fix: restore the txindex requirement when governance validation is enabled

src/init.cpp

@@ -1439,6 +1439,13 @@ bool AppInitParameterInteraction(const ArgsManager& args)
         }
     }
 
+    // Governance needs the transaction index to look up proposal collateral transactions
+    if (!args.GetBoolArg("-disablegovernance", !DEFAULT_GOVERNANCE_ENABLE) &&
+        !args.GetBoolArg("-txindex", DEFAULT_TXINDEX) && chainparams.NetworkIDString() != CBaseChainParams::REGTEST) {
+        return InitError(_("Transaction index can't be disabled with governance validation enabled. Either start with "
+                           "-disablegovernance command line switch or enable transaction index."));
+    }
+
     if (args.GetBoolArg("-disablegovernance", !DEFAULT_GOVERNANCE_ENABLE)) {
         InitWarning(_("You are starting with governance validation disabled.") +
             (fPruneMode ?

test/functional/feature_governance_txindex_devnet.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+# Copyright (c) 2026 The Dash Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test that a node refuses to run governance validation without the transaction index outside regtest.
+
+Regtest exempts nodes from this check, so it is exercised on devnet here.
+"""
+
+from test_framework.governance import EXPECTED_STDERR_NO_GOV
+from test_framework.test_framework import BitcoinTestFramework
+
+
+class GovernanceTxindexDevnetTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.setup_clean_chain = True
+        self.chain = "devnet"
+        self.num_nodes = 1
+
+    def run_test(self):
+        self.stop_node(0)
+
+        self.log.info("Test that -txindex=0 is refused while governance validation is enabled")
+        self.nodes[0].assert_start_raises_init_error(
+            extra_args=["-txindex=0"],
+            expected_msg="Error: Transaction index can't be disabled with governance validation enabled. "
+                         "Either start with -disablegovernance command line switch or enable transaction index.")
+
+        self.log.info("Test that -txindex=0 is allowed together with -disablegovernance")
+        self.start_node(0, extra_args=["-txindex=0", "-disablegovernance"])
+        self.stop_node(0, expected_stderr=EXPECTED_STDERR_NO_GOV)
+
+
+if __name__ == '__main__':
+    GovernanceTxindexDevnetTest().main()

test/functional/test_runner.py

@@ -340,6 +340,7 @@
     'p2p_compactblocks_blocksonly.py',
     'p2p_mutated_blocks.py', # NOTE: needs dash_hash to pass
     'p2p_connect_to_devnet.py',
+    'feature_governance_txindex_devnet.py',
     'feature_sporks.py',
     'rpc_getblockstats.py',
     'feature_bind_port_externalip.py',