Radarr, Sonarr, and their sibling apps watch RSS feeds for new releases but never go back for what your library is still missing, and Houndarr fills that gap by asking them to search in small, polite batches. It reads the wanted lists of every connected Radarr, Sonarr, Lidarr, Readarr, and Whisparr instance and sends a few search commands per cycle, so a big backlog drains over days instead of arriving as one Search All Missing burst. Each instance has its own batch size, sleep interval, hourly cap, per-item cooldown, and post-release grace period, plus an optional download-queue limit, allowed search windows such as 09:00-23:00, and tag filters that include or exclude items. Three independent passes run per instance: missing items, cutoff-unmet items below your quality profile, and upgrades for files that already meet cutoff, with the last two off until you enable them. Sonarr, Lidarr, and Readarr can search by season, artist, or author, and search order is random or oldest-first. The dashboard shows library health, recent hunts, hourly budgets, and a cooldown schedule per instance, with Run Now buttons for on-demand cycles. The Logs page records every search and skip with its reason in a filterable audit trail that copies as TSV. A key-gated widget endpoint feeds Homepage dashboards, and built-in login or reverse-proxy authentication protects the interface. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.