Architectural Contracts
-----------------------

The interaction between the Health Evaluation Model and
``HealthDiagnostics`` is governed by a clear input/output contract.

Evaluation Model Responsibilities
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The Health Evaluation Model guarantees that:

- The aggregated ``HealthState`` is fully determined before
  diagnostics generation.
- Any forced operational condition is explicitly represented
  in the evaluation result.
- Contextual information required for explanation is provided
  in a structured form.
- No partial or transitional states are exposed.


The model remains the single authoritative source of truth
for the system health classification.

Diagnostics Responsibilities
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

``HealthDiagnostics`` guarantees that:

- It does not modify or reinterpret the aggregated
  ``HealthState``.
- It generates explanatory messages consistent with the
  evaluation result.
- Forced conditions take precedence over snapshot-derived
  explanations.
- Output messages are deterministic and derived solely from
  the provided inputs.

Boundary Conditions
^^^^^^^^^^^^^^^^^^^

- Diagnostics must not trigger re-evaluation of health.
- Evaluation must not depend on diagnostic formatting rules.
- Timing and supervision logic remain external to both
  components.

HealthInfo Publication Contract
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The publication of the ``HealthInfo`` attribute follows these guarantees:

- Forwarded subsystem ``HealthInfo`` change events are buffered.
- For each subscribed subsystem source, only the latest received
  payload is retained until the next evaluation cycle.
- Forwarded updates are merged together with locally generated
  diagnostics during evaluation.
- At most one aggregated ``HealthInfo`` attribute update is emitted
  per evaluation cycle (subject to change detection).
- No redundant publication occurs if the aggregated content is
  unchanged.

This contract ensures that multiple subsystem diagnostic updates
occurring in rapid succession are coalesced by the supervision
debounce mechanism and do not produce excessive parent-level
``HealthInfo`` events, while preserving deterministic and
snapshot-consistent behaviour.