb286784d51f73fa0af9-->

    🚧 At least one of the CI tasks failed. _{Task Windows native, fuzz, VS: https://github.com/bitcoin/bitcoin/actions/runs/32946989507/job/98116580388} _{LLM reason (✨ experimental): CI failed because the fuzz target rpc crashed (exit code 3221225477, likely an access violation) during the fuzz corpus run.}

    <details><summary>Hints</summary>

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13. DrahtBot removed the label CI failed on Aug 26, 2026
14. 
    Sjors commented at 4:59 PM on August 26, 2026: member

    re-ACK 74e1cd38f2a381977b5e46fab6bb15ca17efd349 (just the release note file rename)

15. DrahtBot requested review from pablomartin4btc on Aug 26, 2026

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