test

        // Setup local block store — file-backed if path configured, otherwise memory

        if (!cfg_.store_path.empty()) {

            std::cerr << "Cluster: using file_block_store at " << cfg_.store_path << std::endl;

            store_ = std::make_shared<paritypp::file_block_store>(cfg_.store_path);

            store_ = std::make_shared<paritypp::file_block_store>(cfg_.store_path, 0);

        } else {

            std::cerr << "Cluster: using memory_block_store (no PATH configured)" << std::endl;

            store_ = std::make_shared<paritypp::memory_block_store>();

        if (running_) return;

        running_ = true;

        // Vacuum file store at startup to reclaim space from old session data

        // that was previously written to blocks.bin instead of session_store_

        // Purge old session blocks from file store and vacuum to reclaim space.

        // Previous versions stored session shards in blocks.bin; identify them

        // by checking if block 0 of each group starts with the SESB magic

        // (after the 8-byte parity length header).

        if (store_) {

            auto all_groups = store_->list_groups();

            int purged = 0;

            for (uint64_t gid : all_groups) {

                std::vector<uint8_t> block0;

                if (store_->fetch(gid, 0, block0) && block0.size() >= 12) {

                    // The parity client prepends an 8-byte length header.

                    // After that, session data starts with 'SESB' magic.

                    if (block0[8] == 'S' && block0[9] == 'E' &&

                        block0[10] == 'S' && block0[11] == 'B') {

                        store_->remove_group(gid);

                        ++purged;

                    }

                }

            }

            if (purged > 0) {

                std::cerr << "Cluster: purged " << purged

                          << " old session groups from file store" << std::endl;

            }

            if (store_->vacuum()) {

                std::cerr << "Cluster: startup vacuum completed" << std::endl;

            }