TL;DR
- I publish a JSON payload with device_tracker.location set to “home”/“not_home”.
- My MQTT device_tracker sometimes ends up in the wrong state or stays stale.
- I’m looking for concrete ways to observe how Home Assistant evaluates value_template and matches it to payload_home/payload_not_home (logs, traces, debugging tools), and for any known pitfalls.
Context
- I’m using the MQTT device_tracker platform.
- JSON is published using Home Assistant’s mqtt.publish service via Tasker on Android.
- Messages are received on the expected topic and consumed by other MQTT sensors fine, but the device_tracker state in HA is occasionally wrong or doesn’t update as expected.
Current YAML (device_tracker)
Note: state_value_template is deprecated, so I’m using value_template.
mqtt:
device_tracker:
- name: "Posizione"
object_id: "tablet_di_simone"
unique_id: "tablet_di_simone"
icon: "mdi:cellphone"
device:
name: "Tablet di Simone"
identifiers: !secret tablet_di_simone_identifiers
manufacturer: !secret tablet_di_simone_manufacturer
model: !secret tablet_di_simone_model
sw_version: !secret tablet_di_simone_sw_version
state_topic: "Dispositivi/Simone/tablet"
value_template: "{{ value_json.device_tracker.location }}"
payload_home: "home"
payload_not_home: "not_home"
payload_reset: "None"
json_attributes_topic: "Dispositivi/Simone/tablet"
json_attributes_template: "{{ value_json.device_tracker.attributes | tojson }}"
Example payload being published
Note: The home coordinates and Wi‑Fi BSSID below are fictional placeholders for privacy.
{
"device_tracker": {
"location": "home",
"attributes": {
"source_type": "gps",
"latitude": 45.464211,
"longitude": 9.191383,
"gps_accuracy": 10,
"altitude": 62.66,
"speed": 0.0
}
},
"battery_stats": {
"battery": 43,
"battery_charging": false,
"battery_health": "Buono",
"battery_temperature": 28.7,
"battery_power_source": "Batteria",
"energy_saving": false,
"time_until_charged": 0
},
"connectivity": {
"bluetooth": "on",
"wifi": "on",
"wifi_connected": true,
"wifi_ssid": "HomeWiFi_2G",
"wifi_bssid": "AA:BB:CC:DD:EE:FF",
"local_ip_address": "192.168.1.107"
},
"attività": { "attività": "still" },
"device_lost": { "device_lost": false },
"alarm_clock": { "alarm_clock": true, "attributes": { "Prossima sveglia": 1762408800 } },
"sleeping_mode": false,
"last_status_updated": 1762368399
}
Symptoms
- The device_tracker state occasionally doesn’t reflect the latest payload (“home” vs “not_home”), or it stays stale after reconnects/restarts.
- Other sensors that parse the same JSON work as expected, which makes me think this is about how the device_tracker template is evaluated or how payload matching happens.
What I expected
- Each incoming message with location “home” or “not_home” should reliably update the entity state to home/not_home, and attributes should reflect the nested JSON.
What I’ve tried
- Set logger to debug for MQTT and device_tracker:
logger: default: warn logs: homeassistant.components.mqtt: debug homeassistant.components.device_tracker: debug homeassistant.helpers.template: debug - Verified the topic and payload in Developer Tools > MQTT > “Listen to a topic” (Dispositivi/Simone/#).
- Ensured the JSON path matches my payload (value_json.device_tracker.location).
- Normalized the output (lower/trim) in a test template to avoid whitespace/case issues.
- Considered retained messages: I can clear (-n -r) on the state topic to eliminate stale retained states if that’s a common trap.
- Full HA restart after config changes.
Questions for the community
- How can I see exactly what string HA thinks the template produced for value_template on each message? Is there a built-in trace/log that shows:
- The raw incoming payload,
- The evaluated result of value_template,
- The final decision vs payload_home/payload_not_home?
- Are there known pitfalls when using MQTT device_tracker with nested JSON + json_attributes_template? For example:
- Cases where Jinja returns a Python None which becomes the string “None”,
- Retained messages forcing stale states after restart,
- Case/whitespace sensitivities in payload matching.
- Is there a recommended “best practice” template for robust parsing here (e.g., defensive checks for missing keys)?
- Any tips to differentiate issues caused by:
- Template evaluation (wrong/missing path),
- Retained vs live messages,
- Broker reconnects (message order/duplicates),
- Attribute parsing failures?
Minimal reproducible test I can run
- Publish from Developer Tools > MQTT to Dispositivi/Simone/tablet with:
retain=false, QoS=0.{ "device_tracker": { "location": "home", "attributes": { "source_type": "gps", "latitude": 45.464211, "longitude": 9.191383, "gps_accuracy": 10 } } } - Expect the entity to switch to home; repeat with not_home.
- If this works but real-world messages don’t, I suspect retained or timing/interleaving.
Thanks in advance for pointers on how to trace template evaluation for MQTT device_trackers (or confirm retained vs. live messages causing mismatches). Links to docs/tools or example debug snippets would be greatly appreciated!