diff --git a/app/api/routes/api/config.py b/app/api/routes/api/config.py
index 0cc239b..bfffd2b 100644
--- a/app/api/routes/api/config.py
+++ b/app/api/routes/api/config.py
@@ -75,8 +75,11 @@ def put_config(
             detail="invalid config submission",
         ) from exc
 
-    # Re-read settings after save (save_config_updates clears the settings cache)
-    refreshed_settings = get_settings()
+    # Re-read settings after save (save_config_updates clears the settings cache).
+    # Use build_runtime_settings so the reconnect picks up DB-stored values, not
+    # just the bootstrap env (otherwise a broker configured via the UI is ignored).
+    from app.services.config_page import build_runtime_settings
+    refreshed_settings = build_runtime_settings(db, get_settings())
 
     # Reconnect MQTT client if any MQTT setting was updated.
     if mqtt_keys_submitted:
diff --git a/app/api/routes/api/expose.py b/app/api/routes/api/expose.py
index 9d048cf..084864a 100644
--- a/app/api/routes/api/expose.py
+++ b/app/api/routes/api/expose.py
@@ -23,6 +23,7 @@ from sqlalchemy.orm import Session
 from app.api.routes.api.deps import require_csrf, require_session
 from app.config import get_settings
 from app.dependencies import get_db
+from app.services.config_page import build_runtime_settings
 from app.integrations.expose import CatalogEntry, build_catalog
 from app.integrations.mqtt import mqtt_manager
 from app.models.expose import ExposedEntityToggle
@@ -48,9 +49,9 @@ router = APIRouter(prefix="/api", tags=["api-expose"])
 # ---------------------------------------------------------------------------
 
 
-def _get_mqtt_status() -> MqttStatusSchema:
-    """Build MQTT/Discovery status from live runtime state."""
-    settings = get_settings()
+def _get_mqtt_status(db: Session) -> MqttStatusSchema:
+    """Build MQTT/Discovery status from live runtime state (DB-merged settings)."""
+    settings = build_runtime_settings(db, get_settings())
     return MqttStatusSchema(
         mqtt_configured=mqtt_manager.is_configured(settings),
         mqtt_connected=mqtt_manager.is_connected,
@@ -87,7 +88,7 @@ def _build_response_data(
     """Return (catalog_entries, mqtt_status) for building GET / PUT responses."""
     catalog = build_catalog(session)
     catalog_schema = [_entry_to_schema(e) for e in catalog]
-    mqtt_status = _get_mqtt_status()
+    mqtt_status = _get_mqtt_status(session)
     return catalog_schema, mqtt_status
 
 
@@ -179,7 +180,7 @@ def post_expose_republish(
     Returns a status indicating whether the publish was attempted (or skipped
     because MQTT / discovery is not enabled / connected).
     """
-    settings = get_settings()
+    settings = build_runtime_settings(db, get_settings())
     if not (settings.mqtt_enabled and settings.ha_discovery_enabled and mqtt_manager.is_connected):
         return RepublishResponse(
             ok=False,
diff --git a/app/main.py b/app/main.py
index 43b4364..ffa919c 100644
--- a/app/main.py
+++ b/app/main.py
@@ -26,7 +26,7 @@ from app.api.routes.ticktick import router as ticktick_router
 from app.config import get_settings
 from app.integrations.mqtt import mqtt_manager
 from app.services.auth import AuthBootstrapError, initialize_auth_schema
-from app.services.config_page import seed_missing_config_from_bootstrap, sync_app_hostname_from_bootstrap
+from app.services.config_page import build_runtime_settings, seed_missing_config_from_bootstrap, sync_app_hostname_from_bootstrap
 from app.services.public_ip import check_public_ipv4_and_notify
 from app.services.modbus_poll import poll_all_enabled_devices, BASE_POLL_TICK_SECONDS
 from app.services.ha_discovery import publish_discovery, publish_states
@@ -74,10 +74,19 @@ def _run_scheduled_ha_state_publish() -> None:
     ``mqtt_manager.connect()`` would fire before the TCP handshake completes and
     be a no-op.  Instead, this periodic job picks it up within 60 seconds of the
     broker becoming available — retained payloads make repeated publishes harmless.
+
+    Additionally, if MQTT is configured in DB but the manager is not yet connected
+    (e.g. MQTT was enabled via UI after startup), this job attempts to connect so
+    the user does not need to restart the server.
     """
     session_local = get_session_local()
     session: Session = session_local()
     try:
+        runtime_settings = build_runtime_settings(session, get_settings())
+        # Reconnect if MQTT is configured (in DB) but not yet connected.
+        if mqtt_manager.is_configured(runtime_settings) and not mqtt_manager.is_connected:
+            logger.info("_run_scheduled_ha_state_publish: MQTT configured but not connected — attempting connect.")
+            mqtt_manager.connect(runtime_settings)
         publish_discovery(session)
         publish_states(session)
     except Exception:
@@ -140,10 +149,17 @@ async def lifespan(_: FastAPI):
     )
     scheduler.start()
 
-    # MQTT: connect if configured.
+    # MQTT: connect using DB-merged runtime settings so broker configured via UI
+    # is picked up on restart (not just from env/bootstrap settings).
     # Discovery will be published by the first run of _run_scheduled_ha_state_publish
     # (within 60 s of startup), after the async paho handshake completes.
-    mqtt_manager.connect(get_settings())
+    _startup_session_local = get_session_local()
+    _startup_session: Session = _startup_session_local()
+    try:
+        _startup_runtime_settings = build_runtime_settings(_startup_session, get_settings())
+    finally:
+        _startup_session.close()
+    mqtt_manager.connect(_startup_runtime_settings)
 
     yield
 
diff --git a/app/services/ha_discovery.py b/app/services/ha_discovery.py
index 25dbe39..b317a4b 100644
--- a/app/services/ha_discovery.py
+++ b/app/services/ha_discovery.py
@@ -35,6 +35,7 @@ from sqlalchemy.orm import Session
 
 from app.integrations.expose import ExposableEntity, build_catalog
 from app.integrations.mqtt import mqtt_manager
+from app.services.config_page import build_runtime_settings
 
 logger = logging.getLogger(__name__)
 
@@ -44,12 +45,6 @@ logger = logging.getLogger(__name__)
 # ---------------------------------------------------------------------------
 
 
-def _get_settings() -> Any:
-    """Return the current runtime settings (cached singleton)."""
-    from app.config import get_settings
-    return get_settings()
-
-
 def _should_publish(settings: Any) -> bool:
     """Return True only if MQTT and HA Discovery are both enabled and connected."""
     return bool(
@@ -180,7 +175,8 @@ def publish_discovery(session: Session) -> None:
     No-op if MQTT / discovery is not enabled or the client is not connected.
     All MQTT errors are caught internally — this function never raises.
     """
-    settings = _get_settings()
+    from app.config import get_settings
+    settings = build_runtime_settings(session, get_settings())
     if not _should_publish(settings):
         logger.debug("publish_discovery: skipped (MQTT/Discovery not enabled or not connected)")
         return
@@ -232,7 +228,8 @@ def publish_states(session: Session) -> None:
     No-op if MQTT / discovery is not enabled or the client is not connected.
     All errors are caught internally — this function never raises.
     """
-    settings = _get_settings()
+    from app.config import get_settings
+    settings = build_runtime_settings(session, get_settings())
     if not _should_publish(settings):
         logger.debug("publish_states: skipped (MQTT/Discovery not enabled or not connected)")
         return
@@ -320,7 +317,8 @@ def publish_device_state(session: Session, device: Any) -> None:
     No-op if MQTT / discovery is not enabled or the client is not connected.
     All errors are caught internally — never raises.
     """
-    settings = _get_settings()
+    from app.config import get_settings
+    settings = build_runtime_settings(session, get_settings())
     if not _should_publish(settings):
         return
 
@@ -386,7 +384,7 @@ def publish_device_state(session: Session, device: Any) -> None:
             )
 
 
-def publish_device_offline(device_uuid: str) -> None:
+def publish_device_offline(session: Session, device_uuid: str) -> None:
     """Publish an "offline" availability payload for *device_uuid*.
 
     Called by ``modbus_poll.poll_device`` when a poll fails, to immediately
@@ -395,7 +393,8 @@ def publish_device_offline(device_uuid: str) -> None:
     No-op if MQTT / discovery is not enabled or the client is not connected.
     Never raises.
     """
-    settings = _get_settings()
+    from app.config import get_settings
+    settings = build_runtime_settings(session, get_settings())
     if not _should_publish(settings):
         return
 
diff --git a/app/services/modbus_poll.py b/app/services/modbus_poll.py
index 0579041..1046531 100644
--- a/app/services/modbus_poll.py
+++ b/app/services/modbus_poll.py
@@ -132,7 +132,7 @@ def poll_device(session: Session, device: ModbusDevice) -> ModbusReading | None:
 
         # Best-effort: publish "offline" availability after failed poll.
         try:
-            publish_device_offline(device.uuid)
+            publish_device_offline(session, device.uuid)
         except Exception:  # noqa: BLE001
             logger.exception(
                 "poll_device: MQTT offline publish failed for device %r (id=%d)",
diff --git a/frontend/src/components/ExposeSettings.tsx b/frontend/src/components/ExposeSettings.tsx
index 6e769cf..aebf8e2 100644
--- a/frontend/src/components/ExposeSettings.tsx
+++ b/frontend/src/components/ExposeSettings.tsx
@@ -201,6 +201,7 @@ function RepublishButton() {
   return (
     <Stack gap="xs">
       <Button
+        type="button"
         variant="outline"
         size="sm"
         onClick={handleRepublish}
diff --git a/frontend/src/pages/ConfigPage.test.tsx b/frontend/src/pages/ConfigPage.test.tsx
index 7e67ca4..7c47287 100644
--- a/frontend/src/pages/ConfigPage.test.tsx
+++ b/frontend/src/pages/ConfigPage.test.tsx
@@ -399,6 +399,168 @@ describe('ConfigPage', () => {
   })
 })
 
+// ---------------------------------------------------------------------------
+// M5-fix2: MqttTestButton — Issue 1 (frontend)
+// ---------------------------------------------------------------------------
+
+describe('ConfigPage — MQTT test button', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    // Use the MOCK_CONFIG_WITH_CHECKBOX fixture which includes an MQTT section
+    mockGet.mockResolvedValue({ data: MOCK_CONFIG_WITH_CHECKBOX, response: { status: 200, ok: true } })
+  })
+
+  afterEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('renders MQTT test button when MQTT section is present', async () => {
+    renderConfig()
+
+    await waitFor(() => {
+      expect(screen.getByTestId('mqtt-test-button')).toBeInTheDocument()
+    })
+  })
+
+  it('does not render MQTT test button when no MQTT section present', async () => {
+    // Use a config fixture without MQTT section
+    mockGet.mockResolvedValueOnce({ data: MOCK_CONFIG, response: { status: 200, ok: true } })
+    renderConfig()
+
+    await waitFor(() => {
+      expect(screen.getByTestId('config-form')).toBeInTheDocument()
+    })
+
+    // No MQTT section in MOCK_CONFIG → button absent
+    // Wait a bit for any async renders
+    await waitFor(() => {
+      expect(screen.queryByTestId('mqtt-test-button')).not.toBeInTheDocument()
+    })
+  })
+
+  it('shows success alert after MQTT test succeeds', async () => {
+    mockPost.mockResolvedValueOnce({
+      data: { result: 'success', message: 'Test message published.' },
+      response: { status: 200, ok: true },
+    })
+
+    renderConfig()
+
+    await waitFor(() => {
+      expect(screen.getByTestId('mqtt-test-button')).toBeInTheDocument()
+    })
+
+    fireEvent.click(screen.getByTestId('mqtt-test-button'))
+
+    await waitFor(() => {
+      expect(screen.getByTestId('mqtt-result-success')).toBeInTheDocument()
+    })
+
+    expect(screen.queryByTestId('mqtt-result-config-error')).not.toBeInTheDocument()
+    expect(screen.queryByTestId('mqtt-result-failed')).not.toBeInTheDocument()
+  })
+
+  it('shows config-error alert when MQTT test returns config-error', async () => {
+    const { ApiError } = await import('../api/client')
+    mockPost.mockRejectedValueOnce(
+      new ApiError(400, { result: 'config-error', message: 'Broker host not configured.' }),
+    )
+
+    renderConfig()
+
+    await waitFor(() => {
+      expect(screen.getByTestId('mqtt-test-button')).toBeInTheDocument()
+    })
+
+    fireEvent.click(screen.getByTestId('mqtt-test-button'))
+
+    await waitFor(() => {
+      expect(screen.getByTestId('mqtt-result-config-error')).toBeInTheDocument()
+    })
+
+    expect(screen.queryByTestId('mqtt-result-success')).not.toBeInTheDocument()
+    expect(screen.queryByTestId('mqtt-result-failed')).not.toBeInTheDocument()
+  })
+
+  it('shows failed alert when MQTT test returns failed (502)', async () => {
+    const { ApiError } = await import('../api/client')
+    mockPost.mockRejectedValueOnce(
+      new ApiError(502, { result: 'failed', message: 'Connection refused.' }),
+    )
+
+    renderConfig()
+
+    await waitFor(() => {
+      expect(screen.getByTestId('mqtt-test-button')).toBeInTheDocument()
+    })
+
+    fireEvent.click(screen.getByTestId('mqtt-test-button'))
+
+    await waitFor(() => {
+      expect(screen.getByTestId('mqtt-result-failed')).toBeInTheDocument()
+    })
+
+    expect(screen.queryByTestId('mqtt-result-success')).not.toBeInTheDocument()
+    expect(screen.queryByTestId('mqtt-result-config-error')).not.toBeInTheDocument()
+  })
+
+  it('MQTT test button has type="button" and does not submit the config form', async () => {
+    renderConfig()
+
+    await waitFor(() => {
+      expect(screen.getByTestId('mqtt-test-button')).toBeInTheDocument()
+    })
+
+    const mqttBtn = screen.getByTestId('mqtt-test-button')
+    // The rendered button element should have type="button"
+    expect(mqttBtn.getAttribute('type')).toBe('button')
+  })
+})
+
+// ---------------------------------------------------------------------------
+// M5-fix2: ExposeSettings in config accordion — Issue 3 (frontend)
+// ---------------------------------------------------------------------------
+
+describe('ConfigPage — ExposeSettings in main accordion', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    mockGet.mockResolvedValue({ data: MOCK_CONFIG, response: { status: 200, ok: true } })
+  })
+
+  afterEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('renders Home Assistant Expose accordion item inside the config accordion', async () => {
+    renderConfig()
+
+    await waitFor(() => {
+      expect(screen.getByTestId('config-accordion')).toBeInTheDocument()
+    })
+
+    // The Expose accordion item should be inside the main config-accordion
+    const configAccordion = screen.getByTestId('config-accordion')
+    const exposeControl = screen.getByTestId('accordion-control-expose')
+    expect(configAccordion.contains(exposeControl)).toBe(true)
+  })
+
+  it('Expose accordion item appears before the Save button in DOM order', async () => {
+    renderConfig()
+
+    await waitFor(() => {
+      expect(screen.getByTestId('accordion-control-expose')).toBeInTheDocument()
+    })
+
+    const exposeControl = screen.getByTestId('accordion-control-expose')
+    const saveButton = screen.getByTestId('config-save-button')
+
+    // compareDocumentPosition: if expose comes before save, position & Node.DOCUMENT_POSITION_FOLLOWING === true
+    const position = exposeControl.compareDocumentPosition(saveButton)
+    // DOCUMENT_POSITION_FOLLOWING = 4 means saveButton comes after exposeControl
+    expect(position & Node.DOCUMENT_POSITION_FOLLOWING).toBeTruthy()
+  })
+})
+
 // ---------------------------------------------------------------------------
 // Area B: checkbox (Switch) rendering and value round-trip
 // ---------------------------------------------------------------------------
diff --git a/frontend/src/pages/ConfigPage.tsx b/frontend/src/pages/ConfigPage.tsx
index fdb83d9..66dd5dd 100644
--- a/frontend/src/pages/ConfigPage.tsx
+++ b/frontend/src/pages/ConfigPage.tsx
@@ -57,6 +57,13 @@ type SmtpResult =
   | { kind: 'failed'; message: string }
   | null
 
+/** MQTT test result tri-state. */
+type MqttResult =
+  | { kind: 'success'; message: string }
+  | { kind: 'config-error'; message: string }
+  | { kind: 'failed'; message: string }
+  | null
+
 // ---------------------------------------------------------------------------
 // Hook: load config
 // ---------------------------------------------------------------------------
@@ -263,6 +270,75 @@ function SmtpTestButton({ smtpResult, setSmtpResult }: SmtpTestButtonProps) {
   )
 }
 
+// ---------------------------------------------------------------------------
+// MqttTestButton — sends POST /api/config/mqtt/test and displays tri-state result
+// ---------------------------------------------------------------------------
+
+interface MqttTestButtonProps {
+  mqttResult: MqttResult
+  setMqttResult: (r: MqttResult) => void
+}
+
+function MqttTestButton({ mqttResult, setMqttResult }: MqttTestButtonProps) {
+  const [testing, setTesting] = useState(false)
+
+  async function handleTest() {
+    setMqttResult(null)
+    setTesting(true)
+    try {
+      const res = await apiClient.POST('/api/config/mqtt/test')
+      if (res.data) {
+        setMqttResult({ kind: 'success', message: res.data.message })
+      }
+    } catch (err) {
+      if (err instanceof ApiError) {
+        const body = err.body as { result?: string; message?: string } | null
+        const result = body?.result
+        const message = body?.message ?? 'Unknown error'
+        if (result === 'config-error') {
+          setMqttResult({ kind: 'config-error', message })
+        } else {
+          setMqttResult({ kind: 'failed', message })
+        }
+      } else {
+        setMqttResult({ kind: 'failed', message: 'Unexpected error sending test message.' })
+      }
+    } finally {
+      setTesting(false)
+    }
+  }
+
+  return (
+    <Stack gap="xs">
+      <Button
+        type="button"
+        variant="outline"
+        onClick={handleTest}
+        loading={testing}
+        data-testid="mqtt-test-button"
+      >
+        Send Test Message
+      </Button>
+
+      {mqttResult?.kind === 'success' && (
+        <Alert color="green" data-testid="mqtt-result-success">
+          MQTT test message sent successfully. {mqttResult.message}
+        </Alert>
+      )}
+      {mqttResult?.kind === 'config-error' && (
+        <Alert color="orange" data-testid="mqtt-result-config-error">
+          MQTT configuration error — check your MQTT settings. {mqttResult.message}
+        </Alert>
+      )}
+      {mqttResult?.kind === 'failed' && (
+        <Alert color="red" data-testid="mqtt-result-failed">
+          MQTT test failed. {mqttResult.message}
+        </Alert>
+      )}
+    </Stack>
+  )
+}
+
 // ---------------------------------------------------------------------------
 // ConfigPage — main component
 // ---------------------------------------------------------------------------
@@ -295,6 +371,9 @@ export function ConfigPage() {
   // SMTP test tri-state
   const [smtpResult, setSmtpResult] = useState<SmtpResult>(null)
 
+  // MQTT test tri-state
+  const [mqttResult, setMqttResult] = useState<MqttResult>(null)
+
   function handleChange(envName: string, value: string) {
     setLocalValues((prev) => ({ ...prev, [envName]: value }))
     setSaveStatus(null)
@@ -350,6 +429,9 @@ export function ConfigPage() {
     s.name.toLowerCase().includes('smtp') || s.name.toLowerCase().includes('email'),
   )
 
+  // Detect if there is an MQTT section (to show the MQTT test button).
+  const hasMqttSection = data.sections.some((s) => s.name.toLowerCase() === 'mqtt')
+
   // Default: open the first section so users immediately see content.
   const defaultAccordionValue = data.sections[0]?.name ?? null
 
@@ -387,6 +469,18 @@ export function ConfigPage() {
                 </Accordion.Panel>
               </Accordion.Item>
             ))}
+
+            {/* M5-fix2: Home Assistant Expose panel merged into the config accordion,
+                above Save/Test buttons.  All interactive elements inside ExposeSettings
+                use type="button" so they do not trigger the config form submit. */}
+            <Accordion.Item value="expose" data-testid="expose-accordion-item">
+              <Accordion.Control data-testid="accordion-control-expose">
+                <Text fw={500}>Home Assistant Expose</Text>
+              </Accordion.Control>
+              <Accordion.Panel>
+                <ExposeSettings />
+              </Accordion.Panel>
+            </Accordion.Item>
           </Accordion>
 
           <Divider />
@@ -411,9 +505,14 @@ export function ConfigPage() {
               Save Configuration
             </Button>
 
-            {hasSmtpSection && (
-              <SmtpTestButton smtpResult={smtpResult} setSmtpResult={setSmtpResult} />
-            )}
+            <Group gap="sm" wrap="wrap">
+              {hasSmtpSection && (
+                <SmtpTestButton smtpResult={smtpResult} setSmtpResult={setSmtpResult} />
+              )}
+              {hasMqttSection && (
+                <MqttTestButton mqttResult={mqttResult} setMqttResult={setMqttResult} />
+              )}
+            </Group>
           </Group>
         </Stack>
       </form>
@@ -426,20 +525,6 @@ export function ConfigPage() {
         </Stack>
       )}
 
-      {/* M5-T12: Home Assistant Expose — entity toggle panel as an Accordion.Item
-          below the config form. Kept outside <form> because it manages its own
-          mutations (PUT /api/expose, POST /api/expose/republish). */}
-      <Accordion variant="separated" radius="md" mt="xl" data-testid="expose-accordion">
-        <Accordion.Item value="expose">
-          <Accordion.Control data-testid="accordion-control-expose">
-            <Text fw={500}>Home Assistant Expose</Text>
-          </Accordion.Control>
-          <Accordion.Panel>
-            <ExposeSettings />
-          </Accordion.Panel>
-        </Accordion.Item>
-      </Accordion>
-
       {/* TOTP two-factor auth management */}
       <Stack mt="xl">
         <TotpSettings />
diff --git a/tests/test_api_config.py b/tests/test_api_config.py
index 556a448..673e017 100644
--- a/tests/test_api_config.py
+++ b/tests/test_api_config.py
@@ -3,7 +3,7 @@
 from __future__ import annotations
 
 import sqlite3
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 from fastapi.testclient import TestClient
 
@@ -656,3 +656,90 @@ def test_put_config_bool_field_roundtrip_true_false(
     finally:
         conn.close()
     assert rows.get("MQTT_ENABLED") == "false"
+
+
+# ---------------------------------------------------------------------------
+# M5-fix2: DB-config → runtime settings (Issue 2 regression assertions)
+# ---------------------------------------------------------------------------
+
+def test_put_config_mqtt_reconnect_uses_db_merged_settings(
+    client: TestClient, test_database_urls
+) -> None:
+    """PUT /api/config with MQTT keys must reconnect with DB-merged settings,
+    not bootstrap-only settings.  Asserts that mqtt_manager.reconnect receives
+    settings where mqtt_enabled=True and mqtt_broker_host matches the submitted value.
+    """
+    _login(client)
+
+    target_host = "mqtt.example.com"
+    payload = _full_config_payload({
+        "MQTT_ENABLED": "true",
+        "MQTT_BROKER_HOST": target_host,
+    })
+
+    mock_mgr = MagicMock()
+    mock_mgr.is_configured.return_value = True
+
+    with patch("app.api.routes.api.config.mqtt_manager", mock_mgr):
+        resp = client.put(
+            "/api/config",
+            json={"updates": payload},
+            headers={"X-CSRF-Token": "token"},
+        )
+
+    assert resp.status_code == 200
+
+    # reconnect must have been called once
+    assert mock_mgr.reconnect.call_count == 1, (
+        f"Expected mqtt_manager.reconnect called once, got {mock_mgr.reconnect.call_count}"
+    )
+    reconnect_settings = mock_mgr.reconnect.call_args[0][0]
+    assert reconnect_settings.mqtt_enabled is True, (
+        f"reconnect settings.mqtt_enabled must be True, got {reconnect_settings.mqtt_enabled!r}"
+    )
+    assert reconnect_settings.mqtt_broker_host == target_host, (
+        f"reconnect settings.mqtt_broker_host must be {target_host!r}, "
+        f"got {reconnect_settings.mqtt_broker_host!r}"
+    )
+
+
+def test_post_mqtt_test_uses_db_broker_host(
+    client: TestClient, test_database_urls
+) -> None:
+    """POST /api/config/mqtt/test must use the DB-stored broker host, not env/bootstrap."""
+    _login(client)
+
+    db_host = "broker.db-configured.local"
+
+    # First write the MQTT config to DB via PUT /api/config
+    payload_save = _full_config_payload({
+        "MQTT_ENABLED": "true",
+        "MQTT_BROKER_HOST": db_host,
+    })
+    with patch("app.api.routes.api.config.mqtt_manager"):
+        save_resp = client.put(
+            "/api/config",
+            json={"updates": payload_save},
+            headers={"X-CSRF-Token": "token"},
+        )
+    assert save_resp.status_code == 200
+
+    # Now POST /api/config/mqtt/test — capture the host that _run_mqtt_test uses.
+    captured_host: list[str] = []
+
+    def _fake_run_mqtt_test(settings):
+        captured_host.append(settings.mqtt_broker_host)
+        # simulate success by just returning
+        return
+
+    with patch("app.api.routes.api.config._run_mqtt_test", side_effect=_fake_run_mqtt_test):
+        resp = client.post(
+            "/api/config/mqtt/test",
+            headers={"X-CSRF-Token": "token"},
+        )
+
+    assert resp.status_code == 200
+    assert len(captured_host) == 1, "Expected _run_mqtt_test to be called once"
+    assert captured_host[0] == db_host, (
+        f"Expected mqtt test to use DB host {db_host!r}, got {captured_host[0]!r}"
+    )
diff --git a/tests/test_api_expose.py b/tests/test_api_expose.py
index 578fbda..f4689cc 100644
--- a/tests/test_api_expose.py
+++ b/tests/test_api_expose.py
@@ -367,7 +367,7 @@ class TestPostRepublish:
         mock_settings.ha_discovery_enabled = True
         mock_settings.ha_discovery_prefix = "homeassistant"
 
-        with patch("app.api.routes.api.expose.get_settings", return_value=mock_settings):
+        with patch("app.api.routes.api.expose.build_runtime_settings", return_value=mock_settings):
             with patch("app.api.routes.api.expose.mqtt_manager") as mock_mqtt:
                 mock_mqtt.is_configured.return_value = True
                 mock_mqtt.is_connected = True
@@ -406,7 +406,7 @@ class TestPostRepublish:
         mock_settings.mqtt_enabled = True
         mock_settings.ha_discovery_enabled = True
 
-        with patch("app.api.routes.api.expose.get_settings", return_value=mock_settings):
+        with patch("app.api.routes.api.expose.build_runtime_settings", return_value=mock_settings):
             with patch("app.api.routes.api.expose.mqtt_manager") as mock_mqtt:
                 mock_mqtt.is_connected = False
                 resp = client.post(
@@ -475,3 +475,48 @@ class TestCatalogGrouping:
         components = {e["entity"]["component"] for e in catalog}
         assert "binary_sensor" in components
         assert "sensor" in components
+
+
+# ---------------------------------------------------------------------------
+# M5-fix2: DB-config → mqtt_status runtime assertion (Issue 2)
+# ---------------------------------------------------------------------------
+
+
+class TestMqttStatusReadsFromDB:
+    def test_get_expose_mqtt_configured_reflects_db_value(self, expose_client):
+        """GET /api/expose must return mqtt_configured=True when MQTT is enabled+configured
+        in the DB (app_config), even if the bootstrap env says disabled.
+
+        This verifies that _get_mqtt_status uses build_runtime_settings (DB-merged)
+        rather than bare get_settings() (bootstrap-only).
+        """
+        client, engine = expose_client
+        _login(client)
+
+        # Write MQTT_ENABLED=true and MQTT_BROKER_HOST into app_config directly.
+        # The lifespan seeds all config keys on startup, so we must UPDATE existing rows.
+        from datetime import UTC, datetime
+        from app.models.config import AppConfigEntry
+
+        now = datetime.now(UTC)
+        with Session(engine) as session:
+            for key, value in [("MQTT_ENABLED", "true"), ("MQTT_BROKER_HOST", "broker.test.local")]:
+                row = session.query(AppConfigEntry).filter(AppConfigEntry.key == key).first()
+                if row is None:
+                    session.add(AppConfigEntry(key=key, value=value, updated_at=now))
+                else:
+                    row.value = value
+                    row.updated_at = now
+            session.commit()
+
+        # The bootstrap env does NOT have MQTT enabled (default False in Settings).
+        # But GET /api/expose should still report mqtt_configured=True because it reads DB.
+        with patch("app.integrations.expose._REGISTRY", []):
+            resp = client.get("/api/expose")
+
+        assert resp.status_code == 200
+        mqtt_status = resp.json()["mqtt_status"]
+        assert mqtt_status["mqtt_configured"] is True, (
+            f"Expected mqtt_configured=True from DB settings, "
+            f"got {mqtt_status['mqtt_configured']!r}. Full status: {mqtt_status}"
+        )
diff --git a/tests/test_ha_discovery.py b/tests/test_ha_discovery.py
index 0a1f83c..27bdbbd 100644
--- a/tests/test_ha_discovery.py
+++ b/tests/test_ha_discovery.py
@@ -340,7 +340,7 @@ def test_publish_discovery_sends_retained_for_enabled_entity(disco_db) -> None:
     mock_mgr.publish.side_effect = _capture
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
     ):
         from app.services.ha_discovery import publish_discovery
@@ -383,7 +383,7 @@ def test_publish_discovery_sends_empty_payload_for_disabled_entity(disco_db) ->
     mock_mgr.publish.side_effect = _capture
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
     ):
         from app.services.ha_discovery import publish_discovery
@@ -425,7 +425,7 @@ def test_publish_discovery_enabled_vs_disabled_payload(disco_db) -> None:
     mock_mgr.publish.side_effect = _capture
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
     ):
         from app.services.ha_discovery import publish_discovery
@@ -501,7 +501,7 @@ def test_publish_states_calls_value_getter_for_enabled_sensor() -> None:
     mock_catalog = [CatalogEntry(entity=mock_entity, enabled=True)]
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
         patch("app.services.ha_discovery.build_catalog", return_value=mock_catalog),
     ):
@@ -549,7 +549,7 @@ def test_publish_states_skips_disabled_entities() -> None:
     mock_catalog = [CatalogEntry(entity=mock_entity, enabled=False)]
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
         patch("app.services.ha_discovery.build_catalog", return_value=mock_catalog),
     ):
@@ -614,7 +614,7 @@ def test_publish_device_state_pushes_availability_and_state() -> None:
     mock_device.last_poll_ok = True
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
         patch("app.services.ha_discovery.build_catalog", return_value=mock_catalog),
     ):
@@ -658,7 +658,7 @@ def test_publish_device_state_publishes_offline_on_failed_poll() -> None:
     mock_device.last_poll_ok = False
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
         patch("app.services.ha_discovery.build_catalog", return_value=[]),
     ):
@@ -695,12 +695,13 @@ def test_publish_device_offline_publishes_offline_topic() -> None:
     mock_mgr.publish.side_effect = _capture
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
     ):
         from app.services.ha_discovery import publish_device_offline
+        from unittest.mock import MagicMock as _MagicMock
 
-        publish_device_offline(uuid_val)
+        publish_device_offline(_MagicMock(), uuid_val)
 
     assert len(published) == 1
     topic, payload = published[0]
@@ -713,13 +714,55 @@ def test_publish_device_offline_publishes_offline_topic() -> None:
 # ---------------------------------------------------------------------------
 
 
+def test_should_publish_true_when_db_enabled_bootstrap_disabled(disco_db) -> None:
+    """_should_publish must use DB-merged settings: if DB has mqtt_enabled=True and
+    ha_discovery_enabled=True (bootstrap has both False), publish should proceed.
+
+    This is the core regression test for Issue 2: bare get_settings() returns bootstrap
+    (False); build_runtime_settings returns DB-merged (True).
+    """
+    from app.services.config_page import build_runtime_settings
+    from app.services.ha_discovery import _should_publish
+    from app.models.config import AppConfigEntry
+    from datetime import UTC, datetime
+
+    now = datetime.now(UTC)
+
+    # Write MQTT + discovery enabled into app_config (DB level)
+    with Session(disco_db) as session:
+        session.add(AppConfigEntry(key="MQTT_ENABLED", value="true", updated_at=now))
+        session.add(AppConfigEntry(key="MQTT_BROKER_HOST", value="broker.test", updated_at=now))
+        session.add(AppConfigEntry(key="HA_DISCOVERY_ENABLED", value="true", updated_at=now))
+        session.commit()
+
+    # Bootstrap has mqtt_enabled=False and ha_discovery_enabled=False (env defaults)
+    from app.config import Settings
+    bootstrap = Settings(_env_file=None, mqtt_enabled=False, ha_discovery_enabled=False,
+                         app_database_url=str(disco_db.url))
+
+    with Session(disco_db) as session:
+        runtime = build_runtime_settings(session, bootstrap)
+
+    # Simulate a connected broker for the _should_publish check
+    mock_mgr_connected = MagicMock()
+    mock_mgr_connected.is_connected = True
+
+    with patch("app.services.ha_discovery.mqtt_manager", mock_mgr_connected):
+        result = _should_publish(runtime)
+
+    assert result is True, (
+        "_should_publish must return True when DB has mqtt_enabled=True + ha_discovery_enabled=True, "
+        "even if bootstrap Settings has both False"
+    )
+
+
 def test_publish_discovery_noop_when_mqtt_disabled() -> None:
     """publish_discovery must be a no-op when mqtt_enabled=False."""
     settings = _make_settings(mqtt_enabled=False, ha_discovery_enabled=True)
     mock_mgr = _make_mock_manager(is_connected=False)
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
     ):
         from app.services.ha_discovery import publish_discovery
@@ -739,7 +782,7 @@ def test_publish_states_noop_when_not_connected() -> None:
     mock_mgr = _make_mock_manager(is_connected=False)
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
     ):
         from app.services.ha_discovery import publish_states
@@ -758,7 +801,7 @@ def test_publish_discovery_noop_when_ha_discovery_disabled() -> None:
     mock_mgr = _make_mock_manager(is_connected=True)
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
     ):
         from app.services.ha_discovery import publish_discovery
@@ -781,7 +824,7 @@ def test_publish_device_state_noop_when_mqtt_disabled() -> None:
     mock_device.last_poll_ok = True
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
     ):
         from app.services.ha_discovery import publish_device_state
@@ -800,12 +843,13 @@ def test_publish_device_offline_noop_when_mqtt_disabled() -> None:
     mock_mgr = _make_mock_manager(is_connected=False)
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
     ):
         from app.services.ha_discovery import publish_device_offline
+        from unittest.mock import MagicMock as _MagicMock
 
-        publish_device_offline("some-uuid")  # must not raise
+        publish_device_offline(_MagicMock(), "some-uuid")  # must not raise
 
     mock_mgr.publish.assert_not_called()
 
@@ -984,7 +1028,7 @@ def test_publish_discovery_uses_retain_true_for_enabled_entity() -> None:
     catalog = [CatalogEntry(entity=entity, enabled=True)]
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
         patch("app.services.ha_discovery.build_catalog", return_value=catalog),
     ):
@@ -1085,7 +1129,7 @@ def test_real_provider_value_getter_returns_latest_reading_value(disco_db) -> No
     mock_device.last_poll_ok = True
 
     with (
-        patch("app.services.ha_discovery._get_settings", return_value=settings),
+        patch("app.services.ha_discovery.build_runtime_settings", return_value=settings),
         patch("app.services.ha_discovery.mqtt_manager", mock_mgr),
         # NOTE: build_catalog is NOT mocked — we use the real modbus provider.
     ):