A use-case record describes an engine variant assembled for a delivery scenario. Feature records answer what the engine can do; use-case records answer why a consumer needs a different composition.

Qualification

Create a use-case record only when the candidate:

names a concrete delivery scenario and consumer;
changes composition by adding, omitting, replacing, or differently configuring behavior;
builds on identifiable SPF capabilities; and
cannot be expressed as runtime policy in the default composition.

Adapter UI and product-shell defaults stay outside SPF. A single capability belongs in features rather than here.

Record shape

Keep each record short:

the scenario and status;
durable composition decisions or proposed direction;
unresolved decisions needed before implementation;
current source links for implemented variants;
links to constituent feature records.

Do not preserve phase tables, speculative file inventories, or progress logs after code lands.

Current variants

Audio-only mode override: implemented subtractive HLS composition.
Background video: implemented decorative-video composition.
Video-only mode override: future generic variant; requires a consumer distinct from background video.

Most delivery policy should remain a feature constraint or adapter concern. Add another composition record only when the qualification above is satisfied.