RPC: getblock(header) returns the same target for every block #33440

1. 
   gmart7t2 commented at 0:29 am on September 20, 2025: none

   Is there an existing issue for this?

   • I have searched the existing issues

   Current behaviour

   Run getblock or getblockheader for block 1 and you get the same “target” reported as for block 900000

   Expected behaviour

   I would expect the target to be different for different blocks

   Steps to reproduce

   Run getblock or getblockheader for block 1 and you get the same “target” reported as for block 900000

   Relevant log output

   No response

   How did you obtain Bitcoin Core

   Compiled from source

   What version of Bitcoin Core are you using?

   v29.0

   Operating system and version

   Debian Linux

   Machine specifications

   No response

2. 
   pinheadmz commented at 0:40 am on September 20, 2025: member

   Hm yeah…

   0pi@zippi:~ $ bitcoin-cli getblockheader `bitcoin-cli getblockhash 1` | jq .target
   1"00000000000000000001fa380000000000000000000000000000000000000000"
   2pi@zippi:~ $ bitcoin-cli getblockheader `bitcoin-cli getblockhash 100` | jq .target
   3"00000000000000000001fa380000000000000000000000000000000000000000"
   4pi@zippi:~ $ bitcoin-cli getblockheader `bitcoin-cli getblockhash 200000` | jq .target
   5"00000000000000000001fa380000000000000000000000000000000000000000"
   6pi@zippi:~ $ bitcoin-cli getblockheader `bitcoin-cli getblockhash 900000` | jq .target
   7"00000000000000000001fa380000000000000000000000000000000000000000"
   

3. 
   pinheadmz commented at 0:43 am on September 20, 2025: member

   I believe it’s always showing the current difficulty target for the next block
4. 
   pinheadmz commented at 0:44 am on September 20, 2025: member

   https://github.com/bitcoin/bitcoin/blob/11d80d4187afaa101de989330fa1982cd019cfa8/src/rpc/blockchain.cpp#L149-L177
5. 
   gmart7t2 commented at 1:15 am on September 20, 2025: none

   Yes. It’s the same as reported by getblockchaininfo:

   0$ bitcoin-cli getblockchaininfo | jq .target
   1"00000000000000000001fa380000000000000000000000000000000000000000"
   

6. 
   pinheadmz commented at 1:36 am on September 20, 2025: member

   This is expected, see #31583 and https://github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-29.0.md#updated-rpcs

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

7. 
   gmart7t2 commented at 4:25 am on September 20, 2025: none

   That looks like a release note error to me. Why would we want to know the current target when looking up information about an old block?

   The help text for the RPC calls says that it returns the difficulty target and difficulty of blockheader <hash>:

   

   It makes no sense to return the target for a different block’s difficulty. It means that the block header information returned for old blocks changes over time as the current difficulty changes.

8. 
   gmart7t2 commented at 4:38 am on September 20, 2025: none

   This tiny change changes both RPCs to return the target for the block of interest rather than the current target:

    0diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
    1index 8cbca51ccb..edda17d369 100644
    2--- a/src/rpc/blockchain.cpp
    3+++ b/src/rpc/blockchain.cpp
    4@@ -164,7 +164,7 @@ UniValue blockheaderToJSON(const CBlockIndex& tip, const CBlockIndex& blockindex
    5     result.pushKV("mediantime", blockindex.GetMedianTimePast());
    6     result.pushKV("nonce", blockindex.nNonce);
    7     result.pushKV("bits", strprintf("%08x", blockindex.nBits));
    8-    result.pushKV("target", GetTarget(tip, pow_limit).GetHex());
    9+    result.pushKV("target", GetTarget(blockindex, pow_limit).GetHex());
   10     result.pushKV("difficulty", GetDifficulty(blockindex));
   11     result.pushKV("chainwork", blockindex.nChainWork.GetHex());
   12     result.pushKV("nTx", blockindex.nTx);
   

9. 
   pinheadmz commented at 10:24 am on September 20, 2025: member

   Why would we want to know the current target when looking up information about an old block? @Sjors

10. 
    Sjors commented at 3:41 pm on September 20, 2025: member

    This is indeed a bug. The other commits in that PR use the tip, but that’s incorrect for these two RPC methods. See https://github.com/bitcoin/bitcoin/pull/31583/commits/2a7bfebd5e788e1d9e7e07a9f1b8e3625a0301cd#r2365643082

    I’ll PR a fix shortly, still working on adding test coverage.

11. Sjors referenced this in commit 88fb025c83 on Sep 20, 2025
12. 
    Sjors commented at 4:53 pm on September 20, 2025: member

    #33446 fixes this
13. fanquake closed this on Sep 24, 2025

    ---

14. fanquake referenced this in commit d41b503ae1 on Sep 24, 2025

Contributors
gmart7t2 pinheadmz Sjors