diff --git a/internal/db/db.go b/internal/db/db.go
new file mode 100644
index 0000000..e96509f
--- /dev/null
+++ b/internal/db/db.go
@@ -0,0 +1,102 @@
+package db
+
+import (
+	"database/sql"
+	"errors"
+	"os"
+	"path/filepath"
+
+	_ "modernc.org/sqlite"
+)
+
+var (
+	ErrNotFound        = errors.New("not_found")
+	ErrAlreadyPromoted = errors.New("invalid_promote")
+	ErrAlreadyFluid    = errors.New("invalid_demote")
+)
+
+type Store struct {
+	db *sql.DB
+}
+
+func Open(path string) (*Store, error) {
+	db, err := sql.Open("sqlite", path)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, pragma := range []string{
+		"PRAGMA journal_mode = WAL",
+		"PRAGMA foreign_keys = ON",
+		"PRAGMA busy_timeout = 5000",
+	} {
+		if _, err := db.Exec(pragma); err != nil {
+			db.Close()
+			return nil, err
+		}
+	}
+
+	s := &Store{db: db}
+	if err := s.migrate(); err != nil {
+		db.Close()
+		return nil, err
+	}
+	return s, nil
+}
+
+func (s *Store) Close() error {
+	return s.db.Close()
+}
+
+func (s *Store) migrate() error {
+	_, err := s.db.Exec(`
+		CREATE TABLE IF NOT EXISTS entities (
+			id          TEXT PRIMARY KEY,
+			created_at  TEXT NOT NULL,
+			modified_at TEXT NOT NULL,
+			body        TEXT NOT NULL,
+			glyph       TEXT NOT NULL
+				CHECK (glyph IN ('todo', 'event', 'note')),
+			time_anchor TEXT,
+			completed_at TEXT,
+			pinned      INTEGER NOT NULL DEFAULT 0,
+			deleted_at  TEXT,
+			card_type   TEXT
+				CHECK (card_type IN ('snippet', 'template', 'checklist', 'decision', 'link')
+				       OR card_type IS NULL),
+			card_data   TEXT,
+			use_count   INTEGER NOT NULL DEFAULT 0,
+			last_used_at TEXT
+		);
+
+		CREATE TABLE IF NOT EXISTS entity_tags (
+			entity_id TEXT NOT NULL REFERENCES entities(id) ON DELETE CASCADE,
+			tag       TEXT NOT NULL,
+			PRIMARY KEY (entity_id, tag)
+		);
+
+		CREATE INDEX IF NOT EXISTS idx_entities_created
+			ON entities(created_at DESC) WHERE deleted_at IS NULL;
+		CREATE INDEX IF NOT EXISTS idx_entities_card_use
+			ON entities(use_count DESC)
+			WHERE card_type IS NOT NULL AND deleted_at IS NULL;
+		CREATE INDEX IF NOT EXISTS idx_entity_tags_tag
+			ON entity_tags(tag);
+	`)
+	return err
+}
+
+func DefaultPath() (string, error) {
+	if env := os.Getenv("NIB_DB"); env != "" {
+		return env, nil
+	}
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", err
+	}
+	dir := filepath.Join(home, ".nib")
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		return "", err
+	}
+	return filepath.Join(dir, "nib.db"), nil
+}
diff --git a/internal/db/db_test.go b/internal/db/db_test.go
new file mode 100644
index 0000000..a3e24df
--- /dev/null
+++ b/internal/db/db_test.go
@@ -0,0 +1,80 @@
+package db
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func testStore(t *testing.T) *Store {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "test.db")
+	s, err := Open(path)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	t.Cleanup(func() { s.Close() })
+	return s
+}
+
+func TestOpen_CreatesFile(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "test.db")
+	s, err := Open(path)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	defer s.Close()
+
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		t.Fatal("database file not created")
+	}
+}
+
+func TestOpen_WALMode(t *testing.T) {
+	s := testStore(t)
+	var mode string
+	if err := s.db.QueryRow("PRAGMA journal_mode").Scan(&mode); err != nil {
+		t.Fatal(err)
+	}
+	if mode != "wal" {
+		t.Errorf("expected wal, got %s", mode)
+	}
+}
+
+func TestOpen_ForeignKeys(t *testing.T) {
+	s := testStore(t)
+	var fk int
+	if err := s.db.QueryRow("PRAGMA foreign_keys").Scan(&fk); err != nil {
+		t.Fatal(err)
+	}
+	if fk != 1 {
+		t.Errorf("expected foreign_keys=1, got %d", fk)
+	}
+}
+
+func TestOpen_MigrateIdempotent(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "test.db")
+	s1, err := Open(path)
+	if err != nil {
+		t.Fatalf("first Open: %v", err)
+	}
+	s1.Close()
+
+	s2, err := Open(path)
+	if err != nil {
+		t.Fatalf("second Open: %v", err)
+	}
+	s2.Close()
+}
+
+func TestDefaultPath_EnvOverride(t *testing.T) {
+	want := "/tmp/custom-nib.db"
+	t.Setenv("NIB_DB", want)
+	got, err := DefaultPath()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("expected %s, got %s", want, got)
+	}
+}
diff --git a/internal/db/entities.go b/internal/db/entities.go
new file mode 100644
index 0000000..152d30f
--- /dev/null
+++ b/internal/db/entities.go
@@ -0,0 +1,540 @@
+package db
+
+import (
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"strings"
+	"time"
+
+	nibulid "github.com/lerko/nib/internal/ulid"
+)
+
+type Glyph string
+
+const (
+	GlyphNote  Glyph = "note"
+	GlyphTodo  Glyph = "todo"
+	GlyphEvent Glyph = "event"
+)
+
+type CardType string
+
+const (
+	CardSnippet   CardType = "snippet"
+	CardTemplate  CardType = "template"
+	CardChecklist CardType = "checklist"
+	CardDecision  CardType = "decision"
+	CardLink      CardType = "link"
+)
+
+func ValidGlyph(s string) bool {
+	switch Glyph(s) {
+	case GlyphNote, GlyphTodo, GlyphEvent:
+		return true
+	}
+	return false
+}
+
+func ValidCardType(s string) bool {
+	switch CardType(s) {
+	case CardSnippet, CardTemplate, CardChecklist, CardDecision, CardLink:
+		return true
+	}
+	return false
+}
+
+type Entity struct {
+	ID          string
+	CreatedAt   time.Time
+	ModifiedAt  time.Time
+	Body        string
+	Glyph       Glyph
+	TimeAnchor  *string
+	CompletedAt *time.Time
+	Pinned      bool
+	DeletedAt   *time.Time
+	CardType    *CardType
+	CardData    *string
+	UseCount    int
+	LastUsedAt  *time.Time
+	Tags        []string
+}
+
+type ListParams struct {
+	Tag            *string
+	Date           *string
+	Since          *time.Time
+	CardsOnly      bool
+	IncludeDeleted bool
+	CardTypeFilter *CardType
+	Sort           string
+	Order          string
+	Limit          int
+	Offset         int
+}
+
+func DefaultListParams() ListParams {
+	return ListParams{
+		Sort:  "created",
+		Order: "desc",
+		Limit: 50,
+	}
+}
+
+type EntityUpdate struct {
+	Body       *string
+	Glyph      *Glyph
+	TimeAnchor *string
+	ClearTime  bool
+	Pinned     *bool
+	CardType   *CardType
+	CardData   *string
+	Tags       *[]string
+}
+
+func (s *Store) Create(e *Entity) error {
+	now := time.Now().UTC()
+	e.ID = nibulid.New()
+	e.CreatedAt = now
+	e.ModifiedAt = now
+	if e.Tags == nil {
+		e.Tags = []string{}
+	}
+
+	tx, err := s.db.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+
+	_, err = tx.Exec(`
+		INSERT INTO entities (id, created_at, modified_at, body, glyph, time_anchor,
+			completed_at, pinned, deleted_at, card_type, card_data, use_count, last_used_at)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+		e.ID,
+		e.CreatedAt.Format(time.RFC3339),
+		e.ModifiedAt.Format(time.RFC3339),
+		e.Body,
+		string(e.Glyph),
+		e.TimeAnchor,
+		formatTimePtr(e.CompletedAt),
+		boolToInt(e.Pinned),
+		formatTimePtr(e.DeletedAt),
+		cardTypePtr(e.CardType),
+		e.CardData,
+		e.UseCount,
+		formatTimePtr(e.LastUsedAt),
+	)
+	if err != nil {
+		return err
+	}
+
+	if err := insertTags(tx, e.ID, e.Tags); err != nil {
+		return err
+	}
+
+	return tx.Commit()
+}
+
+func (s *Store) Get(id string) (*Entity, error) {
+	e := &Entity{}
+	var createdAt, modifiedAt string
+	var completedAt, deletedAt, lastUsedAt sql.NullString
+	var timeAnchor, cardType, cardData sql.NullString
+	var pinned int
+
+	err := s.db.QueryRow(`
+		SELECT id, created_at, modified_at, body, glyph, time_anchor,
+			completed_at, pinned, deleted_at, card_type, card_data, use_count, last_used_at
+		FROM entities WHERE id = ?`, id).Scan(
+		&e.ID, &createdAt, &modifiedAt, &e.Body, &e.Glyph, &timeAnchor,
+		&completedAt, &pinned, &deletedAt, &cardType, &cardData, &e.UseCount, &lastUsedAt,
+	)
+	if err == sql.ErrNoRows {
+		return nil, ErrNotFound
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	e.CreatedAt, _ = time.Parse(time.RFC3339, createdAt)
+	e.ModifiedAt, _ = time.Parse(time.RFC3339, modifiedAt)
+	e.TimeAnchor = nullToPtr(timeAnchor)
+	e.CompletedAt = parseTimePtr(completedAt)
+	e.Pinned = pinned != 0
+	e.DeletedAt = parseTimePtr(deletedAt)
+	e.CardType = nullToCardType(cardType)
+	e.CardData = nullToPtr(cardData)
+	e.LastUsedAt = parseTimePtr(lastUsedAt)
+
+	tags, err := s.loadTags(id)
+	if err != nil {
+		return nil, err
+	}
+	e.Tags = tags
+
+	return e, nil
+}
+
+func (s *Store) List(params ListParams) ([]*Entity, error) {
+	var where []string
+	var args []any
+
+	if !params.IncludeDeleted {
+		where = append(where, "e.deleted_at IS NULL")
+	}
+	if params.Tag != nil {
+		where = append(where, "e.id IN (SELECT entity_id FROM entity_tags WHERE tag = ?)")
+		args = append(args, *params.Tag)
+	}
+	if params.Date != nil {
+		where = append(where, "date(e.created_at) = ?")
+		args = append(args, *params.Date)
+	}
+	if params.Since != nil {
+		where = append(where, "e.created_at >= ?")
+		args = append(args, params.Since.Format(time.RFC3339))
+	}
+	if params.CardsOnly {
+		where = append(where, "e.card_type IS NOT NULL")
+	}
+	if params.CardTypeFilter != nil {
+		where = append(where, "e.card_type = ?")
+		args = append(args, string(*params.CardTypeFilter))
+	}
+
+	whereClause := ""
+	if len(where) > 0 {
+		whereClause = "WHERE " + strings.Join(where, " AND ")
+	}
+
+	orderCol := "e.created_at"
+	if params.Sort == "use_count" {
+		orderCol = "e.use_count"
+	}
+	orderDir := "DESC"
+	if strings.EqualFold(params.Order, "asc") {
+		orderDir = "ASC"
+	}
+
+	limit := params.Limit
+	if limit <= 0 {
+		limit = 50
+	}
+
+	query := fmt.Sprintf(`
+		SELECT e.id, e.created_at, e.modified_at, e.body, e.glyph, e.time_anchor,
+			e.completed_at, e.pinned, e.deleted_at, e.card_type, e.card_data,
+			e.use_count, e.last_used_at
+		FROM entities e
+		%s
+		ORDER BY %s %s
+		LIMIT ? OFFSET ?`, whereClause, orderCol, orderDir)
+
+	args = append(args, limit, params.Offset)
+
+	rows, err := s.db.Query(query, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var entities []*Entity
+	for rows.Next() {
+		e := &Entity{}
+		var createdAt, modifiedAt string
+		var completedAt, deletedAt, lastUsedAt sql.NullString
+		var timeAnchor, cardType, cardData sql.NullString
+		var pinned int
+
+		if err := rows.Scan(
+			&e.ID, &createdAt, &modifiedAt, &e.Body, &e.Glyph, &timeAnchor,
+			&completedAt, &pinned, &deletedAt, &cardType, &cardData,
+			&e.UseCount, &lastUsedAt,
+		); err != nil {
+			return nil, err
+		}
+
+		e.CreatedAt, _ = time.Parse(time.RFC3339, createdAt)
+		e.ModifiedAt, _ = time.Parse(time.RFC3339, modifiedAt)
+		e.TimeAnchor = nullToPtr(timeAnchor)
+		e.CompletedAt = parseTimePtr(completedAt)
+		e.Pinned = pinned != 0
+		e.DeletedAt = parseTimePtr(deletedAt)
+		e.CardType = nullToCardType(cardType)
+		e.CardData = nullToPtr(cardData)
+		e.LastUsedAt = parseTimePtr(lastUsedAt)
+
+		entities = append(entities, e)
+	}
+
+	for _, e := range entities {
+		tags, err := s.loadTags(e.ID)
+		if err != nil {
+			return nil, err
+		}
+		e.Tags = tags
+	}
+
+	return entities, nil
+}
+
+func (s *Store) Update(id string, u *EntityUpdate) error {
+	existing, err := s.Get(id)
+	if err != nil {
+		return err
+	}
+
+	tx, err := s.db.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+
+	var sets []string
+	var args []any
+
+	sets = append(sets, "modified_at = ?")
+	args = append(args, time.Now().UTC().Format(time.RFC3339))
+
+	if u.Body != nil {
+		sets = append(sets, "body = ?")
+		args = append(args, *u.Body)
+	}
+	if u.Glyph != nil {
+		sets = append(sets, "glyph = ?")
+		args = append(args, string(*u.Glyph))
+	}
+	if u.ClearTime {
+		sets = append(sets, "time_anchor = NULL")
+	} else if u.TimeAnchor != nil {
+		sets = append(sets, "time_anchor = ?")
+		args = append(args, *u.TimeAnchor)
+	}
+	if u.Pinned != nil {
+		sets = append(sets, "pinned = ?")
+		args = append(args, boolToInt(*u.Pinned))
+	}
+	if u.CardType != nil {
+		sets = append(sets, "card_type = ?")
+		args = append(args, string(*u.CardType))
+	}
+	if u.CardData != nil {
+		sets = append(sets, "card_data = ?")
+		args = append(args, *u.CardData)
+	}
+
+	args = append(args, existing.ID)
+	query := fmt.Sprintf("UPDATE entities SET %s WHERE id = ?", strings.Join(sets, ", "))
+
+	if _, err := tx.Exec(query, args...); err != nil {
+		return err
+	}
+
+	if u.Tags != nil {
+		if _, err := tx.Exec("DELETE FROM entity_tags WHERE entity_id = ?", existing.ID); err != nil {
+			return err
+		}
+		if err := insertTags(tx, existing.ID, *u.Tags); err != nil {
+			return err
+		}
+	}
+
+	return tx.Commit()
+}
+
+func (s *Store) Promote(id string, cardType CardType, cardData *string) error {
+	e, err := s.Get(id)
+	if err != nil {
+		return err
+	}
+	if e.CardType != nil {
+		return ErrAlreadyPromoted
+	}
+
+	dataVal := "{}"
+	if cardData != nil {
+		dataVal = *cardData
+	}
+
+	_, err = s.db.Exec(`
+		UPDATE entities SET card_type = ?, card_data = ?, modified_at = ?
+		WHERE id = ?`,
+		string(cardType), dataVal, time.Now().UTC().Format(time.RFC3339), id)
+	return err
+}
+
+func (s *Store) Demote(id string) error {
+	e, err := s.Get(id)
+	if err != nil {
+		return err
+	}
+	if e.CardType == nil {
+		return ErrAlreadyFluid
+	}
+
+	_, err = s.db.Exec(`
+		UPDATE entities SET card_type = NULL, card_data = NULL,
+			use_count = 0, last_used_at = NULL, modified_at = ?
+		WHERE id = ?`,
+		time.Now().UTC().Format(time.RFC3339), id)
+	return err
+}
+
+type DeleteResult int
+
+const (
+	DeletedSoft DeleteResult = iota
+	DeletedHard
+)
+
+func (s *Store) SoftDelete(id string) (DeleteResult, error) {
+	var deletedAt sql.NullString
+	err := s.db.QueryRow("SELECT deleted_at FROM entities WHERE id = ?", id).Scan(&deletedAt)
+	if err == sql.ErrNoRows {
+		return 0, ErrNotFound
+	}
+	if err != nil {
+		return 0, err
+	}
+
+	if deletedAt.Valid {
+		_, err = s.db.Exec("DELETE FROM entities WHERE id = ?", id)
+		return DeletedHard, err
+	}
+
+	_, err = s.db.Exec("UPDATE entities SET deleted_at = ? WHERE id = ?",
+		time.Now().UTC().Format(time.RFC3339), id)
+	return DeletedSoft, err
+}
+
+func (s *Store) IncrementUse(id string) error {
+	res, err := s.db.Exec(`
+		UPDATE entities SET use_count = use_count + 1, last_used_at = ?
+		WHERE id = ?`,
+		time.Now().UTC().Format(time.RFC3339), id)
+	if err != nil {
+		return err
+	}
+	n, _ := res.RowsAffected()
+	if n == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+func (s *Store) Resolve(prefix string) (string, error) {
+	rows, err := s.db.Query("SELECT id FROM entities WHERE id LIKE ?", prefix+"%")
+	if err != nil {
+		return "", err
+	}
+	defer rows.Close()
+
+	var ids []string
+	for rows.Next() {
+		var id string
+		if err := rows.Scan(&id); err != nil {
+			return "", err
+		}
+		ids = append(ids, id)
+	}
+
+	switch len(ids) {
+	case 0:
+		return "", ErrNotFound
+	case 1:
+		return ids[0], nil
+	default:
+		return "", fmt.Errorf("ambiguous id prefix %q matches %d entities", prefix, len(ids))
+	}
+}
+
+// helpers
+
+func (s *Store) loadTags(entityID string) ([]string, error) {
+	rows, err := s.db.Query("SELECT tag FROM entity_tags WHERE entity_id = ? ORDER BY tag", entityID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var tags []string
+	for rows.Next() {
+		var tag string
+		if err := rows.Scan(&tag); err != nil {
+			return nil, err
+		}
+		tags = append(tags, tag)
+	}
+	if tags == nil {
+		tags = []string{}
+	}
+	return tags, nil
+}
+
+func insertTags(tx *sql.Tx, entityID string, tags []string) error {
+	for _, tag := range tags {
+		if _, err := tx.Exec("INSERT OR IGNORE INTO entity_tags (entity_id, tag) VALUES (?, ?)",
+			entityID, tag); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func formatTimePtr(t *time.Time) interface{} {
+	if t == nil {
+		return nil
+	}
+	return t.Format(time.RFC3339)
+}
+
+func parseTimePtr(ns sql.NullString) *time.Time {
+	if !ns.Valid {
+		return nil
+	}
+	t, err := time.Parse(time.RFC3339, ns.String)
+	if err != nil {
+		return nil
+	}
+	return &t
+}
+
+func nullToPtr(ns sql.NullString) *string {
+	if !ns.Valid {
+		return nil
+	}
+	return &ns.String
+}
+
+func nullToCardType(ns sql.NullString) *CardType {
+	if !ns.Valid {
+		return nil
+	}
+	ct := CardType(ns.String)
+	return &ct
+}
+
+func cardTypePtr(ct *CardType) interface{} {
+	if ct == nil {
+		return nil
+	}
+	return string(*ct)
+}
+
+func boolToInt(b bool) int {
+	if b {
+		return 1
+	}
+	return 0
+}
+
+func (e *Entity) CardDataJSON() map[string]interface{} {
+	if e.CardData == nil {
+		return nil
+	}
+	var m map[string]interface{}
+	json.Unmarshal([]byte(*e.CardData), &m)
+	return m
+}
diff --git a/internal/db/entities_test.go b/internal/db/entities_test.go
new file mode 100644
index 0000000..19ef9e2
--- /dev/null
+++ b/internal/db/entities_test.go
@@ -0,0 +1,443 @@
+package db
+
+import (
+	"testing"
+	"time"
+)
+
+func ptr[T any](v T) *T {
+	return &v
+}
+
+func TestCreate_Note(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "hello world", Glyph: GlyphNote}
+	if err := s.Create(e); err != nil {
+		t.Fatal(err)
+	}
+	if e.ID == "" {
+		t.Fatal("ID not set")
+	}
+
+	got, err := s.Get(e.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Body != "hello world" {
+		t.Errorf("body: got %q", got.Body)
+	}
+	if got.Glyph != GlyphNote {
+		t.Errorf("glyph: got %q", got.Glyph)
+	}
+}
+
+func TestCreate_TodoWithTimeAnchor(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "deploy", Glyph: GlyphTodo, TimeAnchor: ptr("14:00")}
+	if err := s.Create(e); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := s.Get(e.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.TimeAnchor == nil || *got.TimeAnchor != "14:00" {
+		t.Errorf("time_anchor: got %v", got.TimeAnchor)
+	}
+}
+
+func TestCreate_WithTags(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "deploy nginx", Glyph: GlyphNote, Tags: []string{"ops", "nginx"}}
+	if err := s.Create(e); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := s.Get(e.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got.Tags) != 2 {
+		t.Fatalf("expected 2 tags, got %d", len(got.Tags))
+	}
+}
+
+func TestCreate_WithCardType(t *testing.T) {
+	s := testStore(t)
+	ct := CardSnippet
+	e := &Entity{Body: "trick", Glyph: GlyphNote, CardType: &ct}
+	if err := s.Create(e); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := s.Get(e.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.CardType == nil || *got.CardType != CardSnippet {
+		t.Errorf("card_type: got %v", got.CardType)
+	}
+}
+
+func TestGet_NotFound(t *testing.T) {
+	s := testStore(t)
+	_, err := s.Get("01NONEXISTENT0000000000000")
+	if err != ErrNotFound {
+		t.Errorf("expected ErrNotFound, got %v", err)
+	}
+}
+
+func TestList_DefaultParams(t *testing.T) {
+	s := testStore(t)
+	for i := 0; i < 3; i++ {
+		s.Create(&Entity{Body: "note", Glyph: GlyphNote})
+	}
+
+	entities, err := s.List(DefaultListParams())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entities) != 3 {
+		t.Fatalf("expected 3, got %d", len(entities))
+	}
+	// desc order: newest first
+	if entities[0].CreatedAt.Before(entities[2].CreatedAt) {
+		t.Error("expected newest first")
+	}
+}
+
+func TestList_FilterByTag(t *testing.T) {
+	s := testStore(t)
+	s.Create(&Entity{Body: "a", Glyph: GlyphNote, Tags: []string{"ops"}})
+	s.Create(&Entity{Body: "b", Glyph: GlyphNote, Tags: []string{"home"}})
+	s.Create(&Entity{Body: "c", Glyph: GlyphNote, Tags: []string{"ops", "home"}})
+
+	p := DefaultListParams()
+	tag := "ops"
+	p.Tag = &tag
+
+	entities, err := s.List(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entities) != 2 {
+		t.Errorf("expected 2 entities with tag ops, got %d", len(entities))
+	}
+}
+
+func TestList_FilterByDate(t *testing.T) {
+	s := testStore(t)
+	s.Create(&Entity{Body: "today", Glyph: GlyphNote})
+
+	p := DefaultListParams()
+	date := time.Now().UTC().Format("2006-01-02")
+	p.Date = &date
+
+	entities, err := s.List(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entities) != 1 {
+		t.Errorf("expected 1, got %d", len(entities))
+	}
+
+	otherDate := "2020-01-01"
+	p.Date = &otherDate
+	entities, err = s.List(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entities) != 0 {
+		t.Errorf("expected 0 for past date, got %d", len(entities))
+	}
+}
+
+func TestList_CardsOnly(t *testing.T) {
+	s := testStore(t)
+	s.Create(&Entity{Body: "fluid", Glyph: GlyphNote})
+	ct := CardSnippet
+	s.Create(&Entity{Body: "card", Glyph: GlyphNote, CardType: &ct})
+
+	p := DefaultListParams()
+	p.CardsOnly = true
+	entities, err := s.List(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entities) != 1 {
+		t.Fatalf("expected 1 card, got %d", len(entities))
+	}
+	if entities[0].Body != "card" {
+		t.Errorf("expected card entity, got %q", entities[0].Body)
+	}
+}
+
+func TestList_IncludeDeleted(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "doomed", Glyph: GlyphNote}
+	s.Create(e)
+	s.SoftDelete(e.ID)
+
+	p := DefaultListParams()
+	entities, err := s.List(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entities) != 0 {
+		t.Error("deleted entity should be excluded by default")
+	}
+
+	p.IncludeDeleted = true
+	entities, err = s.List(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entities) != 1 {
+		t.Error("deleted entity should appear with include_deleted")
+	}
+}
+
+func TestList_SortByUseCount(t *testing.T) {
+	s := testStore(t)
+	ct := CardSnippet
+	e1 := &Entity{Body: "low", Glyph: GlyphNote, CardType: &ct}
+	e2 := &Entity{Body: "high", Glyph: GlyphNote, CardType: &ct}
+	s.Create(e1)
+	s.Create(e2)
+	s.IncrementUse(e2.ID)
+	s.IncrementUse(e2.ID)
+
+	p := DefaultListParams()
+	p.Sort = "use_count"
+	entities, err := s.List(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if entities[0].Body != "high" {
+		t.Errorf("expected highest use first, got %q", entities[0].Body)
+	}
+}
+
+func TestList_Pagination(t *testing.T) {
+	s := testStore(t)
+	for i := 0; i < 10; i++ {
+		s.Create(&Entity{Body: "note", Glyph: GlyphNote})
+	}
+
+	p := DefaultListParams()
+	p.Limit = 3
+	p.Offset = 0
+	page1, err := s.List(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(page1) != 3 {
+		t.Fatalf("expected 3, got %d", len(page1))
+	}
+
+	p.Offset = 3
+	page2, err := s.List(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(page2) != 3 {
+		t.Fatalf("expected 3, got %d", len(page2))
+	}
+	if page1[0].ID == page2[0].ID {
+		t.Error("pages should not overlap")
+	}
+}
+
+func TestUpdate_Body(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "old", Glyph: GlyphNote}
+	s.Create(e)
+
+	time.Sleep(1100 * time.Millisecond)
+	newBody := "new"
+	if err := s.Update(e.ID, &EntityUpdate{Body: &newBody}); err != nil {
+		t.Fatal(err)
+	}
+
+	got, _ := s.Get(e.ID)
+	if got.Body != "new" {
+		t.Errorf("body not updated: %q", got.Body)
+	}
+	if !got.ModifiedAt.After(e.ModifiedAt) {
+		t.Error("modified_at not updated")
+	}
+}
+
+func TestUpdate_Tags(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "test", Glyph: GlyphNote, Tags: []string{"old"}}
+	s.Create(e)
+
+	newTags := []string{"new1", "new2"}
+	if err := s.Update(e.ID, &EntityUpdate{Tags: &newTags}); err != nil {
+		t.Fatal(err)
+	}
+
+	got, _ := s.Get(e.ID)
+	if len(got.Tags) != 2 {
+		t.Fatalf("expected 2 tags, got %d: %v", len(got.Tags), got.Tags)
+	}
+}
+
+func TestPromote_Success(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "trick", Glyph: GlyphNote}
+	s.Create(e)
+
+	if err := s.Promote(e.ID, CardSnippet, nil); err != nil {
+		t.Fatal(err)
+	}
+
+	got, _ := s.Get(e.ID)
+	if got.CardType == nil || *got.CardType != CardSnippet {
+		t.Errorf("expected snippet, got %v", got.CardType)
+	}
+}
+
+func TestPromote_AlreadyPromoted(t *testing.T) {
+	s := testStore(t)
+	ct := CardSnippet
+	e := &Entity{Body: "trick", Glyph: GlyphNote, CardType: &ct}
+	s.Create(e)
+
+	if err := s.Promote(e.ID, CardTemplate, nil); err != ErrAlreadyPromoted {
+		t.Errorf("expected ErrAlreadyPromoted, got %v", err)
+	}
+}
+
+func TestDemote_Success(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "trick", Glyph: GlyphNote}
+	s.Create(e)
+	s.Promote(e.ID, CardSnippet, nil)
+
+	if err := s.Demote(e.ID); err != nil {
+		t.Fatal(err)
+	}
+
+	got, _ := s.Get(e.ID)
+	if got.CardType != nil {
+		t.Errorf("expected nil card_type, got %v", got.CardType)
+	}
+	if got.UseCount != 0 {
+		t.Errorf("expected use_count reset to 0, got %d", got.UseCount)
+	}
+}
+
+func TestDemote_AlreadyFluid(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "trick", Glyph: GlyphNote}
+	s.Create(e)
+
+	if err := s.Demote(e.ID); err != ErrAlreadyFluid {
+		t.Errorf("expected ErrAlreadyFluid, got %v", err)
+	}
+}
+
+func TestSoftDelete_First(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "doomed", Glyph: GlyphNote}
+	s.Create(e)
+
+	result, err := s.SoftDelete(e.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if result != DeletedSoft {
+		t.Errorf("expected DeletedSoft, got %d", result)
+	}
+
+	got, _ := s.Get(e.ID)
+	if got.DeletedAt == nil {
+		t.Error("expected deleted_at to be set")
+	}
+}
+
+func TestSoftDelete_Second(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "doomed", Glyph: GlyphNote}
+	s.Create(e)
+
+	s.SoftDelete(e.ID)
+	result, err := s.SoftDelete(e.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if result != DeletedHard {
+		t.Errorf("expected DeletedHard, got %d", result)
+	}
+
+	_, err = s.Get(e.ID)
+	if err != ErrNotFound {
+		t.Errorf("expected ErrNotFound after hard delete, got %v", err)
+	}
+}
+
+func TestSoftDelete_NotFound(t *testing.T) {
+	s := testStore(t)
+	_, err := s.SoftDelete("01NONEXISTENT0000000000000")
+	if err != ErrNotFound {
+		t.Errorf("expected ErrNotFound, got %v", err)
+	}
+}
+
+func TestIncrementUse(t *testing.T) {
+	s := testStore(t)
+	ct := CardSnippet
+	e := &Entity{Body: "trick", Glyph: GlyphNote, CardType: &ct}
+	s.Create(e)
+
+	if err := s.IncrementUse(e.ID); err != nil {
+		t.Fatal(err)
+	}
+
+	got, _ := s.Get(e.ID)
+	if got.UseCount != 1 {
+		t.Errorf("expected use_count=1, got %d", got.UseCount)
+	}
+	if got.LastUsedAt == nil {
+		t.Error("expected last_used_at to be set")
+	}
+}
+
+func TestResolve_FullID(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "test", Glyph: GlyphNote}
+	s.Create(e)
+
+	got, err := s.Resolve(e.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != e.ID {
+		t.Errorf("expected %s, got %s", e.ID, got)
+	}
+}
+
+func TestResolve_Prefix(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "test", Glyph: GlyphNote}
+	s.Create(e)
+
+	got, err := s.Resolve(e.ID[:6])
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != e.ID {
+		t.Errorf("expected %s, got %s", e.ID, got)
+	}
+}
+
+func TestResolve_NotFound(t *testing.T) {
+	s := testStore(t)
+	_, err := s.Resolve("ZZZZZZZZZ")
+	if err != ErrNotFound {
+		t.Errorf("expected ErrNotFound, got %v", err)
+	}
+}
diff --git a/internal/db/tags.go b/internal/db/tags.go
new file mode 100644
index 0000000..29b2787
--- /dev/null
+++ b/internal/db/tags.go
@@ -0,0 +1,33 @@
+package db
+
+type TagCount struct {
+	Tag   string
+	Count int
+}
+
+func (s *Store) ListTags() ([]TagCount, error) {
+	rows, err := s.db.Query(`
+		SELECT t.tag, COUNT(*) as cnt
+		FROM entity_tags t
+		JOIN entities e ON t.entity_id = e.id
+		WHERE e.deleted_at IS NULL
+		GROUP BY t.tag
+		ORDER BY t.tag`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var tags []TagCount
+	for rows.Next() {
+		var tc TagCount
+		if err := rows.Scan(&tc.Tag, &tc.Count); err != nil {
+			return nil, err
+		}
+		tags = append(tags, tc)
+	}
+	if tags == nil {
+		tags = []TagCount{}
+	}
+	return tags, nil
+}
diff --git a/internal/db/tags_test.go b/internal/db/tags_test.go
new file mode 100644
index 0000000..9cd3dfe
--- /dev/null
+++ b/internal/db/tags_test.go
@@ -0,0 +1,63 @@
+package db
+
+import "testing"
+
+func TestListTags_Empty(t *testing.T) {
+	s := testStore(t)
+	tags, err := s.ListTags()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(tags) != 0 {
+		t.Errorf("expected 0 tags, got %d", len(tags))
+	}
+}
+
+func TestListTags_Counts(t *testing.T) {
+	s := testStore(t)
+	s.Create(&Entity{Body: "a", Glyph: GlyphNote, Tags: []string{"ops", "nginx"}})
+	s.Create(&Entity{Body: "b", Glyph: GlyphNote, Tags: []string{"ops"}})
+	s.Create(&Entity{Body: "c", Glyph: GlyphNote, Tags: []string{"home"}})
+
+	tags, err := s.ListTags()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(tags) != 3 {
+		t.Fatalf("expected 3 distinct tags, got %d", len(tags))
+	}
+
+	counts := map[string]int{}
+	for _, tc := range tags {
+		counts[tc.Tag] = tc.Count
+	}
+	if counts["ops"] != 2 {
+		t.Errorf("ops count: expected 2, got %d", counts["ops"])
+	}
+	if counts["nginx"] != 1 {
+		t.Errorf("nginx count: expected 1, got %d", counts["nginx"])
+	}
+	if counts["home"] != 1 {
+		t.Errorf("home count: expected 1, got %d", counts["home"])
+	}
+}
+
+func TestListTags_ExcludesDeleted(t *testing.T) {
+	s := testStore(t)
+	e := &Entity{Body: "doomed", Glyph: GlyphNote, Tags: []string{"gone"}}
+	s.Create(e)
+	s.SoftDelete(e.ID)
+
+	s.Create(&Entity{Body: "alive", Glyph: GlyphNote, Tags: []string{"here"}})
+
+	tags, err := s.ListTags()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(tags) != 1 {
+		t.Fatalf("expected 1 tag, got %d", len(tags))
+	}
+	if tags[0].Tag != "here" {
+		t.Errorf("expected 'here', got %q", tags[0].Tag)
+	}
+}
diff --git a/internal/ulid/ulid.go b/internal/ulid/ulid.go
new file mode 100644
index 0000000..9ec14d2
--- /dev/null
+++ b/internal/ulid/ulid.go
@@ -0,0 +1,20 @@
+package ulid
+
+import (
+	"crypto/rand"
+	"sync"
+
+	"github.com/oklog/ulid/v2"
+)
+
+var (
+	entropy     *ulid.MonotonicEntropy
+	entropyOnce sync.Once
+)
+
+func New() string {
+	entropyOnce.Do(func() {
+		entropy = ulid.Monotonic(rand.Reader, 0)
+	})
+	return ulid.MustNew(ulid.Now(), entropy).String()
+}
diff --git a/internal/ulid/ulid_test.go b/internal/ulid/ulid_test.go
new file mode 100644
index 0000000..04553b0
--- /dev/null
+++ b/internal/ulid/ulid_test.go
@@ -0,0 +1,28 @@
+package ulid
+
+import (
+	"testing"
+)
+
+func TestNew_ReturnsValidULID(t *testing.T) {
+	id := New()
+	if len(id) != 26 {
+		t.Errorf("expected 26 chars, got %d: %s", len(id), id)
+	}
+}
+
+func TestNew_Unique(t *testing.T) {
+	a := New()
+	b := New()
+	if a == b {
+		t.Errorf("two calls returned same ULID: %s", a)
+	}
+}
+
+func TestNew_Sortable(t *testing.T) {
+	a := New()
+	b := New()
+	if b < a {
+		t.Errorf("expected b >= a for sequential calls: a=%s b=%s", a, b)
+	}
+}