Function applyCacheControl

src/common/utils/ai/cacheStrategy.ts:92–116

(
  messages: ModelMessage[],
  modelString: string,
  cacheTtl?: AnthropicCacheTtl | null
)

 * We add cache_control to the last content part of the last message.
 */
export function applyCacheControl(
  messages: ModelMessage[],
  modelString: string,
  cacheTtl?: AnthropicCacheTtl | null
): ModelMessage[] {
  // Only apply cache control for Anthropic models
  if (!supportsAnthropicCache(modelString)) {
    return messages;
  }

  // Need at least 1 message to add a cache breakpoint
  if (messages.length < 1) {
    return messages;
  }

  // Add cache breakpoint at the last message
  const cacheIndex = messages.length - 1;

  return messages.map((msg, index) => {
    if (index === cacheIndex) {
      return addCacheControlToLastContentPart(msg, cacheTtl);
    }
    return msg;
  });
}

/**
 * Create a system message with cache control for Anthropic models.