Nuki is not a KNX device — but via the Bridge local HTTP API and Home Assistant running on local hardware, it becomes fully controllable from any KNX group address in your installation. No cloud dependency, no subscription, and remarkably stable for a consumer product. Here is the complete integration path.

Nuki product selection

The **Nuki Smart Lock 4.0 Pro** (€229) includes built-in Wi-Fi and thread — no Bridge required, direct local API access. This is the recommended choice for new installations. The **Smart Lock 3.0** (older generation) requires the **Nuki Bridge** (€109) for local API access — it communicates via Bluetooth to the lock and exposes an HTTP API on the local network. The **Nuki Opener** (€109) integrates with apartment building intercoms (Ritto, TCS, Urmet, Siedle and others) — ring suppression, automatic door opener on arrival, and "Ring to Open" mode. For apartment buildings with KNX access control, the Opener plus Bridge is the standard solution.

Bridge local API setup

First, enable developer mode in the Nuki smartphone app: Settings → Manage devices → select Bridge → Enable API. The Bridge IP address and API token appear in this screen. Test connectivity with a simple HTTP request: GET http://[BRIDGE-IP]:8080/list?token=[TOKEN] — this returns a JSON list of paired locks with their current state (locked/unlocked/unlatched). The local API supports lock, unlock, unlatch, lock'n'go, and status query. No internet required after initial pairing.

Home Assistant configuration

Install the Nuki integration from HACS or via the official HA integration page (Settings → Integrations → Add → Nuki). Enter the Bridge IP and token. HA creates a lock entity (lock.front_door) with states locked/unlocked and services lock.lock, lock.unlock, lock.open. Enable the webhook callback in the Nuki integration settings — this gives instant state updates (sub-second) when the lock changes state physically, without polling.

KNX to Nuki automations

Five automation examples in Home Assistant YAML: (1) Departure lock — KNX group address 4/0/5 telegram TRUE ("Goodbye" scene) → lock.lock service on lock.front_door. (2) Arrival unlock — KNX presence sensor (motion at door, DPT 1.001) TRUE + time condition (07:00–22:00) → lock.unlock. (3) Guest code on schedule — HA time trigger (check-in time from calendar) → Nuki keypad code activation via Nuki API. (4) Alarm trigger lock — Ajax alarm armed_away event → lock.lock + lock state KNX feedback GA 5/0/10 = TRUE. (5) Door state to KNX display — lock entity state change → knx.send to GA 5/0/10 (DPT 1.001) — shown on KNX room display (Gira G1, MDT Glastaster II) as locked/unlocked indicator.

Ajax alarm integration

The most-used combination in premium EU residential: Nuki lock + Ajax alarm on a single "Goodbye" KNX scene. KNX scene 5 (GA 4/0/0, value 5) → HA automation → simultaneously: lock.lock on Nuki, Ajax arm_away via Ajax HA integration, KNX shutter actuator all blinds closed, KNX HVAC setback. One pushbutton press handles departure completely. For return: Ajax disarm (motion at entry zone) + Nuki unlock from outside → HA automation sends KNX welcome scene (lights on, heating to comfort, blinds auto-mode).

Suitability for professional installations

The Nuki Bridge HTTP API has been stable across firmware versions since 2019. For professional installations, run Home Assistant on dedicated local hardware (Intel NUC, Raspberry Pi 4, or Proxmox VM) with UPS power — not on a shared home server. Document the Bridge IP as static DHCP reservation in the router. The lock cylinder replacement (Nuki replaces your existing euro cylinder) is compatible with most EU doors — verify the cylinder length before ordering. For projects requiring formal access control audit logs, use the Nuki Web API (cloud) as a secondary logging channel alongside the local API primary control path.