/**
 * Returns `true` when the given session has a non-empty `parentID`
 * (subagent). Returns `false` for primary sessions, when the SDK is
 * unavailable, or when any error occurs — the false default keeps
 * primary sessions working exactly as before.
 *
 * First call per session: one SDK round-trip. All subsequent calls:
 * O(1) cache lookup.
 */
export declare function resolveIsSubagent(client: unknown, sessionId: string | undefined, _fallbackDirectory?: string): Promise<boolean>;
/** Test-only cache reset. Not exported from the public surface. */
export declare function _resetSubagentCacheForTest(): void;
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