Function dedupeFinalAgainstStreamed

src/cli/modes/final-dedupe.ts:35–65

(rawFinal: string, streamedThisTurn: string)

const normCompare = (s: string) => cleanForDisplay(s).replace(/\s+/g, ' ').trim();

export function dedupeFinalAgainstStreamed(rawFinal: string, streamedThisTurn: string): FinalDedupeDecision {
  const finalContent = cleanForDisplay(rawFinal ?? '');
  const finalCmp = normCompare(rawFinal ?? '');
  const shownCmp = normCompare(streamedThisTurn ?? '');

  // (a) Nothing in final: just close the line if we streamed anything.
  if (!finalContent) {
    return { emit: '', closeLine: !!streamedThisTurn };
  }

  // (b) Nothing was streamed (some backends emit ONLY `final`): print final fresh.
  if (!shownCmp) {
    return { emit: finalContent, closeLine: true };
  }

  // (c) Already streamed (modulo whitespace): close the line, emit nothing.
  if (finalCmp === shownCmp) {
    return { emit: '', closeLine: true };
  }

  // (d) Streamed a prefix; print the remaining suffix.
  if (finalCmp.startsWith(shownCmp)) {
    const suffixLen = finalCmp.length - shownCmp.length;
    const remainder = finalContent.slice(finalContent.length - suffixLen);
    return { emit: remainder, closeLine: true };
  }

  // (e) Divergence (filter drift, sub-agent timing, etc). DO NOT re-print — this
  // was the duplication bug. Close the line and stop.
  return { emit: '', closeLine: true };
}

/**
 * Detect whether a newly-produced assistant message is redundant against the