/**
 * Billing-mode probe: which auth a headless adapter child will actually use.
 *
 * The engine never handles credentials — children are plain adapter CLIs and
 * authenticate however that CLI does. But the CLIs prefer an exported API key
 * over a stored (subscription) login when both are present, and that override
 * is almost always an accident: a sourced .env or a leftover export silently
 * moves the run from subsidized subscription billing to per-token API billing.
 * This probe classifies the state per adapter so the engine can refuse the
 * silent-override case (see decision 0015 addendum) while leaving deliberate
 * key-only hosts (CI boxes with no login) working.
 *
 * Detection is a heuristic over well-known credential locations; when a
 * location can't prove presence or absence (e.g. Claude Code stores its OAuth
 * token in the macOS keychain, not a file), the state is "unknown" and the
 * engine never hard-fails on it — the adapter CLI itself is the final
 * authority and will error loudly if truly unauthenticated.
 */
import type { AdapterName } from "./types.js";
/** The env var each adapter CLI reads as an API key (preferred over a stored
 * login when set). Shared with the child-env builder's subscription-only
 * scrub. */
export declare const API_KEY_VARS: Record<string, string>;
export type LoginState = "present" | "absent" | "unknown";
export type BillingMode = 
/** No API key exported; the child rides the stored (subscription) login. */
"subscription"
/** API key present, no stored login detected: a deliberate key-only host. */
 | "api-key"
/** API key present AND a stored login exists: the key silently overrides
 * subsidized auth. The engine refuses this unless explicitly allowed. */
 | "api-key-override";
export interface BillingProbe {
    adapter: AdapterName;
    /** The env var checked (from API_KEY_VARS), or a note when the key was
     * found in a credential file instead of the environment. */
    apiKeySource: string | null;
    apiKeyPresent: boolean;
    login: LoginState;
    mode: BillingMode;
}
export interface ProbeIo {
    env?: NodeJS.ProcessEnv;
    home?: string;
}
export type BillingProber = (adapter: AdapterName) => BillingProbe;
export declare function probeBilling(adapter: AdapterName, io?: ProbeIo): BillingProbe;
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