feat(collections): RLS ownership enforcement at the DB layer

collections + collection_items join the RLS-governed tables, same
doctrine as the media_items family lens (2026-10-29). Policies route
through two PURE predicate functions (app_can_read_collection /
app_can_write_collection) that never query collections — no policy
recursion under FORCE RLS — so a future sharing model is one EXISTS
branch inside the functions, not a schema re-touch. Reads: owner or
admin; writes: owner, admin escape for SYSTEM collections only.

Why: the write path had no app-level ownership gate on Update/Delete/
AddBooks — any authenticated user could mutate another user's
collection by id. The DB is now the enforcement of record; existing
app-level gates (match-mode, reorder, view-settings) stay as
defense-in-depth.

Behavior changes (contract_pins 2026-10-31):
- cross-user GET detail: 200 -> 404 (row invisible)
- cross-user PUT update: silent success -> 404 (ErrNoRows mapping;
  service wrap fixed %v -> %w so errors.Is sees pgx.ErrNoRows)
- cross-user POST books: silent success -> 404
- cross-user DELETE: 204, now a true DB no-op
- anonymous sees nothing; admin persona unchanged

Bootstrap: registration seeds system collections BEFORE the JWT
exists — CreateDefaultCollectionsForUser declares the new user's
identity (rls.WithUser), the same fix mirrored in the test harness
(createDefaultCollectionsForUser owner-scoped; collection sweeps run
under the owner's identity).

Tests: new TestCollectionsRLS pins the cross-user matrix end-to-end
(404 detail/update/add/view-settings, 204 no-op delete, admin escape,
owner positive control, registration seeding under RLS). Harness
fixture writes to non-system collections now run as the row's OWNER
(scopeExecAs/ownerSeedCtx) — the admin write-escape covers system
rows only, and bare-ctx pool reads of collections see nothing.
Filter/playlist/audiobook/scan-state fixtures converted. Full
container suite green (159s).

cmd/server/tests/audiobook_multifile_test.go

@@ -659,12 +659,14 @@ func TestAudiobookFolderSidecarEditDetected(t *testing.T) {
 	require.NoError(t, os.WriteFile(sidecar, []byte(`{"title":"Sidecar Real Titlz","series":["Sidecar Saga (Reading Order) #1"]}`), 0o644))
 	scanTestFolder(t, setup, admin, folder)
 	var collCount int
-	require.NoError(t, setup.DBPool.QueryRow(context.Background(),
+	// Owner-scoped read: collections RLS (2026-10-31) hides rows from
+	// the pool session's SeedIdentity.
+	require.NoError(t, database.NewScopedDB(setup.DBPool).QueryRow(ownerSeedCtx(admin),
 		`SELECT COUNT(*) FROM collections WHERE name = 'Sidecar Saga (Reading Order)' AND user_id = $1`, admin,
 	).Scan(&collCount))
 	require.Equal(t, 1, collCount, "reading-order sidecar edit creates the collection for an existing book")
 	scanTestFolder(t, setup, admin, folder)
-	require.NoError(t, setup.DBPool.QueryRow(context.Background(),
+	require.NoError(t, database.NewScopedDB(setup.DBPool).QueryRow(ownerSeedCtx(admin),
 		`SELECT COUNT(*) FROM collections WHERE name = 'Sidecar Saga (Reading Order)' AND user_id = $1`, admin,
 	).Scan(&collCount))
 	require.Equal(t, 1, collCount, "rescan is idempotent — no duplicate collection")

cmd/server/tests/collections_rls_test.go

@@ -0,0 +1,127 @@
+package main
+
+import (
+	"bytes"
+	"testing"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// Collections RLS (2026-10-31): ownership enforcement moved to the DB
+// layer (p_collections_* + parent-checked collection_items policies in
+// schema.sql, predicates app_can_read/write_collection). The API surface
+// answers invisibility with 404 — including the write endpoints that
+// had NO app-level gate (Update/AddBooks, the flagged gap). Admin keeps
+// the escape; system collections stay per-user; registration still
+// seeds them (the seeding identity fix in
+// CreateDefaultCollectionsForUser is regression-pinned here).
+func TestCollectionsRLS(t *testing.T) {
+	setup := setupTestServer(t)
+	ownerToken := setup.RegularToken // user A: the harness regular user
+	adminToken := setup.Token
+	marker := fmt.Sprintf("rls%d", time.Now().UnixNano()%100000)
+
+	// User B: a second regular user via registration. The register
+	// endpoint is rate-limited — exactly one call. The response's
+	// access_token is B's identity for every probe below.
+	regEmail := fmt.Sprintf("%s@tests.bookhoard.internal", marker)
+	regBody := fmt.Sprintf(
+		`{"email":%q,"username":%q,"password":"Test@Pass123!"}`,
+		regEmail, "rlsb"+marker)
+	regResp, err := http.Post(setup.Server.URL+"/api/auth/register",
+		"application/json", bytes.NewReader([]byte(regBody)))
+	require.NoError(t, err)
+	require.Equal(t, http.StatusCreated, regResp.StatusCode,
+		"registration must succeed — including the system-collection seeding that now runs under the new user's RLS identity")
+	var reg struct {
+		Token string `json:"access_token"`
+	}
+	require.NoError(t, json.NewDecoder(regResp.Body).Decode(&reg))
+	require.NotEmpty(t, reg.Token)
+	otherToken := reg.Token
+	_ = regResp.Body.Close()
+
+	// B's registration seeded B's OWN system collections — visible in
+	// B's list (this is the registration-seeding identity fix, live).
+	code, body := podcastAuthed(t, setup, otherToken, "GET", "/api/collections", "")
+	require.Equal(t, http.StatusOK, code)
+	assert.Contains(t, string(body), "Continue Reading",
+		"registration seeded the new user's system collections under RLS")
+
+	// A creates the target collection.
+	code, body = podcastAuthed(t, setup, ownerToken, "POST", "/api/collections",
+		`{"name":"test RLS Owner ` + marker + `"}`)
+	require.Equal(t, http.StatusCreated, code, "%s", string(body))
+	var coll struct {
+		ID string `json:"id"`
+	}
+	require.NoError(t, json.Unmarshal(body, &coll))
+	t.Cleanup(func() {
+		podcastAuthed(t, setup, ownerToken, "DELETE", "/api/collections/"+coll.ID, "")
+	})
+
+	// ── B (non-owner) probes A's collection: invisible = 404 ──
+	code, _ = podcastAuthed(t, setup, otherToken, "GET", "/api/collections/"+coll.ID, "")
+	require.Equal(t, http.StatusNotFound, code, "detail-by-id is RLS-invisible cross-user")
+
+	code, body = podcastAuthed(t, setup, otherToken, "GET", "/api/collections", "")
+	require.Equal(t, http.StatusOK, code)
+	assert.NotContains(t, string(body), "test RLS Owner "+marker,
+		"the list query stays user-scoped")
+
+	code, body = podcastAuthed(t, setup, otherToken, "PUT", "/api/collections/"+coll.ID,
+		`{"name":"renamed by B"}`)
+	require.Equal(t, http.StatusNotFound, code,
+		"update of an RLS-invisible row answers 404 (was: ungated success): %s", string(body))
+
+	code, body = podcastAuthed(t, setup, otherToken, "POST", "/api/collections/"+coll.ID+"/books",
+		`{"book_ids":[]}`)
+	require.Equal(t, http.StatusNotFound, code,
+		"AddBooks on an RLS-invisible collection answers 404 (the flagged ungated-write gap, closed at the DB)")
+
+	code, body = podcastAuthed(t, setup, otherToken, "PUT",
+		"/api/collections/"+coll.ID+"/view-settings", `{"chain_order":"newest"}`)
+	require.Equal(t, http.StatusNotFound, code,
+		"chain-order write on an invisible collection answers 404")
+
+	code, _ = podcastAuthed(t, setup, otherToken, "DELETE", "/api/collections/"+coll.ID, "")
+	require.Equal(t, http.StatusNoContent, code,
+		"DELETE touches no rows under RLS (silent no-op — no destructive action)")
+
+	// The no-op delete lied about nothing: A still owns the collection.
+	code, body = podcastAuthed(t, setup, ownerToken, "GET", "/api/collections/"+coll.ID, "")
+	require.Equal(t, http.StatusOK, code, "owner retains the collection after B's failed delete")
+
+	// ── admin escape: sees everything, as with media ──
+	code, _ = podcastAuthed(t, setup, adminToken, "GET", "/api/collections/"+coll.ID, "")
+	require.Equal(t, http.StatusOK, code, "admin persona sees collections (policy escape)")
+
+	// ── B's ownership works: B renames B's OWN system collection ──
+	// (positive control — B is not locked out of what B owns)
+	code, body = podcastAuthed(t, setup, otherToken, "GET", "/api/collections", "")
+	require.Equal(t, http.StatusOK, code)
+	var list struct {
+		Collections []struct {
+			ID   string `json:"id"`
+			Name string `json:"name"`
+		} `json:"collections"`
+	}
+	require.NoError(t, json.Unmarshal(body, &list))
+	var bSystem string
+	for _, c := range list.Collections {
+		if c.Name == "Continue Reading" {
+			bSystem = c.ID
+			break
+		}
+	}
+	require.NotEmpty(t, bSystem, "B owns the seeded system collections")
+	code, body = podcastAuthed(t, setup, otherToken, "PUT", "/api/collections/"+bSystem,
+		`{"name":"Continue Reading"}`)
+	require.Contains(t, []int{http.StatusOK, http.StatusCreated}, code,
+		"owner mutation of an OWN collection still works: %s", string(body))
+}

cmd/server/tests/collections_smart_test.go

@@ -213,7 +213,7 @@ func TestSmartCollections(t *testing.T) {
 	t.Run("SystemCollectionsBlockedFromTheEditor", func(t *testing.T) {
 		// System collections may never carry rules/trees — the editor
 		// route refuses them (item 3.4: the page IS the editor).
-		colls, err := setup.DB.GetCollectionsByUser(context.Background(), pgtype.UUID{Bytes: [16]byte(adminID), Valid: true})
+		colls, err := setup.DB.GetCollectionsByUser(ownerSeedCtx(pgtype.UUID{Bytes: [16]byte(adminID), Valid: true}), pgtype.UUID{Bytes: [16]byte(adminID), Valid: true})
 		require.NoError(t, err)
 		var systemID string
 		for _, c := range colls {

cmd/server/tests/filter_builder_test.go

@@ -455,12 +455,17 @@ func TestFilterUserRelativeFields(t *testing.T) {
 		aID, wickID, aID, tideID)
 
 	var collID pgtype.UUID
-	err := setup.DBPool.QueryRow(context.Background(),
+	// Seed as the OWNER (collections RLS, 2026-10-31): the insert
+	// predicate wants actor == owner, and the item/cleanup writes want
+	// the same identity — the admin write-escape covers SYSTEM rows only.
+	err := database.NewScopedDB(setup.DBPool).QueryRow(ownerSeedCtx(aID),
 		`INSERT INTO collections (user_id, name) VALUES ($1, $2) RETURNING id`,
 		aID, fmt.Sprintf("Test Builder Coll %d", time.Now().UnixNano())).Scan(&collID)
 	require.NoError(t, err)
-	t.Cleanup(func() { _ = setup.DB.DeleteCollection(ctx, collID) })
-	seedExec(t, setup.DBPool,
+	t.Cleanup(func() {
+		scopeExecAs(t, setup, aID, `DELETE FROM collections WHERE id = $1`, collID)
+	})
+	scopeExecAs(t, setup, aID,
 		`INSERT INTO collection_items (collection_id, media_item_id) VALUES ($1,$2)`, collID, tideID)
 
 	titlesFor := func(token string, qf string) []string {
@@ -542,7 +547,6 @@ func TestFilterSuggestionsUnderRules(t *testing.T) {
 	libUUID, _ := builderFixtureLib(t, setup, userID, "Sug")
 
 	// Add a second distinct author+genre pair (trigram-disjoint).
-	ctx := context.Background()
 	_, err := setup.DB.CreateMediaItem(seedCtx(), database.CreateMediaItemParams{
 		LibraryID: pgtype.UUID{Bytes: libUUID, Valid: true},
 		Title:     "Sug Dune",
@@ -670,16 +674,21 @@ func TestFilterSuggestionsUnderRules(t *testing.T) {
 	// offered with the surviving count; zero-match containers never are.
 	userA := getRegularUserID(t, setup.DB)
 	var collID pgtype.UUID
-	err = setup.DBPool.QueryRow(context.Background(),
+	// Seed as the OWNER (collections RLS, 2026-10-31) — same identity
+	// rule as the first seeding site in this file.
+	ownerID := pgtype.UUID{Bytes: [16]byte(userA), Valid: true}
+	err = database.NewScopedDB(setup.DBPool).QueryRow(ownerSeedCtx(ownerID),
 		`INSERT INTO collections (user_id, name) VALUES ($1, $2) RETURNING id`,
-		pgtype.UUID{Bytes: [16]byte(userA), Valid: true},
+		ownerID,
 		fmt.Sprintf("Test Builder Sug Coll %d", time.Now().UnixNano())).Scan(&collID)
 	require.NoError(t, err)
-	t.Cleanup(func() { _ = setup.DB.DeleteCollection(ctx, collID) })
+	t.Cleanup(func() {
+		scopeExecAs(t, setup, ownerID, `DELETE FROM collections WHERE id = $1`, collID)
+	})
 	var tideID pgtype.UUID
 	err = setup.DBPool.QueryRow(context.Background(), `SELECT id FROM media_items WHERE title = $1`, "Sug Tide").Scan(&tideID)
 	require.NoError(t, err)
-	seedExec(t, setup.DBPool,
+	scopeExecAs(t, setup, ownerID,
 		`INSERT INTO collection_items (collection_id, media_item_id) VALUES ($1, $2)`, collID, tideID)
 
 	status, results = suggest("collection", " ", "")

cmd/server/tests/playlist_collections_test.go

@@ -13,6 +13,8 @@ import (
 
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/require"
+
+	"bookhoard/internal/database"
 )
 
 // A2c end-to-end: an ABS sidecar whose series array mixes a real series and
@@ -67,13 +69,14 @@ func TestPlaylistCollectionsEndToEnd(t *testing.T) {
 	require.NotEmpty(t, foundPath)
 
 	// (b) The playlist collection exists with provenance, dashboard pin,
-	// and the item at reading position 7.
+	// and the item at reading position 7. Owner-scoped read: collections
+	// RLS (2026-10-31) hides the row from the pool session's SeedIdentity.
 	adminUUIDStr := adminID.String()
 	var collID uuid.UUID
 	var collName, collDesc string
 	var showOnDashboard bool
 	var viewSettingsRaw []byte
-	require.NoError(t, setup.DBPool.QueryRow(context.Background(),
+	require.NoError(t, database.NewScopedDB(setup.DBPool).QueryRow(ownerSeedCtx(adminID),
 		`SELECT id, name, description, show_on_dashboard, view_settings
 		 FROM collections WHERE user_id = $1 AND name = 'The Tagged Saga (Reading Order)'`,
 		adminID).Scan(&collID, &collName, &collDesc, &showOnDashboard, &viewSettingsRaw))
@@ -85,7 +88,9 @@ func TestPlaylistCollectionsEndToEnd(t *testing.T) {
 
 	var position *int32
 	var itemCount int
-	require.NoError(t, setup.DBPool.QueryRow(context.Background(),
+	// Owner-scoped reads: collections RLS (2026-10-31) — items ride the
+	// parent's readability, so the pool session's SeedIdentity sees none.
+	require.NoError(t, database.NewScopedDB(setup.DBPool).QueryRow(ownerSeedCtx(adminID),
 		`SELECT ci.position, COUNT(*) OVER () FROM collection_items ci
 		 WHERE ci.collection_id = $1`, collID).Scan(&position, &itemCount))
 	require.Equal(t, 1, itemCount)
@@ -96,11 +101,11 @@ func TestPlaylistCollectionsEndToEnd(t *testing.T) {
 	// (c) Rescan: no duplicate collection, no duplicate membership.
 	scanTestFolder(t, setup, adminID, folder)
 	var collectionCount, membershipCount int
-	require.NoError(t, setup.DBPool.QueryRow(context.Background(),
+	require.NoError(t, database.NewScopedDB(setup.DBPool).QueryRow(ownerSeedCtx(adminID),
 		`SELECT COUNT(*) FROM collections WHERE user_id = $1 AND name = 'The Tagged Saga (Reading Order)'`,
 		adminID).Scan(&collectionCount))
 	require.Equal(t, 1, collectionCount)
-	require.NoError(t, setup.DBPool.QueryRow(context.Background(),
+	require.NoError(t, database.NewScopedDB(setup.DBPool).QueryRow(ownerSeedCtx(adminID),
 		`SELECT COUNT(*) FROM collection_items WHERE collection_id = $1`, collID).Scan(&membershipCount))
 	require.Equal(t, 1, membershipCount)
 
@@ -131,7 +136,9 @@ func TestPlaylistCollectionsEndToEnd(t *testing.T) {
 	// (e) hide_finished + Up Next + completion marker.
 	// Flip the collection's flag on, mark the single item finished for the
 	// admin, and the dashboard section becomes Complete with no items.
-	_, err = setup.DBPool.Exec(context.Background(),
+	// Owner-or-admin UPDATE policy: run as ADMIN (collections RLS,
+	// 2026-10-31).
+	adminScopeExec(t, setup, adminCtxValue(t, setup),
 		`UPDATE collections SET view_settings = view_settings || '{"hide_finished": true}'::jsonb WHERE id = $1`, collID)
 	require.NoError(t, err)
 	_, err = setup.DBPool.Exec(context.Background(),

cmd/server/tests/scan_state_test.go

@@ -207,12 +207,13 @@ func TestScanManifestLifecycle(t *testing.T) {
 	require.NoError(t, os.WriteFile(opfPath, []byte(`{"title":"Manifesu Book","series":["Lifecycle Saga (Reading Order) #1"]}`), 0644))
 	scanTestFolder(t, setup, admin, folder)
 	var collCount int
-	require.NoError(t, setup.DBPool.QueryRow(context.Background(),
+	// Owner-scoped read: collections RLS (2026-10-31).
+	require.NoError(t, database.NewScopedDB(setup.DBPool).QueryRow(ownerSeedCtx(admin),
 		`SELECT COUNT(*) FROM collections WHERE name = 'Lifecycle Saga (Reading Order)' AND user_id = $1`, admin,
 	).Scan(&collCount))
 	assert.Equal(t, 1, collCount, "reading-order sidecar added to an existing book creates its collection")
 	scanTestFolder(t, setup, admin, folder)
-	require.NoError(t, setup.DBPool.QueryRow(context.Background(),
+	require.NoError(t, database.NewScopedDB(setup.DBPool).QueryRow(ownerSeedCtx(admin),
 		`SELECT COUNT(*) FROM collections WHERE name = 'Lifecycle Saga (Reading Order)' AND user_id = $1`, admin,
 	).Scan(&collCount))
 	assert.Equal(t, 1, collCount, "rescan is idempotent — no duplicate collection")

cmd/server/tests/test_helpers_test.go

@@ -329,6 +329,22 @@ func seedCtx() context.Context {
 	return rls.WithUser(context.Background(), rls.SeedIdentity)
 }
 
+// ownerSeedCtx returns a context carrying a fixture user's identity,
+// for seeding rows OWNED by that user. Collections RLS (2026-10-31):
+// the write predicates want actor == owner for non-system rows (the
+// admin write-escape covers SYSTEM collections only), and reads under
+// the pool session's SeedIdentity see nothing.
+func ownerSeedCtx(userID pgtype.UUID) context.Context {
+	return rls.WithUser(context.Background(), userID)
+}
+
+// scopeExecAs is adminScopeExec's generic form: raw SQL under ANY
+// declared identity. Use it (with the row's OWNER) for fixture writes
+// to non-system collections — see ownerSeedCtx.
+func scopeExecAs(t *testing.T, setup *TestServerSetup, userID pgtype.UUID, sql string, args ...any) {
+	adminScopeExec(t, setup, userID, sql, args...)
+}
+
 // seedExec runs a raw statement against the pool under the seed
 // identity. The bare pool bypasses ScopedDB (nothing reads the ctx for
 // the GUC), so governed tables need the identity declared manually
@@ -356,7 +372,12 @@ func uuidToPGType(u uuid.UUID) pgtype.UUID {
 
 // createDefaultCollectionsForUser creates the 4 default system collections for a user
 func createDefaultCollectionsForUser(t *testing.T, db *database.Queries, userID pgtype.UUID) {
-	ctx := context.Background()
+	// Owner-scoped seeding: the collections RLS policies (2026-10-31)
+	// need an acting identity, and the harness seeds before any JWT —
+	// the same bootstrap fix as CreateDefaultCollectionsForUser in
+	// internal/handlers/auth.go. Owner == actor, so SELECT sees the
+	// rows, the INSERT passes, and the heal-UPDATE passes.
+	ctx := rls.WithUser(context.Background(), userID)
 	// Canonical Title-case names — the same list the registration seed
 	// (CreateDefaultCollectionsForUser) and RestoreSystemCollection use.
 	// A stale kebab-case copy lived here once and duplicated every
@@ -772,11 +793,15 @@ func setupTestServer(t *testing.T) *TestServerSetup {
 	// run's creates die on UNIQUE(user_id, name) — the "collections
 	// 500-panic" rot. System collections are skipped (permanent rows).
 	// Same convention as the library pass: names containing "test".
-	adminColls, cerr := queries.GetCollectionsByUser(ctx, pgtype.UUID{Bytes: adminUUID, Valid: true})
+	// Swept under the OWNER's identity: collections RLS (2026-10-31)
+	// makes unscoped reads return nothing, which would silently turn
+	// this cleanup into a no-op.
+	adminScope := rls.WithUser(ctx, pgtype.UUID{Bytes: adminUUID, Valid: true})
+	adminColls, cerr := queries.GetCollectionsByUser(adminScope, pgtype.UUID{Bytes: adminUUID, Valid: true})
 	if cerr == nil {
 		for _, coll := range adminColls {
 			if !coll.IsSystemCollection.Bool && strings.Contains(strings.ToLower(coll.Name), "test") {
-				queries.DeleteCollection(ctx, coll.ID)
+				queries.DeleteCollection(adminScope, coll.ID)
 			}
 		}
 	}
@@ -850,11 +875,13 @@ func setupTestServer(t *testing.T) *TestServerSetup {
 
 		// Same pass for test-created COLLECTIONS (the "collections
 		// 500-panic" rot: they lingered forever and poisoned later runs).
-		adminColls, cerr := queries.GetCollectionsByUser(ctx, pgtype.UUID{Bytes: adminUUID, Valid: true})
+		// Owner-scoped for the same RLS reason as the setup sweep.
+		adminScope := rls.WithUser(ctx, pgtype.UUID{Bytes: adminUUID, Valid: true})
+		adminColls, cerr := queries.GetCollectionsByUser(adminScope, pgtype.UUID{Bytes: adminUUID, Valid: true})
 		if cerr == nil {
 			for _, coll := range adminColls {
 				if !coll.IsSystemCollection.Bool && strings.Contains(strings.ToLower(coll.Name), "test") {
-					queries.DeleteCollection(ctx, coll.ID)
+					queries.DeleteCollection(adminScope, coll.ID)
 				}
 			}
 		}