/**
 * Run `callback` inside a database transaction when the driver supports one,
 * or invoke it directly against the same `db` handle when it doesn't.
 *
 * Designed for Voyant services that share code paths between drivers with
 * different transaction semantics:
 *
 * - `postgres-js` (node) and `neon-serverless` (WebSocket): real transactions.
 *   The driver's `transaction(...)` method is used.
 * - `neon-http` (edge): the HTTP driver tagged with
 *   `VOYANT_DB_SUPPORTS_TRANSACTIONS = false` by `createDbClient`. The
 *   callback runs directly against `db`. Writes execute as independent
 *   statements — atomicity is lost on this driver. Callers that need true
 *   atomicity must select a transaction-capable adapter at startup.
 *
 * Nested calls are detected via a `WeakSet`: when invoked with a `tx` handle
 * that the helper already opened, the callback runs in-place against that
 * same handle (no second `BEGIN`).
 *
 * As a defense-in-depth, if a driver's `transaction()` throws with
 * "No transactions support …" *before* the callback executes (i.e. the
 * capability tag is missing on an HTTP-like driver), the helper retries by
 * invoking the callback directly. Errors raised *after* the callback starts
 * are not retried — they propagate.
 */
export declare function withOptionalTransaction<TDb, T>(db: TDb, callback: (tx: TDb) => Promise<T>): Promise<T>;
/** @internal — exposed for tests so they can assert WeakSet behavior */
export declare const __test__: {
    activeTransactionDbs: WeakSet<object>;
};
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