diff --git a/.github/workflows/backend-ci.yml b/.github/workflows/backend-ci.yml
index e358f69e6..dbbc0b197 100644
--- a/.github/workflows/backend-ci.yml
+++ b/.github/workflows/backend-ci.yml
@@ -41,8 +41,30 @@ jobs:
           go install golang.org/x/vuln/cmd/govulncheck@latest
           govulncheck ./...
 
-      - name: Run unit tests
-        run: go test ./internal/handlers/... ./internal/services/... -short -coverprofile=coverage.out -covermode=atomic -timeout 5m
+      - name: Run unit tests with coverage
+        run: >
+          go test
+          ./internal/handlers/...
+          ./internal/services/...
+          ./internal/core/...
+          ./internal/middleware/...
+          -short -coverprofile=coverage.out -covermode=atomic -timeout 5m
+
+      - name: Enforce coverage threshold (>= 70%)
+        run: |
+          COVERAGE=$(go tool cover -func=coverage.out | grep '^total:' | awk '{print $NF}' | tr -d '%')
+          echo "Total coverage: ${COVERAGE}%"
+          if [ -z "$COVERAGE" ]; then
+            echo "::warning::Could not parse coverage percentage"
+            exit 0
+          fi
+          # Compare as integers (remove decimal)
+          COV_INT=$(echo "$COVERAGE" | cut -d. -f1)
+          if [ "$COV_INT" -lt 70 ]; then
+            echo "::error::Coverage ${COVERAGE}% is below the 70% threshold"
+            exit 1
+          fi
+          echo "::notice::Coverage ${COVERAGE}% meets the >= 70% threshold"
 
       - name: Upload coverage report
         uses: actions/upload-artifact@65c4c4a1ddee5b72f698fdd19549f0f0fb45cf08 # v4.6.0
@@ -50,6 +72,30 @@ jobs:
           name: go-coverage
           path: veza-backend-api/coverage.out
 
+      - name: Generate coverage badge
+        if: github.ref == 'refs/heads/main' && github.event_name == 'push'
+        run: |
+          COVERAGE=$(go tool cover -func=coverage.out | grep '^total:' | awk '{print $NF}' | tr -d '%')
+          COV_INT=$(echo "$COVERAGE" | cut -d. -f1)
+          if [ "$COV_INT" -ge 80 ]; then
+            COLOR="brightgreen"
+          elif [ "$COV_INT" -ge 70 ]; then
+            COLOR="green"
+          elif [ "$COV_INT" -ge 50 ]; then
+            COLOR="yellow"
+          else
+            COLOR="red"
+          fi
+          echo "{\"schemaVersion\":1,\"label\":\"Go coverage\",\"message\":\"${COVERAGE}%\",\"color\":\"${COLOR}\"}" > coverage-badge.json
+          echo "Coverage badge: ${COVERAGE}% (${COLOR})"
+
+      - name: Upload coverage badge
+        if: github.ref == 'refs/heads/main' && github.event_name == 'push'
+        uses: actions/upload-artifact@65c4c4a1ddee5b72f698fdd19549f0f0fb45cf08 # v4.6.0
+        with:
+          name: go-coverage-badge
+          path: veza-backend-api/coverage-badge.json
+
   test-integration:
     runs-on: ubuntu-latest
 
@@ -105,4 +151,3 @@ jobs:
 
       - name: Run integration tests
         run: go test -tags=integration ./internal/... -timeout 15m
-
diff --git a/.github/workflows/rust-ci.yml b/.github/workflows/rust-ci.yml
index da2ec1066..1a34bea15 100644
--- a/.github/workflows/rust-ci.yml
+++ b/.github/workflows/rust-ci.yml
@@ -10,13 +10,43 @@ on:
       - 'veza-stream-server/**'
 
 jobs:
-  clippy-stream:
+  test-and-lint:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - uses: dtolnay/rust-toolchain@631a55b12751854ce901bb631d5902ceb48146f7 # stable
         with:
           components: clippy
+
       - name: Clippy lint
         run: cargo clippy -- -D warnings
         working-directory: veza-stream-server
+
+      - name: Run tests
+        run: cargo test --workspace --timeout 300
+        working-directory: veza-stream-server
+
+      - name: Install cargo-tarpaulin
+        run: cargo install cargo-tarpaulin
+
+      - name: Measure coverage
+        run: cargo tarpaulin --out json --output-dir target/coverage --timeout 300 --skip-clean
+        working-directory: veza-stream-server
+
+      - name: Enforce coverage threshold (>= 50%)
+        run: |
+          COVERAGE=$(cat target/coverage/tarpaulin-report.json | python3 -c "import sys,json; print(f'{json.load(sys.stdin).get(\"coverage\", 0):.1f}')")
+          echo "Rust coverage: ${COVERAGE}%"
+          COV_INT=$(echo "$COVERAGE" | cut -d. -f1)
+          if [ "$COV_INT" -lt 50 ]; then
+            echo "::error::Rust coverage ${COVERAGE}% is below the 50% threshold"
+            exit 1
+          fi
+          echo "::notice::Rust coverage ${COVERAGE}% meets the >= 50% threshold"
+        working-directory: veza-stream-server
+
+      - name: Upload coverage report
+        uses: actions/upload-artifact@65c4c4a1ddee5b72f698fdd19549f0f0fb45cf08 # v4.6.0
+        with:
+          name: rust-coverage
+          path: veza-stream-server/target/coverage/tarpaulin-report.json
diff --git a/VEZA_VERSIONS_ROADMAP.md b/VEZA_VERSIONS_ROADMAP.md
index 8c535feb5..dd792ccdb 100644
--- a/VEZA_VERSIONS_ROADMAP.md
+++ b/VEZA_VERSIONS_ROADMAP.md
@@ -1285,7 +1285,8 @@ Le diagnostic audit a identifié 9 modules "fantômes" — du code présent dans
 
 ### v0.12.9 — Tests Éthiques & Coverage CI
 
-**Statut** : ⏳ TODO
+**Statut** : ✅ DONE
+**Complété le** : 2026-03-12
 **Priorité** : P1
 **Durée estimée** : 2-3 jours
 **Prerequisite** : v0.12.6.3 complète
@@ -1295,21 +1296,29 @@ Les tests de biais éthiques exigés par les specs sont absents. La coverage n'e
 
 **Tâches**
 
-- [ ] **TASK-ETH-001** : Test de biais artistes émergents (critère v0.10.1 non coché)
-  - La découverte ne doit pas défavoriser les artistes avec 0 ou peu de contenus
-- [ ] **TASK-ETH-002** : Test recherche artiste 0 plays (critère v0.10.2 non coché)
-  - Un artiste avec 0 plays doit apparaître dans les résultats de recherche par nom
-- [ ] **TASK-ETH-003** : Documenter l'algorithme de découverte
+- [x] **TASK-ETH-001** : Test de biais artistes émergents (critère v0.10.1 non coché)
+  - 3 tests : `TestDiscovery_NoPlayCountBias_GenreBrowse`, `_TagBrowse`, `_EmergingArtistVisibility`
+  - Vérifie l'ordre chronologique (created_at DESC) dans GetTracksByGenre et GetTracksByTag
+  - Track 0 plays apparaît en premier si plus récent qu'un track avec 1M+ plays
+- [x] **TASK-ETH-002** : Test recherche artiste 0 plays (critère v0.10.2 non coché)
+  - 4 tests : `TestSearch_ArtistZeroPlays_Discoverable`, `_ZeroPlaysTrack_NotFilteredOut`, `_DefaultSortIsChronological`, `_NoPopularityBias_InDefaultRanking`
+  - Vérifie qu'un artiste avec 0 plays est trouvable par nom
+  - Vérifie que le tri par défaut est chronologique, pas par popularité
+- [x] **TASK-ETH-003** : Documenter l'algorithme de découverte
   - Fichier: `veza-docs/DISCOVERY_ALGORITHM.md`
-- [ ] **TASK-COV-001** : Configurer coverage CI (Go + Rust)
-  - Quality gate: coverage >= 70% Go, >= 50% Rust
-- [ ] **TASK-COV-002** : Rapport coverage global avec badge
+  - Documente les 6 mécanismes de découverte, les interdictions éthiques, et les tests de garantie
+- [x] **TASK-COV-001** : Configurer coverage CI (Go + Rust)
+  - Go : ajout quality gate >= 70% dans backend-ci.yml (coverage étendue à core/ et middleware/)
+  - Rust : ajout cargo test + cargo-tarpaulin avec quality gate >= 50% dans rust-ci.yml
+- [x] **TASK-COV-002** : Rapport coverage global avec badge
+  - Badge JSON généré sur push main (shields.io compatible)
+  - Artifacts uploadés : go-coverage, go-coverage-badge, rust-coverage
 
 **Critères d'acceptation**
-- [ ] Test de biais artistes émergents PASSE
-- [ ] Test recherche artiste 0 plays PASSE
-- [ ] Algorithme de découverte documenté
-- [ ] Coverage mesurée et enforcée en CI (>= 70% Go, >= 50% Rust)
+- [x] Test de biais artistes émergents PASSE (4 tests discover, tous PASS)
+- [x] Test recherche artiste 0 plays PASSE (4 tests search, tous PASS)
+- [x] Algorithme de découverte documenté (`veza-docs/DISCOVERY_ALGORITHM.md`)
+- [x] Coverage mesurée et enforcée en CI (>= 70% Go, >= 50% Rust)
 
 ---
 
@@ -1577,7 +1586,7 @@ Toutes les conditions suivantes doivent être remplies avant de taguer v1.0.0 :
 | v0.12.6.3 | Nettoyage Code Fantôme | P1 | ✅ DONE | 1-2j | v0.12.6 |
 | v0.12.7 | Internationalisation | P1 | ⏳ TODO | 3-4j | v0.12.5 |
 | v0.12.8 | Documentation & API Publique | P1 | ⏳ TODO | 3-4j | v0.12.6 |
-| v0.12.9 | Tests Éthiques & Coverage CI | P1 | ⏳ TODO | 2-3j | v0.12.6.3 |
+| v0.12.9 | Tests Éthiques & Coverage CI | P1 | ✅ DONE | 2-3j | v0.12.6.3 |
 | v0.13.0 | Conformité Features Partielles | P2 | ⏳ TODO | 5-7j | v0.12.9 |
 | v0.13.1 | Conformité Audio & Player | P2 | ⏳ TODO | 4-5j | v0.13.0 |
 | v0.13.2 | Consolidation Design System | P2 | ⏳ TODO | 2-3j | v0.13.0 |
diff --git a/veza-backend-api/internal/core/discover/ethical_bias_test.go b/veza-backend-api/internal/core/discover/ethical_bias_test.go
new file mode 100644
index 000000000..082356055
--- /dev/null
+++ b/veza-backend-api/internal/core/discover/ethical_bias_test.go
@@ -0,0 +1,209 @@
+package discover
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+	"time"
+
+	"veza-backend-api/internal/models"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap"
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+)
+
+func setupTestDiscoverService(t *testing.T) (*Service, *gorm.DB) {
+	t.Helper()
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	require.NoError(t, err)
+
+	err = db.AutoMigrate(
+		&models.User{},
+		&models.Track{},
+		&models.Genre{},
+		&models.TrackGenre{},
+		&models.Tag{},
+		&models.TrackTag{},
+		&models.UserGenreFollow{},
+		&models.UserTagFollow{},
+	)
+	require.NoError(t, err)
+
+	service := NewService(db, zap.NewNop())
+	return service, db
+}
+
+// createTestTrackWithPlays creates a track with explicit play_count and created_at.
+func createTestTrackWithPlays(t *testing.T, db *gorm.DB, userID uuid.UUID, title string, playCount int64, createdAt time.Time) *models.Track {
+	t.Helper()
+	track := &models.Track{
+		UserID:    userID,
+		Title:     title,
+		Artist:    "Test Artist",
+		FilePath:  "/test/" + title + ".mp3",
+		FileSize:  5 * 1024 * 1024,
+		Format:    "MP3",
+		Duration:  180,
+		IsPublic:  true,
+		Status:    models.TrackStatusCompleted,
+		PlayCount: playCount,
+		CreatedAt: createdAt,
+	}
+	err := db.Create(track).Error
+	require.NoError(t, err)
+	return track
+}
+
+// TestDiscovery_NoPlayCountBias_GenreBrowse verifies that GetTracksByGenre
+// returns tracks in strict chronological order, regardless of play counts.
+// TASK-ETH-001: ORIGIN_BUSINESS_LOGIC.md — discovery must NOT favor popular tracks.
+func TestDiscovery_NoPlayCountBias_GenreBrowse(t *testing.T) {
+	service, db := setupTestDiscoverService(t)
+	ctx := context.Background()
+
+	userID := uuid.New()
+	err := db.Create(&models.User{ID: userID, Username: "artist1", Email: "a1@test.com", IsActive: true}).Error
+	require.NoError(t, err)
+
+	err = db.Create(&models.Genre{Slug: "electronic", Name: "Electronic"}).Error
+	require.NoError(t, err)
+
+	now := time.Now()
+
+	// Track A: emerging artist, 0 plays, uploaded MOST RECENTLY
+	trackA := createTestTrackWithPlays(t, db, userID, "Hidden Gem", 0, now)
+	err = db.Create(&models.TrackGenre{TrackID: trackA.ID, GenreSlug: "electronic", Position: 0}).Error
+	require.NoError(t, err)
+
+	// Track B: viral hit, 1M plays, uploaded 1 hour ago
+	trackB := createTestTrackWithPlays(t, db, userID, "Viral Hit", 1_000_000, now.Add(-1*time.Hour))
+	err = db.Create(&models.TrackGenre{TrackID: trackB.ID, GenreSlug: "electronic", Position: 0}).Error
+	require.NoError(t, err)
+
+	// Track C: moderate track, 500 plays, uploaded 2 hours ago
+	trackC := createTestTrackWithPlays(t, db, userID, "Moderate Track", 500, now.Add(-2*time.Hour))
+	err = db.Create(&models.TrackGenre{TrackID: trackC.ID, GenreSlug: "electronic", Position: 0}).Error
+	require.NoError(t, err)
+
+	// Fetch discovery by genre
+	tracks, _, err := service.GetTracksByGenre(ctx, "electronic", 10, "")
+	require.NoError(t, err)
+	require.Len(t, tracks, 3)
+
+	// ETHICAL ASSERTION: order must be chronological (newest first),
+	// NOT by play count. The 0-play track MUST appear first.
+	assert.Equal(t, trackA.ID, tracks[0].ID, "newest track (0 plays) must appear first — no play-count bias")
+	assert.Equal(t, trackB.ID, tracks[1].ID, "second newest (1M plays) must appear second")
+	assert.Equal(t, trackC.ID, tracks[2].ID, "oldest track must appear last regardless of play count")
+}
+
+// TestDiscovery_NoPlayCountBias_TagBrowse verifies that GetTracksByTag
+// returns tracks in strict chronological order, regardless of play counts.
+// TASK-ETH-001: same principle applied to tag-based discovery.
+func TestDiscovery_NoPlayCountBias_TagBrowse(t *testing.T) {
+	service, db := setupTestDiscoverService(t)
+	ctx := context.Background()
+
+	userID := uuid.New()
+	err := db.Create(&models.User{ID: userID, Username: "artist2", Email: "a2@test.com", IsActive: true}).Error
+	require.NoError(t, err)
+
+	tagID := uuid.New()
+	err = db.Create(&models.Tag{ID: tagID, Name: "ambient"}).Error
+	require.NoError(t, err)
+
+	now := time.Now()
+
+	// Track with 0 plays (newest)
+	trackNew := createTestTrackWithPlays(t, db, userID, "New Ambient", 0, now)
+	err = db.Create(&models.TrackTag{TrackID: trackNew.ID, TagID: tagID}).Error
+	require.NoError(t, err)
+
+	// Track with 50000 plays (older)
+	trackOld := createTestTrackWithPlays(t, db, userID, "Popular Ambient", 50_000, now.Add(-3*time.Hour))
+	err = db.Create(&models.TrackTag{TrackID: trackOld.ID, TagID: tagID}).Error
+	require.NoError(t, err)
+
+	tracks, _, err := service.GetTracksByTag(ctx, "ambient", 10, "")
+	require.NoError(t, err)
+	require.Len(t, tracks, 2)
+
+	// ETHICAL ASSERTION: chronological order, not popularity
+	assert.Equal(t, trackNew.ID, tracks[0].ID, "0-play track must appear first (newest)")
+	assert.Equal(t, trackOld.ID, tracks[1].ID, "50k-play track must appear second (older)")
+}
+
+// TestDiscovery_EmergingArtistVisibility verifies that tracks from an artist
+// with zero total plays appear alongside tracks from established artists.
+// TASK-ETH-001: ORIGIN_FEATURES_REGISTRY.md F351-F355.
+func TestDiscovery_EmergingArtistVisibility(t *testing.T) {
+	service, db := setupTestDiscoverService(t)
+	ctx := context.Background()
+
+	// Emerging artist: 0 total plays across all tracks
+	emergingID := uuid.New()
+	err := db.Create(&models.User{ID: emergingID, Username: "emerging_artist", Email: "emerging@test.com", IsActive: true}).Error
+	require.NoError(t, err)
+
+	// Established artist: many plays
+	establishedID := uuid.New()
+	err = db.Create(&models.User{ID: establishedID, Username: "established_star", Email: "star@test.com", IsActive: true}).Error
+	require.NoError(t, err)
+
+	err = db.Create(&models.Genre{Slug: "jazz", Name: "Jazz"}).Error
+	require.NoError(t, err)
+
+	now := time.Now()
+
+	// Emerging artist's track (newest, 0 plays)
+	emergingTrack := createTestTrackWithPlays(t, db, emergingID, "First Song Ever", 0, now)
+	err = db.Create(&models.TrackGenre{TrackID: emergingTrack.ID, GenreSlug: "jazz", Position: 0}).Error
+	require.NoError(t, err)
+
+	// Established artist's track (older, 2M plays)
+	starTrack := createTestTrackWithPlays(t, db, establishedID, "Greatest Hit", 2_000_000, now.Add(-30*time.Minute))
+	err = db.Create(&models.TrackGenre{TrackID: starTrack.ID, GenreSlug: "jazz", Position: 0}).Error
+	require.NoError(t, err)
+
+	tracks, _, err := service.GetTracksByGenre(ctx, "jazz", 10, "")
+	require.NoError(t, err)
+	require.Len(t, tracks, 2)
+
+	// ETHICAL ASSERTION: emerging artist's track is NOT pushed down
+	assert.Equal(t, emergingTrack.ID, tracks[0].ID, "emerging artist's newer track must not be demoted by popularity")
+	assert.Equal(t, starTrack.ID, tracks[1].ID)
+}
+
+// TestDiscovery_MetricsNotExposedInJSON verifies that play_count and like_count
+// are not serialized in JSON responses (json:"-" tag).
+// ORIGIN_UI_UX_SYSTEM.md §14.2: metrics are PRIVATE, visible only to creator.
+func TestDiscovery_MetricsNotExposedInJSON(t *testing.T) {
+	track := models.Track{
+		ID:        uuid.New(),
+		Title:     "Test Track",
+		Artist:    "Test Artist",
+		PlayCount: 999999,
+		LikeCount: 50000,
+	}
+
+	data, err := json.Marshal(track)
+	require.NoError(t, err)
+
+	var parsed map[string]interface{}
+	err = json.Unmarshal(data, &parsed)
+	require.NoError(t, err)
+
+	// play_count and like_count must NOT appear in JSON output
+	_, hasPlayCount := parsed["play_count"]
+	_, hasLikeCount := parsed["like_count"]
+	assert.False(t, hasPlayCount, "play_count must not be exposed in JSON (json:\"-\" tag required)")
+	assert.False(t, hasLikeCount, "like_count must not be exposed in JSON (json:\"-\" tag required)")
+
+	// But title and artist should be present
+	assert.Equal(t, "Test Track", parsed["title"])
+	assert.Equal(t, "Test Artist", parsed["artist"])
+}
diff --git a/veza-backend-api/internal/services/ethical_search_test.go b/veza-backend-api/internal/services/ethical_search_test.go
new file mode 100644
index 000000000..7fb3010d6
--- /dev/null
+++ b/veza-backend-api/internal/services/ethical_search_test.go
@@ -0,0 +1,268 @@
+package services
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"veza-backend-api/internal/models"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+)
+
+// TestSearch_ArtistZeroPlays_Discoverable verifies that an artist with 0 plays
+// appears in search results when searched by name.
+// TASK-ETH-002: ORIGIN_FEATURES_REGISTRY.md F375 — search must not require play count.
+func TestSearch_ArtistZeroPlays_Discoverable(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	require.NoError(t, err)
+	err = db.AutoMigrate(&models.Track{}, &models.User{})
+	require.NoError(t, err)
+
+	service := NewTrackSearchService(db)
+	ctx := context.Background()
+
+	// Artist with 0 plays — emerging artist
+	emergingID := uuid.New()
+	err = db.Create(&models.User{ID: emergingID, Username: "emerging_talent", Email: "emerging@test.com", IsActive: true}).Error
+	require.NoError(t, err)
+
+	// Create track with 0 plays
+	track := &models.Track{
+		UserID:    emergingID,
+		Title:     "My First Song",
+		Artist:    "emerging_talent",
+		FilePath:  "/test/first.mp3",
+		FileSize:  4 * 1024 * 1024,
+		Format:    "MP3",
+		Duration:  200,
+		IsPublic:  true,
+		Status:    models.TrackStatusCompleted,
+		PlayCount: 0,
+		LikeCount: 0,
+	}
+	err = db.Create(track).Error
+	require.NoError(t, err)
+
+	// Search by artist name
+	results, total, err := service.SearchTracks(ctx, TrackSearchParams{
+		Query: "emerging_talent",
+		Page:  1,
+		Limit: 10,
+	})
+
+	require.NoError(t, err)
+	assert.Equal(t, int64(1), total, "artist with 0 plays must appear in search results")
+	require.Len(t, results, 1)
+	assert.Equal(t, "My First Song", results[0].Title)
+}
+
+// TestSearch_ZeroPlaysTrack_NotFilteredOut verifies that tracks with 0 play count
+// are not filtered from search results by any implicit popularity filter.
+// TASK-ETH-002: no play-count minimum for searchability.
+func TestSearch_ZeroPlaysTrack_NotFilteredOut(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	require.NoError(t, err)
+	err = db.AutoMigrate(&models.Track{}, &models.User{})
+	require.NoError(t, err)
+
+	service := NewTrackSearchService(db)
+	ctx := context.Background()
+
+	userID := uuid.New()
+	err = db.Create(&models.User{ID: userID, Username: "testuser", Email: "t@test.com", IsActive: true}).Error
+	require.NoError(t, err)
+
+	now := time.Now()
+
+	// Create tracks with varying play counts
+	tracks := []struct {
+		title     string
+		playCount int64
+		createdAt time.Time
+	}{
+		{"Zero Plays Song", 0, now},
+		{"One Play Song", 1, now.Add(-1 * time.Hour)},
+		{"Popular Song", 100_000, now.Add(-2 * time.Hour)},
+	}
+
+	for _, tc := range tracks {
+		err = db.Create(&models.Track{
+			UserID:    userID,
+			Title:     tc.title,
+			Artist:    "Test Artist",
+			FilePath:  "/test/" + tc.title + ".mp3",
+			FileSize:  5 * 1024 * 1024,
+			Format:    "MP3",
+			Duration:  180,
+			IsPublic:  true,
+			Status:    models.TrackStatusCompleted,
+			PlayCount: tc.playCount,
+			CreatedAt: tc.createdAt,
+		}).Error
+		require.NoError(t, err)
+	}
+
+	// Search for "Song" — all 3 must appear regardless of play count
+	results, total, err := service.SearchTracks(ctx, TrackSearchParams{
+		Query: "Song",
+		Page:  1,
+		Limit: 10,
+	})
+
+	require.NoError(t, err)
+	assert.Equal(t, int64(3), total, "all tracks must appear regardless of play count")
+	assert.Len(t, results, 3)
+
+	// Verify all titles are present
+	titles := make([]string, len(results))
+	for i, r := range results {
+		titles[i] = r.Title
+	}
+	assert.Contains(t, titles, "Zero Plays Song", "0-play track must be in results")
+	assert.Contains(t, titles, "One Play Song", "1-play track must be in results")
+	assert.Contains(t, titles, "Popular Song", "popular track must be in results")
+}
+
+// TestSearch_DefaultSortIsChronological verifies that the default sort order
+// is created_at DESC (chronological), not by popularity or engagement.
+// TASK-ETH-002: ORIGIN_BUSINESS_LOGIC.md — no engagement optimization.
+func TestSearch_DefaultSortIsChronological(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	require.NoError(t, err)
+	err = db.AutoMigrate(&models.Track{}, &models.User{})
+	require.NoError(t, err)
+
+	service := NewTrackSearchService(db)
+	ctx := context.Background()
+
+	userID := uuid.New()
+	err = db.Create(&models.User{ID: userID, Username: "testuser", Email: "t@test.com", IsActive: true}).Error
+	require.NoError(t, err)
+
+	now := time.Now()
+
+	// Create tracks: popular one is oldest, unpopular one is newest
+	oldPopular := &models.Track{
+		UserID:    userID,
+		Title:     "Old Popular",
+		Artist:    "Artist",
+		FilePath:  "/test/old.mp3",
+		FileSize:  5 * 1024 * 1024,
+		Format:    "MP3",
+		Duration:  180,
+		IsPublic:  true,
+		Status:    models.TrackStatusCompleted,
+		PlayCount: 1_000_000,
+		CreatedAt: now.Add(-24 * time.Hour),
+	}
+	err = db.Create(oldPopular).Error
+	require.NoError(t, err)
+
+	newUnpopular := &models.Track{
+		UserID:    userID,
+		Title:     "New Unpopular",
+		Artist:    "Artist",
+		FilePath:  "/test/new.mp3",
+		FileSize:  5 * 1024 * 1024,
+		Format:    "MP3",
+		Duration:  180,
+		IsPublic:  true,
+		Status:    models.TrackStatusCompleted,
+		PlayCount: 0,
+		CreatedAt: now,
+	}
+	err = db.Create(newUnpopular).Error
+	require.NoError(t, err)
+
+	// Default search (no SortBy specified) — should be created_at DESC
+	results, _, err := service.SearchTracks(ctx, TrackSearchParams{
+		Page:  1,
+		Limit: 10,
+	})
+
+	require.NoError(t, err)
+	require.Len(t, results, 2)
+	assert.Equal(t, "New Unpopular", results[0].Title, "default sort must be chronological (newest first), not popularity")
+	assert.Equal(t, "Old Popular", results[1].Title)
+}
+
+// TestSearch_NoPopularityBias_InDefaultRanking verifies that when no sort
+// is specified, results are not biased by play_count or like_count.
+// TASK-ETH-002: ethical search — equal visibility for all artists.
+func TestSearch_NoPopularityBias_InDefaultRanking(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	require.NoError(t, err)
+	err = db.AutoMigrate(&models.Track{}, &models.User{})
+	require.NoError(t, err)
+
+	service := NewTrackSearchService(db)
+	ctx := context.Background()
+
+	// Two different artists
+	emergingID := uuid.New()
+	err = db.Create(&models.User{ID: emergingID, Username: "new_artist", Email: "new@test.com", IsActive: true}).Error
+	require.NoError(t, err)
+
+	starID := uuid.New()
+	err = db.Create(&models.User{ID: starID, Username: "mega_star", Email: "star@test.com", IsActive: true}).Error
+	require.NoError(t, err)
+
+	now := time.Now()
+
+	// Emerging artist's track (newest, genre=jazz)
+	err = db.Create(&models.Track{
+		UserID:    emergingID,
+		Title:     "Jazz Improvisation",
+		Artist:    "new_artist",
+		FilePath:  "/test/jazz1.mp3",
+		FileSize:  5 * 1024 * 1024,
+		Format:    "MP3",
+		Duration:  300,
+		Genre:     "jazz",
+		IsPublic:  true,
+		Status:    models.TrackStatusCompleted,
+		PlayCount: 0,
+		LikeCount: 0,
+		CreatedAt: now,
+	}).Error
+	require.NoError(t, err)
+
+	// Star's track (older, genre=jazz)
+	err = db.Create(&models.Track{
+		UserID:    starID,
+		Title:     "Jazz Standards",
+		Artist:    "mega_star",
+		FilePath:  "/test/jazz2.mp3",
+		FileSize:  5 * 1024 * 1024,
+		Format:    "MP3",
+		Duration:  250,
+		Genre:     "jazz",
+		IsPublic:  true,
+		Status:    models.TrackStatusCompleted,
+		PlayCount: 5_000_000,
+		LikeCount: 200_000,
+		CreatedAt: now.Add(-1 * time.Hour),
+	}).Error
+	require.NoError(t, err)
+
+	// Search for "Jazz" — default sort
+	genre := "jazz"
+	results, _, err := service.SearchTracks(ctx, TrackSearchParams{
+		Genre: &genre,
+		Page:  1,
+		Limit: 10,
+	})
+
+	require.NoError(t, err)
+	require.Len(t, results, 2)
+
+	// ETHICAL ASSERTION: emerging artist's newer track must come first
+	// when using default sort (chronological), despite having 0 plays vs 5M
+	assert.Equal(t, "Jazz Improvisation", results[0].Title,
+		"emerging artist's track must rank first (chronological default), not star's track with 5M plays")
+}
diff --git a/veza-docs/DISCOVERY_ALGORITHM.md b/veza-docs/DISCOVERY_ALGORITHM.md
new file mode 100644
index 000000000..84afbeb47
--- /dev/null
+++ b/veza-docs/DISCOVERY_ALGORITHM.md
@@ -0,0 +1,131 @@
+# Algorithme de Découverte Veza
+
+> **Version** : v0.12.9
+> **Dernière mise à jour** : 2026-03-12
+> **Référence** : ORIGIN_BUSINESS_LOGIC.md §11, ORIGIN_FEATURES_REGISTRY.md F351-F375, ORIGIN_UI_UX_SYSTEM.md §13-14
+
+---
+
+## Principes fondamentaux
+
+L'algorithme de découverte de Veza est conçu selon des principes éthiques stricts :
+
+1. **Chronologique, pas algorithmique** — Le feed et la découverte sont ordonnés par date de création (du plus récent au plus ancien). Aucun critère d'engagement (play count, likes, partages) n'influence l'ordre d'affichage.
+
+2. **Pas de ML/IA** — Aucun algorithme de machine learning (collaborative filtering, content-based filtering, analyse prédictive) n'est utilisé. La découverte repose exclusivement sur des mécanismes déclaratifs et humains.
+
+3. **Visibilité égale** — Un artiste émergent avec 0 écoutes a exactement la même chance d'apparaître qu'un artiste établi avec des millions d'écoutes, à condition qu'il soit dans le même genre/tag et que son contenu soit plus récent.
+
+4. **Métriques privées** — Les compteurs d'écoutes, likes et followers ne sont JAMAIS visibles publiquement. Ils sont réservés exclusivement au créateur dans son tableau de bord analytics.
+
+---
+
+## Mécanismes de découverte
+
+### 1. Feed personnel (chronologique)
+
+**Implémentation** : `internal/core/feed/service.go`
+
+Le feed d'un utilisateur affiche les tracks des artistes qu'il suit, triées par `created_at DESC`.
+
+```
+Requête : SELECT tracks.*
+         FROM tracks
+         INNER JOIN follows ON follows.followed_id = tracks.creator_id
+         WHERE follows.follower_id = :user_id
+         ORDER BY tracks.created_at DESC, tracks.id DESC
+```
+
+Aucun facteur de popularité n'intervient. L'ordre est strictement chronologique.
+
+### 2. Découverte par genre (F353)
+
+**Implémentation** : `internal/core/discover/service.go` — `GetTracksByGenre()`
+
+Browse par genre avec pagination curseur. Tri : `created_at DESC, id DESC`.
+
+```
+Requête : SELECT tracks.*
+         FROM tracks
+         INNER JOIN track_genres ON track_genres.track_id = tracks.id
+         WHERE track_genres.genre_slug = :slug
+           AND tracks.status = 'completed'
+           AND tracks.is_public = true
+         ORDER BY tracks.created_at DESC, tracks.id DESC
+```
+
+### 3. Découverte par tag (F353)
+
+**Implémentation** : `internal/core/discover/service.go` — `GetTracksByTag()`
+
+Même principe que par genre, avec les tags déclarés par l'artiste.
+
+### 4. Nouveautés des genres suivis (F355)
+
+**Implémentation** : `internal/core/discover/service.go` — `GetTracksFromFollowedGenres()`
+
+Affiche les tracks récentes dans les genres que l'utilisateur suit. Tri chronologique.
+
+### 5. Playlists éditoriales (F141)
+
+**Implémentation** : `internal/core/discover/service.go` — `GetEditorialPlaylists()`
+
+Playlists créées manuellement par l'équipe de curation. Aucune génération automatique.
+
+### 6. Recherche textuelle (F375)
+
+**Implémentation** :
+- PostgreSQL : `internal/services/search_service.go` (ILIKE pattern matching)
+- Elasticsearch : `internal/elasticsearch/search_service.go` (BM25 + fuzziness)
+
+La recherche utilise la pertinence textuelle (BM25 sur Elasticsearch, ILIKE sur PostgreSQL). Le commentaire dans le code est explicite :
+
+```go
+// F364: fuzziness for typo tolerance; no boost by popularity (ethical)
+```
+
+Les champs boostés sont `title^2` et `artist^2` — c'est un boost de pertinence textuelle, PAS de popularité.
+
+---
+
+## Ce qui est explicitement INTERDIT
+
+| Mécanisme | Raison de l'interdiction | Référence |
+|-----------|-------------------------|-----------|
+| Collaborative filtering | Optimise la rétention, pas la découverte authentique | ORIGIN_BUSINESS_LOGIC.md §11 |
+| Content-based filtering ML | Crée des bulles de filtrage | ORIGIN_BUSINESS_LOGIC.md §11 |
+| Analyse prédictive du comportement | Manipulation de l'engagement | ORIGIN_BUSINESS_LOGIC.md §11 |
+| Trending basé sur play counts | Favorise les artistes établis | ORIGIN_UI_UX_SYSTEM.md §13 |
+| "X personnes écoutent maintenant" | Dark pattern FOMO | ORIGIN_UI_UX_SYSTEM.md §13 |
+| Compteurs publics de followers | Biais de preuve sociale | ORIGIN_UI_UX_SYSTEM.md §13 |
+| Leaderboards/classements | Gamification interdite | CLAUDE.md règle #3 |
+| Badges de performance | XP/streaks interdits | CLAUDE.md règle #3 |
+
+---
+
+## Garanties éthiques testées
+
+Les tests suivants vérifient en continu le respect de ces principes :
+
+| Test | Fichier | Ce qu'il vérifie |
+|------|---------|-----------------|
+| `TestDiscovery_NoPlayCountBias_GenreBrowse` | `discover/ethical_bias_test.go` | Genre browse : ordre chronologique, pas par play count |
+| `TestDiscovery_NoPlayCountBias_TagBrowse` | `discover/ethical_bias_test.go` | Tag browse : même vérification |
+| `TestDiscovery_EmergingArtistVisibility` | `discover/ethical_bias_test.go` | Artiste 0 plays non défavorisé |
+| `TestDiscovery_MetricsNotExposedInJSON` | `discover/ethical_bias_test.go` | play_count/like_count absents du JSON |
+| `TestSearch_ArtistZeroPlays_Discoverable` | `services/ethical_search_test.go` | Artiste 0 plays trouvable par nom |
+| `TestSearch_ZeroPlaysTrack_NotFilteredOut` | `services/ethical_search_test.go` | Track 0 plays non filtré |
+| `TestSearch_DefaultSortIsChronological` | `services/ethical_search_test.go` | Tri par défaut = chronologique |
+| `TestSearch_NoPopularityBias_InDefaultRanking` | `services/ethical_search_test.go` | Pas de biais popularité dans le ranking par défaut |
+
+---
+
+## Audit et transparence
+
+Cet algorithme est :
+- **Documenté** : ce fichier constitue la documentation publique
+- **Auditable** : le code source est lisible et les requêtes SQL sont explicites
+- **Testé** : les tests éthiques ci-dessus sont exécutés en CI
+- **Déterministe** : pas de composante aléatoire ou opaque
+
+Toute modification de l'algorithme de découverte doit passer les tests éthiques existants et être documentée ici.