import { type SessionTreeEntry } from "../harness/types.js";
/**
 * The SINGLE invariant gate for cross-backend session IMPORT (2c session-sync, service [266]②), as a STREAMING
 * online validator — feed entries oldest-first via {@link step}, then {@link finish}. The 2c NDJSON path imports
 * entries as a stream (keyset pages, no whole-array buffer), so the gate must be incremental; the array form
 * {@link validateEntriesForImport} is a thin wrapper over this (ONE source of truth — fork/tests keep the array
 * API). Fail-CLOSED: the first violation throws `SessionError("invalid_session")` and the caller writes nothing.
 *
 * Invariants enforced (the session-tree contract — see `storage-base.ts` getPathToRoot/appendEntry):
 *  1. Unique entry ids.
 *  2. Append order = parent-before-child: every non-null `parentId` MUST reference an entry stepped EARLIER. This
 *     is also the floor-truncation tripwire — if the export silently dropped pre-floor entries (the `getEntries()`
 *     tail-only bug), a tail entry's parent would be absent → throw, instead of a broken headless tree.
 *  3. Exactly one root (a single `parentId === null` entry) for a non-empty log — checked at `finish`.
 *  4. The derived leaf (after the last entry) resolves to a stepped entry — checked at `finish`.
 *
 * The validator NEVER rewrites entries — ids/parents/timestamps are preserved verbatim (the caller re-stamps only
 * the owner). It is single-use: `step` after `finish`, or a second `finish`, throws.
 */
export declare class StreamingImportValidator {
    private readonly seen;
    private rootCount;
    private runningLeaf;
    private done;
    /** Validate ONE entry, in oldest-first order. Throws `SessionError("invalid_session")` on the first violation
     *  (duplicate id, or a parent/structural reference not stepped before this entry). */
    step(entry: SessionTreeEntry): void;
    /** Finalize the stream: exactly one root (for a non-empty log) + the derived leaf resolves to a stepped entry.
     *  Returns the resolved leaf id (null for an empty session). Throws on violation; single-use. */
    finish(): {
        leafId: string | null;
    };
}
/**
 * Validate a verbatim session-entry log for cross-backend IMPORT (2c session-sync, service [266]②). The ARRAY
 * form of {@link StreamingImportValidator} (ONE source of truth — this just drives step()/finish() over the
 * array, kept for `fork`/tests that already hold the whole log). Fail-CLOSED: any violation throws
 * `SessionError("invalid_session")` and nothing is written.
 *
 * Returns the entries VERBATIM (validated, never rewritten — ids/parents/timestamps preserved so the imported
 * session is byte-identical to the source; only the owner is re-stamped by the caller, not here).
 */
export declare function validateEntriesForImport(entries: SessionTreeEntry[]): SessionTreeEntry[];
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