/**
 * The host's declaration of what it does with a view's gestures (ggui#1309),
 * carried as the `Ggui-Host-Capabilities` request header on the MCP
 * connection to a ggui server.
 *
 * **Parties.** The HOST's own code sets the header (its MCP client's
 * connection configuration) — never the model: a flag the model can write
 * would be the agent writing behaviour into the contract, and could not be
 * verified. The SERVER reads it per request and adjusts agent-facing hints.
 * The AGENT follows the hints it is given.
 *
 * **Value.** Comma-separated tokens. A server ignores a token it does not
 * name (tolerant read, VERSION-POLICY §3.6), so a later capability rides the
 * same header without breaking an older server. On a transport with no
 * headers (stdio) there is no declaration, and behaviour is unchanged.
 */
/** The header name, lowercase (HTTP header names are case-insensitive; Node lowercases them). */
export declare const GGUI_HOST_CAPABILITIES_HEADER = "ggui-host-capabilities";
/**
 * `ui-message-turn` — the host delivers every `ui/message` the view posts as
 * a later agent turn (at once when no turn is in progress, after the live
 * turn ends when one is, never by cancelling it), or answers that
 * `ui/message` to the view in-band with an error, never a success: the error
 * names the drop to the view that posted it. A host declares it only for a
 * client that does this, per request (for the client driving that call).
 * Effect on a ggui server: a render response omits its
 * `nextStep: ggui_consume` hint, because a later gesture reaches the agent as
 * a turn anyway — so the agent ends its turn at paint. A refused `ui/message`
 * costs the wake-up, not the gesture, which is already on the consume pipe.
 * Observable violation: a view's `ui/message` that neither yields a later
 * turn nor is answered with an error.
 */
export declare const HOST_CAPABILITY_UI_MESSAGE_TURN = "ui-message-turn";
/**
 * Parse the header's value (a string, a repeated header's array, or absent)
 * into its tokens: trimmed, lowercased, de-duplicated, empties dropped,
 * unknown tokens KEPT. Absent or empty ⇒ `[]`.
 */
export declare function parseHostCapabilitiesHeader(raw: string | readonly string[] | undefined): readonly string[];
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