/**
 * persist-tool-calls — runtime glue between MCP server's in-memory
 * `sessionStats` and the on-disk `tool_calls` SessionDB table.
 *
 * Why this module exists
 * ──────────────────────
 * Commit 4742160 (May 2 16:58) added the SessionDB write path so the
 * statusline counters survived `npm update -g context-mode` and
 * `claude --continue`. Commit b392c2f (May 2 21:43) — the concurrency
 * refactor — silently dropped that wiring as collateral. Same-session
 * `/ctx-upgrade` flips the statusline back to `0 calls / $0.00`
 * because the new PID starts with an empty `sessionStats` and never
 * looks at the table the old PID was writing to.
 *
 * This module re-introduces the write path AND adds the read-side
 * restore that 4742160 never shipped — both pure helpers so the
 * server.ts wiring is a one-liner and the unit tests don't need to
 * boot the MCP server.
 */
/**
 * Shape returned by {@link restoreSessionStats}. Subset of the in-memory
 * `sessionStats` object the MCP server keeps — only the fields that can
 * be recovered from SessionDB.
 */
export interface RestoredSessionStats {
    /** Per-tool call counts. */
    calls: Record<string, number>;
    /** Per-tool returned bytes. */
    bytesReturned: Record<string, number>;
    /**
     * Epoch-ms for `session_meta.started_at` of the latest session, so the
     * statusline `uptime_ms` reflects the original session start instead of
     * resetting to `Date.now()` on every PID change.
     */
    sessionStart: number;
}
/**
 * Increment the persistent tool-call counter for `toolName` under whatever
 * session_id `session_meta` currently treats as the most recent. This is
 * called from {@link trackResponse} on every tool response and must be
 * cheap, non-throwing, and best-effort — a stats failure must never break
 * the MCP tool call.
 */
export declare function persistToolCallCounter(sessionDbPath: string, toolName: string, bytes: number): void;
/**
 * Read the latest session's tool-call totals back out of SessionDB so the
 * MCP server can hydrate its in-memory `sessionStats` on startup. Returns
 * `null` when the DB is missing or empty so the caller can keep the
 * default zero-state without branching twice.
 *
 * Used during MCP server boot (BEFORE the heartbeat fires) so the
 * statusline doesn't briefly flash `0 calls / $0.00` after upgrade.
 */
export declare function restoreSessionStats(sessionDbPath: string): RestoredSessionStats | null;