Stop a drying cycle reporting itself finished a minute in (#2759)

Starting the dryer on an AMS 2 Pro holding two PETG and two PLA spools
and picking PLA showed "PLA @ 45°C" for about a minute and then switched
to "PETG @ 65°C" for the remaining twelve hours.

Bambu never echoes back which filament or temperature a cycle is
running, so the badge reads the target cached when the command went out,
and that cache had been dropped. Between accepting the command and
settling its countdown the firmware publishes one update with the
remaining time at zero while the unit is still in its Checking phase --
the reporter's log has 720, then 0, then 719, and four seconds later the
same unit's info hex decodes to dry_status 2, Drying. The falling-edge
detector read that zero as the cycle ending. Losing the cached target
left the badge to guess from the first loaded slot, which was PETG, and
its RFID-recommended 65°C. The same false ending fired
on_drying_complete, so anyone with smart-plug auto-off-after-drying
switched on had power scheduled to cut one minute into a twelve-hour
dry; the reporter had it off, which is the only reason this reads as a
cosmetic bug.

A remaining time of zero now ends a cycle only when the unit is not also
reporting an active phase. dry_status comes from the same info hex
already parsed a few lines above, so this costs nothing to check.
Stopping and Error are deliberately not treated as active -- those
should end it -- and a unit that reports no phase at all still ends its
cycles, so the gate can only ever suppress on positive evidence that the
cycle is live. A suppressed edge leaves the remembered dry_time alone,
exactly as the #1462 absent-value skip does, so the push that really
ends the cycle still sees a non-zero previous.

The fallback guess is tightened to match. On a mixed unit the first tray
is evidence of nothing, and naming a temperature the cycle is not using
is worse than naming none, so it now answers only when every loaded
spool is the same filament and otherwise leaves the badge showing the
countdown alone. Both the websocket and REST status builders carried
their own copy of that loop; they now share one helper, which also takes
the temperature from the first slot that carries an RFID one rather than
giving up when slot 1 holds a third-party spool.

CHANGELOG.md

@@ -5,6 +5,7 @@ All notable changes to Bambuddy will be documented in this file.
 ## [1.2.6b1] - Unreleased
 
 ### Fixed
+- **A drying cycle no longer reports itself finished a minute after it starts (#2759)** — Starting the dryer on an AMS 2 Pro holding two PETG and two PLA spools and picking PLA showed "PLA @ 45°C" for about a minute, then switched to "PETG @ 65°C" for the remaining twelve hours. Bambu never echoes back which filament or temperature a cycle is running, so the badge reads the target Bambuddy cached when it sent the command — and that cache had been thrown away. Between accepting the command and settling its countdown the firmware publishes one update with the remaining time at zero while the unit is still in its Checking phase; the reporter's log caught 720 minutes, then 0, then 719. Bambuddy read the zero as the cycle ending. Losing the cached target left the badge to guess the filament from the first loaded slot, which happened to be PETG, and its RFID-recommended 65°C — a confident wrong answer for a cycle running PLA at 45. The same false ending also armed smart-plug auto-off-after-drying, so anyone with that switched on had power scheduled to cut one minute into a twelve-hour dry. A remaining time of zero is now only treated as the end of a cycle when the AMS also reports an idle phase, which the firmware already publishes alongside it; stopping a dry early still ends it immediately, and a unit that reports no phase at all still ends its cycles as before. The fallback guess has been tightened to match: it now answers only when every loaded spool is the same filament, and on a mixed unit the badge shows the countdown alone rather than naming a temperature the cycle isn't using. Covered by backend tests.
 - **A print that never starts now says AMS drying was running, instead of blaming the SD card (#2758)** — Sending a job to an X2D with two AMS units mid-drying failed silently: the file uploaded, the printer accepted it and then simply stayed idle. Bambuddy waited out the start watchdog, re-uploaded the whole 3MF, waited again, and after three attempts gave up with advice to check the printer's screen and the SD card — while Bambu Studio, asked directly, said it could not start the job because of the drying. Bambuddy now watches the AMS drying telemetry it already receives across the dispatch window and, when a job never starts while a unit was drying, names the units in the failure message and records the correlation in the log from the first attempt rather than only after the retries are spent. This is deliberately a diagnosis and not a rule: the printers concerned support drying *continuing* through a print, so drying and printing are not in conflict as such, and the report also involved one AMS drying without its external power supply — which would make the start-of-print calibration a power problem rather than a drying one. Stopping the cycle automatically would therefore be acting on a guess, and could tear down drying the hardware was happy to continue. Until it is known which of the two is the real obstacle, Bambuddy tells you what it saw and leaves the call to you. The message for a stalled dispatch with no drying involved is unchanged. Wiki updated. Covered by backend tests.
 - **A hand-written systemd service left the Virtual Printer unable to start, with nothing obvious to blame (#2549, reporter @Ru3ck3)** — The Virtual Printer binds ports 990 and 322, both below 1024, which a service running as a normal user may not do without the `CAP_NET_BIND_SERVICE` capability. Without it the rest of Bambuddy works perfectly and only the Virtual Printer is dead: its sockets never open, the slicer never finds the printer, and the sole trace is one line in the journal. The reporter lost days to this before someone on Discord spotted the missing line. The install script has carried it since March, but the three other places that define the same service did not — the manual-install template, the combined Bambuddy plus SpoolBuddy installer, and the unit the wiki tells you to paste. All three have it now, and the wiki no longer claims the capability is always included when its own instructions omitted it. Bambuddy also diagnoses this itself: **Diagnose** on the virtual printer card previously reported only that nothing was listening on port 990, which reads identically to an ordinary port conflict. It now checks whether the process actually holds the capability and, when that is what is wrong, says so and gives the line to add. The check stays quiet when the port is answering, since fronting it another way (an iptables redirect is the documented alternative) is a legitimate setup, and it stays quiet when the capability is held, so a port that failed for some other reason is not misattributed. Existing installs are unaffected until reinstalled; the diagnostic tells you whether yours needs the line. Translated in all locales; wiki updated. Covered by backend tests.
 - **A refused AMS filament setting now says so in the log (#2756, reporter @Jostxxl)** — Configuring a slot publishes an `ams_filament_setting` command, and the printer answers it with a verdict. That answer was received and then thrown away at debug level, so a printer that refused the write left no trace at the log level support bundles are collected at. The reporter hit exactly that: six manual **Configure Slot** attempts on one X1C, every one returning success, every one read back by the #2582 verification as still holding the previous profile, and nothing anywhere to say what the printer had made of the command. A refusal is now logged with the printer's own `result` and `reason` alongside the AMS and tray it concerned. Only refusals are promoted — unlike the K-profile and drying commands this one is not rare, since every spool assignment and every K-profile re-apply sends one, and logging each acknowledgement would bury the line worth reading. The developer-mode probe is excluded as well: it sends this same command to the external slot specifically to watch it be refused on P1 firmware, so its failure is a measurement rather than a fault. Diagnostics only — nothing about which commands are sent or how they are built has changed. Covered by backend tests.

backend/app/api/routes/printers.py

@@ -61,6 +61,7 @@ from backend.app.services.printer_manager import (
     supports_chamber_temp,
     supports_drying,
     supports_drying_while_printing,
+    uniform_tray_drying_hint,
 )
 from backend.app.utils.filament_ids import filament_id_to_setting_id
 from backend.app.utils.http import build_content_disposition
@@ -576,20 +577,18 @@ async def get_printer_status(
                     dry_target_temp = None
             if target_fil_val:
                 dry_filament = str(target_fil_val)
-            # Fallback: derive from first loaded tray when no cached target
-            # (drying started in a previous backend session, or cache wasn't
-            # seeded). Mirrors the popover seed heuristic.
+            # Fallback: derive from the loaded trays when there is no cached
+            # target (drying started in a previous backend session, or the
+            # cache wasn't seeded), and only when they agree on a filament
+            # type. See uniform_tray_drying_hint.
             if dry_target_temp is None or not dry_filament:
-                for tray in trays:
-                    if tray.tray_type:
-                        if not dry_filament:
-                            dry_filament = str(tray.tray_type)
-                        if dry_target_temp is None and tray.drying_temp:
-                            try:
-                                dry_target_temp = int(tray.drying_temp)
-                            except (TypeError, ValueError):
-                                pass
-                        break
+                hint_filament, hint_temp = uniform_tray_drying_hint(
+                    [(tray.tray_type or "", tray.drying_temp) for tray in trays]
+                )
+                if not dry_filament:
+                    dry_filament = hint_filament
+                if dry_target_temp is None:
+                    dry_target_temp = hint_temp
 
             ams_units.append(
                 AMSUnit(

backend/app/services/bambu_mqtt.py

@@ -40,6 +40,12 @@ _AMS_MODULE_PREFIXES = ("ams/", "n3f/", "n3s/")
 # printer_manager.ACTIVE_PRINT_STATES and print_scheduler._ACTIVE_PRINT_STATES.
 _ACTIVE_PRINT_STATES = frozenset({"PREPARE", "SLICING", "RUNNING", "PAUSE"})
 
+# AMS dry_status phases (info bits 4-7) in which a drying cycle is still live, so
+# a dry_time of 0 alongside one of them is a transient rather than a completion
+# (#2759). 0=Off, 4=Stopping and 5=Error all mean the cycle is over or ending and
+# are deliberately excluded — those SHOULD end it.
+_ACTIVE_DRY_STATUSES = frozenset({1, 2, 3})  # Checking, Drying, Cooling
+
 # CONNACK reason codes that mean the printer actively refused our credentials,
 # as opposed to being unreachable or busy. Bambu speaks MQTT 3.1.1, whose
 # single-byte CONNACK return codes paho maps onto the v5 reason-code space:
@@ -2789,6 +2795,27 @@ class BambuMQTTClient:
                 current = int(raw_dry_time)
             except (TypeError, ValueError):
                 continue
+            # A dry_time of 0 only means "finished" when the unit also reports
+            # an idle phase. Between the command ack and the countdown settling
+            # the firmware publishes a transient 0 while the AMS is still
+            # Checking — #2759 caught a 720 → 0 → 719 sequence one minute into a
+            # 12-hour cycle. Taking that at face value dropped the cached target
+            # (leaving the badge to guess the filament from tray 1, so a PLA
+            # cycle read "PETG @ 65°C") and fired on_drying_complete, which
+            # schedules smart-plug auto-off. dry_status comes from the same info
+            # hex parsed above; when it is absent we let the edge through, so a
+            # firmware that never reports one still ends its cycles.
+            if current == 0 and ams_unit.get("dry_status") in _ACTIVE_DRY_STATUSES:
+                # Leave the remembered value alone, exactly as the absent-
+                # dry_time skip above does: whichever push ends the cycle for
+                # real must still see a non-zero previous.
+                logger.debug(
+                    "[%s] AMS %d reported dry_time 0 in phase %s — cycle still live, ignoring",
+                    self.serial_number,
+                    ams_id,
+                    ams_unit.get("dry_status"),
+                )
+                continue
             previous = self._previous_dry_times.get(ams_id, 0)
             self._previous_dry_times[ams_id] = current
             if previous > 0 and current == 0:

backend/app/services/printer_manager.py

@@ -238,6 +238,43 @@ def drying_screen_only(model: str | None) -> bool:
     return model.strip().upper() in _DRYING_SCREEN_ONLY_MODELS
 
 
+def uniform_tray_drying_hint(loaded_trays: list[tuple[str, object]]) -> tuple[str | None, int | None]:
+    """Guess an active cycle's filament + target temperature from the loaded trays.
+
+    Bambu never echoes back which filament or temperature a drying cycle is
+    running, so the badge normally reads the target we cached when we sent the
+    command. This is the fallback for when we have no record — drying started in
+    a previous backend lifetime, or from the printer's own screen.
+
+    It answers only when every loaded tray holds the same filament type. On a
+    mixed unit the first tray is evidence of nothing: an AMS holding two PETG
+    and two PLA spools, drying PLA at the 45°C the user picked, was labelled
+    "PETG @ 65°C" purely because slot 1 happened to be PETG (#2759). Saying
+    nothing and letting the badge show just the countdown beats stating a
+    temperature the cycle isn't using.
+
+    Args:
+        loaded_trays: ``(tray_type, drying_temp)`` for each tray, in slot order.
+            Empty slots (falsy tray_type) are ignored. ``drying_temp`` is the
+            RFID-recommended value and may be None or unparseable.
+
+    Returns:
+        ``(filament, temp)``, either of which may be None.
+    """
+    types = {str(tray_type) for tray_type, _ in loaded_trays if tray_type}
+    if len(types) != 1:
+        return None, None
+    filament = next(iter(types))
+    for tray_type, drying_temp in loaded_trays:
+        if not tray_type or not drying_temp:
+            continue
+        try:
+            return filament, int(drying_temp)
+        except (TypeError, ValueError):
+            continue
+    return filament, None
+
+
 def supports_drying(model: str | None, firmware: str | None) -> bool:
     """Check if a printer model accepts remote AMS drying commands.
 
@@ -1254,9 +1291,8 @@ def printer_state_to_dict(
             # per-tick AMS push, so prefer the cached target from the last
             # ``send_drying_command``. When we have no record (drying
             # started in a previous backend lifetime, or the cache was
-            # never seeded), fall back to the first loaded tray's
-            # tray_type + RFID-recommended drying_temp — the same heuristic
-            # the popover already uses to seed defaults.
+            # never seeded), fall back to the loaded trays — but only when
+            # they agree on a filament type. See uniform_tray_drying_hint.
             ams_id_int = int(ams_data.get("id", 0))
             target = (drying_targets or {}).get(ams_id_int)
             dry_target_temp: int | None = None
@@ -1272,16 +1308,13 @@ def printer_state_to_dict(
                 if fil_val:
                     dry_filament = str(fil_val)
             if dry_target_temp is None or not dry_filament:
-                for tray in trays:
-                    if tray.get("tray_type"):
-                        if not dry_filament:
-                            dry_filament = str(tray["tray_type"])
-                        if dry_target_temp is None and tray.get("drying_temp"):
-                            try:
-                                dry_target_temp = int(tray["drying_temp"])
-                            except (TypeError, ValueError):
-                                pass
-                        break
+                hint_filament, hint_temp = uniform_tray_drying_hint(
+                    [(tray.get("tray_type") or "", tray.get("drying_temp")) for tray in trays]
+                )
+                if not dry_filament:
+                    dry_filament = hint_filament
+                if dry_target_temp is None:
+                    dry_target_temp = hint_temp
 
             ams_units.append(
                 {

backend/tests/unit/services/test_bambu_mqtt.py

@@ -6078,6 +6078,48 @@ class TestDryingCompleteCallback:
         mqtt_client._handle_ams_data({"ams": [{"id": "0", "dry_time": 0, "tray": []}]})
         assert mqtt_client._drying_events == [0]
 
+    def test_transient_zero_while_checking_is_not_completion(self, mqtt_client):
+        """#2759 — between the command ack and the countdown settling, firmware
+        publishes a dry_time of 0 while the AMS is still in its Checking phase.
+        The reporter's log caught 720 → 0 → 719 one minute into a 12-hour
+        cycle: it dropped the cached target (so the badge guessed the filament
+        from tray 1 and read "PETG @ 65°C" for a PLA dry) and armed smart-plug
+        auto-off."""
+        mqtt_client._drying_targets[0] = {"filament": "PLA", "temp": 45}
+        # Cycle starts: 12 hours, unit reports dry_status 1 (Checking).
+        mqtt_client._handle_ams_data({"ams": [{"id": "0", "dry_time": 720, "info": "11402113", "tray": []}]})
+        assert mqtt_client._drying_events == []
+
+        # The blip: dry_time 0, still Checking.
+        mqtt_client._handle_ams_data({"ams": [{"id": "0", "dry_time": 0, "info": "11402113", "tray": []}]})
+        assert mqtt_client._drying_events == []
+        # And the user's chosen target survived it.
+        assert mqtt_client._drying_targets[0] == {"filament": "PLA", "temp": 45}
+
+        # Countdown settles and the unit moves to dry_status 2 (Drying).
+        mqtt_client._handle_ams_data({"ams": [{"id": "0", "dry_time": 719, "info": "11402123", "tray": []}]})
+        assert mqtt_client._drying_events == []
+
+        # Twelve hours later it really finishes, back to dry_status 0 (Off).
+        mqtt_client._handle_ams_data({"ams": [{"id": "0", "dry_time": 0, "info": "11402103", "tray": []}]})
+        assert mqtt_client._drying_events == [0]
+        assert 0 not in mqtt_client._drying_targets
+
+    def test_zero_while_stopping_completes(self, mqtt_client):
+        """dry_status 4 (Stopping) means the cycle is ending, not running — the
+        edge must still fire so smart-plug auto-off runs when a user stops a
+        dry early."""
+        mqtt_client._handle_ams_data({"ams": [{"id": "0", "dry_time": 720, "info": "11402123", "tray": []}]})
+        mqtt_client._handle_ams_data({"ams": [{"id": "0", "dry_time": 0, "info": "11402143", "tray": []}]})
+        assert mqtt_client._drying_events == [0]
+
+    def test_absent_dry_status_still_completes(self, mqtt_client):
+        """The phase gate is a suppression, not a requirement: firmware that
+        never reports an info hex must still be able to end a cycle."""
+        mqtt_client._handle_ams_data({"ams": [{"id": "0", "dry_time": 720, "tray": []}]})
+        mqtt_client._handle_ams_data({"ams": [{"id": "0", "dry_time": 0, "tray": []}]})
+        assert mqtt_client._drying_events == [0]
+
 
 class TestPrintRunningObservedCallback:
     """#1485 follow-up: on_print_running_observed fires the FIRST time we

backend/tests/unit/services/test_printer_manager.py

@@ -1378,8 +1378,8 @@ class TestDryingTargetExposure:
         assert result["ams"][0]["dry_target_temp"] == 65
 
     def test_falls_back_to_loaded_tray_when_no_cache(self):
-        """No cached target → derive from first loaded tray's tray_type +
-        RFID-recommended drying_temp (popover seed heuristic)."""
+        """No cached target → derive from the loaded trays' tray_type +
+        RFID-recommended drying_temp when they agree on a filament."""
         state = self._state_with_ams(
             {
                 "id": 0,
@@ -1419,6 +1419,64 @@ class TestDryingTargetExposure:
         assert result["ams"][0]["dry_filament"] is None
         assert result["ams"][0]["dry_target_temp"] is None
 
+    def test_no_fallback_when_loaded_trays_disagree(self):
+        """#2759 — the reporter's AMS held 2 PETG and 2 PLA and was drying the
+        PLA at 45°C, but the fallback read slot 1 and labelled it "PETG @ 65°C".
+        A mixed unit gives no evidence of what the cycle is running, so the
+        badge must show the countdown alone rather than a confident wrong
+        answer."""
+        state = self._state_with_ams(
+            {
+                "id": 0,
+                "dry_time": 719,
+                "tray": [
+                    {"id": 0, "tray_type": "PETG", "drying_temp": 65, "state": 11},
+                    {"id": 1, "tray_type": "PETG", "drying_temp": 65, "state": 11},
+                    {"id": 2, "tray_type": "PLA", "drying_temp": 45, "state": 11},
+                    {"id": 3, "tray_type": "PLA", "drying_temp": 45, "state": 11},
+                ],
+            }
+        )
+        result = printer_state_to_dict(state, drying_targets={})
+        assert result["ams"][0]["dry_filament"] is None
+        assert result["ams"][0]["dry_target_temp"] is None
+
+    def test_fallback_survives_multiple_trays_of_one_type(self):
+        """Agreement across slots is still evidence — a unit loaded entirely
+        with PLA keeps the fallback the mixed case gives up."""
+        state = self._state_with_ams(
+            {
+                "id": 0,
+                "dry_time": 719,
+                "tray": [
+                    {"id": 0, "tray_type": "PLA", "drying_temp": 45, "state": 11},
+                    {"id": 1, "tray_type": "PLA", "drying_temp": 45, "state": 11},
+                    {"id": 2},
+                ],
+            }
+        )
+        result = printer_state_to_dict(state, drying_targets={})
+        assert result["ams"][0]["dry_filament"] == "PLA"
+        assert result["ams"][0]["dry_target_temp"] == 45
+
+    def test_fallback_takes_temp_from_a_later_tray_when_slot_one_has_none(self):
+        """Only Bambu spools carry an RFID drying_temp. A third-party spool in
+        slot 1 alongside a genuine one of the same type should not cost us the
+        temperature."""
+        state = self._state_with_ams(
+            {
+                "id": 0,
+                "dry_time": 719,
+                "tray": [
+                    {"id": 0, "tray_type": "PLA", "state": 11},
+                    {"id": 1, "tray_type": "PLA", "drying_temp": 45, "state": 11},
+                ],
+            }
+        )
+        result = printer_state_to_dict(state, drying_targets={})
+        assert result["ams"][0]["dry_filament"] == "PLA"
+        assert result["ams"][0]["dry_target_temp"] == 45
+
 
 class TestSupportsChamberTemp:
     """Tests for supports_chamber_temp helper function."""