Repository: bitcoin/bitcoin (language: cpp)

Issue:
 Update chainparams pre 26.x branch-off 
### Motivation

This should be done before the branch-off, and can be done by anyone, as the steps are  reproducible and reviewable.

### Possible solution

Follow the documentation: https://github.com/bitcoin/bitcoin/blob/master/doc/release-process.md#before-branch-off

### Useful Skills

* Compiling Bitcoin Core from source
* Running the C++ unit tests and the Python functional tests
* ...


### Guidance for new contributors

Want to work on this issue?

For guidance on contributing, please read [CONTRIBUTING.md](https://github.com/bitcoin/bitcoin/blob/master/CONTRIBUTING.md) before opening your pull request.



Discussion / hints:

Fix patch:
diff --git a/contrib/devtools/headerssync-params.py b/contrib/devtools/headerssync-params.py
index f0088d6cb9a36..0198f5db99f8b 100644
--- a/contrib/devtools/headerssync-params.py
+++ b/contrib/devtools/headerssync-params.py
@@ -12,13 +12,13 @@
 # Parameters:
 
 # Aim for still working fine at some point in the future. [datetime]
-TIME = datetime(2026, 5, 25)
+TIME = datetime(2026, 10, 5)
 
 # Expected block interval. [timedelta]
 BLOCK_INTERVAL = timedelta(seconds=600)
 
 # The number of headers corresponding to the minchainwork parameter. [headers]
-MINCHAINWORK_HEADERS = 784000
+MINCHAINWORK_HEADERS = 804000
 
 # Combined processing bandwidth from all attackers to one victim. [bit/s]
 # 6 Gbit/s is approximately the speed at which a single thread of a Ryzen 5950X CPU thread can hash
diff --git a/doc/release-process.md b/doc/release-process.md
index 468efeb7e135a..c70b0194abdf9 100644
--- a/doc/release-process.md
+++ b/doc/release-process.md
@@ -28,7 +28,7 @@ Release Process
 
 #### Before branch-off
 
-* Update hardcoded [seeds](/contrib/seeds/README.md), see [this pull request](https://github.com/bitcoin/bitcoin/pull/7415) for an example.
+* Update hardcoded [seeds](/contrib/seeds/README.md), see [this pull request](https://github.com/bitcoin/bitcoin/pull/27488) for an example.
 * Update the following variables in [`src/kernel/chainparams.cpp`](/src/kernel/chainparams.cpp) for mainnet, testnet, and signet:
   - `m_assumed_blockchain_size` and `m_assumed_chain_state_size` with the current size plus some overhead (see
     [this](#how-to-calculate-assumed-blockchain-and-chain-state-size) for information on how to calculate them).
@@ -36,7 +36,7 @@ Release Process
     that causes rejection of blocks in the past history.
   - `chainTxData` with statistics about the transaction count and rate. Use the output of the `getchaintxstats` RPC with an
     `nBlocks` of 4096 (28 days) and a `bestblockhash` of RPC `getbestblockhash`; see
-    [this pull request](https://github.com/bitcoin/bitcoin/pull/20263) for an example. Reviewers can verify the results by running
+    [this pull request](https://github.com/bitcoin/bitcoin/pull/28591) for an example. Reviewers can verify the results by running
     `getchaintxstats <window_block_count> <window_final_block_hash>` with the `window_block_count` and `window_final_block_hash` from your output.
   - `defaultAssumeValid` with the output of RPC `getblockhash` using the `height` of `window_final_block_height` above
     (and update the block height comment with that height), taking into account the following:
@@ -45,7 +45,7 @@ Release Process
   - `nMinimumChainWork` with the "chainwork" value of RPC `getblockheader` using the same height as that selected for the previous step.
 * Consider updating the headers synchronization tuning parameters to account for the chainparams updates.
   The optimal values change very slowly, so this isn't strictly necessary every release, but doing so doesn't hurt.
-  - Update configuration variables in [`contrib/devtools/headerssync-params.py`](contrib/devtools/headerssync-params.py):
+  - Update configuration variables in [`contrib/devtools/headerssync-params.py`](/contrib/devtools/headerssync-params.py):
     - Set `TIME` to the software's expected supported lifetime -- after this time, its ability to defend against a high bandwidth timewarp attacker will begin to degrade.
     - Set `MINCHAINWORK_HEADERS` to the height used for the `nMinimumChainWork` calculation above.
     - Check that the other variables still look reasonable.
diff --git a/src/headerssync.cpp b/src/headerssync.cpp
index 1b5d7305e84fa..b885590c56561 100644
--- a/src/headerssync.cpp
+++ b/src/headerssync.cpp
@@ -13,11 +13,11 @@
 // contrib/devtools/headerssync-params.py.
 
 //! Store one header commitment per HEADER_COMMITMENT_PERIOD blocks.
-constexpr size_t HEADER_COMMITMENT_PERIOD{600};
+constexpr size_t HEADER_COMMITMENT_PERIOD{606};
 
 //! Only feed headers to validation once this many headers on top have been
 //! received and validated against commitments.
-constexpr size_t REDOWNLOAD_BUFFER_SIZE{14308}; // 14308/600 = ~23.8 commitments
+constexpr size_t REDOWNLOAD_BUFFER_SIZE{14441}; // 14441/606 = ~23.8 commitments
 
 // Our memory analysis assumes 48 bytes for a CompressedHeader (so we should
 // re-calculate parameters if we compress further)
diff --git a/src/kernel/chainparams.cpp b/src/kernel/chainparams.cpp
index 5e893a3f58c4d..8563d0e8eba6c 100644
--- a/src/kernel/chainparams.cpp
+++ b/src/kernel/chainparams.cpp
@@ -104,8 +104,8 @@ class CMainParams : public CChainParams {
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nTimeout = 1628640000; // August 11th, 2021
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].min_activation_height = 709632; // Approximately November 12th, 2021
 
-        consensus.nMinimumChainWork = uint256S("0x000000000000000000000000000000000000000044a50fe819c39ad624021859");
-        consensus.defaultAssumeValid = uint256S("0x000000000000000000035c3f0d31e71a5ee24c5aaf3354689f65bd7b07dee632"); // 784000
+        consensus.nMinimumChainWork = uint256S("0x000000000000000000000000000000000000000052b2559353df4117b7348b64");
+        consensus.defaultAssumeValid = uint256S("0x00000000000000000001a0a448d6cf2546b06801389cc030b2b18c6491266815"); // 804000
 
         /**
          * The message start string is designed to be unlikely to occur in normal data.
@@ -118,8 +118,8 @@ class CMainParams : public CChainParams {
         pchMessageStart[3] = 0xd9;
         nDefaultPort = 8333;
         nPruneAfterHeight = 100000;
-        m_assumed_blockchain_size = 540;
-        m_assumed_chain_state_size = 7;
+        m_assumed_blockchain_size = 590;
+        m_assumed_chain_state_size = 9;
 
         genesis = CreateGenesisBlock(1231006505, 2083236893, 0x1d00ffff, 1, 50 * COIN);
         consensus.hashGenesisBlock = genesis.GetHash();
@@ -177,10 +177,10 @@ class CMainParams : public CChainParams {
         };
 
         chainTxData = ChainTxData{
-            // Data from RPC: getchaintxstats 4096 000000000000000000035c3f0d31e71a5ee24c5aaf3354689f65bd7b07dee632
-            .nTime    = 1680665245,
-            .nTxCount = 820876044,
-            .dTxRate  = 3.672283614033389,
+            // Data from RPC: getchaintxstats 4096 00000000000000000001a0a448d6cf2546b06801389cc030b2b18c6491266815
+            .nTime    = 1692502494,
+            .nTxCount = 881818374,
+            .dTxRate  = 5.521964628130412,
         };
     }
 };
@@ -222,8 +222,8 @@ class CTestNetParams : public CChainParams {
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nTimeout = 1628640000; // August 11th, 2021
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].min_activation_height = 0; // No activation delay
 
-        consensus.nMinimumChainWork = uint256S("0x000000000000000000000000000000000000000000000977edb0244170858d07");
-        consensus.defaultAssumeValid = uint256S("0x0000000000000021bc50a89cde4870d4a81ffe0153b3c8de77b435a2fd3f6761"); // 2429000
+        consensus.nMinimumChainWork = uint256S("0x000000000000000000000000000000000000000000000b6a51f415a67c0da307");
+        consensus.defaultAssumeValid = uint256S("0x0000000000000093bcb68c03a9a168ae252572d348a2eaeba2cdf9231d73206f"); // 2500000
 
         pchMessageStart[0] = 0x0b;
         pchMessageStart[1] = 0x11;
@@ -276,10 +276,10 @@ class CTestNetParams : public CChainParams {
         };
 
         chainTxData = ChainTxData{
-            // Data from RPC: getchaintxstats 4096 0000000000000021bc50a89cde4870d4a81ffe0153b3c8de77b435a2fd3f6761
-            .nTime    = 1681542696,
-            .nTxCount = 65345929,
-            .dTxRate  = 0.09855282814711661,
+            // Data from RPC: getchaintxstats 4096 0000000000000093bcb68c03a9a168ae252572d348a2eaeba2cdf9231d73206f
+            .nTime    = 1694733634,
+            .nTxCount = 66484552,
+            .dTxRate  = 0.1804908356632494,
         };
     }
 };
@@ -302,15 +302,15 @@ class SigNetParams : public CChainParams {
             vSeeds.emplace_back("178.128.221.177");
             vSeeds.emplace_back("v7ajjeirttkbnt32wpy3c6w3emwnfr3fkla7hpxcfokr3ysd3kqtzmqd.onion:38333");
 
-            consensus.nMinimumChainWork = uint256S("0x000000000000000000000000000000000000000000000000000001899d8142b0");
-            consensus.defaultAssumeValid = uint256S("0x0000004429ef154f7e00b4f6b46bfbe2d2678ecd351d95bbfca437ab9a5b84ec"); // 138000
+            consensus.nMinimumChainWork = uint256S("0x000000000000000000000000000000000000000000000000000001ad46be4862");
+            consensus.defaultAssumeValid = uint256S("0x0000013d778ba3f914530f11f6b69869c9fab54acff85acd7b8201d111f19b7f"); // 150000
             m_assumed_blockchain_size = 1;
             m_assumed_chain_state_size = 0;
             chainTxData = ChainTxData{
-                // Data from RPC: getchaintxstats 4096 0000004429ef154f7e00b4f6b46bfbe2d2678ecd351d95bbfca437ab9a5b84ec
-                .nTime    = 1681127428,
-                .nTxCount = 2226359,
-                .dTxRate  = 0.006424463050600656,
+                // Data from RPC: getchaintxstats 4096 0000013d778ba3f914530f11f6b69869c9fab54acff85acd7b8201d111f19b7f
+                .nTime    = 1688366339,
+                .nTxCount = 2262750,
+                .dTxRate  = 0.003414084572046456,
             };
         } else {
             bin = *options.challenge;


Test patch: