# ADR 0001: LCD Expression and Presentation Ownership

## Status

Accepted

## Context

LCD behavior now needs multiple reusable expressions that can be triggered by
different runtime conditions. The system must keep semantic expression ownership
separate from low-level LCD playback so future expressions can be added without
copying cross-layer contracts or coupling orchestration code to asset paths.

## Decision

- `domain` owns LCD expression semantics and declares `domain_expression_*` in
  `components/domain/include/domain.h`.
- `control_plane` owns trigger policy: it decides when a runtime condition
  requests a semantic expression.
- `platform` owns LCD presentation playback primitives and declares
  `platform_lcd_presentation_*` in `components/platform/include/platform.h`.
- Domain runtime adapters map semantic expressions to platform presentation
  requests.
- Platform LCD internals serialize presentation requests and perform all panel
  drawing inside the LCD render task.

## Consequences

- Adding a new expression requires a domain expression ID and catalog mapping,
  plus an optional control-plane trigger rule.
- Public upper-layer facades must not expose platform playback types.
- Platform public APIs must not expose domain semantic expression IDs.
- High-priority expressions can interrupt lower-priority presentations without
  leaking policy logic into the LCD driver.