/**
 * SSE wire-protocol decoder — a timer-free synchronous state machine,
 * mechanically extracted from `useSseChatAdapter`'s inline
 * `createDocStreamFn` parser. Byte-for-byte behavior parity with the
 * legacy parser is the contract (the golden fixtures in
 * `src/components/chat/hooks/__tests__/sse-stream-golden.test.ts` pin it
 * through the full hook path), including its quirks:
 *
 *   - A leading `\0`-terminated block that fails JSON.parse flips the
 *     stream into text mode and the WHOLE buffer (including the `\0`)
 *     is emitted as answer text (legacy no-frame stream fallback). This
 *     transition is marked `turn-start { implicit: true }`.
 *   - In text mode only `\x1F` is scanned — literal `\0` / `\x1E` bytes
 *     pass through into the answer; the FIRST literal `\x1F` flips into
 *     trailer mode and everything after is captured as the trailer
 *     (golden fixture (d) characterizes this mis-framing; the fix lives
 *     in `encode.ts`'s sentinel stripping, NOT here).
 *   - The `\x1E` sentinel and the `\x1F` trailer can arrive in ONE TCP
 *     chunk (fixed-answer responses) — the post-sentinel slice is
 *     re-scanned for the trailer sentinel.
 *   - Multi-byte UTF-8 across chunk boundaries survives via a single
 *     streaming TextDecoder (`{ stream: true }` on every push; no final
 *     flush — a trailing partial code point is dropped, as legacy did).
 *   - `end()` parses the accumulated trailer (malformed → silently
 *     ignored) and drops any un-terminated leading buffer, as legacy did.
 *     It is IDEMPOTENT (a deliberate deviation from legacy): repeat calls
 *     emit nothing, so an adapter that ends in both its completion path
 *     and its `finally` cannot double-count the usage frame.
 *
 * State flow: leading → (sentinel | parse-failure) → text → (\x1F) →
 * trailer-accumulate → end().
 *
 * Server-safe: no React, no timers, TextDecoder only.
 */
import type { ChatStreamEvent } from './events';
export interface SseFrameDecoder {
    /** Feed raw response bytes; returns the events they produced. */
    push(bytes: Uint8Array): ChatStreamEvent[];
    /**
     * Signal end-of-stream; parses the trailing usage frame if present.
     * IDEMPOTENT — every call after the first returns `[]`. Adapters
     * routinely call this from BOTH their completion path and a `finally`,
     * and a re-emitted `usage`/`stage:'end'` event would double-count token
     * usage (displayed cost doubles).
     */
    end(): ChatStreamEvent[];
}
export { escapeThinkingTags } from './leading-frames';
export declare function createSseFrameDecoder(): SseFrameDecoder;
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