hvac: native MQTT driver for MHI aircon (replaces Modbus for control/status)

The Intesis MHI gateway was switched from Modbus TCP to native MQTT mode
(2026-08-13), publishing retained per-signal JSON status to
hvac/mhi/IU<nn>/status/<signal> and subscribing to commands at
hvac/mhi/IU<nn>/cmd/<signal>Cmd. This adds an MQTT ingest + command path
alongside the now-dormant Modbus driver, under a new mhi_mqtt device type.

Backend:
- lib/mqtt.js: subscribe hvac/mhi/+/status/+, parse JSON payloads, auto-
  register each unit as an unassigned mhi_mqtt zone_devices row and cache
  live status (power/mode/setpoint/room temp/fan/health). Add
  publishMhiCommand() for on/off/mode/setpoint/fan/vanes writes (QoS 1,
  retain off — a retained command would replay stale on gateway reconnect).
  Numeric mode/fan enums map index-for-index to the frontend label arrays.
- routes/override.js: mhi-status/mhi-control branch on device_type —
  mhi_mqtt serves from the push-populated cache and publishes commands;
  mhi_modbus keeps its synchronous register path unchanged.
- routes/devices.js: discover() note for mhi_mqtt (units self-register).
- No DB migration: existing status columns cover it.

Credentials: getCredentials() now prefers env-injected creds
(MQTT_BROKER_HOST/USERNAME/PASSWORD) over the settings fetch — the broker
hashes each dynsec client password show-once, so it can't be re-served from
settings at runtime. Compose passes the new env through.

Frontend: add mhi_mqtt to DeviceType/labels/implemented list, render
MhiControlPanel and count it as an AC device type.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/src/routes/devices.js

@@ -26,6 +26,8 @@ const DRIVERS = {
 const NOT_YET_IMPLEMENTED = ['midea', 'daikin']
 const MHI_MODBUS_NOTE = "MHI aircon units aren't found via Discover — configure a gateway and import its register " +
   'map under Devices -> Gateways, then assign units to zones there.'
+const MHI_MQTT_NOTE = 'MHI aircon units on native MQTT self-register as they publish status — they appear ' +
+  'automatically in the device list. Assign each discovered unit to a zone; no Discover or gateway import needed.'
 
 export async function deviceRoutes(app, opts) {
   const UPLOADS_DIR = opts.uploadsDir
@@ -53,6 +55,10 @@ export async function deviceRoutes(app, opts) {
       return reply.status(200).send({ ok: true, devices: [], note: MHI_MODBUS_NOTE })
     }
 
+    if (device_type === 'mhi_mqtt') {
+      return reply.status(200).send({ ok: true, devices: [], note: MHI_MQTT_NOTE })
+    }
+
     if (NOT_YET_IMPLEMENTED.includes(device_type)) {
       return reply.status(200).send({
         ok: true, devices: [],

backend/src/routes/override.js

@@ -1,6 +1,6 @@
 import { requireAuth, requireCap } from '../auth.js'
 import { pool, logActivity } from '../db.js'
-import { batchSetZoneTemperature } from '../lib/mqtt.js'
+import { batchSetZoneTemperature, publishMhiCommand } from '../lib/mqtt.js'
 import * as mhiDriver from '../lib/drivers/mhi-modbus.js'
 
 // Manual force-temperature — the equivalent of the old integration's
@@ -40,40 +40,86 @@ export async function overrideRoutes(app) {
     return { ok: successful > 0, successful, total: devices.length, auto_mode: false }
   })
 
-  // GET /api/devices/:id/mhi-status — live Modbus read (onOff/mode/setpoint/
-  // fanSpeed/roomTemp/errorCode/etc) for one assigned MHI aircon unit.
+  // GET /api/devices/:id/mhi-status — live status for one assigned MHI aircon unit.
+  // mhi_mqtt: served from the push-populated status cache (mqtt.js keeps it fresh
+  // from the gateway's retained topics). mhi_modbus: live Modbus round-trip read.
   app.get('/api/devices/:id/mhi-status', { preHandler: requireCap('view') }, async (req, reply) => {
     const { rows } = await pool.query(
-      `SELECT * FROM zone_devices WHERE id = $1 AND device_type = 'mhi_modbus'`,
+      `SELECT * FROM zone_devices WHERE id = $1 AND device_type IN ('mhi_modbus', 'mhi_mqtt')`,
       [req.params.id]
     )
     if (!rows.length) return reply.status(404).send({ error: 'MHI device not found' })
-    const status = await mhiDriver.getStatus(rows[0].external_ref)
+    const device = rows[0]
+
+    if (device.device_type === 'mhi_mqtt') {
+      return {
+        external_ref: device.external_ref,
+        onOff: device.power_state ?? undefined,
+        mode: device.current_mode ?? undefined,
+        setpoint: device.current_target_temp != null ? Number(device.current_target_temp) : undefined,
+        fanSpeed: device.fan_speed ?? undefined,
+        roomTemp: device.current_room_temp != null ? Number(device.current_room_temp) : undefined,
+      }
+    }
+
+    const status = await mhiDriver.getStatus(device.external_ref)
     if (!status || status.error) {
       return reply.status(502).send({ error: status?.error || 'Failed to read device status' })
     }
     return status
   })
 
-  // POST /api/devices/:id/mhi-control — manual aircon control only (no
-  // scheduler wiring). Body: { onOff?, mode?, tempC?, fanSpeed? } — only the
-  // fields present are written, via the mhi-modbus driver's setTarget().
+  // POST /api/devices/:id/mhi-control — manual aircon control only (no scheduler
+  // wiring). Body: { onOff?, mode?, tempC?, fanSpeed? } — only the fields present
+  // are written. mhi_mqtt: publish command topics (fire-and-forget, QoS 1); the
+  // gateway echoes the new state back on its status topics within a second, which
+  // mqtt.js re-caches — we also optimistically update the cache for instant UI.
+  // mhi_modbus: synchronous register write via the driver.
   app.post('/api/devices/:id/mhi-control', { preHandler: requireCap('control') }, async (req, reply) => {
     const { rows } = await pool.query(
-      `SELECT * FROM zone_devices WHERE id = $1 AND device_type = 'mhi_modbus'`,
+      `SELECT * FROM zone_devices WHERE id = $1 AND device_type IN ('mhi_modbus', 'mhi_mqtt')`,
       [req.params.id]
     )
     if (!rows.length) return reply.status(404).send({ error: 'MHI device not found' })
     const device = rows[0]
     const { onOff, mode, tempC, fanSpeed } = req.body || {}
 
-    const ok = await mhiDriver.setTarget(device.external_ref, { onOff, mode, tempC, fanSpeed })
-
-    if (ok && tempC !== undefined && tempC !== null) {
-      await pool.query(
-        `UPDATE zone_devices SET current_target_temp = $1, target_origin = 'manual', updated_at = NOW() WHERE id = $2`,
-        [tempC, device.id]
-      )
+    let ok
+    if (device.device_type === 'mhi_mqtt') {
+      try {
+        publishMhiCommand(device.external_ref, { onOff, mode, tempC, fanSpeed })
+        ok = true
+      } catch (err) {
+        ok = false
+        req.log.warn(`MHI command publish failed for ${device.external_ref}: ${err.message}`)
+      }
+      if (ok) {
+        // Optimistic cache update so the dashboard reflects the command immediately.
+        await pool.query(
+          `UPDATE zone_devices SET
+             power_state         = COALESCE($1, power_state),
+             current_mode        = COALESCE($2, current_mode),
+             current_target_temp = COALESCE($3, current_target_temp),
+             fan_speed           = COALESCE($4, fan_speed),
+             updated_at = NOW()
+           WHERE id = $5`,
+          [
+            onOff === undefined || onOff === null ? null : (onOff ? 'on' : 'off'),
+            mode ?? null,
+            tempC ?? null,
+            fanSpeed ?? null,
+            device.id,
+          ]
+        )
+      }
+    } else {
+      ok = await mhiDriver.setTarget(device.external_ref, { onOff, mode, tempC, fanSpeed })
+      if (ok && tempC !== undefined && tempC !== null) {
+        await pool.query(
+          `UPDATE zone_devices SET current_target_temp = $1, target_origin = 'manual', updated_at = NOW() WHERE id = $2`,
+          [tempC, device.id]
+        )
+      }
     }
 
     await logActivity(device.zone_id, 'device_command', {