Function buildThreadStyleHint

server/src/addie/thread-utils.ts:12–40

(
  messages: Array<{ user?: string; text?: string }>,
  botUserId: string
)

 * or when human messages are already long-form.
 */
export function buildThreadStyleHint(
  messages: Array<{ user?: string; text?: string }>,
  botUserId: string
): string | null {
  const humanMessages = messages
    .filter(msg => msg.user && msg.user !== botUserId && msg.text)
    .map(msg => msg.text!.trim())
    .filter(text => text.length > 0);

  if (humanMessages.length < 1) return null;

  // Measure median character length of human messages (true median for even counts)
  const lengths = humanMessages.map(t => t.length).sort((a, b) => a - b);
  const mid = Math.floor(lengths.length / 2);
  const median = lengths.length % 2 === 0
    ? (lengths[mid - 1] + lengths[mid]) / 2
    : lengths[mid];

  // If humans are writing short messages (under ~400 chars ≈ 3-4 sentences),
  // tell Addie to be concise. Over 400 is long-form enough that Addie's
  // normal style is fine.
  if (median > 400) return null;

  return [
    '## Response Style — Thread Calibration',
    `Humans in this thread are averaging ~${Math.round(median)}-character replies. Keep yours proportional.`,
    'Your baseline conciseness rules apply with extra force here — lead with the answer, not background.',
  ].join('\n');
}

/**
 * Check if a thread has multiple human participants.