Force MQTT pushall re-sync after a report gap (fixes #14)

The printer publishes partial deltas most of the time; the accumulator
merges each one onto whatever state it already has. When the printer
powers off, our cloud MQTT connection stays up (it's a persistent
session to Bambu's broker, not a socket to the printer), so nothing
signals the outage. When the printer reconnects and resumes its normal
partial updates, those deltas get merged onto the stale pre-outage
state — fields the delta doesn't mention (e.g. nozzle_temp) stay frozen
at their old values. Sending any command happens to trigger a full
report from the printer, which is why toggling the light "fixes" it.

Track the time of the last message per BambuPrinter instance. When a
new message arrives after a gap longer than
BAMBU_RUN_MQTT_RESYNC_GAP_SECONDS (default 90s), request a pushall
before processing it, forcing a complete state refresh instead of
trusting the partial delta to overwrite stale fields.

bambu_run/conf.py

@@ -81,5 +81,12 @@ class _Settings:
     def CLOUD_SYNC_DAYS(self):
         return get_setting("BAMBU_RUN_CLOUD_SYNC_DAYS", 30)
 
+    # Seconds of silence on the MQTT report topic that, once broken by a new
+    # message, is treated as "the printer was probably offline" and triggers
+    # a pushall re-sync instead of trusting the partial delta to fill in stale
+    # fields left over from before the gap.
+    @property
+    def MQTT_RESYNC_GAP_SECONDS(self):
+        return get_setting("BAMBU_RUN_MQTT_RESYNC_GAP_SECONDS", 90)
 
 app_settings = _Settings()

bambu_run/mqtt_client.py

@@ -21,6 +21,7 @@ import os
 import platform
 import sys
 import select
+import time
 from contextlib import contextmanager
 from dataclasses import dataclass, field
 from datetime import datetime
@@ -809,6 +810,7 @@ class BambuPrinter:
         self._accumulator = PrinterStateAccumulator()
         self._connected = False
         self._devices: List[Dict[str, Any]] = []
+        self._last_message_at: Optional[float] = None
 
     def _get_fresh_token(self, verification_code_timeout: int = 300) -> str:
         """Get a fresh token using credentials."""
@@ -914,6 +916,30 @@ class BambuPrinter:
         """Internal MQTT message handler"""
         if not data:
             return
+
+        # The printer publishes partial deltas most of the time; the accumulator
+        # merges them onto whatever it already has. If the printer went offline
+        # (power cycle) and just reconnected, the first delta after the gap would
+        # otherwise be merged onto stale pre-outage state, leaving fields like
+        # nozzle_temp frozen at their last value until some unrelated full report
+        # happens to refresh them. Detect the gap and force a full pushall so the
+        # accumulator gets a clean, complete state instead.
+        now = time.time()
+        if (
+            self._last_message_at is not None
+            and now - self._last_message_at > app_settings.MQTT_RESYNC_GAP_SECONDS
+            and self._mqtt is not None
+        ):
+            try:
+                self._mqtt.request_full_status()
+                logger.info(
+                    "MQTT report gap of %.0fs detected for %s; requested full status re-sync",
+                    now - self._last_message_at, device_id,
+                )
+            except Exception as e:
+                logger.warning("Full status re-sync request failed (non-fatal): %s", e)
+        self._last_message_at = now
+
         state = self._accumulator.update(data)
         if self._on_update:
             self._on_update(state)