diff --git a/src/test/consensus/ProposalPrecheck_test.cpp b/src/test/consensus/ProposalPrecheck_test.cpp
index 9fb451de5..2c5a9343b 100644
--- a/src/test/consensus/ProposalPrecheck_test.cpp
+++ b/src/test/consensus/ProposalPrecheck_test.cpp
@@ -63,6 +63,16 @@ public:
     {
         using enum detail::ProposalPrecheckResult;
 
+        //@@start test-peer-proposal-authentication
+        testcase("cluster transport does not bypass proposal authentication");
+        {
+            BEAST_EXPECT(detail::proposalSignatureAccepted(false, true));
+            BEAST_EXPECT(detail::proposalSignatureAccepted(true, true));
+            BEAST_EXPECT(!detail::proposalSignatureAccepted(false, false));
+            BEAST_EXPECT(!detail::proposalSignatureAccepted(true, false));
+        }
+        //@@end test-peer-proposal-authentication
+
         //@@start test-proposal-precheck-legacy-ok
         testcase("legacy and extended ok");
         {
diff --git a/src/xrpld/app/consensus/ProposalPrecheck.h b/src/xrpld/app/consensus/ProposalPrecheck.h
index 0e875255b..8b78a8a68 100644
--- a/src/xrpld/app/consensus/ProposalPrecheck.h
+++ b/src/xrpld/app/consensus/ProposalPrecheck.h
@@ -37,6 +37,13 @@ struct ProposalPrecheckRejection
     char const* feeReason;
 };
 
+inline bool
+proposalSignatureAccepted(bool /* clusterPeer */, bool signatureValid)
+{
+    // Cluster trust affects relay and charging, never validator attribution.
+    return signatureValid;
+}
+
 inline bool
 proposalHasMalformedHashes(protocol::TMProposeSet const& set)
 {
diff --git a/src/xrpld/overlay/detail/PeerImp.cpp b/src/xrpld/overlay/detail/PeerImp.cpp
index 07379b176..132e8e690 100644
--- a/src/xrpld/overlay/detail/PeerImp.cpp
+++ b/src/xrpld/overlay/detail/PeerImp.cpp
@@ -3120,19 +3120,19 @@ PeerImp::checkPropose(
 
     XRPL_ASSERT(packet, "ripple::PeerImp::checkPropose : non-null packet");
 
-    // Always verify the proposal signature before harvesting export
-    // sigs, even in cluster mode.  Cluster peers are trusted for relay
-    // and resource charging, but export sigs produce on-chain artifacts
-    // (multisigned blobs in metadata) so they require cryptographic
-    // proof of validator identity regardless.
+    // Always authenticate validator positions, including those relayed by a
+    // cluster peer. Sidecar alignment counts these positions as validator
+    // statements, so cluster transport trust cannot replace the signature.
+    //@@start peer-proposal-authentication
     bool const sigValid = peerPos.checkSign();
-    if (!cluster() && !sigValid)
+    if (!detail::proposalSignatureAccepted(cluster(), sigValid))
     {
         std::string desc{"Proposal fails sig check"};
         JLOG(p_journal_.warn()) << desc;
         charge(Resource::feeInvalidSignature, desc);
         return;
     }
+    //@@end peer-proposal-authentication
 
     //@@start peer-harvest-export-sigs
     // Harvest export sigs AFTER checkSign() so only cryptographically