/**
 * The provider echo shape — the ONE alphabet for upstream bytes the engine carries verbatim (#1204): visible ASCII
 * (0x21–0x7E — no space, no control byte, no non-ASCII), 1–128 characters. The echo fields (`requestId`,
 * `responseModel`) are carried or dropped by it, and a provider-minted tool-call id is admitted verbatim or folded
 * by it (`tool-call-id.ts`).
 *
 * Zero-dependency leaf: `tool-call-id.ts` (itself a leaf, see its header) reads the shape from here. `errors.ts`
 * re-exports the two public names, which is where the package root takes them from.
 */
/** The longest value the shape admits. */
export declare const PROVIDER_ECHO_MAX_CHARS = 128;
/**
 * The shape a provider ECHO field must have to be carried: the request id a provider states on a response
 * header (`AssistantMessage.requestId`, projected as `TaskResult.apiFailure.requestId`) and the model name it
 * reports answering (`AssistantMessage.responseModel`). Both are UPSTREAM BYTES that end up persisted in a
 * transcript and rendered by a UI, so one alphabet governs both: visible ASCII (0x21–0x7E — no space, no
 * control byte, no non-ASCII), 1–128 characters. A value outside it is dropped (the field is absent), never
 * truncated or rewritten; the empty string is outside it. No flags, so `test` is stateless. This object is the
 * consumer's copy: the engine judges with its own instance built from the same source, so recompiling or
 * otherwise mutating this one cannot change what the engine admits.
 */
export declare const PROVIDER_ECHO_SHAPE: RegExp;
/** Does `value` fit {@link PROVIDER_ECHO_SHAPE}? A non-string answers `false` (a JS caller's number is not an echo). */
export declare function isProviderEchoShape(value: string): boolean;
/** Is every character of `value` in the shape's alphabet, whatever its length? (`""` answers `true`.) */
export declare function fitsProviderEchoCharset(value: string): boolean;