diff --git a/cmd/server/main.go b/cmd/server/main.go
index 2a15fc98..abd96908 100644
--- a/cmd/server/main.go
+++ b/cmd/server/main.go
@@ -170,8 +170,12 @@ func main() {
 	opdsHandler := handlers.NewOPDSHandler(queries, libraryService, conversionService)
 	opdsHandler.SetSettings(registry)
 
-	collectionHandler := handlers.NewCollectionHandler(queries, libraryService, connManager)
-	dashboardService := services.NewDashboardService(queries)
+	// One composed-engine service shared by search AND the collection
+	// subsystem (item 3.2): tree-driven smart collections evaluate
+	// through the unified engine.
+	collectionSearchService := services.NewSearchService(queries, scopedDB)
+	collectionHandler := handlers.NewCollectionHandler(queries, libraryService, connManager, collectionSearchService)
+	dashboardService := services.NewDashboardService(queries, collectionSearchService)
 	dashboardHandler := handlers.NewDashboardHandler(queries)
 	seriesHandler := handlers.NewSeriesHandler(queries)
 	filtersHandler := handlers.NewFiltersHandler(queries)
diff --git a/cmd/server/tests/contract_pins_test.go b/cmd/server/tests/contract_pins_test.go
index 245ab6c8..889fdad3 100644
--- a/cmd/server/tests/contract_pins_test.go
+++ b/cmd/server/tests/contract_pins_test.go
@@ -503,6 +503,7 @@ func TestContractPin_CollectionsJSON(t *testing.T) {
 		"auto_assign_rules", "view_settings", "books", "book_count",
 		"is_smart", "created_at", "up_next",
 		"rule_match_mode", // item-2.4 widening (docs/contract_pins.md)
+		"filter_tree",     // item-3.2 widening (docs/contract_pins.md)
 	}
 
 	t.Run("user collection with library_id (badged branch)", func(t *testing.T) {
diff --git a/cmd/server/tests/podcast_test.go b/cmd/server/tests/podcast_test.go
index 7a2c0b8d..bed726cf 100644
--- a/cmd/server/tests/podcast_test.go
+++ b/cmd/server/tests/podcast_test.go
@@ -952,6 +952,125 @@ func TestPodcastSmartCollections(t *testing.T) {
 	})
 }
 
+// TestEpisodeCollectionsFilterTree pins item 3.2: smart collections
+// WITH A FILTER TREE evaluate through the unified engine; the briefing
+// rules ride the qf DSL; the reader chain follows the tree's live
+// membership; the tree wins when legacy rules coexist; edits without a
+// tree keep the stored one.
+func TestEpisodeCollectionsFilterTree(t *testing.T) {
+	setup := setupTestServer(t)
+	regUUID := getRegularUserID(t, setup.DB)
+	regToken := setup.RegularToken
+
+	lib, _ := createPodcastsLibrary(t, setup, "test TreeColl Podcasts")
+	marker := fmt.Sprintf("treecoll%d", time.Now().UnixNano()%100000)
+
+	feedA, err := setup.DB.CreatePodcastFeed(adminSeedCtx(t, setup), database.CreatePodcastFeedParams{
+		LibraryID: lib.ID,
+		FeedUrl:   "https://feed.invalid/" + marker + "-a.xml",
+		Title:     "TreeColl Feed A " + marker,
+	})
+	require.NoError(t, err)
+	aNew := upsertTestEpisode(t, setup, feedA, marker+"-new", "TreeColl New", 1)
+	aNew2 := upsertTestEpisode(t, setup, feedA, marker+"-new2", "TreeColl New Two", 5)
+	aOld := upsertTestEpisode(t, setup, feedA, marker+"-old", "TreeColl Old", 9)
+	adminScopeExec(t, setup, adminCtxValue(t, setup), `
+		UPDATE media_items SET download_state = 'downloaded', file_size = 1000,
+		       date_published = CURRENT_DATE WHERE id IN ($1, $2)`, aNew.ID, aNew2.ID)
+	adminScopeExec(t, setup, adminCtxValue(t, setup), `
+		UPDATE media_items SET download_state = 'downloaded', file_size = 1000,
+		       date_published = CURRENT_DATE - 30 WHERE id = $1`, aOld.ID)
+	subscribeRaw(t, setup, regUUID, feedA.ID)
+
+	feedAID := uuid.UUID(feedA.ID.Bytes).String()
+	// Sequence config rides a data-json attribute — templ escapes quotes.
+	esc := func(s string) string { return strings.ReplaceAll(s, `"`, """) }
+
+	// The Daily Fiction briefing AS A TREE (item 2.5's shape, unified DSL).
+	briefing, _ := json.Marshal(map[string]interface{}{
+		"scope": "episodes", "mode": "all",
+		"children": []map[string]interface{}{
+			{"field": "feed", "op": "in", "values": []string{feedAID}},
+			{"field": "played", "op": "is_false"},
+			{"field": "published_date", "op": "within_days", "values": []string{"7"}},
+		},
+	})
+
+	code, body := podcastAuthed(t, setup, regToken, "POST", "/api/collections",
+		`{"name":"test TreeColl `+marker+`","filter_tree":`+string(briefing)+`}`)
+	require.Equal(t, http.StatusCreated, code, "%s", string(body))
+	var coll struct {
+		ID string `json:"id"`
+	}
+	require.NoError(t, json.Unmarshal(body, &coll))
+	collID := coll.ID
+	t.Cleanup(func() {
+		podcastAuthed(t, setup, regToken, "DELETE", "/api/collections/"+collID, "")
+	})
+
+	t.Run("tree_evaluates_through_the_engine", func(t *testing.T) {
+		code, body := podcastAuthed(t, setup, regToken, "GET", "/api/collections/"+collID, "")
+		require.Equal(t, http.StatusOK, code)
+		var out struct {
+			IsSmart bool        `json:"is_smart"`
+			Tree    interface{} `json:"filter_tree"`
+		}
+		require.NoError(t, json.Unmarshal(body, &out))
+		assert.True(t, out.IsSmart, "a tree collection IS smart without any rules array")
+		assert.NotNil(t, out.Tree, "the tree round-trips in the envelope")
+		h := string(body)
+		assert.Contains(t, h, "TreeColl New")
+		assert.Contains(t, h, "TreeColl New Two")
+		assert.NotContains(t, h, "TreeColl Old", "published 30d ago fails within_days")
+	})
+
+	t.Run("chain_follows_the_tree", func(t *testing.T) {
+		code, body := podcastAuthed(t, setup, regToken, "GET",
+			"/readers/"+uuid.UUID(aNew.ID.Bytes).String()+"?queue=collection:"+collID, "")
+		require.Equal(t, http.StatusOK, code)
+		html := string(body)
+		assert.Contains(t, html, esc(`"source":"collection"`))
+		assert.Contains(t, html, esc(`"episode_index":1`))
+		assert.Contains(t, html, esc(`"index_total":2`), "the briefing tree = the 2 fresh downloaded episodes")
+		assert.Contains(t, html, esc(`"next_url":"/readers/`+uuid.UUID(aNew2.ID.Bytes).String()+`?queue=collection:`+collID+`"`),
+			"chain hops stay on the tree's live membership")
+	})
+
+	t.Run("invalid_tree_is_400", func(t *testing.T) {
+		code, body := podcastAuthed(t, setup, regToken, "POST", "/api/collections",
+			`{"name":"Bad Tree `+marker+`","filter_tree":{"scope":"manga","mode":"all","children":[]}}`)
+		assert.Equal(t, http.StatusBadRequest, code,
+			"an invalid tree must be rejected at write: %s", string(body))
+	})
+
+	t.Run("tree_wins_over_legacy_rules", func(t *testing.T) {
+		// Update carries BOTH: a rules array that would match everything
+		// with the marker, and the strict briefing tree. The tree drives.
+		code, body := podcastAuthed(t, setup, regToken, "PUT", "/api/collections/"+collID,
+			`{"name":"test TreeColl `+marker+`","rule_match_mode":"any","auto_assign_rules":[{"field":"title","operator":"contains","value":"TreeColl"}],"filter_tree":`+string(briefing)+`}`)
+		require.Equal(t, http.StatusCreated, code, "%s", string(body))
+		code, body = podcastAuthed(t, setup, regToken, "GET", "/api/collections/"+collID, "")
+		require.Equal(t, http.StatusOK, code)
+		h := string(body)
+		assert.Contains(t, h, "TreeColl New")
+		assert.NotContains(t, h, "TreeColl Old",
+			"the tree's AND governs — legacy rules alone would have matched Old")
+	})
+
+	t.Run("edit_form_without_tree_keeps_it", func(t *testing.T) {
+		code, body := podcastAuthed(t, setup, regToken, "PUT", "/api/collections/"+collID,
+			`{"name":"test TreeColl `+marker+`","description":"kept the tree"}`)
+		require.Equal(t, http.StatusCreated, code, "%s", string(body))
+		code, body = podcastAuthed(t, setup, regToken, "GET", "/api/collections/"+collID, "")
+		require.Equal(t, http.StatusOK, code)
+		var out struct {
+			Tree interface{} `json:"filter_tree"`
+		}
+		require.NoError(t, json.Unmarshal(body, &out))
+		assert.NotNil(t, out.Tree, "an edit that sends no tree keeps the stored one")
+	})
+}
+
 // ---- download worker: state machine, idempotency, file layout ----
 
 func TestPodcastDownloadWorker(t *testing.T) {
diff --git a/cmd/server/tests/test_helpers_test.go b/cmd/server/tests/test_helpers_test.go
index 8f3a741a..aa3df61b 100644
--- a/cmd/server/tests/test_helpers_test.go
+++ b/cmd/server/tests/test_helpers_test.go
@@ -596,9 +596,12 @@ func setupTestServer(t *testing.T) *TestServerSetup {
 	worker := services.NewWorker(3, connManager)
 	services.WorkerInstance = worker
 	jobsHandler := handlers.NewJobsHandler(queries, worker)
-	collectionHandler := handlers.NewCollectionHandler(queries, libraryService, connManager)
+	// One composed-engine service for search AND the collection
+	// subsystem (item 3.2 — mirrors main.go).
+	collectionSearchService := services.NewSearchService(queries, scopedDB)
+	collectionHandler := handlers.NewCollectionHandler(queries, libraryService, connManager, collectionSearchService)
 	filtersHandler := handlers.NewFiltersHandler(queries)
-	dashboardService := services.NewDashboardService(queries)
+	dashboardService := services.NewDashboardService(queries, collectionSearchService)
 	dashboardHandler := handlers.NewDashboardHandler(queries)
 	statisticsService := services.NewStatisticsService(queries)
 	statsHandler := handlers.NewStatsHandler(statisticsService)
diff --git a/database/schema/schema.sql b/database/schema/schema.sql
index 1acf5334..77e174a1 100644
--- a/database/schema/schema.sql
+++ b/database/schema/schema.sql
@@ -1347,6 +1347,9 @@ CREATE TABLE IF NOT EXISTS collections (
     -- AND (the daily briefing needs feed∈{…} ∧ unplayed ∧ <7d).
     -- Applied only when rules exist; static collections ignore it.
     rule_match_mode TEXT NOT NULL DEFAULT 'any',
+    -- The unified filter tree (plan item 3.2): when present the qf
+    -- engine drives membership; see FilterTree. NULL = legacy rules.
+    filter_tree JSONB,
     view_settings JSONB,
     show_on_dashboard BOOLEAN DEFAULT false,
     query_type TEXT DEFAULT 'filter',
@@ -1367,12 +1370,18 @@ ALTER TABLE collections ADD COLUMN IF NOT EXISTS deleted_at TIMESTAMPTZ;
 -- DEFAULT covers existing rows.
 ALTER TABLE collections ADD COLUMN IF NOT EXISTS rule_match_mode TEXT NOT NULL DEFAULT 'any';
 
+-- Smart collections in the UNIFIED filter engine (plan item 3.2): the
+-- qf tree (same DSL as saved filters, See FilterTree). NULL = no tree
+-- (the legacy rules array governs until the collection is rewritten).
+-- Legacy rule_match_mode stays authoritative for rules-array
+-- collections; a tree's root mode owns its semantics.
+ALTER TABLE collections ADD COLUMN IF NOT EXISTS filter_tree JSONB;
+
 CREATE INDEX IF NOT EXISTS idx_collections_user_id ON collections(user_id);
 
 -- Index for dashboard queries
 CREATE INDEX IF NOT EXISTS idx_collections_dashboard ON collections(user_id, show_on_dashboard, priority)
     WHERE show_on_dashboard = true;
-
 -- Create user_dashboard_preferences table
 CREATE TABLE IF NOT EXISTS user_dashboard_preferences (
     id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
diff --git a/docs/contract_pins.md b/docs/contract_pins.md
index 1484f766..e20a3e70 100644
--- a/docs/contract_pins.md
+++ b/docs/contract_pins.md
@@ -481,3 +481,11 @@ Two shapes widen, both ADDITIVE — nothing removed, nothing renamed:
   episode-collections extras. Adapters that predate episode awareness
   emit their zero values (`false`/`""`), matching the
   viewer_percentage precedent (nil-representable, key always present).
+
+## 2026-10-30 — collections envelope gains filter_tree (additive widening, item 3.2)
+
+`GET /api/collections/:id` adds `filter_tree` to the envelope: the
+unified filter tree when the smart collection carries one (item 3.2 —
+tree-driven membership), `null` for legacy/static collections. The
+tree is the same qf DSL as saved filters (`{scope?, mode, children}`).
+Nothing removed, nothing renamed.
diff --git a/internal/database/models.go b/internal/database/models.go
index d429b670..d3eb690e 100644
--- a/internal/database/models.go
+++ b/internal/database/models.go
@@ -36,6 +36,7 @@ type Collections struct {
 	Icon               pgtype.Text        `db:"icon" json:"icon"`
 	AutoAssignRules    []byte             `db:"auto_assign_rules" json:"auto_assign_rules"`
 	RuleMatchMode      string             `db:"rule_match_mode" json:"rule_match_mode"`
+	FilterTree         []byte             `db:"filter_tree" json:"filter_tree"`
 	ViewSettings       []byte             `db:"view_settings" json:"view_settings"`
 	ShowOnDashboard    pgtype.Bool        `db:"show_on_dashboard" json:"show_on_dashboard"`
 	QueryType          pgtype.Text        `db:"query_type" json:"query_type"`
diff --git a/internal/database/queries.sql.go b/internal/database/queries.sql.go
index e6f02e03..8ff27e96 100644
--- a/internal/database/queries.sql.go
+++ b/internal/database/queries.sql.go
@@ -671,9 +671,9 @@ func (q *Queries) CreateAutoResolvedSyncConflict(ctx context.Context, arg Create
 
 const CreateCollection = `-- name: CreateCollection :one
 
-INSERT INTO collections (user_id, name, description, color, icon, auto_assign_rules, view_settings, show_on_dashboard)
-VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
-RETURNING id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at
+INSERT INTO collections (user_id, name, description, color, icon, auto_assign_rules, view_settings, show_on_dashboard, filter_tree)
+VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)
+RETURNING id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at
 `
 
 type CreateCollectionParams struct {
@@ -685,6 +685,7 @@ type CreateCollectionParams struct {
 	AutoAssignRules []byte      `db:"auto_assign_rules" json:"auto_assign_rules"`
 	ViewSettings    []byte      `db:"view_settings" json:"view_settings"`
 	ShowOnDashboard pgtype.Bool `db:"show_on_dashboard" json:"show_on_dashboard"`
+	FilterTree      []byte      `db:"filter_tree" json:"filter_tree"`
 }
 
 // COLLECTIONS QUERIES
@@ -699,6 +700,7 @@ func (q *Queries) CreateCollection(ctx context.Context, arg CreateCollectionPara
 		arg.AutoAssignRules,
 		arg.ViewSettings,
 		arg.ShowOnDashboard,
+		arg.FilterTree,
 	)
 	var i Collections
 	err := row.Scan(
@@ -710,6 +712,7 @@ func (q *Queries) CreateCollection(ctx context.Context, arg CreateCollectionPara
 		&i.Icon,
 		&i.AutoAssignRules,
 		&i.RuleMatchMode,
+		&i.FilterTree,
 		&i.ViewSettings,
 		&i.ShowOnDashboard,
 		&i.QueryType,
@@ -2253,7 +2256,7 @@ func (q *Queries) CreateSyncQueueItem(ctx context.Context, arg CreateSyncQueueIt
 const CreateSystemCollection = `-- name: CreateSystemCollection :one
 INSERT INTO collections (user_id, name, description, icon, color, show_on_dashboard, query_type, priority, is_system_collection, auto_assign_rules)
 VALUES ($1, $2, $3, $4, $5, $6, $7, $8, true, 'null'::jsonb)
-RETURNING id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at
+RETURNING id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at
 `
 
 type CreateSystemCollectionParams struct {
@@ -2288,6 +2291,7 @@ func (q *Queries) CreateSystemCollection(ctx context.Context, arg CreateSystemCo
 		&i.Icon,
 		&i.AutoAssignRules,
 		&i.RuleMatchMode,
+		&i.FilterTree,
 		&i.ViewSettings,
 		&i.ShowOnDashboard,
 		&i.QueryType,
@@ -4385,7 +4389,7 @@ func (q *Queries) GetBooksByTag(ctx context.Context, arg GetBooksByTagParams) ([
 }
 
 const GetCollection = `-- name: GetCollection :one
-SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections WHERE id = $1
+SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections WHERE id = $1
 `
 
 // Get collection
@@ -4401,6 +4405,7 @@ func (q *Queries) GetCollection(ctx context.Context, id pgtype.UUID) (Collection
 		&i.Icon,
 		&i.AutoAssignRules,
 		&i.RuleMatchMode,
+		&i.FilterTree,
 		&i.ViewSettings,
 		&i.ShowOnDashboard,
 		&i.QueryType,
@@ -4413,7 +4418,7 @@ func (q *Queries) GetCollection(ctx context.Context, id pgtype.UUID) (Collection
 }
 
 const GetCollectionByImportedSeries = `-- name: GetCollectionByImportedSeries :one
-SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections
+SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections
 WHERE user_id = $1
   AND view_settings->>'imported_from_series' = $2::text
   AND deleted_at IS NULL
@@ -4440,6 +4445,7 @@ func (q *Queries) GetCollectionByImportedSeries(ctx context.Context, arg GetColl
 		&i.Icon,
 		&i.AutoAssignRules,
 		&i.RuleMatchMode,
+		&i.FilterTree,
 		&i.ViewSettings,
 		&i.ShowOnDashboard,
 		&i.QueryType,
@@ -4452,7 +4458,7 @@ func (q *Queries) GetCollectionByImportedSeries(ctx context.Context, arg GetColl
 }
 
 const GetCollectionByUserAndName = `-- name: GetCollectionByUserAndName :one
-SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections
+SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections
 WHERE user_id = $1 AND name = $2 AND deleted_at IS NULL
 LIMIT 1
 `
@@ -4474,6 +4480,7 @@ func (q *Queries) GetCollectionByUserAndName(ctx context.Context, arg GetCollect
 		&i.Icon,
 		&i.AutoAssignRules,
 		&i.RuleMatchMode,
+		&i.FilterTree,
 		&i.ViewSettings,
 		&i.ShowOnDashboard,
 		&i.QueryType,
@@ -4966,7 +4973,7 @@ func (q *Queries) GetCollectionUpNext(ctx context.Context, arg GetCollectionUpNe
 
 const GetCollectionWithBookCount = `-- name: GetCollectionWithBookCount :one
 SELECT
-    c.id, c.user_id, c.name, c.description, c.color, c.icon, c.auto_assign_rules, c.rule_match_mode, c.view_settings, c.show_on_dashboard, c.query_type, c.priority, c.is_system_collection, c.created_at, c.deleted_at,
+    c.id, c.user_id, c.name, c.description, c.color, c.icon, c.auto_assign_rules, c.rule_match_mode, c.filter_tree, c.view_settings, c.show_on_dashboard, c.query_type, c.priority, c.is_system_collection, c.created_at, c.deleted_at,
     COUNT(ci.id) as book_count
 FROM collections c
 LEFT JOIN collection_items ci ON c.id = ci.collection_id
@@ -4983,6 +4990,7 @@ type GetCollectionWithBookCountRow struct {
 	Icon               pgtype.Text        `db:"icon" json:"icon"`
 	AutoAssignRules    []byte             `db:"auto_assign_rules" json:"auto_assign_rules"`
 	RuleMatchMode      string             `db:"rule_match_mode" json:"rule_match_mode"`
+	FilterTree         []byte             `db:"filter_tree" json:"filter_tree"`
 	ViewSettings       []byte             `db:"view_settings" json:"view_settings"`
 	ShowOnDashboard    pgtype.Bool        `db:"show_on_dashboard" json:"show_on_dashboard"`
 	QueryType          pgtype.Text        `db:"query_type" json:"query_type"`
@@ -5006,6 +5014,7 @@ func (q *Queries) GetCollectionWithBookCount(ctx context.Context, id pgtype.UUID
 		&i.Icon,
 		&i.AutoAssignRules,
 		&i.RuleMatchMode,
+		&i.FilterTree,
 		&i.ViewSettings,
 		&i.ShowOnDashboard,
 		&i.QueryType,
@@ -5019,7 +5028,7 @@ func (q *Queries) GetCollectionWithBookCount(ctx context.Context, id pgtype.UUID
 }
 
 const GetCollectionsByUser = `-- name: GetCollectionsByUser :many
-SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections WHERE user_id = $1 AND deleted_at IS NULL ORDER BY created_at DESC
+SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections WHERE user_id = $1 AND deleted_at IS NULL ORDER BY created_at DESC
 `
 
 // Get collections by user
@@ -5041,6 +5050,7 @@ func (q *Queries) GetCollectionsByUser(ctx context.Context, userID pgtype.UUID)
 			&i.Icon,
 			&i.AutoAssignRules,
 			&i.RuleMatchMode,
+			&i.FilterTree,
 			&i.ViewSettings,
 			&i.ShowOnDashboard,
 			&i.QueryType,
@@ -5060,7 +5070,7 @@ func (q *Queries) GetCollectionsByUser(ctx context.Context, userID pgtype.UUID)
 }
 
 const GetCollectionsForBook = `-- name: GetCollectionsForBook :many
-SELECT c.id, c.user_id, c.name, c.description, c.color, c.icon, c.auto_assign_rules, c.rule_match_mode, c.view_settings, c.show_on_dashboard, c.query_type, c.priority, c.is_system_collection, c.created_at, c.deleted_at
+SELECT c.id, c.user_id, c.name, c.description, c.color, c.icon, c.auto_assign_rules, c.rule_match_mode, c.filter_tree, c.view_settings, c.show_on_dashboard, c.query_type, c.priority, c.is_system_collection, c.created_at, c.deleted_at
 FROM collections c
 JOIN collection_items ci ON c.id = ci.collection_id
 WHERE ci.media_item_id = $1
@@ -5086,6 +5096,7 @@ func (q *Queries) GetCollectionsForBook(ctx context.Context, mediaItemID pgtype.
 			&i.Icon,
 			&i.AutoAssignRules,
 			&i.RuleMatchMode,
+			&i.FilterTree,
 			&i.ViewSettings,
 			&i.ShowOnDashboard,
 			&i.QueryType,
@@ -10790,7 +10801,7 @@ func (q *Queries) GetSyncQueueStats(ctx context.Context, deviceID pgtype.UUID) (
 
 const GetSystemCollectionByQueryType = `-- name: GetSystemCollectionByQueryType :one
 
-SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections
+SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections
 WHERE user_id = $1
   AND query_type = $2
   AND is_system_collection = true
@@ -10818,6 +10829,7 @@ func (q *Queries) GetSystemCollectionByQueryType(ctx context.Context, arg GetSys
 		&i.Icon,
 		&i.AutoAssignRules,
 		&i.RuleMatchMode,
+		&i.FilterTree,
 		&i.ViewSettings,
 		&i.ShowOnDashboard,
 		&i.QueryType,
@@ -10830,7 +10842,7 @@ func (q *Queries) GetSystemCollectionByQueryType(ctx context.Context, arg GetSys
 }
 
 const GetSystemCollectionsForDashboard = `-- name: GetSystemCollectionsForDashboard :many
-SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections
+SELECT id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at FROM collections
 WHERE user_id = $1
   AND is_system_collection = true
   AND show_on_dashboard = true
@@ -10857,6 +10869,7 @@ func (q *Queries) GetSystemCollectionsForDashboard(ctx context.Context, userID p
 			&i.Icon,
 			&i.AutoAssignRules,
 			&i.RuleMatchMode,
+			&i.FilterTree,
 			&i.ViewSettings,
 			&i.ShowOnDashboard,
 			&i.QueryType,
@@ -11562,7 +11575,7 @@ func (q *Queries) GetUserByUsername(ctx context.Context, username string) (GetUs
 }
 
 const GetUserCollectionsForDashboard = `-- name: GetUserCollectionsForDashboard :many
-SELECT c.id, c.user_id, c.name, c.description, c.color, c.icon, c.auto_assign_rules, c.rule_match_mode, c.view_settings, c.show_on_dashboard, c.query_type, c.priority, c.is_system_collection, c.created_at, c.deleted_at FROM collections c
+SELECT c.id, c.user_id, c.name, c.description, c.color, c.icon, c.auto_assign_rules, c.rule_match_mode, c.filter_tree, c.view_settings, c.show_on_dashboard, c.query_type, c.priority, c.is_system_collection, c.created_at, c.deleted_at FROM collections c
 WHERE c.user_id = $1
   AND c.is_system_collection = false
   AND c.deleted_at IS NULL
@@ -11591,6 +11604,7 @@ func (q *Queries) GetUserCollectionsForDashboard(ctx context.Context, userID pgt
 			&i.Icon,
 			&i.AutoAssignRules,
 			&i.RuleMatchMode,
+			&i.FilterTree,
 			&i.ViewSettings,
 			&i.ShowOnDashboard,
 			&i.QueryType,
@@ -16470,7 +16484,7 @@ SET name = $2,
     show_on_dashboard = true,
     deleted_at = NULL
 WHERE id = $1
-RETURNING id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at
+RETURNING id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at
 `
 
 type RestoreSystemCollectionRowParams struct {
@@ -16503,6 +16517,7 @@ func (q *Queries) RestoreSystemCollectionRow(ctx context.Context, arg RestoreSys
 		&i.Icon,
 		&i.AutoAssignRules,
 		&i.RuleMatchMode,
+		&i.FilterTree,
 		&i.ViewSettings,
 		&i.ShowOnDashboard,
 		&i.QueryType,
@@ -18217,9 +18232,10 @@ SET
     icon = $5,
     auto_assign_rules = $6,
     view_settings = $7,
-    rule_match_mode = $8
+    rule_match_mode = $8,
+    filter_tree = $9
 WHERE id = $1
-RETURNING id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at
+RETURNING id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at
 `
 
 type UpdateCollectionParams struct {
@@ -18231,6 +18247,7 @@ type UpdateCollectionParams struct {
 	AutoAssignRules []byte      `db:"auto_assign_rules" json:"auto_assign_rules"`
 	ViewSettings    []byte      `db:"view_settings" json:"view_settings"`
 	RuleMatchMode   string      `db:"rule_match_mode" json:"rule_match_mode"`
+	FilterTree      []byte      `db:"filter_tree" json:"filter_tree"`
 }
 
 // Update collection
@@ -18244,6 +18261,7 @@ func (q *Queries) UpdateCollection(ctx context.Context, arg UpdateCollectionPara
 		arg.AutoAssignRules,
 		arg.ViewSettings,
 		arg.RuleMatchMode,
+		arg.FilterTree,
 	)
 	var i Collections
 	err := row.Scan(
@@ -18255,6 +18273,7 @@ func (q *Queries) UpdateCollection(ctx context.Context, arg UpdateCollectionPara
 		&i.Icon,
 		&i.AutoAssignRules,
 		&i.RuleMatchMode,
+		&i.FilterTree,
 		&i.ViewSettings,
 		&i.ShowOnDashboard,
 		&i.QueryType,
@@ -18283,7 +18302,7 @@ func (q *Queries) UpdateCollectionMatchMode(ctx context.Context, arg UpdateColle
 }
 
 const UpdateCollectionRulesJSON = `-- name: UpdateCollectionRulesJSON :one
-UPDATE collections SET auto_assign_rules = $2 WHERE id = $1 RETURNING id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at
+UPDATE collections SET auto_assign_rules = $2 WHERE id = $1 RETURNING id, user_id, name, description, color, icon, auto_assign_rules, rule_match_mode, filter_tree, view_settings, show_on_dashboard, query_type, priority, is_system_collection, created_at, deleted_at
 `
 
 type UpdateCollectionRulesJSONParams struct {
@@ -18305,6 +18324,7 @@ func (q *Queries) UpdateCollectionRulesJSON(ctx context.Context, arg UpdateColle
 		&i.Icon,
 		&i.AutoAssignRules,
 		&i.RuleMatchMode,
+		&i.FilterTree,
 		&i.ViewSettings,
 		&i.ShowOnDashboard,
 		&i.QueryType,
diff --git a/internal/database/queries/queries.sql b/internal/database/queries/queries.sql
index a0b163b8..687275d5 100644
--- a/internal/database/queries/queries.sql
+++ b/internal/database/queries/queries.sql
@@ -3489,8 +3489,8 @@ DELETE FROM device_file_aliases WHERE id = $1;
 
 -- Create collection
 -- name: CreateCollection :one
-INSERT INTO collections (user_id, name, description, color, icon, auto_assign_rules, view_settings, show_on_dashboard)
-VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
+INSERT INTO collections (user_id, name, description, color, icon, auto_assign_rules, view_settings, show_on_dashboard, filter_tree)
+VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)
 RETURNING *;
 
 -- A2c §2.4: provenance + playlist flags on an existing collection without
@@ -3535,7 +3535,8 @@ SET
     icon = $5,
     auto_assign_rules = $6,
     view_settings = $7,
-    rule_match_mode = $8
+    rule_match_mode = $8,
+    filter_tree = $9
 WHERE id = $1
 RETURNING *;
 
diff --git a/internal/handlers/collections.go b/internal/handlers/collections.go
index 87095634..408cfcd1 100644
--- a/internal/handlers/collections.go
+++ b/internal/handlers/collections.go
@@ -26,10 +26,10 @@ type CollectionHandler struct {
 	connManager       *wsync.ConnectionManager
 }
 
-func NewCollectionHandler(db *database.Queries, libraryService *services.LibraryService, connManager *wsync.ConnectionManager) *CollectionHandler {
+func NewCollectionHandler(db *database.Queries, libraryService *services.LibraryService, connManager *wsync.ConnectionManager, search ...*services.SearchService) *CollectionHandler {
 	return &CollectionHandler{
 		db:                db,
-		collectionService: services.NewCollectionService(db),
+		collectionService: services.NewCollectionService(db, search...),
 		libraryService:    libraryService,
 		connManager:       connManager,
 	}
@@ -43,6 +43,47 @@ type CreateCollectionRequest struct {
 	CollectionType  string                 `form:"collection_type" json:"collection_type"` // "static" (default) or "smart" (rule-based)
 	AutoAssignRules []services.Rule        `form:"auto_assign_rules" json:"auto_assign_rules"`
 	ViewSettings    map[string]interface{} `form:"view_settings" json:"view_settings"`
+	// The unified filter tree (item 3.2): when present the collection's
+	// smart membership runs through the qf engine. INVALID trees are a
+	// 400 (ParseFilterTree at the handler); a tree supersedes
+	// auto_assign_rules. Persisted as-is (any). RawMessage for
+	// round-trip safety.
+	FilterTree any `form:"filter_tree" json:"filter_tree"`
+}
+
+// treeFilterJSON returns the request's filter tree as JSON storage
+// bytes (nil when none): object payloads marshal; strings (a legacy
+// double-encoded client, the custom-section builder's known bug class)
+// are written verbatim after object-attempt.
+func treeFilterJSON(payload any) ([]byte, error) {
+	switch v := payload.(type) {
+	case nil:
+		return nil, nil
+	case map[string]interface{}:
+		b, err := json.Marshal(v)
+		if err != nil {
+			return nil, err
+		}
+		return b, nil
+	case string:
+		return []byte(v), nil
+	default:
+		return nil, fmt.Errorf("filter_tree must be an object")
+	}
+}
+
+// parseRequestFilterTree validates the request's tree against the
+// engine grammar (ParseFilterTree) so an invalid tree is a 400, never
+// a stored 500 at render time.
+func parseRequestFilterTree(payload any) ([]byte, error) {
+	b, err := treeFilterJSON(payload)
+	if err != nil || b == nil {
+		return b, err
+	}
+	if _, err := services.ParseFilterTree(string(b)); err != nil {
+		return nil, fmt.Errorf("invalid filter_tree: %w", err)
+	}
+	return b, nil
 }
 
 type UpdateCollectionRequest struct {
@@ -50,6 +91,11 @@ type UpdateCollectionRequest struct {
 	// Smart-collection match semantics (item 2.4): "any" (OR) | "all"
 	// (AND). Empty/invalid keeps the stored value.
 	RuleMatchMode   string                 `form:"rule_match_mode" json:"rule_match_mode"`
+	// The unified filter tree (item 3.2): when present the collection's
+	// smart membership runs through the qf engine. INVALID trees are a
+	// 400 (ParseFilterTree at the handler); a tree supersedes
+	// auto_assign_rules.
+	FilterTree      any                    `form:"filter_tree" json:"filter_tree"`
 	Description     string                 `form:"description" json:"description"`
 	Color           string                 `form:"color" json:"color"`
 	Icon            string                 `form:"icon" json:"icon"`
@@ -141,6 +187,10 @@ func (h *CollectionHandler) CreateCollection(c *echo.Context) error {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": err.Error()})
 	}
 
+	treeJSON, treeErr := parseRequestFilterTree(req.FilterTree)
+	if treeErr != nil {
+		return c.JSON(http.StatusBadRequest, map[string]string{"error": treeErr.Error()})
+	}
 	collection, err := h.collectionService.CreateCollection(
 		c.Request().Context(),
 		userUUID,
@@ -150,6 +200,7 @@ func (h *CollectionHandler) CreateCollection(c *echo.Context) error {
 		req.Icon,
 		req.AutoAssignRules,
 		req.ViewSettings,
+		treeJSON,
 	)
 	if err != nil {
 		if errors.Is(err, services.ErrCollectionNameTaken) {
@@ -200,7 +251,7 @@ func (h *CollectionHandler) GetCollections(c *echo.Context) error {
 
 	response := make([]CollectionSummary, 0, len(collections))
 	for _, col := range collections {
-		isSmart := h.collectionService.IsSmartCollection(col.AutoAssignRules)
+		isSmart := services.IsCollectionSmart(col)
 		if !includeAuto && isSmart {
 			// Legacy default for API clients (the Android app pre-dates
 			// smart collections): rule-driven collections stay opt-in so
@@ -216,10 +267,9 @@ func (h *CollectionHandler) GetCollections(c *echo.Context) error {
 			}
 		}
 		if isSmart {
-			rules := h.collectionService.ParseRules(col.AutoAssignRules)
 			visibleIDs, visErr := h.userVisibleLibraryIDs(c)
 			if visErr == nil {
-				matches, evalErr := h.collectionService.EvaluateSmartCollection(c.Request().Context(), rules, services.SmartEvalOptions{
+				matches, evalErr := h.collectionService.EvaluateSmartMembership(c.Request().Context(), col, services.SmartEvalOptions{
 					LibraryID:    libUUID,
 					VisibleIDs:   visibleIDs,
 					MatchMode:    col.RuleMatchMode,
@@ -291,15 +341,14 @@ func (h *CollectionHandler) GetCollection(c *echo.Context) error {
 		libUUID = pgtype.UUID{Bytes: parsed, Valid: true}
 	}
 
-	isSmart := h.collectionService.IsSmartCollection(collection.AutoAssignRules)
+	isSmart := services.IsCollectionSmart(collection)
 	libTypes := LibraryTypeMap(c.Request().Context(), h.db)
 	if isSmart {
-		rules := h.collectionService.ParseRules(collection.AutoAssignRules)
 		visibleIDs, err := h.userVisibleLibraryIDs(c)
 		if err != nil {
 			return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
 		}
-		matches, evalErr := h.collectionService.EvaluateSmartCollection(c.Request().Context(), rules, services.SmartEvalOptions{
+		matches, evalErr := h.collectionService.EvaluateSmartMembership(c.Request().Context(), collection, services.SmartEvalOptions{
 			LibraryID:    libUUID,
 			VisibleIDs:   visibleIDs,
 			MatchMode:    collection.RuleMatchMode,
@@ -419,6 +468,7 @@ func (h *CollectionHandler) GetCollection(c *echo.Context) error {
 		"auto_assign_rules": json.RawMessage(collection.AutoAssignRules),
 		"view_settings":     viewSettings,
 		"rule_match_mode":   collection.RuleMatchMode,
+		"filter_tree":       treeEnvelope(collection.FilterTree),
 		"books":             bookList,
 		"book_count":        len(bookList),
 		"is_smart":          isSmart,
@@ -458,6 +508,10 @@ func (h *CollectionHandler) UpdateCollection(c *echo.Context) error {
 		req.ViewSettings["show_up_next"] = *v
 	}
 
+	treeJSON, treeErr := parseRequestFilterTree(req.FilterTree)
+	if treeErr != nil {
+		return c.JSON(http.StatusBadRequest, map[string]string{"error": treeErr.Error()})
+	}
 	collection, err := h.collectionService.UpdateCollection(
 		c.Request().Context(),
 		collectionID,
@@ -468,6 +522,7 @@ func (h *CollectionHandler) UpdateCollection(c *echo.Context) error {
 		req.AutoAssignRules,
 		req.ViewSettings,
 		req.RuleMatchMode,
+		treeJSON,
 	)
 	if err != nil {
 		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
@@ -860,7 +915,7 @@ func (h *CollectionHandler) rejectSmartMutation(c *echo.Context, collectionID uu
 	if err != nil {
 		return echo.NewHTTPError(http.StatusNotFound, "collection not found")
 	}
-	if h.collectionService.IsSmartCollection(collection.AutoAssignRules) {
+	if services.IsCollectionSmart(collection) {
 		return echo.NewHTTPError(http.StatusBadRequest, "smart collections are rule-based — membership is managed by the collection's rules, not by hand")
 	}
 	return nil
@@ -916,7 +971,7 @@ func (h *CollectionHandler) AddRule(c *echo.Context) error {
 	return c.JSON(http.StatusCreated, map[string]interface{}{
 		"collection_id": uuid.UUID(updated.ID.Bytes).String(),
 		"rule":          rule,
-		"is_smart":      h.collectionService.IsSmartCollection(updated.AutoAssignRules),
+		"is_smart":      services.IsCollectionSmart(updated),
 	})
 }
 
@@ -952,7 +1007,7 @@ func (h *CollectionHandler) UpdateRule(c *echo.Context) error {
 
 	return c.JSON(http.StatusOK, map[string]interface{}{
 		"collection_id": uuid.UUID(updated.ID.Bytes).String(),
-		"is_smart":      h.collectionService.IsSmartCollection(updated.AutoAssignRules),
+		"is_smart":      services.IsCollectionSmart(updated),
 	})
 }
 
@@ -977,7 +1032,7 @@ func (h *CollectionHandler) RemoveRule(c *echo.Context) error {
 
 	return c.JSON(http.StatusOK, map[string]interface{}{
 		"collection_id": uuid.UUID(updated.ID.Bytes).String(),
-		"is_smart":      h.collectionService.IsSmartCollection(updated.AutoAssignRules),
+		"is_smart":      services.IsCollectionSmart(updated),
 	})
 }
 
@@ -988,6 +1043,19 @@ type TestRulesRequest struct {
 	MatchMode string `json:"match_mode"`
 }
 
+// treeEnvelope renders the stored filter tree for the envelope: nil
+// (legacy/static collections) serializes as null, trees as the object.
+func treeEnvelope(t []byte) any {
+	if len(t) == 0 {
+		return nil
+	}
+	var v interface{}
+	if json.Unmarshal(t, &v) == nil {
+		return v
+	}
+	return nil
+}
+
 type BookMatch struct {
 	MediaItemID    string `json:"media_item_id"`
 	Title          string `json:"title"`
diff --git a/internal/router/frontend.go b/internal/router/frontend.go
index be7199cc..dcaec798 100644
--- a/internal/router/frontend.go
+++ b/internal/router/frontend.go
@@ -562,11 +562,11 @@ func registerFrontendRoutes(cfg *Config) {
 		colData := make([]templates.CollectionData, len(collections))
 		colService := cfg.CollectionHandler.CollectionService()
 		for i, col := range collections {
-			isSmart := colService.IsSmartCollection(col.AutoAssignRules)
+			isSmart := services.IsCollectionSmart(col)
 			bookCount := 0
 			if isSmart {
-				matches, evalErr := colService.EvaluateSmartCollection(c.Request().Context(),
-					colService.ParseRules(col.AutoAssignRules), services.SmartEvalOptions{
+				matches, evalErr := colService.EvaluateSmartMembership(c.Request().Context(),
+					col, services.SmartEvalOptions{
 						LibraryID:    libScope,
 						VisibleIDs:   visibleIDs,
 						MatchMode:    col.RuleMatchMode,
diff --git a/internal/router/helpers.go b/internal/router/helpers.go
index 0fe2fa1f..f0a8de05 100644
--- a/internal/router/helpers.go
+++ b/internal/router/helpers.go
@@ -289,7 +289,7 @@ func collectionDataFromRow(collection database.Collections, collectionID string,
 // libUUID/libScope/isAll/scoped per their own resolution rules.
 func (cfg *Config) collectionBooksForScope(c *echo.Context, userUUID uuid.UUID, collUUID pgtype.UUID, collection database.Collections, collectionID string, libUUID pgtype.UUID, libScope pgtype.UUID, scoped bool, visibleIDs []pgtype.UUID) (books []handlers.BookInfo, isSmart bool, errCode string) {
 	colService := cfg.CollectionHandler.CollectionService()
-	isSmart = colService.IsSmartCollection(collection.AutoAssignRules)
+	isSmart = services.IsCollectionSmart(collection)
 	libTypes := handlers.LibraryTypeMap(c.Request().Context(), cfg.Queries)
 
 	if isSmart {
@@ -297,8 +297,8 @@ func (cfg *Config) collectionBooksForScope(c *echo.Context, userUUID uuid.UUID,
 		// visible libraries, live items only, rules applied under the
 		// collection's match mode (item 2.4: any|all), with the
 		// viewer's progress feeding played/unplayed rules.
-		matches, evalErr := colService.EvaluateSmartCollection(c.Request().Context(),
-			colService.ParseRules(collection.AutoAssignRules), services.SmartEvalOptions{
+		matches, evalErr := colService.EvaluateSmartMembership(c.Request().Context(),
+			collection, services.SmartEvalOptions{
 				LibraryID:    libScope,
 				VisibleIDs:   visibleIDs,
 				MatchMode:    collection.RuleMatchMode,
diff --git a/internal/router/reader.go b/internal/router/reader.go
index 51c05cf3..b2d1524e 100644
--- a/internal/router/reader.go
+++ b/internal/router/reader.go
@@ -286,7 +286,7 @@ func buildCollectionSequenceContext(c *echo.Context, cfg *Config, item *database
 	// order, never written back) — evaluate the rules for THIS viewer
 	// and chain the downloaded episode matches in native feed order
 	// (R3: every listening order routes through OrderEpisodes).
-	if len(coll.AutoAssignRules) > 0 {
+	if services.IsCollectionSmart(coll) {
 		return buildSmartCollectionSequenceContext(c, cfg, item, userID, coll)
 	}
 	// Downloaded episodes in collection order (SQL orders; RLS scopes
@@ -339,7 +339,7 @@ func buildSmartCollectionSequenceContext(c *echo.Context, cfg *Config, item *dat
 	if err != nil {
 		visibleIDs = nil
 	}
-	matches, err := colService.EvaluateSmartCollection(ctx, colService.ParseRules(coll.AutoAssignRules), services.SmartEvalOptions{
+	matches, err := colService.EvaluateSmartMembership(ctx, coll, services.SmartEvalOptions{
 		VisibleIDs:   visibleIDs,
 		MatchMode:    coll.RuleMatchMode,
 		ViewerUserID: userID,
diff --git a/internal/services/collection_service.go b/internal/services/collection_service.go
index b6eeadaf..5e0bdd73 100644
--- a/internal/services/collection_service.go
+++ b/internal/services/collection_service.go
@@ -78,17 +78,28 @@ type RuleEvaluation struct {
 // CollectionService handles collection management
 type CollectionService struct {
 	db *database.Queries
+	// search powers the unified-engine path (item 3.2): tree-driven
+	// smart collections evaluate via ComposedLiveMedia. Optional —
+	// nil disables tree evaluation (legacy-only services, which keeps
+	// every existing constructor call site valid).
+	search *SearchService
 }
 
-// NewCollectionService creates a new collection service
-func NewCollectionService(db *database.Queries) *CollectionService {
-	return &CollectionService{
-		db: db,
+// NewCollectionService creates a new collection service. search is
+// optional (variadic for constructor compatibility) — required for
+// TREE-driven smart collections (item 3.2), ignored otherwise.
+func NewCollectionService(db *database.Queries, search ...*SearchService) *CollectionService {
+	svc := &CollectionService{db: db}
+	if len(search) > 0 {
+		svc.search = search[0]
 	}
+	return svc
 }
 
-// CreateCollection creates a new collection
-func (s *CollectionService) CreateCollection(ctx context.Context, userID uuid.UUID, name, description, color, icon string, autoAssignRules []Rule, viewSettings map[string]any) (database.Collections, error) {
+// CreateCollection creates a new collection. filterTree (item 3.2)
+// replaces autoAssignRules as the smart engine's source when present —
+// both may coexist on the row (tree wins at evaluation).
+func (s *CollectionService) CreateCollection(ctx context.Context, userID uuid.UUID, name, description, color, icon string, autoAssignRules []Rule, viewSettings map[string]any, filterTree []byte) (database.Collections, error) {
 	// Convert rules to JSONB ([]byte)
 	var rulesJSON []byte
 	if len(autoAssignRules) > 0 {
@@ -117,6 +128,7 @@ func (s *CollectionService) CreateCollection(ctx context.Context, userID uuid.UU
 		Icon:            pgtype.Text{String: icon, Valid: icon != ""},
 		AutoAssignRules: rulesJSON,
 		ViewSettings:    settingsJSON,
+		FilterTree:      filterTree,
 	})
 
 	if err != nil {
@@ -155,14 +167,18 @@ func (s *CollectionService) GetUserCollections(ctx context.Context, userID uuid.
 // UpdateCollection updates a collection
 // UpdateCollection rewrites the collection row. ruleMatchMode empty or
 // invalid = keep the stored value (the edit form only sends the toggles
-// it renders — plan item 2.4).
-func (s *CollectionService) UpdateCollection(ctx context.Context, collectionID uuid.UUID, name, description, color, icon string, autoAssignRules []Rule, viewSettings map[string]any, ruleMatchMode string) (database.Collections, error) {
+// it renders — plan item 2.4). filterTree semantics: nil = leave the
+// stored tree untouched.
+func (s *CollectionService) UpdateCollection(ctx context.Context, collectionID uuid.UUID, name, description, color, icon string, autoAssignRules []Rule, viewSettings map[string]any, ruleMatchMode string, filterTree []byte) (database.Collections, error) {
 	// A2c §3.3: the edit form carries only the toggles it renders — merge
 	// them OVER the stored view_settings so provenance keys
 	// (imported_from_series) and anything else on the row survive.
 	existingMode := RuleMatchAny
 	if existing, err := s.db.GetCollection(ctx, pgtype.UUID{Bytes: collectionID, Valid: true}); err == nil {
 		existingMode = existing.RuleMatchMode
+		if filterTree == nil {
+			filterTree = existing.FilterTree // nil = untouched (forms don't send trees)
+		}
 		if len(viewSettings) > 0 && len(existing.ViewSettings) > 0 {
 			var stored map[string]any
 			if json.Unmarshal(existing.ViewSettings, &stored) == nil {
@@ -207,6 +223,7 @@ func (s *CollectionService) UpdateCollection(ctx context.Context, collectionID u
 		AutoAssignRules: rulesJSON,
 		ViewSettings:    settingsJSON,
 		RuleMatchMode:   ruleMatchMode,
+		FilterTree:      filterTree,
 	})
 
 	if err != nil {
@@ -461,6 +478,142 @@ type SmartEvalOptions struct {
 	ViewerUserID pgtype.UUID
 }
 
+// IsCollectionSmart is the ONE smart detection: a collection is smart
+// when it carries the unified filter tree (item 3.2) or a legacy rules
+// array (item 2's shape). Every surface routes through this — rules
+// presence alone misses tree collections.
+func IsCollectionSmart(coll database.Collections) bool {
+	if len(coll.FilterTree) > 0 {
+		return true
+	}
+	var rules []Rule
+	if err := json.Unmarshal(coll.AutoAssignRules, &rules); err != nil {
+		return false
+	}
+	return len(rules) > 0
+}
+
+
+
+// EvaluateSmartMembership is THE single smart evaluator (item 3.2):
+// tree-bearing collections evaluate through the unified filter engine;
+// legacy rule arrays keep per-item evaluation until rewritten. One
+// call site surface, two storage epochs.
+func (s *CollectionService) EvaluateSmartMembership(ctx context.Context, coll database.Collections, opts SmartEvalOptions) ([]database.MediaItems, error) {
+	if len(coll.FilterTree) > 0 {
+		return s.evaluateTreeMembership(ctx, coll, opts)
+	}
+	return s.EvaluateSmartCollection(ctx, s.ParseRules(coll.AutoAssignRules), opts)
+}
+
+// RulesToFilterTree converts a legacy rules array + its match mode
+// into a qf tree so a collection upgrades to the unified engine at its
+// first edit (item 3.2): zero-rewrite back-compat at read, one-way
+// upgrade at write. Episode rules map mechanically (feed→in-list,
+// played/downloaded→booleans, published_within→published_date
+// within_days); legacy operators without an engine equivalent
+// (starts_with/ends_with) fall back to contains — documented, and the
+// operator labels stay in the rules docs.
+func RulesToFilterTree(rules []Rule, matchMode string) (*FilterTree, error) {
+	children := make([]FilterChild, 0, len(rules))
+	scope := ""
+	for _, r := range rules {
+		child, err := ruleToFilterChild(r)
+		if err != nil {
+			return nil, err
+		}
+		if episodeOnlyFields[r.Field] {
+			scope = ScopeEpisodes
+		}
+		children = append(children, child)
+	}
+	if len(children) == 0 {
+		return nil, fmt.Errorf("no rules to convert")
+	}
+	mode := RuleMatchAny
+	if matchMode == RuleMatchAll {
+		mode = RuleMatchAll
+	}
+	return &FilterTree{Scope: scope, Mode: mode, Children: children}, nil
+}
+
+func ruleToFilterChild(r Rule) (FilterChild, error) {
+	child := FilterChild{Field: r.Field}
+	switch r.Field {
+	case "feed":
+		// The rules format stores comma-separated feed IDs in one value.
+		child.Op = OpIn
+		child.Values = splitRuleValues(r.Value)
+		return child, nil
+	case "downloaded":
+		child.Op = isTrueFalse(r.Value == "true")
+		return child, nil
+	case "played":
+		child.Op = isTrueFalse(r.Value == "true")
+		return child, nil
+	case "published_within":
+		child.Field = "published_date"
+		child.Op = OpWithinDays
+		child.Values = []string{r.Value}
+		return child, nil
+	}
+	// Registry fields: legacy operators → engine operators.
+	switch r.Operator {
+	case "equals":
+		child.Op = OpIs
+	case "not_equals":
+		child.Op = OpIsNot
+	case "contains":
+		child.Op = OpContains
+	case "not_contains":
+		child.Op = OpNotContains
+	case "greater_than":
+		child.Op = OpAtLeast
+	case "less_than":
+		child.Op = OpAtMost
+	case "in":
+		child.Op = OpIn
+		child.Values = splitRuleValues(r.Value)
+	case "starts_with", "ends_with":
+		// No engine equivalent — contains is the honest nearest.
+		child.Op = OpContains
+	default:
+		return FilterChild{}, fmt.Errorf("legacy rule operator %q has no filter-engine equivalent", r.Operator)
+	}
+	child.Values = []string{r.Value}
+	return child, nil
+}
+
+func isTrueFalse(b bool) string {
+	if b {
+		return OpIsTrue
+	}
+	return OpIsFalse
+}
+
+func splitRuleValues(v string) []string {
+	parts := strings.Split(v, ",")
+	out := make([]string, 0, len(parts))
+	for _, p := range parts {
+		p = strings.TrimSpace(p)
+		if p != "" {
+			out = append(out, p)
+		}
+	}
+	return out
+}
+
+func (s *CollectionService) evaluateTreeMembership(ctx context.Context, coll database.Collections, opts SmartEvalOptions) ([]database.MediaItems, error) {
+	tree, err := ParseFilterTree(string(coll.FilterTree))
+	if err != nil {
+		return nil, fmt.Errorf("collection %s has an invalid filter tree: %v", coll.ID, err)
+	}
+	if s.search == nil {
+		return nil, errors.New("tree collections require the search service (constructor wiring)")
+	}
+	return s.search.ComposedLiveMedia(ctx, opts.ViewerUserID, opts.LibraryID, opts.VisibleIDs, tree)
+}
+
 // EvaluateSmartCollection resolves a smart collection's membership LIVE:
 // every visible live book matched by at least one enabled rule is in.
 // No stored links are consulted — "truly dynamic," always current.
diff --git a/internal/services/collection_service_test.go b/internal/services/collection_service_test.go
index 22cff8b1..d03842d1 100644
--- a/internal/services/collection_service_test.go
+++ b/internal/services/collection_service_test.go
@@ -2,9 +2,12 @@ package services
 
 import (
 	"bookhoard/internal/database"
+	"encoding/json"
 	"testing"
 
 	"github.com/jackc/pgx/v5/pgtype"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestEvaluateRules_Equality(t *testing.T) {
@@ -276,3 +279,45 @@ func TestEvaluateRules_PriorityBoost(t *testing.T) {
 		t.Errorf("expected higher priority rule to be first, got %s", evaluations[0].RuleID)
 	}
 }
+
+func TestRulesToFilterTree(t *testing.T) {
+	t.Run("episode_rules_map_mechanically", func(t *testing.T) {
+		rules := []Rule{
+			{ID: "1", Field: "feed", Operator: "in", Value: "feed-a, feed-b"},
+			{ID: "2", Field: "played", Operator: "equals", Value: "false"},
+			{ID: "3", Field: "downloaded", Operator: "equals", Value: "true"},
+			{ID: "4", Field: "published_within", Operator: "greater_than", Value: "7"},
+		}
+		tree, err := RulesToFilterTree(rules, RuleMatchAll)
+		require.NoError(t, err)
+		assert.Equal(t, RuleMatchAll, tree.Mode, "the collection's match mode becomes the tree mode")
+		assert.Equal(t, ScopeEpisodes, tree.Scope, "episode rules force the episodes scope")
+		require.Len(t, tree.Children, 4)
+		assert.Equal(t, FilterChild{Field: "feed", Op: OpIn, Values: []string{"feed-a", "feed-b"}}, tree.Children[0])
+		assert.Equal(t, FilterChild{Field: "played", Op: OpIsFalse}, tree.Children[1])
+		assert.Equal(t, FilterChild{Field: "downloaded", Op: OpIsTrue}, tree.Children[2])
+		assert.Equal(t, FilterChild{Field: "published_date", Op: OpWithinDays, Values: []string{"7"}}, tree.Children[3])
+		// The converted tree parses under the strict engine.
+		b, _ := json.Marshal(tree)
+		_, err = ParseFilterTree(string(b))
+		require.NoError(t, err, "converted tree must satisfy the engine grammar")
+	})
+
+	t.Run("book_rules_map_and_stay_books_scope", func(t *testing.T) {
+		rules := []Rule{
+			{Field: "genre", Operator: "equals", Value: "fantasy"},
+			{Field: "author", Operator: "contains", Value: "Voss"},
+			{Field: "copyright_year", Operator: "greater_than", Value: "1990"},
+			{Field: "tags", Operator: "starts_with", Value: "dyst"},
+		}
+		tree, err := RulesToFilterTree(rules, RuleMatchAny)
+		require.NoError(t, err)
+		assert.Equal(t, "", tree.Scope, "no episode rules → the books scope (legacy default)")
+		assert.Equal(t, RuleMatchAny, tree.Mode)
+		assert.Equal(t, FilterChild{Field: "genre", Op: OpIs, Values: []string{"fantasy"}}, tree.Children[0])
+		assert.Equal(t, FilterChild{Field: "copyright_year", Op: OpAtLeast, Values: []string{"1990"}}, tree.Children[2])
+		// Documented fallback: rules ops without an engine equivalent
+		// (starts_with/ends_with) become contains.
+		assert.Equal(t, OpContains, tree.Children[3].Op)
+	})
+}
diff --git a/internal/services/dashboard_service.go b/internal/services/dashboard_service.go
index 9c0dc4b7..d499f63f 100644
--- a/internal/services/dashboard_service.go
+++ b/internal/services/dashboard_service.go
@@ -17,10 +17,10 @@ type DashboardService struct {
 	collectionService *CollectionService
 }
 
-func NewDashboardService(db *database.Queries) *DashboardService {
+func NewDashboardService(db *database.Queries, search ...*SearchService) *DashboardService {
 	return &DashboardService{
 		db:                db,
-		collectionService: NewCollectionService(db),
+		collectionService: NewCollectionService(db, search...),
 	}
 }
 
diff --git a/internal/services/filter_query.go b/internal/services/filter_query.go
index fa7229d2..232a9737 100644
--- a/internal/services/filter_query.go
+++ b/internal/services/filter_query.go
@@ -9,6 +9,7 @@ import (
 	"bookhoard/internal/database"
 
 	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgtype"
 )
 
@@ -873,6 +874,42 @@ func composedQueryBlock(qBind, exactBind string) string {
 	))`
 }
 
+// ComposedLiveMedia — full media rows matching the tree: the TREE path
+// of the smart-collection evaluator (item 3.2). Same filters as
+// ComposedSearch (scope head, family lens via the visibility join,
+// tree clause, optional visible-library belt) but SELECT mi.* so
+// collection surfaces get the whole media row (episode-card stamping,
+// feed position for the replay chain). Replaces the candidate query's
+// Sqlc embed for tree collections; ordering matches the legacy
+// candidate query (title ASC).
+func (s *SearchService) ComposedLiveMedia(ctx context.Context, userID, libraryID pgtype.UUID, visibleIDs []pgtype.UUID, tree *FilterTree) ([]database.MediaItems, error) {
+	b := newFilterBuilder(userID)
+	head := b.headWhere(libraryID, tree.FilterScope()) + treeWhere(tree, b)
+	visibleClause := ""
+	if len(visibleIDs) > 0 {
+		visibleClause = " AND (l.id = ANY(" + b.bind(visibleIDs) + "::uuid[])"
+		if libraryID.Valid {
+			// Redundant by construction; keep SQL valid either way.
+			visibleClause += " OR l.id = " + b.bind(libraryID)
+		}
+		visibleClause += ")"
+	}
+	sqlStr := "SELECT mi.* " + filterFrom + b.userIDBind +
+		b.joinBlock() + `
+WHERE ` + head + visibleClause + `
+ORDER BY mi.title ASC`
+
+	rows, err := s.raw.Query(ctx, sqlStr, b.args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	// Name-based decoding:mi.* column order and the struct order stay
+	// decoupled (position-based scanning would silently break the next
+	// schema append).
+	return pgx.CollectRows(rows, pgx.RowToStructByName[database.MediaItems])
+}
+
 // ComposedCount — the live match count for the builder (rules + scope,
 // no pagination): a true COUNT(*), not the page length.
 func (s *SearchService) ComposedCount(ctx context.Context, userID, libraryID pgtype.UUID, tree *FilterTree) (int, error) {