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summary: The MQTT broker every reading passes through: clients, topics, where its passwords live
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# MQTT broker

Mosquitto 2.0 on the small server; every reading passes through it.

- Fed by: `gateway.md`. Read by: the time-series database (`timeseries-db.md`).
- Access: one account per client; the passwords live in the password manager, entry "Greenhouse / MQTT", never here.
- Restart and log locations: `runbook.md`.

## Topics (since 2026-03-06)
- `greenhouse/valves/#` for `irrigation-valve.md`; `greenhouse/check` for `checks.md`.