diff --git a/internal/adapters/store/actions.go b/internal/adapters/store/actions.go
new file mode 100644
index 0000000..ead5e5d
--- /dev/null
+++ b/internal/adapters/store/actions.go
@@ -0,0 +1,137 @@
+package store
+
+import (
+	"context"
+	"fmt"
+)
+
+// allowedActions is the closed set of action verbs persisted in summary_actions.
+// It mirrors the CHECK constraint in migration 002; validating in Go returns a
+// clear error before the round-trip rather than a raw constraint violation.
+var allowedActions = map[string]bool{
+	"watched": true,
+	"skipped": true,
+	"saved":   true,
+}
+
+// oppositeAction maps each mutually-exclusive action to the one it clears:
+// watching a video clears a prior skip and vice versa (ui-spec.md §4). "saved"
+// is independent and has no opposite, so it is absent here.
+var oppositeAction = map[string]string{
+	"watched": "skipped",
+	"skipped": "watched",
+}
+
+// validateAction rejects any action outside the allowed set.
+func validateAction(action string) error {
+	if !allowedActions[action] {
+		return fmt.Errorf("store: invalid action %q (want watched|skipped|saved)", action)
+	}
+	return nil
+}
+
+// SetAction records that the user took action on a video. It is idempotent:
+// re-setting an already-active action refreshes acted_at, never duplicates.
+// Mutual exclusion is enforced atomically in one tx — setting "watched" clears
+// "skipped" and vice versa; "saved" coexists with either.
+func (s *Store) SetAction(ctx context.Context, userID, videoID, action string) error {
+	if err := validateAction(action); err != nil {
+		return err
+	}
+
+	tx, err := s.pool.Begin(ctx)
+	if err != nil {
+		return fmt.Errorf("store: begin set action: %w", err)
+	}
+	defer tx.Rollback(ctx) //nolint:errcheck // no-op after Commit
+
+	if opposite, ok := oppositeAction[action]; ok {
+		if _, err := tx.Exec(ctx,
+			`DELETE FROM summary_actions
+			  WHERE user_id = $1 AND video_id = $2 AND action = $3`,
+			userID, videoID, opposite); err != nil {
+			return fmt.Errorf("store: clear opposite action: %w", err)
+		}
+	}
+
+	if _, err := tx.Exec(ctx,
+		`INSERT INTO summary_actions (user_id, video_id, action)
+		 VALUES ($1, $2, $3)
+		 ON CONFLICT (user_id, video_id, action) DO UPDATE SET acted_at = NOW()`,
+		userID, videoID, action); err != nil {
+		return fmt.Errorf("store: set action: %w", err)
+	}
+
+	if err := tx.Commit(ctx); err != nil {
+		return fmt.Errorf("store: commit set action: %w", err)
+	}
+	return nil
+}
+
+// ClearAction removes an action for (user, video). Clearing an action that is
+// not set is a no-op (no error) — toggling off an inactive button is harmless.
+func (s *Store) ClearAction(ctx context.Context, userID, videoID, action string) error {
+	if err := validateAction(action); err != nil {
+		return err
+	}
+	if _, err := s.pool.Exec(ctx,
+		`DELETE FROM summary_actions
+		  WHERE user_id = $1 AND video_id = $2 AND action = $3`,
+		userID, videoID, action); err != nil {
+		return fmt.Errorf("store: clear action: %w", err)
+	}
+	return nil
+}
+
+// ActionsFor returns the active actions per video for the given user, keyed by
+// video_id, for the list view. Videos with no actions are simply absent from the
+// map. Scoped by user_id: one user never sees another's actions.
+func (s *Store) ActionsFor(ctx context.Context, userID string, videoIDs []string) (map[string][]string, error) {
+	out := make(map[string][]string)
+	if len(videoIDs) == 0 {
+		return out, nil
+	}
+	rows, err := s.pool.Query(ctx,
+		`SELECT video_id, action FROM summary_actions
+		  WHERE user_id = $1 AND video_id = ANY($2)
+		  ORDER BY video_id, action`,
+		userID, videoIDs)
+	if err != nil {
+		return nil, fmt.Errorf("store: actions for: %w", err)
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var videoID, action string
+		if err := rows.Scan(&videoID, &action); err != nil {
+			return nil, fmt.Errorf("store: scan action: %w", err)
+		}
+		out[videoID] = append(out[videoID], action)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, fmt.Errorf("store: iterate actions: %w", err)
+	}
+	return out, nil
+}
+
+// attachActions enriches read rows with their current actions in a single query.
+// Additive: rows with no actions keep a nil Actions slice. Used by the read
+// views (reads.go) to surface action state without a cross-type SQL join
+// (summaries.video_id is UUID, summary_actions.video_id is TEXT).
+func (s *Store) attachActions(ctx context.Context, userID string, rows []SummaryRow) error {
+	if len(rows) == 0 {
+		return nil
+	}
+	ids := make([]string, len(rows))
+	for i := range rows {
+		ids[i] = rows[i].VideoID
+	}
+	actions, err := s.ActionsFor(ctx, userID, ids)
+	if err != nil {
+		return err
+	}
+	for i := range rows {
+		rows[i].Actions = actions[rows[i].VideoID]
+	}
+	return nil
+}
diff --git a/internal/adapters/store/actions_test.go b/internal/adapters/store/actions_test.go
new file mode 100644
index 0000000..de92009
--- /dev/null
+++ b/internal/adapters/store/actions_test.go
@@ -0,0 +1,161 @@
+package store_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestSetActionThenActionsFor(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	resetDB(t, rawPool(t))
+
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "watched"))
+
+	got, err := s.ActionsFor(ctx, userA, []string{videoX})
+	require.NoError(t, err)
+	require.Equal(t, map[string][]string{videoX: {"watched"}}, got)
+}
+
+func TestSetActionWatchedSkippedMutuallyExclusive(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	resetDB(t, rawPool(t))
+
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "watched"))
+	// Switching to skipped must clear watched (and vice versa).
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "skipped"))
+
+	got, err := s.ActionsFor(ctx, userA, []string{videoX})
+	require.NoError(t, err)
+	require.Equal(t, map[string][]string{videoX: {"skipped"}}, got, "skipped replaces watched")
+
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "watched"))
+	got, err = s.ActionsFor(ctx, userA, []string{videoX})
+	require.NoError(t, err)
+	require.Equal(t, map[string][]string{videoX: {"watched"}}, got, "watched replaces skipped")
+}
+
+func TestSetActionSavedCoexists(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	resetDB(t, rawPool(t))
+
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "watched"))
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "saved"))
+
+	got, err := s.ActionsFor(ctx, userA, []string{videoX})
+	require.NoError(t, err)
+	// ActionsFor orders by action: saved, watched.
+	require.Equal(t, map[string][]string{videoX: {"saved", "watched"}}, got,
+		"saved is independent and coexists with watched")
+}
+
+func TestClearAction(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	resetDB(t, rawPool(t))
+
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "saved"))
+	require.NoError(t, s.ClearAction(ctx, userA, videoX, "saved"))
+
+	got, err := s.ActionsFor(ctx, userA, []string{videoX})
+	require.NoError(t, err)
+	require.Empty(t, got, "cleared action no longer active")
+
+	// Clearing an action that was never set is a harmless no-op.
+	require.NoError(t, s.ClearAction(ctx, userA, videoX, "watched"))
+}
+
+func TestSetActionIsIdempotent(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	p := rawPool(t)
+	resetDB(t, p)
+
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "watched"))
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "watched"))
+
+	var count int
+	require.NoError(t, p.QueryRow(ctx,
+		`SELECT count(*) FROM summary_actions
+		  WHERE user_id = $1 AND video_id = $2 AND action = 'watched'`,
+		userA, videoX).Scan(&count))
+	require.Equal(t, 1, count, "re-setting must refresh, not duplicate")
+}
+
+func TestSetActionRejectsInvalid(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	resetDB(t, rawPool(t))
+
+	require.Error(t, s.SetAction(ctx, userA, videoX, "bookmarked"))
+	require.Error(t, s.ClearAction(ctx, userA, videoX, ""))
+}
+
+func TestActionsAreUserScoped(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	resetDB(t, rawPool(t))
+
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "watched"))
+
+	got, err := s.ActionsFor(ctx, userB, []string{videoX})
+	require.NoError(t, err)
+	require.Empty(t, got, "user B must not see user A's actions")
+}
+
+func TestActionsForMultipleVideos(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	resetDB(t, rawPool(t))
+
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "watched"))
+	require.NoError(t, s.SetAction(ctx, userA, videoY, "saved"))
+
+	got, err := s.ActionsFor(ctx, userA, []string{videoX, videoY})
+	require.NoError(t, err)
+	require.Equal(t, map[string][]string{
+		videoX: {"watched"},
+		videoY: {"saved"},
+	}, got)
+
+	// Empty input -> empty (non-nil) map, no query.
+	empty, err := s.ActionsFor(ctx, userA, nil)
+	require.NoError(t, err)
+	require.Empty(t, empty)
+}
+
+func TestReadsSurfaceActions(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	resetDB(t, rawPool(t))
+
+	require.NoError(t, s.Deliver(ctx, summary(userA, videoX, "body")))
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "watched"))
+	require.NoError(t, s.SetAction(ctx, userA, videoX, "saved"))
+
+	list, err := s.ListSummaries(ctx, userA, 50)
+	require.NoError(t, err)
+	require.Len(t, list, 1)
+	require.Equal(t, []string{"saved", "watched"}, list[0].Actions, "list view carries current actions")
+
+	detail, err := s.GetSummaryByVideo(ctx, userA, videoX)
+	require.NoError(t, err)
+	require.Equal(t, []string{"saved", "watched"}, detail.Actions, "detail view carries current actions")
+}
+
+func TestReadsSurfaceNoActionsAsNil(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	resetDB(t, rawPool(t))
+
+	require.NoError(t, s.Deliver(ctx, summary(userA, videoX, "body")))
+
+	list, err := s.ListSummaries(ctx, userA, 50)
+	require.NoError(t, err)
+	require.Len(t, list, 1)
+	require.Nil(t, list[0].Actions, "no actions -> nil slice")
+}
diff --git a/internal/adapters/store/migrations/002_summary_actions.down.sql b/internal/adapters/store/migrations/002_summary_actions.down.sql
new file mode 100644
index 0000000..33d5215
--- /dev/null
+++ b/internal/adapters/store/migrations/002_summary_actions.down.sql
@@ -0,0 +1 @@
+DROP TABLE summary_actions;
diff --git a/internal/adapters/store/migrations/002_summary_actions.up.sql b/internal/adapters/store/migrations/002_summary_actions.up.sql
new file mode 100644
index 0000000..dcbd955
--- /dev/null
+++ b/internal/adapters/store/migrations/002_summary_actions.up.sql
@@ -0,0 +1,19 @@
+-- summary_actions records the maintainer's act on a summary (watch/skip/save) —
+-- the column that makes the Stage-0 headline metric ("acts on >=1 summary")
+-- queryable (ui-spec.md §5, ADR-011). Per-user isolation: every row carries
+-- user_id (dormant authz at Stage 0, single user). video_id is TEXT and not
+-- FK-constrained, mirroring summaries' standalone (user_id, video_id) key.
+
+CREATE TABLE summary_actions (
+    id        UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id   UUID NOT NULL,
+    video_id  TEXT NOT NULL,
+    action    TEXT NOT NULL,
+    acted_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    CONSTRAINT summary_actions_action_check
+        CHECK (action IN ('watched', 'skipped', 'saved')),
+    CONSTRAINT summary_actions_user_video_action_unique
+        UNIQUE (user_id, video_id, action)
+);
+
+CREATE INDEX idx_summary_actions_user_video ON summary_actions(user_id, video_id);
diff --git a/internal/adapters/store/reads.go b/internal/adapters/store/reads.go
index d488996..8233d1a 100644
--- a/internal/adapters/store/reads.go
+++ b/internal/adapters/store/reads.go
@@ -37,6 +37,7 @@ type SummaryRow struct {
 	AIModel      string
 	FallbackUsed bool
 	CreatedAt    time.Time
+	Actions      []string // current active actions for this video; nil when none
 }
 
 // selectSummary is the shared projection for both reads. videos is LEFT JOINed
@@ -87,6 +88,9 @@ func (s *Store) ListSummaries(ctx context.Context, userID string, limit int) ([]
 	if err := rows.Err(); err != nil {
 		return nil, fmt.Errorf("store: iterate summaries: %w", err)
 	}
+	if err := s.attachActions(ctx, userID, out); err != nil {
+		return nil, err
+	}
 	return out, nil
 }
 
@@ -113,7 +117,11 @@ func (s *Store) GetSummaryByVideo(ctx context.Context, userID, videoID string) (
 	if err != nil {
 		return nil, err
 	}
-	return &row, nil
+	holder := []SummaryRow{row}
+	if err := s.attachActions(ctx, userID, holder); err != nil {
+		return nil, err
+	}
+	return &holder[0], nil
 }
 
 // scanSummaryRow reads one row in the selectSummary column order. published_at is
diff --git a/internal/adapters/store/store_test.go b/internal/adapters/store/store_test.go
index cac0e81..623d3ed 100644
--- a/internal/adapters/store/store_test.go
+++ b/internal/adapters/store/store_test.go
@@ -74,7 +74,7 @@ func rawPool(t *testing.T) *pgxpool.Pool {
 func resetDB(t *testing.T, p *pgxpool.Pool) {
 	t.Helper()
 	_, err := p.Exec(context.Background(),
-		`TRUNCATE sink_deliveries, summaries, transcripts, videos, users CASCADE`)
+		`TRUNCATE summary_actions, sink_deliveries, summaries, transcripts, videos, users CASCADE`)
 	require.NoError(t, err)
 }