diff --git a/src/libs/services/recommendation/impl/audio-similarity/AudioSimilarityEngine.impl.hpp b/src/libs/services/recommendation/impl/audio-similarity/AudioSimilarityEngine.impl.hpp
index c3c869c7..114335ef 100644
--- a/src/libs/services/recommendation/impl/audio-similarity/AudioSimilarityEngine.impl.hpp
+++ b/src/libs/services/recommendation/impl/audio-similarity/AudioSimilarityEngine.impl.hpp
@@ -50,10 +50,10 @@
 
 #include "InterpolationFitConstraint.hpp"
 #include "MaxDistanceConstraint.hpp"
-#include "NearDuplicateEmbeddingConstraint.hpp"
 #include "SmoothTransitionConstraint.hpp"
 #include "track-selection-constraints/DuplicateTrackConstraint.hpp"
 #include "track-selection-constraints/SameArtistConstraint.hpp"
+#include "track-selection-constraints/SameRecordingMBIDConstraint.hpp"
 #include "track-selection-constraints/SameReleaseConstraint.hpp"
 
 #include "Types.hpp"
@@ -121,11 +121,9 @@ namespace lms::recommendation
         constexpr float smoothTransitionWeight{ 0.2F };
         constexpr float sameReleaseWeight{ 0.5F };
         constexpr float sameArtistWeight{ 0.5F };
-        constexpr float nearDuplicateThreshold{ 0.01F };
-
         _similarityEvaluator = {};
         _similarityEvaluator.addHardConstraint(std::make_unique<DuplicateTrackConstraint>());
-        _similarityEvaluator.addHardConstraint(std::make_unique<NearDuplicateEmbeddingConstraint<ReducedDimCount>>(_trackVectors, nearDuplicateThreshold));
+        _similarityEvaluator.addHardConstraint(std::make_unique<SameRecordingMBIDConstraint>(_trackMetadata));
         _similarityEvaluator.addHardConstraint(std::make_unique<MaxDistanceConstraint<ReducedDimCount>>(_trackVectors, _trackDistanceThreshold));
         _similarityEvaluator.addSoftConstraint(std::make_unique<InterpolationFitConstraint<ReducedDimCount>>(_trackVectors), interpolationFitWeight);
         _similarityEvaluator.addSoftConstraint(std::make_unique<SmoothTransitionConstraint<ReducedDimCount>>(_trackVectors), smoothTransitionWeight);
@@ -134,7 +132,7 @@ namespace lms::recommendation
 
         _pathEvaluator = {};
         _pathEvaluator.addHardConstraint(std::make_unique<DuplicateTrackConstraint>());
-        _pathEvaluator.addHardConstraint(std::make_unique<NearDuplicateEmbeddingConstraint<ReducedDimCount>>(_trackVectors, nearDuplicateThreshold));
+        _pathEvaluator.addHardConstraint(std::make_unique<SameRecordingMBIDConstraint>(_trackMetadata));
         _pathEvaluator.addSoftConstraint(std::make_unique<InterpolationFitConstraint<ReducedDimCount>>(_trackVectors), interpolationFitWeight);
         _pathEvaluator.addSoftConstraint(std::make_unique<SmoothTransitionConstraint<ReducedDimCount>>(_trackVectors), smoothTransitionWeight);
         _pathEvaluator.addSoftConstraint(std::make_unique<SameReleaseConstraint>(_trackMetadata), sameReleaseWeight);
@@ -595,28 +593,29 @@ namespace lms::recommendation
             _trackVectors.try_emplace(trackId, &reducedVector);
         });
 
-        db::Release::find(session, db::Release::FindParameters{}, [&](const db::Release::pointer& release) {
-            std::vector<std::reference_wrapper<const ReducedVector>> releaseTrackFeatures;
+        db::Track::find(session, db::Track::FindParameters{}, [&](const db::Track::pointer& track) {
+            const auto itVec{ _trackVectors.find(track->getId()) };
+            if (itVec == _trackVectors.cend())
+                return;
 
-            db::Track::FindParameters params;
-            params.setRelease(release->getId());
+            auto& meta{ _trackMetadata[track->getId()] };
+            const db::ReleaseId releaseId{ track->getReleaseId() };
+            meta.releaseId = releaseId;
+            meta.recordingMBID = track->getRecordingMBID();
 
-            const auto trackIds{ db::Track::findIds(session, params) };
-            for (const db::TrackId trackId : trackIds.results)
-            {
-                const auto itFeatures{ _trackVectors.find(trackId) };
-                if (itFeatures != std::cend(_trackVectors))
-                {
-                    assert(itFeatures->second);
-                    releaseTrackFeatures.emplace_back(*itFeatures->second);
-                    _trackMetadata[trackId].releaseId = release->getId();
-                }
-            }
-
-            if (!releaseTrackFeatures.empty())
-                _releaseVectors.try_emplace(release->getId(), std::move(releaseTrackFeatures));
+            if (releaseId.isValid())
+                _releaseVectors[releaseId].emplace_back(*itVec->second);
         });
 
+        math::MedoidCalculator<ReducedVector> calc;
+        for (const auto& [id, vecs] : _releaseVectors)
+        {
+            calc.clear();
+            for (const auto& v : vecs)
+                calc.add(v.get());
+            _releaseMedoids.try_emplace(id, calc.finalize());
+        }
+
         db::Artist::find(session, db::Artist::FindParameters{}, [&](const db::Artist::pointer& artist) {
             const auto mbid{ artist->getMBID() };
             // skip "Various Artists" to avoid false artist matches
@@ -658,15 +657,6 @@ namespace lms::recommendation
                 _artistVectors.try_emplace(artist->getId(), std::move(artistTrackVectors));
         });
 
-        math::MedoidCalculator<ReducedVector> calc;
-        for (const auto& [id, vecs] : _releaseVectors)
-        {
-            calc.clear();
-            for (const auto& v : vecs)
-                calc.add(v.get());
-            _releaseMedoids.try_emplace(id, calc.finalize());
-        }
-
         for (const auto& [id, vecs] : _artistVectors)
         {
             calc.clear();
diff --git a/src/libs/services/recommendation/impl/clusters/ClustersEngine.cpp b/src/libs/services/recommendation/impl/clusters/ClustersEngine.cpp
index 5e4476a8..8c01c15c 100644
--- a/src/libs/services/recommendation/impl/clusters/ClustersEngine.cpp
+++ b/src/libs/services/recommendation/impl/clusters/ClustersEngine.cpp
@@ -23,7 +23,6 @@
 #include <limits>
 #include <memory>
 #include <optional>
-#include <random>
 #include <unordered_set>
 
 #include "database/IDb.hpp"
@@ -39,6 +38,7 @@
 
 #include "track-selection-constraints/DuplicateTrackConstraint.hpp"
 #include "track-selection-constraints/SameArtistConstraint.hpp"
+#include "track-selection-constraints/SameRecordingMBIDConstraint.hpp"
 #include "track-selection-constraints/SameReleaseConstraint.hpp"
 #include "track-selection-constraints/TrackCandidateContext.hpp"
 
@@ -103,6 +103,7 @@ namespace lms::recommendation
         constexpr float sameReleaseWeight{ 0.5F };
         constexpr float sameArtistWeight{ 0.5F };
         _trackEvaluator.addHardConstraint(std::make_unique<DuplicateTrackConstraint>());
+        _trackEvaluator.addHardConstraint(std::make_unique<SameRecordingMBIDConstraint>(_trackMetadata));
         _trackEvaluator.addSoftConstraint(std::make_unique<SameReleaseConstraint>(_trackMetadata), sameReleaseWeight);
         _trackEvaluator.addSoftConstraint(std::make_unique<SameArtistConstraint>(_trackMetadata), sameArtistWeight);
     }
@@ -122,8 +123,8 @@ namespace lms::recommendation
         db::Session& session{ _db.getTLSSession() };
         auto transaction{ session.createReadTransaction() };
 
-        buildTrackMetadata(session);
         buildTrackClusters(session);
+        buildTrackMetadata(session);
         buildReleaseClusters();
         buildArtistClusters();
 
@@ -134,11 +135,17 @@ namespace lms::recommendation
     {
         LOG(DEBUG, "building track metadata...");
 
-        db::Release::find(session, db::Release::FindParameters{}, [&](const db::Release::pointer& release) {
-            db::Track::FindParameters params;
-            params.setRelease(release->getId());
-            for (const db::TrackId trackId : db::Track::findIds(session, params).results)
-                _trackMetadata[trackId].releaseId = release->getId();
+        // Ensure cluster tracks with no release/artist have an entry
+        for (const auto& [trackId, _] : _trackClusters)
+            _trackMetadata.try_emplace(trackId);
+
+        db::Track::find(session, db::Track::FindParameters{}, [&](const db::Track::pointer& track) {
+            const auto it{ _trackMetadata.find(track->getId()) };
+            if (it != _trackMetadata.cend())
+            {
+                it->second.releaseId = track->getReleaseId();
+                it->second.recordingMBID = track->getRecordingMBID();
+            }
         });
 
         db::Artist::find(session, db::Artist::FindParameters{}, [&](const db::Artist::pointer& artist) {
diff --git a/src/libs/services/recommendation/impl/clusters/ClustersEngine.hpp b/src/libs/services/recommendation/impl/clusters/ClustersEngine.hpp
index f123c15e..bd46f9ac 100644
--- a/src/libs/services/recommendation/impl/clusters/ClustersEngine.hpp
+++ b/src/libs/services/recommendation/impl/clusters/ClustersEngine.hpp
@@ -54,8 +54,8 @@ namespace lms::recommendation
         ArtistResults findSimilarArtists(db::ArtistId artistId, core::EnumSet<db::TrackArtistLinkType> linkTypes, std::size_t maxCount) const override;
 
         TrackResults greedySelect(std::vector<db::TrackId> candidates, std::vector<db::TrackId> selectedTracks, std::size_t maxCount) const;
-        void buildTrackMetadata(db::Session& session);
         void buildTrackClusters(db::Session& session);
+        void buildTrackMetadata(db::Session& session);
         void buildReleaseClusters();
         void buildArtistClusters();
 
diff --git a/src/libs/services/recommendation/impl/track-selection-constraints/SameRecordingMBIDConstraint.hpp b/src/libs/services/recommendation/impl/track-selection-constraints/SameRecordingMBIDConstraint.hpp
new file mode 100644
index 00000000..9a76edd7
--- /dev/null
+++ b/src/libs/services/recommendation/impl/track-selection-constraints/SameRecordingMBIDConstraint.hpp
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2026 Emeric Poupon
+ *
+ * This file is part of LMS.
+ *
+ * LMS is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * LMS is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with LMS.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "ITrackCandidateHardConstraint.hpp"
+#include "TrackMetadata.hpp"
+
+namespace lms::recommendation
+{
+    class SameRecordingMBIDConstraint : public ITrackCandidateHardConstraint
+    {
+    public:
+        SameRecordingMBIDConstraint(const TrackMetadataMap& trackMetadata)
+            : _trackMetadata{ trackMetadata }
+        {
+        }
+
+        bool rejects(const TrackCandidateContext& context) const override
+        {
+            const auto it{ _trackMetadata.find(context.candidateTrackId) };
+            if (it == _trackMetadata.cend() || !it->second.recordingMBID)
+                return false;
+
+            for (const db::TrackId selectedId : context.selectedTracks)
+            {
+                const auto itSel{ _trackMetadata.find(selectedId) };
+                if (itSel != _trackMetadata.cend() && itSel->second.recordingMBID == it->second.recordingMBID)
+                    return true;
+            }
+            return false;
+        }
+
+    private:
+        const TrackMetadataMap& _trackMetadata;
+    };
+} // namespace lms::recommendation
diff --git a/src/libs/services/recommendation/impl/track-selection-constraints/TrackMetadata.hpp b/src/libs/services/recommendation/impl/track-selection-constraints/TrackMetadata.hpp
index d2a89b43..88393b7a 100644
--- a/src/libs/services/recommendation/impl/track-selection-constraints/TrackMetadata.hpp
+++ b/src/libs/services/recommendation/impl/track-selection-constraints/TrackMetadata.hpp
@@ -19,9 +19,11 @@
 
 #pragma once
 
+#include <optional>
 #include <unordered_map>
 #include <vector>
 
+#include "core/UUID.hpp"
 #include "database/objects/ArtistId.hpp"
 #include "database/objects/ReleaseId.hpp"
 #include "database/objects/TrackId.hpp"
@@ -30,9 +32,9 @@ namespace lms::recommendation
 {
     struct TrackMetadata
     {
-        db::ReleaseId releaseId;             // invalid if track has no release
-        std::vector<db::ArtistId> artistIds; // sorted; album artists only
-        // Future: db::MediaLibraryId mediaLibraryId;
+        db::ReleaseId releaseId;                 // invalid if track has no release
+        std::vector<db::ArtistId> artistIds;     // sorted, album artists only
+        std::optional<core::UUID> recordingMBID; // absent if track has no recording MBID
     };
 
     using TrackMetadataMap = std::unordered_map<db::TrackId, TrackMetadata>;
diff --git a/src/libs/services/recommendation/test/ConstraintsTest.cpp b/src/libs/services/recommendation/test/ConstraintsTest.cpp
index 4d9cc9b9..f9fc7b38 100644
--- a/src/libs/services/recommendation/test/ConstraintsTest.cpp
+++ b/src/libs/services/recommendation/test/ConstraintsTest.cpp
@@ -24,390 +24,474 @@
 #include "database/objects/TrackId.hpp"
 #include "math/Vector.hpp"
 
+#include "core/UUID.hpp"
+
 #include "audio-similarity/InterpolationFitConstraint.hpp"
 #include "audio-similarity/MaxDistanceConstraint.hpp"
 #include "audio-similarity/NearDuplicateEmbeddingConstraint.hpp"
 #include "audio-similarity/SmoothTransitionConstraint.hpp"
 #include "track-selection-constraints/DuplicateTrackConstraint.hpp"
 #include "track-selection-constraints/SameArtistConstraint.hpp"
+#include "track-selection-constraints/SameRecordingMBIDConstraint.hpp"
 #include "track-selection-constraints/SameReleaseConstraint.hpp"
 #include "track-selection-constraints/TrackCandidateContext.hpp"
 #include "track-selection-constraints/TrackCandidateEvaluator.hpp"
 #include "track-selection-constraints/TrackMetadata.hpp"
 
-using namespace lms;
-using namespace lms::recommendation;
-
-namespace
+namespace lms::recommendation::tests
 {
-    const db::TrackId T1{ 1 };
-    const db::TrackId T2{ 2 };
-    const db::TrackId T3{ 3 };
-    const db::TrackId T4{ 4 };
+    namespace
+    {
+        const db::TrackId T1{ 1 };
+        const db::TrackId T2{ 2 };
+        const db::TrackId T3{ 3 };
+        const db::TrackId T4{ 4 };
 
-    const db::ArtistId A1{ 10 };
-    const db::ArtistId A2{ 20 };
+        const db::ArtistId A1{ 10 };
+        const db::ArtistId A2{ 20 };
 
-    const db::ReleaseId R1{ 100 };
-    const db::ReleaseId R2{ 200 };
-} // namespace
+        const db::ReleaseId R1{ 100 };
+        const db::ReleaseId R2{ 200 };
+    } // namespace
 
-TEST(DuplicateTrackConstraint, acceptsNewCandidate)
-{
-    const std::vector<db::TrackId> selected{ T1, T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T3, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FALSE(DuplicateTrackConstraint{}.rejects(ctx));
-}
+    TEST(DuplicateTrackConstraint, acceptsNewCandidate)
+    {
+        const std::vector<db::TrackId> selected{ T1, T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T3, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(DuplicateTrackConstraint{}.rejects(ctx));
+    }
 
-TEST(DuplicateTrackConstraint, rejectsAlreadySelected)
-{
-    const std::vector<db::TrackId> selected{ T1, T2, T3 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T2, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_TRUE(DuplicateTrackConstraint{}.rejects(ctx));
-}
+    TEST(DuplicateTrackConstraint, rejectsAlreadySelected)
+    {
+        const std::vector<db::TrackId> selected{ T1, T2, T3 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T2, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_TRUE(DuplicateTrackConstraint{}.rejects(ctx));
+    }
 
-TEST(DuplicateTrackConstraint, acceptsWhenSelectionEmpty)
-{
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
-    EXPECT_FALSE(DuplicateTrackConstraint{}.rejects(ctx));
-}
+    TEST(DuplicateTrackConstraint, acceptsWhenSelectionEmpty)
+    {
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
+        EXPECT_FALSE(DuplicateTrackConstraint{}.rejects(ctx));
+    }
 
-TEST(SameArtistConstraint, zeroScoreWhenNoSharedArtist)
-{
-    const TrackMetadataMap meta{
-        { T1, { .releaseId = {}, .artistIds = { A1 } } },
-        { T2, { .releaseId = {}, .artistIds = { A2 } } },
-    };
-    const SameArtistConstraint constraint{ meta };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+    TEST(SameArtistConstraint, zeroScoreWhenNoSharedArtist)
+    {
+        const TrackMetadataMap meta{
+            { T1, { .releaseId = {}, .artistIds = { A1 } } },
+            { T2, { .releaseId = {}, .artistIds = { A2 } } },
+        };
+        const SameArtistConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
 
-TEST(SameArtistConstraint, fullScoreWhenMostRecentMatchesArtist)
-{
-    TrackMetadataMap meta{
-        { T1, { .releaseId = {}, .artistIds = { A1 } } },
-        { T2, { .releaseId = {}, .artistIds = { A1 } } },
-    };
-    const SameArtistConstraint constraint{ meta };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+    TEST(SameArtistConstraint, fullScoreWhenMostRecentMatchesArtist)
+    {
+        TrackMetadataMap meta{
+            { T1, { .releaseId = {}, .artistIds = { A1 } } },
+            { T2, { .releaseId = {}, .artistIds = { A1 } } },
+        };
+        const SameArtistConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
 
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 1.F);
-}
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 1.F);
+    }
 
-TEST(SameArtistConstraint, halfScoreWhenSecondMostRecentMatchesArtist)
-{
-    TrackMetadataMap meta{
-        { T1, { .releaseId = {}, .artistIds = { A1 } } },
-        { T2, { .releaseId = {}, .artistIds = { A2 } } },
-        { T3, { .releaseId = {}, .artistIds = { A1 } } },
-    };
-    const SameArtistConstraint constraint{ meta };
+    TEST(SameArtistConstraint, halfScoreWhenSecondMostRecentMatchesArtist)
+    {
+        TrackMetadataMap meta{
+            { T1, { .releaseId = {}, .artistIds = { A1 } } },
+            { T2, { .releaseId = {}, .artistIds = { A2 } } },
+            { T3, { .releaseId = {}, .artistIds = { A1 } } },
+        };
+        const SameArtistConstraint constraint{ meta };
 
-    const std::vector<db::TrackId> selected{ T3, T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        const std::vector<db::TrackId> selected{ T3, T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
 
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.5F);
-}
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.5F);
+    }
 
-TEST(SameArtistConstraint, trackOutsideWindowIsIgnored)
-{
-    TrackMetadataMap meta{
-        { T1, { .releaseId = {}, .artistIds = { A1 } } },
-        { T2, { .releaseId = {}, .artistIds = { A2 } } },
-        { T3, { .releaseId = {}, .artistIds = { A1 } } },
-    };
-    const SameArtistConstraint constraint{ meta, /*window=*/1 };
+    TEST(SameArtistConstraint, trackOutsideWindowIsIgnored)
+    {
+        TrackMetadataMap meta{
+            { T1, { .releaseId = {}, .artistIds = { A1 } } },
+            { T2, { .releaseId = {}, .artistIds = { A2 } } },
+            { T3, { .releaseId = {}, .artistIds = { A1 } } },
+        };
+        const SameArtistConstraint constraint{ meta, /*window=*/1 };
 
-    const std::vector<db::TrackId> selected{ T3, T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+        const std::vector<db::TrackId> selected{ T3, T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
 
-TEST(SameArtistConstraint, zeroScoreWhenCandidateNotInMap)
-{
-    const TrackMetadataMap meta{};
-    const SameArtistConstraint constraint{ meta };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+    TEST(SameArtistConstraint, zeroScoreWhenCandidateNotInMap)
+    {
+        const TrackMetadataMap meta{};
+        const SameArtistConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
 
-TEST(SameReleaseConstraint, zeroScoreWhenNoSharedRelease)
-{
-    TrackMetadataMap meta{
-        { T1, { .releaseId = R1, .artistIds = {} } },
-        { T2, { .releaseId = R2, .artistIds = {} } },
-    };
-    const SameReleaseConstraint constraint{ meta };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+    TEST(SameReleaseConstraint, zeroScoreWhenNoSharedRelease)
+    {
+        TrackMetadataMap meta{
+            { T1, { .releaseId = R1, .artistIds = {} } },
+            { T2, { .releaseId = R2, .artistIds = {} } },
+        };
+        const SameReleaseConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
 
-TEST(SameReleaseConstraint, fullScoreWhenMostRecentMatchesRelease)
-{
-    TrackMetadataMap meta{
-        { T1, { .releaseId = R1, .artistIds = {} } },
-        { T2, { .releaseId = R1, .artistIds = {} } },
-    };
-    const SameReleaseConstraint constraint{ meta };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 1.F);
-}
+    TEST(SameReleaseConstraint, fullScoreWhenMostRecentMatchesRelease)
+    {
+        TrackMetadataMap meta{
+            { T1, { .releaseId = R1, .artistIds = {} } },
+            { T2, { .releaseId = R1, .artistIds = {} } },
+        };
+        const SameReleaseConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 1.F);
+    }
 
-TEST(SameReleaseConstraint, zeroScoreWhenCandidateHasNoRelease)
-{
-    TrackMetadataMap meta{
-        { T1, { .releaseId = {}, .artistIds = {} } },
-        { T2, { .releaseId = R1, .artistIds = {} } },
-    };
-    const SameReleaseConstraint constraint{ meta };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+    TEST(SameReleaseConstraint, zeroScoreWhenCandidateHasNoRelease)
+    {
+        TrackMetadataMap meta{
+            { T1, { .releaseId = {}, .artistIds = {} } },
+            { T2, { .releaseId = R1, .artistIds = {} } },
+        };
+        const SameReleaseConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
 
-TEST(TrackCandidateEvaluator, hardConstraintRejects)
-{
-    TrackCandidateEvaluator evaluator;
-    evaluator.addHardConstraint(std::make_unique<DuplicateTrackConstraint>());
+    TEST(TrackCandidateEvaluator, hardConstraintRejects)
+    {
+        TrackCandidateEvaluator evaluator;
+        evaluator.addHardConstraint(std::make_unique<DuplicateTrackConstraint>());
 
-    const std::vector<db::TrackId> selected{ T1 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_TRUE(evaluator.rejects(ctx));
-}
+        const std::vector<db::TrackId> selected{ T1 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_TRUE(evaluator.rejects(ctx));
+    }
 
-TEST(TrackCandidateEvaluator, noHardConstraintDoesNotReject)
-{
-    TrackCandidateEvaluator evaluator;
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
-    EXPECT_FALSE(evaluator.rejects(ctx));
-}
+    TEST(TrackCandidateEvaluator, noHardConstraintDoesNotReject)
+    {
+        TrackCandidateEvaluator evaluator;
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
+        EXPECT_FALSE(evaluator.rejects(ctx));
+    }
 
-TEST(TrackCandidateEvaluator, softConstraintScoreIsWeighted)
-{
-    TrackMetadataMap meta{
-        { T1, { .releaseId = R1, .artistIds = {} } },
-        { T2, { .releaseId = R1, .artistIds = {} } },
-    };
-    TrackCandidateEvaluator evaluator;
-    evaluator.addSoftConstraint(std::make_unique<SameReleaseConstraint>(meta), 2.F);
+    TEST(TrackCandidateEvaluator, softConstraintScoreIsWeighted)
+    {
+        TrackMetadataMap meta{
+            { T1, { .releaseId = R1, .artistIds = {} } },
+            { T2, { .releaseId = R1, .artistIds = {} } },
+        };
+        TrackCandidateEvaluator evaluator;
+        evaluator.addSoftConstraint(std::make_unique<SameReleaseConstraint>(meta), 2.F);
 
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
 
-    EXPECT_FLOAT_EQ(evaluator.score(ctx), 2.F);
-}
+        EXPECT_FLOAT_EQ(evaluator.score(ctx), 2.F);
+    }
 
-TEST(TrackCandidateEvaluator, multipleSoftConstraintsAreAccumulated)
-{
-    TrackMetadataMap meta{
-        { T1, { .releaseId = R1, .artistIds = { A1 } } },
-        { T2, { .releaseId = R1, .artistIds = { A1 } } },
-    };
-    TrackCandidateEvaluator evaluator;
-    evaluator.addSoftConstraint(std::make_unique<SameReleaseConstraint>(meta), 1.F);
-    evaluator.addSoftConstraint(std::make_unique<SameArtistConstraint>(meta), 1.F);
+    TEST(TrackCandidateEvaluator, multipleSoftConstraintsAreAccumulated)
+    {
+        TrackMetadataMap meta{
+            { T1, { .releaseId = R1, .artistIds = { A1 } } },
+            { T2, { .releaseId = R1, .artistIds = { A1 } } },
+        };
+        TrackCandidateEvaluator evaluator;
+        evaluator.addSoftConstraint(std::make_unique<SameReleaseConstraint>(meta), 1.F);
+        evaluator.addSoftConstraint(std::make_unique<SameArtistConstraint>(meta), 1.F);
 
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
 
-    EXPECT_FLOAT_EQ(evaluator.score(ctx), 2.F);
-}
+        EXPECT_FLOAT_EQ(evaluator.score(ctx), 2.F);
+    }
 
-TEST(TrackCandidateEvaluator, hardConstraintPassesEvenWithSoftConstraints)
-{
-    TrackMetadataMap meta{
-        { T1, { .releaseId = R1, .artistIds = {} } },
-        { T2, { .releaseId = R1, .artistIds = {} } },
-    };
-    TrackCandidateEvaluator evaluator;
-    evaluator.addHardConstraint(std::make_unique<DuplicateTrackConstraint>());
-    evaluator.addSoftConstraint(std::make_unique<SameReleaseConstraint>(meta), 1.F);
+    TEST(TrackCandidateEvaluator, hardConstraintPassesEvenWithSoftConstraints)
+    {
+        TrackMetadataMap meta{
+            { T1, { .releaseId = R1, .artistIds = {} } },
+            { T2, { .releaseId = R1, .artistIds = {} } },
+        };
+        TrackCandidateEvaluator evaluator;
+        evaluator.addHardConstraint(std::make_unique<DuplicateTrackConstraint>());
+        evaluator.addSoftConstraint(std::make_unique<SameReleaseConstraint>(meta), 1.F);
 
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FALSE(evaluator.rejects(ctx));
-    EXPECT_FLOAT_EQ(evaluator.score(ctx), 1.F);
-}
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(evaluator.rejects(ctx));
+        EXPECT_FLOAT_EQ(evaluator.score(ctx), 1.F);
+    }
 
-namespace
-{
-    using TestVec = math::Vector<2, float>;
-    const TestVec v_x{ 1.F, 0.F };
-    const TestVec v_y{ 0.F, 1.F };
+    namespace
+    {
+        using TestVec = math::Vector<2, float>;
+        const TestVec v_x{ 1.F, 0.F };
+        const TestVec v_y{ 0.F, 1.F };
 
-    using TestConstraint = NearDuplicateEmbeddingConstraint<2>;
-    using TestVectorMap = TestConstraint::TrackVectorMap;
-} // namespace
+        using TestConstraint = NearDuplicateEmbeddingConstraint<2>;
+        using TestVectorMap = TestConstraint::TrackVectorMap;
+    } // namespace
 
-TEST(NearDuplicateEmbeddingConstraint, acceptsWhenCandidateNotInMap)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x } };
-    const TestConstraint constraint{ trackVectors, 0.1F };
-    const std::vector<db::TrackId> selected{ T1 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T2, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FALSE(constraint.rejects(ctx));
-}
+    TEST(NearDuplicateEmbeddingConstraint, acceptsWhenCandidateNotInMap)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x } };
+        const TestConstraint constraint{ trackVectors, 0.1F };
+        const std::vector<db::TrackId> selected{ T1 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T2, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
 
-TEST(NearDuplicateEmbeddingConstraint, acceptsWhenSelectionEmpty)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x } };
-    const TestConstraint constraint{ trackVectors, 0.1F };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
-    EXPECT_FALSE(constraint.rejects(ctx));
-}
+    TEST(NearDuplicateEmbeddingConstraint, acceptsWhenSelectionEmpty)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x } };
+        const TestConstraint constraint{ trackVectors, 0.1F };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
 
-TEST(NearDuplicateEmbeddingConstraint, acceptsWhenSelectedTrackNotInMap)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x } };
-    const TestConstraint constraint{ trackVectors, 0.1F };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FALSE(constraint.rejects(ctx));
-}
+    TEST(NearDuplicateEmbeddingConstraint, acceptsWhenSelectedTrackNotInMap)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x } };
+        const TestConstraint constraint{ trackVectors, 0.1F };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
 
-TEST(NearDuplicateEmbeddingConstraint, rejectsWhenDistanceBelowThreshold)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x } };
-    const TestConstraint constraint{ trackVectors, 0.1F };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_TRUE(constraint.rejects(ctx));
-}
+    TEST(NearDuplicateEmbeddingConstraint, rejectsWhenDistanceBelowThreshold)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x } };
+        const TestConstraint constraint{ trackVectors, 0.1F };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_TRUE(constraint.rejects(ctx));
+    }
 
-TEST(NearDuplicateEmbeddingConstraint, acceptsWhenDistanceAboveThreshold)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y } };
-    const TestConstraint constraint{ trackVectors, 0.1F };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FALSE(constraint.rejects(ctx));
-}
+    TEST(NearDuplicateEmbeddingConstraint, acceptsWhenDistanceAboveThreshold)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y } };
+        const TestConstraint constraint{ trackVectors, 0.1F };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
 
-TEST(NearDuplicateEmbeddingConstraint, rejectsWhenOneOfManySelectedIsNearDuplicate)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T3, &v_y }, { T4, &v_x } };
-    const TestConstraint constraint{ trackVectors, 0.1F };
-    const std::vector<db::TrackId> selected{ T3, T4 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_TRUE(constraint.rejects(ctx));
-}
+    TEST(NearDuplicateEmbeddingConstraint, rejectsWhenOneOfManySelectedIsNearDuplicate)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T3, &v_y }, { T4, &v_x } };
+        const TestConstraint constraint{ trackVectors, 0.1F };
+        const std::vector<db::TrackId> selected{ T3, T4 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_TRUE(constraint.rejects(ctx));
+    }
 
-TEST(NearDuplicateEmbeddingConstraint, acceptsWhenAllSelectedAreFarEnough)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y }, { T3, &v_y } };
-    const TestConstraint constraint{ trackVectors, 0.1F };
-    const std::vector<db::TrackId> selected{ T2, T3 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FALSE(constraint.rejects(ctx));
-}
+    TEST(NearDuplicateEmbeddingConstraint, acceptsWhenAllSelectedAreFarEnough)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y }, { T3, &v_y } };
+        const TestConstraint constraint{ trackVectors, 0.1F };
+        const std::vector<db::TrackId> selected{ T2, T3 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
 
-TEST(InterpolationFitConstraint, zeroScoreWhenNoSeeds)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x } };
-    const InterpolationFitConstraint<2> constraint{ trackVectors };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+    TEST(InterpolationFitConstraint, zeroScoreWhenNoSeeds)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x } };
+        const InterpolationFitConstraint<2> constraint{ trackVectors };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
 
-TEST(InterpolationFitConstraint, zeroScoreWhenCandidateMatchesSeed)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x } };
-    const InterpolationFitConstraint<2> constraint{ trackVectors };
-    const std::vector<db::TrackId> seeds{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+    TEST(InterpolationFitConstraint, zeroScoreWhenCandidateMatchesSeed)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x } };
+        const InterpolationFitConstraint<2> constraint{ trackVectors };
+        const std::vector<db::TrackId> seeds{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
 
-TEST(InterpolationFitConstraint, halfScoreWhenCandidateOrthogonalToSeed)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y } };
-    const InterpolationFitConstraint<2> constraint{ trackVectors };
-    const std::vector<db::TrackId> seeds{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.5F);
-}
+    TEST(InterpolationFitConstraint, halfScoreWhenCandidateOrthogonalToSeed)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y } };
+        const InterpolationFitConstraint<2> constraint{ trackVectors };
+        const std::vector<db::TrackId> seeds{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.5F);
+    }
 
-TEST(InterpolationFitConstraint, usesClosestSeed)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x }, { T3, &v_y } };
-    const InterpolationFitConstraint<2> constraint{ trackVectors };
-    const std::vector<db::TrackId> seeds{ T3, T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+    TEST(InterpolationFitConstraint, usesClosestSeed)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x }, { T3, &v_y } };
+        const InterpolationFitConstraint<2> constraint{ trackVectors };
+        const std::vector<db::TrackId> seeds{ T3, T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
 
-TEST(MaxDistanceConstraint, acceptsWhenNoSeeds)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x } };
-    const MaxDistanceConstraint<2> constraint{ trackVectors, 0.5F };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
-    EXPECT_FALSE(constraint.rejects(ctx));
-}
+    TEST(MaxDistanceConstraint, acceptsWhenNoSeeds)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x } };
+        const MaxDistanceConstraint<2> constraint{ trackVectors, 0.5F };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
 
-TEST(MaxDistanceConstraint, acceptsWhenWithinThresholdOfOneSeed)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x } };
-    const MaxDistanceConstraint<2> constraint{ trackVectors, 0.5F };
-    const std::vector<db::TrackId> seeds{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
-    EXPECT_FALSE(constraint.rejects(ctx));
-}
+    TEST(MaxDistanceConstraint, acceptsWhenWithinThresholdOfOneSeed)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x } };
+        const MaxDistanceConstraint<2> constraint{ trackVectors, 0.5F };
+        const std::vector<db::TrackId> seeds{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
 
-TEST(MaxDistanceConstraint, rejectsWhenBeyondThresholdFromAllSeeds)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y } };
-    const MaxDistanceConstraint<2> constraint{ trackVectors, 0.1F };
-    const std::vector<db::TrackId> seeds{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
-    EXPECT_TRUE(constraint.rejects(ctx));
-}
+    TEST(MaxDistanceConstraint, rejectsWhenBeyondThresholdFromAllSeeds)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y } };
+        const MaxDistanceConstraint<2> constraint{ trackVectors, 0.1F };
+        const std::vector<db::TrackId> seeds{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
+        EXPECT_TRUE(constraint.rejects(ctx));
+    }
 
-TEST(MaxDistanceConstraint, acceptsWhenAnyOfManySeedsIsCloseEnough)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y }, { T3, &v_x } };
-    const MaxDistanceConstraint<2> constraint{ trackVectors, 0.5F };
-    const std::vector<db::TrackId> seeds{ T2, T3 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
-    EXPECT_FALSE(constraint.rejects(ctx));
-}
+    TEST(MaxDistanceConstraint, acceptsWhenAnyOfManySeedsIsCloseEnough)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y }, { T3, &v_x } };
+        const MaxDistanceConstraint<2> constraint{ trackVectors, 0.5F };
+        const std::vector<db::TrackId> seeds{ T2, T3 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = seeds };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
 
-TEST(SmoothTransitionConstraint, zeroScoreWhenNoSelectedTracks)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x } };
-    const SmoothTransitionConstraint<2> constraint{ trackVectors };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+    TEST(SmoothTransitionConstraint, zeroScoreWhenNoSelectedTracks)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x } };
+        const SmoothTransitionConstraint<2> constraint{ trackVectors };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
 
-TEST(SmoothTransitionConstraint, zeroScoreWhenPreviousMatchesCandidate)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x } };
-    const SmoothTransitionConstraint<2> constraint{ trackVectors };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+    TEST(SmoothTransitionConstraint, zeroScoreWhenPreviousMatchesCandidate)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x } };
+        const SmoothTransitionConstraint<2> constraint{ trackVectors };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
 
-TEST(SmoothTransitionConstraint, halfScoreWhenPreviousOrthogonalToCandidate)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y } };
-    const SmoothTransitionConstraint<2> constraint{ trackVectors };
-    const std::vector<db::TrackId> selected{ T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.5F);
-}
+    TEST(SmoothTransitionConstraint, halfScoreWhenPreviousOrthogonalToCandidate)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_y } };
+        const SmoothTransitionConstraint<2> constraint{ trackVectors };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.5F);
+    }
 
-TEST(SmoothTransitionConstraint, usesMostRecentlySelectedTrack)
-{
-    const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x }, { T3, &v_y } };
-    const SmoothTransitionConstraint<2> constraint{ trackVectors };
-    const std::vector<db::TrackId> selected{ T3, T2 };
-    const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
-    EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
-}
+    TEST(SmoothTransitionConstraint, usesMostRecentlySelectedTrack)
+    {
+        const TestVectorMap trackVectors{ { T1, &v_x }, { T2, &v_x }, { T3, &v_y } };
+        const SmoothTransitionConstraint<2> constraint{ trackVectors };
+        const std::vector<db::TrackId> selected{ T3, T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FLOAT_EQ(constraint.computeScore(ctx), 0.F);
+    }
+
+    namespace
+    {
+        const core::UUID MBID1{ *core::UUID::fromString("3d2508f7-3a7e-4f25-895c-fca079dd71ce") };
+        const core::UUID MBID2{ *core::UUID::fromString("8e44e4ea-9bce-47c2-a48c-8aa338242fb2") };
+    } // namespace
+
+    TEST(SameRecordingMBIDConstraint, acceptsWhenCandidateNotInMap)
+    {
+        const TrackMetadataMap meta{ { T2, { .releaseId = {}, .artistIds = {}, .recordingMBID = MBID1 } } };
+        const SameRecordingMBIDConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
+
+    TEST(SameRecordingMBIDConstraint, acceptsWhenCandidateHasNoMBID)
+    {
+        const TrackMetadataMap meta{
+            { T1, { .releaseId = {}, .artistIds = {}, .recordingMBID = std::nullopt } },
+            { T2, { .releaseId = {}, .artistIds = {}, .recordingMBID = MBID1 } },
+        };
+        const SameRecordingMBIDConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
+
+    TEST(SameRecordingMBIDConstraint, acceptsWhenSelectionEmpty)
+    {
+        const TrackMetadataMap meta{ { T1, { .releaseId = {}, .artistIds = {}, .recordingMBID = MBID1 } } };
+        const SameRecordingMBIDConstraint constraint{ meta };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = {}, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
+
+    TEST(SameRecordingMBIDConstraint, acceptsWhenNoneOfSelectedHasSameMBID)
+    {
+        const TrackMetadataMap meta{
+            { T1, { .releaseId = {}, .artistIds = {}, .recordingMBID = MBID1 } },
+            { T2, { .releaseId = {}, .artistIds = {}, .recordingMBID = MBID2 } },
+        };
+        const SameRecordingMBIDConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
+
+    TEST(SameRecordingMBIDConstraint, rejectsWhenOneOfSelectedHasSameMBID)
+    {
+        const TrackMetadataMap meta{
+            { T1, { .releaseId = {}, .artistIds = {}, .recordingMBID = MBID1 } },
+            { T2, { .releaseId = {}, .artistIds = {}, .recordingMBID = MBID2 } },
+            { T3, { .releaseId = {}, .artistIds = {}, .recordingMBID = MBID1 } },
+        };
+        const SameRecordingMBIDConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2, T3 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_TRUE(constraint.rejects(ctx));
+    }
+
+    TEST(SameRecordingMBIDConstraint, acceptsWhenSelectedTrackNotInMap)
+    {
+        const TrackMetadataMap meta{ { T1, { .releaseId = {}, .artistIds = {}, .recordingMBID = MBID1 } } };
+        const SameRecordingMBIDConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
+
+    TEST(SameRecordingMBIDConstraint, acceptsWhenSelectedTrackHasNoMBID)
+    {
+        const TrackMetadataMap meta{
+            { T1, { .releaseId = {}, .artistIds = {}, .recordingMBID = MBID1 } },
+            { T2, { .releaseId = {}, .artistIds = {}, .recordingMBID = std::nullopt } },
+        };
+        const SameRecordingMBIDConstraint constraint{ meta };
+        const std::vector<db::TrackId> selected{ T2 };
+        const TrackCandidateContext ctx{ .candidateTrackId = T1, .selectedTracks = selected, .seedTrackIds = {} };
+        EXPECT_FALSE(constraint.rejects(ctx));
+    }
+} // namespace lms::recommendation::tests
\ No newline at end of file