OpenAI-compatible upstreams with explicit context cache (e.g. Alibaba Bailian)
report cache-write tokens as prompt_tokens_details.cache_creation_input_tokens.
The field was ignored, so cache-write tokens were billed at the plain input
price instead of the cache-creation price.
Parse it into InputTokenDetails.CacheCreationInputTokens and include it in
CacheCreationTokensTotal using max() with the existing cache-write fields, so
the same tokens are never counted twice.
yxkong
9823ebc7ea