export interface AdmissionConfig {
    /** Base directory holding one subdirectory per resource. */
    dir: string;
    /** Resource name, e.g. "browser-qa" or "build". */
    resource: string;
    /** Maximum concurrent holders. */
    capacity: number;
    /** Poll interval while waiting (default 500ms). */
    pollMs?: number;
    /** Entries older than this are pruned regardless of PID (default 6h). */
    ttlMs?: number;
}
export interface AdmissionEntry {
    pid: number;
    label: string;
    created_at: string;
    /** Set on holders once admitted. */
    acquired_at?: string;
}
export interface AdmissionWaitInfo {
    /** 1-based position in the ticket queue. */
    position: number;
    holders: AdmissionEntry[];
}
export interface AdmissionAcquireOptions {
    /** Human-readable holder description shown in status listings. */
    label: string;
    /** Maximum wait before AdmissionTimeoutError (default 20 minutes). */
    timeoutMs?: number;
    /** Progress callback, invoked at most once per poll while waiting. */
    onWait?: (info: AdmissionWaitInfo) => void;
}
export interface AdmissionHandle {
    /** The held entry's filename (diagnostics). */
    entry: string;
    /** Milliseconds spent waiting in the queue. */
    waitedMs: number;
    /** Give the slot back. Safe to call more than once. */
    release: () => void;
}
export declare class AdmissionTimeoutError extends Error {
    readonly holders: AdmissionEntry[];
    constructor(resource: string, timeoutMs: number, holders: AdmissionEntry[]);
}
/** Is a PID alive on this machine? EPERM counts as alive; only ESRCH counts
 * as dead (fail toward respecting holders rather than stealing slots). */
export declare function pidAlive(pid: number): boolean;
/**
 * Join the FIFO queue for one resource and resolve once a slot is held.
 * Throws AdmissionTimeoutError (with the holders snapshot) when no slot
 * frees within the timeout — the caller decides whether that is fatal.
 */
export declare function acquireAdmission(config: AdmissionConfig, options: AdmissionAcquireOptions): Promise<AdmissionHandle>;
export interface AdmissionStatus {
    resource: string;
    capacity?: number;
    holders: AdmissionEntry[];
    waiters: AdmissionEntry[];
}
/** Snapshot the queue for one resource, pruning dead entries on the way. */
export declare function admissionStatus(config: Pick<AdmissionConfig, "dir" | "resource" | "ttlMs">): AdmissionStatus;
/**
 * Base directory for admission queue state. tmpdir clears on reboot, which
 * is correct — stale queue state must not outlive the boot. Override with
 * HARNERY_ADMISSION_DIR. Host CLIs and harn commands must share this helper
 * so they join the same machine-wide queues.
 */
export declare function admissionBaseDir(): string;
/** Resources present under an admission base directory. */
export declare function listAdmissionResources(dir: string): string[];
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