/**
 * Linkup credential resolution.
 *
 * Single source of truth for the Linkup API key (`LINKUP_API_KEY`).
 * Whitespace-only values are treated as absent, matching the
 * descriptor's `isConfigured` contract. Resolved keys are returned
 * trimmed so wire headers never carry stray whitespace.
 *
 * Boundary rules (ARCHITECTURE.md §2):
 *   - May import the normalized-error contract only.
 *   - Must NOT import transport, command presentation, or another
 *     Provider's Adapter.
 *
 * Missing credentials are surfaced as {@link ConfigurationError}
 * (exit 3), distinct from {@link AuthError} (exit 1) which means the
 * Provider REJECTED a presented credential.
 */
/** Credential environment names read by this module (#232 derivation pin). */
export declare const ENV_NAMES: readonly ["LINKUP_API_KEY"];
/**
 * Resolve the Linkup API key without throwing. Returns the trimmed key
 * or `undefined` when no non-blank value is present.
 */
export declare function getLinkupApiKey(env: NodeJS.ProcessEnv): string | undefined;
/**
 * Resolve the Linkup API key or throw {@link ConfigurationError}
 * (exit 3) when it is missing. Call this at every capability
 * invocation gate.
 */
export declare function requireLinkupApiKey(env: NodeJS.ProcessEnv): string;
/**
 * True when a non-blank Linkup API key is configured. Metadata-only:
 * performs no transport construction and reads no other Provider's
 * credentials.
 */
export declare function isLinkupConfigured(env: NodeJS.ProcessEnv): boolean;
/**
 * Lowercase hex SHA-256 fingerprint of the Linkup API key. Used for
 * partitioned cache identity; the raw key must never appear in cache
 * filenames, errors, or logs.
 */
export declare function hashLinkupApiKey(key: string): string;
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