Function flatUsageToV3

src/node/utils/gatewayStreamNormalization.ts:39–67

(usage: Record<string, unknown>)

 * Convert flat (v2-style) usage to v3 nested format.
 */
export function flatUsageToV3(usage: Record<string, unknown>): V3Usage {
  const inputTokens = typeof usage.inputTokens === "number" ? usage.inputTokens : undefined;
  const outputTokens = typeof usage.outputTokens === "number" ? usage.outputTokens : undefined;
  const cachedInputTokens =
    typeof usage.cachedInputTokens === "number" ? usage.cachedInputTokens : undefined;
  const reasoningTokens =
    typeof usage.reasoningTokens === "number" ? usage.reasoningTokens : undefined;

  return {
    inputTokens: {
      total: inputTokens,
      noCache:
        inputTokens != null && cachedInputTokens != null
          ? inputTokens - cachedInputTokens
          : undefined,
      cacheRead: cachedInputTokens,
      cacheWrite: undefined,
    },
    outputTokens: {
      total: outputTokens,
      text:
        outputTokens != null && reasoningTokens != null
          ? outputTokens - reasoningTokens
          : undefined,
      reasoning: reasoningTokens,
    },
    raw: usage,
  };
}

/**
 * Normalize a finish-reason value to v3 format { unified, raw }.