Function prefixChars

src/llm/cache-layout.ts:53–59

(messages: Message[], n: number)

/** Approximate character count of the first `n` messages (proxy for cached tokens). */
export function prefixChars(messages: Message[], n: number): number {
  let chars = 0;
  for (let i = 0; i < Math.min(n, messages.length); i++) {
    chars += serializeMessage(messages[i]!).length;
  }
  return chars;
}

export interface CacheReuse {
  /** Leading messages shared with the previous turn. */