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Home Assistant Context

Context is used to tie events and states together in Home Assistant. Whenever anything (e.g. an automation or user interaction) triggers a new change, a new context is assigned. This context will be attached to all events and states that happen as result of the change. The context thus allows to attribute all changes to their original cause internally and in the logbook.

A context object contains the following fields:

FieldDescription
idUnique identifier for the context.
user_idUnique identifier of the user that started the change, in case it is known to home assistant. This field is most notably populated, if the change is initiatited via the frontend. The user_id is used for restricting the ability to access and change the state of your home.
parent_idUnique identifier of the parent context's id that started the change. Most notably, automations will generate a new context, even if the trigger already has one. This is done to decouple the automation actions from the user privileges possibly associated to the trigger. Note that, currently, not all triggers generate a context.

In the following example, all events and states will refer to the same context (either directly in their context.id or via context.parent_id):

  • Paulus arrives home, which updates device_tracker.paulus_pixel from not_home to home
  • The automation "Paulus is home" is triggered and fires automation_triggered event (with a new context.id and a reference to the old id in context.parent_id).
  • The automation calls service light.turn_on, which fires the service_call event.
  • The light.turn_on service turns on the light which causes an update to the state of light.living_room.

Context is not stored in their own table in the database. Instead, each event row maintains it's own columns to store context.

Currently, there is no native way to retrieve the original cause of a context in automations or templates.

Example queries​

Finding the context_id for a state_changed event in the database.​

SELECT states_meta.entity_id, states.state, hex(states.context_id_bin), hex(states.context_user_id_bin), hex(states.context_parent_id_bin) FROM states LEFT JOIN states_meta ON (states.metadata_id=states_meta.metadata_id);

Finding the context_id for an event in the database.​

SELECT event_types.event_type, event_data.shared_data, hex(events.context_id_bin), hex(events.context_user_id_bin), hex(events.context_parent_id_bin) FROM events  LEFT JOIN event_data ON (events.data_id=event_data.data_id) LEFT JOIN event_types ON (events.event_type_id=event_types.event_type_id);