Merge bitcoin/bitcoin#28591: kernel: chainparams updates for 26.x

bd71f03df75d2c17926b6d575ffa886daa334e3a doc: update example pulls in release-process.md (fanquake)
b2ede22395ae8ce371433c9611929374dd98908a headerssync: update params for 26.x (fanquake)
f12f92b813cd8c29904f36f8ed7ed74649886897 kernel: update m_assumed_* chain params for 26.x (fanquake)
a8c2e5e556daf2a8c6b013110c802768b3f4b30e kernel: update chainTxData for 26.x (fanquake)
a9d070a6f89d855aec5fbe6efe679feef86a21f3 kernel: update nMinimumChainWork & defaultAssumeValid for 26.x (fanquake)

Pull request description:

  Update chainparams pre `26.x` branch off.

  Note: Remember that some variance is expected in the m_assumed_* sizes.

  Closes #28572.

ACKs for top commit:
  Sjors:
    re-ACK bd71f03df75d2c17926b6d575ffa886daa334e3a
  ajtowns:
    reACK bd71f03df75d2c17926b6d575ffa886daa334e3a
  darosior:
    re-ACK bd71f03df75d2c17926b6d575ffa886daa334e3a for assumevalid and minchainwork params.

Tree-SHA512: c586b82711477bfc1fd9ac4c9c1130ccde29f75d652492c66ef5730f4a49b7da822a3ad2d9090468ea0c9f0e77d00c25f6a800600c81878d8141ce2ffb3724af

4 files changed, 27 insertions, 27 deletions

diff --git a/contrib/devtools/headerssync-params.py b/contrib/devtools/headerssync-params.py
index f0088d6cb9..0198f5db99 100644
--- a/contrib/devtools/headerssync-params.py
+++ b/contrib/devtools/headerssync-params.py
@@ -12,13 +12,13 @@ import random
 # 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 468efeb7e1..c70b0194ab 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 1b5d7305e8..b885590c56 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 644e2a2c67..3ac8756e41 100644
--- a/src/kernel/chainparams.cpp
+++ b/src/kernel/chainparams.cpp
@@ -104,8 +104,8 @@ public:
         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 @@ public:
         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 @@ public:
         };
 
         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 @@ public:
         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 @@ public:
         };
 
         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 @@ public:
             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;