Add a pause that holds an agent after its current step

internal/store/migrations/104-add-session-paused.sql

@@ -0,0 +1 @@
+ALTER TABLE agent_sessions ADD COLUMN paused INTEGER NOT NULL DEFAULT 0;

internal/store/store.go

@@ -1376,6 +1376,32 @@ func (s *Store) SessionsWithSubagents(ctx context.Context) ([]api.AgentSession,
 	return s.querySessions(ctx, `SELECT `+sessionColumns+` FROM agent_sessions WHERE subagents > 0`)
 }
 
+func (s *Store) PausedSessions(ctx context.Context) ([]api.AgentSession, error) {
+	return s.querySessions(ctx, `SELECT `+sessionColumns+` FROM agent_sessions WHERE paused AND state != ?`, string(api.AgentSessionStateCompleted))
+}
+
+func (s *Store) SetSessionPaused(ctx context.Context, id string, paused bool, actor string) error {
+	return s.write(ctx, func(tx *sql.Tx, emit emitFunc) error {
+		taskID := ""
+		projectID := ""
+		owner := ""
+		err := tx.QueryRowContext(ctx, `
+			SELECT coalesce(t.id, ''), coalesce(t.project_id, ''), s.owner FROM agent_sessions s LEFT JOIN tasks t ON t.id = s.task_id WHERE s.id = ?
+		`, id).Scan(&taskID, &projectID, &owner)
+		if errors.Is(err, sql.ErrNoRows) {
+			return ErrNotFound
+		}
+		if err != nil {
+			return err
+		}
+		_, err = tx.ExecContext(ctx, `UPDATE agent_sessions SET paused = ? WHERE id = ?`, paused, id)
+		if err != nil {
+			return err
+		}
+		return emit(sessionEvent("session.paused", projectID, taskID, owner, id, actor, map[string]any{"paused": paused}))
+	})
+}
+
 func (s *Store) SetSubagents(ctx context.Context, id string, n int, actor string) error {
 	return s.write(ctx, func(tx *sql.Tx, emit emitFunc) error {
 		taskID := ""
@@ -1701,7 +1727,7 @@ const backgroundExpr = `(audit != '' OR EXISTS (SELECT 1 FROM tasks r WHERE r.id
 		AND (kind != 'task.discard_suggested'
 			OR (kind = 'task.discard_suggested' AND NOT EXISTS (SELECT 1 FROM tasks r JOIN workflow_definitions d ON d.id = r.workflow_definition_id WHERE r.id IN (tasks.id, tasks.parent_task_id) AND d.auto_discard))))`
 
-const sessionColumns = `id, coalesce(task_id, ''), owner, vendor, model, vendor_session_id, state, role, member, created_by, created_at, forked_from, forked_at, subagents`
+const sessionColumns = `id, coalesce(task_id, ''), owner, vendor, model, vendor_session_id, state, role, member, created_by, created_at, forked_from, forked_at, subagents, paused`
 
 type scanner interface {
 	Scan(dest ...any) error
@@ -1809,7 +1835,7 @@ func scanSession(row scanner) (api.AgentSession, error) {
 	createdAt := ""
 	forkedFrom := ""
 	forkedAt := ""
-	err := row.Scan(&sess.Id, &sess.TaskId, &sess.Owner, &vendor, &sess.Model, &sess.VendorSessionId, &state, &role, &sess.Member, &sess.CreatedBy, &createdAt, &forkedFrom, &forkedAt, &sess.Subagents)
+	err := row.Scan(&sess.Id, &sess.TaskId, &sess.Owner, &vendor, &sess.Model, &sess.VendorSessionId, &state, &role, &sess.Member, &sess.CreatedBy, &createdAt, &forkedFrom, &forkedAt, &sess.Subagents, &sess.Paused)
 	if err != nil {
 		return sess, err
 	}