fix: reuse one MQTT TLS session for TUI dashboard and monitor

AGENTS.md

@@ -30,6 +30,7 @@ Core printer interaction is `BambuPrinter` in `bambu_cli/printer.py`. Agents and
 - Secret-bearing files are tightened to `0600` automatically on POSIX: config.json on load, and the `access_code_file` when `load_access_code()` reads it. Windows relies on NTFS ACLs (see [SECURITY.md](SECURITY.md)).
 - Network operations support `timeout` and `retries` through `printer.send_command()` and `printer.status()`.
 - `printer.status()` returns a **complete** state snapshot, never a partial MQTT delta: the printer streams incremental updates on its report topic and only answers `pushall` with the whole state, so report messages are merged and the wait continues until `gcode_state`, `mc_percent`, `bed_temper`, and `nozzle_temper` are all present. If only deltas arrive it raises `PrinterStatusIncomplete` (exit `6`) instead of returning a partial — so `plate --json status` never emits a `printer` object missing `gcode_state`. Pass `require_complete=False` for liveness probes that only need to know MQTT works (this is what `doctor` and `print --dry-run` do).
+- A long-lived process can call `printer.hold_mqtt()` so `status` / `send_command` / `get_version` reuse one TLS session. The TUI does this: dashboard and monitor refreshes must not open a new connection every few seconds. One-shot CLI commands still connect and tear down. Always pair with `release_mqtt()` so the paho loop thread does not leak (CI runs with `-W error::ResourceWarning`).
 
 ### Module layout
 

CHANGELOG.md

@@ -7,6 +7,10 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); version
 
 ### Changed
 
+- The TUI dashboard and monitor keep one MQTT TLS session for the process
+  instead of opening a new connection on every refresh. One-shot CLI commands
+  still connect and tear down.
+
 - `--json` emitters construct `bambu_cli.contracts` objects. `status --json`
   no longer flattens firmware fields onto the envelope; they stay under
   `printer`. Errors go through `ErrorEnvelope`; `job` success/failure through

bambu_cli/printer.py

@@ -4,6 +4,7 @@
 import os
 import secrets
 import ssl
+import threading
 import time
 from typing import Any, Optional
 
@@ -47,6 +48,38 @@ def __init__(
         self.mqtt_timeout = 5.0
         self.ftps_timeout = 15.0
 
+        # Long-lived MQTT session. None for one-shot CLI (connect + teardown).
+        # The TUI calls hold_mqtt() so dashboard/monitor refreshes reuse one
+        # TLS connection instead of opening a new one every 10s.
+        self._mqtt_session: Any = None
+        self._mqtt_hold_lock = threading.Lock()
+
+    def hold_mqtt(self, *, client_factory=None) -> None:
+        """Keep one MQTT client for subsequent status/send_command/get_version.
+
+        No-op in simulation mode (nothing opens a socket). Safe to call twice.
+        Pair with ``release_mqtt()`` so the loop thread and socket do not leak.
+        """
+        if self.simulation_mode:
+            return
+        with self._mqtt_hold_lock:
+            if self._mqtt_session is None:
+                from bambu_cli.protocols.mqtt_session import MqttSession
+
+                self._mqtt_session = MqttSession(self, client_factory=client_factory)
+
+    def release_mqtt(self) -> None:
+        """Disconnect a held MQTT session. Safe to call twice."""
+        with self._mqtt_hold_lock:
+            session = self._mqtt_session
+            self._mqtt_session = None
+        if session is not None:
+            session.close()
+
+    @property
+    def mqtt_held(self) -> bool:
+        return self._mqtt_session is not None
+
     def send_command(self, payload: str, timeout: Optional[float] = None, retries: int = 2) -> bool:
         """Send a JSON command payload via MQTT."""
         return mqtt_protocol.send_command(self, payload, timeout=timeout, retries=retries)

bambu_cli/protocols/mqtt.py

@@ -1,8 +1,9 @@
 """MQTT transport facade.
 
-Implementations live in ``mqtt_tls``, ``mqtt_cmd``, ``mqtt_print``, and
-``mqtt_monitor``. This module re-exports the public names so existing imports
-and test patches on ``bambu_cli.protocols.mqtt`` keep working.
+Implementations live in ``mqtt_tls``, ``mqtt_cmd``, ``mqtt_print``,
+``mqtt_monitor``, and ``mqtt_session``. This module re-exports the public
+names so existing imports and test patches on ``bambu_cli.protocols.mqtt``
+keep working.
 """
 
 from __future__ import annotations
@@ -19,6 +20,7 @@
 )
 from bambu_cli.protocols.mqtt_monitor import _status_event, monitor_status
 from bambu_cli.protocols.mqtt_print import _printer_error_hex, execute_print_command
+from bambu_cli.protocols.mqtt_session import MqttSession
 from bambu_cli.protocols.mqtt_tls import (
     PinningSSLContext,
     _mqtt_connect,
@@ -39,6 +41,7 @@
     "_printer_error_hex",
     "_require_mqtt",
     "_status_event",
+    "MqttSession",
     "create_mqtt_client",
     "execute_print_command",
     "get_status",

bambu_cli/protocols/mqtt_cmd.py

@@ -59,6 +59,10 @@ def send_command(
         logger.info(f"🤖 [SIM] Sending command: {payload}")
         return True
 
+    session = getattr(printer, "_mqtt_session", None)
+    if session is not None:
+        return session.send_command(payload, timeout, retries)
+
     for attempt in range(retries + 1):
         client = _factory(printer)
         client.user_data_set({})
@@ -164,6 +168,10 @@ def get_status(printer, timeout=None, retries=2, *, require_complete=True):
             },
         }
 
+    session = getattr(printer, "_mqtt_session", None)
+    if session is not None:
+        return session.get_status(timeout, retries, require_complete=require_complete)
+
     merged: dict = {}
     merged_lock = threading.Lock()
     _factory = _client_factory(None)
@@ -265,6 +273,10 @@ def get_version(printer, timeout=5, retries=1):
     if printer.simulation_mode:
         return [{"name": "ota", "sw_ver": "01.00.00.00", "hw_ver": "P1P-SIM"}]
 
+    session = getattr(printer, "_mqtt_session", None)
+    if session is not None:
+        return session.get_version(timeout, retries)
+
     _factory = _client_factory(None)
     _sleep_fn = _sleep(None)