/**
 * Typed INBOUND control vocabulary for the `relay` family (ADR 0056, ACP steer).
 *
 * The relay data frame ({@link RelayPayload} `{ stream, offset, chunk }`) is the
 * OUTBOUND (hub → consumer) byte lane and is left untouched. This module adds an
 * ADDITIVE vocabulary for the INBOUND (consumer → agent) steer lane, where a
 * peer historically sent a bare `chunk` string that a PTY role fed straight to
 * the terminal as keystrokes. ACP steering must now distinguish three intents:
 *
 *  - `prompt`     — start a new turn (carries the prompt text);
 *  - `cancel`     — interrupt the current turn (optionally with a reason);
 *  - `permission` — answer/release a blocked `session/request_permission`
 *                   (carries the request id being answered + the outcome).
 *
 * ## Backward compatibility (raw-byte steer)
 *
 * The vocabulary is a STRICT superset of the legacy raw-byte path. A structured
 * frame is a JSON envelope TAGGED with {@link CONTROL_FRAME_MARKER}; a bare
 * inbound string that is NOT such a tagged envelope (a keystroke, a shell line,
 * unrelated JSON) continues to decode as a `prompt` whose `text` is the original
 * chunk verbatim. Existing raw-byte producers and consumers need not change.
 *
 * ## Decode order (see {@link parseInboundRelayChunk})
 *
 *  1. If the chunk parses as a control envelope (a JSON object tagged with the
 *     marker at the current version) → validate it and return the typed frame;
 *     a tagged-but-malformed envelope is an ERROR, never a silent prompt.
 *  2. Otherwise → legacy fall-back: `{ kind: "prompt", text: <chunk> }`.
 *
 * This is purely the inbound control vocabulary at the protocol seam: it changes
 * neither the relay transport (ring, QoS, offsets, stream routing) nor the
 * outbound `{ stream, offset, chunk }` data-frame shape.
 */
/**
 * The marker key that tags a chunk as a structured inbound control envelope.
 * Its value is the {@link CONTROL_FRAME_VERSION}. A chunk without this key is a
 * legacy bare-string steer and decodes as a `prompt`.
 */
export declare const CONTROL_FRAME_MARKER: "nanoControlFrame";
/** The schema version carried by the {@link CONTROL_FRAME_MARKER}. */
export declare const CONTROL_FRAME_VERSION: 1;
/** The three inbound steer intents. */
export type InboundControlKind = "prompt" | "cancel" | "permission";
/** How a blocked `session/request_permission` was answered. */
export type PermissionOutcome = "granted" | "denied";
/** Start a new turn with the given prompt text. */
export interface PromptControlFrame {
    readonly kind: "prompt";
    readonly text: string;
}
/** Interrupt the current turn. `reason` is advisory, for telemetry/audit. */
export interface CancelControlFrame {
    readonly kind: "cancel";
    readonly reason?: string;
}
/** Answer a blocked `session/request_permission` identified by `requestId`. */
export interface PermissionControlFrame {
    readonly kind: "permission";
    readonly requestId: string;
    readonly outcome: PermissionOutcome;
}
/** The typed inbound control vocabulary — a discriminated union on `kind`. */
export type InboundControlFrame = PromptControlFrame | CancelControlFrame | PermissionControlFrame;
export interface InboundControlError {
    readonly code: InboundControlErrorCode;
    readonly message: string;
}
/**
 * The closed set of validation-error codes a tagged-but-malformed control
 * envelope can raise. The conformance corpus derives its coverage from this
 * union, so a new code cannot be added without a covering malformed vector.
 */
export type InboundControlErrorCode = "bad-kind" | "bad-prompt-text" | "bad-cancel-reason" | "bad-permission-request-id" | "bad-permission-outcome";
/**
 * The result of decoding an inbound steer chunk. `structured` distinguishes a
 * recognised control envelope from the legacy bare-string-as-prompt fall-back,
 * so a consumer can tell an explicit `prompt` frame from a raw keystroke.
 */
export type InboundControlDecodeResult = {
    readonly ok: true;
    readonly frame: InboundControlFrame;
    readonly structured: boolean;
} | {
    readonly ok: false;
    readonly errors: readonly InboundControlError[];
};
/**
 * Is `value` a structured inbound control envelope (a plain object tagged with
 * the marker at the current version)? This is the discriminator the decoder uses
 * to choose the structured path over the legacy bare-string fall-back — it does
 * NOT assert the envelope's `kind`-specific fields are well-formed.
 */
export declare function isInboundControlEnvelope(value: unknown): value is Record<string, unknown>;
/**
 * Decode a raw inbound steer chunk into a typed {@link InboundControlFrame}.
 *
 * A chunk tagged as a control envelope is validated and returned as its typed
 * frame (`structured: true`); a tagged-but-malformed envelope (bad/missing
 * discriminant, missing/ill-typed field) is a validation ERROR. Any other chunk
 * — a bare keystroke, a shell line, unrelated JSON — is treated as the legacy
 * raw-byte steer and returned as a `prompt` whose `text` is the chunk verbatim
 * (`structured: false`). See the module header for the full decode order.
 */
export declare function parseInboundRelayChunk(chunk: string): InboundControlDecodeResult;
/**
 * Encode a typed {@link InboundControlFrame} as its canonical wire chunk — a
 * JSON envelope tagged with {@link CONTROL_FRAME_MARKER}. The result round-trips
 * back through {@link parseInboundRelayChunk} to an equal frame.
 */
export declare function encodeInboundControlFrame(frame: InboundControlFrame): string;