test

                auto data = pclient_->retrieve(gid);

                if (data.empty()) {

                    std::cerr << "[SCRUB] group " << gid

                              << " — retrieve returned empty, skipping" << std::endl;

                              << " — retrieve returned empty, skipping (NOT removing)" << std::endl;

                    result.groups_failed++;

                    continue;

                }

                // remove + store ensures correct block placement on all nodes

                // Validate retrieved data before removing the existing blocks.

                // A manifest must have at least a valid AuthHeader + magic + count.

                if (data.size() < sizeof(AuthHeader) + sizeof(uint32_t) + sizeof(uint32_t)) {

                    std::cerr << "[SCRUB] group " << gid

                              << " — retrieved data too small (" << data.size()

                              << " bytes), skipping (NOT removing)" << std::endl;

                    result.groups_failed++;

                    continue;

                }

                // Verify AuthHeader is present

                AuthHeader head;

                std::memcpy(&head, data.data(), sizeof(AuthHeader));

                if (head.start != 0xFE) {

                    std::cerr << "[SCRUB] group " << gid

                              << " — retrieved data has invalid header marker"

                              << ", skipping (NOT removing)" << std::endl;

                    result.groups_failed++;

                    continue;

                }

                // Data is valid — safe to remove and re-store for correct placement

                pclient_->remove(gid);

                pclient_->store(gid, data.data(), data.size());

                result.groups_repaired++;