/** One piece of per-message context. Context for the model, never instructions. */
export type MessageContextItem = Readonly<{
    /** Stable identity, such as "selection"; leaving an item out is remembered per id and label. */
    id: string;
    /** The text the model receives with each message. */
    text: string;
    /** Short pill text, such as "Sheet1 · B2:D14". Without one, the item is sent but not shown. */
    label?: string | undefined;
    /** Longer description in the pill's tooltip. */
    detail?: string | undefined;
}>;
/**
 * What a page supplies: plain text, one item, a list of items, or a function
 * read when each message is sent (not shown in the composer).
 */
export type MessageContextInput = string | MessageContextItem | readonly MessageContextItem[] | (() => string | undefined) | undefined;
export type MessageContextPill = Readonly<{
    id: string;
    label: string;
    detail?: string | undefined;
    /** The person left this out of their messages. */
    excluded: boolean;
}>;
export type MessageContextStore = Readonly<{
    set(input: MessageContextInput): void;
    /** The pills to show, stable between changes (for useSyncExternalStore). */
    pills(): readonly MessageContextPill[];
    subscribe(listener: () => void): () => void;
    exclude(id: string): void;
    include(id: string): void;
    /** The context text to send with a message now, without excluded items. */
    forSend(): string | undefined;
}>;
export declare function createMessageContextStore(initial?: MessageContextInput): MessageContextStore;