From c08246d68c84e27020fe35d8d4dfe54f2f855657 Mon Sep 17 00:00:00 2001
From: VictorLux <mike_lux@hotmail.fr>
Date: Tue, 9 Jun 2026 22:31:45 +0200
Subject: [PATCH] Activate ZIP-209 shielded turnstile on mainnet

Enable fZIP209Enabled on mainnet (CMainParams) with a Sprout value-pool
checkpoint at height 3000000 (balance 1316412375709, block
0000038aee939c8017f4ad353e3fd1313c6a0da565bbc1d3269bbe855fe33505), mirroring
the existing testnet configuration. With this set, ConnectBlock's existing
ZIP-209 enforcement rejects any block that drives the Sprout or Sapling
shielded value-pool balance negative (turnstile containment), bounding the
damage of any shielded-circuit soundness bug: value forged inside a pool
cannot be withdrawn past the pool boundary undetected.

This is a consensus rule-tightening (soft fork) and wants a coordinated
network upgrade -- see the PR description.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 src/chainparams.cpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index fab7224ba22..6033c95d0ef 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -202,6 +202,21 @@ class CMainParams : public CChainParams {
             1138            // * recent transactions/day (measured: ~1.0 tx/block, ~1138 blocks/day)
         };
 
+        // ZIP-209: reject any block that drives a shielded value pool balance
+        // negative (turnstile enforcement). Previously configured on testnet
+        // only; this mirrors that for mainnet. The hardcoded Sprout checkpoint
+        // re-seeds nChainSproutValue for nodes whose block index predates pool
+        // monitoring, so they can enforce from this height forward WITHOUT a full
+        // reindex; nodes that tracked the pool from genesis instead assert their
+        // computed balance equals this value, so it MUST be the exact genesis-
+        // derived Sprout balance at this block. Verified on a synced mainnet node:
+        //   getblock 0000038aee939c8017f4ad353e3fd1313c6a0da565bbc1d3269bbe855fe33505
+        //   -> valuePools[id=sprout].chainValueZat == 1316412375709  (height 3000000)
+        nSproutValuePoolCheckpointHeight = 3000000;
+        nSproutValuePoolCheckpointBalance = 1316412375709;
+        fZIP209Enabled = true;
+        hashSproutValuePoolCheckpointBlock = uint256S("0000038aee939c8017f4ad353e3fd1313c6a0da565bbc1d3269bbe855fe33505");
+
         fastSyncAnchorData.nHeight = 3126937;
         fastSyncAnchorData.hashBlock = uint256S("0x00000663e40f1fe0bc32a7e7282fac25de5fe8ecefd9c627e2fd948d388f7053");
         fastSyncAnchorData.hashAnchorSha256 = uint256S("0x376d6d5e6f7d02459b89ae0988f5c51bb1deaf2a3e4b3a1de745e4f2e3bb279d");