Function buildDroppedMessagesSummary

server/src/utils/token-limiter.ts:331–357

(droppedMessages: MessageTurn[])

 * @returns A concise summary string, or null if nothing worth summarizing
 */
export function buildDroppedMessagesSummary(droppedMessages: MessageTurn[]): string | null {
  if (droppedMessages.length < 5) return null;

  const toolsUsed = new Set<string>();
  let userMessageCount = 0;

  for (const msg of droppedMessages) {
    if (msg.toolCalls) {
      for (const tc of msg.toolCalls) {
        toolsUsed.add(tc.name);
      }
    }
    if (msg.role === 'user') userMessageCount++;
  }

  const parts: string[] = [];
  parts.push(`## Earlier Conversation Summary`);
  parts.push(`${droppedMessages.length} earlier messages (${userMessageCount} from the user) were dropped from context.`);

  if (toolsUsed.size > 0) {
    parts.push(`\n**Tools used earlier:** ${Array.from(toolsUsed).join(', ')}`);
  }

  parts.push(`\nIf the user references something from earlier that you don't recall, acknowledge the context was trimmed and offer to look it up or suggest starting a new thread.`);

  return parts.join('\n');
}

/**
 * Check if a request is likely to exceed context limits.