Function openai_request 

pub fn openai_request(model: &str, usage: &Value) -> EconomicsRequest

Read an OpenAI usage object into the same shape. OpenAI’s input_tokens includes the cached part (input_tokens_details.cached_tokens), where Anthropic’s excludes it; the cached part is moved out so that the three input fields are disjoint for both. OpenAI bills no cache writes, so that field is zero, which is what it is.

use majordomus_cli::economics::usage::openai_request;
let r = openai_request("gpt-5", &serde_json::json!({
    "input_tokens": 1000, "input_tokens_details": {"cached_tokens": 800},
    "output_tokens": 50, "output_tokens_details": {"reasoning_tokens": 30}
}));
assert_eq!((r.input_tokens, r.cache_read_input_tokens, r.cache_creation_input_tokens), (200, 800, 0));
assert_eq!(r.thinking_tokens, Some(30));