/**
 * Config and identity persistence for the Sideband CLI.
 *
 * Config directory: $SIDEBAND_HOME or ~/.sideband/
 *   config.json   — { apiKey: string }
 *   identity.json — { type: "ed25519", publicKey: "<hex>", privateKey: "<hex>" }
 *
 * All file writes are atomic (write to .tmp, rename) with 0o600 permissions
 * so secrets are never world-readable, even on a partial write.
 */
import type { IdentityKeyPair } from "@sideband/secure-relay";
export interface Config {
    apiKey?: string;
}
/** Resolved config directory (SIDEBAND_HOME or ~/.sideband). */
export declare function getConfigDir(): string;
/**
 * Resolve API key with priority: flag > SIDEBAND_API_KEY env > config file.
 * Returns undefined if none found.
 */
export declare function resolveApiKey(fromFlag: string | undefined, configDir: string): Promise<string | undefined>;
/** Read config.json. Returns null if the file does not exist. */
export declare function loadConfig(configDir: string): Promise<Config | null>;
/** Write config.json atomically with 0o600 permissions. */
export declare function saveConfig(configDir: string, config: Config): Promise<void>;
/** Load identity.json; generate and save if missing. */
export declare function loadIdentityKeyPair(configDir: string): Promise<IdentityKeyPair>;
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