/**
 * UsageProxyServer — a loopback HTTP reverse proxy that sits between a
 * subprocess CLI and its configured LLM API base URL, purely to observe
 * token usage. It is NOT part of the request/response path functionally —
 * every request/response is relayed byte-for-byte unchanged; usage parsing
 * is a side-channel that never affects what the CLI sees.
 *
 * Why this exists: some subprocess-backed AgentRunners (CrushAgentRunner,
 * CopilotAgentRunner) drive CLIs whose non-interactive output doesn't
 * self-report token usage the way codex/kimi/qwen/grok's JSON event streams
 * do. Those CLIs DO support pointing at a custom OpenAI-compatible (or
 * Anthropic-compatible) base URL for BYOK/self-hosted use — this proxy uses
 * that existing knob rather than needing any CLI-side cooperation: the
 * runner starts a UsageProxyServer pointed at the real upstream, sets the
 * CLI's base-url env var to `proxy.url()`, and reads `proxy.totals()` after
 * each turn.
 *
 * Deliberately generic — not tied to crush/copilot specifically. Any future
 * subprocess runner whose CLI doesn't self-report usage can reuse this.
 */
export interface UsageTotals {
    inputTokens: number;
    outputTokens: number;
}
export type UsageApiStyle = 'openai' | 'anthropic';
export interface UsageProxyOptions {
    /** The real API base URL requests are relayed to, e.g. https://api.openai.com. */
    upstreamBaseUrl: string;
    /** Which response-body shape to look for usage in. */
    apiStyle: UsageApiStyle;
}
/** Parse a (possibly SSE) response body buffer for the usage it carries,
 *  merging per-field across every JSON document / SSE chunk found (not
 *  "last chunk wins" as a whole object — see mergeUsage). Handles both a
 *  single JSON document and `data: {...}\n\n` SSE framing. Exported for unit
 *  testing without spinning up a real server. */
export declare function parseUsageFromResponseBody(body: string, apiStyle: UsageApiStyle): UsageTotals | undefined;
export declare class UsageProxyServer {
    private opts;
    private server;
    private boundPort;
    private totalsAcc;
    private readonly upstream;
    constructor(opts: UsageProxyOptions);
    start(): Promise<void>;
    url(): string;
    totals(): UsageTotals;
    reset(): void;
    stop(): Promise<void>;
    private handle;
}
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