diff --git a/src/test/consensus/ConsensusExtensions_test.cpp b/src/test/consensus/ConsensusExtensions_test.cpp
new file mode 100644
index 000000000..417031357
--- /dev/null
+++ b/src/test/consensus/ConsensusExtensions_test.cpp
@@ -0,0 +1,120 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose  with  or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED WARRANTIES OF
+    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include <test/jtx.h>
+#include <xrpld/app/consensus/ConsensusExtensions.h>
+#include <xrpld/app/ledger/Ledger.h>
+#include <xrpl/basics/StringUtilities.h>
+#include <xrpl/beast/unit_test.h>
+#include <xrpl/protocol/Feature.h>
+#include <xrpl/protocol/Indexes.h>
+
+namespace ripple {
+namespace test {
+
+class ConsensusExtensions_test : public beast::unit_test::suite
+{
+    std::vector<PublicKey>
+    makeValidatorKeys() const
+    {
+        std::vector<std::string> const rawKeys = {
+            "0388935426E0D08083314842EDFBB2D517BD47699F9A4527318A8E10468C97C05"
+            "2",
+            "02691AC5AE1C4C333AE5DF8A93BDC495F0EEBFC6DB0DA7EB6EF808F3AFC006E3F"
+            "E"};
+
+        std::vector<PublicKey> keys;
+        keys.reserve(rawKeys.size());
+        for (auto const& rawKey : rawKeys)
+        {
+            auto const pkHex = strUnHex(rawKey);
+            keys.emplace_back(makeSlice(*pkHex));
+        }
+        return keys;
+    }
+
+    void
+    testActiveValidatorViewAppliesNegativeUNL()
+    {
+        testcase("Active validator view applies NegativeUNL");
+
+        using namespace jtx;
+        Env env{
+            *this,
+            envconfig(),
+            supported_amendments() | featureNegativeUNL,
+            nullptr};
+
+        auto const vlKeys = makeValidatorKeys();
+        auto const genesis = std::make_shared<Ledger>(
+            create_genesis,
+            env.app().config(),
+            std::vector<uint256>{},
+            env.app().getNodeFamily());
+        auto l = std::make_shared<Ledger>(
+            *genesis, env.app().timeKeeper().closeTime());
+        BEAST_EXPECT(l->rules().enabled(featureNegativeUNL));
+
+        auto report = std::make_shared<SLE>(keylet::UNLReport());
+        std::vector<STObject> activeValidators;
+        for (auto const& pk : vlKeys)
+        {
+            activeValidators.push_back(
+                STObject::makeInnerObject(sfActiveValidator));
+            activeValidators.back().setFieldVL(sfPublicKey, pk);
+        }
+        report->setFieldArray(
+            sfActiveValidators, STArray(activeValidators, sfActiveValidators));
+
+        auto negUnl = std::make_shared<SLE>(keylet::negativeUNL());
+        std::vector<STObject> disabledValidators;
+        disabledValidators.push_back(
+            STObject::makeInnerObject(sfDisabledValidator));
+        disabledValidators.back().setFieldVL(sfPublicKey, vlKeys[0]);
+        disabledValidators.back().setFieldU32(sfFirstLedgerSequence, l->seq());
+        negUnl->setFieldArray(
+            sfDisabledValidators,
+            STArray(disabledValidators, sfDisabledValidators));
+        OpenView accum(&*l);
+        accum.rawInsert(report);
+        accum.rawInsert(negUnl);
+        accum.apply(*l);
+
+        ConsensusExtensions ce{env.app(), env.journal};
+        auto const view = ce.makeActiveValidatorView(l);
+
+        BEAST_EXPECT(view->fromUNLReport);
+        BEAST_EXPECT(view->size() == 1);
+        BEAST_EXPECT(!view->containsMaster(vlKeys[0]));
+        BEAST_EXPECT(!view->containsNode(calcNodeID(vlKeys[0])));
+        BEAST_EXPECT(view->containsMaster(vlKeys[1]));
+        BEAST_EXPECT(view->containsNode(calcNodeID(vlKeys[1])));
+    }
+
+public:
+    void
+    run() override
+    {
+        testActiveValidatorViewAppliesNegativeUNL();
+    }
+};
+
+BEAST_DEFINE_TESTSUITE(ConsensusExtensions, consensus, ripple);
+
+}  // namespace test
+}  // namespace ripple
diff --git a/src/xrpld/app/consensus/ConsensusExtensions.cpp b/src/xrpld/app/consensus/ConsensusExtensions.cpp
index a61d05279..fcd24791a 100644
--- a/src/xrpld/app/consensus/ConsensusExtensions.cpp
+++ b/src/xrpld/app/consensus/ConsensusExtensions.cpp
@@ -92,22 +92,29 @@ buildActiveValidatorView(
         }
     }
 
-    // TODO: If this fork still supports Negative UNL, fold that policy into
-    // this active view before quorum sizing or sidecar eligibility decisions.
-    if (!view.masterKeys.empty())
-        return view;
+    if (view.masterKeys.empty())
+    {
+        // Fallback exists for early ledgers and dev/test networks before the
+        // report object is available. It is deliberately the configured trusted
+        // master-key set so manifest signing keys still resolve through trust.
+        for (auto const& masterKey : app.validators().getTrustedMasterKeys())
+            view.insertMaster(masterKey);
 
-    // Fallback exists for early ledgers and dev/test networks before the
-    // report object is available. It is deliberately the configured trusted
-    // master-key set so manifest signing keys still resolve through trust.
-    for (auto const& masterKey : app.validators().getTrustedMasterKeys())
-        view.insertMaster(masterKey);
+        // Some standalone/dev configurations trust local validation implicitly.
+        // insertMaster() makes this idempotent if self is already trusted.
+        auto const& valKeys = app.getValidatorKeys();
+        if (valKeys.keys && valKeys.nodeID != beast::zero)
+            view.insertMaster(valKeys.keys->masterPublicKey);
+    }
 
-    // Some standalone/dev configurations trust local validation implicitly.
-    // insertMaster() makes this idempotent if self is already trusted.
-    auto const& valKeys = app.getValidatorKeys();
-    if (valKeys.keys && valKeys.nodeID != beast::zero)
-        view.insertMaster(valKeys.keys->masterPublicKey);
+    if (sourceLedger && sourceLedger->rules().enabled(featureNegativeUNL))
+    {
+        // UNLReport records recently active validators; NegativeUNL is the
+        // separate ledger policy overlay that core consensus applies to quorum.
+        // Apply it to either source so sidecar quorum matches that policy.
+        for (auto const& masterKey : sourceLedger->negativeUNL())
+            view.eraseMaster(masterKey);
+    }
 
     return view;
 }
diff --git a/src/xrpld/app/consensus/ConsensusExtensions.h b/src/xrpld/app/consensus/ConsensusExtensions.h
index 93cbcbb54..43a25b72d 100644
--- a/src/xrpld/app/consensus/ConsensusExtensions.h
+++ b/src/xrpld/app/consensus/ConsensusExtensions.h
@@ -58,6 +58,13 @@ public:
             nodeIds.insert(calcNodeID(masterKey));
         }
 
+        void
+        eraseMaster(PublicKey const& masterKey)
+        {
+            masterKeys.erase(masterKey);
+            nodeIds.erase(calcNodeID(masterKey));
+        }
+
         std::size_t
         size() const
         {