useComposers(selector) in any plugin component and composers(selector) on every command context return the composer of a running agent, named by id or by focus, whether or not its tab is open.
A running agent now has one store-backed composer model apart from any mounted tab. The mounted composer plugs its cursor-aware insert in while mounted; otherwise insertText and setPrompt write the agent's saved prompt. model and thinking resolve through the provider catalog with the picker's own function, so a read equals what the picker shows.
The host reads one ComposerModel from context and no longer knows whether it is in an agent, a draft or New workspace. The daemon rejects an unlisted model or thinking option for a running agent, replacing the app-side guard.