/**
 * The streaming-transcription (gpt-4o-transcribe SSE) reduction as PURE logic — extracted
 * from `stt.ts`'s `_readTranscriptionStream` so the fiddly bits (delta accumulation, the
 * done-vs-error precedence, the non-SSE JSON salvage, and the "empty ≠ error" / no-speech
 * decision) are unit-tested without a real network stream. `stt.ts` keeps only the
 * ReadableStream glue and drives these two functions.
 */
/** The running state as SSE events fold in. `acc` = concatenated deltas (the live partial);
 *  `final` = the `transcript.text.done` text (wins over `acc`); `streamErr` = a reason from
 *  an `error` event on an otherwise-200 stream. */
export interface TranscriptState {
    acc: string;
    final: string;
    streamErr: string;
}
export declare function initialTranscriptState(): TranscriptState;
/** The result of folding one payload: the new state plus any live partial to surface
 *  (`onResult(interim, false)`), or null when the event produced no partial. */
export interface TranscriptStep {
    state: TranscriptState;
    interim: string | null;
}
/**
 * Fold ONE SSE `data:` payload into the transcript state. Deltas accumulate and yield a
 * live partial; a done event sets the final; an `error` (or `*.error`) event records a
 * reason. Unknown/heartbeat payloads are inert. Pure — no side effects.
 */
export declare function reduceTranscriptPayload(state: TranscriptState, payload: string): TranscriptStep;
export type TranscriptOutcome = {
    kind: "result";
    text: string;
} | {
    kind: "no-speech";
} | {
    kind: "error";
    message: string;
};
/**
 * Decide the outcome of a completed stream. Precedence: any transcribed text wins (final
 * over accumulated deltas); else a mid-stream error surfaces; else it's a plain empty
 * result — silence / echo / the agent's own voice tail — reported as the soft `no-speech`
 * sentinel, NOT a scary error. `raw` is every decoded byte so a non-SSE `{ text }` JSON
 * body (proxy/model ignored `stream:true`) can still be salvaged. Pure.
 */
export declare function finalizeTranscript(state: TranscriptState, raw: string): TranscriptOutcome;
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