/**
 * agentfootprint/stream — agent events → Server-Sent Events helpers.
 *
 * Pattern: Adapter (event stream → SSE wire format).
 * Role:    Outer ring. Subscribes to a `Runner`'s `EventDispatcher`
 *          and yields SSE-formatted strings. Drop into any HTTP
 *          framework that accepts an async iterable response body
 *          (Fetch Response, Express res.write, Hono streaming, etc.).
 * Emits:   N/A — observes only.
 */
import type { AgentfootprintEvent } from './events/registry.js';
import type { RunnerBase } from './core/RunnerBase.js';
/**
 * Hand the runner this iterable's caller before calling `runner.run()`.
 * Yields SSE-formatted strings until the run finishes (success, error,
 * or pause). Each event becomes:
 *
 *   event: <event name>
 *   data: <JSON payload>
 *   <blank line>
 *
 * @example
 *   // Express
 *   app.post('/agent', async (req, res) => {
 *     res.setHeader('content-type', 'text/event-stream');
 *     for await (const chunk of toSSE(agent)) {
 *       res.write(chunk);
 *     }
 *     res.end();
 *     // (in parallel: await agent.run(req.body))
 *   });
 */
export interface ToSSEOptions {
    /**
     * Filter predicate — return false to skip an event. Default: all events.
     * Common: `event => event.type.startsWith('agentfootprint.stream.')`
     * for a token-only feed.
     */
    readonly filter?: (event: AgentfootprintEvent) => boolean;
    /**
     * Output shape:
     *   - 'full' (default) — each event is JSON-serialized verbatim.
     *   - 'text' — only `agentfootprint.stream.token.content` is yielded,
     *     in plain text form (no event/data prefix). Useful for piping
     *     directly into a chat UI.
     */
    readonly format?: 'full' | 'text';
    /**
     * Custom event name extractor. By default `event.type` is used.
     * Useful for SSE consumers that want their own naming.
     */
    readonly eventName?: (event: AgentfootprintEvent) => string;
    /**
     * Heartbeat interval in ms. SSE connections through proxies/load
     * balancers often die after ~30s of silence; emit `: ping` comments
     * at this interval. Default 0 (disabled).
     */
    readonly heartbeatMs?: number;
}
/**
 * Subscribe to a runner's `EventDispatcher` and yield SSE-formatted
 * strings until the run completes.
 */
export declare function toSSE<TIn, TOut>(runner: RunnerBase<TIn, TOut>, options?: ToSSEOptions): AsyncIterable<string>;
/**
 * Class form for consumers who prefer `new SSEFormatter(runner).stream()`.
 * Identical behavior to `toSSE(runner)` — pick by preference.
 */
export declare class SSEFormatter<TIn = unknown, TOut = unknown> {
    private readonly runner;
    private readonly options;
    constructor(runner: RunnerBase<TIn, TOut>, options?: ToSSEOptions);
    /** Async iterable of SSE chunks. Consume with `for await`. */
    stream(): AsyncIterable<string>;
}
/**
 * Format any JSON-able payload as a single SSE event chunk.
 *
 * Useful for app-level events outside the runner's typed registry
 * (auth/error frames, app-state echoes). Most consumers won't need this.
 */
export declare function encodeSSE(eventName: string, payload: unknown): string;
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