### Changed
- Minimum optional AbstractCore dependency floor is now `abstractcore>=2.13.27` (and matching `multimodal`, `mcp-worker`, and hardware-profile cascade extras), aligning Runtime with the latest Core capability plugin floors and server contracts.

### Fixed
- Remote and VisualFlow music generation now fail closed on legacy `backend` / `music_backend` selectors and require `provider` / `music_provider` as the backend selector, matching AbstractCore Server `/v1/audio/music` validation.
- VisualFlow `generate_music` lowering now preserves boolean `structure_prompt` values (including explicit `False`) in the pending output selector, keeping the Flow/Gateway/Core contract consistent.
